System Information Overview

System Information verview By : Ahmed Atef Ibrahim

By Ahmed Atef Ibra im RF Engineer ahmed.atef@huawei. om [email protected] +2- 0100 8937017 +2- 0127 7588718

RF Integration Team ��

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System Information Overview By : Ahmed Atef Ibrahim

System Information System information (SYS INFO) contains network parameters sent to MS through Um interface  network identity parameters (CGI, CID)  cell selection parameters  system control parameters  network function parameters System information can be sent through two kinds of logical channels  System information on BCCH (IN the IDLE mode)  System information on SACCH (Dedicated mode)





fully utilize

Cell Selection & Reselection

Network

access

MS

_

various services provided by the network, and achieve favorable cooperation with the network SYS INFO : MS

BCCH

SYS INFO

SYS INFO 1, 2, 2BIS, 2TER, 3, and 4 Idle Mode

MS

SACCH

SYS INFO 5, 5BIS, 5TER, and 6 Dedicated Mode

Hint :

Additionally Huawei BSC supports supports the system information information 7 and 13 to support GPRS . BCCH system information information belongs to common common channel information. information. SACCH system information basically belongs belongs to TRX management information. information. Common channel and TRX management information should be selected in order to observe all the system information when tracing on the layer 3 messages of radio interface .

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SYS INFO 1



SYS INFO 1 



It contains random access control information (RACH) and cell frequency allocation table (i.e. CA table). It is transmitted on BCCH.

Content  SYS INFO 1 •

Cell Channel Description

(cell channel description format) •

RACH Control Parameter

(random access channel control parameter)



These control parameters include: 

Maximum re-transmitting times (MAX retrans) _ limit of times that MS is allowed to send Channel Request in one

immediate

assignment procedure 

Extended transmission timeslots (Tx_integer) _ calculate the number of timeslots in the interval between multiple channel requests sent by MS



Common access control level (AC) _ permit or forbid the network access of some common level users



Call reestablish permitted (RE) _ An option in GSM is to allow for a call reestablishment in case of a dropped connection . In these cases, frist a CHANG_REQ is sent to the BTS and then it is tried to with the CM_RES_REQ to reestablish an RR connection for the still existingand active MM and CC connection .



Emergency call permitted (EC) _ Enables the MS to make emergency calls in the uncovered areas

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SYS INFO 2 

SYS INFO 2 



It contains access control information (RACH), network color code permitted (NCC Permitted), and neighbor cell frequency allocation list (BA1 list). It is transmitted on BCCH. Generally speaking, SYS INFO 2, 2BIS, 2TER contains different parts of the neighbor cell’s BCCH frequencies. Via reading and decoding BA1 list, MS can perform cell reselection in idle mode. For a MS of GSM900 PHASE I, it only reads the neighbor cell BCCH frequencies defined in SYS INFO 2, and ignores those carried by 2BIS and 2TER.

Content  SYS INFO 2  Neighbor Cell BCCH Frequency Description  NCC Permitted  RACH Control Parameter

Neighbors

NCC

RACH

Serving Cell

SYS INFO 2

Band

SYS INFO 2

Neighbor BCCHs 1800

SYS INFO 2TER SYS INFO 2 &

900

band

support

SYS INFO 2BIS & 2TER

SYS INFO 2BIS

Neighbor

Parameter

BCCHs frequencies

SYS INFO 2 & 5 BA List

. BCCHs

MS

Extended indication (EXT_IND)

Neighbor

_

5

0

( serving Cell

.1

band

SYS INFO 2 & 5

BA table indication (BA_IND)

BA 1

data

MS

1

_ BCCHs

Parameter 1

0

current neighbor cell relationship and BA2 table 1 �

BA_IND

dedicated mode

0 ) BCCHs

BA List SYS INFO 2 &

_

_ 5

BA 2 MS � ��


system information 5

neighbor cell frequency latest information

re-decode

MS

(maybe also 5BIS and 5TER)

Hint :

Network Color Code Permitted (NCC Permitted) is transmitted on system information 2 and 6. It has eight bits.The eight bits are used to show if the particular NCC codes are permitted for the MS to access. If bit N is set to “0” (0<=N<=7), the MS will not measure the BCCH of the cell with NCC=N at all. Thus, the MS will not be handed over to the cell with NCC=N.

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SYS INFO 2BIS



SYS INFO 2BIS 



2BIS contains RACH control data and neighbor cell’s BCCH frequencies (part of BA1 list). It is optional and transmitted on BCCH. As the number of frequencies in BA1 list carried by SYS INFO 2 is limited, SYS INFO 2BIS carries the rest of the BCCH frequencies in the BA1 list that are from the same band as in SYS INFO 2. Content  SYS INFO 2BIS − Neighbor Cell Description. − RACH Control Parameter (Same as those in SYS INFO 1)

SYS INFO 2 band

BA1 List ) SYS INFO 2BIS

Frequencies

_

BCCH frequencies ( serving Cell

Hint :

_ Currently Huawei GSM BSS supports up to 32 neighbor cells. And for GSM900 cells all these 32 neighbor cells’ BCCH ARFCNs can be transmitted via System Information 2 by using the format of bitmap. Therefore, BA1 table can be completely delivered to the MS using system information 2. So, it is not necessary use System Information 2BIS. _ For GSM1800 cell, when the number of configured neighbor cells with the same band is more than 16, it will send system information 2BIS.

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SYS INFO 2TER



SYS INFO 2TER

2TER contains neighbor BCCH frequencies (part of BA1 list). It is transmitted on BCCH. Only dual band MS can read this information, and single band 900 or 1800 MS will ignore it. Since this information carries BCCH frequencies that belong to different band other than those in SYS INFO 2, it is unnecessary for single band MS to read. Content  SYS INFO 2TER − Neighbor Cell Description (extended) 



band Two Band 900 &

Neighbor BCCH frequencies support

MS . ignore it

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_

INFO support one band

Serving Cell MS

( 1800 )

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SYS INFO 3 

SYS INFO 3 •



It contains LAI, cell identity, RACH control parameters and cell selection related parameters. It is transmitted on BCCH. It is one of the most important information.

Content •

SYS INFO 3 •

Cell Identity

•

LAI (location area identity)

•

Control Channel Description

•

Cell Option



Cell Selection Parameter

•

RACH Control Parameter

Cell Identity and Location Area Identity 

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Cell Global Identity (CGI) consists of Location Area Identity (LAI) and Cell Identity (CI). And LAI includes Mobile Country Code (MCC), Mobile Network Code (MNC), and Location Area Code (LAC). SYS INFO 3, 6, and 4 contain all or part of the information of CGI. According to the received SYS INFO, MS decodes the CGI, and decide whether it can register in the network based on the MCC and MNC indicated by CGI. At the same time, it can judge whether the current location area is changed, so as to decide whether it is necessary to start the location updating process.

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MNC

MCC

LAI

CI

LAI

CGI

_ LAC

received SYS MNC

.

CGI

info

SYS INFO 3,6 and 4

MCC

Location Area Update

CGI

MS

INFO

LA

Control Channel Description 

Control channel description includes the following parameters 

IMSI Attach-Detach Allowed (ATT)



Common Control Channel Configuration (CCCH_CONF) It is “Common Control Channel Configuration”. CCCH configuration determines the capacity of PCH, AGCH and RACH . According to the configuration of traffic channel and traffic model, CCCH can be carried by either one or multiple physical channels. Moreover, CCCH and SDCCH can share one physical channel. The MS needs to know how the CCCH(s) is/are configured, so that it can find and select one to listen to. The CCCH_CONF is just used to tell the MS about this matter. Hint : Currently CCCH can be configured according to actual traffic load. If the paging load is very heavy, the paging traffic of cell should be distributed via multiple CCCH physical channels other way. Special attention should be paid to PCH in CCCH and if the paging load is not heavy, the combined mode is used .



Access Granted Blocks Reserved (BS_AG_BLKS_RES) 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). This parameter actually assigns the proportion of AGCH and PCH on CCCH. It affects the time of MS’s response to the paging. It may be 1 or 0. If it is 1, that means block will be reserved for AGCH & we will have either 8 or 2 blocks assigned for paging . If it is 0, no blocks are reserved for AGCH & we will have either 9 or 3 blocks assigned for assigned foe paging .

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System Information Overview By : Ahmed Atef Ibrahim 

Paging Channel Multi-frames (BS_PA_MFRAMES) It is Paging Channel Multi-frames. It defines the number of multi-frames used as a cycle of paging sub-channels. D = 90/ MFRMS, MFRMS is a cell parameter defines the no. of multi-frames between the transmission of each paging group i.e. no. of multi-frames that MS would wait in sleeping mode until it is up again to listen to paging again . If MS doesn't decode the paging messages successfully, then D is decremented by MFRMS value & if messages decoded correctly, then D is incremented by 1 . If d reaches zero, then a Down link Signaling Failure is detected and cell reselection take place .



Periodic Location Update Timer (T3212) It is the Periodic Location (LA) Update Timer. It defines the interval of periodic location update.

MS

YES or No

parameter

YES Non-

cell

Combined Mode

: ATT _

IMSI attach-detach

parameter

: CCCH_CONF

Combined mode

_

Combined Mode !! Non-Combined mode

time slot (TS 0)

BCCH

: Non-Combined Mode

(TS1) SDCCH

time slot

BCCH

_

SDCCH : Combined Mode

_

time slot (TS 0) !! Non-combined Mode paging load traffic

Area Area

Combine Mode

Area

Capacity load

_ _

Non-Combined Mode

Combined Mode

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(1

Values 0 or 1 SDCCH AGCH

) parameter

MS

: BS_AG_BLKS_RES

block

at least one block

Network

paging

values 2～9

) parameter

paging group

sleep MS

:

LAC

Network

Location Update

MS

Paging

:BS_PA_MFRAMES MS

_

multi-frames

paging

Location Update LAC

MS Signaling

MS (2

_

MS MS

: T3212

: Normal Location Update

-i

: Periodic Location Update

-ii

: IMSI Attach-Detach Update

-iii

parameter

T3212

_

_

Periodic Location Update Value : 1 ( 6 min ) to 255 ( 25.5 hours ) Default : 40 ( 4 hours )

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Cell Option 

Cell option contains the following parameters:  Power control indication (PWRC) 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 influe;2nce of receiving level on BCCH is not in consideration. If it is set to “Yes”, process it in the way mentioned above



Discontinuous transmission (DTX) 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



Radio link timeout RLT This parameter is used for MS to decide down-link disconnection in case of SACCH decoding failures . Once assigned with a dedicated channel, MS will start counter S. From then on, S will decrease by 1 when a SACCH message fails to be decoded, and will increase by 2 when decoded correctly. When S decreases to 0, there will be a radio link failure.

Values :

)

DTX function ( Shall use



MS

parameter

: DTX

_

May use, Shall use, Shall not use

Its application has two advantages:

1- The interference on radio channel is effectively reduced and a better average conversation quality can be achieved 2- DTX can considerably reduce the power consumption of MS. Therefore DTX is recommended on the network.

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MS

( NO MS

BCCH

Value YES or NO timeslots

) parameter

: PWRC

_

: RLT

_

received level value base band hopping mode

)

Down Link Failure

MS

parameter

Down Link Failure

( Values 4~64 availability of resources

Cell Selection Parameter 

Cell selection parameters indicate how the MS should behave after the MS is powered on. It includes the following parameters: 





 

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Cell Reselection Hysteresis (CRH) Cell Reselection Hysteresis. It is the parameter used when cell reselection happens between two location areas . Maximum power level of control channel (MS_TXPWR_MAX_CCH) 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 ;8command. Minimum receiving level of MS permitted to access (RXLEV_ACCESS_MIN) It means the minimum receive signal level required for MS to access a cell .To prevent MS from accessing the system when the receiving signal level is very low (this will make unsatisfactory communication quality and waste the radio resources of the network), GSM specifications require that the MS’s receiving level must be greater than a threshold when it needs to register in the network. The threshold is the RXLEV_ACCESS_MIN Additional reselection parameter indicator (ACS) Half-rate supported (Support Half-Rate)

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Reselection

MS

parameter

Optimization Value

)

cell

high signaling

parameter

Max Pwr

_

Ping Pong effect

heavy traffic (8

MS

: CRH

parameter

range: 0~14

: MS_TXPWR_MAX_CCH

_

Power Control Feature

access

MS

Min Pwr

parameter

: RXLEV_ACCESS_MIN

_

Network

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SYS INFO 4 

SYS INFO 4

It consists LAI, RACH control parameters, cell selection parameters and optional CBCH channel information. It is transmitted on BCCH. When the cell supports cell broadcast function, CBCH together with CBCH MA describe the configuration of CBCH the relevant frequency information. 

Content SYS INFO 4 •

   

 

LAI Cell Selection Parameter RACH Control Parameter CBCH Channel Description (optional) These two parameters are optional. When system supports cell broadcast, CBCH Channel Description explains the CBCH channel configuration situation. When CBCH Channel is in frequency hopping mode, CBCH MA is also needed. CBCH channel description includes: channel type and TDMA offset, Timeslot Number (TN), Training Sequence Code (TSC), Hopping channel indication (H), Mobile Allocation Index Offset (MAIO), Hopping Sequence Number (HSN), Absolute Radio Frequency Channel Number (ARFCN). CBCH mobile configuration contains frequency hopping sequent description and cell channel description. CBCH Mobile Allocation SI4 Rest Octets (parameters related to cell reselection) It contains the following parameters: Cell Reselection Parameter Indicator (PI) Cell Bar Qualify (CBQ) 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 Cell Bar Access (CBA)

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Cell Bar Access, worked together with CBQ to set the priority status of the cell in idle mode for cell selection and reselection . The network operator can set the cell access is permitted or not by the parameter. Usually all cells allow MS to access, thus it is set as “Yes”. But in the special cases, the operator may want a cell to be used for handover service only, which can be realized by setting the parameter as “No” (CBQ should be “No” in this case). Cell Reselect Offset (CRO) Cell Reselect Offset. It is a parameter in C2 calculation to give an intentional modification in MS cell reselection. In other way defines a SS Offset to encourage or discourage MSs to reselct that cell (Value range: 0~63, the corresponding level value: 0~126dB, stepped every 2dB ) . Temporary Offset (TO) Cell Reselect Temporary Offset. It is a parameter in C2 criterion to give a temporary modification within PT time . Practically this useful to prevent fast moving MSs from camping on Micros (Value range: 0~7 , the corresponding value is 0~60dB, 7 corresponds to “Infinite” ) . Penalty Time (PT) Cell Reselect Penalty Time . (Value range: 0~31, the corresponding time is 20~620s. 31 is to change the formula of C2 ). If PT=31, this means a (-ve) SS Offset "CRO" will be applied to this cell & it appears less favorite for cell reselection .

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Hint :

Cell reselection is conducted on the basis of C2 value. C2 is obtained by the calculation of a series of parameters. If Cell Selection Parameter “ACS” is set as “No”, it means MS will use the relevant parameters in SI4 Reset Octets to calculate C2. If ACS is “Yes”, it means MS should obtain cell reselection related parameters from the residual bytes of system information 7 or 8 to calculate C2. Cell Reselection Parameters C2=C1+CRO-TO*H(PT-T)

(PT <31)

C2=C1-CRO

(PT = 31)

H(x)=0

if x<0；

H(x)=1

if x≥0

idle

cell

camp

MS

OFF

parameters

: CBA

CBQ

Cell Baring

high traffic

_

mode

New Sites Events

_ How can CBQ used even CBA is OFF ?!! resources

LAU

MS cell

congestion

reselection

CBA

��

resources

resources

ON

cell

OFF LOW

Don't Select

_

.. !! capacity

HIGH CBQ

MS

HIGH

LOW

Cell Selection

Cell

&Reslection

Reselction

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A= -72 dbm

B= -78 dbm

CRO= 10 dbm

C2= -72-10 = -82 dbm, So MS camps on Cell B

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SYS INFO 5



SYS INFO 5



It describes the neighbor cell BCCH frequencies(BA2 list). It is mandatory and is transmitted on SACCH. Different from SYS INFO 2, MS can read the frequency described in SYS INFO 5 in dedicated mode, report the relevant information of neighbor cells in measurement reports, and use it as the basis for handover. Similarly, for 900 MS of PHASE 1, it only recognizes the neighbor cell frequencies described by SYS INFO 5, and ignores those carried by SYS INFO 5BIS and 5TER. Content •

•

SYS INFO 5 − Neighbor Cell Description.

Hint : Corresponding to System Information 2 (System Information 2 describes BA1),System Information 5 describes part of the BA2 table. The BA2 table is used when MS is in the dedicated mode. Generally, the contents of BA1 and BA2 are the same. In special cases, such as they are modified for radio network optimization purpose, their contents can be different.

Neighbor BCCHs Serving Cell

Band

SYS INFO 5 .

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SYS INFO 2 Neighbor BCCHs 1800

900

SYS INFO 5TER

band

_

. Dedicated Mode

support

MS

SYS INFO 5BIS

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SYS INFO 5BIS 

SYS INFO 5BIS

5BIS describes neighbor cells’ BCCH frequencies.These frequencies are part of BA2 list. It is optional and is transmitted on SACCH. Generally, as the number of frequencies which can be described by SYS INFO 5 is limited, SYS INFO 5BIS carries the rest BCCH frequencies in the BA2 which belong to the same band as SYS INFO 5. Content  SYS INFO 5BIS − Neighbor Cell Description 



Hint : Corresponding to System Information 2BIS (2BIS is for BA1), the content of 5BIS is a part of the BA2 table. It is used when MS is in dedicated mode. The neighbor cells’ frequencies which belong to the same band as the serving cell will be put into 5BIS to be transmitted to the MS while there is no room in System Information 5. BA1 List SYS

Frequencies BCCH frequencies . ( serving Cell

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SYS INFO 2BIS

_

SYS INFO 5 band

) INFO 5BIS

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SYS INFO 5TER 

SYS INFO 5TER 



5TER describes neighbor cells’ BCCH frequencies, these frequencies are also a part of the BA2 list. It is transmitted on SACCH. Similarly, only dual band MS can read this information, and single band GSM900 or GSM1800 MS will ignore it. It carries the BCCH frequencies of neighbor cells whose band are different from the serving cell’s. Content  SYS INFO 5TER − Neighbor Cell Description (Extended)

Hint : Corresponding to System Information 2TER (2TER is for BA1), the content of the 5TER is a part of the BA2 table. It is used when MS is in the dedicated mode. The neighbor cells’ frequencies which belong to different band (900, 1800) than the serving cell, will be put into 5TER for transmitting to the MS.

Neighbor BCCH

SYS INFO 2TER

INFO support one band

Serving Cell MS

band

( Two Band 900 & 1800 )

_ frequencies

support

MS ignore it

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SYS INFO 6 

SYS INFO 6 •



Content •

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It describes LAI, cell identity, and some parameters describing the cell’s functions. It is transmitted on SACCH. It is also one of the most important system information.

SYS INFO 6  Cell Identity  LAI  Cell Option  NCC Permitted

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SYS INFO 7 & 8



SYS INFO 7

_ System information type 7 is optional and is sent on BCCH extended if system information type 4 does not contain all information needed for cell reselection. 

SI 7 Rest Octets

_ System information type 7 rest octets have the same format as the system information type 4 rest octets. 

TYPE 8

_ System information type 8 is optionally sent on BCCH extended if system information type 4 does not contain all information needed for cell reselection. 

SI 8 Rest Octets

_ System information type 8 rest octets have the same format as the system information type 4 rest octets.

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System Information Overview

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