microsoft power point - 2 omf010001 system information issue1

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System Information

Contents

1. System Information Overview

2. Parameters Introduction

3. Case Study

System Information Overview

� System information (SYS INFO) contains network parameters

sent to MS through Um interface

� network identity parameters

� cell selection parameters

� system control parameters

� network function parameters

� System information can be sent through two kinds of logical

channels

� System information on BCCH

� System information on SACCH

Contents

3. Case Study

Introduction to SYS INFO Parameters

� Huawei GSM System Information Parameters:

� Network Identity Parameters

� System Control Parameters

� Cell Selection Parameters

� Network Functional Parameters

Network Identity Parameter — CGI

� Network identity parameters mainly include cell global identity

(CGI) and base station identity code (BSIC).

CGI=MCC+MNC+LAC+CI

� Once MS receives SYS INFO, it decodes the CGI information, and

decides whether it can stay in the cell according to the MCC and

MNC indicated by CGI. At the same time, it judges whether the

current location area is changed, so as to decide whether to

execute location update. During the location update process, MS

will report the new LAI to the network, so that the network can

know the LA in which MS is currently located.

Network Identity Parameter — BSIC

� BSIC=NCC+BCC

� In GSM system, each BTS is allocated with a color code, which is

called BSIC. MS can identify two cells with the same BCCH by the

help of BSIC. In network planning, effort should be made to make

sure that BCCH of neighbor cells are different from the serving

cell’s BCCH to reduce the interference. Practically it is still

possible that a same BCCH is re-used in the surrounding cells.

For cells using the same BCCH in a relevant near distance, their

BSIC must be different so that MS can identify two neighbor cells

with same BCCH.

Mobile Country Code（MCC）

� Definition

� MCC consists of 3 decimal numbers. It indicates the home

country of the mobile subscriber.

� Format

� MCC is composed of 3 decimal numbers. The coding range is

decimal 000-999.

Mobile Network Code（MNC）

� Definition

� MNC is used to uniquely identify a specific GSM PLMN

network in a certain country (decided by MCC).

� Format

� MNC is composed of two decimal numbers. The coding range

is decimal 00-99.

Location Area Code（LAC）

� Definition

� To locate the location of MS, the whole area covered by each

GSM PLMN is divided into different location areas. LAC is used

to identify different location areas.

� Format

� LAI contains LAC, which is composed of two bytes. LAC

adopts hexadecimal coding. The available range is from 0001H

to FFFEH. The code 0000H and FFFFH cannot be used

(please refer to specification GSM0303, 0408, and 1111). One

location area can contain one or more cells.

Cell Identity（CI）

� Definition

� To uniquely identify each cell in the GSM PLMN, the network

operator needs to allocate one code for each cell, which is the

cell identity (CI). Cell identity, together with LAI, is used for

identity of each cell in the world. (specification 0303).

� Format

� CI is composed of 16 bits, The available range is 0~65535.

Network Color Code（NCC）

� Definition

� NCC is a part of BSIC. MS uses it to distinguish adjacent BTS

that belong to different GSM PLMN.

� Format

� NCC is composed of 3 bits, with the range of 0 to 7.

BTS Color Code（BCC）

� Definition

� BCC is a part of BSIC. For its function, please refer to

above sections.

� Format

� BCC is composed of 3 bits. The available range is

from 0 to 7.

System Control Parameters� ATT (Idle Mode)

� CCCH_CONF (Idle Mode)

� BS_AG_BLKS_RES (Idle Mode)

� BS_PA_MFRAMES (Idle Mode)

� T3212 (Idle Mode)

� Neighbor Cell Description (Idle

Mode-BA1&Handover-BA2)

� NCC Allowed (Idle Mode)

� TX-Integer (Idle Mode)

� MS MAX Retrans (Call

Control)

� Radio Link Timeout (Call

Control)

� Common/ Special Access

Control Class (Call Control)

� MBR (Call Control)

� ECSC (Call Control)

� Value range: Yes, No

� Content：It is used to inform MS whether IMSI attach-

detach is allowed in this cell. If it is set to “Yes”, the network

will not process the connection to the called mobile

subscriber when MS is power-off. Thus network processing

time and radio resources are saved. Otherwise the network

will process the connection even though the MS has been

powered off.

� Recommendation：Yes

CCCH_CONF

� Value range: 1 Non-Compounding CCCH, 1 Compounding CCCH, 2

Non-Compounding CCCHs, 3 Non-compounding CCCHs, 4 Non-

compounding CCCHs.

� Content: It is “Common Control Channel Configuration”. CCCH

configuration determines the capacity of PCH, AGCH and RACH. This

parameter can be automatically configured by the BSC Data Auto

Configuration System according to the TRX channel configuration.

� Recommendation: When there is one TRX in the cell, one combined

CCCH is recommended (in a system with few paging messages in

location area). For others, it is configured according to the number of

TRX in the cell.

BS_AG_BLKS_RES

� Value range: 0~2 (1 combined CCCH), 0~7 (others)

� Unit: Block

� Content: It is also called Access Granted Blocks Reserved.

It is the number of CCCH channel message blocks that are

reserved in one multi-frame for access granted channels

(AGCH).

� Recommendation: 2 (non-combined CCCH)

BS_PA_MFRAMES

� Value range: 2～9

� Unit: Multi-frame period (51 frames)

� Content: It is Paging Channel Multi-frames. It defines the

number of multi-frames used as a cycle of paging sub-

channels.

� Recommendation: 2

� Value range: 0~255

� Unit: 6 minutes

� Content: It is the Periodic Location Update Timer. It defines the

interval of periodic location update.

� Recommendation: 30 (for urban area), 20 (for suburban area)

Definition of Location Update

�Inform the system the LA (Location Area) where the MS is to be paged.

Condition of Location Update

� Periodical location update

� Moving into a new LA

Procedure of Location Update

1 Hour 1 Hour 1 Hour

≥ ++ ++ +

Abnormal Occasion

But I am always powered on

The subscriber you dialed has been powered off

Reason1 of Abnormal Occasion

1 Hour 1 Hour1 Hour

Reason2 of Abnormal Occasion

1 Hour 1 Hour 1 Hour

Application of T3212

Even if T3212 setting is less than the system (MSC) query time, the system

will still sometimes voice “The subscriber you dialed is powered off”.

T3212=4 T3212=8

“Ping-pong Reselect”

Neighbor Cell Description

� There are table BA1 and table BA2.

� Table BA1 describes BCCH frequencies of the adjacent

cells to be measured when the MS is in idle mode.

� Table BA2 describes BCCH frequencies of the adjacent

cells to be measured when the MS is in dedicated mode.

Theoretical Neighbor Cells Actual Neighbor Cells

Application of Neighbor Cell Description

NCC Allowed

� Value range: Check box, including options 0~7.

� Content: Network Color Code, sent in system information 2

and 6. It lists NCC that need be measured by MS. If a

neighbor cell’s NCC is permitted, MS will report MRs of it to

the network.

� Recommendation: Subject to the concrete conditions.

MS MAX Retrans

� Value range: 1, 2, 4, 7

� Unit: Time

� Content: It is one of the random access control parameters. MS MAX

Retrans is the upper limit of times that MS is allowed to send “Channel

Request” in one immediate assignment procedure.

� Recommendation:

� Set to 7 for areas with low traffic (suburban or rural area) and the cell radius

more than 3 km.

� Set to 4 for areas with ordinary traffic (non-busy area in the city) and the cell

radius is less than 3km.

� Set to 2 for micro-cell

� Set to 1 for micro-cell with heavy traffic or with obvious congestion.

� Set to 4 or 7 for satellite transmission BTS.

TX-Integer

� Value range: 3~12, 14, 16, 20, 25, 32, 50

� Unit: RACH timeslot (equals to a TDMA frame, 4.615ms)

� Content: Used to calculate the number of timeslots in the

interval between multiple channel requests sent by MS.

� Recommendation: 20 (If the cell immediate assignment

success rate is low, set the S with a larger value. Select 32

for satellite transmission, so as to reduce satellite

transmission delay).

Calculation of S

STx-integer

Non-Combined CCCH Combined CCCH

3, 8, 14, 50 55 41

4, 9, 16 76 52

5, 10, 20 109 58

6, 11, 25 163 86

7, 12, 32 217 115

Radio Link Timeout

� Value range: 4~64, the step size is 4

� Unit: SACCH period (480ms)

� Content: This parameter is used for MS to decide down-link

disconnection in case of SACCH decoding failures.

� Recommendation: 20~56

Application of Radio Link Timeout

Impact of radio link timeout

Poor coverage

Common Access Control Class

� Value range: Check box, including level 0 forbidden,lever 1

forbidden,…, till level 9 forbidden

� Content: One of the parameters of random access control

information. It is used for load control of ordinary

subscribers, to permit or forbid the network access of some

common level users. “1” stands for forbidden and “0” for

permitted.

Special Access Control Class

� Value range: Check box, including level 11

forbidden,level12 forbidden,…, till level 15 forbidden

� Content: It is used for load control, permitting or forbidding

the network access of some special level users. “1” stands

for forbidden and “0” for permitted.

� Content: Multi-band Reporting. It is used to inform MS to

report the adjacent cells in a controllable way. It is sent in

the System Information 2ter and 5ter.

Application of MBR

-92dBm-82dBmA

C -68dBm

D -90dBm

E -78dBm

F -88dBm

G -96dBm

H -84dBm

GSM1800

GSM900S

� Content: Early Classmark Sending Control. It indicates if an

MS in the cell is allowed to use early Classmark sending.

See Protocol 0408.

� Recommendation: No.

Cell Selection Parameter

� CBQ (Cell Bar Qualify)

� CBA (Cell Bar Access)

� MS_TXPWR_MAX_CCH

� RXLEV_ACCESS_MIN

� PI (Cell Reselect Parameters Indication)

� CRO (Cell Reselection Offset)

� TO (Temporary Offset)

� PT (Penalty Time)

� CRH ( Cell Reselection Hysteresis)

Cell Selection Process

� There are two kinds of cell selection.

� Normal cell selection

� Stored list cell selection

� In fact, the process might be different for different MSs

Stored List Cell Selection

Search the BCCH

which have been

stored

Can not find it

Normal cell

selection

Can find it

Can reside in it

Can’t reside ,search

neighbor cell

Come into

idle mode

Normal Cell Selection

Search all frequency

Rank according to receiving level

Come into idle

Check whether this is a BCCH carrier, get

SCH and decode system information

PLMN, C1>0, priority is normal

Check next one

Normal Cell Selection

Check the next frequency by the same step

Check the cell which priority is low, C1>0,PLMN

Come into idle

modeTry the cell which PLMN is allowed

in the SIM card

Stay at a cell which RX-LEV is strongest,

C1>0 , cell priority is not prohibitedEmergency

call mode

Cell Selection Parameter

C1=RLA_C-RXLEV_ACCESS_MIN-

MAX((MS_TXPWR_MAX_CCH - P), 0)

RLA_C: Receiving level of MS

RXLEV_ACCESS_MIN: Minimum receiving level of MS permitted to access

P: Maximum Physical supported transmitting power of MS.

RXLEV_ACCESS_MIN

� Unit: Level

� Content: It means the minimum receive signal level

required for MS to access a cell.

MS TXPWR_MAX_CCH

� Unit: level

� Content: This parameter determines the maximum

allowed output power of the MS when it begins to

access a cell and has not yet received power

control command.

� Recommendation: 5(900MHz), 0(1800MHz)

� Value range: Yes , No

� Unit: None

� Content: Cell Bar Qualify. CBQ only affects the selection

of cells but is not related to cell reselection. It works with

CBA to define the access priorities of cells.

� Recommendation: No.

� Content: Cell Bar Access, worked together with CBQ to set

the priority status of the cell in idle mode for cell selection

and reselection.

� Recommendation: Yes

Application of CBA and CBQ

normallow11

normallow10

forbiddenforbidden01

normalnormal00

Cell reselectionpriority

Cell selection priorityCBQCBA

Application of CBQ

The traffic of cell A and B is heavy. Set these two cells with CBA=“1”, CBQ=“0”.

Application of CBA

B is a micro cell. Set B to “Normal” and A to “Low”.

Cell Reselection Process� Cell reselection for cells in same location area

� If the C2 value of the target cell is higher than that of the serving cell for longer

than 5 seconds, a cell reselection process will be performed and the MS tunes

to the new cell.

� Cell reselection for cells in different location areas

� If the C2 value of the target cell is higher than that of the serving cell by at least

the value of CRH for longer than 5 seconds, a location update process and the

cell reselection process will be performed.

� Two consecutive cell reselections caused by C2 have a time interval of 15

seconds. In other words to say, if because of C2 a MS reselected to a cell,

then the MS cannot reselect to another cell by the cause of C2 within 15

seconds.

� If current serving cell is prohibited, or down link fails, or C1 is less than 0

continuously for 5s, cell reselection will also be triggered.

� MS starts a cell reselection if the access times exceed the MAX retrans.

Cell Reselection Parameter

C2=C1+CRO-TO*H(PT-T) When PT is not equal to 31

C2=C1-CRO When PT is equal to 31

Function H(x)=0, when x<0; H(x)=1, when x>0

� Value range: Yes (1), No (0).

� Unit: None

� Content: Cell Reselect Parameters Indication, sent

on the broadcast channel of the cell. It is an

indication to the existence of “Cell Reselect

Offset(CRO)”, “Temporary Offset(TO)” and

“Penalty Time(PT)”.

� Value range: 0~63, the corresponding level value:

0~126dB, stepped every 2dB.

� Unit: None

� Content: Cell Reselect Offset. It is a parameter in

C2 calculation to give an intentional modification in

MS cell reselection.

� Value range: 0~7 , the corresponding value is

0~60dB, 7 corresponds to “Infinite”.

� Unit: None

� Content: Cell Reselect Temporary Offset. It is a

parameter in C2 criterion to give a temporary

modification within PT time.

� Value range: 0~31, the corresponding time is

20~620s. 31 is to change the formula of C2.

� Unit: None

� Content: Cell Reselect Penalty Time.

� Value range: 0~14 , the step size is 2

� Unit: dB

� Content: Cell Reselection Hysteresis. It is the parameter

used when cell reselection happens between two location

areas.

Network Function Parameter

� PWRC (Power Control Permitted)

� Other Attributes/Public Channel Control

� UL DTX (Uplink Discontinuous Transmission)

� Cell Attributes

� Call Re-establishment Forbidden (RE)

� Cell Attributes

� EC Disabled (Emergency Call Disabled)

� Call Control

� Value range: Yes, No.

� Unit: None

� Content: It is used to indicate MS weather to reduce received level

value obtained from the timeslots of BCCH when MS measures

receiving level during base band hopping mode. When it is set to

“No”, it means the influence of receiving level on BCCH is not in

consideration. If it is set to “Yes”, process it in the way mentioned

above.

UL DTX

� Value range: May use, Shall use, Shall not use.

� Unit: None

� Content: It is used to indicate whether MS uses DTX

function. In System Information 3, it is 2-bit coding. In

System Information 6, it is 3-bit coding. It shows the DTX

state of the MS in the previous measurement period.

� Recommendation: Shall use

Call Re-establishment Forbidden

� Unit: None

� Content: Informing MS whether call reestablishment is

allowed or not.

� Recommendation:Yes

EC Disabled

� Unit: None

� Content: Emergence Call Allowed . When EC Allowed is set

to “Yes”, it means emergency call is permitted. Otherwise it

is prohibited.

� Recommendation: No

Contents

3. Case Study

Case Study� Case 1: Island effect

� Case Description

� During the process of optimization in a certain area, it is found out

that the signal is poor in a certain section of suburban highway.

The signal strength measured is less than -95dBm.

� Handling Procedure

� Modify the data in BSC. Add neighbor relationship to Cell A and B

for each other. The coverage problem is thus solved.

Case Study� Case 2: Incorrect CGI causes MS unable to register on the network.

� Case description

� The subscriber complained that MS could not register to the network, or it was

difficult to register to the network between BTS A and B, or no network mark

was displayed on the MS, but MS indicated that the signal was very good.

Some subscribers also complained that MS could make MTC could not make

� Cause analysis

� CGI of the cell was modified. So the network register flow was not normal.

Although the signal was very good, MS could not get registered in the network.

� Recommendation and summary

� CGI is a very important parameter and should be configured correctly, thus to

ensured that the CGI data in BSC and MSC are the same.

Case Study

� Case 3: RXLEV_ACCESS_MIN causes signal fluctuation.

� Subscribers complain that the signal fluctuates in a certain area. On-site test shows

that this phenomenon does exist. From the testing mobile, we can see that there are a

lot of cells’ signals in this area. Some frequencies are the suburb BTS signals far

away from this area. The cell reselection of MS is rather frequent.

� Handling procedure

� Modify parameter “RXLEV_ACCESS_MIN” of all cells in urban area and make them

consistent with each other. The problem of signal fluctuation is solved.

� Recommendation and summary

� In area with complicated coverage, the “RXLEV_ACCESS_MIN” of each cell should

be kept same.

Case Study

� Case 4：Too small T3212 causes MS lose connection with

network.

� A local GSM network has more than 6000 subscribers. There are four

BTSs. The network has been working properly. But from sometime on,

some MS often lost connection with network suddenly. The complaint from

subscribers in urban area increased.

� Handling procedure

� Modify T3212 to 10, i.e. 60 minutes. Modify the corresponding time of MSC

to 180 minutes. Two days’ observation shows no subscriber complaint and

the problem is solved.

Thank youwww.huawei.com

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