radio resource_management_v1.1_chema

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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)


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)


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)


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)


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)


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)


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


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)


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


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)


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


•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

Soft blocking C/N FR: 0…63dB/ def: 12dB

Soft Blocking C/N HR: 0…63dB/ def: 14dB

Soft blocking C/N AMR FR: 0…63dB/ def: 7dB

Soft blocking C/N AMR HR: 0…63dB/ def: 12dB

Soft blocking C/N 14.4 : 0…63dB/ def: 14dB

RX level based TCH Allocation (m)

Note: all the soft blocking C/N parameters belong to BSC


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)


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)


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)


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)


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)


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


• 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


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


• 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


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


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


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


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


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


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

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