Editorial Board - UPT · Editorial Board • Prof. Dr. Eng ... downlink DTX on the traffic channel...

Editorial Board

• Prof. Dr. Eng. Ioan NAFORNITA, Editor-in-chief

• Prof. Dr. Eng. Virgil TIPONUT • Prof. Dr. Eng. Alexandru ISAR • Prof. Dr. Eng. Dorina ISAR • Prof. Dr. Eng. Traian JURCA • Prof. Dr. Eng. Aldo DE SABATA • Prof. Dr. Eng. Florin ALEXA • Prof. Dr. Eng. Radu VASIU

• Lecturer Dr. Eng. Maria KOVACI, Scientific Secretary • Associate Prof. Dr. Eng. Corina NAFORNITA, Scientific

Secretary

Scientific Board

• Prof. Dr. Eng. Monica BORDA, Technical University of Cluj-Napoca, Romania

• Prof. Dr. Eng. Aldo DE SABATA, Politehnica University of Timisoara, Romania

• Prof. Dr. Eng. Karen EGUIAZARIAN, Tampere University of Technology, Institute of Signal Processing, Finland

• Prof. Dr. Eng. Liviu GORAS, Technical University Gheorghe Asachi, Iasi, Romania

• Prof. Dr. Eng. Alexandru ISAR, Politehnica University of Timisoara, Romania

• Prof. Dr. Eng. Michel JEZEQUEL, TELECOM Bretagne, Brest, France

• Prof. Dr. Eng. Traian JURCA, Politehnica University of Timisoara, Romania

• Prof. Dr. Eng. Ioan NAFORNITA, Politehnica University of Timisoara, Romania

• Prof. Dr. Eng. Mohamed NAJIM, ENSEIRB Bordeaux, France

• Prof. Dr. Eng. Emil PETRIU, SITE, University of Ottawa, Canada

• Prof. Dr. Eng. Andre QUINQUIS, Ministère de la Défense, Paris, France

• Prof. Dr. Eng. Maria Victoria RODELLAR BIARGE, Polytechnic University of Madrid, Spain

• Prof. Dr. Eng. Alexandru SERBANESCU, Technical Military Academy, Bucharest, Romania

• Prof. Dr. Eng. Virgil TIPONUT, Politehnica University of Timisoara, Romania

• Prof. Dr. Eng. Radu VASIU, Politehnica University of Timisoara, Romania

Advisory Board

• Prof. Dr. Eng. Ioan NAFORNITA, Politehnica University of Timisoara, Romania

• Prof. Dr. Eng. Alexandru ISAR, Politehnica University of Timisoara, Romania

• Prof. Dr. Eng. Mihaela LASCU, Politehnica University of Timisoara, Romania

• Prof. Dr. Eng. Florin ALEXA, Politehnica University of Timisoara, Romania

• Prof. Dr. Eng. Vasile GUI, Politehnica University of Timisoara, Romania

• Associate Prof. Dr. Eng. Eugen MARZA, Politehnica University of Timisoara, Romania

• Associate Prof. Dr. Eng. Dan ANDREICIUC, Politehnica University of Timisoara, Romania

• As. Dr. Ing. Andy VESA, Politehnica University of Timisoara, Romania

Buletinul Ştiinţific al Universităţii Politehnica Timişoara

TRANSACTIONS on ELECTRONICS and COMMUNICATIONS

Volume 59(73), Issue 1, 2014

CONTENTS

Cătălina-Marina Crina:

"Study on Coexistence between Long Term Evolution and Global System for Mobile

Communication"........................................................................................................................ 3

Razvan-Marius Popa:

"RAN Dimensioning for Wireless Networks"................................................................ 8

Ioana-Elena Puşcaş:

"Carrier Aggregation in LTE-Advanced"................................................................... 13

Victor Serban, Dan Andreiciuc, Aurel Filip:

"Telemetric Applications for the Automotive Industry using IQRF devices".............. 17

Cătălin Tudoran, Dan Andreiciuc, Aurel Filip:

"Multifunctional Siren for Emergency Services"........................................................ 21

Lupou Cristian Marius:

"Modeling in Matlab/Simulink the control of the vehicle’s air conditioner

compressor"............................................................................................................................. 26

Instructions for authors at the Scientific Bulletin of the Politehnica University of Timisoara -

Transactions on Electronics and Communications ................................................................ 32

1



Volume 59(73), Issue 1, 2014

Study on Coexistence between Long Term Evolution and

Global System for Mobile Communication

Cătălina-Marina Crina 1

1 Faculty of Electronics and Telecommunications, Communications Dept.

Bd. V. Parvan 2, 300223 Timisoara, Romania, e-mail [email protected]

Abstract — The massive development in mobile and

personal communications and the emergence of a

diversity of radio applications and services has led to an

explosion in the number of base station sites and mobile

stations and it is emphasizing the necessity for

improvements in the way that network operators co-

exist. Sustaining future growth is strongly dependent

upon the efficiency with which the radio spectrum is

used.

The main purpose of this paper is to evaluate the

possibility of co-existence between the GSM and LTE

systems using a software tool based upon Monte Carlo

technique, so called the Spectrum Engineering

Advanced Monte Carlo Analysis Tool (SEAMCAT),

identify the potential problems that might occur and

eventually draw conclusions and emphasize proper

solutions for the occurred problems.

Keywords — co-existence, interference, GSM, LTE

Monte Carlo, SEAMCAT

I. INTRODUCTION

Co-location or co-existence in near vicinity of Base

Stations may cause interference resulting in

performance degradation. In order to minimize this

performance degradation to an acceptable defined

level, certain decoupling requirements between the

systems have to be met. Actual decoupling

requirements can be estimated using comprehensive

interference analysis techniques.

The most critical co-existence situations occur when

the Down Link (DL) of any system (the interfering

one) is close to the Up Link (UL) of the concerned

victim system. In that case an interfering Base Station

(BS) is constantly disturbing a victim system BS

probably with high gain antennas on both sides.

Mobile Stations (MSs) may also be close to each

other and cause interference but this happens only

occasionally. BS and MS may also interferer each

other in special situations, caused by the near far

problems.

The assessment methodology for mobile inter-system

compatibility for site co-existence, site co-location

and sharing consists in the three main steps:

- Listing the possible incompatibility problems;

- Interference analysis;

- Required decoupling implementation solution.

The scope of this first step is to get a list of possible

reciprocal impact of the given systems in terms of

interferences. It is desirable (but often impossible) to

rank the interference sources upon their impact’s

severity.

The goal of the second step is to obtain the necessary

decoupling value between systems or the probability

of interference, depending on the calculation method

used.

There are two methods used for interference

assessment:

- deterministic calculation, which provides decoupling

requirement values which must be implemented

between the two systems;

- statistical method based on Monte Carlo simulations,

which provides the probability of interference

between the two systems.

The last step it consists of considering some case

specific solutions:

- improvement of cell planning such as: shrinking the

interfering cell, for example by lowering its output

power or tilting the antennas of its base station (if

feasible),

- increasing the stopband attenuation of the interfering

system’s transmit filter in the receive band of the

victim system,

- increasing the stopband attenuation of the interfering

system’s transmit filter in the transmit band of the co-

located system. This minimizes coupling between the

transmitters and the generated IM products in the

transmitters.

- increasing the receive filter’s stopband attenuation

for the interfering transmit frequencies, so that the

levels of these transmit signals are lowered below the

critical value,

- increasing decoupling between the two systems,

either the air decoupling or the decoupling provided

by diplexer. This also minimizes coupling between

the transmitters.

- other system specific measures such as activating

downlink DTX on the traffic channel or activating

downlink power control on traffic channels in the case

of the GSM system will be lower.

3

II. SPECTRUM ENGINEERING ADVANCED

MONTE CARLO ANALYSIS TOOL (SEAMCAT)

Using Monte Carlo method, in many applications the

physical process is directly simulated, hence there is

no need to write the differential equations describing

the behavior of the system, unlike the classical

analysis methods which use differential equations.The

only requirement is that the physical or mathematical

system to be described using probability and density

functions. The result is extracted by averaging a

number of simulations for a certain number of cases

[2].

The SEAMCAT simulator models a victim receiver

which operates in a medium with multiple sources of

interference. The interference sources may belong to

the same system as the victim receiver, or to another

system. The interference sources are randomly

distributed around the victim in a manner chosen by

the user. Usually a uniform distribution is chosen.

Only a specific number of sources of interference are

active at a time. In the figure 1, there is presented a

simulation scenario with a victim receiver and its

sources of interference.

The effect of each source of interference is accounted.

Some interference mechanisms are also included:

unwanted emissions, receiver blocking,

intermodulation products, co-channel and adjacent

channel interference [2]. A condition of interference occurrence is that the

victim receiver to have a carrier to interference ratio

(C/I) smaller than the minimum accepted value for a

correct decoding. In order to compute the carrier to

interference ratio of the victim, it is necessary to

establish both the desired received signal strength

(dRSS) and interfering received signal strength

(iRSS), [2].

On the left side of the diagram, the situation when no

interference occurs is presented, and on the right side

the opposite is presented. In the latter case, the

additional interference inside the wanted channel

Fig 1 A typical interference scenario for a Monte Carlo simulation,

[2].

Fig 2 Diagram of the received signals and C/I ratio [2].

band, will increase the noise level, and consequently

the C/I ratio of the victim system will decrease. The

new C/I ratio is defined by the difference in dB

between desired signal strength and the increased

noise level. This ratio has to be greater than the

minimum accepted in order to obtain a correct

decoding, [2].

The SEAMCAT tool verifies this condition and it

registers, for each case, whether interference occurred.

The Monte Carlo method considers independent

situations in time (or space). For each situation, a

scenario is built using a certain number of different

variables: the interfering sources position in relation

to the victim, the desired signal strength, the channels

used by the victim receiver and the interferer, and so

on. If a sufficient number of simulations are taken into

account, the probability of interference can be

computed with a higher precision, [2].

III. STUDY CASE – INTERFERENCE

ASSESSMENT BETWEEN LEGACY GSM AND

4G LTE IN 900 MHZ BAND

This study focuses on the main interference problems

which may appear with the introduction of new

generation LTE, inside the existing GSM 900MHz

frequency band in the case in which the GSM BS and

LTE BS are co-located. The study will consider both

the impact from GSM to LTE as well as from LTE to

GSM. The study assumes the case of GSM Operator

introducing LTE Base Stations on the already existing

GSM sites. The main objective is to evaluate the

impact of the interference, determine the interference

probability and identify the possible means to mitigate

the interference effects: minimum necessary guard

band, additional filtering required, and so on.

Channel arrangements in the 900 MHz GSM band:

• 2 x 25 MHz are allocated as Standard or

primary GSM 900 Band, P-GSM:

Uplink: 890 MHz to 915 MHz: mobile transmit, base

receive;

Downlink: 935 MHz to 960 MHz: base transmit,

mobile receive.

• Another 2 x 10 MHz are allocated as

Extended GSM 900 Band, E-GSM:

Uplink: 880 MHz to 915 MHz: mobile transmit, base

receive;

Downlink: 925 MHz to 960 MHz: base transmit,

mobile receive.

In total there are thus 2 x 35 MHz used by GSM900

(Standard GSM and Extended GSM).

Channel arrangements in the 900 MHz LTE band:

Uplink: 880MHz to 915 MHz: mobile transmit, base

receive;

Downlink: 925MHz to 960 MHz MHz: base transmit,

mobile receive

4

A. GSM IMPACT OVER LTE

1. BS-TO-MS SCENARIO

Since LTE will be introduced in the same GSM

900MHz band, the DL bands of the two systems will

be adjacent to each other, with a minimum guard band

which has to be determined for the two systems to co-

exist without impacting each other. Therefore, there is

a concern that potential interference from GSM BS

transmitters could interfere with LTE MS receivers.

The BS-to-MS interference might cause LTE system

DL performance degradation. In order to prevent the

affected LTE MS receiver desensitization and

blocking, a sufficient isolation between the interfering

and affected systems should be achieved.

Impact of mutual interference depends on the

interfering GSM BS transmitter emission mask and

affected LTE MS receiver characteristics that are

functions of the frequency separation between the two

systems (guard band).

The tables below show the results of the Monte Carlo

simulation for this scenario based on which the

recommended minimum guard band is 100 kHz in

order to have less than 5% interference probability.

Fig.3 Interfering Transmitter Emission Mask

(GSM BS)

Fig.4 Receiver Blocking Response (LTE MS)

Simulation Parameters

Simulation Results

Table 1 Unwanted Emissions caused Interference

Probability vs. Guard Band

Table 2 Receiver Blocking caused Interference


2. MS-TO-BS SCENARIO

Since LTE will be introduced in the same GSM

900MHz band, the UL bands of the two systems will

be adjacent to each other, with a minimum guard band

which has to be determined for the two systems to co-

exist without impacting each other. Therefore, there is

a concern that potential interference from GSM MS

transmitters could interfere with LTE BS receivers.

The MS-to-BS interference might cause LTE system

UL performance degradation. In order to prevent the

affected LTE BS receiver desensitization and



Impact of mutual interference depends on the

interfering GSM MS transmitter emission mask and

affected LTE BS receiver characteristics that are

functions of the frequency separation between the two

systems (guard band).

5


Simulation Results





The tables above show the results of the Monte Carlo

simulation for this scenario based on which the

recommended minimum guard band is 200 kHz, in

order to have less than 5% interference probability.

Based on the 3GPP standard values, the receiver

blocking interference probability is higher than 5%

even for higher guard bands. In real cases, the actual

performances of the LTE BS receiver are better than

standard requirements. If this is not the case,

additional filtering must be applied. Therefore, based

on simulations, the LTE BS blocking response must

be improved with 8 dB above 3GPP

requirements.

B. LTE IMPACT OVER GSM

1. BS-TO-MS SCENARIO

The BS-to-MS interference might cause GSM system

DL performance degradation. In order to prevent the

affected GSM MS receiver desensitization and


and affected systems should be achieved. Impact of

mutual interference depends on the interfering LTE

BS transmitter emission mask and affected GSM MS

receiver characteristics that are functions of the

frequency separation between the two systems (guard

band).


Simulation Results





The tables above show the results of the Monte Carlo

simulation for this scenario, based on which it results

that there are no interference problems because the

probability of interference caused by both unwanted

emissions and receiver blocking (which is actually

0%) is less than 5%. Therefore, in this case, there is

no need for additional filtering or for increasing the

guard band between the two systems.

2. MS-TO-BS SCENARIO

The MS-to-BS interference might cause GSM system

UL performance degradation. In order to prevent the

affected GSM BS receiver desensitization and



The tables below show the results of the Monte Carlo

simulation for this scenario, based on which it results

that there are no interference problems because the

probability of interference caused by both unwanted

emissions and receiver blocking (probability which is

actually 0%) is less than 5%.

6


Simulation Results





IV. CONCLUSIONS

Each one of the most representative selected scenarios

from study treated one mechanism of interference at a

time and the final result for the probability of

interference was not computed as the cumulative

effect from all the interference phenomena present

when the 2 systems, GSM and LTE, coexist. Only

after solving the problem caused by one interference

phenomenon, it can be noticed whether there are still

problems caused by other interference phenomena

which could be disturbing for the two systems.

From the simulation results, it can be concluded that

the GSM system has a greater negative impact upon

the LTE system rather than vice versa. However, this

impact in not crucial, because with a 200 kHz guard

band the probability of interference can be diminished

under the accepted value of 5%. The minimum

necessary guard band of 200 kHz implies that the

GSM operator has to release two carriers, solution

which does not affect too much the GSM network.

The simulation results in both studies show that the

most impacting scenario out of the four most

representative is the MS-to-BS one (the case in which

the GSM mobile station is the interferer for the LTE

base station). In this case, based on the 3GPP standard

values, the receiver blocking interference probability

is higher than 5% even for higher guard bands.

However, in real cases, the actual performances of the

LTE BS receiver are better than the standard

requirements. If this is not the case, additional

filtering must be applied. Therefore, based on

simulations, the LTE BS blocking response must be

improved with 8 dB above 3GPP requirements.

REFERENCES

[1] Inter-System-Compatibility – Theoretical Background, Dr. Ing.

T. Asztalos

[2] The Spectrum Engineering Advanced MONTE CARLO Analysis Tool (SEAMCAT) *, EMC 2002, Marc Le Dévendec and

Ari Réfik

[3] Inter-System-Compatibility – Challenges and Solutions, Dr. Ing. T. Asztalos

[4] 3GPP TS 45.005 V7.2.0 – technical specifications for the GSM

radio access network

[5] 3GPP TS 36.101 V8.5.1 –technical specifications for the LTE

radio access network (user equipment)

[6] CEPT/ERC/Report 68, Regensburg, May 2001: “Monte-Carlo Radio Simulation Methodology for the use in sharing and

compatibility studies between different radio services or systems”.

7



Volume 59(73), Issue 1, 2014

RAN Dimensioning for Wireless Networks

Razvan-Marius Popa Abstract – This paper paper will present the general

process of radio network design dimensioning and the

way the Vamos feature impacts dimensioning of the

Radio Access Network. The impact of VAMOS feature

over the Abis Interface dimensioning will be described.

Keywords: Abis, Vamos, capacity dimensioning

I. INTRODUCTION

The architecture of a 2G GSM network is presented in

Fig.1.

The Radio Access Network ( RAN ) is composed of

the BSC (Base Station Controller), the BTS (Base

Transceiver Station), the TC (Transcoder) and the

MFS (Multi-BSS Fast Packet Server) [1].

The BTS is a radio equipment which uses the radio

interface to receive and transmit information.A group

of BTS is handled by one BSC. The interface between

the BTS and the BSC is called Abis interface [2].

The BSC handles all associated radio functions like

RR management (for radio resource management and

mobility management during a call), power control,

handover, cell configuration data and channel

allocation. A group of BSC is served by a MSC

(Mobile Switching Center) and a SGSN (Serving

GPRS Service Node). Two interfaces leave the BSC:

Ater CS which is the interface conveying CS

information towards the transcoder (TC) and Ater PS

which is the interface conveying PS information

towards the MFS.

The transcoder can handle different types of codecs:

FR (Full Rate), EFR (Enhanced Full Rate), HR ( Half

Rate), AMR (Adaptive Multi Rate, transforms the

different coding into A law/miu law coding used in

the PCM format) and its major function is to translate

the 16 kbps channels called nibbles into 64 kbps

Fig. 1 GSM/GPRS/EDGE architecture[1]

channels called time slots (TS). The TC is linked to

the MSC by the A interface.

The MFS is in charge of performing the Packet

control function through the PCU (Packet Control

Unit).

The interface between the MSC and the SGSN is

called the Gb interface.

In this paper, the capacity dimensioning for the Abis

interface dimensioning for CS traffic coming from IP

sites will be detailed.

The capacity analysis is done independently from the

coverage analysis. Indeed the capacity of a cell, i.e.

the number of subscribers that can be handled,

depends only on:

- the user profile,

- the cell characteristics (i.e. how many TRXs

are available and in which configuration),

- the radio features that are available to boost

the capacity.

Also, it will be presented the impact of the VAMOS

feature over the dimensioning process of this

interface.

II. VAMOS FEATURE

VAMOS (Voice services over Adaptive Multi-user

channels on One Slot) is a 3GPP work item, the

objective of which is to specify a way in which two

users may be multiplexed on the same radio resource

simultaneously, i.e. using the same radio timeslot and

physical sub-channel.

In order to be able to use VAMOS, No new traffic

channels will be introduced to support VAMOS. The

existing FR and HR traffic channels will be used.

A. Downlink process

In the downlink direction, the BTS transmits

simultaneously to two MSs (Mobile Stations) on the

same frequency and TS, but using two different

training sequences, and a different modulation scheme

– alpha-Quadrature Phase Shift Keying (α -QPSK),

presented in “Fig. 2”[6], which allows two users to

share the same bandwidth, at the penalty of increased

interference.

In the diagram, two users are sharing the same

bandwidth, one using the first bit in each symbol, and

the other used the second. The value of α is chosen to

BTS

BTS

BTS

BSC MFS

SGSN

HLR

IP backbone

GGSN

PSTN

Internet/

Intranet

MSC/VLR

Mobile Radio

Mobile Core Circuit Switching

Mobile Core Packet Switching

TC

BTS

BTS

BTS

BSC MFS

SGSNSGSN

HLRHLR

IP backboneIP backbone

GGSNGGSN

PSTN

Internet/

Intranet

MSC/VLR

Mobile Radio

Mobile Core Circuit Switching

Mobile Core Packet Switching

TC

8

Fig. 2 α -QPSK diagram[7]

allow the power allocated to the two users to be

unequal.

α -QPSK can only be used when there is a 2-bit

symbol to transmit (one bit from each user).

Therefore, when DTX (Discontinuous Transmission)

is active, and there is a pause in speech from one user,

the other must switch back to using GMSK (Gaussian

Minimum Shift Keying, standard modulation scheme)

for the duration of the pause.

B. Uplink process

In the uplink direction, two MSs simultaneously

transmit their GMSK signal to the BTS on the same

TS and frequency. The BTS uses the different training

sequences to separate the signals (see Table 1).

Table 1 VAMOS Training sequences [6] Training

Sequence

Training sequence bits for the first set

0 (0,0,1,0,0,1,0,1,1,1,0,0,0,0,1,0,0,0,1,0,0,1,0,1,1,1)

1 (0,0,1,0,1,1,0,1,1,1,0,1,1,1,1,0,0,0,1,0,1,1,0,1,1,1)

2 (0,1,0,0,0,0,1,1,1,0,1,1,1,0,1,0,0,1,0,0,0,0,1,1,1,0)

3 (0,1,0,0,0,1,1,1,1,0,1,1,0,1,0,0,0,1,0,0,0,1,1,1,1,0)

4 (0,0,0,1,1,0,1,0,1,1,1,0,0,1,0,0,0,0,0,1,1,0,1,0,1,1)

5 (0,1,0,0,1,1,1,0,1,0,1,1,0,0,0,0,0,1,0,0,1,1,1,0,1,0)

6 (1,0,1,0,0,1,1,1,1,1,0,1,1,0,0,0,1,0,1,0,0,1,1,1,1,1)

7 (1,1,1,0,1,1,1,1,0,0,0,1,0,0,1,0,1,1,1,0,1,1,1,1,0,0)

Training sequence bits for the second set

0 (0,1,1,0,0,0,1,0,0,0,1,0,0,1,0,0,1,1,1,1,0,1,0,1,1,1)

1 (0,1,0,1,1,1,1,0,1,0,0,1,1,0,1,1,1,0,1,1,1,0,0,0,0,1)

2 (0,1,0,0,0,0,0,1,0,1,1,0,0,0,1,1,1,0,1,1,1,0,1,1,0,0)

3 (0,0,1,0,1,1,0,1,1,1,0,1,1,1,0,0,1,1,1,1,0,1,0,0,0,0)

4 (0,1,1,1,0,1,0,0,1,1,1,1,0,1,0,0,1,1,1,0,1,1,1,1,1,0)

5 (0,1,0,0,0,0,0,1,0,0,1,1,0,1,0,1,0,0,1,1,1,1,0,0,1,1)

6 (0,0,0,1,0,0,0,0,1,1,0,1,0,0,0,0,1,1,0,1,1,1,0,1,0,1)

7 (0,1,0,0,0,1,0,1,1,1,0,0,1,1,1,1,1,1,0,0,1,0,1,0,0,1)

III. BSS IP ARHITECTURES

The Abis interface conveys the CS traffic between the

BTS and the BSC. The transport mode that can be

used on this interface can be TDM or IP. Since the

VAMOS feature is available only with IP in the BSS,

only the 2 available IP architectures will be presented:

A. IP over Ethernet

Fig. 3 IPoEth architecture

The first architecture is called IP over Ethernet

(IPoEth) and offers a full IP over Ethernet solution.

The CS user plane flow that goes directly to the TC

and it is called the Abis CS flow. When dimensioning

the IP over Ethernet network the peak and the average

throughputs need to be computed.

B. IP over E1

Fig. 4 IPoE1 architecture

The second IP architecture is called IP over E1

(IPoE1). This architecture keeps the existing E1 links

on the Abis interface, and then introduces IP transport

within these links, using the Point-to-Point Protocol

(PPP) or the Multi Link PPP (ML-PPP) in the case of

two or more E1 links. The difference compared to the

previous architecture is the fact that the whole traffic

is routed towards the BSC. Beyond the BSC, the

logical flows are conveyed through the IP backbone.

The Ater CS flow is going form the BSC to the TC.

So, compared to the previous architecture, a new flow

appears.

IV. ABIS INTERFACE DIMENSIONING FOR CS

A. Information packing and headers

The CS traffic is carried on TRAU (Transcoder and

Rate Adaptation Unit) frames. One TRAU frame lasts

20 ms and is carried on the TDMA frames. The 20 ms

correspond to the duration of 4 TDMA frames.

Looking at the “Fig. 5”, it can be observed that a first

part of the TRAU frame is carried on TS1 of the 1st

Fig. 5 Multiplexing of TRAUP frames on IP packets

9

TDMA frame, the second part is carried also on TS1

of the second TDMA frame, the 3rd part of the TRAU

frame is carried on TS1 of the 3rd TDMA frame and

the last part of the TRAU frame is carried on TS1 of

the 4th TDMA frame. Finally, after 4 TDMA frames,

the whole TRAU frame is sent. The red TS

correspond to the 1st TRAU frame. A second TRAU

frame is carried on TS2 of each TDMA frame during

4 TD MA frames lasting 20 ms in the same way as the

1st one. In the figure above, the blue TS correspond to

the 2nd TRAU frame [7].

After the full TRAU frame is sent, it is put in an IP

packet. The IP packet contains only full TRAU

frames, in consequence only after the last part of the

TRAU frame has been received, it can be put in an IP

packet. Several TRAU frames are multiplexed over IP

packets. The TRAUP packets are composed out of

some useful information represented in the dark green

color and some headers represented in light green.

Inside the IP packet there are headers from each

protocol used: MUXTRAUP, UDP, IP and depending

on the architecture IPoEth or IPoE1 the Ethernet or

the [ML] PPP header is added.

When putting TRAUP frames into IP packets one of

the two limitations may occur before sending the IP

packet:

a) Maximum size supported by the IP packet

(MUXTRAUP_SIZE), which does not

include the Ethernet or the [ML] PPP header.

The typical size is 800 bytes [3].

b) Maximum time elapsed since beginning the

sending of TRAUP packets reflected in the

timer MAX_HOLD_MUXTRAUP. The

default value is 2 ms.

The IP packet is sent when encountering the first

limitation. If the delayed timer

MAX_HOLD_MUXTRAUP has expired then the

packet is sent even if it is not full, i.e. even if it didn’t

reach the maximum 800 bytes size.

These limitations will be carefully considered when

computing the number of IP packets needed to send

some information and the overheads associated to it.

The headers for IPoEth and IPoE1 are presented in

Table 2.

Table 2 IPoEth and IPoE1 headers [7]

PPP (Point-to-Point Protocol) HDLC is used in case

of a single E1 link on the Abis. In case of 2 or more

E1 links, [ML] PPP is used (Multi-link Point-to-Point

Protocol).

The TRAUP frame is built up as follows:

UL: 2 bytes (UL Address) + 1 byte (control) + N

bytes (payload, incl. 2 or 4 bits for the payload type)

[3]

DL: 2 bytes (Call-ID + DL Address) + 1 byte

(control) + N bytes (payload, incl. 2 or 4 bits for the

payload type) [3]

The payload depends on the codec. The values

considered in Alcatel-Lucent’s method[3] are:

a) TRAUP_Size FR = 244 bits

b) TRAUP_Size HR = 148 bits

B. IP Packets:

Headers associated to IP packets lead to overheads

and the number of IP headers depends on the number

of IP packets. In order to compute the overheads on

Abis introduced by all the protocol headers, the

number of IP packets need to be computed first.

The computation of the number of IP packets used to

carry CS traffic over 20 ms (TRAU frame duration)

depends then on the number of TRAU frames created

during T_MAX_HOLD_MUXTRAUP and the

maximum size of the IP packet.

The size of the information that can be put in an IP

packet during the timer

T_MAX_HOLD_MUXTRAUP is computed. This

will depend on the TRXs and the TS used for CS.

Information = N8 × TRAU× RoundDown T !"#$%&'()*&+timeslot/012345 6 (1)

With VAMOS, it is possible to carry 2 calls (i.e. 2

TRAU frames over 20ms) simultaneously on each

radio TS.

The number of calls will be doubled for a proportion

πVAMOS of the TS, and will remain as previously for a

proportion (1- πVAMOS).

Consequently, the number of TRAU frames, and also

the number of TRAUP bits, will change by

introducing a factor of:

(1- πVAMOS) + 2 × πVAMOS = [1 + πVAMOS] (2)

After the introduction of (2) in (1) we get:

:;<=>?@AB=;CDEF =GHIJ × (1 +LMNOPQ) × RSTUVWDXC ×roundDown YZ%*'!"#$%&'()*&+3[ \43]^_`abcd e(3)

The number of IP packets is the total information to

be carried divided by the maximum size of the blocks

used to carry that information. Or conversely, the

number of TS needed to be carried divided by the

number of TS corresponding to the Max_size. The

active TS, NCS to be sent are multiplied with the

VAMOS factor to account for the fact that with

VAMOS 2 calls are simultaneously carried on one TS.

IPoEth IPoE1

Header Size ( bytes )

Ethernet 38 -

[ML]PPP

HDLC

- 9 [13]

UDP/IP 28

MUXTRAUP 2

TRAUP Number_of_TRAUP_Frames *

TRAUP_Size

Total

(without

TRAUP)

68 39 [43]

10

Fig. 6 Number of IP Packets per 20 miliseconds

Fig. 7 VAMOS impact on Peak Throughput

The denominator represents the number of TS

corresponding to Max_size which is the maximum

size divided by the size of the TRAUP frame which

takes into account the HRCR and the different values

of the TRAUP frame for HR and FR. ghijklmnoHI= S=p;qUr gtQ × (1 +LMNOPQ)

S=p;qu=v; wTxQDEFyzSS × 2 × RSTUVQDEF~ +(1 − zSS) × RSTUQDEF6(4)

C. Peak Throughput

The CS peak throughput is the throughput reached

when all the CS radio TS are simultaneously active.

By multiplying the number of active TS used for CS

by the bitrate per TS, the figure obtained, Fig.7, is the

useful throughput for NCS TS. V@Rℎ>=pℎrpAtQ= gtQ× BAS@A × (1 − zSS) + 2× BAS@A × zSS× (1 +LMNOPQ)(5)

As it can be observed in the above chart the Peak

throughput increases rapidly with the VAMOS

penetration. For instance for a number of 180 active

TS the throughput achieved with VAMOS 100% is

more than double the one achieved without VAMOS.

D. Peak Overheads

The total CS overheads are computed by including

also the TRAUP headers (1 TRAUP header per active

call over 20 ms).The number of TRAUP frames in the

20ms period is doubled for the πPAIRED calls. >ℎ@qtQ = ghijklmnoHI × :VFFC +gtQ ×RSTUVFFC × (1 + LMNOPQ) × (1 + zSS)/20?(6)

Although the Peak overheads increase with the

VAMOS penetration (Fig. 8) - which is normal

Fig. 8 VAMOS influence on the Peak OH

Fig. 9 VAMOS influence on OH ratio

Fig. 10 VAMOS impact on Useful Average Throughput

considering that the more packets are sent during the

reference period, the more headers are sent, thus the

larger quantity of OH – the overhead ratio (Fig. 9)

computed as the overhead information reported to the

useful information tends to the same constant value no

matter the VAMOS penetration for large

configurations (more than 50 NCS).

E. Average Throughput

The Average throughput, Fig.10, is composed out of

the useful average throughput and the average

overheads. The average OH will be discussed in the

next paragraph. The useful average throughput is

impacted by the same [1 + πVAMOS] factor: U<pT>@Rℎ>=pℎrpA= BAS@A × (1 − zSS) + 2× BAS@A × zSS × (1

+ LMNOPQ) × (_)(7)F

Where ρcell represents the traffic intensity in the cell.

In the above charts, apart of the fact that the

throughput increases with the VAMOS penetration, it

is also that no major gain is brought by passing from

50% HRCR to 100% HRCR for the same penetration

of VAMOS (see light blue and dark blue lines), on the

other hand a significant improvement can be observed

when passing from VAMOS 0% to VAMOS 100%

for the same HRCR (see dark blue and pink lines).

Peak Overheads (kbps) IPoEth

0

200

400

600

800

1000

1200

1400

0 20 40 60 80 100 120 140 160 180

N_CS

IPo

Eth

Pe

ak

Overh

ead

s (

kb

ps)

(DT

X =

60%

, H

RC

R =

10

0%

)

VAMOS_0%

VAMOS_50%

VAMOS_100%


0

200

400

600

800

1000

1200

1400

0 20 40 60


0

200

400

600

800

1000

1200

1400

0 20 40 60 80 100 120 140 160 180

N_CS

IPo

Eth

Pe

ak

Overh

ead

s (

kb

ps)

(DT

X =

60%

, H

RC

R =

10

0%

)

VAMOS_0%

VAMOS_50%

VAMOS_100%

11

Furthermore, the impact on the average throughput is

a major one when considering both HRCR and

VAMOS 100%, the average throughput more than

doubles for the same number of NCS.

F. Average Overhead

For the average overhead computation, all the states in

which the system can be must be considered. The

following states and their corresponding probabilities

of occurrence must be considered: the state with 1

active call, with 2 active calls and so on up to NCS

active calls. For one specific state the computation is

the same as for the peak, but with NCS replaced by k

which can take values from 1 to NCS. The VAMOS

impact relies as for the peak in the number of IP

packets and the number of TRAUP frames transferred

during the 20ms period: >ℎ@qtQ() = ghijklmnoHI × :VFFC + × RSTUVFFC × (1 + LMNOPQ) × (1+ zSS)/20?(8)

An average overhead will be computed taking into

account all the overheads introduced by different

states and their probability of occurrence: T>@>ℎ@qtQ

=r()× >ℎ@qtQ()(9)

Since the average overhead computation is practically

based on the same formula as the peak overhead, the

same observations are valid, the overhead increases

with the NCS and also with the VAMOS proportion.

For the overhead ratio, although the overheads start

from a higher value for larger VAMOS penetration,

Fig. 11 VAMOS impact on Average Overhead

Fig. 12 VAMOS impact on Average Overhead Ratio

after a given configuration in terms of number of

active TS, the overhead ratio tends toward a constant

value no matter the VAMOS penetration.

V. CONCLUSIONS

VAMOS uses a new modulation, α-QPSK to allow

two voice calls to be transmitted simultaneously over

the same timeslot. This feature impacts the network

design dimensioning process in two of its branches:

Capacity and Abis dimensioning. A new parameter is

needed to account for the VAMOS impact, πVAMOS.

Abis Dimensioning requires changes to Number of IP

Packets computation, peak and average Overhead and

Throughput formulas to account for additional traffic

present. The influence relies on the [1 + πVAMOS]

factor which is explained by the fact that with

VAMOS, it is possible to carry 2 calls (i.e. 2 TRAU

frames over 20ms) simultaneously on each radio TS,

thus the number of calls will be doubled for a

proportion πVAMOS of the TS, and will remain as

previously for a proportion (1- πVAMOS).

Consequently, the number of TRAU frames in all the

previous formulas used in Abis dimensioning will

change by introducing a factor of (1- πVAMOS) + 2 *

πVAMOS = [1 + πVAMOS].

The effects of an increased VAMOS penetration on

Abis dimensioning are the increase of number of IP

packets that can be sent during the 20 ms period, the

increase of average and peak throughput but also the

increase of generated overheads which come from the

packet headers. All in all VAMOS brings a major

improvement since the throughput is larger and the

overall overhead ratio tends toward a constant figure

no matter the VAMOS penetration for a given number

of resources larger than 50 NCS.

REFERENCES

[1] M. Saily, G. Sebire, Dr. E. Riddington, “GSM/EDGE Evolution

and Performance”, John Wiley & Sons Ltd, 2011.

[2] M. Staiak, M. Glabowski, A.Wisniewski, P. Zwierzykowski,

“Modeling and Dimensioning of Mobile Networks – From GSM to

LTE”, John Wiley & Sons Ltd, 2011.

[3] “Capacity Analysis”, Alcatel-Lucent.

[4] E. Marza, “Comunicatii Mobile, note de curs”, Facultatea de Electronică şi Telecomunicaţii Timişoara, 2012.

[5] “Evolution of GSM voice”,

http://www.ericsson.com/res/docs/whitepapers/100716_VAMOS_a

pproved.pdf

[6] “Communication of redundant SACCH Slots during

discontinuous transmission mode for VAMOS”, http://www.faqs.org/patents/app/20110205947

[7] “GSM/GPRS/EDGE Radio Network design process for Alcatel-

Lucent BSS Release LR13”, Alcatel-Lucent.

12



Volume 59(73), Issue 1, 2014

Carrier Aggregation in LTE-Advanced

Ioana-Elena Puşcaş 1

1 Faculty of Electronics and Telecommunications, Communications Dept.


Abstract – LTE-Advanced extends the capabilities

originally defined in LTE within the 3GPP and Carrier

Aggregation (CA) is the most significant, although

complex, improvement provided by LTE-Advanced.

Bandwidths from various portion of spectrum are

logically concatenated or “aggregated” resulting in a

virtual block of a much larger band, enabling increased

data throughput. The aim of this paper is to present an

introduction of CA in LTE-Advanced system, including

current 3GPP status on CA technology, configuration

and deployment scenarios and Physical, MAC and RRC

(Radio Resource Control) Layers aspects of Carrier

Aggregation.

Keywords: LTE-Advanced, Carrier Aggregation, 3GPP

I. INTRODUCTION

LTE-Advanced (LTE-A) aims to support peak

data rates of 1 Gbps in the downlink and 500 Mbps in

uplink. [1] In order to fulfill such requirements, a

transmission bandwidth of up to 100 MHz is required.

However, since current versions of broadband

wireless systems make use of channel bandwidths of

up to 20 MHz the availability of such large portions of

contiguous spectrum is rare in practice. Therefore a

different spectrum management scheme is necessary

for next generation wireless systems in order to

achieve the required bandwidth.

LTE-Advanced uses carrier aggregation to form a

larger bandwidth by collection of multiple existing

carriers in order to meet the needs of higher

bandwidths. In Fig. 1 is presented CA concept in

LTE-Advanced system. [2] Each aggregated carrier is

referred to as a component carrier (CC). Release 8

LTE carriers have a maximum bandwidth of 20 MHz;

therefore LTE-Advanced can support aggregation of

up to five 20 MHz carriers.

Upon the demand on higher bandwidth and

higher data rate applications and based on the

expected growth of broadband users, LTE-Advanced

system introduced CA technology to overcome the

spectrum poverty and fragmentation problem,

irrespective of the peak data rate. [3]

Carrier aggregation in LTE-Advanced is designed

to support aggregation of a variety of different

arrangements of component carriers including carriers

of the same or different bandwidths, adjacent or non-

adjacent component carriers in the same frequency

band or in different frequency bands. [4] There are

three types of CA, depending on CC combinations:

a) Intra-band Contiguous CA

b) Inter-band Non-contiguous CA

c) Intra-band Non-contiguous CA

The component carrier can have a bandwidth of

1.4, 3, 5, 10, 15 or 20 MHz and, as mentioned earlier,

a maximum number of five component carriers can be

aggregated allowing for an overall transmission

bandwidth of up to 100 MHz. CA can be used for

both FDD and TDD. In FDD the number of

aggregated carriers can be different in downlink (DL)

and uplink (UL); however the number of UL

component carriers is always equal or lower that the

number of DL component carriers. The individual CC

can also be of different bandwidths. For TDD the

number of CCs as well as the bandwidths of each CC

will normally be the same for DL and UL.

Figure 2. Types of Carrier Aggregation

Figure 1. Concept of Carrier Aggregation

13

II. CONFIGURATION SCENARIOS OF CARRIER

AGGREGATION

3GPP has defined a range of carrier aggregation

scenarios for LTE-Advanced. Further we will present

five potential deployment CA scenarios considering

F1 and F2 two carriers to be aggregated (F2>F1). For

the DL all scenarios could be supported and for the

UL only scenarios #1, #2 and #3. [5]

A first possible CA configuration scenario is

described by following characteristics: F1 and F2

cells are co-located and overlaid, providing nearly the

same coverage. For this scenario both carriers are

generally within the same band (e.g. 2 GHz, 800

MHz, etc.) and it is expected that aggregation is

possible between overlaid F1 and F2 cells. [5]

The second possible scenario is similar with the

first one, F1 and F2 are co-located and overlaid, but

F2 has smaller coverage due to larger path loss. Only

F1 is used to provide full coverage and F2 is used to

further improve the data transfer rate for some

specific area. For this scenario the two carriers are

configured in different frequency bands (e.g. F1 =

800 MHz, 2 GHz and F2 = 3.5 GHz, etc.) and it

is expected that aggregation is possible between

overlaid F1 and F2 cells. [5]

In the third configuration scenario F1 and F2

cells are co-located, but F2 antennas are directed to

the cell boundaries of F1 to increase the throughput at

cell edge. In this configuration is also more likely that

the two carriers are configured in different frequency

bands. It is expected that F1 and F2 cells of the same

base station can be aggregated where coverage

overlap for higher data transmission rate. [5]

The fourth CA deployment scenario is shown in

Figure 5. F1 provides macro coverage and F2 is

deployed with Remote Radio Heads (RRHs) to

provide throughput at hot spots. Possible

configuration is to assign two carriers on different

frequency bands. It is expected that F2 cells can be

aggregated with the underlying F1 macro cells. [5]

The fifth configuration scenario is similar to

scenario #2, but frequency selective repeaters are

deployed so that coverage is extended for one of the

carrier frequencies. It is expected that F1 and F2 cells

of the same base station can be aggregated where

coverage overlap. [5]

III. PROTOCOL IMPACT OF CARRIER

AGGREGATION

Backward compatibility is essential for smooth

system migration and maximal reuse of the previous

design. The design of 3GPP LTE-Advanced carrier

aggregation considers backward compatibility; thus

CA feature enables concurrent data transmission on

multiple CCs, with procedures largely inherited from

LTE Release 8/9.

The services offered by higher layers are filled by

user plane and control plane function. The user plane

is responsible for data communicational, and the

control plane is responsible for maintaining the

connection between the network and the user

equipment (UE). The LTE R8/9 control plane stack

also applies to LTE-A CA. From the higher layer

viewpoint, each CC appears as a single cell with its

own cell identifier: each UE connects to one Primary

Serving Cell (Pcell) which is initially configured

during establishment and provides all necessary

control information and functions; besides, up to four

Secondary Serving Cells (SCells) may be configured

after connection establishment only to provide

additional radio resources. [6]

Figure 3. CA deployment scenario #1





14

In the user plane protocol design for LTE-A, the

use of carrier aggregation is not visible above the

Medium Access Control (MAC) layer.

A. Physical Layer Aspects

The exchanging of the data and control

information between network and UE is the

responsibility of the physical layer. LTE-A CA

inherits the legacy LTE data transmission per CC,

including multiple access scheme, modulation and

channel coding (MCS). Additional UE functionalities

are supported in LTE-A, but the main challenge in the

design of CA was improving the DL and UL control

signaling to efficiently support data transmission. [7]

For downlink, at the start of each subframe of

each DL CC a control region is available for Physical

Control Format Indicator Channel (PCFICH –

transmits a control format indicator, CIF, field which

specifies the number of OFDMA symbols carrying

control information), Physical Downlink Control

Channel (PDCCH – supports information on resource

allocation, MCC, HARQ etc.) and Physical HARQ

Indicator Channel (PHICH – used for transmission of

the HARQ ACK/NACKs).

A key characteristic of CA is a cross-carrier-

scheduling. This enables a PDCCH on a CC to be

configured in order to scheduled PDSCH and PUSCH

transmissions on other CCs by means of new 3-bits

carrier indicator field (CIF) inserted at the beginning

of the PDCCH. The main motivation for cross-carrier

scheduling is to support Inter-Cell Interference

Coordination (ICIC) for PDCCH in heterogeneous

networks, so CA can reduce or even eliminate ICIC

on PDCCH of the CC which can schedule data

resources on others CCs and improve data rates. [8]

The normal scheduling operation where the

PDCCH with the corresponding PDSCH or PUSCH

are transmitted on the same cell is also maintained for

backward compatibility. It is possible to transmit

PDCCH scheduling a PDSCH on the same carrier

frequency and PDCCH scheduling a PUSCH on a

linked UL carrier frequency where the linkage of the

DL and UL carriers in conveyed as system

information.

Based on the decoded CFI value, UE derives the

starting point of PDSCH transmission. In the case of

PDSCH non-cross-carrier scheduled by PDCCH on

the same component carrier, UE is required to decode

the PCFICH in order to determine the starting OFDM

symbol used for PDSCH. For PDSCH cross-carrier

scheduled by PDCCH on another carrier, the starting

OFDM symbol for PDSCH transmission is configured

by the network though higher layers, and the UE is

not required to decode the PCFICH on the CC of the

PDSCH transmission. [9]

The design of the PHICH in LTE-Advanced CA

follows the design of LTE Release 8.

Uplink control signaling, UCI, includes HARQ

ACK/NACK signaling corresponding to potentially

multiple PDSCHs, scheduling requests and Channel

State Information (CSI). As in LTE Release 8/9, UCI

can be transmitted on a physical uplink control

channel (PUCCH) if there is no transmission on a

PUSCH in a subframe, and transmitted on PUSCH

otherwise. LTE-Advanced further supports, by

network configuration, simultaneous transmission of

PUCCH and PUSCH in a sub frame. This allows the

base station to flexibly control the performance of the

PUCCH and PUSCH independently and to avoid the

UCI overhead on the PUSCH by utilizing existing

PUCCH resources. The PUCCH can only be

transmitted on the PCell, since it typically has more

reliable link quality and coverage relative to the

SCells. When applicable, UCI is always transmitted

on a single PUSCH. [9]

LTE Release 8/9 PUCCH known as format 1b

was only defined to support up to 4 bits (2 bits in FFD

and 4 bits in TDD), so HARQ feedback can only be

transmitted only for two CCs. The PUCCH format 3

was introduced in LTE-A to support HARQ feedback

for a UE configured with downlink CA. This enables

a full range of ACK/NACK bits to be transmitted (up

to 10 Bits for FDD and up to 20 bits in TDD). [7]

Channel state information (CSI) feedback assist

the network to achieve PDSCH scheduling, including

resource selection, MCS selection, transmission rack

indicator and precoding matrix indicator. In order to

handle the different channel conditions and interface

level among different CCs, the CSI is configured for

each CC. In LTE-Advanced, both periodic and

aperiodic CSI feedbacks are supported. LTE-

Advanced supports aperiodic CSI feedback for a

single or multiple CCs in a subframe in order to

balance the CSI accuracy and feedback overhead. [9]

In CA, periodic CSI is reported for only one CC

in a subframe. Different offsets and periodicities

should be configured to minimize collisions between

CSI reports of different CCs in a subframe. In case the

collisions involve the multiple periodic CSI reports,

the priority is according to defined prioritization rules.

Aperiodic CSI feedback is transmitted on PUSCH and

carries more CSI than periodic CSI feedback. In the

case of a collision between periodic and aperiodic CSI

for downlink CCs, the periodic CSI is dropped. [7]

B. MAC Layer Aspects

From the MAC perspective the CA simply

provides additional conduits, thus the MAC layer

Figure 8. Cross-carrier scheduling

15

plays the role of a multiplexing entity for the

aggregated components carriers. [10] There is one

MAC entity per user, which controls the multiplexing

of data from all logical channels to the user, and

further controls how this data is transmitted on the

available CCs. Each MAC entity will provide to his

corresponding CC its own Physical Layer entity,

providing resource mapping, data modulation, HARQ

and channel coding.

The interface between the MAC layer and the

physical layer, which are referred to as transport

channels, is also separate for each component carrier.

[8]

V. CONCLUSIONS

This article provides an overview of CA in 3GPP

LTE-Advanced. CA for LTE-Advanced is fully

backward compatible, which essentially means that

legacy LTE Release 8/9 terminals and LTE-Advanced

terminals can co-exist maintaining the advantages of

legacy technologies and reducing the cost per bit and

saving energy.

Carrier Aggregation has much more to offer and

it continues to be a significant area of work for 3GPP,

equipment manufacturers and network operators and

will continue to be one of the most important

techniques in the next generation telecommunication

system. Over the coming years there will be a

number of important developments, including, for

example: increasing the number of CCs and the total

bandwidth supported in both the DL and the UL;

supporting a greater number of frequency bands and

combinations of frequency bands; supporting CA

between licensed and unlicensed spectrum. [13]

REFERENCES

[1] 3GPP Technical Report 36.913, “Requirements for further

advancements for Evolved Universal Terrestrial Radio Access (E-

UTRA) (LTE-Advanced)”, www.3gpp.org.

[2] E. Seidel, “LTE-A Carrier Aggregation Enhancements in

Release 11”, NOMOR Research GmbH, Munich, Germany, 2012.

[3] A. Z. Yonis, M. F. L. Abdullah, M. F. Ghanim, “Effective Carrier Aggregation on the LTE-Advanced Systems”, International

Journal of Advanced Science and Technology, vol. 41, April, 2012.

[4] 3GPP documentation - Carrier Aggregation explained

http://www.3gpp.org/technologies/keywords-acronyms/101-carrier-

aggregation-explained

[5] 3GPP Technical Report R2-102490, “CA deployment scenarios,” NTT DOCOMO, INC.

[6] Z. Shen, A. Papasakellariou, J. Montojo, D. Gerstenberger, F.

Xu, „Overview of 3GPP LTE-Advanced Carrier Aggregation for

4G Wireless Communications“, IEEE Magazine, February, 2012.

[7] M. Al-Shibly, M. Habaebi, J. Chebil, “Carrier Aggregation in

Long Term Evolution- Advanced”, IEEE Control and System Graduate Research Colloquium, 2012.

[8] S. Ahmadi, “LTE-Advanced: A Practical System Approach to

Understanding the 3GPP LTE Releases 10 and 11 Radio Access Technologies”, Elsvier Science and technology Books, UK, 2014.

[9] H. Holma, A. Toskala,“LTE-Advanced: 3GPP Solution for

IMT-Advanced“, John Wiley& Sons, Inc., 2012

[10] Anritsu - Understanding LTE-Advanced Carrier Aggregation

https://www.anritsu.com/en-GB/Promotions/carrier-aggregation-

guide/registration.aspx [11] F. Ren, C. Wang, A. Chen, W. Sheen, „Introduction to Carrier

Aggregation Technology in LTE-Advanced Systems“, International

Conference on Advanced Information Technologies, 2011

[12] http://www.artizanetworks.com/lte_tut_adv_acceleration.html

[13] http://www.unwiredinsight.com/2014/lte-carrier-aggregation-

evolution

Figure 9. Downlink MAC Layer structure with CA

16



Volume 59(73), Issue 1, 2014

Telemetric Applications for the Automotive Industry using IQRF

devices

Victor Serban, Dan Andreiciuc, Aurel Filip

Abstract— The proposed system implies exploiting a

technology previously utilized in smart home automation, namely

IQRF boards, in the automotive industry. Employing these

devices, one can obtain a more versatile control of his/her vehicle,

as well as various aspects of environmental conditions, like

temperature or the intensity of light outside the vehicle. This

system constitutes of a modular hardware part, and multiple

software parts, each accomplishing some of the previously

enumerated notions. (Abstract)

Keywords—IQRF; Automotive; IQMESH; Telemetry (key words)

I. INTRODUCTION

IQRF is a sub GHz wireless communications technology. It is

intended where wireless general use connectivity is needed, be

it point to point, or in complex networks. Its functionality

depends only on a dedicated application written in the C

programming language.

The object of this application that is presented in this paper is

the integration of smart house applications in the automotive

industry.

The elementary IQRF communication is the transceiver

module including a microcontroller with an onboard operating

system, implementing the physical level, as well as the data

link level upholding the MESH network which utilizes the

open IQMESH protocol. No other superior level, like the

transport level is part of this technology.

II. IQRF MODULAR HARDWARE UTILIZED

IQRF Technology Characteristics

Among the main properties of the IQRF technology are: low speeds, low power consumption and low data rate, packet based oriented data radio frequency up to 128 Bits/packet, RF software selectable parameters, sub-GHz radio frequency bands using multi canal systems and FSK modulation, bit rate between 1,2 – 86,2kb/s, output power of maximum 20mW, output range of over 1 Km per hop, up to 240 hops per packet, up to 65000 devices in a single network, low power consumption (380nA in idle mode and 25 uA when receiving), the code can be uploaded wirelessly to all nodes in the same time and last but not least, there is no license acquisition fee.

III. HARDWARE CHARACTERISTICS

A. DK-EVAL-04

The DK-EVAL-04 is a universal development kit for wireless

IQRF transceivers. Its reduced size, LiPol accumulator and low

cost make this kit ideal for intelligent network application

usage.

Applications for this device include: the development of

wireless applications, host for TR IQRF modules, testing and

debugging of IQMESH networks and portable battery powered

wireless systems.

The simplified diagram of the board is presented in Fig.1.

B. CK-USB-04

The CK-USB-04 is a development kit oriented towards the

programming and debugging of user applications with IQRF

transceivers. It can also serve as a IQRF USB gateway (USB –

SPI converter) or just a simple host for the transceiver module.

Among the key applications are the following: programmer

board for the IQRF transceiver, IQRF debug kit, final IQRF

application host, USB host, USB – SPI converter and finally

PC connectivity. The simplified circuit diagram is presented in the Fig.2.

Fig.1 – Simplified diagram of the DK-EVAL-04 board

17

Fig.2 – Simplified diagram for the CK-USB-04 board

The network can be controlled using three words:

1. Node address

2. Peripheral number – indicates with which peripheral I can communicate with

3. Each peripheral number has different commands

Each packet can have 58 bits that can be used.

C. SHD-SE-01

The SHD-SE-01 is a multifunctional wireless sensor that gives

temperature readings, illumination, acceleration measurement,

has a real time clock as well as an EEPROM memory.

Its low power usage design allows its battery to last for years

on end.

The sensor can be adapted to user specific functionality

through application software for the microcontroller in the

operating system included transceiver module.

The key characteristics of the sensor are the following: smart

Transceiver station with built-in antenna, Selectable band of

FR 868 / 916 MHz with multiple channels, internal

microcontroller equipped with an operating system, compatible

with TR-54D, 3 axis accelerometer, temperature sensor, light

sensor, real time clock, serial EEPROM, tactile button, LED

indicator, ultra reduced power consumption, integrated primary

battery with a multi-year lifetime and a programmable

application in the internal transceiver module.

Fig.3 represents a picture of the SHD-SE-01 module.

Fig.4 will represent the simplified block diagram of the SHD-

SE-01 module.

Fig.3 Image of the SHD-SE-01 module

Fig.4 Simplified block diagram of the SHD-SE-01 module

IV. SOFTWARE ARCHITECTURE

Software architecture is defined by IEEE as: basic organization

of a system embodied in the system components, the

relationships between them and between system components

and the environment, and the principles governing the design

and evolution of the system. [ANSI/IEEE Std. 1471-2000,

Recommended Practice for Architectural Description of

Software-Intensive Systems].

The definition proposed by IEEE says that architecture

captures system structure in terms of its components and how

these components interact. The system architecture defines the

rules by which the system is designed as well as defining how

it can be changed.

An embedded enterprise architecture is organized in four

levels:

• drivers working with hardware (its abstraction).

• Basic Software - eg AdcHandler (mode like reading

series features several ADC channels, applying

transformations on the results).

• OS - basic skeleton of an operating system based on

tasks (model time-slice).

• Application - Module generic state machines,

controllers, error checking, etc.

18

This type of architecture is commonly used in automotive

industry. The proposed variant satisfies the portability and

future expansion, given the requirements and the complexity of

the application.

To demonstrate the feasibility of using IQRF devices, but also

to have a starting point for the concept car telemetry

integration in smart home, they realized some projects in the

IQRF IDE 4.7. The first project aims to familiarize with the

programming environment, the operating system and the

attached framework and programming devices and using

IQRF.

This first project carried out at switching supply or after reset,

the LED flashing three times. Upload file consists Start.c (v.

Annex) in one of microcontrollers (Fig.5).

The second project consists of a device programmed with Rx.c

file that will ide receive a package through LED lights, a

device that sends a message by pressing and sensor standard

program that sends all the data to a message by pressing. In

Fig.6's played such a system.

Fig.5 Start.c project

Fig.6 Second Project

The third project is a temperature sensor remote that receives

every 5 seconds data and sends to the USB port to be displayed

on the terminal that monitors communication between your

device and computer programming, feature offered by IQRF

IDE development environment. The devices involved in the

project are shown in Fig.7 and a screen capture after the

terminal window is shown in Fig.8. One can notice the

message wrong (and detected as erroneous) when the device

transmitter button is pressed and interfere with the

communication of the sensor.

The fourth project contains two devices. In the first is entered a

program that executes two commands: alters the duty cycle of

the PWM signal generated and lights five times the LED. With

this program you can control another device ON / OFF or can

act an actuator (motor, etc.). The second device is a transceiver.

Topology can be seen in Fig.9. In Fig.10 is shown connected to

the terminal window with TR.c, control messages are sent

manually with the author. Also, here is presented the

information in a message from SHD device containing data

that can provide it (from all sensors mounted).

Fig.7 Third Project

Fig.8 Temperature readings as seen on the screen

Start.c

E_RX_Temp.c

jamming

TX.c

TX.c

RX.c

19

Fig.9 The fourth project

Fig.10 Terminal window, message transmission and reception

Fig.11 – The fifth Project

The last project contains an interpretation program of the

messages coming from the SHD. The implementation is seen

in Fig.11. This program can be directly used to monitor the

automobile. Thus, alarms can be set if the vehicle is moved,

started, what temperature is inside, etc. Commands can be

sent, as seen in the previous project to lock the doors, stop the

engine, start the air conditioning, etc. The car will be as such

in a permanent state of monitoring and control.

One utility example can be seen when a person wants to leave

home in an hour. This is signaled to the smart house intelligent

system, which verifies the temperature in the car and in case it

is too high, turns on the air conditioning. In such a way the

vehicle will be ready for the voyage.

V. CONCLUSIONS

In the proposed paper is presented the exploitation of a

technology that until recently was used only in the smart home.

The idea to gather telemetry from inside a car is also an

innovative one not implemented by the time of the current

study.

The programs used in the C programming language are simple,

with no great complexity and can be easily carried, debugged

and tested.

The sensors have a battery life of several years, providing a

long and independent functionality comparable to the average

user to overhaul a car.

We can advance the application on IQRF devices in cars by

manipulating a visual control panel touchscreen display that

can receive both data and sensor nodes and monitor activity

programs running in them, besides work and monitor the

integrated smart home.

ACKNOWLEDGMENT

This work was partially supported by the Polithenica University of Timisoara, Department of Applied Electronics with the assistance of Assoc. Prof. Dr. Eng. Dan Andreiciuc.

REFERENCES

[1] APLICAȚII TELEMETRICE PENTRU INDUSTRIA AUTOMOTIVE

UTILIZÂND DISPOZITIVE IQRF, Serban Victor

[2] ***, http://en.wikipedia.org/wiki/Telemetry

[3] ***, http://en.wikipedia.org/wiki/Wireless_sensor_network

[4] ***, IQRF Quick Start Guide,

http://www.iqrf.org/weben/index.php?sekce=support&id=download

[5] ***, IQRF Technical Guide,


[6] ***, DK-EVAL-04 User’s Guide,


[7] ***, CK-USB-04 User’s Guide,


[8] ***, SHD-SE-01 User’s Guide,


[9] ***, Wikipedia, http://en.wikipedia.org/wiki/IQRF

[10] ***, SOS Electronic Webinar, http://www.soselectronic.com/?str=1426

[11]. Brian Kernighan and Dennis Ritchie, The C Programming Language,

1978 (1st edition), Englewood Cliffs, NJ: Prentice Hall. ISBN 0-13-110163-3.

TR.c

multi_com.c

prel_msg_SHD.

20



Volume 59(73), Issue 1, 2014

Multifunctional Siren for Emergency Services

Cătălin Tudoran1 Dan Andreiciuc

2 Aurel Filip

3

1 E-mail [email protected] 2 Faculty of Electronics and Telecommunications, Applied Electronics Dept., Bd. V. Pârvan, 300223 Timisoara, Romania, e-mail [email protected] 3 Faculty of Electronics and Telecommunications, Applied Electronics Dept., Bd. V. Pârvan, 300223 Timisoara, Romania, e-mail

[email protected]

Abstract – this paper presents a solution for the design

of a multifunctional siren for emergency services (police,

ambulance, special services etc). Such a device should

have two functionalities: both as a voice amplifier and as

a tone generator. When designing such a circuit, a D

class amplifier has been considered for the amplification

and a PIC microcontroller for the tone generation. A

switch should be used to interchange these

functionalities and user buttons must be provided for

configuring the tone libraries.

Keywords: siren, class D amplifier, PIC, microcontroller

I. INTRODUCTION

From the beginning of time, sounds have been used

by every living being on this planed as a means of

communication. By means of sounds we can

communicate almost everything, from simple words

to tones used in warning systems. From the physical

point of view, sound is a vibration that propagates as a

typically audible mechanical wave of pressure and

displacement, through a medium such as air, and

water. In physiology and psychology, sound is the

reception of such waves and their perception by the

brain. Sound waves are often simplified to a

description in terms of sinusoidal plane waves, which

are characterized by the following properties:

frequency, wavelength, wavenumber, amplitude,

sound pressure, sound intensity, speed of sound and

direction. The human ear can only perceive sounds

with frequencies between 20 Hz and 20 kHz with a

maximum audibility around 3500 Hz. This interval is

mainly influenced by the amplitude of the vibrations

and the age and health of the individual.

II. POWER AMPLIFIERS

An audio power amplifier is an electronic amplifier

that amplifies low-power audio signals (signals

composed primarily of frequencies between 20 - 20

000 Hz, the human range of hearing) to a level

suitable for driving loudspeakers. It is the final

electronic stage in a typical audio playback chain.

Because power amplifiers are large-signal amplifiers,

a much larger portion of the load line is used during

signal operation than in a small-signal amplifier.

There are a few basic classes of power amplifiers:

class A, class B, class AB, class C and class D. These

amplifier classifications are based on the percentage

of the input cycle for which the amplifier operates in

its linear region. Each class has a unique circuit

configuration because of the way it must be operated.

The emphasis is on power amplification. Power

amplifiers are normally used as the final stage of a

communications receiver or transmitter to provide

signal power to speakers or to a transmitting antenna.

Fig.1. Basic example of a power amplifier, where:

− η% is the efficiency of the amplifier.

− Pout is the amplifiers output power delivered to the load.

− Pdc is the DC power taken from the supply.

A. Class A amplifiers

The Class A amplifier is the most common and

simplest form of power amplifier that uses the

switching transistor in the standard common emitter

circuit configuration. The transistor is always biased

“ON” so that it conducts during one complete cycle of

the input signal waveform producing minimum

distortion and maximum amplitude to the output.

Both large-signal and small-signal amplifiers are

considered to be class A if they operate in the linear

region at all times. Class A power amplifiers are

large-signal amplifiers with the objective of providing

power (rather than voltage) to a load. As a rule of

thumb, an amplifier may be considered to be a power

amplifier if it is rated for more than 1 W and it is

necessary to consider the problem of heat dissipation

21

in components. The maximum theoretical power

efficiency of a Class A amplifier is between 25% and

50%, depending upon the type of output coupling

used. The main disadvantage of power amplifiers and

especially the Class A amplifier is that their overall

conversion efficiency is very low as large currents

mean that a considerable amount of power is lost in

the form of heat.

Fig.2. Basic class A amplifier operation. Output is shown 180° out

of phase with the input (inverted)

B. Class B and AB amplifiers

The class B amplifier operates in the linear region for

180° of the input cycle and is in cutoff for the rest of

the 180° of the cycle. Class AB amplifiers are biased

to conduct for slightly more than 180°. The primary

advantage of a class B or class AB amplifier over a

class A amplifier is that either one is more efficient

than their class A counterpart, so as a result, you can

get more output power for a given amount of input

power. A disadvantage of class B or class AB is that it

is more difficult to implement the circuit in order to

get a linear reproduction of the input waveform. The

term push-pull refers to the fact that two transistors

are used on alternating half-cycles to reproduce the

input waveform at the output.

Fig.3. Basic class B amplifier operation (noninverting)

C. Class C amplifiers

Class C amplifiers are biased so that conduction

occurs for much less than 180°. Class C amplifiers are

more efficient than either class A or push-pull class B

and class AB, which means that more output power

can be obtained from class C operation. The output

amplitude is a nonlinear function of the input, so class

C amplifiers are not used for linear amplification.

They are generally used in radio frequency (RF)

applications, including circuits, such as oscillators,

that have a constant output amplitude, and

modulators, where a high-frequency signal is

controlled by a low-frequency signal. With class B,

one needs to use a push-pull arrangement. That’s why

almost all class B amplifiers are push-pull amplifiers.

With class C, one needs to use a resonant circuit for

the load. This is why almost all class C amplifiers are

tuned amplifiers.

Fig.4. Basic class C amplifier operation (noninverting)

D. Class D amplifiers

A class-D amplifier or switching amplifier is an

electronic amplifier where all power devices (usually

MOSFETs) are operated as binary switches. They are

either fully on or fully off. Ideally, zero time is spent

transitioning between those two states. Output stages

such as those used in pulse generators are examples of

class D amplifiers. However, the term mostly applies

to power amplifiers intended to reproduce signals

with a bandwidth well below the switching frequency.

In Classes A, B and AB, the problem is lack of

efficiency. Some power is wasted, and one would

prefer that it could be sensibly employed in driving

the loudspeakers to ever-higher sound pressure levels

(or, at least, not converted to heat).

Fig.5. Block diagram of a basic switching or PWM (class D)

amplifier

A Class D amplifier has three main stages, the first of

which is the modulation stage. In a Class D amplifier,

the signal must be converted to a digital signal before

being amplified. There are several ways to accomplish

this; the two most widely used are Pulse Width

Modulation and Delta-Sigma (∆Σ) Modulation. Each

method has advantages and disadvantages. After the

signal is modulated, it must be amplified. The

amplification stage in a Class D amplifier uses several

Metal Oxide Semiconductor Field Effect Transistors

(MOSFETs), a different kind of transistor with very

low power losses. The MOSFETs in a Class D

amplifier can switch between fully on and fully off

because they are amplifying a digital signal, avoiding

the triode region where power efficiencies drop.

When completely on in the active region, or

completely off in the cutoff region, MOSFETs are

theoretically lossless and in practice have very low

power losses. After the modulated signal is amplified,

it must be filtered before it can be sent to a speaker.

The last stage is the filtering, or demodulation, stage,

which consists of a low pass filter. This allows

everything in the audible range (20 Hz - 20 KHz) to

pass through, but significantly attenuates everything

above 20 KHz. After being filtered, the signal is an

amplified replica of the original input signal, and can

be applied directly to a speaker.

22

What generally happens in class D amplifiers is that

that the transistors switch alternately to lift the output

all the way up to the positive supply rail, then all the

way down to the negative supply rail, as quickly as

possible, with no in-between voltages. This is clearly

going to be a pulse waveform. The secret to class D is

that if the width of the pulses can be made

proportional to the input signal's instantaneous level,

the power delivered to the loudspeaker, averaged over

time, will be the same as if the input signal had been

amplified in the conventional way.

Fig.6. Class D amplifier waveforms

Generally speaking, class D amplification is achieved

by modulating a signal, amplifying the modulated

signal and then filtering the amplified signal back into

its original form. Since Class D amplifiers work with

digital signals, they do not require that the transistors

involved operate in the triode region and, as a result,

they are much more efficient than other amplifiers.

This method of amplification has been used in

portable audio devices, cell phones and low fidelity

audio where size, power and heat dissipation are of

great concern. The advantages of Class D, however,

can also be applied to the larger systems required for

live audio. The reduction in power consumption made

possible by a Class D system is sometimes considered

unnecessary for live audio because the size and

efficiency of an audio system is not usually a concern

when the system is permanently installed in a venue

and the power is drawn from the wall. In our case,

however, when we are speaking about emergency

services and cars equipped with sirens and voice

amplifiers, this advantage becomes very attractive.

Class D amplifiers have historically only been used in

a limited number of applications, like motor control,

because it is more difficult to generate the high quality

signals required for audio applications with a Class D

amplifier. Recently, however, Class D technology has

advanced sufficiently to allow these amplifiers to

accurately and cleanly amplify audio signals. There

are many advantages to using Class D amplifiers for

audio applications, and the number of disadvantages

is shrinking every year with further advances in

technology.

III. ADVANTAGES AND DISADVANTAGES

OF CLASS D AMPLIFIERS

Further on, some advantages and disadvantages of

Class D amplifiers will be presented. Despite the

complexity involved, a properly designed class D

amplifier offers the following benefits:

− reduced power waste as heat dissipation

− because of the above, a reduction in cost, size and

weight of the amplifier due to smaller (or no) heat

sinks, and compact circuitry

− very high power conversion efficiency, usually

better than 90% above one quarter of the

amplifier's maximum power, and around 50% at

low power levels.

While Class D amplifiers have been in use for many

years, only recently have they come to the forefront of

audio amplification. This is because Class D

amplifiers have a number of disadvantages that make

them less suitable for audio amplification, though

many of these have been overcome with recent

advances in technology. One major disadvantage is

that a Class D amplifier has a very high amount of

high frequency noise, generated by the switching

design. This noise must be kept at a high enough

frequency to be inaudible, yet to a minimum

amplitude to meet Federal Communications

Commission (FCC) regulations. To help reduce

extraneous noise, a filter is added after the amplifying

stage. This filter is an additional component of the

Class D amplifier, and adds complexity, weight, and

cost. The added weight is negligible, however, when

compared to the weight of the heat sink required for a

Class A, Class AB or Class B amplifier. The

additional cost of a filter may also be minimized using

careful design techniques. Since the filter only needs

to attenuate signals above the audible frequencies, it is

not essential that the filter be extremely precise. The

filter may therefore be realized by a fairly simple,

low-pass, passive filter.

A second deficiency of Class D amplifiers is the

increased complexity in design. This may result in

increased design time and expense. Increased design

expenses are generally considered acceptable,

however, if the result is a lower manufacturing cost

because design is singular expense, whereas

manufacturing expenses are recurring. After the

amplifier is designed, most of the components, with

the possible exception of any inductors used in the

filter and specialized MOSFETs in the power stage,

are extremely inexpensive when purchased in bulk.

So while the increased complexity seems like a major

disadvantage, it may become irrelevant when the

amplifiers are mass-produced.

The last major disadvantage of Class D amplifiers is

that historically, distortion has been a major problem.

High Total Harmonic Distortion (THD) is indicative

of high noise levels, which detract significantly from

the audio quality of the output. Advances in

technology have allowed for faster modulation

23

techniques, however, which can reduce THD to

fractions of a percentage in Class D audio amplifiers.

After consideration of advantages and disadvantages,

the conclusion would be that such a Class D amplifier

is ideal for use in vehicles and especially when

equipping it for emergency services. Because of the

light weight, low power consumption and relatively

high quality output, it would serve the purpose of this

project.

IV. THE TDA7498 AMPLIFIER

The TDA7498 is a dual BTL class-D audio amplifier

with single power supply designed for home systems

and active speaker applications. It comes in a 36-pin

PowerSSO package with exposed pad up (EPU) to

facilitate mounting a separate heat sink. Some of its

features are described below:

− 100 W + 100 W output power at THD = 10%

with RL = 6 Ω and VCC = 36 V

− 80 W + 80 W output power at THD = 10% with

RL = 8 Ω and VCC = 34 V

− Wide range single supply operation (14 - 39 V)

− High efficiency (η = 90%)

− Four selectable, fixed gain settings of nominally

25.6 dB, 31.6 dB, 35.1 dB and 37.6 dB

− Differential inputs minimize common-mode noise

− Standby and mute features

− Short-circuit protection

− Thermal overload protection

− Externally synchronizable

Such a device will have as input a microphone (for

example, a CB Mic, because it has buttons for on/off

and is portable) and as output, the loudspeakers. The

device will amplify the sounds coming from the

microphone when necessary.

V. THE PIC16F84A MICROCONTROLLER

The PIC16F84A is an 18-pin Enhanced

FLASH/EEPROM 8-Bit Microcontroller. It belongs

to the mid-range family of the PICmicro®

microcontroller devices. Some of the features are

described below:

A. High Performance RISC CPU Features

• Only 35 single word instructions to learn

• All instructions single-cycle except for program

branches which are two-cycle

• Operating speed: DC - 20 MHz clock input DC -

200 ns instruction cycle

• 1024 words of program memory

• 68 bytes of Data RAM

• 64 bytes of Data EEPROM

• 14-bit wide instruction words

• 8-bit wide data bytes

• 15 Special Function Hardware registers

• Eight-level deep hardware stack

• Direct, indirect and relative addressing modes

• Four interrupt sources:

- External RB0/INT pin

- TMR0 timer overflow

- PORTB<7:4> interrupt-on-change

- Data EEPROM write complete

B. Peripheral Features

• 13 I/O pins with individual direction control

• High current sink/source for direct LED drive

- 25 mA sink max. per pin

- 25 mA source max. per pin

• TMR0: 8-bit timer/counter with 8-bit programmable

prescaler

C. Special Microcontroller Features

• 10,000 erase/write cycles Enhanced FLASH

Program memory typical

• 10,000,000 typical erase/write cycles EEPROM

Data memory typical

• EEPROM Data Retention > 40 years

• In-Circuit Serial Programming™ (ICSP™) - via two

pins

• Power-on Reset (POR), Power-up Timer (PWRT),

Oscillator Start-up Timer (OST)

• Watchdog Timer (WDT) with its own On-Chip RC

Oscillator for reliable operation

• Code protection

• Power saving SLEEP mode

• Selectable oscillator options

D. CMOS Enhanced FLASH/EEPROM Technology

• Low power, high speed technology

• Fully static design

• Wide operating voltage range:

- Commercial: 2.0V to 5.5V

- Industrial: 2.0V to 5.5V

• Low power consumption:

- < 2 mA typical @ 5V, 4 MHz

- 15 µA typical @ 2V, 32 kHz

- < 0.5 µA typical standby current @ 2V

The above mentioned microcontroller will be used

mainly for tone generation as C libraries exist that can

facilitate the process of writing code.

VI. THE RESULT

The desired result of this project would be a working

circuit that could fit into any vehicle. It’s function

would be two-fold: one as a siren and the other as a

tone generator. A switch will be used to activate either

one of these functions. Besides the button on the CB

Microphone, which will activate the voice

amplification, the device will have other buttons that

control the siren function. When the siren

24

functionality is activated, the user should be able to

switch between the different sound warning standards

of the world. By pressing and holding a button, the

device will enter a configuration mode and the user

will be able to select the desired tones. After

selection, the configuration mode can be exited with a

long press of the same button. Apart from this, the

device will be equipped with an ON/OFF switch and

LED indicators that should indicate in which mode it

is now and if the device is working properly.

REFERENCES

[1] Thomas L. Floyd, "Electronic Devices"

[2] http://www.electronics-tutorials.ws/amplifier/amp_5.html

[3] http://www.mikroe.com/chapters/view/17/chapter-4-

examples/#c4v1 [4] http://en.wikipedia.org/wiki/Sound

[5] http://highered.mcgraw-

hill.com/sites/dl/free/007297527x/329094/malvinoch12.pdf [6] http://en.wikipedia.org/wiki/Class-D_amplifier

[7] Jun Honda & Jonathan Adams "Application Note AN-1071 -

Class D Audio Amplifier Basics"

[8]

http://www.soundonsound.com/sos/jun06/articles/loudandlight.htm

[9] Briana Morey, Ravi Vasudevan, Ian Woloschin, "Class D Audio

Amplifier - The design of a live audio Class D audio amplifier with

greater than 90% efficiency and less than 1% distortion",

WORCESTER POLYTECHNIC INSTITUTE - May 2008

[10] PIC16F84A microcontroller datasheet

[11] TDA7498 amplifier datasheet

25



Volume 59(73), Issue 1, 2014

Modeling in Matlab/Simulink the control of the vehicle’s

air conditioner compressor

Lupou Cristian Marius1

1 Faculty of Electronics and Telecommunications, Electronic Dept., Master

Bd. V. Parvan 2, 300223 Timisoara, Romania,

Abstract – This article presents a model developed in

MATLAB/SIMULINK, for the control of the vehicle’s

air conditioner compressor with a PWM signal. This

signal is used to control the solenoid valve of the

compressor. The model was created to allow in the

future the study of the compressor’s behavior in

different operating conditions of the vehicle to improve

the functioning of the internal combustion motor and

optimize the efficiency of the air conditioner system.

The model will be converted to a software script to be

used in the car together with the AutoBox from dSpace.

Keywords: air conditioner, compressor, model,

AutoBox, dSpace

I. INTRODUCTION

Air conditioning systems have long ceased to be

regarded as luxury equipment. Air conditioners have

become a factor in active safety, and today can almost

be considered as an integral part of a vehicle's safety

specification. 10 years ago, only about 10 percent of

all newly registered vehicles were fitted with an air

conditioning system. By 1996, air conditioners were

being installed as standard in more than one in four

newly registered vehicles. The design of the

refrigerant circuit of an air conditioner is identical in

all vehicles. Air conditioner refrigerant circuits only

vary in respect of how they are adapted to meet

refrigeration requirements, [1].

People feel comfortable at a certain ambient

temperature and atmospheric humidity. As a

component part of active safety, the driver's well-

being is a key factor in driving ability. The “in-car

climate” has a direct bearing on the driver, fatigue-

free driving and driving safety. A comfortable interior

temperature is dependent upon the prevailing ambient

temperature and upon sufficient air flow:

Low ambient temperature, e.g. -20 °C

Higher interior temperature 28 °C

High air flow rate: 8 kg per min.

High ambient temperature, e.g. 40 °C

Low interior temperature 23 °C

High air flow rate: 10 kg per min.

Modarate ambient temperature, e.g. 10 °C

Low interior temperature 21.5 °C

Low air flow rate: 4 kg per min

Fig. 1. The interior temperature and the air flow rate depending

on the ambient temperature

Fig. 2. The interior temperature with and without the air

conditioning

Even modern heating and ventilation systems have

difficulty maintaining a pleasant climate inside a

vehicle at high ambient temperatures. In strong

sunlight in particular, the heated cabin air can only be

exchanged for air with ambient temperature. In

addition, the air temperature usually rises on route

from the intake point to the air outlet. Opening a

window or sliding roof or setting a higher fan speed

for greater comfort will usually result in a draught and

expose the occupants to other nuisances such as noise,

exhaust gases and pollen, [1].

High levels of atmospheric humidity put the body

under considerably greater physical strain.

Scientific studies conducted by the WHO (World

Health Organization) have shown that one's ability to

concentrate and reactions are impaired when under

26

Fig. 3. Comfort range

stress. Heat puts a strain on the body. The best

temperature for the driver is between 20 and 22 °C.

This is equivalent to climatic load A (see Fig.3), the

"comfort range".

Strong sunlight can increase the interior temperature

by more than 15 above the ambient temperature

particularly in the head area. This is where the effects

of heat are most dangerous. The body temperature

rises and the heart rate increases. Heavier perspiration

will typically occur, too. The brain is not receiving

enough oxygen. Also refer to "climatic load range B".

Climatic loads in range C put an excessive strain on

the body. Physicians specializing in traffic-related

illnesses refer to this condition as “climatic stress”,

[1].

Studies have shown that an increase in temperature

from 25 to 35 °C reduces one's sensory perception and

powers of reasoning by 20%. It has been estimated

that this figure is equivalent to a blood alcohol

concentration of 0.5 milliliters alcohol level.

II. THE REFRIGERANT

The refrigerant with a low boiling point used for

vehicle air conditioners is a gas. As a gas, it is

invisible. As a vapour and as a liquid, it is colorless

like water. Refrigerants may not be combined with

each other. Only the refrigerant specified for the

system in question may be used. [1]

With regard to vehicle air conditioners, the sale and

filling of refrigerant R12 were banned in Germany

with effect from 1995 and July 1998 respectively.

In current automotive air conditioners, only

refrigerant R134a is used. R134a, a fluorocarbon

contains no chlorine atoms, unlike refrigerant R12,

which cause depletion of the ozone layer in the earth's

atmosphere when they split. The vapour pressure

curves of R134a and R12 are very similar. R134a has

the same refrigeration capacity as R12. Depending on

the pressure and temperature conditions in the

refrigerant circuit, the refrigerant will either be a gas

or a liquid.

In addition to the vapour pressure curve, the cycle

shows the change of state of the refrigerant under

Table 1

Parameter Value Unit Boiling point -26.5

Freezing point -101.6

Critical temperature 100.6

Critical pressure 4.056/40.56 MPa/bar

Fig. 4. The cycle in an air conditioner

pressure and temperature in addition to the energy

balance at which the refrigerant returns to its original

state. The diagram is an excerpt from the state

diagram of refrigerant R134a for a vehicle air

conditioner. Different absolute values are possible in

dependence upon the demand of a vehicle type for

refrigeration capacity.

The energy content is a key factor in the design of an

air conditioner. It shows what energy is required

(evaporator heat, condenser heat) to achieve the

intended refrigeration capacity.

Ozone protects the earth's surface against UV

radiation by absorbing a large proportion of these

rays. UV rays split ozone (O_3) into an oxygen

molecule (O_2) and in an oxygen atom (O). Oxygen

atoms and oxygen molecules from other reactions

combine again to form ozone. This process takes

place in the ozonosphere, a part of the stratosphere at

an altitude of between 20 and 50 km.

III. THE COOLING SYSTEM

We know that too cool down an object, heat must be

given off. A compression refrigeration system is used

in motor vehicles for this purpose. A refrigerant

circulates in the closed circuit, continually alternating

changing from a liquid to a gas and vice versa. The

refrigerant is:

• compressed in the gaseous state

• condensed through heat dissipation

• evaporated through pressure reduction and heat

absorption.

27

Cool air is not produced, heat is extracted from the air

flow in the vehicle.

The compressor induces cold, gaseous refrigerant at a

low pressure. The refrigerant is compressed in the

compressor, causing it to heat up. The refrigerant is

pumped into the circuit on the high-pressure side.

The compressed liquid refrigerant continues to flow

up to a narrowing. This narrowing can be in the form

of a restrictor or an expansion valve. Once the

refrigerant reaches the narrowing, it is injected into

the evaporator causing its pressure to drop (low-

pressure side).

Inside the evaporator, the injected liquid refrigerant

expands and evaporates. The evaporation heat

required for this purpose is extracted from warm fresh

air which cools down when it passes through the

evaporator fins. The temperature inside the vehicle is

reduced to a pleasant level.

The components from figure 5 are as follows:

A Compressor with magnetic clutch

B Condenser

C Fluid container with drier

D High pressure switch

E High pressure service connection

F Expansion Valve

G Evaporator

H Low pressure service connection

I Damper (vehicle specific

The refrigerant follows the short path to the condenser

(liquefier). Heat is now extracted from the

compressed, hot gas in the condenser by the air

flowing through (headwind and fresh air blower). The

refrigerant condenses and becomes a liquid when it

reaches its melting point (pressure dependent), [1].

Now in the gaseous state again, the refrigerant

emerges from the evaporator. The refrigerant is again

drawn in by the compressor and passes through the

cycle once again. Thus, the circuit is closed.

The refrigeration capacity of a vehicle air conditioner

is dependent upon the car-specific installation

conditions and the vehicle category (passenger cars,

Fig. 5. The air conditioner circuit with expansion valve

Fig. 6. Localization of the refrigerant circuit in the car

vans). The components A to H exist in every circuit.

Additional connections can be provided for service

work, temperature sensors, pressure switches in the

high- and low-pressure circuit and oil drain screws

depending on the circuit design and requirements. The

layout of components within the circuit also differs

from one vehicle type to another. Some systems have

a damper before the compressor in order to dampen

refrigerant vibrations.

The pressures and temperatures in the circuit are

always dependent on momentary operating state. The

specified values are intended as a rough guideline

only. They are reached after 20 min. at an ambient

temperature of 20 and at engine speeds of between

1500 and 2000 rpm. At 20 and when the engine

is at a standstill, a pressure of 0.47 MPa (4.7 bar) will

build up inside the refrigerant circuit.

IV. THE COMPRESSOR

The compressors used in vehicle air conditioners are

oil-lubricated displacement compressors. They

operate only when the air conditioner is switched on,

and this is controlled by means of a magnetic clutch.

The compressor increases the pressure of the

refrigerant. The temperature of the refrigerant rises at

the same time. Were there to be no pressure increase,

it would not be possible for the refrigerant in the air

conditioner to expand and therefore cool down

subsequently. A special refrigerant oil is used for

lubricating the compressor. About half of it remains in

the compressor while the other half is circulated with

the refrigerant. A pressure shut-off valve, which is

usually attached to the compressor, protects the

system against excessively high pressures, [1].

Fig. 7. Compressor with magnetic clutch

28

The compressor draws in cold, gaseous refrigerant

through the evaporator under low pressure. It is "vital"

for the compressor that the refrigerant be in a gaseous

state, because liquid refrigerant cannot be compressed

and would destroy the compressor (in much the same

way as a water shock can damage an engine). The

compressor compresses the refrigerant and forces it

towards the condenser as a hot gas on the high-

pressure side of refrigerant circuit. The compressor

therefore represents the interface between the low-

pressure and high-pressure sides of the refrigerant

circuit.

Compressors for air conditioners operate according to

various principles:

• Reciprocating compressors

• Coiled tube compressors

• Vane-cell compressors

• Wobbleplate compressors

The turning motion of the input shaft is converted to

an axial motion (= piston stroke) by means of the

wobbleplate. Depending on compressor type, between

3 and 10 pistons can be centred around the input shaft.

A suction/pressure valve is assigned to each piston.

These valves open/close automatically in rhythm with

the working stroke. An air conditioner is rated for the

max. speed of the compressor. However, the

compressor output is dependent on engine rpm.

Compressor rpm differences of between 0 and 6000

rpm can occur. This affects evaporator filling as well

as the cooling capacity of the air conditioner.

Controlled-output compressors with a variable

displacement were developed in order to adapt

compressor output to different engine speeds, ambient

temperatures or driver-selected interior temperatures.

Compressor output is adapted by adjusting the angle

of the wobbleplate. In constant-displacement

compressors, compressor output is adapted to the

demand for refrigeration by switching the compressor

on and off periodically via the magnetic clutch.

All control positions between upper stop (100 %) and

the lower stop (approx. 5 %) are adapted to the

required delivery rate by altering the chamber

pressure. The compressor is on continuous duty

during the control cycle.

The turning motion of the input shaft is transmitted to

the drive hub and converted to axial motion of the

piston via the wobbleplate. The wobbleplate is located

Fig. 8. Compressor

longitudinally in a slide rail. The piston stroke and the

delivery rate are defined by the inclination of the

wobbleplate.

Inclination - dependent on the chamber pressure and

hence the pressure conditions at the base and top of

the piston. The inclination is supported by springs

located before and after the wobbleplate.

Chamber pressure - is dependent upon the high and

low pressures acting upon the regulating valve and by

the calibrated restrictor bore.

High pressure, low pressure and chamber pressure are

equal when the air conditioner is off.

The springs before and after the wobbleplate set it to a

delivery rate of about 40%. The advantage of output

control is that it eliminates compressor cut-in shock,

which often manifests itself in a jolt while driving.

V. THE CONTROL COMPRESSOR MODEL

In the first part of the description is presented the

model implemented in SIMULINK. Simulink is a

block diagram environment for multidomain

simulation and Model-Based Design. It supports

system-level design, simulation, automatic code

generation, and continuous test and verification of

embedded systems. Simulink provides a graphical

editor, customizable block libraries, and solvers for

modeling and simulating dynamic systems. It is

integrated with MATLAB, enabling you to

incorporate MATLAB algorithms into models and

export simulation results to MATLAB for further

analysis, [2].

This model was created for the control of the

vehicle’s air conditioner compressor with a PWM

signal. This signal is used to control the solenoid

valve of the compressor. After the model is

developed, it used to be uploaded to the ControlDesk.

The model will be compiled on the PC and the

resulting script is loaded on an AutoBox from

dSPACE and the results are then shown both on the

ControlDesk and on the oscilloscope. AutoBox is the

ideal environment for using your dSPACE real-time

system for in-vehicle control experiments such as test

drives for powertrain, ABS or chassis control

development. You can install AutoBox anywhere in a

vehicle, for example, in the trunk of your test car.[5]

On the AutoBox we have the DS2201 board which

will be used in the project. The DS2201 Multi I/O

Board provides a space-saving solution for

applications requiring a lot of I/Os, [6].

The model implemented in SIMULINK is based on

the schematic shown in figure 10. Same as other types

Fig. 9. The Autobox

29

of AC compressors, the externally controlled one

essentially needs to compress AC refrigerant. The

pressurized refrigerant flows through condenser

where it can be cooled down by the engine cooling

fan and/or vehicle movement. This subsequently

reduces pressure to certain level. The refrigerant

passes through TxV (thermostat expansion valve)

where the expanded refrigerant becomes cool. The

cooling is then brought away by the air through the

evaporator. The cooled air from evaporator is then

produced for cabin cooling and dehumidification.

Externally controlled compressor has two controllable

parts, namely clutch and control valve. The same as

internally controlled compressor and fixed

displacement compressor, the AC clutch can make the

compressor fully turning and fully stopping. The

engagement of the clutch makes compressor

switching on (turning) and the disengagement makes

compressor switching off (stopping). The compressor

is driven by engine crankshaft via pulley.

The control valve makes the compressor be called

'Externally controlled' which adds more control ability

than other used compressors. The valve is installed

between 3 chambers inside the compressor, e.g.

discharge, suction and crankcase. The fully open/close

of the valve can make the passage available between

discharge and crankcase chambers or between

crankcase and suction chambers (depends on

suppliers). The valve is a solenoid driven. A PWM

signal is to deliver required control current on the

valve solenoid. The current level is corresponding to

the valve open position which consequently

determines the suction pressure that can be

maintained at steady-state. There is also a bleeding

passage between crankcase and suction chambers.

That makes crankcase pressure tend to equalize to

suction pressure. The pressure levels in the three

chambers and compressor turning speed determines

the position of the swash plate that results in different

compressor piston displacement. The displacement

will give rise to different compressor capacity and

different torque loss.

Fig. 10. Compressor

The model uses some inputs signals which are

calibrated in order to avoid malfunctions for the

vehicle’s motor and for the mechanical components

in the circuit of the air conditioner. These inputs are:

the ambient temperature, the activation ratio of

accelerator pedal, the engine speed, the coolant

temperature, the refrigerant pressure for the air

conditioner compressor, the evaporator temperature

and the time after start.

For the critical switch of conditions such as critical

engine speed, defective fan, critical cooling pressure,

critical cooling temperature or critical ambient

temperature, it is used a minimum turn-on time and a

minimum turn-off time.

If the vehicle has climate control module which can

create an evaporator temperature set point, then ECU

will use the evaporator temperature set point signal

in the close loop controller. Otherwise, ECU needs to

create the evaporator temperature set point according

to a calibrated table based on ambient temp.

The AC valve duty cycle must be obtained from a PID

controller with input of the difference between evap

temp and evap temp set point. The PID controller is

the most common controlling algorithm based on

system feedback form. The “textbook” version of the

PID algorithm is described by:

( ) ( ) ( )( )

+τ∫ τ+=

dt

tdeTde

TteKtu d

t

i 0

1 (1)

where y is the measured process variable, r the

reference variable, u is the control signal and e is the

control error (e = ysp – y). The reference variable is

often called the set point. The control signal is thus a

sum of three terms: the P term, (which is proportional

to the error), the I term (which is proportional to the

integral of the error), and the D term (which is

proportional to the derivative of the error). The

controller parameters are proportional gain K, integral

time Ti, and derivative time Td. The integral,

proportional and derivative part can be interpreted as

control actions based on the past, the present and the

future, [3].

During idle, the result of the evap temp closed loop

controller should be restricted by an extra regulator.

Fig. 11. The model

30

If demanded torque is smaller than a lower threshold,

then the duty cycle obtained from the evap temp

closed loop controller should be directly used. The

lower threshold is the product of max available torque

and a calibrated factor.

If demanded torque is greater than an upper threshold,

then a valve duty cycle increment should be used. The

increment is obtained from a calibrated table as a

function maximum available torque. The upper

threshold is the product of max available torque and

another calibrated factor.

If engine is in launch operation, then the AC

compressor should work at a degraded condition or

disengage AC clutch. At transition of A/C clutch

engagement to disengagement due to launch cut-out,

initialized cut-out timer starts decrementing.

If there is any request to minimize the AC valve duty

cycle for any function, then the valve duty cycle

should be firstly minimized to a calibrated level. If

AC clutch is disengaged for AC off request, then the

valve duty cycle should also be minimized.

The model will be then compiled and for

optimization, the model was simulated with a single

step, discret, and with the ode 5 solver. After the

simulation there were generated o series of files with

different extensions, from them de .sdf file was used.

First part of the experiment in ControlDesk is to

create a project for which the .sdf file from the

Simulink model, will be used. For visualization and

controlling the desired parameters the a .lay file will

be used, after this we can use different instrument like

controllers, indicators, plotters etc. In figure 12, we

have a GUI made in the ControlDesk, the interface

presents the inhibitions from the model in Simulink,

respectively the ambient temperature, the activation

ratio of accelerator pedal, the engine speed, the

coolant temperature, the refrigerant pressure for the

air conditioner compressor, the evaporator

temperature and the time after start.

In the last part of the experiment, the PWM signal

from the model is present on one pin from the

Fig. 12. The GUI from ControlDesk

Fig. 13. The PWM signal on the osciloscope

DS2201 board on the AutoBox. The signal can be

seen on the oscilloscope, as shown in figure 13. In

order to see the signal on the DS2201 board we have

to use the dSPACE RTI1005 library in the Simulink

model. This library consits of : I/O units for ADC,

DAC convertors, digital I/O, signal generation and

frequency measurements. Real-Time Interface (RTI)

is the link between dSPACE hardware and the

development software MATLAB/Simulink/Stateflow

from The MathWorks, [7].

VI. CONCLUSION

The model was developed for the control of the

vehicle’s air conditioner compressor using a PWM

signal. The AutoBox from dSPACE together with the

ControlDesk helps us represent the signal in Real

Time.

REFERENCES

[1] Air Conditioner in the Motor Vehicle, Self-Study Programme

208

[2] Getting Started Guide - Simulink, Matlab & Simulink,

MathWorks, 2014

[3] Karl Johan Åström, Control System Design, Lecture Notes for

ME 155A, Santa Barbara, 2000 [4] Simulink. Simulation and Model-Based Design, MathWorks,

2014

[5]http://www.dspace.com/en/pub/home/products/hw/accessories/a

utobox.cfm

[6] Hardware Installation and Configuration Refrence, Modular

Systems, dSPACE

[7] Real Time Interface from dSPACE

31

Buletinul Ştiinţific al Universităţii Timişoara


Volume 59(73), Issue 2, 2014

Instructions for authors at the Scientific Bulletin of the

Politehnica University of Timisoara - Transactions on

Electronics and Communications

First Author1 Second Author

2

1 Faculty of Electronics and Telecommunications, Communications Dept. Bd. V. Parvan 2, 300223 Timisoara, Romania, e-mail [email protected] 2 Faculty of Electronics and Telecommunications, Communications Dept.


Abstract – These instructions present a model for editing

the papers accepted at the Scientific Bulletin of

“Politehnica” University of Timisoara, Transactions on

Electronics and Communications. The abstract should

contain the description of the problem, methods,

solutions and results in a maximum of 12 lines. No

references are allowed here.

Keywords: editing, Bulletin, author

I. INTRODUCTION

The page format is A4. The articles must be of 6

pages or less, tables and figures included.

II. GUIDELINES

The paper should be sent in this standard form. Use a

good quality printer, and print on a single face of the

sheet. Use a double column format with 0.5 cm in

between columns, on an A4, portrait oriented,

standard size. The top and bottom margins should be

of 2.28 cm, and the left and right margins of 2.54 cm.

Microsoft Word for Windows is recommended as a

text editor. Choose Times New Roman fonts, and

single spaced lines. Font sizes should be: 18 pt bold

for the paper title, 12 pt for the author(s), 9 pt bold for

the abstract and keywords, 10 pt capitals for the

section titles, 10 pt italic for the subsection titles;

distance between section numbers and titles should be

of 0.25 cm; use 10 pt for the normal text, 8 pt for

affiliation, footnotes, figure captions, and references.

III. FIGURES AND TABLES

Figures should be centered, and tables should be left

aligned, and should be placed after the first reference

in the text. Use abbreviations such as “Fig.1.” even at

the beginning of the sentence. Leave an empty line

before and after equations. Equation numbering

should be simple: (1), (2), (3) … and right aligned:

∫−

−=

a

adtytx ττ )()( . (1)

IV. ABOUT REFERENCES

References should be numbered in a simple form [1],

[2], [3]…, and quoted accordingly [1]. References are

not allowed in footnotes. It is recommended to

mention all authors; “et al.” should be used only for

more than 6 authors.

Table 1

Parameter Value Unit

I 2.4 A

U 10.0 V

V. REMARKS

A. Abbreviations and acronyms

Abbreviations and acronyms should be explained

when they appear for the first time in the text.

Abbreviations such as IEEE, IEE, SI, MKS, CGS, ac,

dc and rms need no further explanation. It is

recommended not to use abbreviations in section or

subsection titles.

Fig. 1. Amplitudes in the standing wave

32

B. Further recommendations

The International System of units is recommended.

Do not mix SI and CGS. Preliminary, experimental

results are not accepted. Roman section numbering is

optional.

REFERENCES

[1] A. Ignea, “Preparation of papers for the International

Symposium Etc. ’98”, Buletinul Universităţii “Politehnica”, Seria

Electrotehnica, Electronica si Telecomunicatii, Tom 43 (57), 1998,

Fascicola 1, 1998, pp. 81.

[2] R. E. Collin, Foundations for Microwave Engineering, Second

Edition, McGraw-Hill, Inc., 1992.

[3] http://www.tc.etc.upt.ro/bulletin

33

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