This document provides an overview of radio resource management for cellular networks. It discusses topics like call signaling, traffic channel allocation algorithms, interference level measurements, prioritized allocation, queuing parameters and processes for entering and leaving the queue. The document is copyrighted material from Nokia Siemens Networks and cannot be copied or shared without their permission.

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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 interact with handover and especially directed retry
•Discuss the algorithms to verify call drop and re-establish a call
•Explain TCH allocation and queuing for Wireless Priority of Service (WPS)

4. 4 © Nokia Siemens Networks
Channel request (RACH)
MS
NETWORK
Immediate assignment
Immediate assignment (AGCH)
Service request (SDCCH)
Service request
Authentication request (SDCCH)
Authentication response (SDCCH)
Authentication
Ciphering mode command (SDCCH)
Ciphering mode complete (SDCCH)
Ciphering mode setting
Setup (SDCCH)
Call initiation
Call proceeding (SDCCH)
Assignment command (SDCCH)
Assignment complete (FACCH)
Assignment of traffic channel
Alert (FACCH)
Call confirmation
Connect (FACCH)
Connect acknowledged (FACCH)
Call accepted
Signalling (Mobile Originating Call)

5. 5 © Nokia Siemens Networks
Page request (PCH)
MS
NETWORK
Immediate assignment
Channel request (RACH)
Page response (SDCCH)
Service request
Authentication request (SDCCH)
Authentication response (SDCCH)
Authentication
Ciphering mode command (SDCCH)
Ciphering mode complete (SDCCH)
Ciphering mode setting
Setup (SDCCH)
Call initiation
Call confirmation (SDCCH)
Assignment command (SDCCH)
Assignment complete (FACCH)
Assignment of traffic channel
Alert (FACCH)
Call confirmation
Connect (FACCH)
Connect acknowledged (FACCH)
Call accepted
Immediate assignment (AGCH)
Signalling (Mobile Terminating Call)

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Disconnect
MS
NETWORK
Call clearing
Release
Channel release
Release
Release complete
Disconnect
MS
NETWORK
Call clearing
Release
Channel release
Release
Release complete
Network initiated
MS initiated
Signalling (Call Release)

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MS capabilities
Channel rate : full, half, dual, multi rate
Speech codecs : normal FR, normal HR, EFR, AMR FR, AMR HR
MSC demands
A interface circuit allocated for call
BTS demands
Speech codec capabilities
TCH configuration
Current resources
Homogeneous use of TRXs and radio time slots
Large free groups of radio time slots for high loaded HSCSD BTS
Standard TCH Allocation (General Criteria)

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Measurement of uplink receive level on idle channels = uplink interference
Averaging over interferenceAveragingProcessAverPeriod (AP) (SEG) = 1..32 SACCH periods, step 1, Def=6
Classification into interference bands based on interferenceAveragingProcess (BO1..BO4) (BTS) = -110..-47 dBm
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
7
1
2
3
4
5
6
rxLevUL = -75 dBm
BO5 –47 (fixed)
BO0 –110 (fixed)
BO4 -90
BO3 -95
BO1 -105
BO2 -100
Standard TCH Allocation (Interference Bands) (m)

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Measurement Coding
RxLev Coding
-110dBm 0
-109 1
-108 2
. .
. .
- 49 61
- 48 62
- 47dBm 63
BER(%) Coding
< 0.2 0
0.2-0.4 1
0.4-0.8 2
0.8-1.6 3
1.6-3.2 4
3.2-6.4 5
6.4-12.8 6
> 12.8 7
I Interf.
(dBm) Band
-110 to -105 0
-104 to -100 1
-99 to -95 2
-94 to -90 3
-89 to -47 4
LEVEL
QUALITY
INTERFERENCE

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MAX_INTF_LEV = RXLEV_UL - cNThreshold + (msTxPwrMax - MS_TXPWR)
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
-> TCH usually from better band than according the standard algorithm
Parameters
RXLEV_UL current uplink receive level
cNThreshold (CNT) (BTS) 0..63 dB desired C/N ratio
MS_TXPWR current MS output power
msTxPwrMax (PMAX1 & PMAX2) (SEG) maximum allowed MS output power in serving cell
Maximum Interference Level (Call Set Up + Intra Cell Handover) (m)

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MAX_INTF_LEV = RXLEV_DL - rxLevBalance - cNThreshold
• RXLEV_UL is current uplink receive level
• BSC tries to allocate TCH in target cell from interference band, into which MAX_INTF_LEV falls
Maximum Interference Level (Inter Cell Handover)
MO Class
Abbreviated Name
Range And Step
Description
Default value
BSC - MML Name
BSC
rxLevBalance
0...20 dB, step 1 dB
Balance between the DL signal level and the UL signal level within the BSC coverage area. DL is considered RXBAL dB stronger than UL.
5 dB
RXBAL
BTS
cnThreshold
0...63, step 1
The minimum acceptable C/N (carrier/noise) ratio when selecting a time slot to be allocated for a call or handover.
0
CNT

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Priority for TCH from BCCH TRX
BCCH transmitted permanently -> no additional interference in network
Planned to be least interfered channels
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)(SEG) 0 = no priority
1 = priority for BCCH TRX
2 = priority for other TRX
3 = priority for BCCH TRX for non-AMR users,
priority for other TRX for AMR users
Prioritized TCH Allocation (m)

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Enables to differentiate Rx level requirement for:
•MS camping to the network /RxLev Access Min
•MS accessing to TCH /RX level based TCH access RX level based TCH allocation method
•RX Level measured by the MS is used to determine whether the BTS is acceptable for TCH allocation
•TCH allocation for emergency calls is not restricted due to low RX level Provides better drop call meters and better performance of MSs
•MSs having too low Rx levels are not allowed to camp the network By separating camping and TCH access thresholds the operator will be able to provide the maximum camping footprint
RX level based TCH Allocation

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•Allows to define minimum C/N ratios separately for each call type (AMR FR, AMR HR,
EFR/FR, HR and 14.4 data)
•Parameter values ‘RX level based TCH access’ (RXTA) (BSC) def=0
0: RX level based TCH access is not used (C/N definitions not in use)
1: RX level based TCH access is used in call setup
2: RX level based TCH access is used in call setup and in handovers
Downlink RX Level
-> TCH Access
Soft blocking C/N FR: 0…63dB/ def: 12dB
Soft Blocking C/N HR:
Soft blocking C/N AMR FR:
Soft blocking C/N AMR HR:
Soft blocking C/N
0…63dB/ def: 14dB
0…63dB/ def: 7dB
0…63dB/ def: 12dB
14.4 : 0…63dB/ def: 14dB
RX level based TCH Allocation (m)
Note: all the soft blocking C/N parameters
belong to BSC

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Priorities
No TCH available for call set up / handover -> request put into queue
Different kinds of requests can have different priorities
queuePriorityUsed (QPU) (SEG) Y/N enables use of priorities
queueingPriorityCall (QPC) (SEG) 1..14 priority for call set up request
queuePriorityNonUrgentHo (QPN) (SEG) 1..14 priority for non urgent handover (power budget,umbrella, slow moving MS, traffic reason)
request
queueingPriorityHandover (QPH) (SEG) 1..14 priority for urgent handover (all other) request
Queue length and time
maxQueueLength (MQL) (SEG) 0..100(def:50) percentage of # of TCHs handled by BTS timeLimitCall (TLC) (SEG) 0..15 s time a call set up request is kept in the queue
0 = queuing is disabled
timeLimitHandover (TLH) (SEG) 0..10 s time a handover request is kept in the queue
0 = queuing is disabled
Queuing (Parameters) (m)

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Conditions
Timers set to values > 0
User of priorities enabled
Queue not full with requests of equal or higher priority than the current one
Queuing of call set up requests
Reservation of SDCCH resources
-> SDCCH easily overbooked
-> blocking of services like SMS or location update
Queuing (Entering the Queue)

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Handover request queued by target BTS
Handover timers hoPeriodPBGT and hoPeriodUmbrella stopped Measurement processing and averaging continues as usual
Intra BSC handover
Inter BSC handover
Queuing possibility checked for all possible target cells Order according conventional ranking
Target BTS given by MSC by handover request message
Queuing (Handover)

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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 timer expires
Request of higher priority enters full queue
Queuing (Leaving the Queue)

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Directed Retry Timer maxTimeLimit maxTimeLimitDirectedRetry (MADR) (SEG) 1 …15 sec, def= 5 sec 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 on SACCH for running call for the first time
Counter initialised with value of radioLinkTimeout (RLT) (SEG) (4,8,..64 SACCH periods, step= 4 SACCH blocks, DEF= 20 Blocks)
SACCH not received again
Counter decremented by 1
SACCH received again
Counter incremented by 2 (but not beyond initial value)
Counter has value 0
Call release due to radio link time out
Example: short tunnel
Dropped Call Control (m) Radio Link Timeout

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•RLT is based on SACCH deletion but SACCH is though not using a dynamic codec like voice in AMR, which means:
•Using the EFR RLT value an AMR customer can have the call dropped because RLT = 0 when still the FER is good
•RLT is not anymore reliable with the same value in AMR than in EFR
•Due to the fact that the FER performance is different when comparing AMR calls to EFR calls, the Radio Link Timeout need to be defined separately for AMR
•The Radio Link Timeout parameters for AMR are ARLT and AHRLT. The principle of these is the same than in the RLT but it is used only for the AMR capable mobile stations. ARLT & AHRLT are not supported in Talk Family base stations.
Dropped Call Control Radio Link Timeout

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Radio link timeout occurs
callReestablishmentAllowed (RE) (SEG) (Y/N Def=N) set to Y
Receive level of BCCH measured for serving and adjacent cell Averaged over 5 s
Strongest cell considered
BCCH decoded C1 cell selection criterion fulfilled Cell not barred
Cell belongs to selected PLMN
Attempt to re-establish call
Successful within 20s *
 call re-established
Not successful within 20s *  call released
Example: long tunnel
Dropped Call Control (m) Call Reestablishment
* MAX WAIT TIME OF RE-ESTAB REQ is a modifiable timer in MSC

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•Wireless Priority Service is intended for National Security and Emergency Preparedness (NS/EP) leaders and key personnel(ANSI Markets)
•WPS calls are given priority access to the next available radio traffic channel in congestion situation
•Reasonable amount of radio capacity must be available also for public users
Wireless Priority Service

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Overload situation  authorized personnel still should have access to network
 access for commercial users must be denied
MS access class
Indicated by BCCH system information message
MS belongs to indicated access class  access allowed
Otherwise  access not allowed
WPS user
Has basic access class and one of access classes 12-14
Wireless Priority Service Principle

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WPS priority capacity %
• Priority to WPS users if the share of WPS users is less than defined WPS priority capacity from total cell load
• If cell is congested WPS user is put on queue
WPS preferred capacity %
• Allowed to allocate to WPS users without restrictions when share of WPS users exceeds WPS priority capacity but total cell load is less than WPS priority capacity plus WPS preferred capacity
Public Service capacity %
• Certain amount of public calls must be served before resource to WPS user can be allocated when share of WPS users exceeds WPS priority capacity and total cell load is exceeds WPS priority capacity plus WPS preferred capacity share.
• If cell is congested WPS user is put on queue
Radio interface resource
Wireless Priority Service Resource management principle

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BSC Parameter
wpsPriCapa (WPIC) 0..100% percentage of cell load, for which WPS users have higher priority
wpsPrefCapa (WPEC) 0..100% percentage of remaining cell load, which can be occupied without restricting access for WPS users
PublicServCount (PSC) 0..10 number of public user that must be served prior to serving the next WPS call in the round robin allocation
Example
8 TCHs
wpsPriCapa = 50% (8 * 0.5) = 4 TCHs
wpsPrefCapa = 75% (8 – 4) * 0.75 = 3 TCHs
 round robin allocation is invoked when at least four WPS users occupy the cell and a total of seven or more traffic channels (TCH) are occupied
Wireless Priority Service (m) Cell Load Thresholds

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Cell load = occupied resources / working resources
Rules to estimate number of occupied and working resources
Channel Number of Number of
occupied resources working resources
Free FR timeslot 0 1
Reserved FR timeslot 1 1
Free DR timeslot 0 3
Half reserved DR timeslot 2 3
Fully reserved DR timeslot 3 3
Free HR timeslot 0 2
Half reserved HR timeslot 1 2
Fully reserved HR timeslot 2 2
Default (E)GRPS timeslot taken into account for load calculation
Dedicated (E)GPRS timeslot not taken into account for load calculation
Wireless Priority Service Cell Load Calculation

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At least wpsPriCapa capacity occupied by WPS users AND at least wpsPrefCapa further capacity occupied by any users
Radio capacity assurance for public algorithm
Serve publicServCount consecutive users
Serve WPS user
Repeat steps until cell
load falls below one of
the thresholds
Wireless Priority Service Round Robin Algorithm

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One queue for WPS users and one for all other ones
BTS Parameters
Same priority parameters
msPriorityUsedInQueueing (MPU) Y/N must be set to Y to replace WPS calls of low MS priority level with such ones of high priority level in a full queue
But individual timers for WPS queue
timeLimitWPS (TLW) 0..30 s analogue to timeLimitCall
timeLimitWPSHO (TLWH) 0..30 s analogue to timeLimitHandover
Queuing and directed retry
Queuing continues, if timer maxTimeLimitDirectedRetry expires earlier than queuing timer
Queuing instead of directed retry, if load of target cell exceeds upper threshold wpsPrefCapa
Inter BSC directed retry not possible for WPS user
Wireless Priority Service (m) Queuing