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BSSPAR1: Chapter 4
Radio Resource Management
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Module Objectives
Give an overview about the signalling to establish and release a call Discuss the standard and maximum acceptable interference level
algorithm used for TCH allocation
Explain prioritised TCH allocation
Give an overview about the parameter settings applied to queuing
Explain how the queue is entered and left, and how these processes
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Discuss the algorithms to verify call drop and re-establish a call
Explain TCH allocation and queuing for Wireless Priority of Service(WPS)
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Channel request (RACH)MS NETWORK
Immediate assignmentImmediate assignment (AGCH)
Service request (SDCCH)
Service request
Authentication request (SDCCH)
Authentication response (SDCCH) Authentication
Ciphering mode command (SDCCH)
Signaling (Mobile Originating Call)
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Setup (SDCCH)
Call initiationCall proceeding (SDCCH)
Assignment command (SDCCH)
Assignment complete (FACCH) Assignment of traffic channel
Alert (FACCH)
Call confirmation
Connect (FACCH)
Connect acknowledged (FACCH) Call accepted
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Page request (PCH)MS NETWORK
Immediate assignmentChannel request (RACH)
Page response (SDCCH)
Service request
Authentication request (SDCCH)
Authentication response (SDCCH) Authentication
Ciphering mode command (SDCCH)
Immediate assignment (AGCH)
Signaling (Mobile Terminating Call)
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Ciphering mode complete (SDCCH) Ciphering mode setting
Setup (SDCCH)
Call initiationCall confirmation (SDCCH)
Assignment command (SDCCH)
Assignment complete (FACCH) Assignment of traffic channel
Alert (FACCH)
Call confirmation
Connect (FACCH)
Connect acknowledged (FACCH) Call accepted
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DisconnectMS NETWORK
Call clearingRelease
Channel release
Release complete
Network initiated
Signaling (Call Release)
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DisconnectMS NETWORK
Call clearingRelease
Channel release
Release
Release complete
MS initiated
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MS capabilities
Channel rate : full, half, dual, multi rateSpeech codecs : normal FR, normal HR, EFR, AMR FR, AMR HR, Double HR(OSC)
MSC demands
A interface circuit allocated for call
Standard TCH Allocation (General Criteria)
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BTS demands
Speech codec capabilitiesTCH configurationCurrent resources
Homogeneous use of TRXs and radio time slotsLarge free groups of radio time slots for high loaded HSCSD BTS
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Measurement of uplink receive level on idle channels = uplink interference
Averaging over interferenceAveragingProcessAverPeriod (AP)(6) = 1..32 SACCHperiods
Classification into interference bands based on interferenceAveragingProcess(BO1..BO4) = -110..-47 dBm
Standard TCH Allocation(Interference Bands)
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BSC tries to allocate TCH from best interference band (can be requested by MSC)If not available, BSC tries to take TCH from next band
0 71 2 3 4 5 6
rxLevUL = -75 dBm
BO5 47 (fixed)
BO0 110 (fixed)
BO4 -90
BO3 -95
BO1 -105BO2 -100
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Measurement Coding
RxLev Coding
-110dBm 0-109 1
-108 2
BER(%) Coding
< 0.2 00.2-0.4 10.4-0.8 2
I Interf.(dBm) Band
-110 to -105 0
-104 to -100 1
LEVEL QUALITY INTERFERENCE
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. .
. .- 49 61- 48 62
- 47dBm 63
0.8-1.6 31.6-3.2 43.2-6.4 5
6.4-12.8 6> 12.8 7
-99 to -95 2-94 to -90 3-89 to -47 4
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Standard algorithm
Does not avoid allocation of strongly interfered channels-> dropped calls-> channels allocated again with same consequence
Maximum interference level algorithm
BSC tries to allocate TCH from interference band into which MAX INTF LEV falls
Maximum Interference Level(Call Set Up + Intra Cell Handover)
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MAX_INTF_LEV = RXLEV_UL - cNThreshold + (msTxPwrMax - MS_TXPWR)
_ _-> TCH usually from better band than according the standard algorithm
Parameters
RXLEV_UL current uplink receive levelcNThreshold (CNT)0..63 dB desired C/N ratioMS_TXPWR current MS output powermsTxPwrMax maximum allowed MS output power in serving cell
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MAX_INTF_LEV = RXLEV_DL - rxLevBalance - cNThreshold
RXLEV_DL is current downlink receive level
Maximum Interference Level(Inter Cell Handover)
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BSC tries to allocate TCH in target cell from interference band, into which MAX_INTF_LEV falls
MOClass
AbbreviatedName
Range And Step Description Defaultvalue
BSC - MMLName
BSC rxLevBalance 0...20 dB, step 1
dB
Balance between the DL signal level and
the UL signal level within the BSCcoverage area. DL is considered RXBALdB stronger than UL.
5 dB RXBAL
BTS cnThreshold 0...63, step 1 The minimum acceptable C/N(carrier/noise) ratio when selecting a timeslot to be allocated for a call or handover.
0 CNT
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Priority for TCH from BCCH TRX
BCCH is transmitted permanently -> no additional interference in networkPlanned to be least interfered channels
Prioritized TCH Allocation
Whole band , 50 channels 1 ch=200kHz
BCCH, 30 channels TCH, 20 channels
All 50 channels for BCCH and TCH
Case1
Case2
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Priority for TCH from other TRX
BCCH TRX does not hop in case of RF hopping -> hopping gain only for other TRX
Parameter
trxPriorityInTCHAlloc (TRP) 0 = no priority1 = priority for BCCH TRX2 = priority for other TRX3 = priority for BCCH TRX for non-AMR users,
priority for other TRX for AMR users
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Priorities
No TCH available for call set up / handover -> request put into queueDifferent kinds of requests can have different priorities
queuePriorityUsed (QPU) Y/N enables use of priorities
queueingPriorityCall (QPC)(10) 1..14 priority for call set up requestqueuePriorityNonUrgentHo (QPN)(9) 1..14 priority for non urgent handover (power budget,
umbrella, slow moving MS, traffic reason)
Queuing (Parameters)
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request
queueingPriorityHandover (QPH)(9) 1..14 priority for urgent handover (all other) request
Queue length and time
maxQueueLength (MQL)(50) 0..100% percentage of number of TCHs handled by BTStimeLimitCall (TLC)(10) 0..15 s time a call set up request is kept in the queue
0 = queuing is disabledtimeLimitHandover (TLH)(5) 0..10 s time a handover request is kept in the queue
0 = queuing is disabled
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Conditions
Timers set to values > 0Use of priorities enabledQueue not full with requests of equal or higher priority than the current one
Queuing of call set up requests
Queuing (Entering the Queue)
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Reservation of SDCCH resources-> SDCCH easily overbooked-> blocking of services like SMS or location update
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With TCH allocation
Release of busy TCH Check of queue from top to bottom for best matching request If TCH allocation possible, request removed from queue
Without TCH allocation
Queuing (Leaving the Queue)
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Queuing timer expiresRequest of higher priority enters full queue
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Directed Retry Timer maxTimeLimitDirectedRetry expires
call cleared, even if still in queue
Queuing timer expires
target cell evaluation continues, if directed retry timer is still running
Queuing (Together with Directed Retry)
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BTS does not receive measurement report onSACCH for running call for the first time
Counter initialised with value of radioLinkTimeout(4,8,..64 SACCH periods)(20)
SACCH not received again SACCH received again
Dropped Call ControlRadio Link Timeout
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Counter decremented by 1 Counter incremented by 2(but not beyond initial value)
Counter has value 0
Call release due to radio linktime out
Example: short tunnel
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RLT is based on SACCH deletion but SACCH is though not using adynamic codec like voice in AMR, which means:
Using the EFR RLT value an AMR customer can have the call droppedbecause RLT = 0 when still the FER is good
RLT is not anymore reliable with the same value in AMR as in EFR
Due to the fact that the FER performance is different when comparing AMR
Dropped Call ControlRadio Link Timeout
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,for AMR
The Radio Link Timeout parameters for AMR are ARLT and AHRLT. Theprinciple of these are the same as in the RLT but they are used only for theAMR capable mobile stations. ARLT & AHRLT are not supported in TalkFamily base stations.
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Radio link timeout occurscallReestablishmentAllowed (RE) set to Y
Receive level of BCCH measured for serving and adjacent cellAveraged over 5 s
Strongest cell considered Example: long tunnel
Dropped Call ControlCall Reestablishment
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BCCH decodedC1 cell selection criterion fulfilledCell not barred
Cell belongs to selected PLMN
Attempt to re-establish call
Successful within 20s *
call re-established
Not successful within 20s * call released
* MAX WAIT TIME OF RE-ESTAB REQ is a modifiable timer in MSC