22066459 Chapter7 Parameter Design

8/6/2019 22066459 Chapter7 Parameter Design

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Wireless Network Planning Table of contents

Table of Contents

Chapter 7 Parameter Design ........................................................................................................11.1 System message ..............................................................................................................11.2 Cell Selection and Cell Reselection ..................................................................................3

1.2.1 Network Selection ...................................................................................................3

1.2.2 Cell Selection and Reselection ...............................................................................4

1.2.3 Location Updating ...................................................................................................7

1.3 Huawei Handover Algorithm ............................................................................................10

1.3.1 Handover Decision Flow .......................................................................................11

1.3.2 Measurement Report Pre-processing ...................................................................11

1.3.3 Penalty Processing ...............................................................................................12

1.3.4 Handover Sequencing Algorithm ..........................................................................12

1.3.5 Emergency Handover ...........................................................................................14

1.3.6 Load Handover .....................................................................................................14

1.3.7 Normal Handover ..................................................................................................16

1.3.8 Power prediction after handover ...........................................................................18

1.3.9 Concentric Circle Algorithm ..................................................................................19

1.4 Huawei Power Control Technology .................................................................................22

1.4.1 MR Preprocessing ................................................................................................24

1.4.2 Second Generation of Huawei Power Control Policy ............................................24

1.5 New Channel Allocation Algorithm ..................................................................................271.6 Dual-frequency Network Technology ..............................................................................28

1.6.1 Necessity for Building Dual-frequency Network ....................................................28

1.6.2 Fast Fading Characteristic and Coverage Problem of GSM1800 .........................28

1.6.3 Dual-frequency Networking Structure ...................................................................29

1.6.4 Traffic guidance and Control Policy of Dual-frequency Network ...........................31

1.6.5 Dual-frequency Networking Engineering Implementation .....................................34

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Wireless Network Planning Chapter 7 Parameter Design

Chapter 7 Parameter Design

The network planning is concerned with hundreds of parameters, which consists ofcomplicated algorithms and protocols. Only with deep understanding of the algorithmsand protocols can we flexibly apply these parameters to various different actualenvironments. Therefore, this chapter mainly describes some protocols andalgorithms related to the network planning, such as system message, handover,power control, channel allocation, etc. For description of other parameters, pleaserefer to Data Configuration Specifications for GSM900 and 1800 BSS NetworkPlanning.

The research on radio network parameters should take potential dangerous factors ofradio network (such as large traffic, abnormal user behavior, etc.) into consideration(please do not limit your attention to individual small network).

Furthermore, the parameters are not independent from each other, and many network

problems and phenomena result from the combined function of many functionalalgorithms and radio networking modes. For these integrated phenomena, pleasecombine the theoretic research and practical experiences to conduct complete and in-depth analysis of special topics from various aspects such as MSC, BSC, BTS,characteristics of radio network, etc. During the analysis, please pay attention toapplication recommendations of actual networking algorithm and guide to problemanalysis, etc. Especially, when the radio network is getting more and morecomplicated and the traffic and capacity are getting larger and larger, this task is moreurgent and it is more complicated and difficult to conduct integrated application ofthese parameters with combination of the characteristics of radio network. Toaccomplish this task, long-term practice and experience accumulation are needed.

In the GSM system, large quantities of radio parameters are set based on cell or

local area, while the inter-area parameters generally have strong relativity. Therefore,please consider the influence of parameter setting in an area upon other areas orespecially neighboring areas during parameter planning and adjusting, or theparameter adjusting may lead to great side effect.

In addition, if certain problem occurs to local area in the network, please firstlydetermine whether the problem is caused by equipment fault (including connectionproblem). Only when you confirm that the network problem is really caused by servicecan the radio parameter adjustment be made.

1.1 System message

To obtain or provide various services, the MS needs many messages from the

network, and these messages broadcast at radio interfaces are called systemmessages. The system message includes main radio network parameters at areinterfaces, specifically speaking, including network identification parameters, cellselection parameters, system control parameters and network function parameters.Through receiving the system messages, mobile phones can correctly access andselect appropriate network and can fully utilize various services provided by thenetwork so as to perfectly cooperate with the network. The system message can bedivided into two parts: System messages transmitted in BCCH channel, mainlyincluding system messages 1, 2, 2BIS, 2TER, 3 and 4; and system messagestransmitted in SACCH channel, mainly including system messages 5, 5BIS, 5TERand 6. To support GPRS, Huawei BSC also supports system message 13, which willnot be described in this section.

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I. System message 1

System message 1 mainly describes Random Access Control information (RACH)and Cell frequency Allocation table (i.e., CA table), transmitted in BCCH channel.

System message 1 mainly includes information of the following parameters: CA table,maximum retransmission times (MAX retrans), number of expanded transmissiontimeslots (Tx_interger), cell access barred (CELL_BAR_ACCESS), Access levelControl (AC), Call reestablishment enabled (RE), Emergency Call enabled (EC), etc.

II. System messages 2, 2bis and 2ter

System message 2 mainly describes RACH, Network Color Code Permitted NCCPermitted} and frequency allocation table of neighboring cells (i.e., BA1 table),transmitted in BCCH channel. In general, system messages 2, 2BIS and 2TERdifferent parts of the BA1 table respectively, and mobile phones can conduct cellreselection in idle mode through reading and decoding the BA1 table. For a 900mobile phone in PHASE 1, it only identifies frequency of neighboring cell described bysystem message 2, but neglects frequency messages of neighboring cells carried by2BIS and 2TER messages.

System message 2BIS mainly describes RACH and expanded frequency allocationtable of neighboring cells (it is also a part of BA1 table). It is optional and transmittedin BCCH channel. Generally, the frequency allocation table carried by systemmessage 2 can only describe a limited number of frequencies, so system message2BIS carries information of other frequencies (which are in the same frequency bandas system message 2) in the BA1 table.

System message 2TER mainly describes expended frequency allocation table ofneighboring cells (part of BA1 table), transmitted in BCCH channel. Only dualfrequency mobile phones read this message (single frequency 900 or 1800 mobilephones will neglect this message. Since this message carries frequency informationof different frequency band from the frequency of current cell, so these messages are

unnecessary for single frequency mobile phone.

System message 2, 2bis and 2ter mainly includes information of the followingparameters: Neighboring cell description (BA1 table), NCC Permitted, RACH ControlPara, extended neighboring cell description (Extended), multi-band reporting(Multiband_Reporting), etc.

III. System message 3

System message 3 mainly describes location area identifier, cell identifier, RACH andparameters related to cell selection. It is compulsory and is transmitted in BCCH.System message 3 is one of the most important system messages.

System message 3 mainly includes information of the following parameters: CellGlobal Identity (CGI), IMSI Attach-Detach allowed (ATT), Common control channelconfiguration (CCCH-CONF), number of accessed modules allowed to be reserved(BS_AG_BLKS_RES), number of paging channel multi-frames (BS-PA-MFRAMS),Periodic location updating timer (T3212), power control indication (PWRC),discontinuous transmission (DTX), radio link timeout (Radio_Link_Timeout), CellSelection Hysteresis, maximum power level of control channel(MS_TXPWR_MAX_CCH), accessible minimum received level(RXLEV_ACCESS_MIN), additional reselection parameter indication (ACS), half-rateindication (NECI), RACH Control Para., etc.

IV. System message 4

System message 4 mainly describes location area identifier, RACH, cell selectionparameter and optional CBCH channel information. It is compulsory and is

transmitted in BCCH. The optional IE CBCH description and the MA describe the

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configuration of the CBCH channel and corresponding frequency information whenthe system supports cell broadcast.

System message 4 mainly includes information of the following parameters: LocationArea Identity (LAI), Cell Selection Para., RACH Control Para., CBCH channeldescription and CBCH MA, cell reselection parameter indication (PI), Cell BarQualification (CBQ), Cell Reselection Offset (CRO), Temporary Offset (TO) andPenalty Time (PT).

V. System message 5, 5bis, 5ter

System message 5 mainly describes frequency information of neighboring cells (i.e,BA2 table). It is compulsory and is transmitted in the SACCH channel. Different fromsystem message 2, mobile phones can read frequencies described in systemmessage 5 in communication state and report relevant information of neighboringcells in measurement report so that the report can be used as basis of handover.Similarly, for a mobile phone in PHASE 1, it only can identify neighboring cellfrequency described in system message 5, but neglects frequency information ofneighboring cell carried by messages 5BIS and 5TER.

System message 5BIS mainly describes frequency information of neighboring cells(part of BA2 table). It is optional and is transmitted in SACCH. Generally, thefrequency allocation table carried by system message 5 can only describe a limitednumber of frequencies, so system message 5BIS carries information of otherfrequencies (which are in the same frequency band as system message 5) in the BA2table.

System message 5TER mainly describes frequency information of neighboring cells(it is also a part of BA2 table). It is transmitted in SACCH channel. Similarly, only dualfrequency mobile phones can read this message (single frequency 900 or 1800mobile phones will neglect this message).

System messages 5, 5bis and 5ter mainly include information of relevant parameterssuch as neighboring cell description (Neighbor Cell Desc.), extended neighboring cell

description (Extended), etc.

VI. System message 6

System message 6 mainly describes location area identifier, cell identifier and someparameters describing cell functions. It is compulsory and is transmitted in SACCHchannel. System message 6 is also one of the important system messages.

System message 6 mainly includes information of the following parameters:Information on relevant parameters such as CGI, Cell Option, NCC Permitted, etc.

1.2 Cell Selection and Cell Reselection

In idle mode, mobile phone can conduct the following operations: Network selection,cell selection/reselection and location update.

1.2.1 Network Selection

The mobile station always preferably selects Home Public Land Mobile Network(HPLMN). If a mobile phone is not within the coverage area of the HPLMN, then themobile phone will select Visit Public Land Mobile Network (VPLMN). Even in roamingmode, the mobile station will still periodically attempt to search for the HPLMN.

(1) Power on or start network selection when entering coverage area

(2) Subscriber reselection

A subscriber can start network selection at anytime.

(3) Periodically searching for HPLMN in national roaming mode

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In national roaming mode, the mobile station will periodically attempt to search for theHPLMN. Its periodic value T is stored in the SIM card (If T is not available in the SIM,then please use the default value of 30 minutes).

Success sign of network selection by mobile station:

Successfully finding appropriate resident cell in the network. Successful location update

There are two network selection modes: Automatic mode and manual mode.

(1) Automatic mode

The mobile station automatically select available network of the highest priority.

(2) Manual mode

The mobile station provides a network list and the subscriber selects the network tobe accessed. This network list includes PLMN not allowed.

The mobile phone stores a PLMN not allowed list in the SIM card. When the mobilephone conduct the location updating of location registration in the VPLMN andreceives the location updating rejection including PLMN not allowed, it will add thenetwork (VPLMN) to the list. After successful location update in manual networkselection mode, the network (VPLMN) will be deleted from the list. After power-off orpulling out the SIM card, the list is still reserved. The HPLMN is not included in thelist.

1.2.2 Cell Selection and Reselection

In the selected network, the mobile station will search for an appropriate resident cellaccording to the descending order of the received level strength so that the mobilestation can receive system messages from the network.

I. Conditions of appropriate and normal resident cell

The priority of cell can be divided into: Normal, low priority and bar access. Only whenthere is no appropriate normal cell will the low priority cell be selected.

The appropriate conditions include:

(1) The cell belongs to the selected network.

(2) The cell is not barred.

(3) The cell does not belong to barred national roaming location area.

(4) The radio path loss between MS and BTS is under the threshold set for thenetwork.

The cell priority is determined by both CBQ(CELL_BAR_QUALIFY) and CBA(CELL_BAR_ACCESS).

CELL_BAR QUALIFY CELL_BAR ACCESS Cell selection priority Status for cellreselection0 0 Normal Normal0 1 Barred Barred1 0 Low Normal1 1 Low Normal

II. Cell selection

To implement cell selection and reselection, mobile phones require that all monitoredfrequencies should maintain an average received level grade. The average receivedlevel (RLA_C) should be unweighted average value of the receiving signal levelmeasured with dBm.

(1) Normal cell selection

A mobile phone will search all RF channels in the system (at least 30 RF channels for

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900M system, at least 40 RF channels for 1800M system and at least 40 RF channelsfor PSC1900) to obtain the received level of each RF channel and to calculate thecorresponding RLA_C. The averaging of the received level of each TRX should atleast based upon five measured samples (with a time about 3 to 5 seconds). Themeasured samples of different RF TRXs are uniformly distributed within this period of

time.Then the sequencing according to the descending order of the levels will beperformed and BCCH will be selected. The cell of normal priority will be selectedpreferably among these TRXs. If the appropriate cell is only the cell of low priority, themobile phone will also select the cell of best level. However, in this case the mobilephone has already performed all decoding and identification of the above frequencies.If no appropriate cell is available, the mobile phone will continue to search.

The maximum time to synchronize a BCCH TRX is 0.5s and the maximum time toread the data of a synchronized BCCH TRX is 1.9s. Where the time to obtain systemmessage is exceptional, being n*1.9s(n>1).

(2) Storage table cell selection

In this case, the mobile station has a previously stored BCCH frequency list of theselected network (more than one). For each stored BCCH TRX of the selectednetwork, the mobile phone executes the same sampling process as normal cellselection (only aiming at the stored BCCH TRX). If the storage table cell selectionfails, please start normal cell selection. Please note that if all the cells in this case arecells of low priority, the mobile phone will also finally select a cell of the highest level(but the mobile phone has conducted the decoding of TRXs in all the BA lists. When amobile phone over 900M network enters the 900/1800 network, the mobile phonemay select the 900 network regardless of the priority, since all the contents of theBCCH frequency list stored in the mobile phone only cover 900M frequencies.

(3) Cell selection criteria

The path loss criteria parameter C1 should be used for cell selection:

C1=RLA_C - RXLEV_ACCESS_MIN- MAX((MS_TXPWR_MAX_CCH- P), 0)For DCS 1800 3 mobile phones, C1 is:

C1=RLA_C-RXLEV_ACCESS_MIN-MAX((MS_TXPWR_MAX_CCH+POWEROFFSET- P), 0)

Where all the parameters have the same unit dBm. The meaning of each parameteris as follows:

RLA_C: Average received level of mobile station

RXLEV_ACCESS_MIN: Minimum accessible received level of mobile station

MS_TXPWR_MAX_CCH: Maximum CCH power level

P: Maximum transmitting power level of mobile station.

POWER OFFSET: Power offset used by DCS 1800 3 mobile phones, which is relatedto MS_TXPWR_MAX_CCH

The so-called appropriate cells should meet the requirement: C1>0.

III. Downlink signaling link fault

The downlink link fault criteria are based upon downlink signaling link fault counter(DSC). When the mobile phone resides in a cell, the DSC will be initialized to aninteger close to 90/N to the greatest extent (N stands for BS_PA_MFRMS---numberof frames among same paging, with a value range: 2 to 9). Therefore, when themobile phone attempts to decode the message in the paging subchannel, the value ofDSC will increase by one whenever a message is successfully decoded (but shouldnot exceed the initialized value). If the message decoding fails, the DSC will decreaseby four. If DSC 0, then a downlink signaling link fault occurs. The downlink signalinglink fault will lead to cell reselection.

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IV. Cell reselection

After the cell selection and when the cell reselection starts, the mobile phone willsynchronize and read information of 6 BCCH TRXs (with highest signal level) not inthe service cell as soon as possible (The BCCH TRXs should be in the BA table). For

multi-frequency mobile phones, the TRXs with strongest signal level possibly aredistributed in different bands.

In idle state, the mobile phone will keep on monitoring the information of all the BCCHTRXs specified by the BCCH allocation table (BA), and also within the time periodfrom 5s to Max {5 , ((5 * N + 6) DIV 7) * BS_PA_MFRMS / 4}s, the mobile phone willaverage each received level of the BCCH TRX (where, N refers to the number ofBCCH TRXs not in the service cell). For each RLA_C (average received level), atleast five level measurement samples are needed (RLA_C value is often updated).With respect to service cell, each paging block of the mobile phone at least needsone received level sample. The RLA_C is calculated by averaging the sampled levelvalues received from 5s to Max (5s, five consecutive paging blocks of that MS).

Each time when the measurement of RLA_C is updated, the TRXs in the list (in BA

list)of 6 BCCH TRXs with the highest signal level not in service cell will be updatedeither (possibly the frequencies will be updated faster).

The mobile phone at least attempts to decode all BCCH data of the service cell every30s, and it at least attempts to decode the BCCH data block (which exerts influenceupon cell reselection parameters) carried in 6 BCCH TRXs (with the highest signallevel) not in service cell every five minutes. When the mobile phone finds that a newBCCH TRX has become one of the six TRXs with the highest signal level, the data ofthis BCCH TRX should be decoded in 30s. At least every 30s, the mobile phoneattempts to detect the BSIC (base station color code) of the 6 BCCH TRXs (with thehighest signal level) not in service cell so as to confirm whether it monitors the samecell. If the BSIC changes, then this TRX will be regarded as a new TRX and theBCCH data will be read once again.

The mobile station in resident state will keep on selecting cell better than the current

cell. Corresponding to the parameter C1 applied to cell selection, the path loss criteriaparameter C2 is used for cell reselection. C2 is determined by the following formula:

C2=C1+CELL_RESELECT_OFFSET-TEMPORARY_OFFSET*H(PENALTY_TIME-T)When PENALTY_TIME< >31,

C2 = C1-CELL_RESELECT_OFFSET When PENALTY_TIME =31,

where:

CELL_RESELECT_OFFSET: Cell Reselection Offset (CRO) is used to manuallycorrect C2.

TEMPORARY_OFFSET: Temporary Offset (TO),

PENALTY_TIME: Penalty Time (PT), determining the action time of the TO.

T: A timer with the initial value of 0. When a certain cell is recorded in the list of the sixneighboring cells with the highest signal level by the mobile station, the counter Tcorresponding to this cell starts to count to the accuracy of a TDMA frame (about 4.62ms). When this cell is deleted from the list of the six neighboring cells with the highestsignal level by the mobile station, the corresponding cell will be reset. If cellreselection is needed, the previous service cell enters the list of the six neighboringcells with the highest signal level, and the T value is PENALTY_TIME.

H(x) :

For non-service cells (neighboring cells): H(x) = 0 when x < 0= 1 When x > 0

For service cell: H(x) = 0

If CELL_RESELECT_PARAM_IND in system messages 3 and 4 broadcast in BCCH

is set as 1, then the cell reselection parameters CELL_RESELECT_OFFSET,

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TEMPORARY_OFFSET and PENALTY_TIME are also broadcast in BCCH systemmessages 3 and 4. If CELL_RESELECT_PARAM_IND is set as 0, then the mobilephone will think that all cell reselection parameters are 0, therefore, C2=C1.

At least every 5s, the mobile phone will calculate C1 and C2 of the service cell. Themobile phone will calculate C1 and C2 of all cells not in service (neighboring cells)again if necessary. The mobile phone will keep on checking the following conditions:

(1) The path loss (C1) of the current service cell is decreased to a value less than 0within 5s. It indicates that the path loss of the cell is too great.

(2) The C2 value of an appropriated non-service cell keeps on exceeding C1 value ofthe service cell in 5s and also meets the following conditions:

(a) If the new cell is in different location area, C2 value of the new cell subtractedby cell reselection hysteresis (CELL_RESELECT_HYSTERESIS, broadcast insystem messages 3 and 4 in BCCH channel of the service cell) keeps onexceeding C2 value of the service cell.

(b) If cell reselection occurs in recent 15s, then the C2 value of the new servicesubtracted by 5dB keeps on exceeding C2 value of the service cell in 5s.

A new cell meeting the above condition is the better cell. If the better cell is available,then the mobile phone will perform cell reselection.

After finding the better cell and cell reselection, the mobile phone should not reselectthe previous resident cell in 5s, although the cell may meet the cell reselectionconditions.

To summarize, the following conditions will lead to cell reselection:

(1) The radio path loss of the current resident cell is too great (C1 0).

(2) The downlink of the current resident cell fails (DSC 0).

(3) The current resident cell has been barred.

(4) According to the cell reselection parameter C2, it is found that there is a cell betterthan the current resident cell in the same location area, or with the application of theCell Reselection Hysteresis parameter (CRH), there is a better cell in another locationarea of the network.

(5) The random access times reaches the maximum retry times broadcast in BACH,but the mobile phone has not successfully accessed to the current resident cell yet.

1.2.3 Location Updating

I. Normal location update (location update of offside location area)

When a mobile station moves from one location area to another location area, itshould make registration, that is to say, once the mobile station finds that the LAI in itsmemory is different from the LAI number of the current cell, it will request the network

to change the stored location information. This process is called location update.Firstly, considering mobile station powered on in idle state, which moves in the samelocation area, and if cell reselection occurs in this case and the service cell of themobile station has changed, the mobile station will not inform the network of thechange. That is to say, the mobile station only conducts cell reselection, but not thelocation update, so the network does not take part in the processing. If two cells arenot in the same location area before and after reselection, the mobile station mustinform the network of the location area change. This process is called forcedregistration.

According to the different location update identifiers, i.e., in broad sense, the locationupdate can be divided into normal location update (location update of offside locationarea), periodic location update (corresponding to T3212) and IMSI attachment

(corresponding to mobile stations powered on). Dividing specifically, the locationupdating division depends whether the location update program belongs to the same

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VLR and whether the participation of IMSI number is needed. It can be divided intothe following several types of location update.

(1) Location update of different location areas in the same VLR (INTRA VLRLOCATION UPDATE)

This is the simplest location updating process. During this process, the mobile stationdoes not need to provide IMSI number. The updating is conducted I the current VLR,without the need to notify HLR.

During the initialization, the mobile station has marked in the initialized messagecarried by SABM frame sent to the network that the direct access reason is locationupdating request (MM LOCATION UPDATING REQUEST). This message carries theTMSI number and LAI numbers of the mobile station with clearly indication of normallocation updating. If the MSC sends this message to the VLR when it receives it, theVLR will update the location message of the mobile station and store the new LAInumber, and also it will send a new TMSI number (it is appropriate for the TMSI re-allocation command not to carry the TMSI number, but in this case the mobile stationwill still use the previous TMSI) to the mobile station. After the TMSI re-allocation ofthe mobile station is finished, the MSC will send the location update accepted

(LOCATION UPDATE ACCEPT) to the mobile station. After this, it releases thechannel location update end.

(2) Extra-VLR Location update and the TMSI number is transmitted

When a mobile station enters a cell, if it finds that the stored LAI number is differentfrom the current LAI number, then in the location updating request, it will send its oldLAI number and the stored TMSI number to the VLR through the MSC. When theVLR finds that the LAI number does not belong to itself, it will educe the previous VLRaddress according to the old TMSI and LAI numbers and also it will request the oldVLR to send the IMSE and authorization parameters(MAP_SEND_IDENTIFICATION). The old VLR will return the IMSI and authorizationparameters of the mobile station to the new VLR. If the new VLR cannot obtain theIMSI due to certain reasons, the VLR will send identity request message to the MS to

ask for the IMSI number. After the VLR obtains the IMSI number, it will send locationupdating message to the HLR of the MS. The location message includes MS identifierand relevant information so that the HLR can query data and set up path. After theHLR receives this message, if the new MSC/VLR has normal service authority, thenthe HLR will store the current VLR number and will also send Cancel locationmessage to the old VLR (MAP/D_CANCEL_LOCATION). The old VLR will delete allthe information of the MS after receiving the message and will also send cancellocation confirmation message back to the HLR(MAP/D_CANCEL_LOCATION_RESULT). The new VLR will continue the process ofauthorization encryption and TMSI re-allocation. After that, the HLR will provide theVLR with necessary subscriber information through originating message of insertingsubscriber data (MAP_INSERT_SUBSCRIBER_DATA), including information such asauthorization parameters, etc. When the HLR receives the response of the VLR, it will

send location updating confirmation message to the VLR.(3) Extra-VLR Location update and the IMSI number is transmitted

The location updating process is the same as the above one and is simpler, since itdirectly request authorization parameters from the HLR through the IMSI number.

II. IMSI attachment and detachment

The IMSI attachment and detachment means to add a binary mark to the subscriberrecord in the MSC/VLR. The IMSI attachment process means to set the mark asaccess allowed, while the IMSI detachment means to set the mark as access notallowed.

When the mobile phone powers on, it should notify the network of the power-on state.

This notification process is implemented as follows: The mobile station sends anIMSI attachment message (IMSI ATTATCH) to the network so that the network can

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know that the current state of the mobile phone has changed. The network willindicate clearly the current subscriber state in the system data when receiving thismessage, such that the network can originate its paging program when the pagingmessage of the mobile station arrives.

After power-on, if the mobile station finds that its stored LAI number is consistent withthe current LAI number, then it will perform the IMSI attachment process. It programprocess is basically the same as that of INTRA VLR LOCATION UPDATE, and theonly difference is that the LOCATION UPDATING REQUEST message clearlyindicates that the location updating type is IMSI attachment. Its initialization messageincludes the IMSI number of the mobile station.

After power-on, if the mobile station finds that its stored LAI number is not consistentwith the current LAI number, then it will execute normal location updating process.

It the mobile station wants to power off, it will define to trigger the IMSI detachmentprocess through a key. During this process, only one command is sent from the MS tothe MSC/VLR. This is a piece of unconfirmed message. When the MSC receives theIMSI detachment request, it will notify the VLR to add the Detach mark to the IMSI,but the HLR is not informed of the message that the subscriber has detached from

the network. When this subscriber is paged, the HLR will request the roaming number(MSRN) from the VLR where the subscriber is located. In this case, the HLR will beinformed that the subscriber has detached from the network. Thus, the pagingprogram will not be executed and the paging message will be directly treated, such asplaying the announcement The subscriber is powered off, etc. After the MS sendingout this message, the RR connection will be abandoned automatically.

III. Periodic location updating

If the following conditions occur, the network will always lose connection with themobile phones: (a). When the powered-on mobile station moves out of the coveredarea (i.e., blind area) of the network, in such case, the mobile station cannot send anyinstructions to the network, therefore, the network cannot know the current state of

the mobile phone and it will still think that the mobile station is in attachment state.(b). When the mobile station sends the IMSI Detach message to the network, if thelink is off poor quality due to certain interference in the uplink lf the radio path, thenthe network possibly cannot correctly decode the message. Therefore, it means thatthe system still think that the MS is in attachment state. (c). When the mobile stationis powered off, it still cannot inform the network of its current state, so the two of themlose connection. When the above three cases occur, if the mobile station is beingpaged, then the system will send the paging message in the location area which thesubscriber has registered before. The result is of course that the network cannotreceive the paging response, which will lead to invalid system resources seizure.

To solve this problem, the GSM system takes corresponding measures to force themobile station to report its current location to the network after a certain period oftime. Thus, with this kind of mechanism, the network can understand whether any

change occur to the current state of the mobile station. This is the periodic locationupdating mechanism. With the help of the system broadcast message of BCCH in thecell, the BSS sends the periodic location updating time (T3212) to all subscribers inthe cell so as to force the mobile stations to automatically originate the locationupdating request to the network after the timer is timeout (the request reason shouldbe marked as periodic location updating. After the cell selection or reselection, themobile station will read T3212 from the system message of the current service cell,and also it will set the timer and store it in its SIM card. After that, the mobile stationwill automatically originate location-updating request to the network if it finds that theT3212 is timeout. Correspondingly, for the NSS part, the network will periodicallyquery the subscribers marked as IMSI attachment in its VLR and it will change theidentifier of the subscribers (which do not have any connection with the networkduring this period of time) as IMSI detachment (IMSI DETATCH), so as to prevent

paging for such mobile stations (such paging will lead to waste of system resources).

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To widen the coverage range and to improve the signal quality of hotspots and large-traffic areas.

1.3.1 Handover Decision Flow

The decision flow of Huawei handover algorithm is shown in Figure 7-2.

Figure 7-2 Decision flow of Huawei handover algorithm

1.3.2 Measurement Report Pre-processing

The measurement report pre-processing mainly includes the following two functions:

I. Measurement Result (MR) Interpolation

Generally, the MS will periodically report the measurement results of the uplinks and

neighboring cells, and the BTS will combine the measurements of correspondinguplinks to form Measurement Result and then will report to the BSC. If due to somereason, the received measurement results are discontinuous, then these lostmeasurement results should be interpolated within a certain loss limit. Thisprocessing is called MR interpolation calculation.

The continuity of the MR is judged by Measurement result number, and theinterpolation algorithm adopts simplified one-order interpolation method (the lostvalue is calculated according to the measurement value at both ends of the lostmeasurement result).

II. MR filtering (MR Time Evaluation)

The series of measured values corresponding to a radio link will not be a smooth

curve. To remove accidental factors in handover decision, smooth processing shouldbe conducted for various measured values. This process is regarded as MR filtering.

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There many methods for MR averaging. At present, we use the method of obtainingcurrent values for decision-making by the simple forward averaging. The number offorward obtained values is called filter length. For different types of measured values,there are different filter lengths.

1.3.3 Penalty Processing

I. Penalty for handover failure

Among existing algorithms, when the service cell fails in handover to the neighboringcell, it will terminate regarding the neighboring cell as the destination cell, butcontinue handover attempts to the cell. Thus it will lead to frequent invalid handoverattempts and exert great influence upon the system performance. Therefore, in cellhandover, once the handover fails, the destination cell should be punished during acertain period of time so as to avoid frequency unsuccessful handover attempts.

II. BQ and TA penalty

For emergency handover caused by BQ and TA, after handover to the destinationcell, once the destination cell needs handover due to reasons such as traffic, priority,etc. (since in this case it cannot obtain the TA and receiving quality of the originalservice cell except the received level), if the received level of the original cell ishigher, then the MS will still possibly be handed over back to the original service cell,thus leading to ping-pong handover. Therefore, the penalty-processing module alsoincludes the handover penalty for BQ and TA, i.e., After the MS is handed over to itsneighboring cell due to TA and BQ, the original service cell will be punished during acertain period of time.

1.3.4 Handover Sequencing Algorithm

To select an appropriate destination handover cell, the neighboring cells will be

queued according a certain sequencing principle. The M criteria, K criteria and 16bitcriteria.

I. M criteria

Firstly, determine whether the received levels of the neighboring cells are higher thanthe minimum received level, since only the neighboring cells whose received lever ishigher than the minimum received level can enter the candidate cell list, i.e., theneighboring cells are tailored according their received levels.

For the service cell:

RXLEV(o) >MSRXMIN(o) + MAX(0,Pa(o))

For neighboring cells:

RXLEV(n) > MSRXMIN(n)+ MAX(0,Pa(n))Where,

RXLEV(o) and RXLEV(n) are MS received levels of the service cell and theneighboring cell respectively, while MSRXMIN(o) and MSRXMIN(n) are the minimumreceived levels of the MS required by the service cell and the neighboring cell.

Pa(o)=MS_TXPWR_MAX(o)-P;

Pa(n)=MS_TXPWR_MAX(n)-P;

P =max_power_of_ms;

MS_TXPWR_MAX(n) is maximum transmitting power of mobile phone limited by theBSS.

max_power_of_ms is the maximum transmitting power of the mobile phone itself.

The method can be described as follows: The existing algorithm only considers the

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minimum received power threshold of downlink and does not consider uplink. Thus, ifthe maximum power of the mobile phone exceeds the maximum transmitting levelrequired by the BSS, then Pa is equal to zero, i.e., the uplinks of the mobile phonecan also meet the requirements; to the contrary, the minimum received level ofdownlink should be added with a compensation value to meet the requirements of

uplink received level of the neighboring cell.

II. K criteria

The sequencing of candidate cells is based upon the received level. A hysteresisexists among the cells, i.e., the K hysteresis, which is equivalent to a thresholdbetween different cells and plays the function of handover stabilizer. The actualreceived level of the downlink of a neighboring cell subtracted by a virtual offset (Khysteresis) is the received level of the neighboring cell finally obtained by the servicecell. All neighboring cells are sequenced according to this value and the priorities ofthe neighboring cells are reduced from front to back.

III. 16 bits criteria

Huwei BSC handover algorithm is based upon the 16bit criteria of each cell, the cellwith the minimum value is selected as the handover cell.

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

The specific meaning of each bit is as follows:

Bits 1 to 3: Sequencing based upon the received level of each cell. It results from thesequencing of six candidate cells and one service cell according the received level(with the combination of the received level and the corresponding penalty).

Bit 4: the handover hysteresis comparing bit between cells of the same layer. Bit 3 ofthe service cell is zero all the time. When the received level of a neighboring cellsubtracted by the received level of the service cell is greater than the inter-cell

handover hysteresis, it is set as 0; when the received level of a neighboring cellsubtracted by the received level of the service cell is less than the inter-cell handoverhysteresis, it is set as 1.

Bits 5 to 10: Bits in handover layering and leveling. The bits are used for determinethe layers and priority levels (when the level of the neighboring cell or service cell islower than relationship between the inter-layer handover threshold and hysteresis,they will be screened and set as 0). There are 64 priorities.

Bit 11: Load adjusting bit. If the candidate cell is the service cell and the load isgreater than or equal to the local handover start threshold, then it is set as 1, or it willbe set as 0; if the candidate cell is the neighboring cell and the load is greater than orequal to the local handover receiving threshold, then it is set as 1, or it will be set as0. For the load handover start threshold and receiving threshold, please refer to the

load handover data table. No matter whether the load handover switch is opened ornot, the bit plays its due function.

Bit 12: Common BSC adjusting bit (i.e., sharing the same BSC). If the level of theneighboring cell or the service cell is lower than the relationship between the inter-layer handover threshold and hysteresis, it will be screened and set as 0.

Bit 13: Adjustment bit sharing the same MSC. When the level of the neighboring cellor service cell is lower than relationship between the inter-layer handover thresholdand hysteresis, they will be screened and set as 0.

Bit 14: Inter-layer handover threshold adjusting bit. Whether the level of theneighboring cell is higher than the inter-layer handover threshold + hysteresis or thelevel of the service cell is higher than the inter-layer handover threshold hysteresis.The bit is set as 0 or 1.

Bit 15: Cell type adjusting bit (mainly used for 70KM extended cell).

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1.3.5 Emergency Handover

The emergency handover means that the triggering of the handover is rapid. Atpresent, the emergency handover mainly destinations at four cases: High TA, poorreceiving quality, rapid decrease of received level and great interference. During

emergency handover, the best cell will be selected only according to the current cellsequencing, not multiple sequencing, so as to speed up the time responsecharacteristic of the system.

I. Handover caused by high TA

The timing advance can serve as a criterion for restricting cell size in a sense. TheBSC will judge whether the TA of the current MS exceeds the defined maximum TAthreshold TALIM (Timing Advanced LIMit). If it does, the BSC will originate anemergency handover due to high TA value.

II. Emergency handover caused by BQ

The transmission quality of links is measured with BER (Bit Error Ratio). The reason

of high BER may result from low signal power or channel interference.

III. Emergency handover caused by rapid level decrease

This is mainly used to judge the emergency handover due to rapid decrease of thereceived level of the MS. Since in this case, if the normal handover flow is used (i.e.,the handover is triggered when the received level of the MS is lower than the edgehandover threshold), then the MS may be disconnected without rapid trigger since itstill is making P/N decision. The judgement of rapid level decrease is the emphasis ofthis part. The decision method is to introduce the concept of fast filter.

For rapid level decrease, considering over fluctuation of the original level, it is plannedto filter the level for a short period of time and then to judge whether the level israpidly decreased with an appropriate filter (the filter is specially used to judge rapid

level decrease). The averaged filter length is set as QCKFALLLEN (3 by default).After filtering of the averaging filter, then use the filter for judging the rapid leveldecrease to conduct appropriate processing, shown as follows:

CF(nT) =m

i=0 C((n i)T) <

Where, C(nT) (when j=0) is the measured value of the current signal strength andC((n-j)T) is the corresponding measured result in the J th period (T) before the currentperiod.

IV. Emergency handover caused by uplink/downlink interference

If the BER of the link increases, but the received level is still high, then it is thoughtthat the channel has been interfered and the emergency handover due to

uplink/downlink interference will be originated.

1.3.6 Load Handover

The so-called load handover means that when the load of a cell is too heavy, then theload will be appropriately distributed to neighboring cells of low load so that the load isuniformly distributed over the whole network and to decrease the blocking rate. If theallowed identifier of load handover is set as HoClsAcc, then the system is allowed toperform load handover, i.e., the system allows the load to be handed over to itsneighboring cell and also it allows to accept the subscribers handed over due to loadreason, otherwise the cell neither can hand over subscribers to the neighboring celldue to heavy load nor the cell will accept the subscribers handed over from other cell.The traffic load handover can only be performed in cells of the same BSC. Thecurrent design supports the handover between different layers of the hierarchical

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network.

To implement the load handover function, first of all please judge whether the flowlevel of the current system is higher than the allowed load handover threshold(ClsSysFlowLvl). If it is, then the load handover will not be performed, so as toprevent great influence of load handover upon the overall system. During loadhandover, please judge whether the local of the cell where the subscriber is located ishigher than the load handover threshold (ClsLevel). If it is and also the subscriber iswithin the load handover area, then the subscriber will be handed over to theneighboring cell (if the load is lower than the received threshold ClsAcc, then theClsAcc must be lower than ClsLevel). The purpose of setting the load handover areais to prevent that too many subscribers are handed over to the neighboring cellsimultaneously. The load handover area refers to the area between the edgehandover threshold and the edge handover threshold plus load handover area offset(ClsOffset). Please refer to Figure 7-3.

Cel l A Cel l B

Normal handoverboundary

CONF_HO_RXLE

VCONF_HO_RXLEV+CLSRAM

P

CONF_HO_RXLEV+CLSOFFSE

T

Loadhandover

area

Figure 7-3 Schematic diagram of load handover

Thus, it can be seen that if the system permits the load handover, then all thesubscribers within the load handover area will become load handover objectssimultaneously and will be handed over to Cell B. This will exert great influence uponthe BSC processor and meanwhile it may lead to blocking of the destination cell.Therefore, please gradually hand over the load to Cell B. The gradual handover toCell B is controlled by classified load handover step (ClsRamp). When the loadhandover is allowed, the system allows the subscribers within CONF_HO_RXLEVand CONF_HO_RXLEV+ClsRamp to be handed over to Cell B and in the meantime,the system will start the load handover timer (TimerTCLS). When the timer reaches acertain time (ClsPeriod), the system allows the subscribers within CONF_HO_RXLEV

and CONF_HO_RXLEV +2*ClsRAMP to be handed over to Cell B. This processcontinues until all subscribers in the load handover area are handed over to Cell B.Hereafter, all subscribers in the load handover area can be handed over to Cell B.

Functions such as CRO, leveled traffic control, load handover and direct reuse, etc.

are applicable to abnormal traffic peak in local area of the radio network as

emergency measures or real hierarchical implementation, so they should not be

regarded as the main solutions to traffic congestion, since such means will change

the normal cell layout and will cause accidental network quality problems such as

strong signal fluctuation, etc. If a local area of the network always needs load

handover or direct reuse, then please consider adjusting the sector TRX configuration

of the base station and the network layout.

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1.3.7 Normal Handover

I. Edge handover

In N MRs, if P uplink levels of the MS or service cell are lower than the edge

handover threshold, then the edge handover will be triggered. The edge handoverrequires that the candidate cells should be in front of the service cell in the queue ofcandidate cells.

II. Leveled cell handover

The handover of dual frequency system is implemented through setting the cells asdifferent levels (CellLevel) and different priorities (CellPriority). That is to say, the dualfrequency system is regarded as a network. According to the actual requirements, theGSM1800 system can be set as higher priority. Here, please note the lower the level,the higher the priority and the lower the priority level, the higher the priority. Forexample: The cell of level 1 has a priority higher than the cell of level 2, and the cellwith priority set as 1 has a higher priority than the cell with a priority set as 2.

The cell leveling function is implemented through setting cell levels and priority ofcells in the same level. The cells are divided into four levels, and each level is dividedinto 16 priorities. After basic cell sequencing, the cells will be sequenced againaccording to the levels and priorities of the candidate cells, and the cell of high prioritywill be sequenced at the front. Thus, it is guaranteed that in the same condition, theMS will be handed over to cell of high priority preferably. Thus, the cell levels andpriorities will play function in the sequencing of the candidate cells to which the MSmay be handed over. This part is implemented in the network characteristic adjustingmodule of the handover algorithm.

The network characteristic adjusting module will simultaneously judge whether theneighboring cell and the service cell share the same BSC/MSC, because in order tomeet the requirements of independent networking and to reduce handovers betweenBSC and MSC as much as possible, and the priority of whether the cells share the

same BSC is higher than the leveled priority, therefore, the relationship between cellsshould be judged. Here, please set the On/Off of CO_BSC_MSC_TREATMENT. If it isset as On, then please adjust the queue of the candidate cells according to whetherthe neighboring cell and the service cell configured by the data management consoleshare the same BSC/MSC.

III. PBGT handover

In regions with dense network architecture, the actual radio coverage range is greatlylarger than the distance between base stations. Thus, if the MS keeps communicationin a cell, it cannot be effectively handed over to a closer cell needing lowertransmitting power. Therefore, it will lead to extra-cell coverage phenomenon, whichincreases interference upon the radio environment and influences networking

planning and optimizing. To solve this problem, please introduce the PBGT handoveralgorithm based upon path loss.

The PBGT handover algorithm is a handover algorithm based upon path loss. ThePBGT handover algorithm searches in real time whether there exists a cell which hassmaller path loss and meets certain system requirements and also it will judgewhether the handover is needed. The PBGT handover at least can bring about thefollowing advantages:

(1) Solving the problem of extra-cell coverage.

(2) Reducing the dual frequency handover times.

(3) Providing more flexible means for traffic guidance and control.

(4) Providing subscribers with best current service quality all along.

The GSM05.08 protocol describes the calculation of the PGBT in it appendix as

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follows:

PBGT(n) = (Min (MS_TXPWR_MAX,P) - RXLEV_DL - PWR_C_D)

- (Min (MS_TXPWR_MAX (n),P) - RXLEV_NCELL(n))

--Equal to the downlink received level of the neighboring cell -(Downlink received

level of the service cell + Power control level)

The meaning of each parameter is as follows:

MS_TXPWR_MAX: The maximum MS transmitting power allowed by the service cell

MS_TXPWR_MAX (n): The maximum MS transmitting power allowed by theneighboring cell n

RXLEV_DL: The downlink receiving power of the service cell

RXLEV_NCELL(n): The downlink receiving power of the neighboring cell n

PWR_C_D: The difference of the maximum downlink transmitting power of theservice cell and the actual downlink transmitting power of the service cell caused bypower control

P: The maximum transmitting power of the MSWhen PBGT(n) > HO_MARGIN(n), the PBGT handover can be triggered.

The triggering criterion of the PBGT handover is: If the path loss of the neighboringcell is less than the path loss of the service cell by a certain threshold and also meetsthe P/N criteria during a certain period of measurement time, then the PBGThandover will be triggered.

Specifically speaking, P measurements among N measurements meet PBGT(n) >PGBT_Ho_Margin(n).

Where P, N and PBGT_Ho_Margin(n) are set in the Data Management Console, andPBGT(n) is calculated according to the parameters configured through the DataManagement Console and the measurement results reported by the BTS.

In addition, the PBGT handover can only be performed between cells of the samelevel and priority and also can only be triggered in TCH channel.

IV. Speed sensitivity handover

The handover will be conducted according to the relative speed of the mobile stationso as to reduce the handover times and disconnection rate.

Here, we describe the speed sensitivity handover in the Active mode. Generally,portable mobile stations are relatively fixed, unreasonable extra-cell handover timeswill not be resulted even in dense mircocell network. However, there exists anotherproblem: A portable mobile station can be regarded as making fast motion relative tocell size. If processed by macrocell network, such rapid motion may lead to quite anumber of extra-cell handovers so that it is difficult to implement call control.Therefore, macrocells are used to provide service for these mobile stations with fast

motion so that the extra-cell handover times will not increase considerably. How tojudge whether a mobile station is making fast motion and what method should beused to hand over it to the macrocell are problems to solve.

Principle 1: If the mobile station is making fast motion relative to the microcellnetwork, the please hand over it to the macrocell network.

Principle 2: To prevent the fast mobile station registered in macrocell from enteringthe microcell network, time penalty should be applied to the microcell.

If the service cell is a macrocell:

To prevent the fast mobile station registered in macrocell from entering the microcellnetwork, time penalty should be applied to the microcell. If the penalty time of acertain neighboring cell is not 0, then when the neighboring cell passes the M criteria,

please start the time penalty timer. Subtract the received level of the cell by a largervalue before the timer is timeout so that the cell will be sequenced at the back of the

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queue of candidate cells. Generally, the MS will be handed over to this cell only inemergency handover.

If the service cell is a microcell:

This algorithm adopts the method of obtaining statistic of the microcells the MS

passes. Among the P microcells, if Q microcells think hat the MS is in fast motion,then the MS will be handed over the macrocell, and in the meantime, thecorresponding statistical parameter will be cleared.

1.3.8 Power prediction after handover

If the transmitting power after handover is the maximum transmitting power of theMSs allowed by the new cell, then perfect connection quality can be guaranteed evenfor MSs in the edge areas of the cell during extra-cell handover. However, if the MSsare very close to the base station during the extra-cell handover (especially when thedistance between base stations is very short), then it is unnecessary to use themaximum allowed transmitting power. Although the power control can rapidly reducethe transmitting power of a mobile station to an appropriate level, the RF power peak

after extra-cell handover may lead to uplink/downlink interference upon the radionetwork. Furthermore, excessive power level will shorten the battery life of the MS.Please refer to Figure 7-4.

Min(MS_TXPWR_MAX(n), P)

MS_TXPWR(n)

HOBTS1 BTS2

Figure 7-4 In case without handover power prediction

In fact, we can set the optimum uplink received level of the cell so as to guaranteeperfect communication quality during and after handover. Based upon this, we candeduce the optimized algorithm of the initial MS transmitting power after handover soas to replace the maximum allowed transmitting power with optimized initial MStransmitting power. It can also reduce the uplink power control times after handoverso that the uplink level can verge to the expected power control value faster.

Please define the following variables:

MS_TXPWR_MAX(n): The maximum MS transmitting power of mobile phone allowedby neighboring cell n

MS_TXPWR(n): The actual transmitting power of mobile phone allowed byneighboring cell n

BSPWR(n): Output power of the base station transmitter of neighboring cell n

BSTX_MAX(n): The maximum allowed transmitting power of neighboring cell n

PATH_LOSS_UL(n): The uplink path loss of neighboring cell n

PATH_LOSS_DL(n): The downlink path loss of neighboring cell n

RXLEV_NCELL(n): The downlink signal level of neighboring cell n

MsOptLevel(n): The optimum uplink received level of neighboring cell n

After handover, please guarantee that the uplink received level is a perfect value soas to prevent possible handover failure or call disconnection. This value isrepresented with the optimum received level.

When the received level of the base station approaches to the optimum uplink

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received level, the received level of the MS the received level of the base station,i.e., the received level of the MS is also approaches to the optimum uplink receivedlevel.

The difference between the received level of the MS and the optimum uplink receivedlevel reflects the difference between the maximum transmitting power of the basestation and the required transmitting power after handover. This difference is equal tothe difference between the maximum transmitting power of the MS and the requiredtransmitting power after handover.

Therefore, the calculation formula of the initial transmitting power of the MS afterhandover is as follows:

MS_TXPWR(n) MS_TXPWR_MAX(n) - Max(0,(RXLEV_NCELL(n)- MsOptLevel(n)))

Function Max( ) guarantees that the difference between the downlink level and theoptimum uplink received level of the destination cell is not negative.

To guarantee the calculated power is not beyond the MS capability and to set thelower limit (MSTX_LIM_MIN(n)) of the MS transmitting power so as to prevent too lowMS transmitting power due to improper parameter setting, then

MS_TXPWR(n) Max( Min( A, P ), MSTX_LIM_MIN(n) )

Where, A=MS_TXPWR_MAX(n)-Max(0,(RXLEV_NCELL(n) - MsOptLevel(n)))

M S _ T X P W R _ M A X ( n )

M S _ T X P W R ( n )

H OB T S 1 B T S 2

R X L E V _ N C E L L ( n )

M s O p t L e v e l ( n )

Figure 7-5 Case with handover power prediction

If the uplink power control of the destination handover cell is not opened, then theinitial transmitting power of the MS after handover should use the maximum allowedtransmitting power (not the optimum value). For inter-office handover, please do notcalculate the optimum value of the initial transmitting power of the MS after handover.

1.3.9 Concentric Circle Algorithm

The division of inner circle and excircle of Huawei concentric circle cell is based uponthe downlink received level and timing advance of mobile phones (such as Figure 7-6). According to the received level threshold and timing advance threshold, the borderof inner circle and excircle can be adjusted flexibly such that the inner circle andexcircle can reasonably share traffic in the precondition of guaranteeing variousnetwork indices.

The transmitting power of the inner circle is less than that of the excircle, so when asubscriber is in the inner circle area, then after the connection of inner circle has beenset up, the measured value of the service cell obtained from the MR (Measurement

Result) is based upon measured inner circle value of small power, while themeasured value of the neighboring cell is based upon measured excircle value of

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large power (indicating a kind of unequality). In this case, please make powercompensation for the inner circle so that the service cell will have equal position asthe neighboring cell during sequencing. The power difference of the inner circle andexcircle is generally the sum of the power difference of inner circle/excircle poweramplifier, insertion loss difference of combiners, path loss difference of difference

antennas and path loss difference of difference frequencies. If the inner circle andexcircle shares the same antenna, then please select any a test point, close theuplink power control function and set up communication connection in the inner circleand excircle respectively, and then measure the stable signal strength difference ofthe inner circle and excircle in communication state (the data is configured as thisdifference). If the inner circle and excircle does not share the same antenna, thenplease select three test points and test according to the previous method, and finallyaverage the difference.

In the figure, the TA threshold and path loss threshold are the thresholds preset by thesystem and the broken line stands for the actually configured threshold. There is ahysteresis between the value of the real limited area and the configured value.

The inner circle area can be expressed as:

received level > Received level threshold + Received level Hysteresis and TA


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I. Channel allocation technology of concentric circle cell

With the consideration of the characteristics of concentric circle cells, the channel

allocation technology of the concentric circle cell adopts different allocation policies

for different channel allocation conditions, mainly including the following conditions:

(1) Instant assignment

There are not the received level and TA for reference during the instant assignment.

To guarantee the service quality, the SDCCH channels in the excircle will be allocated

preferably. The signaling channels of the inner circle will be allocation only when

there is not any available signaling channel in the excircle.

(2) Assignment

The channel allocation policy of concentric circle is used for channel allocation.

Firstly, please judge the subscriber position according to the MR in SDCCH. Whenthe subscriber is within the inner circle range, then try best to allocate the inner circlechannels, and when there is not any available inner circle channel, then allocate theexcircle channels. Similarly, when the subscriber is within the excircle range, try bestto allocate the excircle channels, and when there is not any available excirclechannel, then allocate the inner circle channel, so as to implement the purpose thatthe appropriate service layer provides subscribers with appropriate services.

(3) Internal handover of BSC

It is applicable to non-concentric circle handover and direct handover to neighboringcell from the inner circle. The concentric circle channel allocation policy is used forchannel allocation such that the appropriate service layer will provide service formobile phones handed over to the cell. The basic principle is: through adding themeasured value of BCCH in the destination cell to the handover request messagebetween BSC cells, provide the values for concentric circle cell decision and selectthe service layer to allocate channels preferably. The decision method in this case isbasically the same as that of the concentric handover decision. However, the TA valueof the destination cell cannot be obtained, so the TA condition in the concentric circledecision cannot be considered.

(4) Inter-BSC handover

Since the received level and TA of the neighboring cell cannot be obtained, the modeof preferable inner circle/excircle selection without policy is applied with switchselection. For example, in ordinary networking condition, the inter-BSC handover istriggered at cell edges, so in this case the excircle channels can be selectedpreferably; While in dual frequency networking condition, 900/1800 shares the samestation in most cases, in such a case, if there is a great number of incoming

handovers (generally such handover is not triggered at cell edge), therefore, the innercircle channels can be selected preferably.

II. Concentric circle handover technology

Generally, the inner circle has more channels, so the traffic bearing capacity of theinner circle is far greater than the excircle. Therefore, if an MS sets up connection inthe excircle, then when the MS moves to the service area of the inner circle, it shouldbe handed over to the inner circle. The inner circle only has a limited coverage,therefore, if an MS sets up connection in the inner circle, then when the MS moves tothe border of the inner circle and excircle, the MS should be handed over to theexcircle channel so as to maintain the connection. In generally, the concentrichandover is inter-cell handover. In some special cases, maybe the MS needs to be

handed over to a neighboring cell directly from the inner circle, for example when the

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excircle is congested. Call disconnection may occur if the MS is not allowed to bedirectly handed over to the neighboring cell from the inner circle.

Decision criteria of concentric handover:

(1) Handover from excircle to inner circle

When the current service layer is the excircle, if P among N measurement timesmeets the following condition

Rxlev > Received level threshold +Received level Hysteresis Downlink powercontrol compensation,

and also

If TA < TA threshold - TA Hysteresis,

then handover from the excircle to the inner circle will be triggered. IN this case, if theinner circle does not have any available channel, it will directly return the handoverrejection message (the cause value is no available channel).

When the handover from the excircle to the inner circle is triggered, then thehandover to the neighboring cell is not allowed. Because, the condition for triggering

the handover from the excircle to the inner circle is that the received level of thecurrent service cell is higher than a threshold, while the inner circle has higher trafficbearing capacity and has higher priority level, so the concentric circle handover istriggered. However, in this case if the handover to the neighboring cell is triggered,the network optimization is not reflected and the handover may increase the excircleload of the neighboring cell. The handover from the excircle to the neighboring cellcan be implemented through other handover modes, such as PBGT handover, edgehandover, etc.

(2) Handover from inner circle to excircle

When the service layer is the inner circle, if P among N measurement times meets

Rxlev Received level threshold -Received level Hysteresis Downlink powercontrol compensation

or

If TA TA threshold + TA Hysteresis,

then the handover from the inner circle to the excircle will be triggered. When thehandover from the inner circle to the excircle is triggered, the direct handover to theneighboring cell is not allowed.

In this case, if the excircle does not have any available channel, then it will directlyreturn the handover rejection message (the cause value is no available channel).

Where, the meaning of each parameter is as follows:

Rxlev: The downlink received level of the current channel

Downlink power compensation: Due to power consumption of the current channelcaused by the downlink power control, the calculation is the current BS power levelmultiplied by 2. Please not that the BCCH TRX channel needs special processing.

P: P/N decision parameter, i.e., data configuration [Statistic time of concentriccircle handover]

N: P/N decision parameter, i.e., data configuration [Duration of concentric circlehandover]

1.4 Huawei Power Control Technology

The second generation of Huawei power control algorithm can implement thefollowing functions:

(1) MR (Measurement Result) compensation

(2) Filtering of predicted MR

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(3) Canceling initial adjustment stage (relative to the first generation of Huawei powercontrol algorithm)

(4) Adjusting power calculation decision optimization

After power control, the MR compensation is a kind of remedial measure to solve the

problem that the received level in the MR before power adjustment obviously cannotreflect the current receiving condition. These MRs may be used to estimate thecurrent receiving condition or to predict future MR values. For high accuracy,appropriate compensation should be made. The MR prediction filtering function ismainly an improved means for dealing with in sufficient power control hysteresis. Toachieve concise and explicit concept and in the meantime prevent the initialadjustment after introduction of accessed level optimization measure from becominga useless adjustment process, the initial power adjustment has been cancelled in thesecond generation of power control algorithm. Our main design considerationsinclude: firstly, put forward power adjustment requirements according to receivingquality and received level, and then implement the decision with combinedconsideration. Thus, the power control efficiency can be improved and the instabilityof the algorithm can be removed since such solution can bring about more

information for reference and better power control policy adjustment can beconducted.

MR queue compensation

Uplink MR prediction filtering

Yes

MS power processing

Yes

MS power processing

No No

M S p o w e r processing

MS power Control MS power processing

MR queue compensation

Is MR compensation allowed

Second generat ion of Huaweipower control algorithm

Yes

No

Figure 7-7 Flow diagram of the second generation of Huawei powercontrol algorithm

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1.4.1 MR Preprocessing

I. MR compensation

Every time when an MR is received, the MR will be placed in the MR queue to serve

as the original materials for power control and handover decision. To make decision,take integrated consideration of certain number of new MRs. We had such anassumption before that these MRs were obtained in the condition of constanttransmitting power. Thus, if we found that the average received level had changed,we thought that the path loss had changed, so the change would be compensated onthe basis of the current transmitting power. However, the present situation is that,these latest MRs possibly are obtained in different transmitting power conditions.Thus, the method of using the MRs before power adjustment to estimate the receivedlevel in current transmitting power condition will surely lead to error. To reduce sucherror, the MRs before power adjustment should be compensated. The specificmethod is to compensate the received level for the historical MRs at the momentwhen the power adjustment changes (considering adjustment delay, we can judgewhether the transmitting power has changed according to the actual MRs).

The MR compensation after power adjustment is to guarantee the accuracy of the MRprediction function of the second generation of power control algorithm.

II. Prediction filtering

The power control is a process of transmitting power control based upon the currentreceived level and the receiving quality. The sending and transmission of powercontrol command and power adjustment will take certain period of time, so there willexist certain hysteresis between the receiving change and corresponding transmittingpower adjustment. If the hysteresis is very severe, then the transmitting powerchange not only cannot compensate the receiving change, but to the contrary, it willaccelerate this change, so the power adjustment cannot play its due active function.In general, after the transmitting power adjusment command on the uplink is sent out,

the transmitting power will be adjusted after three MRs. However, after the poweradjustment command on downlink is sent out, the transmitting power will be adjustedimmediately. Therefore, the power control hysteresis is mainly applied to the uplinks.It can be predicted that, the delivering of power control command in advance willfacilitate the effective control of the received level, which is beneficial to stablereceived level and high receiving quality.

The basic principle of the prediction filtering is: Firstly, calculate the weighed meanvalue (P1) of the received levels in N1 MRs approaching to the calculation moment,and then calculate the weighed mean value (P2) of N2 points before N1 points, andfinally predict received level (Py) of the subsequent points according to N1 and N2.

Thus, the prediction filtering value of the received level is: Py=P1 + (P1-P2) a (astands for the amplification coefficient)

Here, the time weighing is used. The newer the MRs is, the larger the weighed valuewill be. As, the newer MRs reflect comparatively current situations more accurately.

This value can be directly used during average decision of power control. This valuecan also serve as a new MR to predict the next reference value with the samemethod, and so on. To improve the system controllability, the prediction times can beset in the background.

1.4.2 Second Generation of Huawei Power Control Policy

According to the actual communication state based upon different power adjustmentrequirement combinations, the second generation of Huawei power control algorithmadopts pertinent power control policy so as to guarantee the validity and stability of

the power control algorithm. The following three steps are taken for the calculation of

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adjustment power:

I. Calculating adjustment power step according to the received level(AdjStep_Lev)

To improve the system flexibility and to prevent power control fluctuation, the dual-threshold power control policy is used. To guarantee rapid and accurate positioning ofthe power adjustment, the variable step power control is used. Please refer to thecurrent receiving quality in final determination of step adjustment, because accordingto our estimation of the actually measured results, different receiving quality valuescorrespond to different average received levels. Generally, the corresponding averagereceived level when the receiving quality is 0 is far greater than the average receivedlevel when the receiving quality is not 0. When the receiving quality is not 0, theaverage received levels are almost the same. When the receiving quality is 0, if thereceived level requires that the transmitting power should be decreased by 6dB, thenafter the power adjustment, the receiving quality is possibly 0. Thus, the power controlis implemented. When the receiving quality is 1, then similarly, if the received levelrequires that the transmitting power should be decreased by 6dB, then after the

power adjustment, the receiving quality possibly turns to 4. Thus, the receiving qualitymay require higher transmitting power. Therefore, the power adjustment just now isnot as good as that when the receiving quality is 0. With such consideration, we takethe measure of appropriately referring to the current receiving quality in theadjustment step based upon the power of the received level, so as to better matchwith the actual situations and to make the power adjustment more efficient. Based onthe first generation of Huawei power control algorithm, the second generation ofHuawei power control algorithm has been improved with direct requirements forcontrol target. The adjustment step based upon the final power of the received levelwill use the smaller one of the following two values.

(1) The adjustment step AdjStepThr_Lev based upon the comparison of the actualreceived level and the threshold.

When the received level is low, the power will increase.

In this case we can judge that when RxlevPcUpperThresoldsLev,

AdjStepThr_Lev=DecrStep_Lev

=Rxlev-(PcUpperThresoldsLev+PcLowerThresoldsLev)/2

When the received level falls between the upper threshold and thelower threshold, the transmitting power will not be adjusted.

In this case, when we judge that when PcUpperThresoldsLev Rxlev PcLowerThresoldsLev, the transmitting power will not be adjusted.

In the above formula, the data:

Rxlev is the actual received level after prediction filtering.

PcLowerThresoldsLev PcUpperThresoldsLev stands for the upper/lower threshold,which is set through the background. The distance between the two thresholds shouldnot be too great, or the power control will be not so sensitive to the change of thereceived levels and will lead to greater fluctuation of the received levels. However, italso should not be too small, or the power control will be too sensitive to the changeof the received levels, which will lead to power control fluctuation easily and willexcessively restrict the improvement space of the transmitting power due to lowreceiving quality. It is recommended that the appropriate distance be 6 to 10dB. The

range can float upwards/downwards according to the actual requirements.

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IncrStep_Lev, DecrStep_Lev and AdjStepThr_Lev are the calculated values,respectively standing for increased power step, decreased power step and theadjustment step based upon the comparison of the received level and threshold.

(2) The maximum reference adjustment step of the current receiving quality(CurQulMaxStep). For the convenience of more effective adjustment, some actualreceiving conditions are taken into consideration. The receiving quality is divided intothree quality areas (0, 1 to 2, above 3), and each quality area specifies a maximumreference adjustment step (can be set in the background). The higher the receivingquality is, the greater the step. The lower the quality, the smaller the step, because inthis case, the system faces more interference and is quite sensitive. Thus it facilitatesin guaranteeing the stability of the algorithm. The setting of the maximum allowedadjustment for each quality area is based upon two aspects: (a). The setting shouldnot be too small, or the algorithm cannot attain the purpose of fast power control. (b).The setting cannot be too great, or the due reference function cannot beimplemented, which will lead to decreased power control validity. It is recommendedthat the maximum reference adjustment step of quality area 0 be 8 to 16dB, that ofquality area 1 be 4 to 8dB and that of quality area 2 be about 3dB or 4dB.

The adjustment step calculated according to the received level is: AdjStep_Lev =min(AdjStepThr_Lev, CurQulMaxStep).

II. Calculating adjustment power step (AdjStep_Qul) according to receivingquality

Generally, the receiving quality varies with interference. The main interference in theGSM system is the cofrequency interference generated during frequencymultiplexing. This interference is mutual, the increased power of a call is equivalent tothe increased interference of another call. Therefore, please pay attention to thepower adjustment caused by receiving quality change so as to prevent the viciouscycle of improving transmitting power due to low quality. The result of such groupeffect is that all GSM systems use the maximum transmitting power, but the receivingquality is not improved at all.

The receiving quality threshold is also set as dual threshold. The transmitting powerwill not be adjusted for receiving quality within the quality area, but the transmittingshould be adjusted for those out of the quality area. Because you cannot estimate theinfluence of the transmitting level change upon the receiving quality, and furthermore,to guarantee the stability of the algorithm, please try to prevent large step duringpower adjustment. We have used the fixed step. This value can be set in thebackground.

(1) Improving transmitting power for low receiving quality

If Qulity>PcbadThresoldsQul, please increase the transmitting power and increasethe step to AdjStep_Qul.

(2) Decreasing transmitting power for high receiving quality

If Qulity


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quality improvement is based upon the transmitting power increase. In this case, thereceiving quality is very poor, so please increase the transmitting power gradually. It isrecommended that the value be set as 2 to 4dB.

III. Combining the two power control requirements

When taking the two requirements into combined consideration, on one hand, try bestto meet its requirements, and on the other hand, when the two requirements are notconsistent or completely opposite, then please consider the stability of the algorithmand forbid unstable adjustment. Based upon the above principles, the following poweradjustment table is obtained:

Adjust step according toreceived level

Adjust step according toreceiving quality

Take adjustment resultsinto comprehensive

consideration

Reduce AdjStep_Lev Reduce AdjStep_QulReduce Max (AdjStep_Lev,

AdjStep_Qul)Reduce AdjStep_Lev Add AdjStep_Qul No actionReduce AdjStep_Lev No action Reduce djStep_Lev

Add AdjStep_Lev Add AdjStep_QulAdd Max(AdjStep_Lev,

AdjStep_Qul)Add AdjStep_Lev Reduce AdjStep_Qul Add AdjStep_LevAdd AdjStep_Lev No action Add AdjStep_Lev

No action No action No actionNo action Reduce AdjStep_Qul Reduce AdjStep_QulNo action Add AdjStep_Qul Add AdjStep_Qul

Furthermore, besides the adjustment as shown in the above table, please payattention to the power control fluctuation due to mutual action of the received leveland the receiving quality. For example, after, the transmitting power should bedecreased by 4dB according to the received level, the poor receiving quality requiresan increase of 4dB, and after than the received level again requires an increase f4dB. Thus, the fluctuation is generated due to cyclic increase/decrease. The method

to avoid such fluctuation is: If only the receiving quality has power adjustmentrequirement, then please check after the adjustment, whether the received level willexceed the dual-threshold range. If it will, then please do not conduct the poweradjustment, so as to avoid power control fluctuation. Thus, we can obtain the powerstep to be finally adjusted. The uplink/downlink adjustment policies should beconsistent.

1.5 New Channel Allocation Algorithm

The new channel allocation algorithm is based upon the optimization mechanism.Comparing with the classical first generation of channel allocation algorithm basedupon rotation, the new channel allocation algorithm can provide subscribers withcommunication channels as good as possible.

The new channel allocation algorithm considers the following optimization fact

22066459 Chapter7 Parameter Design

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