gbc 004 e1 1 radio parameters-60

GBC_004_E1_1 Radio parametersZTE UniversityGSM-BSS Team

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ObjectivesAt the end of this course, you will be able to:Understand the meaning of various radio parametersGrasp the setting of radio parametersState the effect to radio network performance of various kind of radio parameters

ContentNetwork identification parametersSystem control parametersCell selection parametersNetwork function parameters

Roles of identification parametersEnable the MS to correctly identify the ID of the current networkEnable the network to be real time informed of the correct geographical location of the MS Enable the MS to report correctly the adjacent cell information during the conversation process

Network identification parameters

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CELL GLOBAL IDENTITY (CGI)Cell Global Identity (CGI) It is used for identifying individual cells within an LA

Cell Global Identity3 Digits2-3 DigitsMax 16 BitsMax 16 bitsLAINetwork identification parameters

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ROLES OF CGIThe CGI information is sent along the system broadcasting information in every cell.When the MS receives the system information, it will extract the CGI information from it and determines whether to camp on the cell according to the MCC and MNC specified by the CGI.It judges whether the current location area is changed, then determines whether to take the location updating process.


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SETTING OF CGI MCCMobile Country Code: consists of 3 decimal digits, and the value range is the decimal 000 999. MNCMobile Network Code: consists of 3 decimal digits, and the value range is the decimal 00 999. LACLocation Area Code: The range is 1-65535. CICell Identity: The range is 0-65535.


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BASE STATION IDENTITY CODE (BSIC) Base Station Identity Code (BSIC) It enables MSs to distinguish between neighboring base stations

3 Bits3 BitsBSICNCC Network/ National Color CodeValue Range: 0~7BCC Base Station Color CodeValue Range: 0~7Network identification parameters

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NCC and BCC ROLESNCC: In the connection mode (during conversation), the MS must measure the signals in the adjacent cells and report the result to the network. As each measurement report sent by the MS can only contain the contents of six cells, so it is necessary to control the MS so as to only report the information of cells factually related to the cell concerned. The high 3 bits (i.e. NCC) in the BSIC serve this purpose. BCC: The BCC is used to identify different BS using the same BCCH in the same GSMPLMN.


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BSIC CONFIGURATION PRINCIPLEIn general, it is required that Cells A, B, C, D, E and F use different BSIC when they have same BCCH frequency. When the BSIC resources are not enough, the cells close to each other may take the priority to use different BSIC.


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ROLES OF BSICInform the MS the TSC used by the common signaling channel of the cell.As the BSIC takes part in the decoding process of the random access channel (RACH), it can be used to prevent the BS from mis-decoding the RACH, sent by the MS to an adjacent cell, as the access channel of this cell.When the MS is in the connection mode (during conversation), it must measure the BCCH level of adjacent cells broadcasting by BCCH and report the results to the BS. In the uplink measurement report, MS must show BSIC of this carrier it has measured to every frequency point.


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BA LIST (BCCH ADJACENT LIST)Adjacent cell BCCH tableAt most 32 adjacent cellCarried by BCCH when MS is idle, by SACCH when MS is dedicatedThe MS will first search carriers from this table and if none is found it will turns to find any of 30 carriers with highest levels.


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RANDOM ACCESSRandom access is the process that messages being transmitted on RACH when a MS turns from idle to specialized mode. The main parameters includes: MAXRETRANSTx_IntegerAC

System control parameters

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MAX RETRANS When starting the immediate assignment process (e.g, when MS needs location updating, originating calls or responding to paging calls), the MS will transmit the "channel request" message over the RACH to the network. As the RACH is an ALOHA channel, in order to enhance the MS access success rate, the network allows the MS to transmit multiple channel request messages before receiving the immediate assignment message. The numbers of maximum retransmission (MAX RETRANS) are determined by the network.


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MAX RETRANS The MAX RETRANS is often set in the following ways: For areas (suburbs or rural areas) where the cell radius is more than 3km and the traffic is smaller, the MAX RETRANS can be set 11 (i.e. the MAX RETRANS is 7). For areas (not bustling city blocks) where the cell radius is less than 3km and the traffic is moderate, the MAX RETRANS can be set 10i.e. the MAX RETRANS is 4). For micro-cellular, its recommend that the MAX RETRANS be set 01i.e. the MAX RETRANS is 2). For microcellular areas with very high traffic and cells with apparent congestion, its recommend that the MAX RETRANS be set 00i.e. the MAX RETRANS is 1).


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Transmission Distribution Timeslots (Tx_integer)The Tx_integer parameter is the interval in timeslots at which the MS continuously sends multiple channel request messages. The parameter S is an intermediate variable in the access algorithm, and is to be determined by the Tx_integer parameter and the combination mode of the CCCH and SDCCH.


Format of Tx_IntegerMS starts the first channel request message : {0, 1, ..., MAX (Tx_integer, 8)-1} The number of timeslots between any two adjacent channel request messages {S, S+1, ..., S+Tx_integer-1} The Tx_integer is a decimal number, which can be 3~12, 14, 16, 20, 25, 32 and 50 (default). The values of the parameter S are shown as below:


Tx_integerCCH Combination ModeCCCH Not Shared with SDCCHCCCH Shared with SDCCH3, 8, 14, 5055414, 9, 16, 76525, 10, 20, 109586, 11, 25, 163867, 12, 32, 217115

ACCESS CONTROL AC The access levels are distributed as follows:C 0C9: ordinary subscribers;C11: used for PLMN management;C12: used by the security department;C13: public utilities e.g. water, gas;C14: emergency service;C15: PLMN staff.


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SETTING OF ACIn the BS installation and commissioning process or in the process of maintaining or testing some cells, the operator can set C0C9 as 0 to forcedly forbid the access of ordinary subscribers so as to reduce the unnecessary effects on the installation or maintenance work.In some cells with very high traffic, the congestion will occur in busy hours. For example, the RACH conflict happens frequently, the AGCH is overloaded and the Abis interface flow is overloaded. The network operator can set proper access control parametersC0C15to control the traffic of some cells.


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CCCH_CONFThe CCCH can be one or more physical channels. The CCCH and SDCCH can share the same physical channel. The combination mode of the common control channel in a cell is determined by the CCCH_CONF


Sheet1

AreaSubscriberTrafficNo. of BTSNo. of TRXNo. of BSC

ALL AREAS1,200,00030,0001,2207,3208

Region A780,00019,5007934,7585

Region B300,0007,5003051,8302

Region C120,0003,0001227321

S22224.60

Sheet2

CBQCBACell Selection PriorityCell Reselection State

NoNoNormalNormal

NoYesBarredBarred

YesNoLowNormal

YesYesLowNormal

Sheet3

Value RangeSpecified dBm Level

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CCCH_CONFThe CCCH_CONF is determined by the telecom operation department according to the traffic model of a cell. If a cell has 1 TRX, we recommend that the CCCH uses one basic physical channel and shares it with the SDCCH If a cell has 2 ~ 8 TRX, we recommend that the CCCH uses one basic physical channel but does not share it with the SDCCH.


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AGBLKSince the CCCH consists of the access grant channel (AGCH) and paging channel (PCH), it is necessary to set how many blocks of the CCCH information blocks are reserved and dedicated to the AGCH, the access grant reserve blocks (AGBLK).AGBLK is represented in decimal numerals, and its value range is:CCCH is not combined with SDCCH: 07.CCCH is combined with SDCCH: 02.


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AGBLKSETTING AND IMPACT OF AGBLKThe AGBLK setting principle is: given that the AGCH is not overloaded, try to reduce the parameter as much as possible to shorten the time when the MS responds to the paging and improve the quality of service of the system.The recommended value of AGBLK is usually 1 (when the CCCH is combined with the SDCCH), 2 or 3 (when the CCCH is not combined with the SDCCH).


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BS-PA-MFRMS According to the GSM specifications, every mobile subscriber belongs to a paging group. the MS calculates the paging group to which it belongs by its own IMSI. In an actual network, the MS only "receives the contents in the paging subchannel to which it belongs but ignores the contents in other paging subchannels. (i.e. DRX source). The BS-PA-MFRMS refers to how many multi-frames are used as a cycle of a paging subchannel. This parameter in fact determines how many paging sub-channels are to be divided from the paging channels of a cell.


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BS-PA-MFRMS (2) BS-PA-MFRMS is represented in decimal numerals and its value range is 29, its unit is multiframe 51 frames, its default value is 2


Sheet1

BS-PA-MFRMSMultiframes of the same paging group that cycle on the paging channel

22

33

44

55

66

77

88

99

Sheet2

Sheet3

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PERIODIC UPDATING TIMER (T3212) The frequency of periodic location update is controlled via the network and the period length is determined by the parameter T3212. The T3212 is a decimal number, within the range of 0~255, in the unit of six minutes (1/10 hours). If the T3212 is set to 0, it means that the cell needs no periodical location update.


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NCCPERMIn the connection mode (during the conversation), the MS will report the measured signals of the adjacent cells to the BS, but each report may contain at most 6 adjacent cells.Therefore, let the MS only report the information of the cells that may become the hand-over target cells.The above functions can be fulfilled by limiting the MS to merely measure the cells whose NCC have been specified. The NCCPERM lists the NCCs of cells to be measured by the MS.NCCPERM will affect handover


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RADIO LINK TIMEOUT (RLT) GSM specification stipulates that the MS must have a timer (S), which is assigned with an initial value at the start of the conversation, that is, the downlink radio link timeout value. Every time the MS fails to decode a correct SACCH message when it should receive the SACCH, the S is decreased by 1. On the contrary, every time the MS receives a correct SACCH message, the S is increased by 2, but the S should not exceed the downlink radio link timeout value. When the S reaches 0, the MS will report the downlink radio link failure. The radio link timeout is a decimal number, within the range of 4 ~ 64, at the step of 4, defaulted to 16.


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MBCR (1) The parameter "multiband indication (MBCR)" is used to notify the MS that it should report the multiband adjacent cell contents. The value is 0-3


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MBCR (2) 0: Based on the signal strength of adjacent cells, the MS reports the measurement results of 6 adjacent cells whose signals are the strongest, whose NCC are known and allowed no matter in which band the adjacent cells lie. The default value is 0 1: The MS should report the measurement result of one adjacent cell in each band (not including the band used by the current service area) in the adjacent table, whose signal is the strongest and whose NCC is already known and allowed.


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MBCR (3) 2: The MS should report the measurement results of two adjacent cells in each band (not including the band used by the current service area) in the adjacent table, whose signals are the strongest and whose NCC are already known and allowed. 3: The MS should report the measurement results of three adjacent cells in each band (not including the band used by the current service area) in the adjacent table, whose signals are the strongest and whose NCC are already known and allowed.


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Application of MBCR


CELL SELECTION C1When the MS is turned on, it will try to contact a public GSM PLMN, so the MS will select a proper cell and extract from the cell the control channel parameters and prerequisite system messages. This selection process is called cell selection. The quality of radio channels is an important factor in cell selection. The GSM Specifications defines the path loss rule C1. For the so-called proper cell, C1>0 must be ensured.

Cell selection parameters

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CELL SELECTION C1where:RXLEV_ACCESS_MIN is the minimum received level the MS is allowed to access the network MS_TXPWR_MAX_CCH is the maximum power level of the control channel (when MS sending on RACH);RXLEV is average received level; P is the maximum TX power of MS;

MAXX, YX; if X Y.MAXX, YY; if Y X.C1 = RXLEV - RXLEV_ACCESS_MIN - Max(MS_TXPWR_MAX_CCH - P ,0) Cell selection parameters

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RXLEV_ACCESS_MINThe RXLEV_ACCESS_MIN is a decimal number, within the range of -110dBm ~ -47dBmDefault value is 0 (-110dBm).


RXLEV_ACCESS_MINMeaning-47 dBm> -48 dBm (level 63)-46 dBm-49 ~ -48 dBm (level 62)......-108 dBm-109 ~ -108 dBm (level 2)-109 dBm-110 ~ -109 dBm (level 1)-110 dBm

Setting and InfluenceFor a cell with traffic overload, you can appropriately increase the RXLEV_ACCESS_MINRXLEV_ACCESS_MIN value cannot be set to too high a value. Otherwise, blind areas will be caused on the borders of cells. It is suggested that the RXLEV_ACCESS_MIN value should not exceed -90 dBm.


CELL RESELECTION C2Cell Reselection (C2) is a process when MS change its service cell in idle mode. When the MS selects a cell it will begin to measure the signal levels of the BCCH TRX of its adjacent cells (at most 6)When given conditions are met, the MS will move from the current cell into another one. This process is called cell reselection.


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CELL RESELECTION C2When C2 Parameter Indicator (PI) indicates YESthe MS will get parameters (CRO, TO and PT) , from BCCH, to be used to calculate C2(channel quality criterion), which serves as cell reselection norm. The equation is as follows:

Where T is a timer. When a cell is recorded by MS as one of the six strongest cells, timer starts counting, otherwise, T is reset to zero.

C2C1CROHPTTTO, when PT 31C2C1CRO , when PT= 31Cell selection parameters

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PARAMETER INDICATOR (PI)PI is used to notify the MS whether to use C2 as the cell reselect parameter and whether the parameters calculating C2 exist.PI consists of 1 bit. 1means the MS should extract parameters from the system message broadcasting in the cell to calculate the C2 value, and use the C2 value as the standard for cell reselect; 0 means the MS should use parameter C1 as the standard for cell reselect (equivalent to C2C1.


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CRO, PT AND TOThe cell reselection initiated by the radio channel quality regards C2 as the standard. C2 is a parameter based on C1 plus some artificial offset parameters. The artificial influence is to encourage the MS to take the priority in accessing to some cells or prevent it from accessing to others. These methods are often used to balance the traffic in the network.In addition to C1, there are three other factors influencing C2, namely: CELL_RESELECT_OFFSET (CRO), TEMPORARY_OFFSET (TO) and PENALTY_TIME (PT).


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Format of CRO, PT and TOThe CRO is a decimal number, in dB, within the range of 0 ~ 63, meaning 0 ~ 126 dB, at the step of 2 dB. The TO is a decimal number, in dB, within the range of 0 ~ 7, meaning 0 ~ 70 dB, at the step of 10 dB, where 70 means infinite. The PT is a decimal number, in seconds, within the range of 0 ~ 31, meaning 20 ~ 620 seconds for 0 ~ 30, and at the step of 20 seconds. The value of 31 is reserved to change the direction of effect that the CRO works on the C2 parameter.


C2 TYPICAL APPLICATIONSFor cells where the traffic is very heavy or the channel quality is very low. the PT may be set 31, making TO invalid, so C2=C1-CRO. For cells where the traffic is moderate, the recommended value for CRO is zero and PT=31, thus causing C2=C1, i. e. no artificial impact will be imposed.


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C2 TYPICAL APPLICATIONSFor cells with light traffic, its recommended that CRO be ranged from 0 to 20dB. The greater the CRO, the more possible the cells will be reselected ,and vice versa. Its also suggested that TO is equal or a little higher than CRO. PT, whose main role is to avoid frequent cell reselection by MS, is generally recommended to be set at 20 seconds or 40 seconds.


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CELL SELECTION HYSTERESIS (1)When a MS reselects a cell, if the old cell and the target cell are in different locations, then the MS must initiate a location updating process after cell reselection. Due to the fading features of the radio channel, the C2 values of two adjacent cells measured along their borders will fluctuate greatly. MS will frequently conduct the cell reselection, which will not only increase the network signaling flow and lead to low efficiency use of radio resources, but reduces the access success rate of the system, as the MS cannot respond to paging calls in the location updating process.


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CELL SELECTION HYSTERESIS (2)To minimize the influence of this issue, the GSM specifications put forward a parameter called cell selection hysteresis (CSH), The cell selection hysteresis is represented in decimal numerals, its unit is dB, its range is 014, its step length is 2dB, and its default value is 4.


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CELL RESELECTION PRINCIPLEIf the MS calculates that the C2 value of an adjacent cell (Same location area) surpasses the C2 value of the serving cell and maintains for 5s or longer, the MS will start cell reselection . If the MS detects a cell that is not in the same location area with the current cell, the calculated C2 value surpasses the sum of the C2 value of the current cell and the cell selection hysteresis (CSH) parameter and if it remains for 5s or longer, the MS will start the cell reselection .The cell reselection caused by C2 should be originated at least at the interval of 15s.


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CELL BAR ACCESS (CBA)In the system message broadcasting in each cell, there is a bit information indicating whether to allow the MS to access to it, which is called cell bar access (CBA). The parameter CBA is to indicate whether the cell bar access is set in a cell.The parameter is represented in character string. Its value range is:

The CBA bit is a parameter for the network operator to set. Usually all the cells are allowed to be accessed by MS , so the bit is set NO. However, in special cases, the telecom operator may want to assign a certain cells for handover service only, then the bit can be set YES.

YES:the cell is barred for accessNO:the cell is not barred for accessCell selection parameters

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CELL BAR ACCESS (CBA) Cell selection parameters

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CELL BAR QUALIFY (CBQ) In areas where the cells overlay with each other and differ in capacity, traffic and functions, the telecom operator often hopes that the MS can have priority in selecting some cells, that is, the setting of cell priority. This function is set by way of the parameter "Cell Bar Qualify" (CBQ).

YES:The cell has low priorityNO:The cell has normal priorityCell selection parameters

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CELL BAR QUALIFY (CBQ) 2C1 and C2 States with CBA and CBQ ConfigurationsCell selection parameters

Sheet1


ALL AREAS1,200,00030,0001,2207,3208

Region A780,00019,5007934,7585

Region B300,0007,5003051,8302

Region C120,0003,0001227321

S22224.60

Sheet2


NoNoNormalNormal

NoYesBarredBarred

YesNoLowNormal

YesYesLowNormal

Sheet3

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EXAMPLE OF CBQ SETTINGFor some reasons, the traffic of Cells A and B is apparently higher than that of other adjacent cells. To balance the traffic in the whole area, you can set the priority of Cells A and B as low, and set the priority of the rest cells as normal so that the traffic in the shade area will be absorbed by adjacent cells. It must be noted that the result of this setting is that the actual coverage of Cell A and Cell B is narrowed. However, this is different from reducing the transmitting power of Cell A and Cell B, the latter may cause blind areas of the network coverage and the reduction of communication quality.


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LIMITnAccording to GSM Specification 05.08, the BTS must measure the interference levels of the upward links of all the free channels for the purpose of providing basis for managing and allocating radio resources. Moreover, the BTS should analyze its measured results, divide the interference levels into 5 grades and report them to the BSC. The division of the 5 interference grades (i.e. the so-called interference bands) is set by the operator through the man-machine interface. The parameter "Interference band border(LIMITn) determines the borders of the 5 interference bands.

Network function parameters

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LIMITnThe division of the interference bands should be favorable in describing the interference in the system. Generally the default values are recommended. In the ordinary situations, the free channel interference level is smaller, so the LIMIT14 value should be smaller. When apparently large interference appears in the system, you can properly increase the LIMIT1~4 values in order to know the exact interference.

Default:LIMIT14LIMIT28LIMIT315LIMIT425


Sheet1


ALL AREAS1,200,00030,0001,2207,3208

Region A780,00019,5007934,7585

Region B300,0007,5003051,8302

Region C120,0003,0001227321

S22224.60

Sheet2


NoNoNormalNormal

NoYesBarredBarred

YesNoLowNormal

YesYesLowNormal

Sheet3

Value RangeSpecified dBm Level

0

INTAVEDue to the randomness of the radio channel interference, the BTS must average the measured uplink interference levels within the specified period, and this average cycle is determined by the INTAVE parameter. This parameter is a decimal number, in SACCH multi-frames, within the range of 1 ~ 31.


New Cause Indication (NECI) The NECI is a decimal number, within the range of 0 ~ 1, with the meaning described as below:When the NECI is 0, it means that the cell does not support the access of half-rate services. When the NECI is 1, it means that the cell supports the access of half-rate services.


RE-ESTABLISHMENT ENABLE (RE)For the drop calls caused by the radio link fault, the MS can start the call reestablishment process to resume the conversation, but the network is entitled to determine whether the call reestablishment is allowed or not. 0=Yes, 1=No.In some special circumstances, the drop call may occur when the MS goes through a blind area during the conversation. If the call reestablishment is allowed, the mean drop call rate will be reduced. However, the call reestablishment process will occupy a longer period of time, most of the subscribers have hung up before the reestablishment process is over, as a result, the call reestablishment failed to achieve its purpose and wasted many radio resources. We recommend that the call reestablishment be not allowed in the network except for some individual cells.


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gbc 004 e1 1 radio parameters-60

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