ZTE GSM BSS UR11.2 Basic Feature Description

GSM BSS Basic Feature

Description

UR11.2

GSM BSS Basic Feature Description

ZTE Confidential Proprietary 1


Version Date Author Reviewer Notes

V1.0 2011/11/20 ZTE Not open to the third party

V1.10 2012/6/11 ZTE Modify some features

2012 ZTE Corporation. All rights reserved.

ZTE CONFIDENTIAL: This document contains proprietary information of ZTE and is not to be disclosed or used

without the prior written permission of ZTE.

Due to update and improvement of ZTE products and technologies, information in this document is subjected to

change without notice.


2 ZTE Confidential Proprietary

TABLE OF CONTENTS

1 Instruction .......................................................................................................... 6

2 Service ............................................................................................................... 7

2.1 Voice Service ....................................................................................................... 7

2.1.1 ZGB-01-01-001 Full Rate (FR) Speech Codec ..................................................... 7

2.2 Data Service ........................................................................................................ 8

2.2.1 ZGB-01-02-001 Quality of Service (QoS) ............................................................. 8

2.3 Supplementary Service ........................................................................................ 9

2.3.1 ZGB-01-03-001 Emergency Call Handling ........................................................... 9

2.3.2 ZGB-01-03-002 Data Traffic Channels ............................................................... 10

2.3.3 ZGB-01-03-003 Short Message Service (SMS).................................................. 10

3 Mobility Management ...................................................................................... 12

3.1 Paging ............................................................................................................... 12

3.1.1 ZGB-02-01-001 Paging ...................................................................................... 12

3.2 Handover and Reselection ................................................................................. 13

3.2.1 ZGB-02-02-001 Basic Handover ........................................................................ 13

3.2.2 ZGB-02-02-004 Support 64 Neighboring Cells ................................................... 16

3.2.3 ZGB-02-02-005 Double BCCH Allocation List .................................................... 17

3.2.4 NoneZGB-02-02-006 Cell Reselection ............................................................... 17

3.2.5 ZGB-02-02-007 Cell Selection ........................................................................... 19

4 Resource Management ................................................................................... 20

4.1 Congestion Control ............................................................................................ 20

4.1.1 ZGB-03-01-001 MS Access Control ................................................................... 20

4.1.2 ZGB-03-01-002 Directed Retry .......................................................................... 22

4.1.3 ZGB-03-01-003 Queuing .................................................................................... 23

4.1.4 ZGB-03-01-004 Immediate TCH Assignment ..................................................... 24

4.2 Channel Allocation ............................................................................................. 25

4.2.1 ZGB-03-02-001 Support of SDCCH/4 and SDCCH/8 ......................................... 25

4.2.2 ZGB-03-02-002 Flexible SDCCH Configuration ................................................. 26

4.2.3 ZGB-03-02-003 Dynamic Configuration of SDCCH ............................................ 26

4.2.4 ZGB-03-02-004 MAC Dynamic Allocation Mode ................................................ 27

4.2.5 ZGB-03-02-005 Static Channel Management .................................................... 28

4.2.6 ZGB-03-02-006 Dynamic Channel Management................................................ 28

4.2.7 ZGO-03-02-001 Idle Channel Measurement ...................................................... 29

4.2.8 ZGO-03-02-002 Enhancement on CS Channel Allocation .................................. 30

4.2.9 ZGO-03-02-003 Enhancement on PS Channel Allocation .................................. 32

4.3 Circuit Management ........................................................................................... 34



4.3.1 ZGB-03-03-001 2M High Speed Signaling Link .................................................. 34

4.3.2 ZGB-03-03-002 Enhanced E1 Link between BSC and BTS ............................... 35

4.3.3 ZGB-03-03-003 LAPD Cluster............................................................................ 36

4.3.4 ZGB-03-03-004 TC Resource Dynamic Sharing ................................................ 37

4.3.5 ZGB-03-03-005 PCU Resource Dynamic Allocation .......................................... 37

4.4 Reliability ........................................................................................................... 38

4.4.1 ZGB-03-04-001 BSC Load Control..................................................................... 38

4.4.2 ZGB-03-04-003 BTS Recovery .......................................................................... 40

4.4.3 ZGB-03-04-004 Dry Contact Alarm .................................................................... 40

4.4.4 ZGB-03-04-006 Backward Compatibility for BTS ............................................... 41

4.5 GPRS/EDGE ..................................................................................................... 41

4.5.1 ZGB-03-05-001 Coding Scheme CS1~CS4 ....................................................... 41

4.5.2 ZGB-03-05-002 Initial Coding Scheme Per Cell Settable ................................... 43

4.5.3 ZGB-03-05-005 8/11 bit Access Burst ................................................................ 43

4.5.4 ZGB-03-05-006 Class A, B, C MS ...................................................................... 44

4.5.5 ZGB-03-05-007 One Phase Access ................................................................... 45

4.5.6 ZGB-03-05-008 Two Phase Access ................................................................... 46

4.5.7 ZGB-03-05-009 Network Mode of Operation (NMO) 1~3 ................................... 47

4.5.8 ZGB-03-05-011 Timeslot Multiplexing ................................................................ 49

4.5.9 ZGB-03-05-012 GPRS Link Adaptation .............................................................. 50

4.5.10 ZGB-03-05-013 Delayed TBF Release in DL ..................................................... 51

4.5.11 ZGB-03-05-014 Delayed TBF Release in UL ..................................................... 51

4.5.12 ZGB-03-05-015 RLC Acknowledged/ Unacknowledged Mode ........................... 52

4.5.13 ZGB-03-05-016 Downlink BVC Flow Control ...................................................... 53

4.5.14 ZGB-03-05-017 Downlink MS Flow Control ........................................................ 54

4.5.15 ZGO-03-05-003 EGPRS Packet Channel Request on CCCH ............................ 55

4.5.16 ZGO-03-05-007 EGPRS Activation per Cell ....................................................... 56

5 Network Performance ..................................................................................... 56

5.1 Coverage Enhancement .................................................................................... 56

5.1.1 ZGB-04-01-001 Receiving Diversity ................................................................... 56

5.1.2 ZGB-04-01-002 Support Tower Mounted Amplifier (TMA) .................................. 57

5.2 Network Quality Improvement ............................................................................ 58

5.2.1 ZGB-04-02-001 Traffic Hold at Channel Blocking............................................... 58

5.2.2 ZGB-04-02-002 Static BTS Power Control ......................................................... 59

5.2.3 ZG0-04-02-019 Discontinuous Reception (DRX)................................................ 60

6 Transmission ................................................................................................... 60

6.1 Flexible Networking ............................................................................................ 60

6.1.1 ZGB-05-02-001 Automatic Bridge in BTS Chain Networking .............................. 60

6.1.2 ZGB-05-02-002 Star, Tree, and Chain Networking ............................................. 61

6.1.3 ZGO-05-02-031 Distributed Architecture of BTS ................................................ 62



6.2 Synchronization ................................................................................................. 63

6.2.1 ZGB-05-03-001 Clock Synchronization .............................................................. 63

7 Others .............................................................................................................. 65

7.1 O&M .................................................................................................................. 65

7.1.1 ZGB-06-01-001 Monitoring Um Interface ........................................................... 65

7.1.2 ZGB-06-01-002 Abis Interface Monitoring .......................................................... 66

7.1.3 ZGB-06-01-003 Performance Data Measurement .............................................. 67

7.1.4 ZGB-06-01-005 BSC Monitor Functions ............................................................. 68

7.1.5 ZGB-06-01-006 BTS Software Loading .............................................................. 69

7.1.6 ZGB-06-01-007 Cell Traffic Statistics ................................................................. 71

7.1.7 ZGB-06-01-008 BSC Diagnostic Tests ............................................................... 72

7.1.8 ZGO-06-01-003 BSC LMT ................................................................................. 74

7.1.9 ZGO-06-01-010 VSWR Detection ...................................................................... 75

7.2 Security .............................................................................................................. 76

7.2.1 ZGB-06-02-001 A5/1 Ciphering Algorithm .......................................................... 76

8 Acronyms and Abbreviations ......................................................................... 77



FIGURES

Figure 4-1 Immediate Assignment of TCH .........................................................................24

Figure 6-1 Star, tree and Chain Networking .......................................................................62

TABLES

Table 2-1 RLC transmission modes corresponding to reliability class ..................................8

Table 4-1 Bandwidth Requirement of LADP Cluster ...........................................................36

Table 4-2 Coding Scheme CS1-CS4 .................................................................................42

Table 4-3 Three Network Operation Modes .......................................................................48



1 Instruction

The complete set of feature description for radio access part of ZTE GSM consists of

three documents:

ZTE GSM BSS Basic Feature Description,

ZTE GSM BSS Optional Feature Description,

ZTE NetNumen-M31 Feature Description.

This document contains the basic features of ZTE GSM BSS.

ZTE GSM BSS Feature ID number is in the format of ZGx-xx-xx-xxx. The header ZG

stands for ZTE GSM.



2 Service

2.1 Voice Service

2.1.1 ZGB-01-01-001 Full Rate (FR) Speech Codec

Benefits

This feature is a speech codec that gives good speech quality used for Full Rate traffic

channels and makes the user have better experience.

Description

Full rate speech coder is the basic coding scheme of GSM system. It uses Linear

Predictive Coding with Regular Pulse Excitation (LPC-RPE codec). It is a full rate speech

codec and operates at 13 kbps. Full Rate Speech Codec is based on RPE-LTP. 160

speech samples in 13-bit PCM are mapped to 260bit (interval is 20ms and sampling rate

is 8KHz), which is called coding. Decoding refers to the mapping relation between the

160 reconstructed speech samples from 260bit coding packet to export packet. The

coding stream is 13kbit/s.

The traffic channel using FR speech codec is usually expressed by TCH/F. One TRX

supports maximum 8 TCH/F time slots. It can give good speech quality with Mean

Opinion Score (MOS) 3.8.

Introduced Version

Before V09R1

Enhancement

None



2.2 Data Service

2.2.1 ZGB-01-02-001 Quality of Service (QoS)

Benefits

This feature enhances high-end subscribers service experience in the case of restricted

radio resource for packet service.

Description

GPRS/EDGE QoS includes the parameters as follows:

Delay class: 1 (short delay) ~ 4 (background)

R -5) ~ 5 (>5*10-4)

Peak throughput class: 1 (



The RLC mode of uplink TBF is determined by mobile phones, while the RLC mode of

downlink TBF is determined by BSC. According to the wireless transmission features,

BSC sets the RLC mode to acknowledged mode for all reliability classes in the downlink.

Introduced Version

Before V09R1

Enhancement

None

2.3 Supplementary Service

2.3.1 ZGB-01-03-001 Emergency Call Handling

Benefits

Emergency calls have the highest priority, even if the system congests or overloads,

emergency calls will be handled rapidly and guaranteed good service quality. This

enhances emergency call handling efficiency and user satisfaction.

Description

Emergency call is a basic voice service of the GSM system. When the MS accesses the

network using an emergency call, the BSS treats and provides higher priority and faster

service to it. So TCH channel will be allocated with higher priority. Allocation of SDCCH

channel will be considered if the TCH channel is busy.

Emergency calls have highest priority, even if the MS does not have any SIM card or the

SIM card is locked, he/she still can dial emergency calls successfully, even if the system

congests or overloads, emergency calls will be handled rapidly and guaranteed good

service quality.

Introduced version

Before V09R1



Enhancement

None

2.3.2 ZGB-01-03-002 Data Traffic Channels

Benefits

Circuit Switched Data services (CSD) shows more ways to support dada services for 2G

operators. Operators can provide diversified services on the data platform of CSD to

attract more subscribers and achieve more profits.

Description

ZTE GSM BSS adopts TCH/F9.6 (transparent and non-transparent) data channels to

deliver circuit switched data services at a rate of 9.6 Kbits/s. The BSS provides the

lower-layer bearer service but does not process the upper-layer services. In

non-transparent data services, a set of radio link protocol is used for data correction and

retransmission between Mobile Station (MS) and Core Network (CN).

Introduced version

Before V09R1

Enhancement

None

2.3.3 ZGB-01-03-003 Short Message Service (SMS)

Benefits

This feature has great potential in attracting target subscribers and increasing revenue.

Many services can be deployed with short messages, such as stock information, current

exchange rate and weather forecast.

In addition, operator can send advertisement, bill and charge information to specific

subscribers by SMS, which makes them charge on not only subscribers, but also the



enterprise that needs the service.

Description

Support bi-directional (MT/MO) message transmission between MS and SMC.

One MS sends text to another MS (point to point, PTP) through network and SMC. The

text should not exceed 160 (English) letters.

SMC is in charge of short message storing and forwarding. This service is not only for

GSM users, but also for fixed network users that are able to receive short messages as

well.

BSS establishes links (SAPI =3) to transmit SMS. This transmission procedure is

transparent to BSS. MS sends and receives SMS in either busy or idle state.

In idle state, MS sets up a link (SAPI = 3) at Abis interface before sending or receiving

short messages. Then it will set up SAPI connection at Abis interface to send or receive

short messages.

Even if a call is coming, MS still can receive short message. After BSC receives the short

message from SMC, it will send Establish Request message to set up a link at Abis

interface first. BSC then transmits the short message to MS after a successful setup.

When MS is going through a call, short messages are carried on SACCH channel. When

MS is in idle state; short messages can be carried on SDCCH channel or FACCH

channel according to the network state.

Introduced version

Before V09R1

Enhancement

None



3 Mobility Management

3.1 Paging

3.1.1 ZGB-02-01-001 Paging

Benefits

This feature is a basic step to setup a call and send a SMS. Large paging capacity and

flexible process avoids congestion caused by paging overload and improves the call

setup success rate.

Description

Paging procedure is initialized by MSC or SGSN to locate the MS. After receiving the

paging message from CN, BSC sends the paging request to all cells in specified LA.

There are two kinds of paging: IMSI paging and TMSI paging. When IMSI is used for

paging, one paging message can contain two IMSI numbers, while four TMSI can be

packed in one paging message.

Paging is sent via CCCH. Downlink CCCH is shared by PCH and AGCH. Among them,

PCH sends paging message, and AGCH sends immediate assignment and immediate

assignment rejection message. According to GSM specification, there are 3 paging

groups in one multi-frame when the CCCH and SDCCH share one control channel, and

there are 9 paging groups when CCCH and SDCCH are configured individually. The

paging group in one multi-frame is shared by PCH and AGCH. Thus, the paging capacity

depends on the configuration method of CCCH, PCH, AGCH, and the ratio of IMSI

paging to TMSI paging. ZTE BSC supports a flexible channel configuration to provide

different paging capacity. The maximal paging capacity for one LAC is 400,000 times per

hour. ZTE BSS also supports paging retransmission. When the paging message is not

replied within certain duration, it will be retransmitted.

There are three paging types: CS call paging, PS paging, and SMS paging. Usually all

these paging messages are sent via CCCH. In order to avoid paging congestion, all

these traffics should be considered so that the LAC can be defined properly.



Introduced Version

Before V09R1

Enhancement

None

3.2 Handover and Reselection

3.2.1 ZGB-02-02-001 Basic Handover

Benefits

This feature enables the basic handover, allowing the terminals to keep talking while

moving in the cell or to the other cells, so as to guarantee the users voice quality during

handover as well.

Description

This feature enables the basic function related to the mobility management, which is

handover. BSC decides whether the terminals need to handover according to the

measurement reports. BSC updates the BCCH Allocation (BA) list first, and then selects

the suitable cell to handover after the handover decision is made. In order to avoid the

frequent handover failure, relevant failure penalty is adopted, which decreases the

signaling load and increases the handover successful ratio.

ZTE GSM supports BSC in dealing with the measurement reports with the sliding window

mechanism and the weighted average algorithm, and then selects the higher priority

handover algorithm according to the different handover reasons. For the intra-cell

handover, the suitable carrier and the timeslot of the minimum interference band is

selected; for the inter-cell handover, the target cell based on the layer strategy and the

handover decision criterion is selected.

The determinant factor of the target cells sequencing is load, priority and power margin.

First, sequence and filter the target cells list according to the traffic: the cell with full

traffic or exceeding the traffic threshold should be deleted from the list. Then sequence



all the target cells based on the priority. At last, sequence all target cells with the same

priority based on the power margin. Select the first cell in the list as the target cell to

handover.

If handover fails, the handover failure penalty should be adopted, which avoids the

repeated handover failure, and increases the successful handover ratio. For the intra-cell

handover, BSC restrains the user not to attempt handover during the penalty time of

handover failure. For the inter-cell handover, BSC deducts the offset value based on the

signal level of the cell, which reduces the possibility of the user handover to the last failed

target cell during the penalty time of handover failure.

In order to prevent the repeated handover, BSC compares the current time point with the

time point of last successful handover. If the difference between the two time point

exceeds the penalty time of repeated handover, the handover procedure is going on; if

not, the source cell of last handover should be deleted from the target cells list of this

handover first, and then select the suitable target cell for this handover.

The handover mode is divided into the synchronous handover and the asynchronous

handover, the synchronous handover is used for the inter-cell handover in the same site,

and the asynchronous handover is used for the handover between the different sites.

ZTE GSM supports basic and optional handover algorithms. Basic handover algorithm

includes: signal quality (uplink/downlink) handover, signal level (uplink/downlink)

handover, signal interference (uplink/downlink) handover, ultra-distance and Power

Budget (PBGT) handover. The details are shown as follows:

Signal Quality (Uplink/Downlink) Handover

Signal quality handover is a basic criterion for inter-cell handover, which is composed of

uplink and downlink, and the handover decision is the same. When the channel quality is

getting worse, the radio link maybe abnormal to release the occupied channel, leading to

the users call drop. In order to avoid this situation, when the mean error rate is greater

than the quality threshold for P times in N times, BSC triggers the signal quality handover

to save this call.

Signal Level (Uplink/Downlink) Handover

Signal level handover is a basic criterion for inter-cell handover, which is composed of



uplink and downlink, and the handover decision is the same. When the interference is

too low to trigger the interference or quality handover even the level fading is serious,

leading to the users call drop. In order to avoid this situation, when the signal lever is

lower than the level threshold for P times in N times, BSC triggers the signal level

handover to save this call.

Signal Interference (Uplink/Downlink) Handover

Signal Interference handover is the basic criterion for intra-cell handover, which is

composed of uplink and downlink, and the handover decision is the same. When the

interference occurs, the interference degree of every channel in the cell is different. So

the handover in the different channel of the same cell solves the interference problem.

When the signal quality is getting worse but the signal level is higher, the terminal enters

the pre-defined interference area for P times in N times, BSC triggers the signal

interference handover to save this call.

If there is not idle channel in the serving cell, the handover should be converted to the

signal quality handover to try the inter-cell handover. The difference between the signal

interference handover and the signal quality handover is: when the signal interference

handover occurs, the signal quality isnt worse to influence the call and the signal level is

high at present.

Ultra-Distance Handover

Ultra-distance handover is a basic criterion for inter-cell handover. If the terminal is far

from BTS, the ultra-distance handover is done to the nearest neighboring cell. When the

Time Advance (TA) is greater than the distance threshold for P times in N times, BSC

triggers the ultra-distance handover to save this call.

PBGT Handover

PBGT handover is a basic criterion for inter-cell handover, so as to keep the call in the

suitable cell. PBGT is gained from the signal level of the neighboring cell subtracting that

of the serving cell. When the downlink level of the neighboring cell is lower than the initial

threshold, if the PBGT of the neighboring cell is greater than the preset PBGT threshold

for P times in N times, BSC triggers the PBGT handover. PBGT handover is a non-saving

handover.



In order to make the PBGT occur in the same layer, and the neighboring cells level of

other layers is strong enough to execute the inter-layer PBGT handover, the inter-layer

timer should be set when the terminal accesses the network. If the inter-layer timer isnt

out, the neighboring cells level should add the offset value of the upper layer for PBGT

handover to the upper layer, and the neighboring cells level should add the offset value

of the lower layer for PBGT handover to the lower layer. If the timer is out, the normal

PBGT handover is executed.

Introduced Version

Before V09R1

Enhancement

None

3.2.2 ZGB-02-02-004 Support 64 Neighboring Cells

Benefits

This feature improves radio network performance and reduces call drop rate by providing

enough neighboring cells.

Description

This feature increases GSM neighboring cells from original 32 to 64 ones, meeting the

demand from growing network capacity and complexity. BSC supports handover and cell

reselection between different frequency bands with maximum 64 GSM handover

neighboring cells, 64 GSM cell reselection cells, and maximum 96 GSM/UMTS

neighboring cells. BSS sends neighboring cell list to MS by system information.

Introduced Version

Before V09R1

Enhancement

None



3.2.3 ZGB-02-02-005 Double BCCH Allocation List

Benefits

This feature enables terminals to adopt different BCCH Allocation (BA) list in idle mode

and connected mode in the high traffic area, realizing the benefits as follows:

Enhance the flexibility of the system, which means different operation methods

are used for terminal in idle mode and connected mode.

Increase the reselection successful rate for terminal in idle mode, so as to

access the network quickly.

Increase the measurement precision for terminal in connected mode, so as to

improve the accuracy for cell reselection.

Description

This feature enables terminals to adopt different BA list in idle mode and connected

mode to handover or reselection. The BA list is provided by the network to terminal, and

terminal gets the BCCH frequency from it. In case of connected mode, the BA list is sent

by SACCH for handover. In case of idle mode, the BA list is broadcasted by BCCH for

cell reselection.

ZTE GSM supports the double BA list in idle mode and connected mode for each cell,

and the maximum number of BCCH is 96. The length of the BA list in idle mode is long,

which includes more frequencies, to increase the reselection successful rate and to

access the network quickly. The length of the BA list in connected mode is short, which

only includes the real neighboring cells, to avoid wasting time to encode the Base Station

Identity Code (BSIC) of the uncorrelated cells, so as to improve the accuracy for cell

reselection.

Introduced Version

Before V09R1

Enhancement

3.2.4 NoneZGB-02-02-006 Cell Reselection

Benefits

This feature enables the reselection to the suitable neighboring cell in the idle mode and

the connected mode for the terminal, ensuring the terminal to offer the best radio



connection.

Description

This feature enables the cell reselection algorithm, which is defined in 3GPP protocol.

The terminal implements the cell reselection through the measurement of the radio

signal in BCCH carriers for the serving cell and the neighboring cells. The signal quality

criterion parameter C2 is used for cell reselection.

If one of the following conditions is satisfied, the cell reselection is triggered:

If C1 C2 (s) the cell reselection occurs; if not, and C2 (n) > C2

(s) + CRH the cell reselection occurs;

Where

C2 (n) is the C2 value of the neighboring cell.

C2 (s) is the C2 value of the serving cell.

CRH applies the hysteresis of cell reselection.

If the cell reselection occurs before the previous 15s, and C2 (n) > C2 (s) + 5dB, the cell

reselection occurs.

ZTE GSM supports the terminals controlled cell reselection, BSC sends the cell

reselection parameters to the terminal through the system information SI 2quater, and

then the terminal selects the cell satisfied with the reselection conditions to reselect in

the searching neighboring cells.

Introduced Version

Before V09R1

Enhancement

None



3.2.5 ZGB-02-02-007 Cell Selection

Benefits

This feature is the basic feature of GSM radio network.

Description

When the MS is switched on or following recovery from lack of coverage, it finds

available GSM PLMN, and selects an appropriate cell for residence. This process is

called "cell selection."

To select one appropriate cell is constrained by many factors, such as whether the cell

belongs to selected network, whether the cell is prohibited from accessing or not, the cell

priority, whether MS access level is prohibited by the cell and whether RF channel quality

is good enough. GSM standard defines C1, the path loss criterion parameter, to

demonstrate RF channel quality, which is the important factor for cell selection. The path

loss criterion is satisfied if C1 > 0.

If MS does not store BCCH message, it searches all the 124 RF channels (for dual-mode

MS, it also needs to search 374 GSM1800 RF channels), reads received signal strength

of each channel and calculates average signal level.

After MS tunes to the carrier with highest receiving level, it confirms whether it is BCCH

carrier or not. If so, the MS attempts to decode SCH to synchronize with this carrier and

reads system broadcast message on BCCH. The MS can only reside in the cell if the MS

correctly decodes BCCH data the cell belongs to the selected PLMN, C1 is larger than 0

and the cell access is not barred. Otherwise, MS is tuned to the next maximum carrier

until it finds an available cell.

If the MS fails to find an appropriate cell after searching 30 RF channels with best signal

strength, it continues monitoring the signal strength of all RF channels and searches

BCCHs with access not barred and C1 larger than 0. After finding an appropriate carrier,

the MS selects the cell without taking into account PLMN identification. In such a mode,

only emergency calls can be made.

If an MS stores BCCH carrier information before last power-off, it first searches the

stored BCCH carrier. If the MS can decode BCCH data of the cell but cannot reside in the



cell, it checks the BCCH Allocation (BA) list of the cell. If it still fails to find an appropriate

cell after searching all BCCH carriers in the BA list, the MS will initiate cell selection

procedure in the way described above.

Introduced Version

Before V09R1

Enhancement

None

4 Resource Management

4.1 Congestion Control

4.1.1 ZGB-03-01-001 MS Access Control

Benefits

This feature allows the operator to classify the subscribers to provide preferential service.

With Access Class Control (ACC), network operators can define some cells to be only

accessed by authorized subscribers.

For example, in traffic hotspot area, operators offer the additional cell to enforce the

traffic abilities; but only authorized subscribers can access the cell. So the operators can

ensure better service for these subscribers in busy hour, and additional income might be

obtained.

This feature can also be used to ensure telecommunication for staffs from special

sections in case of emergency.

Description

BTS continually broadcasts system information message to all MSs in the cell; an

important function of this message is to indicate the MS how to access this cell.



ACC information is included in system information. The GSM protocols define 16

classes:

10 classes (0-9) are randomly allocated to normal subscribers.

Class 10 is dedicated to emergency call.

5 classes (11-15) are allocated to specific high priority subscribers.

Every class is indicated by one bit in system information. If the bit is set to 1, the MS with

the corresponding ACC will be forbidden. Every MS is assigned an ACC, which is saved

in SIM card.

By setting the different ACCs, operator can enable some ACCs to access special cells.

These configurations are set in OMCR and included in system information broadcasted

by BTS.

Introduced Version

Before V09R1

Enhancement

In ZTE BSS version before V09R2, which access classes of users are forbidden to

access in case of radio resource congestion are configured statically on OMCR. So it is

possible for some users to be always forbidden to access in case of radio resource

congestion, while the other users can always access.

In V09R2, MS Access Control function applies sliding window method to decide the

forbidden MS classes, which avoids forbidding some fixed classes of MS.

There are 2 sets of access control parameters for resource congestion scenario, 2 sets

of access control parameters for normal scenario. Which set of access control

parameters to be used can be configured on OMCR. Each set of access control

parameters consists of the first barred access class, barred classes window size and

window sliding time interval.



4.1.2 ZGB-03-01-002 Directed Retry

Benefits

Directed retry realizes wireless resources sharing among neighboring cells during

assignment, effectively relieving the network congestion and the unbalanced usage of

wireless resources and greatly enhancing the assigning success rate.

Description

During TCH assignment, MS turns to serving cell for TCH channel resource; if network

doesnt have available TCH resource, cell will make forced release, forced handover or

queuing attempt according to calling priority, preemption vulnerability indicator, queuing

permission indicator and preemption capability indicator in assignment request; if the

attempt fails, directed retry procedure is initiated.

Then, according to measurement reports sent by MSs, network sorts the adjacent cells

which meet the rule 1 for handover to get the directed retry target cell list.

When sorting adjacent cells, the cells overloaded compared to load threshold are filtered

out first, and the remaining cells are sorted in accordance with the dynamic priorities and

power budget surplus.

Afterwards, BSC turns to the first cell in the target cell list for TCH channel. When TCH

channel is allocated from target cell, channel description of target cell are sent to MS

through assignment or handover command, MS then accesses to target cell. If network

doesnt support directed retry function, when MS fails to initiate forced release, forced

handover and queue, it sends to MSC the failure message and waits for clear command

from MSC, then releases wireless resources.

In addition, according to whether the attempted cells in directed retry cells list belong to

the BSC, directed retry is divided into internal and external directed retry. If the attempted

cells of directed retry belong to the BSC, then MS can directly apply channels to the cell

and make internal directed retry. If the attempted cells do not belong to the BSC, MS has

to send handover request to MSC through A interface and make external directed retry

via inter-BSC external handover flow. External directed retry in BSC part may select

whether to send request failure to MSC; if Yes is selected, request failure will be

delivered to MSC firstly before sending handover request with cause labeled as directed



retry.

Introduced Version

Before V09R1

Enhancement

None

4.1.3 ZGB-03-01-003 Queuing

Benefits

This feature improves the usage of the radio resources, improves the ratio of successful

assignment.

Description

In the assignment procedure of call setup or handover, if the serving cell has no idle

TCHs, and the queuing is allowed in this cell, and MSC indicates in the assignment

message that this MS is allowed to be queued, then the MS is put in a queue.

If some other MS releases a call or hands over to another cell and the serving cell has

idle TCHs, BSC will check if there is idle channel that can match some MSs request in

the queue in respect of subcell, channel type and frequency band. If there is such an idle

channel that matches, it will be assigned to the MS in the queue, then the call setup or

handover procedure continues.

Queuing time can be set individually for call attempts and for handover. When queuing

time is set to zero, the queuing function is deactivated.

By putting subscribers in queue instead of rejecting it when the radio resources are busy,

this feature increases the success ratio of call setup and handover.

Introduced Version

Before V09R1

Enhancement



None

4.1.4 ZGB-03-01-004 Immediate TCH Assignment

Benefits

This feature reduces the call setup time.

Reduce call failures caused by unavailable idle SDCCH in the serving cell.

Description

When this feature is activated, BSS assigns a TCH channel for MS in immediate

assignment procedure. This TCH channel is used as SDCCH to carry the dedicated

signalings. Then in assignment procedure, this channel is modified to a TCH channel to

carry user voice data. This is shown in the following graphic.

Figure 4-1 Immediate Assignment of TCH

MS

CHL_REQ

SABM

CHL_RQD

IMM_ASS_CMD

BSCBTS

CHL_ACT

CHL_ACT_ACK

IMM_ASS

EST_IND

DATA REQ(UM_CHL_MODE_MODIFY)

MODE MODIFY

MODE MODIFY ACK

MSC

ASS_REQ

DATA IND(UM_CHL_MODE_MODIFY_ACK)

ASS_COM

DTAP

UA

On OMCR, the operator can configure which kind of call can initiate immediate



assignment. Usually emergent call and call re-establishment are configured to apply this

feature.

Introduced Version

Before V09R1

Enhancement

None

4.2 Channel Allocation

4.2.1 ZGB-03-02-001 Support of SDCCH/4 and SDCCH/8

Benefits

This feature improves the channel utilization ratio by configuring different SDCCH type

according to cell traffic.

Description

SDCCH is used to transmit system signaling before TCH assignment, such as MS

register, Authentication, and Location Update. As one kind of low data rate logical

channel, several SDCCH channels can be mapped to one physical channel. There are

two different ways to configure SDCCH. One is combination with BCCH. In this

configuration, 4 SDCCH can be configured in the TS0 of BCCH TRX. This kind of

SDCCH is called SDCCH/, while SDCCH/8 means that a whole physical channel is

configured to eight SDCCH channels.

Which kind of configuration should be used depends on the capacity of a cell. Normally

SDCCH/4 is only used for a cell with no more than two TRXs. In ZTE BSS system,

SDCCH/4 and SDCCH/8 can be configured in a cell at the same time or individually.

Introduced Version

Before V09R1



Enhancement

None

4.2.2 ZGB-03-02-002 Flexible SDCCH Configuration

Benefits

This feature allows operator to configure any number of SDCCH in one cell to reduce the

risk of SDCCH congestion.

Description

ZTE BSS supports flexible configuration of SDCCH.

SDCCH can be allocated to every TRX in a cell.

SDCCH can be configured on every TS of one TRX.

Whether a cell supports frequency hopping or not has no effect on SDCCH.

For an extended coverage cell, SDCCH can be configured on both extended and

ordinary TRXs.

With the methods provided above, operator is able to configure SDCCH flexibly

according to cell traffic. It reduces the risk of SDCCH congestion and improves the

network performance.

Introduced Version

Before V09R1

Enhancement

None

4.2.3 ZGB-03-02-003 Dynamic Configuration of SDCCH

Benefits

This feature reduces call attempt failure caused by busy SDCCH.



Description

When this feature is activated, BSC adjusts the SDCCH number in a cell automatically

according to the load of SDCCH,

When the SDCCH channels in a cell are overloaded referring to the threshold set on

OMCR, and TCH channels are idle according to another threshold set on OMCR, BSC

changes one TCH into 8 SDCCHs automatically.

When SDCCH channels are idle, BSC combines 8 redundant SDCCH channels into 1

TCH channel to provide more traffic channels. Only those SDCCH channels formerly

obtained from TCH can be combined into TCH channels.

Introduced Version

Before V09R1

Enhancement

None

4.2.4 ZGB-03-02-004 MAC Dynamic Allocation Mode

Benefits

Dynamic Allocation Mode is defined in 3GPP which is the primary function to introduced

PS service.

Description

ZTE GSM BSS supports two MAC modes: Dynamic Allocation and Extended Dynamic

Allocation. This feature supports dynamic allocation. For Extended Dynamic Allocation,

please refer to ZGO-03-02-007 MAC Extended Dynamic Allocation.

With Dynamic Allocation, Network allocates one timeslot to more than one MS with

specified USF. For downlink data, the USF information is decoded in RLC/MAC headers

to determine which MS is assigned to send radio block in the uplink. In this way, the BSS

controls the uplink access of multiple MS on a timeslot.



The number of downlink PDCHs should be more than uplink PDCHs in Dynamic

Allocation mode.

Introduced Version

Before V09R1

Enhancement

None

4.2.5 ZGB-03-02-005 Static Channel Management

Benefits

This feature provides basic channel management for GSM service.

Description

ZTE GSM BSS supports static channel and dynamic channel. This feature only

describes static channel management. For dynamic channel management, please refer

to ZGB-03-02-006 Dynamic Channel Management.

There are two kinds of static channels: static TCH and static PDCH. Static TCH is only

used for CS service, not PS service. Likewise, static PDCH is only used for PS service.

Introduced Version

Before V09R1

Enhancement

None

4.2.6 ZGB-03-02-006 Dynamic Channel Management

Benefits

This feature provides flexible channel management to improve channel resource

utilization.



Description

ZTE GSM BSS supports static channel and dynamic channel. This feature only

describes dynamic channel management. For static channel management, please refer

to ZGB-03-02-005 Static Channel Management.

With this feature, BSS allocates channel dynamically to CS service or PS service based

on traffic load. Dynamic channels are allocated to CS service while CS traffic load is high

or allocated to PS service while PS traffic is high. If CS and PS traffic are both high in the

same time, the dynamic channel is assigned to CS service with priority. For dynamic

channel allocation priority of PS service, please refer to ZGO-03-02-009 Flexible Priority

Handling of Packet Data Channel.

Introduced Version

Before V09R1

Enhancement

None

4.2.7 ZGO-03-02-001 Idle Channel Measurement

Benefits

This feature improves network quality and user satisfaction by providing interference

measurement result to assign suitable channel to establish new calls.

Description

BTS measures the idle channels interference level and classifies the results into 5 levels,

then reports it to BSC.

The channel with lowest interference level is considered to be the best. During the

channel assignment procedure, BSC assigns the channel with lowest interference level

first. For example, channel with degree 1 is assigned first, then degree 2, 3, 4, 5.

Introduced Version



Before V09R1

Enhancement

None

4.2.8 ZGO-03-02-002 Enhancement on CS Channel Allocation

Benefits

With this feature, levels for different users or applications will be in the initial cut into

channel management to ensure maximum utilization of spectrum resources.

Different allocation functions have different emphases in order to improve network

stability and system capability.

The operator can optimize the network with customized parameters.

Description

This feature supports following channel allocation methods.

Channel allocation on speech channel with different rates

Several channel allocation manners can be selected in order to control and use the FR

and HR channels flexibly. The system supports channel allocation according to the

subscribers priority.

The optional priority based managements are as following:

FR priority

HR priority

Only FR channel to be allocated

Only HR channel to be allocated

Transceivers selected according to priority

Transceivers are separated into five classes according to the radio parameter and the



channels in the transceivers: 1 is the highest priority, 5 is the lowest priority and the

default value is 3. The priority is configured in OMCR, and the BCCH transceivers are set

as the highest priority 1 and other transceivers are set 2 to 5 according the priority in

general condition. The channels of transceivers with high priority are selected by the

system first.

Channel Allocation on TRX Priority

The TRX priority is divided into five levels: level 1 to level 5. Level 1 is the highest priority.

BSS always prefers to allocate the high priority TRX when MS requests to access the

network. TRX priority is set by operator on OMCR.

Channel allocation on interference band

The BTS measures the receiving level values of idle channels, and calculates the

average value in the measurement period (480 ms). It converts the interference

averages to the information of corresponding interference bands and sends it to BSC.

The BSC classifies the interference bands of the channel into five levels: level 1 to level 5.

For details, see ZGO-03-02-001 Idle Channel Measurement.

The channel interference affects the key indices of this channel, such as call quality, call

completion ratio, call drop rate, and handover completion ratio. Therefore, the

interference band information of the channel is a major factor which should be

considered preferentially in the enhanced channel allocation. Low-interference channel

is preferred in the channel allocation. For example, channels with level 1 interference

band will be assigned with priority, followed by level 2, 3, 4, and 5 orderly.

When problems such as radio channel cause the channel exception release, the BSC

sets the interference band of the channel to 0, and sets a punishment period in which the

interference band will not be updated. It acts as an assignment history record to affect

the current channel allocation, that is, the channel with interference band 0 will be

assigned at last in the channel allocation.

Channel allocation on TRX priority

The enhanced channel allocation algorithm sorts the intra-cell carriers by the background

configuration parameter Same Type Carrier Allocation Priority (carrier with high priority

precedes). The priority is divided into five levels: level 1 to level 5. Level 1 is the highest



priority.

Channel allocation on intra-cell handover

When handover is caused by the interference in the uplink or downlink, the channel in

the different transceivers is selected in priority. As the origin of the handover decision is

interference, in another word, there is interference in the current transceivers, the

possibility of interference on the other channels in the transceivers is large. Then the

channels on other transceivers are allocated according to priority, which improves the

handover success rate.

Channel allocation on reserved channel

When service with high user priority is used, the system is allowed to set several

reserved channels.

The difference from eMLPP is that in this feature, channels are reserved only for high

priority subscribers, but in the feature of eMLPP, the channel is not reserved, all the

subscribers can use the channel, but high priority subscriber will be allocated first when

congests.

To control the utilization of the reserved channels flexibly and satisfy the demands of the

different subscribers, system provides two ways: reserved channels are allocated in

priority; and other channels are allocated in priority. High priority subscribers can select

normal channels allocation in priority or reserved channels allocation in priority. The

purpose is to decrease the risk of call failure because of the network congestion.

Introduced Version

Before V09R1

Enhancement

None

4.2.9 ZGO-03-02-003 Enhancement on PS Channel Allocation

Benefits



Enhanced PS channel allocation improves PS users throughput, increases frequency

efficiency, and enhances system performance and capacity.

The operator can optimize the network with customized parameters.

Description

This feature supports following channel allocation methods.

Channel allocation on Guarantee Bit Rate (GBR)

PCU allocates the channel resource to fulfill the GBR of streaming or conversational

service. When current available resource is hard to satisfy the GBR, PCU tries empty

and queue as eMLPP. For empty and queue on GBR service, please refer to

ZGO-01-02-004 Streaming Service Policies.

Channel allocation on users throughput maximum

PCU allocates channel resource as much as possible according to the MS multi-slot

class and system capacity, increasing user throughput.

Channel allcocation on TRX load

BSS limits TRX number that allocated to MS by TRX load, avoiding PS service occurred

TRX overly. New TRX will be allocated for PS service only when service TRX load

exceeds the load threshold. With this way, BSS balances the CS/PS service and

resource.

Channel allocation on EGPRS/GPRS scheduling conflict

When the GPRS uplink and EDGE downlink multiplex the same radio channel, the EDGE

downlink rate will be limited due to the limitation of coding method (8PSK to GSMK). In

order to avoid this scenario, BSS allocates the channel considering the conflict

preferentially, and assigns the channel to MS without conflict.

Channel allocation on PDCH preference

For PS service, BSS allocates the channel with following order. Firstly, allocate static

PDCH; secondly, allocate dynamic channel with PS preference; and last, allocate other

dynamic channel. This method improves the utilization on static and PS preference

channel, reduces requirement on the other dynamic channel and avoids the PDCH



preemption by CS service when traffic load is high. For PS preference dynamic channel,

please refer to ZGO-03-02-009 Flexible Priority Handling of Packet Data Channel.

Channel allocation on TRX priority

The TRX priority is divided into five levels: level 1 to level 5. Level 1 is the highest priority.

BSS always prefers to allocate the high priority TRX when MS requests to access the

network. TRX priority is set by operator on OMCR.

Introduced Version

Before V09R1

Enhancement

None

4.3 Circuit Management

4.3.1 ZGB-03-03-001 2M High Speed Signaling Link

Benefits

This feature extends the bandwidth of system signaling link on A/Ater interface, and

meets the requirement of large capacity networking.

Description

In GSM network, the signaling link between different signaling points is identified by the

Signaling Link Selection (SLS) field of signaling routing label. This field has 4 bits, which

means there are maximal 16 signaling links between two signaling points. When the

narrowband 64Kbps signaling link is used, the total bandwidth between BSC and MSC is

only 16*64Kbps. It limits the processing capacity of one BSC.

ZTE BSS system supports 2Mbps high speed signaling link. In one 2M signaling link,

TS0 is used for synchronization; TS1-TS31 is combined as one signaling link with

1.984M bandwidth. Maximal 16 high speed links can be configured for one signaling



point pair. It extends the bandwidth of signaling link and meets the requirement of large

capacity networking.

Introduced Version

Before V09R1

Enhancement

None

4.3.2 ZGB-03-03-002 Enhanced E1 Link between BSC and BTS

Benefits

This feature enhances E1 transmission function (the number of E1 link, E1 link distance,

and E1 link impedance).

With this feature, network planning and implementation becomes easier.

Description

Enhanced E1 link between BSC and BTS supports the 75and 125impedance input.

This feature enhances E1 transmission, supports 2km-transmission or even longer

distance with unbalanced E1.

This feature supports more E1 links, as many as 16 E1 links.

This feature also supports automatic bridge function of E1 interface. For example, in

chain network, if BTS interface fails, E1 interface can hop to next BTS interface unit

automatically to ensure the normal function of other BTSs.

Introduced Version

Before V09R1

Enhancement

None



4.3.3 ZGB-03-03-003 LAPD Cluster

Benefits

This feature saves the transmission resource of Abis interface, especially for large

capacity sites.

Description

After this feature is deployed, all LAPD signaling of one site is multiplexed on several

64kbps time slots rather than allocating one LAPD time slot for one TRX. According to

the LAPD signaling traffic, 1 to 4 64kbps time slots are allocated to one site. This feature

enhances the LAPD processing capability of BSC and saves the transmission of Abis

interface.

If a site has two racks, the LAPD links of the two racks are multiplexed together. The time

slots used for LAPD cluster work in load-sharing mode. When one of the time slots fail,

the signaling on other time slots are not affected.

The detailed bandwidth requirement of LADP Cluster is shown in following table.

Table 4-1 Bandwidth Requirement of LADP Cluster

TRX

Number

Timeslot

Number Bandwidth

Peak Rate of

Signaling

6 1 64kbps 0~30kbps

7~16 2 128kbps 30~75kbps

17~26 3 192kbps 75kbps~120kbps

27~36 4 256kbps 120kbps~180kbps

Introduced Version

Before V09R1

Enhancement

None



4.3.4 ZGB-03-03-004 TC Resource Dynamic Sharing

Benefits

This feature makes the configuration of TC irrelevant to the codec types and distribution

of MSs in the network. As a result, the configuration of TC is simplified and the hardware

cost of TC is reduced.

Description

ZTE BSS TC unit supports 5 codec types: FR/EFR/HR/AMR-FR/AMR-HR. And the

processing ability for these codec types is the same.

When a call is initiated, the MS reports its bearer capability and the Class Mark to the

network. MSC informs BSS of the voice rate and voice codec type supported by this MS

in Assignment Request or Handover Request message. BSC chooses a codec type for

this call and allocates TC resource.

ZTE BSS TC resources are not allocated to radio channel resource statically, but are

shared by all radio channels. As a result, TC configuration is irrelevant to the distribution

of MSs in the network.

If Remote Transcoder feature is deployed, TC resources are dynamically shared not only

in one BSS, but also in multiple BSSs.

Introduced Version

Before V09R1

Enhancement

None

4.3.5 ZGB-03-03-005 PCU Resource Dynamic Allocation

Benefits

PCU resource dynamic sharing saves the PCU resources, reduces the cost of PCU

resource, and saves investment. With this feature, cell and PCU resources are not



fixedly mapping anymore. When some of the PCU processing resources break down, the

PS service of cell attached on the processing resource will be dynamically switched to

other processing resources, which increases reliability of PCU.

Description

PCU process resources are dynamically allocated to cell when BSS is initialized. If a

PCU process resource fails, the system attaches new PCU process resource to take

over the fault process. When fault process is recovered, the system re-assigns the cell

with load balance.

BSS performs dynamic allocation when the target process fulfills the following conditions:

The process is working normally, no failure.

The number of cell serving this process does not exceed the maximum capacity.

The number of PDCH serving this process does not exceed the maximum capacity.

BSS selects the lowest load process to serve the cells one by one till every cell is

attached completely.

Introduced Version

V09R2

Enhancement

None

4.4 Reliability

4.4.1 ZGB-03-04-001 BSC Load Control

Benefits

This feature guarantees the BSS system stability during the traffic surge by means of

selective rejection of service requests.



Description

This feature deals with these 3 types of overload:

MSC overload: that is, when BSC receives OVERLOAD message via A interface;

Signaling overload: that is, when BSC application layer receives overload message

from BSC signaling transportation layer;

CPU overload: that is, when BSC detects that the CPU usage is too high.

In overload cases, BSC applies the following 2 methods to reject some service requests

to maintain system stability:

Access class control: that is, stop some MSs from accessing the network by sending

(Access Control Class N ACCN) in system information

FUC control: that is, the FUC module of BTS stops some MSs from accessing the

network according to the RACH random value of MSs

The BSC load control function adopts ZTE patent algorithm.

Introduced Version

Before V09R1

Enhancement

In V10R1 BSC load control is enhanced by paging flow control and BHCA control.

There are two methods used to do paging flow control.

Priority based paging flow control; BSC will discard paging messages of low priority

subscribers when CPU load reaches the threshold set via OMC-R

Paging message number based flow control; BSC sets the threshold that how many

paging can be dealt with, if paging messages reach this threshold, new paging

messages will be discarded.

BHCA control, channel request threshold can be set via OMC-R, when BSC receives

more channel requests from Abis, new request received later will be discarded.



4.4.2 ZGB-03-04-003 BTS Recovery

Benefits

This feature enables BTS to restore the service immediately after the recovery of broken

Abis transmission link. It reduces the service outage time.

Description

BTS detects Abis status automatically and sets the service status as block after Abis

transmission is broken. When Abis transmission recovers, BTS applies parameter

refresh for BSC and checks the parameter with that locally set. After the check, BTS sets

the service status as unblock. Thus the service recovers.

Introduced Version

Before V09R1

Enhancement

None

4.4.3 ZGB-03-04-004 Dry Contact Alarm

Benefits

With this feature, system monitors other equipments to ensure the BSS system stability.

Description

With this feature, BTS provides Dry Contact Alarm input and output interfaces. BSC can

monitor whether other equipments are functioning well without extra transmission.

Alarm type includes water alarm, fire alarm, smoke alarm and intruder alarm, etc. All

these alarm signals are connected with BTS through Dry Contact Alarm connector. BTS

collects these alarm messages, and sends to BSC. The OMCRs Alarm Management

terminal shows these alarms.

Operator can define Dry Contact Alarm type in alarm management module.

Introduced Version



Before V09R1

Enhancement

None

4.4.4 ZGB-03-04-006 Backward Compatibility for BTS

Benefits

This feature saves the investment on upgrading and reduces the impact on the existing

network.

Description

BTS reports current software version to BSC via Abis interface after reboot. This

procedure helps BSS to keep compatible to all previous versions of BTS. BTSs of

different versions can co-exist in the same network.

The operator can upgrade BSC and some BTSs to deploy new features in some area

without upgrading the BTSs in other parts of the network.

Introduced Version

Before V09R1

Enhancement

None

4.5 GPRS/EDGE

4.5.1 ZGB-03-05-001 Coding Scheme CS1~CS4

Benefit

This feature provides basic Packet Service for GPRS network.

Description



GPRS offers a number of coding schemes with different levels of error detection and

correction. Network can choose the Coding Scheme depend on data rate requirement

and radio channel quality. There are CS-1, CS-2, CS-3 and CS-4 four types of coding

scheme, CS-1 has the strongest error correction capability and has lowest requirement

for radio environment, but it offers the minimum data throughput. To the opposite, CS-4

offer highest data throughput and have the weakest error correction capability, so it

needs highest C/I.

The following data rates are calculated theoretically based on the selected coding

scheme depending on C/I:

Table 4-2 Coding Scheme CS1-CS4

Coding Scheme CS-1 CS-2 CS-3 CS-4

Modulation GMSK GMSK GMSK GMSK

Data throughput per timeslot

(kbps) 9.05 13.4 15.6 21.4

RLC/MAC data throughput per

timeslot (kbps) 8 12 14.4 20

CS-1: This coding scheme applies for the highest level of error detection and correction.

It is used in scenarios when interference levels are high or signal levels are low. When

applying CS-1, data is not necessarily been re-sent too often. CS-1 uses 1/2 encoder,

and results in data throughput of 9.05 kbps.

CS-2: This coding scheme is used for better channel quality. It effectively uses a 2/3

encoder and results in data throughput of 13.4 kbps.

CS-3: This coding scheme uses 3/4 encoder, to result in 15.6kbps data throughput.

CS-4: This coding scheme is used in good channel condition which has very weak

interference, without error correction it can result in 21.4kbps data throughput. So for MS

using maximum 8 timeslots, 171.2kpbs data throughput can be achieved.

Introduced Version

BeforeV09R1



Enhancement

None

4.5.2 ZGB-03-05-002 Initial Coding Scheme Per Cell Settable

Benefit

This feature offers operator capability to set initial coding scheme of MS based on

network condition. The coding scheme settable can provide MS with optimized access

data rate and make full use of network resources.

Description

The initial coding scheme of PS user assignment can be set from OMCR based on cell

level, by cell level configuration to differentiate GPRS and EGPRS service parameters.

When the MS set up the Temporary Block Flow (TBF) connection, the link quality and C/I

are reported to BSC after a period of time, during which the MS will use the coding

scheme initially settled by the network. And after the period, the coding scheme will be

optimized according to the quality information reported by the MS and BTS.

By analyzing the overall channel quality condition, network user can set an initial coding

scheme which is very close to optimal coding scheme for the cell. It can reduce the time

to adjust to the optimal coding scheme and increase the data rate.

Introduced Version

BeforeV09R1

Enhancement

None

4.5.3 ZGB-03-05-005 8/11 bit Access Burst

Benefits

8 bit access is the primary access mode of PS service and 11 bit access shortens the

access delay and increases the throughput of EGPRS MS, thus improving subscriber



satisfaction.

Description

Two types of packet random access burst are supported in GERAN network: 8 bits

random access burst and 11 bits random access burst called the extended packet

random access burst. The MS shall support both random access bursts. 8 bit access is

the primary access burst; 11 bit access burst includes extend parameters such as MS

multi-slot class, thus can use one phase access to reduce the access delay. BSS

broadcasts the access type in system message PSI1, PSI13 and SI13 to indicate which

access type MS shall adopted.

Please refer to ZGB-03-05-007 One Phase Access for the description on the one

phase access.

Introduced Version

Before V09R1

Enhancement

None

4.5.4 ZGB-03-05-006 Class A, B, C MS

Benefit

This feature provides support for PS basic service.

Description

Not all GPRS/EDGE mobiles are designed to offer the same levels of service. In fact they

are split into three basic categories according to their capabilities to connect to GSM and

GPRS/EDGE network. GPRS/EDGE network can support the three types of mobiles

connection and provides differentiated services to different types of MSs. The three types

of mobiles are Class A, B and C, which are described as the following:

Class A: This class describes mobile phones that can be connected to both

GPRS/EDGE and GSM services at the same time.



Class B: This class mobile can be attached to both GPRS/EDGE and GSM services but

they can be used with only one service at a time. A Class B mobile can make or receive a

voice call, or send or receive a SMS message during a GPRS/EDGE connection. During

voice call or SMS session, the GPRS/EDGE service will be suspended and will be

re-established automatically after the voice call or SMS session is completed.

Class C: This classification covers mobiles that can be attached to either GPRS/EDGE

or GSM services but user needs to switch manually between the two different types.

Introduced Version

Before V09R1

Enhancement

None

4.5.5 ZGB-03-05-007 One Phase Access

Benefit

This feature provides support for PS basic service, to allow MS with certain capability to

quick access to packet network, to reduce latency.

Description

The packet access procedure using CCCH may be used to establish a Temporary Block

Flow (TBF) to support the transfer of LLC PDUs in the direction from MS to network or

from network to MS. For the uplink direction, there are two types of packet access: one

phase access and two phase access.

One phase access reduces initial TBF setup time by reducing signaling procedure and to

improved packet access speed. MS initiates one phase access mode and requests one

phase access in the Channel Request or Packet Channel Request message. Network

sends MS a packet uplink assignment message carrying information about resources

allocated to MS. Resource competition may be happened when different MSs request

the channel at same time. To handle the competition, the MS is asked to send the TLLI in

the begin RLC block after it receives the uplink assignment message. After receiving the



first RLC block, network side will fill the TLLI in PACKET UPLINK ACK and send to MS.

MS receives this ACK message and get the TLLI value. If this TLLI value is identical with

its own value sent to network side, it means the radio resource is allocated to this MS.

Then the one phase access procedure is completed, MS turns to packet transfer mode.

One phase access can be used directly if the requested RLC mode is acknowledged

mode and the amount of data need to be transferred is less than 8 RLC/MAC blocks.

Normally, MS requests one phase access when transmitting paging response, cell

update and MM layer messages through TBF establishment by this feature, MS with one

phase access conditions can quick access to GPRS/EDGE network to have improved

performance on latency.

Introduced Version

BeforeV09R1

Enhancement

None

4.5.6 ZGB-03-05-008 Two Phase Access

Benefit

This feature provides support for PS basic service, to ensure GPRS/EGPRS capable MS

access to network.

Description

The packet access procedure using CCCH may be used to establish a Temporary Block

Flow (TBF) to support the transfer of LLC PDUs in the direction from MS to network or

from network to MS. For the uplink direction, there are two types of packet access: one

phase access and two phase access, they are chosen based on MS access reason or

network can force MS to use two phase access.

Two phase access has complex signaling procedure than one phase access. If two

phase access is initiated by MS, MS send two phase access request in the Channel

Request or Packet Channel Request message. The network sends a Packet Uplink



Assignment message containing single block assignment to MS to instruct second

phase access. Then MS sends a Packet Resource Request message on the allocated

single block. Upon receiving the message, the network returns a Packet Uplink

Assignment message in response. The competition solution on the network side ends

after the network receives TLLI used to identify MS. After MS receives the Packet Uplink

Assignment message, the competition solution on the MS side also ends if TLLI in this

message is identical with that in the Packet Resource Request message from MS. After

the competition solution succeeds, two phase access procedure ends and MS switches

to packet transmission mode. System can also be configured as Force Two Phase

Access, the network will force MS to adopt two phase access mode after receiving the

Channel Request or Packet Channel Request message from MS and ignore the

request reason of MS. Comparing with one phase access, by the second phase access,

network can acquire the MS capability such as Extended Uplink TBF Mode etc.; by the

information to effectively allocate radio resources.

The two phase access will be used in situations when the requested RLC mode is

unacknowledged mode or the RLC mode is acknowledge mode and the data need to be

translated is more than 8 RLC/MAC blocks. In addition, for EGPRS TBF mode capable

MSs (in an EGPRS capable cell), if the cell does not support EGPRS PACKET

CHANNEL REQUEST, then MS has to use two phase access no matter acknowledge

mode or unacknowledged mode.

Introduced Version

BeforeV09R1

Enhancement

None

4.5.7 ZGB-03-05-009 Network Mode of Operation (NMO) 1~3

Benefits

Based on the mode of operation provided by the network, the MS can choose, according

to its capabilities, to attach to GPRS/EDGE services, to non-GPRS/EDGE services, or to

both.



Description

According to 3GPP standards, three network operation modes are defined.

Network operation mode I: the network sends a CS paging message for a

GPRS-attached MS, either on the same channel as the PS paging channel (i.e., the

packet paging channel or the CCCH paging channel), or on a PS traffic channel.

This means that the MS needs only to monitor one paging channel, and that it

receives CS paging messages on the packet data channel when it has been

assigned a packet data channel.

Network operation mode II: the network sends a CS paging message for a

GPRS-attached MS on the CCCH paging channel, and this channel is also used for

PS paging. This means that the MS needs only to monitor the CCCH paging

channel, and that CS paging continues on this paging channel even if the MS has

been assigned a packet data channel.

Network operation mode III: the network sends a CS paging message for a

GPRS-attached MS on the CCCH paging channel, and sends a PS paging

message on either the packet paging channel (if configured in the cell) or on the

CCCH paging channel. This means that an MS that wants to receive paging for both

circuit-switched and packet-switched services shall monitor both paging channels if

the packet paging channel is configured in the cell. No paging co-ordination is

performed by the network.

Table 4-3 Three Network Operation Modes

Mode Circuit Paging Channel PS Paging Channel Paging

Co-ordination

I

Packet Paging Channel Packet Paging Channel

Yes CCCH Paging Channel CCCH Paging Channel

Packet Data Channel Not Applicable

II CCCH Paging Channel CCCH Paging Channel No

III CCCH Paging Channel Packet Paging Channel

No CCCH Paging Channel CCCH Paging Channel

When the Gs interface is available, all MSC-originated paging of GPRS-attached MSs



shall go via the SGSN, thus allowing network co-ordination of paging. Paging

co-ordination shall be made by the SGSN based on the IMSI, and is provided

independently of whether the MS is in STANDBY or in READY state. The network

operates in mode I.

When the Gs interface is not available, all MSC-originated paging of GPRS-attached

MSs shall go via the A interface, and co-ordination of paging cannot be performed. The

network shall then either:

operate in mode II, meaning that the packet common control channel shall not be

configured in the cell; or

operate in mode III, meaning that the packet common control channel shall be used

for PS paging when the packet paging channel is configured in the cell.

The network operation mode (mode I, II, or III) is indicated in system information to

MSs. For proper operation, the mode of network operation should be the same in all

cells of a routing area.

Introduced Version

Before V09R1

Enhancement

None

4.5.8 ZGB-03-05-011 Timeslot Multiplexing

Benefits

PS service has different timeslot allocation strategies from voice service, which helps to

improve efficiency of timeslot.

Description

PS timeslot allocation is different from voice service. The time slots for uplink and

downlink voice are allocated simultaneously and they will be used exclusively by a MS till

the call is terminated to release them. While PS time slots are allocated on uplink and



downlink respectively according to data transfer requirements. And several MSs are able

to use one time slot simultaneously to maximize the timeslot efficiency.

Introduced Version

Before V09R1

Enhancement

None

4.5.9 ZGB-03-05-012 GPRS Link Adaptation

Benefits

This feature improves the adaptation of the link and increases the system throughput

efficiently.

Description

The link adaptation algorithm compares the estimated channel quality with threshold

preset in the OMC-R in order to select appropriate coding scheme. According to different

evaluated parameters: C/I, BLER and BER, different link adaptation algorithm models

are designed

The threshold consists of the switching points between four coding schemes: CS-1, CS-2,

CS-3 and CS-4. It is set in BSC parameters settings. These switching points between

coding schemes are configurable, to make the user choose an optimal link adaptation

algorithm model according to the overall conditions of channel quality, hence improving

the efficiency of link adaptation.

Introduced Version

Before V09R1

Enhancement

None



4.5.10 ZGB-03-05-013 Delayed TBF Release in DL

Benefits

When the PS channel carries the burst IP traffic, it sets up and releases the radio

resource frequently, while TBFs release and setup takes some time and occupies radio

interface resource, which causes high signaling load and decreases the data transfer

efficiency. The delayed TBF release in DL avoids the unnecessary procedure of TBF

setup and release so as to improve the GPRS data transfer performance.

Description

When BSS sends the last RLC block, FBI is not set to 1, and the idle BIT in the RLC

block is filled with filling bit, sending the virtual LLC frame periodically to keep connection.

After a period of time, if it doesnt yet have any new downlink or uplink traffic request, the

connection will be released. Otherwise it will transfer the data over the existing RLC link

immediately.

Introduced Version

Before V09R1

Enhancement

None

4.5.11 ZGB-03-05-014 Delayed TBF Release in UL

Benefits

This feature speeds up the establishment of downlink TBF and improves the user

experience.

Description

Usually, BSS starts releasing an uplink TBF when MS sends a RLC block with CV=0

indicating there is no uplink data to be sent.



With Delayed TBF Release in UL feature, when BSS receives RLC block with CV=0 sent

by MS, if MS or BSC do not support Extended Uplink TBF Mode, and there is no

downlink TBF exists for this MS, then BSC starts a timer. Before this timer expires, if

there is downlink data, a downlink TBF is established via PACCH. Because establishing

a TBF via PACCH is more simple and more quickly than establishing a TBF via CCCH,

this feature speeds up the establishment of downlink TBF and improves the user

experience. When the timer expires, the uplink TBF is released. This feature is

implemented by BSC software and does not require MS modification.

Introduced Version

Before V09R1

Enhancement

None

4.5.12 ZGB-03-05-015 RLC Acknowledged/ Unacknowledged Mode

Benefits

The feature is the basis for introduction of PS service.

Description

ZTE GSM BSS support two RLC modes defined in 3GPP: RLC acknowledged mode and

RLC unacknowledged mode.

RLC acknowledged mode: each data block transmitted on the TBF should be

acknowledged by receiver. The sender shall resend the blocks indicated lost by receiver.

TBF cant be released until each data block transmitted on the TBF is complete and

acknowledged. This mechanism ensures the transmission reliability of the RLC data

blocks.

RLC unacknowledged mode: the receiving party acknowledges the received RLC data

blocks as in RLC acknowledged mode. The data block, however, is not required to be

resent by sender. The TBF is released after the data transmission is complete although

maybe some data are lost during the transmission.



The RLC mode of the uplink TBF is dependent on the service type requested by the MS

and the RLC mode of the downlink TBF is dependent on the RLC mode in the QoS

parameters contained in the downlink LLC PDU.

Introduced Version

Before V09R1

Enhancement

None

4.5.13 ZGB-03-05-016 Downlink BVC Flow Control

Benefits

This feature is a basic feature of PS services. The BVC flow control mechanism controls

the loading of the BSS LLC PDU queues per BVCI between SGSN an

ZTE GSM BSS UR11.2 Basic Feature Description

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