AIRCOM Asset LTE Basics and Asset

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© 2012 AIRCOM International Ltd

Section 1: LTE Air-Interface Instructor – Ishan Marwah

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Roadmap

GSM

EDGE

WCDMA

2G 2.5G 3G phase 1

GPRS

Evolved 3G

HSDPA

HSUPA*

2000/2001 2003/2004 2005 2007

LTE

2010

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Where are we?

LTE is now on the market (both radio and core network evolution)

Release 8 was frozen in December 2008 and this has been the basis for the first wave of LTE equipment

Enhancements to LTE were frozen in to release 9 in December 2009

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Flat Architecture Traditional

Architecture

Control plane

User plane

GGSN

SGSN

RNC

NODE B

One Tunnel

Architecture

REL7

GGSN

SGSN

RNC

NODE B

SAE /GW– System

Architecture Evolution

MME - Mobility

Management Entity

eNodeB - evolved Node B

LTE

SAE GW

MME

eNODEB

IP Network

IP Network

IP Network

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LTE-UE

Evolved UTRAN (E-UTRAN)

MME

S6a

Serving

Gateway

S1-U

S11

Evolved Packet Core (EPC)

S1-MME

PDN

Gateway

IMS

PCRF

S7

S5

Evolved

Node B

(eNB)

X2

LTE-Uu

HSS

MME: Mobility Management Entity

Policy & Charging

Rule Function

LTE Network Architecture

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Release 8– LTE – New Air interface The LTE DOWNLINK uses OFDMA

Orthogonal Frequency Division Multiple Access

This new OFDMA based air interface is also often referred to as the

Evolved UMTS Terrestrial Radio Access Network (EUTRAN)

300 Mbit/s per 20 MHz of spectrum

Uplink

uses Single Carrier Frequency Division Multiple Access (SC-FDMA)

Single Carrier Frequency means information is modulated only to one carrier, adjusting the phase or amplitude of the carrier or both

75 Mbit/s per 20 MHz of spectrum

OFDMA

SC-FDMA

eNODE B

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The Physical Layer - OFDM and OFDMA

Orthogonal Frequency Division Multiplexing

Each user is

assigned a

specific

frequency

resource

Orthogonal Frequency Division Multiple Access

Each user is

assigned a

specific time-

frequency

resource

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Multiple Access DL

LTE employs OFDM as the basic modulation scheme and multiple access is achieved through:

• OFDMA in the LTE Downlink

• A multi-carrier signal with one data symbol per subcarrier

• Scalable to wider bandwidths, multipath resilient and better suited for MIMO architecture

• Drawback: Parallel transmission of multiple symbols creates undesirable high PAPR

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Multiple Access UL SC-OFDMA in the LTE Uplink

• SC-FDMA transmits the four QPSK data symbols from a user in series at four times the rate, with each data symbol occupying N x 15 kHz bandwidth.

• Signal more like single carrier with each data symbol being represented by one wide symbol

• Occupied bandwidth same as OFDMA but crucially, the PAPR is the same as that used for original data symbol

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Advanced Antenna Techniques

• MIMO needs a high signal-to-noise ratio (SNR) at the UE

• High SNR ensures that the UE is able to decode the incoming signal

• This ensures good orthogonality

Use multiple channels to send

multiple information streams

(spatial multiplexing)

• Increase throughput

MIMO creates multiple parallel

channels between transmitter and

receiver. MIMO is using time and space

to transmit data (space time coding).

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LTE - FDD/TDD

There are two types of LTE frame structure:

Type 1: used for the LTE FDD mode systems. Type 2: used for the LTE TDD systems.

LTE can be used in both paired (FDD) and unpaired (TDD)

spectrum. FDD & TDD supports bandwidths from 1.4 Mhz to 20Mhz

FDD

F -DL

F -UL

TDD

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FDD Type 1 used for the LTE FDD mode systems.

The basic type 1 LTE frame has an overall length of 10 ms. This is then divided into a total of 20 individual slots. LTE Subframes then consist of two slots - in other words there are ten LTE subframes within a frame.

0 1 2 3 19

One Sub-

frame = 1 mS

10 ms

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TDD Type 2 LTE Frame Structure

The frame structure for the type 2 frames used on LTE TDD is somewhat different. The 10 ms frame comprises two half frames, each 5 ms long. The LTE half-frames are further split into five subframes, each 1ms long.

10 ms

0 2 3 4 0 1 2 3 4

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TDD

The special subframes consist of the three fields:

DwPTS (Downlink Pilot Timeslot) GP (Guard Period) UpPTS (Uplink Pilot Timeslot)

One radio frame Tf =10 ms

One half- frame Thf = 5 ms

Sub-frame

#0

Sub-frame

#2

Sub-frame

#3

Sub-frame

#4

DwPTS

GP

UpPTS

Sub-frame

#5

Sub-frame

#7

Sub-frame

#8

Sub-frame

#9

DwPTS

GP

UpPTS

special sub-fames

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TDD A total of seven up / downlink

configurations have been set, and these use either 5 ms or 10 ms switch periodicities.

“S” denotes the special subframe when you go from DL to U

The special subframes consist of the three fields: DwPTS (Downlink Pilot Timeslot), GP (Guard Period), and UpPTS (Uplink Pilot Timeslot)

0 1 2 3 19

10 ms

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Flexible Carrier Bandwidths

LTE is defined to support flexible carrier bandwidths from 1.4MHz up to 20MHz, in many spectrum bands and for both FDD and TDD deployments

Supported LTE modes of operation:

Frequency Division Duplex (FDD)

Time Division Duplex (TDD)

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Supported Channels (non-overlapping) E-UTRA

Band Downlink

Bandwidth Channel Bandwidth (MHZ)

1.4 3 5 10 15 20

1 60 - - 12 6 4 3 2 60 42 20 12 6 4* 3* 3 75 53 23 15 7 5* 3* 4 45 32 15 9 4 3 2 5 25 17 8 5 2* - - 6 10 - - 2 1* X X 7 70 - - 14 7 4 3* 8 35 25 11 7 3* - - 9 35 - - 7 3 2* 1*

10 60 - - 12 6 4 3 11 25 - - 5 2* 1* 1* 12 18 12 6 3* 1* - X 13 10 7 3 2* 1* X X 14 10 7 3 2* 1* X X ... 33 20 - - 4 2 1 1 34 15 - - 3 1 1 X 35 60 42 20 12 6 4 3 36 60 42 20 12 6 4 3 37 20 - - 4 2 1 1 38 50 - - 10 5 - - 39 40 - - 8 4 3 2 40 100 - - - 10 6 5

* UE receiver sensitivity can be relaxed X Channel bandwidth too wide for the band - Not supported

E-UTRA Bands and Channel Bandwidths E-UTRA bands are regulated to allow

operations in only certain set of Channel Bandwidths which are defined as

The RF bandwidth supporting a single E-UTRA RF carrier with the transmission bandwidth configured in the uplink or downlink of a cell

Channel bandwidth is measured in MHz and is used as a reference for transmitter and receiver RF requirements

Some EUTRA bands do not allow operation in the narrow bandwidth modes , i.e. < 5 MHz

Others restrict operations in the wider channel bandwidths, i.e. > 15 MHz

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LTE Bands

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Comparison FDD/TDD 1. FDD LTE uses frequency division, while TDD LTE uses

time division

2. FDD LTE is full duplex, while TDD LTE is half duplex

3. FDD LTE is better for symmetric traffic, while TDD is better for asymmetric traffic

4. FDD LTE allows for easier planning than TDD LTE

FDD base stations use different frequencies for receiving and transmitting, they effectively do not hear each other and no special planning is needed. With TDD, special considerations need to be taken in order to prevent neighbouring base stations from interfering with each other

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Sub-Carriers

15Khz Spacing saving

bandwidth. 12 carriers

for 0.5ms

7.5Khz Spacing saving

bandwidth. 24

subcarriers for 0.5 ms.

200Khz

GSM

LTE b0 b1

QPSK

Im

Re 10

11

00

01

b0 b1b2b3

16QAM

Im

Re

0000

1111

Im

Re

64QAM

b0 b1b2b3 b4 b5

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Slot Structure and Physical Resources ONE slot = 12 consecutive

subcarriers

One slot = 0.5mS

6 or 7 OFDM symbols (depending upon cyclic perfix size), thus a single resource block is containing either 72 or 84 OFDM symbols

12x 7 = 84 OFDM symbols

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b0 b1

QPSK

Im

Re 10

11

00

01

b0 b1b2b3

16QAM

Im

Re

0000

1111

Im

Re

64QAM

b0 b1b2b3 b4 b5

One Slot = 0.5mS

Slot Structure and Physical Resources

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R

B

R

B

R

B

R

B

R

B

R

B

R

B

R

B

R

B

R

B

R

B

R

B

R

B

BW config

BW Channel

CHANNEL BW (Mhz)

Nrb BW config= Nrb x 12 x15 1000

% of Channel BW

1.4 6 1.08 77%

3 15 2.7 90%

5 25 4.5 90%

10 50 9 90%

15 75 13.5 90%

20 100 18.0 90%

Channel BW

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Bandwidth (MHz)

1.4 3 5 10 15 20

# of RBs 6 15 25 50 75 100

Subcarriers 72 180 300 600 900 1200


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Cyclic Prefix In the time domain, a guard interval may be added to each symbol to combat

inter-OFDM-symbol-interference due to channel delay spread

The guard interval is a cyclic prefix which is inserted prior to each OFDM symbol

One Slot = 0.5ms

One sub Frame=1mS

7 OFDM Symbols

All Data 7 OFDM Symbols

cyclic prefix

The length of the cyclic prefix, CP is important. If it is not long enough then it will not counteract the multipath reflection delay spread. If it is too long, then it will reduce the data throughput capacity.

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Direct signal

Reflection 1

Last Reflection

Guard

Period

Sampling Window

2

Time Domain

1

3

Normal For LTE, the standard length of the cyclic prefix has been chosen to be 4.69 µs. This enables the system to accommodate path variations of up to 1.4 km. With the symbol length in LTE set to 66.7 µs

Delay Spread

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Cyclic Prefix To each OFDM symbol, a cyclic prefix (CP) is appended as guard time

One downlink slot consists of 6 or 7 OFDM symbols, depending on whether extended or normal cyclic prefix is configured, respectively

The extended cyclic prefix is able to cover larger cell sizes with higher delay spread of the radio channel

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Each 1ms Transmission Time Interval (TTI) consists of two slots (Tslot)

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OFDMA and Throughputs

15kHz To symbol rate of 1/15KHz = 66.7us

Therefore 15 Kilosymbols per second

For 20Mhz bandwidth (1200 carriers)

symbol rate = 1200 x 15= 18Msps

Each symbol using 64 QAM (6 bits)

Total peak rate =

18 Msps x 6 bits = 108Mbps

Subtract overhead and coding and add

gains (MIMO)

66.7us

Each symbol

2 bits(QPSK), 4 Bits (16 QAM)

and 6 bits 64 QAM

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Downlink Reference Signal Structure

PDSCH

Downlink reference signal

RSRP (Reference Signal Received Power)

RSRP is a RSSI type of measurement. It measures the average received power over the resource elements that carry cell-specific reference signals within certain frequency bandwidth.

RSRP is applicable in both RRC_idle and RRC_connected modes

Downlink reference signal structure The downlink reference signal structure is important for channel estimation. The principle of the downlink reference signal structure for 1 antenna. Ref Signal TX1= 8 for 15Khz spacing

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Configuration of Carrier Note that when multiple antennas are used for transmission, then

there is a resource grid for each one.

EUTRAN support 1, 2 or 4 antennas, called the antenna ports

R0

R0

R0 R0

R0

R0

R0

R0

R0

R0

R0 R0

R0

R0

R0

R0

R0

R0

R0 R0

R0

R0

R0

R0

R0

R0

R0 R0

R0

R0

R0

R0

Port 1

Port 4

Port 3

Port 2

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Configuration of Carrier - 1 Antenna

Carrier 1

Overhead REF, Control, Broadcast, Syn

Downlink Reference Signal Structure The downlink reference signal structure is important for channel estimation. The principle of the downlink reference signal structure for 1 antenna. Ref Signal TX1 = 8 for 15Khz spacing

R0

R0

R0 R0

R0

R0

R0

R0

Specific pre-defined resource elements (indicated by R0-3 in in the time-frequency domain are carrying the cell-specific reference signal sequence.

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Carrier 1



The downlink reference signal structure is important for channel estimation.

The principle of the downlink reference signal structure for 2 antenna.

Ref Signal TX2= 16 for 15Khz spacing

R0

R0

R0 R0

R0

R0

R0

R0

R1 R1

R1

R1 R1

R1 R1

R1


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Carrier 1



The downlink reference signal structure is important for channel estimation.

The principle of the downlink reference signal structure for 2 antenna.

Ref Signal TX3= 20 for 15Khz spacing

R0

R0

R0 R0

R0

R0

R0

R0

R1 R1

R1

R1 R1

R1 R1

R1

R2

R2

R2

R2


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Carrier 1


Downlink reference signal structure The downlink reference signal structure is important for channel estimation. The principle of the downlink reference signal structure for 2 antenna. Ref Signal TX3= 20 for 15Khz spacing

R0

R0

R0 R0

R0

R0

R0

R0

R1 R1

R1

R1 R1

R1 R1

R1

R2

R2

R2

R2

R3

R3

R3

R3


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Type1-DL Frame

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FDD Frame Structures UL

Type1-FDD- Uplink

UL Control Channel

• PUCCH transmission in one subframe is compromised of single PRB at or near one edge of the system bandwidth followed by a second PRB at or near the opposite edge of the bandwidth

• PUCCH regions depends on the system bandwidth. Typical values are 1, 2, 4, 8 and 16 for 1.4, 3, 5, 10 and 20 MHz

UL Signals(S-RS & DM RS)

• S-RS estimates the channel quality required for the UL frequency-selective scheduling and transmitted on 1 symbol in each subframe

• DM-RS is associated with the transmission of UL data on the PUSCH and\or control signalling on the PUCCH

• mainly used for channel estimation for coherent demodulation

• transmitted on 2 symbols in each subframe

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Type1- UL Frame

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RSRQ is defined as the ratio N×RSRP / (E-UTRA carrier RSSI)

RSRP is applicable RRC connected modes

LTE_ACTIVE state

RSRQ (Reference Signal Received Quality)

In LTE network, a UE measures: RSRQ (Reference Signal Received Quality)

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Frequency Band Considerations Fifteen FDD band options and eight TDD band

The specific spectrum availability will depend on the country and region in

which the network will operate.

An operator may already have licensed spectrum available in which LTE could be rolled out. This may be because an older legacy technology can be progressively switched off, or because they have spectrum that is currently unused

Given the possible expense of purchasing new radio licences, most operators will at least consider the possibility of refarming their existing licensed spectrum for LTE use.

In most cases, however, an operator will need to consider purchasing new spectrum in which to operate LTE. Even when new spectrum is available, an operator will need to consider a number of configuration options.

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Propagation (Path Loss) Models A propagation model describes the average signal propagation, and it converts the maximum allowed propagation loss to the maximum cell range.

It depends on:

• Environment : urban, rural, dense urban, suburban, open, forest, sea…

• Frequency

• atmospheric conditions

• Indoor/outdoor

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Free Space Path Loss

For typical radio applications, it is common to find measured in units of MHz and in km, in which case the FSPL equation becomes:

Free-Space Path Loss (FSPL) is the loss in signal strength of an

electromagnetic wave that would result from a line-of-site path through free space, with no obstacles nearby to cause reflection or diffraction.

FSPL= 32.5 + 20 log10(d) + 20 log10(f) dBm

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Free Space Path Loss Formula at 1800Mhz

Lo = 32.5 + 20 log(d) + 20 log(fMhz) dBm

What is the free space

path loss at:

1800Mhz at 1Km

20 log (1) + 20logx1800

=0 +65

=32.5 + 65 dB

=97.5


path loss at:

1800Mhz at 10Km

20 log (10) + 20log1800

=20 +65

=32.5+85dB

=117.5


path loss at:

1800Mhz at 100Km

20 log (100) + 20log10x1800

=40 +65

=32.5+105dB

=137

20dB different

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Free Space Path Loss Formula at 900Mhz: Lo = 32.5 + 20 log10(d) + 20 log10(fMhz) dBm


path loss at:

900Mhz at 1Km

20 log (1) + 20log x 900

=0 + 59

=32.5 + 59dB

=91.5dB


path loss at:

900Mhz at 10Km

20 log (10) + 20log x 900

=20 +59

=32.5+79dB

=111.5dB


path loss at:

900Mhz at 100Km

20 log (100) + 20log10x900

=40 +59

=32.5+99dB

=131.5

20dB different

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Examples What is the free space

path loss at:

1800Mhz at 1Km

20 log (1) + 20logx1800

=0 +65

=32.5 + 65 dB

=97.5


path loss at:

1800Mhz at 10Km

20 log (10) + 20log1800

=20 +65

=32.5+85dB

=117.5


path loss at:

1800Mhz at 100Km

20 log (100) + 20log10x1800

=40 +65

=32.5+105dB

=137


path loss at:

900Mhz at 1Km

20 log (1) + 20log x 900

=0 + 59

=32.5 + 59dB

=91.5dB


path loss at:

900Mhz at 10Km

20 log (10) + 20log x 900

=20 +59

=32.5+79dB

=111.5dB


path loss at:

900Mhz at 100Km

20 log (100) + 20log10x900

=40 +59

=32.5+99dB

=131.5

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Frequency Band Considerations The frequency ranges covered by the

defined operating bands for LTE vary greatly and include bands based around 700 MHz up to bands around 2.6 GHz.

The band makes a significant difference to the number of sites required for network rollout.

11.4 dB difference in free space path loss between 700 MHz and 2.6 GHz.

700

MHz

At 700 MHz could be between three and four times larger than at 2.6 GHz.

2.6 GHz

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Frequency Band Considerations 700 MHz

• In the U.S. this commercial spectrum is scheduled to be auctioned in

January 2008

• This includes 62 MHz of spectrum broken into 4 blocks:

• A (12 MHz) • B (12 MHz) • E (6 MHz unpaired) • C (22 MHz) • D (10 MHz)

• These bands are highly prized chunks of spectrum and a tremendous

resource: the low frequency is efficient and will allow for a network that doesn’t require a dense build out and provides better in-building penetration than higher frequency bands.

48


Frequency Band Considerations Refarming GSM 900 MHz

900MHz offers improved building penetration and is particularly well suited to

supporting those regions that have a predominantly rural population.

The ongoing subscriber migration from GSM to UMTS taking place in over 150 countries worldwide is relieving pressure on the GSM900 networks and is starting to free up some spectrum capacity in that band.

Deploying LTE in 900MHz can also bring the additional cost and logistic benefits of being able to deploy LTE at existing GSM sites as the coverage of GSM/LTE in 900MHz should be very similar.

Compared to HSDPA/HSDPA+, LTE is expected to substantially improve end-user throughputs, sector capacity and reduce user plane latency to deliver a significantly improved user experience. As such, the industry expects that Service Providers will wait to deploy LTE in the refarmed 900 MHz

49


Frequency Band Considerations

Frequency Planning

How much spectrum an operator may have access to. Historically, radio

licences for 20 MHz,either TDD or FDD, have been rare.

Much more common would be 10–15 MHz. Additionally, it must be borne in mind that in most implementations some form of frequency plan must be used.

For example, an operator with a licence for 15 MHz may need to implement this as three 5 MHz channels.

It is possible to implement LTE as an SFN (Single Frequency Network), but the high level of interference at cell edges reduces the available bandwidth unless Interference Management Systems are used.

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Questions

51


Questions

1. What is the maximum bit rate if you assign a bandwidth of 10Mhz to a sector and a UE is allocated all RB?

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Questions


53


Questions


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Questions

4. What is meant by Normal type1?

5. Compare band 13 to band 1?

6. What is meant by GSM re-farming?

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Session 02

Setting up a LTE Network in Asset

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Antenna Database

Antenna Information and Mask

57


Setting up a Propagation Model

Propagation models are mathematical attempts to model the real radio environment as closely as possible. Most propagation models need to be tuned (calibrated) by being compared to measured propagation data, otherwise you will not be able to obtain accurate coverage predictions.

58


Std. Macrocell Propagation Model

Asset Standard Macrocell model

lossClutterlossndiffractioKdoglHgloK

gHloKogHlKHKdoglKKPL

eff

effmsms

)(7)()(6

543)(21

59


Recommended Starting Parameters K values 450 MHz 900 MHz 1800 MHz 2000 MHz 2500 MHz 3500 MHz

k1 for LOS 142.3 150.6 160.9 162.5 164.1 167

k2 for LOS 44.9 44.9 44.9 44.9 44.9 44.9

k1 (near) for LOS

129.00 0.00 0.00 0.00 0.00 0.00

k2 (near) for LOS

31.00 0.00 0.00 0.00 0.00 0.00

d < for LOS 0.00 0.00 0.00 0.00 0.00 0.00

k1 for NLOS 142.3 150.6 160.9 162.5 164.1 167

k2 for NLOS 44.9 44.9 44.9 44.9 44.9 44.9

k1 (near) for NLOS

129.00 0.00 0.00 0.00 0.00 0.00

k2 (near) for NLOS

31.00 0.00 0.00 0.00 0.00 0.00

d < for NLOS 0.00 0.00 0.00 0.00 0.00 0.00

k3 -2.22 -2.55 -2.88 -2.93 -3.04 -3.20

k4 -0.8 0.00 0.00 0.00 0.00 0.00

k5 -11.70 -13.82 -13.82 -13.82 -13.82 -13.82

k6 -4.30 -6.55 -6.55 -6.55 -6.55 -6.55

k7 0.4 0.7 0.8 0.8 0.8 0.8

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MME and SAE-GW Support

Asset support for hieratically higher LTE network elements

Mobility Management Entity (MME)

System Architecture Evolution Gate Way (SAE-GW)

Support for Logical/Cellular Connections that allow

for the mesh-type parent-child relationships of the

LTE Core.

eNodeB can be parented to both an SAEGW and

MME and can be parented to multiple SAEGWs and/or MMEs

61


MME and SAE-GW Support

62


LTE Frame Structures

63


LTE Frequency Bands

64


LTE Carriers

65


LTE Carriers

66


Interference Co-ordination Schemes

To minimize Intercell Interference following frequency reuse schemes are being considered

Frequency Reuse-1 with Prioritization

• Each sector divides the available bandwidth into prioritized (one third) and non-prioritized (two third) sections disregard of CE or CC.

• Prioritized spectrum is used more often than non-prioritized by each sector in order to concentrate the interference that it causes to other sectors

67


Interference Co-ordination Schemes Soft Frequency Reuse

• Power difference between the prioritized and non-prioritized spectrum which divides the sector into an inner and an outer region

• User in the inner region can be reached with reduced power, i.e. Cell Centre Users (CCU) than the users in the outer region i.e. Cell Edge Users (CEU)

• CCU are assigned frequency Reuse-1 while CEU employ Reuse-3 with soft reuse

68


Interference Coordination Schemes Reuse Partitioning

• Similar to Soft Frequency Reuse

• High-power part is divided between sectors so that each sector gets one third of the high-power spectrum

• Low-power part employs frequency Reuse-1 while high-power part is configured with a frequency Reuse-3 with hard reuse.

69


Interference Coordination Schemes

70


MIMO - Transmit Diversity

Instead of increasing data rate or capacity, MIMO can be used to exploit

diversity and increase the robustness of data transmission.

Each transmit antenna transmits essentially the same stream of data, so the

receiver gets replicas of the same signal.

T

X

R

X 010100

010100

010100

SU-MIMO

71


MIMO - Spatial Multiplexing

010

T

X

R

X 010100

100

SU-MIMO

Spatial multiplexing allows an increase in the peak rates by a factor of 2 or 4,

depending on the eNodeB and the UE antenna configuration.

Spatial multiplexing allows to transmit different streams of data, different

reference symbols simultaneously on the same resource blocks

72


LTE Downlink Transmission Modes

• LTE Rel 8 supports DLtransmission on 1, 2, or 4 antenna ports:

• 1, 2, or 4 cell-specific reference signals

• each reference signal corresponds to one antenna port

• DL transmission modes are defined for PDSCH (Data\Traffic)

• Single antenna (No MIMO)

• Transmit diversity

• Open loop Spatial multiplexing

• Closed loop spatial multiplexing

• Multi user MIMO

• Closed-loop precoding for Rank=1 (No spatial Mux, But precode)

• Conventional beamforming

• UL MIMO Modes

• Transmit diversity

• Receive Diversity

• MU-MIMO

SU-MIMO

73


SU-MIMO

• This includes conventional techniques such as

• Cyclic Delay Diversity

• Transmit\Receive diversity (Space frequency block codes)

• Spatial Multiplexing\ Precoded Spatial Multiplexing

• Can be implemented as Open and Closed loop

• Diversity techniques improves the signal to interference ratio by transmitting same stream of single user data.

• Spatial multiplexing increases the per user data rate\throughput by transmitting multiple streams of data dedicated for a single user

74


MU-MIMO

• Multiple users (separated in the spatial domain in both UL and DL) sharing the same time-frequency resources

• Uses multiple narrow beams to separate users in the spatial domain and can be considered as a hybrid of beamforming and spatial multiplexing.

• Serves more terminals by scheduling multiple terminals using the same resources

• this increases the cell capacity and number of served terminals

• Suitable for highly loaded cells and for scenarios where number of served terminals is more important than peak user data rates

75


Lookup Table for AAS

76


Templates for Sites When planning a network, Instead of setting the parameter values on each node individually, you can define templates, then select one of these templates as a basis for adding new nodes. The new nodes will then contain the default characteristics of the template.

77


Adding Sites/Cells

You can add network elements by using the site design toolbar in the Map View window and also by using the Site Database window.

You need the correct privileges to be able to add and modify network elements. Contact your administrator if you do not have the correct permissions

78


AAS Settings in Site DB

79


LTE Parameters

80


Scheduler Scheduler Description

Round Robin The aim of this Scheduler is to share the available/unused resources equally among the terminals

(that are requesting RT services) in order to satisfy their RT-MBR demand.

This is a recursive algorithm and continues to share resources equally among terminals, until all RT-

MBR demands have been met or there are no more resources left to allocate.

Proportional

Fair

The aim of this Scheduler is to allocate the available/unused resources as fairly as possible in such a

way that, on average, each terminal gets the highest possible throughput achievable under the

channel conditions.

This is a recursive algorithm. The available/unused resources are shared between the RT terminals in

proportion to the bearer data rates of the terminals. Terminals with higher data rates get a larger

share of the available resources. Each terminal gets either the resources it needs to satisfy its RT-

MBR demand, or its weighted portion of the available/unused resources, whichever is smaller. This

recursive allocation process continues until all RT-MBR demands have been met or there are no more

resources left to allocate.

Proportional

Demand

The aim of this Scheduler is to allocate the available/unused resources in proportion to the RT-MBR

demand, which means that terminals with higher RT-MBR demand achieve higher throughputs than

terminals with lower RT-MBR demand. This is a non-recursive resource allocation process and results

in either satisfying the RT-MBR demands of all terminals or the consumption of all of the

available/unused resources.

Max SINR The aim of this Scheduler is to maximise the terminal throughput and in turn the average cell

throughput. This is a non-recursive resource allocation process where terminals with higher bearer

rates (and consequently higher SINR) are preferred over terminals with low bearer rates (and

consequently lower SINR). This means that resources are allocated first to those terminals with better

SINR/channel conditions than others, thereby maximising the throughput.

81


LTE Parameters Load (%) Interference

Margin (dB)

35 1

40 1.3

50 1.8

60 2.4

70 2.9

80 3.3

90 3.7

100 4.2

82


Session 03

Predicting and Displaying Coverage

83


Predicting Coverage

84


Best RSRP Coverage Example

85


Array Display Properties To customise the arrays displayed in the Map View window, Use the Show Data Types button.

86


Coverage Reports/Statistics

Once coverage arrays have been created, you can generate coverage statistics.

87


Coverage Reports/Statistics

88


Array Manager

Array manager enable memory management on arrays and simulations. In addition, the Array Manager provides the ability to retrieve archived arrays, allowing for the benchmarking of statistical changes over time.

89


Session 04

Traffic Planning on a LTE Network

90


Default LTE Bearers Bearers represent the air interface connections, performing the task of transporting voice and data information between cells and terminal types.

91


Channel Quality Indicator Tables

Indicates a combination of modulation and coding scheme that the NodeB should use to ensure that the BLER experienced by the UE remains < 10%

eNB

UE1

UE2

UE3

UE4

UE5

64 QAM 16 QAM QPSK

CQI

Modulation Efficiency Actual coding rate

Required SINR

1 QPSK 0.1523 0.07618 -4.46

2 QPSK 0.2344 0.11719 -3.75

3 QPSK 0.3770 0.18848 -2.55

4 QPSK 0.6016 308/1024 -1.15

5 QPSK 0.8770 449/1024 1.75

6 QPSK 1.1758 602/1024 3.65

7 16QAM 1.4766 378/1024 5.2

8 16QAM 1.9141 490/1024 6.1

9 16QAM 2.4063 616/1024 7.55

10 64QAM 2.7305 466/1024 10.85

11 64QAM 3.3223 567/1024 11.55

12 64QAM 3.9023 666/1024 12.75

13 64QAM 4.5234 772/1024 14.55

14 64QAM 5.1152 873/1024 18.15

15 64QAM 5.5547 948/1024 19.25

92


LTE Services The parameters that you specify will influence how the simulation behaves and will enable you to examine coverage and service quality for individual types of service.

93


LTE Services and QoS Parameters

Name QCI Resource

Type

Priority

Packet Delay

Budget

Packet Error

Loss Rate

Example Services

VoIP 1 GBR 2 100 ms 10-2 Conversational Voice

Video Call 2 GBR 4 150 ms 10-3 Conversational Video (Live Streaming)

Gaming 3 GBR 3 50 ms 10-3 Real Time Gaming

Streaming 4 GBR 5 300 ms 10-6 Non-Convers.Video (Buff. Streaming)

Signalling 5 Non-GBR 1 100 ms 10-6 IMS Signalling

E-mail 6 Non-GBR 6 300 ms 10-6 Video (Buffered Streaming), TCP-based (www, e-mail, chat,

ftp, p2p sharing, Progressive video, etc.)

Voice, Video (Live Streaming) Interactive Gaming

Web browsing

7 Non-GBR 6 100 ms 10-3

P2P File Sharing

8 Non-GBR 8 300 ms 10-6

Chat 9 Non-GBR 9 300 ms 10-6

94


Clutter Parameters

You can define different shadow fading standard deviations for outdoor terminals and indoor terminals per clutter type. If a building is in urban, it will encounter greater fading than in parkland.

You can also specify different indoor losses for each clutter type.

95


Terminal Types

ASSET models traffic demand by generating traffic density maps for the different types of terminal. These density maps define the amount of traffic offered to the network by each type of terminal on a pixel-by-pixel basis, corresponding to the available clutter map data resolutions.

A Terminal Type in ASSET defines these key characteristics:

How much ‘traffic’ will the terminal type generate in total?

How will the ‘traffic’ be spread geographically?

What is the expected mobile speed distribution for this terminal type?

Which service will the terminal type provide?*

What are the mobile equipment characteristics?

96


LTE Terminal Types

97


LTE User Equipment Categories

Parameters Category 1 Category 2 Category 3 Category 4 Category 5

Peak Data Rate (DL) 10 Mbps 50 Mbps 100 Mbps 150 Mbps 300 Mbps

Peak Data Rate (UL) 5 Mbps 25 Mbps 50 Mbps 50 Mbps 75 Mbps

Block Size (DL) 10296 51024 102048 149776 299552

Block Size (UL) 5160 25456 51024 51024 75376

Max. Modulation (DL) 64QAM 64QAM 64QAM 64QAM 64QAM

Max. Modulation (UL) 16QAM 16QAM 16QAM 16QAM 64QAM

RF Bandwidth 20 MHz 20 MHz 20 MHz 20 MHz 20 MHz

Transmit Diversity 1-4 Tx 1-4 Tx 1-4 Tx 1-4 Tx 1-4 Tx

Receive Diversity Yes Yes Yes Yes Yes

Spatial Multiplexing (DL) Optional 2 X 2 2 X 2 2 X 2 4 X 4

Spatial Multiplexing (UL) No No No No No

MU-MIMO (DL) Optional Optional Optional Optional Optional

MU-MIMO (UL) Optional Optional Optional Optional Optional

98


Traffic Rasters

Traffic Rasters are arrays that store the distribution of traffic over an area. They can be created either from the information in the Terminal Types or from imported Live Traffic values. The name of the created traffic raster will be the same as the name of the terminal type.

The Traffic Rasters enables you to:

Obtain initial estimates of the equipment and configuration needed for a nominal network. By visualising the array, you can then gain a good idea of where to locate your sites.

Can assess how your network performs in terms of capacity for a mature network. Can verify site configuration is sufficient to match the traffic spread over the network.

99


Creating Traffic Rasters

100


Traffic Rasters

101


Session 5

Simulating Network Performance

102


LTE Simulator Wizard

103


Simulation without Snapshots

If you run a simulation without running snapshots (static analysis) you must ensure that the cell loading parameters for the cells/sectors have been specified in the Site Database. The parameters are set on the Cell Load Levels subtab under LTE Params tab.

104


Simulator Outputs

ASSET provides ways of setting your own array definitions, so that you can specify exactly which arrays you want to be output when you use the Simulator.

The easiest way is to use the Auto Setup option. This ensures that all the relevant array types and their parameter combinations are included in the simulation outputs for display and analysis.

You can also define your own customised collection of output array types from the Simulator. This enables you to specify array definitions to determine precisely which arrays you want to output and display, in any combination of parameters you choose. This method is probably only beneficial for advanced users.

105


Simulation – Best RSRP

106


Street Coverage prediction analysis using the Vector

Restriction feature

Best RSRP is calculated for whole 2D View Best RSRP is calculated to streets only

107


Simulation – RSRQ

108


Simulation – Cell Centre / Cell Edge

109


Simulation – Achievable DL Bearer

110


Simulation – DL RS SINR

111


Simulation – DL Transmission Mode

112


Information about Simulated Terminals

The aim of this feature is to provide the user with a set of arrays that show the locations of terminals generated by the simulation snapshots, and to show whether the terminals succeeded or failed to make a connection. The following arrays are provided for each terminal type used in the simulation.

• Terminal Info: Failure Rate

• Terminal Info: Failure Reason

• Terminal Info: Speed

The arrays are only available in simulations that run snapshots, and where the user has checked the Allow Terminal Info Arrays box on the 2nd page of the simulation wizard.

113


Information about Simulated Terminals

Failure Reason array. 1 snapshot

Failure Reason array. 500 snapshots

114


Line-of-Sight array and improved MIMO Modelling

AIRCOM Enhanced Macrocell model (as well as some 3rd party prediction models –

complete list TBD) have the ability to produce line-of-sight (LOS) information for each

predicted location, in addition to the existing pathloss value.

Using LOS info in a simulation can be used to improve MIMO modelling.

MIMO schemes rely on there being a low correlation between the signal paths to the

receive elements of an antenna. Locations that have line-of-sight to an antenna are

more likely to have high correlation between signal paths to the antenna.

The LTE simulator supports 3 basic MIMO schemes: SU-MIMO Multiplexing,

SU-MIMO Diversity, and MU-MIMO. A new page is added to the LTE simulation

wizard, providing the user with the option of enabling/disabling these 3 MIMO schemes

in LOS regions.

If a prediction model

is used that does not

generate LOS info,

then the sim will treat

pathlosses from that

model as non-LOS.

115


Line-of-Sight array and improved MIMO Modelling

116


Pixel Analyser The Pixel Analyser visualises detailed signal strength information that has been accumulated during a simulation.

117


Session 6

LTE Architecture

118


Flat Architecture Traditional

Architecture

Control plane

User plane

GGSN

SGSN

RNC

NODE B

One Tunnel

Architecture

REL7

GGSN

SGSN

RNC

NODE B

SAE /GW– System

Architecture Evolution

MME - Mobility

Management Entity

eNodeB - evolved Node B

LTE

SAE GW

MME

eNODEB

IP Network

IP Network

IP Network

119


LTE-UE


MME

S6a

Serving

Gateway

S1-U

S11


S1-MME

PDN

Gateway

IMS

PCRF

S7

S5

Evolved

Node B

(eNB)

X2

LTE-Uu

HSS


Policy & Charging

Rule Function

LTE Network Architecture

120


Each eNB will have Physical Cell Identity (PCI). There are 504 different PCIs in

LTE. In addition, a globally unique cell identifier (GID)

Function of eNodeB

3GPP Release 8, the eNB supports the following functions:

Radio Resource Management

Radio Bearer Control

Scheduling (uplink and downlink )

Radio Admission Control

Connection Mobility Control

IP header compression and encryption of user data stream

Selection of an MME

Routing of User Plane data towards Serving Gateway

paging messages

121


Physical Cell Identity (PCI)

Non-unique. There are 504 different PCIs in LTE.

Mobile is required to measure the Reference Signal Received Power (RSRP) associated with a particular PCI.

It is important to detect and resolve local PCI conflicts.

PCI

PCI

Send Report

122


LTE-UE


MME

S6a

Serving

Gateway

S1-U

S11


S1-MME

PDN

Gateway

IMS

PCRF

S7

S5

Evolved

Node B

(eNB)

X2

LTE-Uu

HSS


Policy & Charging

Rule Function

EPS Bearer

The QoS parameters associated to the bearer are:

QCI, ARP, GBR and MBR

The QoS model in EPS is mostly based on DiffServ concepts

EPS Bearer in LTE

123


LTE Functional Elements - eNodeB

eNB eNodeB

Radio Resource Management

•Bearer & Admission control

•RF Measurement Reporting

Scheduling

•Dynamic resource allocation to UE’s

•Transmission of Pages & broadcast information

Network Access Security (PDCP)

• IP header compression

•Ciphering of user data stream

EPC Network Selection

•MME Selection at UE attachment

•User Plane routing to SAE-GW

Combines the functionality of the UMTS NodeB & RNC

124


LTE Functional Elements - MME

MME Mobility

Management Entity

EPC Access

•Attachment & Service Request

•Security & Authentication

Mobility

•MME Selection for Intra-LTE handovers

•SGSN Selection for 3GPP I-RAT Handover

UE Tracking and Reach-ability

•Tracking Area List Management (idle or active)

Bearer management

•Dedicated bearer establishment

•PDN GW & SAE-GW selection

Equivalent to the SGSN for the Control Plane

125


LTE Functional Elements – S-GW

S-GW SAE Gateway

Packet routing & forwarding

between EPC & eUTRAN

Local Mobility Anchor for Inter eNB handover

I-RAT Mobility Anchor Function

• 3GPP 2G/3G Handover

• Optimized Handover Procedures (e.g. in LTE-CDMA)

Lawful Interception

Equivalent to the SGSN for the User Plane

126


LTE Functional Elements – P-GW

P-GW PDN Gateway

UE IP address allocation

Policy enforcement

(QoS)

Charging support

Lawful Interception

Mobility Anchor between 3GPP & non-3GPP

access systems

Equivalent to the GGSN

127


Self Organising Networks (SON) The scope of Release 8 of SON:

Automatic inventory

Automatic software download

Automatic Neighbour Relation

Automatic Physical Cell ID (PCI) assignment

The next release of SON, as standardised in Release 9, will provide:

Coverage & Capacity Optimisation

Mobility optimisation

RACH optimisation

Load Balancing optimisation

128


Release 8 Data Rate: Peak data rates target 100 Mbps (downlink) and 50 Mbps (uplink) for 20 MHz spectrum allocation, assuming 2 receive antennas and 1 transmit antenna at the terminal

129


Release 8 Latency: The one-way transit time between a packet being

available at the IP layer in either the UE or radio access network and the availability of this packet at IP layer in the radio access network/UE shall be less than 5 ms

Also C-plane latency shall be reduced, e.g. to allow fast transition times of less than 100 ms from camped state to active state

130


Radio Resource Control (RRC)

RRC

Managing RRC connection

Mobility handling during RRC connected mode

Cell selection and re-selection

Interpreting broadcast system information

Managing radio bearers

Measurement reporting and control

Ciphering control

Signalling Radio Bearers (SRB)

Radio bearers are used only to carry the RRC and NAS messages

SRBs are divided into 3 types:

1. Signalling Radio Bearer 0: SRB0



FDD | TDD - Layer 1

( DL: OFDMA, UL: SC-FDMA )

Medium Access Control (MAC)

Transport Channels

RLC

(Radio Link

Control)

…

…

RLC

(Radio Link

Control)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

Logical Channel

(E-)RRC

(Radio Resource Control)

IP / TCP | UDP | …

Application Layer NAS Protocol(s)

(Attach/TA Update/…)

C plane signalling u plane Data

131



Admission

Control

Admission

Control

FDD | TDD - Layer 1



Transport Channels

RLC

(Radio Link

Control)

…

…

RLC

(Radio Link

Control)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

Logical Channel

(E-)RRC






132



The purpose of this procedure:

Establish/ Modify/ Release RBs

Perform Handover

Configure /modify measurements

FDD | TDD - Layer 1



Transport Channels

RLC

(Radio Link

Control)

…

…

RLC

(Radio Link

Control)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

Logical Channel

(E-)RRC






133




To re-establish the RRC connection

A UE in CONNECTED state in order to continue the RRC connection

This succeeds only if a valid context exists

FDD | TDD - Layer 1



Transport Channels

RLC

(Radio Link

Control)

…

…

RLC

(Radio Link

Control)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

Logical Channel

(E-)RRC






134




To activate security after the RRC connection establishment, using SRB1

FDD | TDD - Layer 1



Transport Channels

RLC

(Radio Link

Control)

…

…

RLC

(Radio Link

Control)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

Logical Channel

(E-)RRC






135



The purpose of this procedure is the release of:

SRB

EPS Bearers

ALL Radio resources

FDD | TDD - Layer 1



Transport Channels

RLC

(Radio Link

Control)

…

…

RLC

(Radio Link

Control)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

Logical Channel

(E-)RRC






136




To transmit paging information to UE in RRC IDLE State

To inform UE in RRC IDLE about system information change

SIBs

FDD | TDD - Layer 1



Transport Channels

RLC

(Radio Link

Control)

…

…

RLC

(Radio Link

Control)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

RLC

(Radio Link

Control)

PDCP

(Packet Data

Convergence

Protocol)

Logical Channel

(E-)RRC






137


Signalling Radio Bearer

Signalling Radio Bearers (SRB) are defined as Radio bearers that are used only to transmit RRC and NAS

Signalling Radio Bearer 0:

SRB0: RRC message using CCCH logical channel.

Signalling Radio Bearer 1: SRB1: is for transmitting NAS messages over DCCH logical channel.

Signalling Radio Bearer 2: SRB2: is for high priority RRC messages. Transmitted over DCCH logical channel

DTCH DCCH

Logical channels

DL-SCH

Transport

channels

Physical

channels

PDSCH

CCCH BCCH

138


Field Results from LTE Trial Objective: The purpose of the test is to validate that the EPS is able to pass ICMP packets to/from a test server under unloaded and loaded conditions using a 5 MHz x 5 MHz FDD channel bandwidth

Max RTT

(ms) Min RTT

(ms) Av RTT

(ms) PING Req

PING Res

PING Loss

Success Rate

PING NOLOAD

18 15 16.25 104 99 5 95.2%

PING LOAD 168 15 20.71 109 104 5 95.2%

139


What Tests Need to be Done?

Latency from UE to Server using a 5 MHz x 5 MHz FDD channel bandwidth

32 B 64 B 256 B 512 B 1024 B

EXC RTT 26.9 30.2 41.0 38.2 41.1

GOOD RTT 28.5 35.6 35.7 43.0 43.1

POOR RTT 28.1 35.2 51.5 59.4 155.1

0

20

40

60

80

100

120

140

160

180

RT

T (

ms

)

RTT vs Payload Size

140


Air Interface – Rel’99

IDLE

CELL DCH

QoS

CELL FACH

NO QoS

CELL URA CELLPCH

CELL SELECTION CELL SELECTION

CELL SELECTION

CELL SELECTION

141


UE States – LTE

RRC IDLE

RRC

CONNECTED

Handover

CELL SELECTION

This will reduce Latency Question: Will there be more handovers with LTE?

142


LTE Devices – UE Categories

143


3G Services and QoS Classes

Each application is different in nature

Some are high delay

Critical

Video Telephony

Streaming Video Radio Tuner

Computer Games Web Browsing

E-mail

Location Services

Server Backups

Casual

NRT

RT

INTEGRITY Telephony

Videotelephony

File downloading

Web browsing

Mail downloading

Calendar synchronisation

Teleworking

Teleshopping

Streaming video

Streaming music

UMTS

Telephony

144


Quality of Service

Traffic Class Conversational Streaming Interactive Background

Maximum Bit Rate X X X X

Delivery Order X X X X

Maximum SDU Size X X X X

SDU Format Information X X X X

SDU Error Ratio X X

Residual Bit Error Ratio X X X X

Delivery of Erroneous SDUs X X X X

Transfer Delay X X

Guaranteed Bit Rate X X

Traffic Handling Priority X

Allocation/Retention Priority X X

145


Services/Applications

Traffic Class Conversational Streaming Interactive Background

Speech X

Video Call X

Streaming Video X

Streaming Audio X

Web Browsing X

Email X

Email (Background) X

VoIP X

Gaming X

Presence X

146


LTE Quality of Service

147


LTE QoS

Allocation and Retention Priority (ARP): Within each QoS class there are different allocation and retention priorities

The primary purpose of ARP is to decide whether a bearer establishment / modification request can be accepted or needs to be rejected in case of resource limitations (typically available radio capacity in case of GBR bearers)

In addition, the ARP can be used (e.g. by the eNodeB) to decide which bearer(s) to drop during exceptional resource limitations (e.g. at handover)

148


Questions

1. Give a example of layer 4 protocol?

2. Give a example of layer 3 protocol?

3. What is the function of ARP?

4. What does QCI 1 mean?

149


Questions 5. How has Latency been reduced in LTE?

6. What is meant by 4x2?

7. What is meant by GSM re-farming?

8. What is a PCI?

9. Give some of the functions of SON for Rel’8?

10. What is EPS Bearer?

150


Session 7

LTE Mobility Management

151


Air Interface – Rel’99 / Rel 4

IDLE

CELL DCH

QoS

CELL FACH

NO QoS

CELL URA CELLPCH

152


LTE – Always On In the early deployment phase, LTE coverage will certainly be

restricted to city and hot spot areas.

MORE HO’s than Rel’99

LTE

Connected

LTE _IDLE

Cell DCH

Connected

Cell FACH

Cell URA

Cell PCH

IDLE GSM/GPRS

IDLE

GSM

Connected

GPRS

Packet Transfer

Handover Handover

Reselection

Connection Establishment/Release

Connection Establishment/Release

Connection

Establishment/Release

153


UE Power-up

UE Power up

DL Syn and Physical Channel ID

Find MIB – System BW

MCC +MNC

SIB’s supported

PCFICH Processing-

Knows the set up of PDCCH

Retrieval of SIBs

Cell Selection Parameters

Cell Selection

Successful Pre-amble / Attach

Yes

Acquire another

LTE Cell

PLMN ID matches

Cell Barred

After Attach –Defaulf

Bearer/IP adress

154


Cell Selection After a UE has selected a PLMN, it performs cell selection – in other

words, it searches for a suitable cell on which to camp

While camping on the chosen cell, the UE acquires the system information that is broadcast

Subsequently, the UE registers its presence in the tracking area, after which it can receive paging information which is used to notify UEs of incoming calls

eNB When camped on a cell, the UE regularly verifies if there is a better cell; this is known as performing cell reselection.

155


LTE-UE


MME

S6a

Serving

Gateway

S1-U

S11


S1-MME

PDN

Gateway

Internet

PCRF

S7

S5

Evolved

Node B

(eNB)

X2

LTE-Uu

HSS


EPS Mobility Management 2 states:

EMM-DEREGISTERED

EMM-REGISTERED

EPS Mobility Management

156


EPS Mobility Management - 2 States EMM-DEREGISTERED:

In this state the MME holds no valid location information about the UE

Successful Attach and Tracking Area Update (TAU) procedures lead to transition to EMM-REGISTERED

EMM-REGISTERED:

• In this state the MME holds location information for the UE at least to the accuracy of a tracking area

• In this state the UE performs TAU procedures, responds to paging messages and performs the service request procedure if there is uplink data to be sent

MME

MME

157


Tracking Area Update – IDLE

MME HSS

s6a

NAS: Tracking Area

update

LTE Non Access Stratum (NAS) The LTE NAS protocol software enables communication with the MME in the LTE core network and handles functions of mobility

Tracking Area Tracking Area

Home

Tracking Area Identity = MCC (Mobile Country Code), MNC (Mobile Network Code) and TAC (Tracking Area Code

158


Tracking Area Update – IDLE Tracking areas are allowed to overlap: one cell can belong to multiple tracking areas

TAI1-2

TAI2

TAI2

TAI2

TAI3

TAI3

TAI3

TAI3

TAI2

TAI2

TAI2

TAI2

TAI2

TAI2

TAI2

TAI2

TAI1

TAI1

TAI1

TAI1-2

NAS: Tracking Area

update

MME

159


MME

Serving

Gateway

S1-MME

(Control Plane)

S1-U

(User Plane)

NAS Protocols

S1-AP

SCTP

IP

L1/L2

User PDUs

GTP-U

UDP

IP

L1/L2

eNB

Tracking Area Update Request

S-TMSI/IMSI, PDN address

allocation Tracking Area Update Accept

Tracking Area Update Complete

LTE Functional Nodes - Management Entity (MME)

Tracking area (TA) is similar to Location/routing area in 2G/3G

Tracking Area Identity

MCC (Mobile Country Code) MNC (Mobile Network Code) TAC (Tracking Area Code)

160


The Globally Unique MME Identifier (GUMMEI) is constructed from the MCC, MNC and MME Identifier (MMEI).

Within the MME, the mobile is identified by the M-TMSI.

Globally Unique Temporary ID

MCC + MNC + MMEI GUMMEI

M-TMSI

MME

MME MME POOLING

Globally Unique Temporary ID

http://lte-epc.blogspot.co.uk/2009/11/knowing-guti-globally-unique-temporary.html

161


Context Request

Context Request A context request includes

old GUTI, complete TAU request, P-TMSI, MME address etc. Basically this message is sent by new MME to old MME to inquire about UE's authenticity, the bearers created if any etc.

Context Response

Context response include IMSI, EPS bearers context, SGW address and etc.

Create Session Request/Response: If there was no change in SGW there will not be this message.

162


RRC States – Idle OR Connected In the early deployment phase, LTE coverage will certainly be restricted to city and hot spot areas.

LTE

Connected

LTE _IDLE

Cell DCH

Connected

Cell FACH

Cell URA

Cell PCH

IDLE GSM/GPRS

IDLE

GSM

Connected

GPRS Packet

Transfer

Handover Handover

Cell Selection

/Reselection

Connection

Establishment/Release Connection

Establishment/Release

Connection

Establishment/

Release

163


Physical channels

20M

hz B

W

MIB

BW = 1.08Mhz

BCCH

BCH

PBCH

MIB

DL-SCH

PDSCH

Logical channels

Transport channels

RRC IDLE

164


The UE moving towards a new cell and identifies the Physical Cell Identity (PCI) based on the Synchronisation signals

Physical Cell Identity (PCI) = 504

P-SCH S-SCH

Physical Cell Identity (PCI)

P-SCH: for cell search and

identification by the UE -Carries

part of the cell ID (one of 3

orthogonal sequences)

S-SCH: for cell search and

identification by the UE Carries

the remainder of the cell ID (one

of 168 binary sequences)

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Measured neighbours

PCI

Best ranked cell

Measurement criteria

S – criteria

Suitable neighbours

R – criteria

Re-selection if not serving cell

neighboring cell was ranked with the highest

value R

Srx > Q rxlevmeas – (qrxlevmin – Qrelevmin

offset)-P Compensation

PCI PCI PCI

P Compensation = max(Pamax-PbMax)

Qrxlevmin SIB1 Cell Reselection:

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LTE_ACTIVE idle

For a cell to be suitable: S rx level>0 Srx > Q rxlevmeas – (qrxlevmin – Qrelevmin offset)

RRC – Idle Cell Selection done by UE Base on UE Measurements

Q rxlevmeas RSRP (Reference Signal Received Power)

Reference signals are transmitted in ALL radio blocks

LTE_ACTIVE IDLE (Cell Selection)

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For a cell to be suitable:

S rx level>0

Srx > Q rxlevmeas – (qrxlevmin – Qrelevmin offset)

Srx = -100 – (-80) = -20 (Will not do cell selection)

Q rxlevmeas=-100dBm

Will not do cell

selection

Q qrxlevmin =-80dBm

Q rxlevmeas RSRP (Reference Signal Received Power)

LTE_ACTIVE IDLE (Cell Selection)

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Measured neighbours

Best ranked cell

Measurement criteria

S – criteria

Suitable neighbours

R – criteria

Rs = Qmeas,s + Qhysts cell)

Rn = Qmeas,n - Qoffsets,n

for candidate neighbouring cells for cell

reselection

PCI PCI PCI PCI

Cell Reselection: R-Criterion

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Cell Reselection: R-Criterion Rs = Qmeas,s + Qhysts (for the serving

cell)

Qmeas,n

Qmeas,s

RS

RP

(d

BM

)

Rs

Rn

Qoffsets,n

Qhysts

Rn > Rs =>“cell reselection“

Treselection

the time interval value Treselection,

whose value ranges between 0 and

31 seconds

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Measurement Rules

In RRC_IDLE, cell re-selection between frequencies is based on absolute priorities, where each frequency has an associated priority. Cell-specific default values of the priorities are provided via system information.

E-UTRAN may assign UE-specific values upon connection release.

In case equal priorities are assigned to multiple cells, the cells are ranked based on radio link quality.

Measurement rules Which frequencies/ RATs to measure: high priority high priority + intra-frequency

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Handover – RRC Connected

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Handover – RRC Connected

In RRC_CONNECTED, the E-UTRAN decides to which cell a UE should hand

over in order to maintain the radio link.

In LTE the UE always connects to a single cell only – in other words, the

switching of a UE’s connection from a source cell to a target cell is a hard

handover.

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Measurement Report Triggering

For LTE, the following event-triggered reporting criteria are specified:

Event A1. Serving cell becomes

better than absolute threshold

Event A2. Serving cell becomes worse than absolute threshold

Event A3. Neighbour cell becomes better than an offset relative to the serving cell

Event A4. Neighbour cell becomes better than absolute threshold

Event A5. Serving cell becomes worse than one absolute threshold and neighbour cell becomes better than another absolute threshold

Source

eNodeB

DCCH: RRC

Measurement Control

DCCH: RRC

Measurement Report

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Measurement Report Triggering

For inter-RAT mobility, the following event-triggered reporting criteria are specified:

Event B1. Neighbour cell

becomes better than absolute threshold

Event B2. Serving cell becomes worse than one absolute threshold and neighbour cell becomes better than another absolute threshold

Source

eNodeB

DCCH: RRC

Measurement Control

DCCH: RRC

Measurement Report

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LTE Reference Signal Received Quality (RSRQ)

The RSRQ is defined as the ratio:

N · RSRP/(LTE carrier RSSI)

where N is the number of Resource Blocks (RBs) of the LTE carrier RSSI measurement bandwidth.

The measurements in the numerator and denominator are made over the same set of resource blocks.

While RSRP is an indicator of the wanted signal strength, RSRQ additionally takes the interference level into account due to the inclusion of RSSI.

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User Plane Switching in Handover

RLC

RLC

RLC RLC

RLC RLC

X2 Connection

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Event A3. Neighbour cell becomes better than an offset relative to the serving cell

1

2 3

4

Target cell

Source cell

Handover Timings

1. UE identifies the target cell

2. Reporting range fulfilled

3. After UE has averaged the measurement, it sends measurement report to source eNodeB

4. Source eNodeB sends handover command to the UE

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Handover

Source

eNodeB

Target

eNodeB

DCCH: RRC Measurement Control

DCCH: RRC

Measurement Report Handover

Decision X2: Handover Request

X2: Handover Request Ack

HO Command

Admission

Control

The event detected and reported is the event A3 within 3GPP LTE

The UE makes periodic

measurements of RSRP and RSRQ based

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Handover

Source

eNode

B

Target

eNode

B

Forward

Packets to

target X2: Handover

Request

HO

Command

Buffer

Packets

180


Handover - Buffer Forwarding

User Plane ACK

Source

eNodeB

Target

eNodeB

Forward Packets to

target

Switch path Request

HO Command

Buffer Packets

MME SAE

User Plane UpdateRequest

Switch DL path

Switch path Ack

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Handover

Source

eNodeB

Target

eNodeB

DCCH: RRC Measurement

Configuration

DCCH: RRC

Measurement Report

Handover

Decision X2: Handover Request

X2: Handover Request Ack

DCCH: RRC Connection

Reconfiguration

In LTE, data buffering in the DL occurs at the eNB because the RLC protocol terminates at the eNB. Therefore, mechanisms to avoid data loss during inter- eNB handovers is all the more necessary when compared to the UMTS architecture where data buffering occurs at the centralised Radio Network Controller (RNC) and inter-RNC handovers are less frequent.

RRCConnectionReconfigurationComplete message.

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Handover

IP

L2 Ethernet

UDP

GTP -C

L1-SDH

Serving Gateway

MME

IP L2

Ethernet

UDP

GTP -C

L1-SDH

SCTP

IP

S1AP

NAS

L2

(Ethernet)

IP

L2 Ethernet

UDP

GTP -U

L1-SDH

MAC

PHY

RLC

PDCP

IP

TCP/UDP

User Plane

MAC

PHY

RLC

RRC

NAS

Control

DA

TA

SCTP

IP

S1AP

NAS

L2 (Ethernet)

MAC

PHY

RLC

RRC

NAS

Control

S1- Control

MME

DIRECTION

Connected Mode Mobility

In LTE_ACTIVE, when a UE moves between two LTE cells

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Questions 1. Define the following:

a) Reference Signal Received Quality (RSRQ)

b) E-UTRA RSSI

c) Reference Signal Received Power (RSRP),

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Questions

2. What is a PCI and how many are there?

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Questions

4. What is the difference between PCI and global cell ID?

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Questions

5. The total number of handovers are likely to be higher in LTE than in UMTS. Why?

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Thank you

AIRCOM Asset LTE Basics and Asset

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Transcript of AIRCOM Asset LTE Basics and Asset