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Soft Channel Capacity in BSC
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# Nokia Siemens Networks 1 (25)
BSC3153
Nokia GSM/EDGE BSS, Rel. BSS13, BSC and
TCSM, Rel. S13, Product Documentation, v.1
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The information in this document is subject to change without notice and describes only theproduct defined in the introduction of this documentation. This documentation is intended for theuse of Nokia Siemens Networks customers only for the purposes of the agreement under whichthe document is submitted, and no part of it may be used, reproduced, modified or transmitted inany form or means without the prior written permission of Nokia Siemens Networks. Thedocumentation has been prepared to be used by professional and properly trained personnel,and the customer assumes full responsibility when using it. Nokia Siemens Networks welcomescustomer comments as part of the process of continuous development and improvement of thedocumentation.
The information or statements given in this documentation concerning the suitability, capacity, orperformance of the mentioned hardware or software products are given as is and all liabilityarising in connection with such hardware or software products shall be defined conclusively andfinally in a separate agreement between Nokia Siemens Networks and the customer. However,Nokia Siemens Networks has made all reasonable efforts to ensure that the instructionscontained in the document are adequate and free of material errors and omissions. NokiaSiemens Networks will, if deemed necessary by Nokia Siemens Networks, explain issues which
may not be covered by the document.
Nokia Siemens Networks will correct errors in this documentation as soon as possible. IN NOEVENT WILL NOKIA SIEMENS NETWORKS BE LIABLE FOR ERRORS IN THISDOCUMENTATION OR FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO SPECIAL,DIRECT, INDIRECT, INCIDENTAL OR CONSEQUENTIAL OR ANY LOSSES, SUCH AS BUTNOT LIMITED TO LOSS OF PROFIT, REVENUE, BUSINESS INTERRUPTION, BUSINESSOPPORTUNITY OR DATA, THAT MAY ARISE FROM THE USE OF THIS DOCUMENT OR THEINFORMATION IN IT.
This documentation and the product it describes are considered protected by copyrights andother intellectual property rights according to the applicable laws.
The wave logo is a trademark of Nokia Siemens Networks Oy. Nokia is a registered trademark ofNokia Corporation. Siemens is a registered trademark of Siemens AG.
Other product names mentioned in this document may be trademarks of their respective owners,and they are mentioned for identification purposes only.
Copyright Nokia Siemens Networks 2008. All rights reserved.
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Contents
Contents 3
List of tables 4
List of figures 5
Summary of changes 7
1 Overview of Soft Channel Capacity 9
2 Requirements for Soft Channel Capacity 11
3 Technical description of Soft Channel Capacity 133.1 BSC radio network configuration with Soft Channel Capacity 133.2 Radio channel allocation with Soft Channel Capacity 143.3 Interworking 16
4 User interface of Soft Channel Capacity 23
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Contents
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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
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List of figures
Figure 1. Example of active traffic channel limits per BCSU 14
Figure 2. Example of cell capacity assurance algorithm 16
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Summary of changes
Changes between document issues are cumulative. Therefore, the latest
document issue contains all changes made to previous issues.
Changes made between issues 4-0 and 3-1
Information on radio network recovery has been added to table Soft
Channel Capacity interworking in chapter Technical description of Soft
Channel Capacity.
Changes made between issues 3-1 and 3-0
Information on Inter-System Direct Access has been removed fromTechnical description of Soft Channel Capacity in BSC, as it is no longer
relevant.
Changes made between issues 3-0 and 2-2
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 1 and 2. CS connection of DTM call has been added to table 3.
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1 Overview of Soft Channel CapacitySoft Channel Capacity increases the traffic channel (TCH) limit on the
BSC2i and BSC3i platforms. The existing limit of the number of TCHs perBSC is doubled. You can configure all the radio traffic timeslots of all the
half rate (HR) capable TRXs to dual rate (DR) support. The overall traffic
processing capacity of the BSC is not increased. The traffic processing
capacity of the BSC remains on the level defined in the BSC2i and BSC3i
product descriptions.
Soft Channel Capacity is a licence-based application software. Its use is
controlled by a capacity licence based on the number of TRXs. With one
TRX licence, you can have eight additional AMR HR channels. For more
information on licensing, see Licensing in BSCunder Install and upgrade/
Software in the PDF view.
Benefits
With Soft Channel Capacity, you can fully utilise the AMR HR application
software in the existing networks without deploying more BSCs.
Related topics in Overview of Soft Channel Capacity
. Requirements for Soft Channel Capacity
. Technical description of Soft Channel Capacity
.
User interface of Soft Channel Capacity
Other related topics
. Functional descriptions
. Radio network performance
. Radio Channel Allocation
. Traffic Reason Handover in BSC
. RF Power Control and Handover Algorithm
. Operability
.
Radio Network Recovery and State Management
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Overview of Soft Channel Capacity
http://localhost/var/www/apps/conversion/releases/20121120192253/tmp/scratch_4/NED?action=retrieve&library=bsc_tcsm_rel_s13_v1_2008_03_25&identifier=dn9814129&edition=3&language=en&coverage=global&encoding=pdf_online_a4&component=data&item=datahttp://localhost/var/www/apps/conversion/releases/20121120192253/tmp/scratch_4/NED?action=retrieve&library=bsc_tcsm_rel_s13_v1_2008_03_25&identifier=dn9814008&edition=2&language=en&coverage=global&encoding=pdf_online_a4&component=data&item=datahttp://localhost/var/www/apps/conversion/releases/20121120192253/tmp/scratch_4/NED?action=retrieve&library=bsc_tcsm_rel_s13_v1_2008_03_25&identifier=dn9814008&edition=2&language=en&coverage=global&encoding=pdf_online_a4&component=data&item=datahttp://localhost/var/www/apps/conversion/releases/20121120192253/tmp/scratch_4/NED?action=retrieve&library=bsc_tcsm_rel_s13_v1_2008_03_25&identifier=dn9814129&edition=3&language=en&coverage=global&encoding=pdf_online_a4&component=data&item=data -
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. 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
. GPRS/EDGE
. HSCSD and 14.4 kbit/s Data Services in BSC
. Value added services
. Wireless Priority Service
. Trunk reservation
. Product descriptions
. Product Description of Nokia BSC2i and BSCi High Capacity
Base Station Controller
. Product Description of Nokia BSC3i High Capacity Base
Station Controller
. Operate and maintain
. Nokia BSS Transmission Configuration
.
Install and upgrade. Software
. Licensing in BSC
. Reference
. Alarms
. Base Station Alarms (70007999)
. Counters/performance Indicators
. Circuit-switched measurements
. 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
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2 Requirements for Soft Channel CapacitySoftware 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 SoftChannel Capacity. You should not create more radio channels per TRX
than recommended in Nokia BSS Transmission Configuration under
Operate and maintain in the PDF view.
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3 Technical description of Soft ChannelCapacity
3.1 BSC radio network configuration with Soft ChannelCapacity
With Soft Channel Capacity, the maximum number of traffic channels
(TCH) per BSC signalling unit (BCSU) is doubled. The new numbers are
shown in table Maximum number of TCHs 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 timeslots to
dual rate (DR) support. Increasing the limits means that more TCHs can be
created in the radio network than are allowed to be activated
simultaneously. This is extra TCH capacity.
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3.2 Radio channel allocation with Soft Channel
Capacity
Maximum number of simultaneously active traffic channels perBCSU
The limits of the number of simultaneously active traffic channels (TCH)
per BCSU are shown in table Maximum number of simultaneously active
TCHs per BCSU.
Table 2. Maximum number of simultaneously active TCHs per BCSU
BSC type Number of simultaneously active
TCHs in the BCSU
BSC2i 512
BSC3i 660 880
BSC3i 1000/2000 1600
The number of active TCHs per BCSU is maintained in the BSC. The radio
resource management part of the BSC controls the usage of TCHs. If the
number of active TCHs in the BCSU reaches the limit value, it is not
possible to activate a new TCH in the TRXs controlled by that BCSU untilan active TCH has been released. Figure Example of active traffic channel
limits per BCSUgives an example of activeTCH limits per BCSU in BSC2i.
Figure 1. Example of active traffic channel limits per BCSU
BSC2i
BCSU 1: 600 TCHs created512 TCHs active
BCSU 2: 500 TCHs created500 TCHs active
TRX 1
BTS 1
TRX 2
TRX 3
BCSU 1
BCSU 3
BCSU 2
BCSU 3: 600 TCHs created450 TCHs active
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In the example, it is not possible to allocate a TCH in TRX 1 or in TRX 2. In
BCSU 1 the maximum number of TCHs is already activated. In BCSU 2 allthe TCHs are already activated. It is possible to allocate a TCH only in
TRX 3. If TRX 3 happens to be in use already, it is not possible to allocate
a TCH in the cell even if there were free channels in TRX 1.
The principles of calculating the number of active TCHs are described in
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 TCHsFull rate single slot CS call 1
Half rate single slot CS call 1
2-timeslot multislot CS data call 2
3-timeslot multislot CS data call 3
4-timeslot multislot CS data call 4
GPRS/EDGE territory timeslot 1
Dynamic SDCCH timeslot 1
CS connection of a DTM call 1
Cell capacity assurance
The cell capacity assurance algorithm ensures that a sufficient number of
TCHs can be activated in each cell of the network at any time even if extra
TCH capacity has been created in the radio network. This algorithm
assures that the minimum number of the calls that can be set up in each
cell of the network at any time is equal to the number of the created TCH
timeslots in the cells, that is, the cell capacity assurance level is 100%.
Figure Example of cell capacity assurance algorithm describes the cellcapacity assurance algorithm.
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Figure 2. Example of cell capacity assurance algorithm
The assured TCH capacity of BTS 1, 2, and 3 together is 18 TCHs. Only 6
TCHs are currently active in those BTSs. The maximum number of
simultaneously active TCHs in BCSU 1 is 512. Of those, 500 are already
active. Therefore, it is not possible to activate a TCH in TRX 4 of BTS 4.
The free resources of BCSU 1 must be saved for BTSs 1, 2, and 3 to
assure sufficient number of calls in each of the BTSs. In BTS 4, it is
possible to allocate a TCH only in TRX 5 at the moment.
3.3 Interworking
The extra TCH capacity created in the radio network has effects on various
operating and application software in the BSC. The effects are describedin table Soft Channel Capacity interworking.
BTS 1: assured capacity6 TCHs2 active TCHs
BTS 2: assured capacity6 TCHs2 active TCHs
BSC2i
BTS 1: assured capacity6 TCHs2 active TCHs
BTS 3: assured capacity6 TCHs2 active TCHs
BCSU 1: 600 TCHs created500 TCHs active
BCSU 2: 500 TCHs created490 TCHs active
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
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Table 4. Soft Channel Capacity interworking
Basic/application software Interworking
Congestion time The BSC starts the congestion time if the
number of idle channels in the BTS drops to
zero. If extra TCH capacity has been created in
the BTSs, it is possible to have the radio
channel allocation attempts rejected because of
a lack of traffic handling capacity in the BCSU
even if the congestion time is not shown in the
statistics.
Intra-BTS handovers because of
GPRS/EDGE or high-speed
circuit-switched data (HSCSD)
Intra-BTS handovers are started for the single-
slot circuit-switched (CS) calls in the BSC to
enable the GPRS/EDGE territory upgrade or the
HSCSD upgrade. The BSC starts these
handovers based on the number of idle channels
in the BTSs. If extra TCH capacity has been
created in the BTSs, it is possible to have
handover attempts started and rejected because
of a lack of traffic handling capacity in the BCSU
although there are idle channels in the BTSs.
For more information on GPRS/EDGE and
HSCSD, see GPRS/EDGE in BSC and HSCSD
and 14.4 kbit/s Data Services in BSC under
Feature descriptions/Data in the PDF view.
GPRS/EDGE margins The GPRS/EDGE territory upgrade anddowngrade decisions are based on the number
of idle timeslots in the BTS. If extra TCH
capacity has been created in the BTS, the
downgrade margin does not work optimally. The
GPRS/EDGE territory downgrade caused by the
increasing CS traffic is not started as early as
without extra TCH capacity. The effects can be
reduced by setting the BSC parameters free
TSL for CS upgrade (CSU) and free TSL
for CS downgrade (CSD) to maximum values.
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Table 4. Soft Channel Capacity interworking (cont.)
Basic/application software Interworking
Wireless Priority Service (WPS) WPS is application software in the BSC. The
radio channel allocation for the public (RCAP)
algorithm is based on the traffic load situation in
the cell. The BSC checks the cell resource
usage based on the BSC parameters WPS
priority capacity (WPIC) and WPS
preference capacity (WPEC). If extra TCH
capacity has been created in the cell, it is
possible that the round robin allocation is
invoked too late and no resources are available
for an incoming public user in the cell. Thissituation can be avoided by reducing the values
of the WPIC and WPEC parameters and
increasing the value of the BSC parameter
public served count (PSC). The values of
the WPIC and WPEC parameters should be
reduced in relation to the amount of extra TCH
capacity in the network. If the number of TCHs
has been doubled in the network, the values of
the parameters should be halved.
For more information, see Wireless Priority
Service under Feature descriptions/Value added
services and BSS Radio Network Parameter
Dictionary under Reference/Parameters in thePDF view..
Directed Retry for a queued WPS
user
The BSC checks the cell resource usage of the
target cells based on the BSC parameters WPS
priority capacity (WPIC) and WPS
preference capacity (WPEC). If extra TCH
capacity has been created in the cell, it is
possible that a Directed Retry handover for a
queued WPS user is started to a cell which
actually is congested and the WPS call setup is
interrupted. This situation can be avoided by
reducing the values of the WPIC and WPEC
parameters. The values of these parameters
should be reduced in relation to the amount ofextra TCH capacity in the network. If the number
of TCHs has been doubled in the network, the
values of the parameters should be halved.
For more information, see Wireless Priority
Service under Feature descriptions/Value added
services and BSS Radio Network Parameter
Dictionary under Reference/Parameters in the
PDF view..
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Table 4. Soft Channel Capacity interworking (cont.)
Basic/application software Interworking
BSC-initiated Traffic Reason
Handover (BSC-initiated TRHO)
BSC-initiated TRHO is a part of Advanced
Multilayer Handling application software in the
BSC. The BSC checks the traffic load situation
in the serving cell based on the parameter AMH
upper load threshold (AUT). If the traffic
load of the serving cell exceeds the AUT
parameter, the BSC tries to hand over calls to
other, less loaded cells. If extra TCH capacity
has been created in the serving cell, the
handovers are started later than without extra
capacity. It is possible that the cell is alreadycongested but the handovers are not started
because of the extra TCH capacity. The effects
can be minimised by reducing the value of the
AUT parameter.
The load of the target cell in the BSC TRHO
attempt is checked based on the value of the
parameter AMH max load of target cell
(AML). If the traffic load in the target cell is
below the value of the AML parameter, the call is
handed over to the target cell. The aim is to
avoid making handovers from one congested cell
to another. If extra TCH capacity has been
created in the target cell, the handover can bemade to a cell which already is almost
congested. The effects can be minimised by
reducing the value of the AML parameter. The
values of the AUT and AML parameters should be
reduced in relation to the amount of extra TCH
capacity in the network. If the number of TCHs
has been doubled in the network, the values of
the parameters should be halved.
For more information, see RF Power Control and
Handover Algorithm under Functional
descriptions/Radio network performance in the
PDF view.
MSC-initiated TRHO The BSC reports the number of idle TCHs in thecells to the MSC. If extra TCH capacity has been
created in the cell, it is not necessarily possible
to allocate all the reported idle channels of a cell
simultaneously. As a consequence, the MSC
may start handovers from one congested cell to
another.
For more information, see Traffic Reason
Handover in BSC under Functional descriptions/
Radio network performance in the PDF view.
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Table 4. Soft Channel Capacity interworking (cont.)
Basic/application software Interworking
Direct Access to Desired Layer/
Band (DADL/B)
DADL/B is application software in the BSC.
When DADL/B is activated, the BSC checks the
traffic load situation in the accessed cell based
on the BTS parameter BTS load threshold
(BLT). If the traffic load of the accessed cell
exceeds the value of the BLT parameter, the
BSC tries to direct the call to another layer or
band of the network. If extra TCH capacity has
been created in the accessed cell, the calls are
not directed to another layer or band as early as
without extra TCH capacity. The effects can beminimised by reducing the value of the BLT
parameter. The value of the BLT parameter
should be reduced in relation to the amount of
extra TCH capacity in the network. If the number
of TCHs has been doubled in the cell, the value
of the parameter should be halved.
For more information, see Direct Access to
Desired Layer/Band under Feature descriptions/
Radio network performance in the PDF view.
Load distribution between the
BTSs of the segment
The load distribution between different BTSs in a
segment is controlled with the BTS parameter
BTS load in SEG (LSEG). For each call, the
BSC checks the resource usage of each BTS ofthe target segment based on the LSEG
parameter. The BSC then decides to which BTS
the call is directed. The aim is to keep the load
of each BTS within the limit that the LSEG
parameter defines. If extra TCH capacity has
been created in the segment, the calls are not
directed, for example, to a non-BCCH layer of
the segment as early as without extra TCH
capacity. The effects can be minimised by
adjusting the value of the LSEG parameter. The
value of the LSEG parameter should be reduced
in relation to the amount of extra TCH capacity
in the network. If the number of TCHs has beendoubled in the BTS, the value of the parameter
should be halved. However, if the value of the
LSEG parameter has already been set to a low
value (about 10% or lower), there is not
necessarily any need to change the value. In this
case the load distribution between layers in the
segment works well also with the extra TCH
capacity.
For more information on the load distribution
between the BTSs of the segment, see Common
BCCH Control in BSC under Feature
descriptions/Radio network performance in the
PDF view.
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Table 4. Soft Channel Capacity interworking (cont.)
Basic/application software Interworking
Dynamic SDCCH reconfiguration The last idle TCH timeslot of a cell is not
supposed to be reconfigured to the stand-alone
dedicated control channel (SDCCH). In case of
the last idle TCH timeslot the FACCH call setup
is applied. However, if extra TCH capacity has
been created in the cell, it is possible that the
dynamic SDCCH reconfiguration causes
temporary TCH congestion in the cell.
For more information on Dynamic SDCCH, see
chapter Dynamic SDCCH in Radio Channel
Allocation under Functional descriptions/Radionetwork performance in the PDF view.
GSM-WCDMA Inter-System
Handover (ISHO)
ISHO from a GSM to a WCDMA RAN cell for
speech calls is started on the basis of the traffic
load in the serving GSM cell. The load in the
serving cell is checked with the handover
parameter min traffic load for speech
call (LTSC). The handover is not started until
the load in the serving cell exceeds the
threshold. If extra TCH capacity has been
created in the serving cell, the handovers to the
WCDMA RAN cell are not started as early as
without extra TCH capacity. The effect can be
minimised by reducing the value of the LTSC
parameter. The value of the LTSC parameter
should be reduced in relation to the amount of
extra TCH capacity in the network. If the number
of TCHs has been doubled in the cell, the value
of the parameter should be halved.
For more information on ISHO, see GSM-
WCDMA Interworking under Feature
descriptions/Radio network performance in the
PDF view.
Trunk Reservation Trunk Reservation does not work optimally if
extra TCH capacity has been created in the
BSC. The trunk reservation algorithm takes intoaccount all the created radio interface TCHs. If
extra TCH capacity has been created in the
BSC, the trunk reservation algorithm cannot
ensure that there is always capacity available for
the priority user in a cell.
For more information, see Trunk Reservation
under Feature descriptions/Value added services
in the PDF view.
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Table 4. Soft Channel Capacity interworking (cont.)
Basic/application software Interworking
Radio network recovery In a recovery situation, either all timeslots of the
TRX are reconfigurated or the user defined traffic
timeslots of the TRX are returned, depending on
the BTS configuration. This means that the
number of TCHs per BCSU can change.
For more information, see Radio Network
Recovery and State Management under
Functional descriptions/Operability in the PDF
view.
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4 User interface of Soft Channel CapacityMML commands
. Transceiver Handling (command group ER)
With the ERM command, you can modify the full rate (FR) radio
timeslots to dual rate (DR) support.
. Base Station Controller Parameter Handling (command group EE)
With the EEI command, you can check the number of real TCHs
under BCSUs.
. 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.
For more information on the command groups and MML commands, see
MML commands under Reference/Commands in the PDF view.
Error codes
. SOFT CHANNEL CAPACITY LICENCE EXCEEDED
With this error code, the BSC informs you that the maximum amount
of soft channels in the BSC is exceeded.. AMOUNT OF SOFT CHANNELS IN BSC EXCEEDS AMR HR LICENCE
CAPACITY
With this error code, the BSC informs you that there are more soft
channels configured in the BSC than the 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 not in use in the BSC.
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For more information, see Licensing in BSC under Install and upgrade/
Software and General Error Messages of System under Reference/Printouts/error codes in the PDF view.
Alarms
7746 CH CONGESTION IN CELL ABOVE DEFINED THRESHOLD
Soft Channel Capacity introduces a field to this alarm.
For a more detailed description of the alarm, see Base Station Alarms
(70007999) under Reference/Alarms in the PDF view.
Counters
The following counters to Soft Channel Capacity Measurement are
introduced:
. 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 extra TCHs have been created
in a cell, it is possible that a radio channel allocation attempt is rejected
because of the lack of BCSU capacity even if there are free radio TCHs in
the cell. In this case, the existing Traffic Measurement and Resource
Availability Measurement counters are updated as if the radio channel
allocation attempt was rejected because of a lack of radio resources. The
following counters are an exception:
. 002026 TOTAL CHANNEL BUSY TIME
. 002044 FULL RATE radio CONGESTION TIME
. 002045 HALF RATE radio CONGESTION TIME
These counters do not show congestion time unless all the radio TCHs of
the cell have been occupied.
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For more information, see the following measurements under Reference/
Counters/performance indicators/Circuit-switched measurements in thePDF view:
. 1 Traffic Measurement
. 2 Resource Availability Measurement
. 109 Soft Channel Capacity Measurement
User interface of Soft Channel Capacity