Soft Channel Capacity in BSC

Soft Channel Capacity in BSC

DN03499862Issue 3-1 en

# Nokia Corporation 1 (25)

BSC3119Nokia BSC/TCSM, Rel. S12, ProductDocumentation, v.1

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2 (25) # Nokia Corporation DN03499862Issue 3-1 en


Contents

Contents 3

List of tables 4

List of figures 5

Summary of changes 7

1 Overview of Soft Channel Capacity in BSC 9

2 Requirements for Soft Channel Capacity in BSC 11

3 Technical description of Soft Channel Capacity in BSC 133.1 BSC radio network configuration with Soft Channel Capacity in BSC 133.2 Radio channel allocation with Soft Channel Capacity in BSC 143.3 Interworking 16

4 User interface of Soft Channel Capacity in BSC 23



Contents

List of tables

Table 1. Maximum number of TCHs per BCSU 13

Table 2. Maximum number of simultaneously active TCHs per BCSU 14

Table 3. Number of active TCHs depending on the activation type 15

Table 4. Soft Channel Capacity interworking 17



List of figures

Figure 1. Example of active traffic channel limits per BCSU 14

Figure 2. Example of cell capacity assurance algorithm 16



List of figures



Summary of changes

Changes between document issues are cumulative. Therefore, the latest documentissue contains all changes made to previous issues.

Changes made between issues 3-1 and 3-0

Information on Inter-System Direct Access has been removed from Technicaldescription of Soft Channel Capacity in BSC, as it is no longer relevant.


Chapter Overview of Soft Channel Capacity in BSC

Other related topics in BSC/TCSM documentation have been updated.

Chapter Technical description of Soft Channel Capacity in BSC

Nokia BSC3i High Capacity Base Station Controller has been added to tables 1and 2. CS connection of DTM call has been added to table 3.



Trunk Reservation has been added to table 4.

Chapter User interface of Soft Channel Capacity in BSC

Error code TOO MANY SCC CHANNEL PER AMR HR CHANNEL IN BSCUhas been replaced with error code AMOUNT OF SOFT CHANNELS IN BSCEXCEEDS AMR HR LICENCE CAPACITY.





Summary of changes

Counters of Soft Channel Capacity measurement and Traffic measurement havebeen added.


Chapter Overview of Soft Channel Capacity in BSC

Information on licensing added.

Chapter Requirements for Soft Channel Capacity in BSC

Information on half rate TRX licences removed.

Information that Soft Channel Capacity requires that AMR HR is in use added.


Figure 2 changed: information on TRX 4 assured TCH capacity added to BTS 4.


New sections Error codes,Alarms, and Counters added.

The document has also been revised throughout to comply with the latestdocumentation standards.



1 Overview of Soft Channel Capacity inBSC

Soft Channel Capacity increases the traffic channel (TCH) limit on the BSC2i andBSC3i platforms. The existing limit of the number of traffic channels per BSC isdoubled. You are allowed to configure all the radio traffic time slots of all the halfrate (HR) capable TRXs to dual rate (DR) support. The overall traffic processingcapacity of the BSC is not increased. The traffic processing capacity of the BSCremains on the level defined in Product Descriptions.

Soft Channel Capacity is a licence-based software. Its use is controlled by acapacity licence based on the number of TRXs. With one TRX licence you canhave eight additional AMR HR channels. For more information on Licensing, seeLicensing in BSC.

Benefits

With Soft Channel Capacity you can fully utilise the AMR HR applicationsoftware in the existing networks without deploying more BSCs. With SoftChannel Capacity it is possible to configure all radio traffic time slots to dual ratesupport.

Related topics in description

. Requirements for Soft Channel Capacity in BSC

. Technical description of Soft Channel Capacity in BSC

. User interface of Soft Channel Capacity in BSC

Other related topics in BSC/TCSM documentation

. Plan. Transmission

. Nokia BSS Transmission Configuration

. Reference. Counters



Overview of Soft Channel Capacity in BSC

. 1 Traffic Measurement

. 2 Resource Availability Measurement

. 109 Soft Channel Capacity Measurement. Parameters

. BSS Radio Network Parameter Dictionary. Printouts/Error codes

. General Error Messages of System

. Descriptions. Product Descriptions

. Product Description of Nokia BSC2i and BSCi High CapacityBase Station Controller

. Product Description of Nokia BSC3i High Capacity BaseStation Controller

. Functional Area Descriptions. Radio Network Performance

. Radio Channel Allocation

. Traffic Reason Handover in BSC. Operability

. Licensing in BSC. Feature Descriptions

. Radio Network Performance. GSM-WCDMA Interworking. Common BCCH Control in BSC. Enhanced Speech Codecs: AMR and EFR. Direct Access to Desired Layer/Band

. Data. (E)GPRS in BSC. HSCSD and 14.4 kbit/s Data Services in BSC

. Value Added Services. Wireless Priority Service in BSC



2 Requirements for Soft Channel Capacityin BSC

Software requirements

Soft Channel Capacity requires that AMR HR is in use.

Hardware requirements

Soft Channel Capacity requires BSC2i or BSC3i.

In BSC2 the existing limit on number of traffic channels per BSC is not changed.

TRXSIG Capacity

The restrictions set by the TRXSIG capacity are also valid with Soft ChannelCapacity. You should not create more radio channels per TRX than recommendedin Nokia BSS Transmission Configuration.

Related topics




Requirements for Soft Channel Capacity in BSC



3 Technical description of Soft ChannelCapacity in BSC

3.1 BSC radio network configuration with Soft ChannelCapacity in BSC

With Soft Channel Capacity the limit of the number of traffic channels (TCHs)per BCSU is doubled. The new limits are shown in table Maximum number ofTCHs per BCSU.

Table 1. Maximum number of TCHs per BCSU

BSC type Number of TCHs in the BCSU

BSC2i 1024

BSC3i 660 1760

BSC3i 1000/2000 3200

With these new limits it is possible to configure all radio traffic time slots to dualrate support. Increasing the limits means that more TCHs can be created in theradio network than are allowed to be activated simultaneously. This is extra TCHcapacity.

Related topics




Technical description of Soft Channel Capacity in BSC

3.2 Radio channel allocation with Soft ChannelCapacity in BSC

Maximum number of simultaneously active traffic channels per BCSU

The limits of the number of simultaneously active traffic channels (TCHs) perBCSU are shown in table Maximum number of simultaneously active TCHs perBCSU.

Table 2. Maximum number of simultaneously active TCHs per BCSU

BSC type Number of simultaneously activeTCHs in the BCSU

BSC2i 512

BSC3i 660 880

BSC3i 1000/2000 1600

The number of active traffic channels per BCSU is maintained in the BSC. TheRadio Resource Management part of the BSC controls the usage of trafficchannels. If the number of active traffic channels in the BCSU reaches the limitvalue, it is not possible to activate a new traffic channel in the TRXs controlled bythat BCSU until an active traffic channel has been released. Below is an exampleof active traffic channel limits per BCSU.

Figure 1. Example of active traffic channel limits per BCSU

BSC2i

BCSU 1: 600 TCHs created512 TCHs active


TRX 1

BTS 1

TRX 2

TRX 3

BCSU 1

BCSU 3

BCSU 2




In the example above it is not possible to allocate a traffic channel in TRX 1 or inTRX 2. In BCSU 1 the maximum number of traffic channels is already activated.In BCSU 2 all the traffic channels are already activated. It is possible to allocate atraffic channel only in TRX 3. If TRX 3 happens to be in use already, it is notpossible to allocate a traffic channel in the cell even if there were free channels inTRX 1.

The principles of calculating the number of active traffic channels are describedin table Number of active TCHs depending on the activation type.

Table 3. Number of active TCHs depending on the activation type

Activation type Number of active TCHs

Full rate single slot CS call 1

Half rate single slot CS call 1

2 time slot multislot CS data call 2



(E)GPRS territory time slot 1

Dynamic SDCCH time slot 1

CS connection of DTM call 1

Cell capacity assurance

Cell capacity assurance algorithm ensures that a sufficient number of trafficchannels can be activated in each cell of the network at any time even if there isextra TCH capacity created in the radio network. This algorithm assures that theminimum number of the calls that can be set up in each cell of the network at anytime is equal to the number of the created TCH TSLs in the cells, that is, the cellcapacity assurance level is 100%.

Below is an example of the cell capacity assurance algorithm.




Figure 2. Example of cell capacity assurance algorithm

The assured TCH capacity of BTS 1, 2, and 3 together is 18 traffic channels. Only6 traffic channels are currently active in those BTSs. The maximum number ofsimultaneously active traffic channels in BCSU 1 is 512. Five hundred (500) ofthem are already active. Thus it is not possible to activate a traffic channel inTRX 4 of BTS 4. The free resources of BCSU 1 must be saved for BTS 1, 2, and3 to assure sufficient number of calls in each of the BTSs. In BTS 4 it is possibleto allocate a traffic channel only in TRX 5 at the moment.

Related topics


3.3 Interworking

The extra TCH capacity created in the radio network has effects on variousoperating and application software in the BSC. The effects are described below.

BTS 1: assured capacity6 TCHs2 active TCHs


BSC2i





TRX 1

BTS 1

TRX 3

BTS 3BCSU 1

TRX 2

BTS 2

TRX 5

TRX 4

BTS 4BCSU 2

BTS 4: TRX 4 assured TCHcapacity activated



Table 4. Soft Channel Capacity interworking

Operating/application software Interworking

Congestion time The BSC starts the congestion time if the number ofidle channels in the BTS goes to zero. If there isextra TCH capacity created in the BTSs, it is possibleto have the radio channel allocation attempts rejectedbecause of a lack of traffic handling capacity in theBCSU even if the congestion time is not shown in thestatistics.

Intra-BTS handovers due to (E)GPRS or HSCSD Intra-BTS handovers are started for the single-slotcircuit switched (CS) calls in the BSC to enable the(E)GPRS territory upgrade or the HSCSD upgrade.The BSC starts these handovers based on thenumber of idle channels in the BTSs. If there is extraTCH capacity created in the BTSs, it is possible tohave handover attempts started and rejectedbecause of a lack of traffic handling capacity in theBCSU although there are idle channels in the BTSs.

For more information, see (E)GPRS in BSC andHSCSD and 14.4 kbit/s Data Services in BSC.

(E)GPRS margins The (E)GPRS territory upgrade and downgradedecisions are based on the number of idle time slotsin the BTS. If there is extra TCH capacity created inthe BTS, the downgrade margin does not workoptimally. The (E)GPRS territory downgrade causedby the increasing CS traffic is not started as early asin the situation without extra TCH capacity. Theeffects can be reduced by setting the BSCparameters free TSL for CS upgrade (CSU) andfree TSL for CS downgrade (CSD) to maximumvalues.

For more information, see (E)GPRS in BSC.




Table 4. Soft Channel Capacity interworking (cont.)


Wireless Priority Service in BSC The Wireless Priority Service (WPS) in BSC is anapplication software. The Radio Channel Allocationfor the Public (RCAP) algorithm is based on the trafficload situation in the cell. The BSC checks the cellresource usage based on the BSC parameters: WPSpriority capacity (WPIC) and WPSpreference capacity (WPEC). If there is extraTCH capacity created in the cell, it is possible thatthe round robin allocation is invoked too late andthere is no resources available for an incoming Publicuser in the cell. This situation can be avoided byreducing the values of the WPIC and WPECparameters and increasing the value of the BSCparameter: public served count (PSC). Thevalues of the WPIC and WPEC parameters should bereduced in relation to the amount of extra TCHcapacity in the network. If the number of TCHs hasbeen doubled in the network, the values of theparameters should be halved.

For more information, see Wireless Priority Service inBSC and BSC radio network object parameters inBSS Radio Network Parameter Dictionary.

Directed Retry for queued WPS user The BSC checks the cell resource usage of the targetcells based on the BSC parameters: WPS prioritycapacity (WPIC) and WPS preferencecapacity (WPEC). If there is extra TCH capacitycreated in the cell, it is possible that a Directed Retryhandover for a queued WPS user is started to a cellwhich actually is congested and the WPS call setupis interrupted. This situation can be avoided byreducing the values of the WPIC and WPECparameters. The values of these parameters shouldbe reduced in relation to the amount of extra TCHcapacity in the network. If the number of TCHs hasbeen doubled in the network, the values of theparameters should be halved.

For more information, see Wireless Priority Service inBSC and BSC radio network object parametersinBSS Radio Network Parameter Dictionary.





BSC initiated Traffic Reason Handover (BSC TRHO) The BSC initiated traffic reason handover is a part ofan Advanced Multilayer Handling application softwarein the BSC. The BSC checks the traffic load situationin the serving cell based on the BSC/BTS parameter:AMH upper load threshold (AUT). If the trafficload of the serving cell exceeds the AUT parameter,the BSC tries to hand over calls to other less loadedcells. If there is extra TCH capacity created in theserving cell, the handovers are started later thanwithout extra capacity. It is possible that the cell isalready congested but the handovers are not startedbecause of the extra TCH capacity. The effects canbe minimised by reducing the value of the AUTparameter.

The load of the target cell in the BSC TRHO attemptis checked based on the BSC/BTS parameter: AMHmax load of target cell (AML). If the traffic loadin the target cell is below the AML parameter, the callis handed over to the target cell. The aim is to avoidmaking handovers from one congested cell toanother. If there is extra TCH capacity created in thetarget cell, the handover can be made to a cell whichalready is almost congested. The effects can beminimised by reducing the value of the AMLparameter. The values of the AUT and AMLparameters should be reduced in relation to theamount of extra TCH capacity in the network. If thenumber of TCHs has been doubled in the network,the values of the parameters should be halved.

For more information, see RF Power Control andHandover Algorithm.

MSC initiated TRHO The BSC reports the number of idle traffic channelsin the cells to the MSC. If there is extra TCH capacitycreated in the cell, it is not necessarily possible toallocate all the reported idle channels of a cellsimultaneously. As a consequence the MSC maystart handovers from one congested cell to another.

For more information, see Traffic Reason Handover inBSC.






Direct Access to Desired Layer/Band (DADL/B) DADL/B is an application software in the BSC. WhenDADL/B is activated, the BSC checks the traffic loadsituation in the accessed cell based on the BTSparameter: BTS load threshold (BLT). If thetraffic load of the accessed cell exceeds the BLTparameter, the BSC tries to direct the call to anotherlayer or band of the network. If there is extra TCHcapacity created in the accessed cell, the calls arenot directed to another layer or band as early aswithout extra TCH capacity. The effects can beminimised by reducing the value of the BLTparameter. The value of the BLT parameter should bereduced in relation to the amount of extra TCHcapacity in the network. If the number of TCHs hasbeen doubled in the cell, the value of the parametershould be halved.

For more information, see Direct Access to DesiredLayer/Band.

Load distribution between BTSs of the segment The load distribution between different BTSs in asegment is controlled with the BTS parameter: BTSload in SEG (LSEG). For each call the BSC checksthe resource usage of each BTS of the targetsegment based on the LSEG parameter . The BSCthen decides to which BTS the call is directed. Theaim is to keep the load of each BTS within the limitthat the LSEG parameter defines. If there is extraTCH capacity created in the segment, the calls arenot directed, for example, to a non-BCCH layer of thesegment as early as without extra TCH capacity. Theeffects can be minimised by adjusting the value ofthe LSEG parameter. The value of the LSEGparameter should be reduced in relation to theamount of extra TCH capacity in the network. If thenumber of TCHs has been doubled in the BTS, thevalue of the parameter should be halved. However, ifthe value of the LSEG parameter has already beenset to a low value (about 10% or lower), there is notnecessarily any need to change the value. In thiscase the load distribution between layers in thesegment works well also with the extra TCH capacity.

For more information on the load distribution betweenthe BTSs of the segment, see Common BCCHControl in BSC.





Dynamic SDCCH reconfiguration The last idle TCH TSL of a cell is not supposed to bereconfigured to SDCCH. In case of the last idle TCHTSL the FACCH call setup is applied. However, ifthere is extra TCH capacity created in the cell, it ispossible that the dynamic SDCCH reconfigurationcauses temporary TCH congestion in the cell.

For more information on Dynamic SDCCH, see RadioChannel Allocation.

GSM-WCDMA Inter-System Handover (ISHO) The GSM-WCDMA Inter-System Handover (ISHO)from a GSM to a WCDMA RAN cell for speech callsis started on the basis of the traffic load in the servingGSM cell. The load in the serving cell is checked withthe handover parameter: min traffic load forspeech call (LTSC). The handover is not starteduntil the load in the serving cell exceeds thethreshold. If there is extra TCH capacity created inthe serving cell, the handovers to the WCDMA RANcell are not started as early as without extra TCHcapacity. The effect can be minimised by reducing thevalue of the LTSC parameter. The value of the LTSCparameter should be reduced in relation to theamount of extra TCH capacity in the network. If thenumber of TCHs has been doubled in the cell, thevalue of the parameter should be halved.

For more information on ISHO, see GSM-WCDMAInterworking.

Trunk Reservation Trunk Reservation does not work optimally if extraTCH capacity has been created in the BSC. TheTrunk Reservation algorithm takes into account all thecreated radio interface traffic channels. If extra TCHcapacity has been created in the BSC, the TrunkReservation algorithm cannot ensure that there isalways capacity available for the priority user in acell.

Related topics







4 User interface of Soft Channel Capacityin BSC

MML commands

. Transceiver Handling (command group ER)

With the ERM command you can modify the full rate (FR) radio time slotsto dual rate (DR) support.

. Base Station Controller Parameter Handling (command group EE)

With the EEI command you can check the number of real TCHs underBCSUs.

. Licence and Feature Handling (command group W7)

With the W7I command you can check the status of the licence.

With the W7M command you can modify the status of the licence.

Error codes

. SOFT CHANNEL CAPACITY LICENCE EXCEEDED

With this error code the BSC informs you that the maximum amount ofsoft channels in the BSC is exceeded.

. AMOUNT OF SOFT CHANNELS IN BSC EXCEEDS AMR HR LICENCECAPACITY

With this error code the BSC informs you that there are more soft channelsconfigured in the BSC than AMR HR licence allows.

. SOFT CHANNEL CAPACITY FEATURE IS NOT IN USE IN BSC

With this error code the BSC informs you that Soft Channel Capacity is notin use in the BSC.

For more information, see Licensing in BSC and General Error Messages ofSystem.



User interface of Soft Channel Capacity in BSC

Alarms

7746 CH CONGESTION IN CELL ABOVE DEFINED THRESHOLD

Because of Soft Channel Capacity there is a new field in this alarm.

For a more detailed description of this alarm, see Base Station Alarms (7000–7999).

Counters

The following new counters to Soft Channel Capacity measurement areintroduced:

. 109000 PEAK BUSY TCH PER BCSU

. 109001 AVE BUSY TCH PER BCSU

. 109002 AVE BUSY TCH PER BCSU DENOMINATOR

. 109003 TOTAL TCH BUSY TIME PER BCSU

Also the following counter is added to Traffic measurement:

. 001216 TCH REQ REJ DUE TO LACK OF RES PER BCSU

When Soft Channel Capacity is active and there are extra TCHs created in a cell,it is possible that radio channel allocation attempt is rejected because of the lackof BCSU capacity even if there are free radio traffic channels in the cell. In thiscase the existing traffic measurement and resource availability counters areaugmented as if the radio channel allocation attempt was rejected because of alack of radio resources. The following counters are an exception:

. 2026 TOTAL CHANNEL BUSY TIME

. 2044 FULL RATE radio CONGESTION TIME

. 2045 HALF RATE radio CONGESTION TIME

These counters do not show congestion time unless all the radio traffic channelsof the cell have been occupied.

For more information, see

. 1 Traffic Measurement

. 2 Resource Availability Measurement

. 109 Soft Channel Capacity Measurement



Related topics




User interface of Soft Channel Capacity in BSC

Documents

Soft Channel Capacity in BSC