8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
1/49
GBC_006_E1_0 GSM Advanced Technology
ZTE University
GSM-BSS Team
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
2/49
Objectives
At the end of this course, you will be able to:
Understand HR services and implementation
methodsUnderstand principles of ZTE ultra-distance
coverage technology
Understand concepts, features and specifications of
EDGE technology
Grasp satellite Abis transmission configurations
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
3/49
Contents
HR Services
Ultra-Distance Coverage Technology
EDGE Technology
Satellite Abis Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
4/49
Basic Concepts
According to the switching mode, TCHs are divided into
circuit switching channels and data switching channels.
According to the transmission rate, TCHs are divided intoFull Rate (FR) channels and Half Rate (HR) channels.
The rate of GSM FR channel is 13 kbps while the rate of
GSM HR channel is 6.5 kbps. In addition, the Enhanced
FR channel has the same rate (13 kbps) as the FR
channel, but has better compression encoding scheme
than the FR channel, thus it has better voice quality.
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
5/49
HR Frame Structure
If the HR voice channel is adopted, the air interfaces frame
structure does not change. The multi-frames odd-numbered
frames are allocated to a user, even-numbered frames are
allocated to another user, and the 26th idle frame functions as
SACCH of the second user. Therefore, the channel capacity
doubles, that is, the channel bears two TCH/H services rather
than the original one TCH/F service.
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
6/49
HR Frame Structure
ZTE equipments support both static HR and dynamic HRservice
Static HR service
Static HR service means that the system HR channels aredecided in network planning, and the static configuration is
made on the system OMCR equipments. During the system
running, the HR channel occupies fixed carrier and timeslots,
and each timeslot on the carrier maintains its status as HR orFR that is set when being allocated, and the status can not be
changed. Fine adjustment can be made to the static
configuration in later network optimization.
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
7/49
HR Frame Structure
Dynamic HR service
Dynamic HR service means that only FR service is provided during the
systems initial running, and the ratio of commissioned HR channels
depends on the traffic change during system running.
When the traffic increases, the reserved dynamic HR auxiliary timeslots
of Abis interface are used to start the conversion from idle FR channels
to HR channels. In this way, HR channels are used to increase the
system traffic capacity and reduce the congestion rate.
When the traffic decreases, the conversion from idle HR channels to FR
channels is started, to guarantee the system voice quality with FR
channels. With dynamic HR service, the advantages of HR service can
be fully utilized in handling traffic burst and network capacity expansion.
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
8/49
HR Service Implementation
In ZXG10-BSS system, the HR service implementation process
in uplink direction is as follows:
The HR frame is processed by BTS first and then sent to RMM
through Abis interface. BIPP performs the internal conversion
from 8 kbps channel to 16 kbps channel and then sends the
frame to Bit-Oriented Switching Network (BOSN). After being
processed by BOSN, the HR frame enters the TC unit and the
rate adaptation unit that handle the HR service. Finally, the
frame is sent to MSC from A-interface at the speed of 64 kbps.
in downlink direction, just reverse of that in uplink direction.
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
9/49
Uplink: conversion from 8 kbps to 16 kbps
Downlink: conversion from 16 kbps to 8 kbps
BB
TT
SS
BB
SS
CC
TT
CC
UU
BB
SS
CC
RR
MM
MM
LA
N
BB
SS
CC
SS
CC
MM
MS supporting
HR-service
BB
TT
SS
BB
SS
CC
TT
CC
UU
BB
SS
CC
TT
CC
UU
BB
SS
CC
RR
MM
MM
BB
SS
CC
RR
MM
MM
OMC-R Server OMC-R Client
LAN
BB
SS
CC
SS
CC
MM
BB
SS
CC
SS
CC
MM
Processing HR frame
A-interface 64
kbps voice channel
Configuring HR,
performance measurement,
and service flow processing
16 kbps
HR channel
16 kbps
HR channelAbis interface 8
kbps HR channel
Uplink: decode HR frame to 64 kbps voice
channel
Downlink: encode 64 kbps voice channel into
16 kbps HR channel
Configuring HR,
performance measurement,
and relevant O&M
processing
HR Service Implementation
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
10/49
HR Channel Allocation Strategies
ZXG10-BSS system can automatically recognize whether the terminal
supports HR , and can decide whether the terminal accesses HR, FR,
EFR channel according to parameter configurations.
The system decides the allocation priority for HR, FR, and EFRchannels according to the users voice channel priority issued by MSS.
Priority allocation parameters for HR, FR, and EFR channels are
supported. For terminals that support HR service, if MSS does not
specify the priority, the system decides to allocate HR, FR, or EFRchannel according to priority allocation parameters. After adopting this
allocation strategy, if a resource is unavailable, the system will
automatically allocate another resource instead.
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
11/49
HR Channel Allocation Strategies
The TC that supports HR service also supports FR and
EFR. After TCs related to FR and EFR are occupied, the
system will allocate TCs that support HR service to satisfy
FR and EFR requirements. After TCs that support HR
service are occupied, the system stops allocating HR
radio resource, and allocates the FR channel and EFR
channel until the TC resource that supports HR service is
available.
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
12/49
HR Service Applications
HR applications in area with burst traffic
The HR service is most effective in handling burst traffic in areas
such as the stadium, campus, or rendezvous. These areas all
have the common feature that the heavy traffic occurs
periodically or suddenly. For example, the traffic increases
suddenly during a match in a stadium, and the traffic on campus
increases suddenly after class. The dynamic HR service is most
appropriate to apply in such situations. In normal cases, the
traffic is low, and the channel is in FR status. When the traffic
increases suddenly, the channel automatically converts to HR
status, relieving the traffic congestion and avoiding the waste
that is usually caused by the common capacity expansion.
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
13/49
HR Service Applications
HR applications in area with dense traffic
The traffic is dense in areas such as the dense urban area, airport,
railway station, and plaza. In order to avoid frequent network
adjustment, the HR service can be adopted to temporarily relieve
the pressure of capacity expansion. Before the next capacity
expansion is performed, commissioning the dynamic HR or static
HR can handle the emergent capacity increase. The HR service,
combined with a long-term planning and capacity expansion,
provides a flexible choice for operators in capacity expansion.
Moreover, the HR service is also a solution for network capacity
expansion for dense urban area where the frequency resource is
limited and the site expansion is infeasible.
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
14/49
HR Service Applications
HR applications in area with low-end users
In some areas with low-end users such as the remote rural
area, operators also provide the coverage to enhance their
competition power. These low-end users do not have high
requirement for the voice quality. Thus the HR service
(static HR or dynamic HR) can be adopted together with
some wide-coverage technologies to realize a low-cost
coverage.
HR service
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
15/49
Contents
HR Services
Ultra-Distance Coverage Technology
EDGE Technology
Satellite Abis Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
16/49
Technological Background
It is specified in GSM protocols that the maximum access
radius of GSM 900 MHz system is 35 km, and the
corresponding Time Advance (TA) is 63. Such restrictions
in GSM protocols are mainly due to that the coverage
larger than 35 km is difficult to realize in the GSM 900
MHz environment, and can be realized only in some
special propagation environments.
Ultra-Distance Coverage Technology
Ult Di t C T h l
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
17/49
Technological Background
With the evolution of GSM protocols, there are more
frequency bands. Because the propagation loss of GSM
400 MHz system is less that that of GSM 900 MHz
system, it is specified that the coverage radius of the
former can be larger than 35 km, the maximum access
radius of the former can be 120 km, and the
corresponding TA is up to 219. For the time being, except
for GSM 400 MHz system, other GSM systems do not
support TA that is larger than 63.
Ultra-Distance Coverage Technology
Ult Di t C T h l
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
18/49
Radio Interface Restrictions
In GSM system, each carrier adopts the TDMA mode,
that is, eight timeslots constitute a frame, and the eight
timeslots correspond to eight physical channels
respectively, as shown in Figure.
TS1 TS2 TS3 TS4 TS5 TS6 TS7 TS0TS0TS7 TS1
Frame
Time Axis
Ultra-Distance Coverage Technology
Ult Di t C T h l
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
19/49
Radio Interface Restrictions
During the call process, one user occupies one timeslot (time
window), and at the base station, each timeslot corresponds to
a user. Thus the MS-sent data that is received by the base
station can only fall into the users time window, otherwise, the
next channel will be influenced.
If MS is in the idle status, it does not know the distance from it
to BTS. Therefore, when sending the first access request, MS
takes its own time window as reference. Because delay exists
in space transmission, the time window has a certain offset
when the MS signal actually reaches BTS, that is, delay exists .
Ultra-Distance Coverage Technology
Ult Di t C T h l
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
20/49
The length of a TA is one byte. As specified in GSMprotocols, both GSM 900 MHz system and GSM 1800
MHz system uses six bits to send the TA and the other
two bits are reserved. Thus the maximum TA value is 63,
i.e. 63 bits, of which each bit equals 3.69 ms.
The space transmission delay includes uplink delay and
downlink delay (the uplink distance equals the downlink
distance). The signal is transmitted at the velocity of light.
The maximum coverage radius is calculated as follows:
(63 3.69 10-6) 3 10 8/ 235 km
Radio Interface Restrictions
Ultra-Distance Coverage Technology
Ultra Distance Coverage Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
21/49
Radio Interface Restrictions
Thus for GSM 900 MHz system and GSM 1800 MHz system,
the maximum coverage radius is specified as 35 km in GSM
protocols. The following lists the restrictions:
1. Restrictions of Access Burst (AB) For the AB of MS, MS sends it according to its own time
reference TA = 0. If the distance between MS and BTS exceeds
35 km, then even the significant bits (0~87) of AB can not fall into
the same timeslot completely. According to the common methodsspecified in GSM protocols, BTS can not decode the AB. In other
words, if MS is more than 35 km away from BTS, it can not
access the network, which then causes subsequent ABs unable
to be decoded.
Ultra-Distance Coverage Technology
Ultra Distance Coverage Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
22/49
Radio Interface Restrictions
2. Restrictions of MSs TA adjustment capability
After MS accesses the network successfully, Normal Burst
(NB) is sent on the traffic/signaling channel. If the distance
between MS and BTS exceeds 35 km, BTS can not adjust
the MSs sending time, which inevitably interferes the
running of other MSs on other timeslots.
Ultra-Distance Coverage Technology
Ultra Distance Coverage Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
23/49
Radio Interface Restrictions
Restriction of upper-layer signaling:
In layer-3 signaling, TA is used by some messages. The
GSM 900 MHz system and GSM 1800 MHz system only
support TA 63, thus when TA > 63, the handling for
abnormal signaling flow is initiated.
The messages are restricted by the condition TA 63, thus
if TA > 63, the normal signaling processing will be
influenced.
Ultra-Distance Coverage Technology
Ultra Distance Coverage Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
24/49
Breakthrough Methods
There are two methods to break the restriction of coverage distance
specified in GSM protocols (i.e. the maximum TA is 63, or the maximum
coverage radius of GSM 900 MHz system and GSM 1800 MHz system is
35 km). Breakthrough method 1
Adopts GSM 400 MHz system, or realizes the method specified in GSM 400
MHz system in GSM 900 MHz system.
Breakthrough method 2
BTS adopts the special radio channel mapping technology and improved
BTS receiving technology at radio interface, to guarantee there is no mutual
interference between BTSs.
Ultra-Distance Coverage Technology
Ultra-Distance Coverage Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
25/49
Breakthrough Methods
Breakthrough method 1:
According to GSM protocols, only the GSM 400 MHz system can
have TA that is larger than 63 and the maximum TA value is 219.
For GSM 400 MHz system, two frequency bands are defined in
GSM protocols: GSM 450 MHz and GSM 480 MHz. As to date,
the GSM 400 MHz system has not been commercialized.
The following lists the advantage and disadvantage of
breakthrough method 1:
Ultra-Distance Coverage Technology
Ultra-Distance Coverage Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
26/49
Breakthrough Methods
Advantage
Since the specification in GSM protocol is broken through,
there is no capacity limit when realizing a coverage
distance larger than 35 km.
Disadvantage
Because the GSM 900 MHz MS does not adapt to GSM
400 MHz system, appropriate MS is required, but it is
difficult to realize in actual applications.
Ultra-Distance Coverage Technology
Ultra-Distance Coverage Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
27/49
Breakthrough Methods
Breakthrough method 2:
If the coverage radius exceeds 35 km, then MS must
support TA > 63. However, the maximum TA recognized by
GSM 900 MHz MS is 63 bits. It is impossible to upgrade all
MSs, thus the restriction that the maximum coverage radius
is 35 km can be broken through by applying special radio
channel mapping technology and improved BTS receivingtechnology at the radio interface. In other words, BSS
should be upgraded.
Ultra-Distance Coverage Technology
Ultra-Distance Coverage Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
28/49
Breakthrough Methods
The following lists the advantage and disadvantage of
breakthrough method 2:
Advantage
It is easy to be applied because no change should be made
in MS and the cost is low.
Disadvantage
A certain system capacity is sacrificed. In normal cases,one carrier provides eight channels. If the coverage area is
very large, there might not be eight channels. The number
of channels depends on specific networking solutions.
Ultra Distance Coverage Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
29/49
Contents
HR Services
Ultra-Distance Coverage Technology
EDGE Technology
Satellite Abis Technology
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
30/49
Definition
Enhanced Data for GSM Evolution (EDGE) includes Enhanced
General Packet Radio Service (EGPRS) and Enhanced Circuit
Switched Data (ECSD). EDGE is a method used to improve the data
transmission rate during GSM radio connection.
Essentially, EDGE is only a new modulating and channel encoding
technology, which can be used to transmit Packet switching (PS)
and Circuit Switching (CS) data/voice. As an evolved GPRS-to-
UMTS solution, EDGE enables the network operator to use currentradio network equipments to the maximum extent. It also provides
PC multimedia communication services ahead of time before the
third generation mobile network become commercialized.
EDGE Technology
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
31/49
Feathers
The system architecture of EDGE network is similar to
that of GSM network. The following lists features of the
EDGE technology in the access service and network
establishment:
1. Access service
The bandwidth is increased greatly. The peak transmission
rate of mobile data service is up to 384 kbps.
It provides more precise network-layer positioning service.
EDGE Technology
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
32/49
Feathers
2. Network establishment
As a modulating and encoding technology, EDGE changes
the transmission rate at the air interface.
EDGEs air interface features, including the air channel
allocation mode and TDMA frame structure, are the same
as those of GSM.
EDGE does not change the architecture of GSM network or
GPRS network, and does not have new NEs. It only
updates BSS
gy
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
33/49
Feathers
The core network adopts the three-layer model: service
application layer, communication control layer, and
communication connection layer. The interface between
layers is standard. The hierarchical architecture makes
the call control and communication connection mutually
independent. It also fully uses advantages of the packet
switching network, making the bandwidth allocation
closely related to the traffic. It especially suits the VoIP
service.
gy
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
34/49
Feathers
Media Gateway (MGW) is adopted in EDGE. MGW has
the same functions as Signaling Transfer Point (STP),
and can realize the signaling network establishment in IP
network. Moreover, MGW is not only the interface
between GSM circuit switching service and PSTN but
also the interface between Radio Access Network (RAN)
and 3G core network.
gy
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
35/49
Feathers
EDGE supports two data transmission modes: packet
switching and circuit switching. With the packet data
service, a rate of 11.2 kbps ~ 69.2 kbps per timeslot can
be realized. EDGE supports the circuit switching service
with a rate of 28.8 kbps. EDGE also supports
symmetric/asymmetric data transmission, which is very
important for the mobile equipment to access network.
For example, in EDGE system, the user can have a
higher rate in downlink than in uplink.
gy
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
36/49
Specifications
The EDGE standardization involves the following three
aspects:
Standardizes the relevant change in physical layer (the
definition of modulation and coding method)
Standardizes the change in ECSD protocol
Standardize the change in EGPRS protocol
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
37/49
Specifications
EDGE is realized in two phases:
Phase 1: provides the single/multiple-timeslot packet
switching service with a rate of less than 64 kbps and the
single/multiple-timeslot circuit switching service.
Phase 2: provides real-time services not included in phase
1 and adopts the new modulating technology.
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
38/49
Key technologies
EDGE modulation mode
EDGE adopts 8-PSK as its modulation mode. 8-PSK has
the same modulation quality as GMSK, considering the
interference generated from adjacent channels. It enables
EDGE channels to be completely integrated in the current
frequency planning, and can allocate the new EDGE
channel as standard GSM channel.
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
39/49
Key technologies
Radio block structure
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
40/49
Key technologies
Channel coding
The nine MCSs of EDGE are categorized into three groups
according to their characteristics:
Family A (MCS-3, MCS-6, MCS- 8, MCS-9)
Family B (MCS-2, MCS-5, MCS-7)
Family C (MCS-1, MCS-4)
For coding scheme structures in the same group, either one
structure includes another or being included by another, which
makes it easy to realize conversion between coding rates.
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
41/49
Key technologies
In practical applications, balance should be kept between
the transmission rate of valid information and the valid
transmission quality. The low-rate channel coding
scheme, which contains many redundancy error
correction codes but without transmitting much valid
information, is suitable for an environment with poor
transmission quality.
EDGE Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
42/49
Key technologies
For example, on the edge of a cell, the low-rate GMSK
modulation method MCS1 ~ 4 is more suitable for
compensating poor link quality; in the central area of a
cell where propagation conditions are good, the high-rate
MCS is often adopted.
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
43/49
Contents
HR Services
Ultra-Distance Coverage Technology
EDGE Technology
Satellite Abis Technology
Satellite Abis Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
44/49
Satellite Transmission Features and Solutions
The following problems will be encountered when the
satellite link is used to realize transmission between BTS
and BSC.
The delay of Abis link is long. The information sent from
the satellite ground station is transferred through the
satellite and then received by another ground station. The
end-to-end delay is not less than 260 ms, which does not
have much to do with the ground stations position.
Satellite Abis Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
45/49
Satellite Transmission Features and Solutions
BER The satellite links BER is much larger than that of the ground
link. Because of this factor and the influence of fading, the BER
change is very large. On the other hand, the large delay and
BER on the transmission link will cause the message throughput
to drop.
Clock
The precision of the satellite Abis clock is not very good. The above problems do not occur when the ground link is used
to realize transmission between BTS and BSC, thus they should
be resolved first.
Satellite Abis Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
46/49
Satellite Transmission Features and Solutions
Solution:
BTS clock
Because the precision of the clock extracted from Abisinterface is much less than the clock precision specified in
GSM protocols, such a clock is not used to synchronize
BTS any more. Instead, when using the satellite link to
connect Abis interface, the high-precision clock source
inside BTS is often used as BTS clock source. In other
words, the inner clock of BTS is used for synchronization.
Satellite Abis Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
47/49
Satellite Transmission Features and Solutions
Protocol timer
Adjust the interval of timers in some BTS/BSC protocols to
make these protocols to adapt to large delay. The LAPD
timer of Abis is influenced most.
Satellite Abis Technology
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
48/49
ZXG10-BSS Satellite Abis Principles
ZXG10-BTS realizes the satellite Abis by setting
transmission modes through setting DIP switches at BTS.
According to the DIP switch setting, BTS sets
corresponding inner processing modes. BSC
automatically identifies the BTS processing mode and
performs relevant processing.
In order to save the cost of satellite transmission, the
satellite Abis often adopts Abis multiplexing mode to
reduce the number of timeslots at Abis interface.
8/13/2019 GBC 006 E1 1 GSM Advanced Technology-49
49/49
Thank you
Top Related