5.Radio Resource Mgn

RADIO RESOURCE MANAGEMENT BSSPAR S9

RADIO RESOURCE MANAGEMENT Contents 1. Traffic Channel Allocation 2. Priority in TCH T CH Allocation Allocation

3. FACCH call set up 4. Preferred BCCH TRX 5. Frequency Hopping BB, RF, Freeform RF Hopping

Flexible MAIO Management 6. DR and IDR 7. Queuing 8. Call Drop Control 9. Dynamic SDCCH

RADIO RESOURCE MANAGEMENT Traffic Channel Allocation • Allocation

starts after the immediate assignment.

Radio resources to be allocated : channel  ) • SDCCH (for initial signalling or for changing the signalling channel ) • TCH (initial TCH or for changing TCH ) • Single Slot • TCH/F • TCH/H •

Multislot (HSCSD) • TCH/F

RADIO RESOURCE MANAGEMENT Traffic Channel Allocation The request includes the type and other requirements ( or recommendations) for the requested resource: tells what kind of resource it needs. In case of TCH: The channel rate •TCH/F •TCH/H The speech codecs •Normal Full rate •Normal Half rate •Enhanced Full rate We can configure three types of RTSL in a TRX: • permanent FR • permanent HR • dual rate

RADIO RESOURCE MANAGEMENT Idle Channel Interference •

The BTS measures and reports on the uplink interference of the radio channels which have been idle during the whole measurement period.

• Idle TCH’s are classified into five interference classes •

RR Management algorithm assigns a channel from the lowest possible interference class Parameters

Value

interference AveragingProcess

1 ... 32 (SACCH Period)

boundary 1-4

-110 ... -47 (dBm) (boundary0/5 fixed)

boundary5 band-47boundary4 -90boundary3 -95boundary2 -100boundary1 -105boundary0 110-

BTS

Interference Level

=> TS4 will be selected!

0

4

7

RADIO RESOURCE MANAGEMENT Calculation of maximum acceptable interference level (1/2) Call set-up and intra-cell HO (when OptimumRxLevUL = ) MAX_INTF_LEV =RXLEV_UL + ( MsTxPwrMax - MS_TXPWR ) CNThreshold When OptimumRxLevUL = MAX_INTF_LEV = MAX{MIN[RXLEV_UL + ( MsTxPwrMax - MS_TXPWR ),OptimumRXLevUL] , RXLEV_UL-(MS_TXPWR-MsTxPwrMin)} -CNThreshold Parameters CNThreshold RxLevBalance OptimumRXLevUL MsPwrOptLevel

Value 0… 63 dB 0… 20 dB -109…-47/N -110…-47/N

(0 not active)

(TRX level) (cell level)

RADIO RESOURCE MANAGEMENT Maximum Interference Level (2/2) Inter-cell Handover 

(when MsPwrOptLevel = < not used>)

MAX_INTF_LEV=RXLEV_DL - RxLevBalance - CNThreshold

Inter-cell handover 

( when MsPwrOptLevel = )

MAX_INTF_LEV (UL) =

MAX { [ MIN (AV_RXLEV_NCELL(n)

- RxLevBalance, MsPwrOptLevel(n) ] ,

( AV_RXLEV_NCELL(n)-RxLevBalance) -

(MsTxPwrMax(n) - MsTxPwrMin(n) )

}

- CNThreshold(n)

The parameter  MsPwrOptLevel(n) indicates the optimum UL RF signal level on a channel in the adjacent cell after a handover.

RADIO RESOURCE MANAGEMENT Traffic Channel Selection - Inter-cell HO example BO5 -47

rxLevUL = -75 dBm

BO4 -90 BO3 -95 BO2 -100 BO1 -105 BO0 -110

0 1 2 3 4 5 6 7

RXLEVDL = -70dBm RxLevBalance = 5 dB C/N Ratio required = 20 dB Interference Level = -70dBm - 5dB - 20dB = -95dBm => TSL between BO2 and BO3 is preferred

RADIO RESOURCE MANAGEMENT TRX Prioritisation in TCH Allocation •The

advantages of using the BCCH carrier for call set up: It would not increase interference in the network BCCH channels are planned to be the least interfered one

•The

advantage of using the TCH TRX for call set up: The hopping gain

It is possible to set priority between the TCH TRXs and BCCH TRX.

Parameters TrxPriorityInTCHAllocation

Value 0 … 2 where 0 = no preference 1 =BCCH preferred 2 =not BCCH preference BTS

RADIO RESOURCE MANAGEMENT Preferred BCCH TRX (1/2) •

Recovery system returns the BCCH automatically to its original TRX after the fault has been eliminated

•

Supports the usage of TRXs with different output power in the same cell

•

Can be activated cell by cell

•

Before restoration Forced Handover is used to avoid cutting calls

It is possible to mark more than one TRX of a cell as preferred, in which case the recovery system selects one of the marked TRXs for the BCCH. TRX-1 Faulty, Original ConfigurationAfter BCCH Recovery Preferred BCCH TRX-1

BCCH, SDCCH/8, 6xTCHs

TRX-2

8xTCHs

8xTCHs

TRX-1 Repaired, After BCCH Restoration BCCH, SDCCH/8, 6xTCHs

BCCH, SDCCH/8, 6xTCHs

8xTCHs

RADIO RESOURCE MANAGEMENT Preferred BCCH TRX, Restrictions (2/2) •

Preferred BCCH mark can not be set to floating TRX

•

BSC can automatically return BCCH to original BCCH TRX, but BSC can not return original traffic channel configuration, if BSC has changed it earlier 

•

If user locks BCCH TRX, then the BSC does not perform BCCH recovery

•

If BSC reconfigures E-RACH to the TRX having preferred BCCH mark, then that TRX is last choice for BCCH use

•

E-RACH recovery is not possible in fault cancel if BSC has to move BCCH to preferred BCCH TRX

Parameters preferredBCCHMark

Value N = Normal P = preferred

TRX

RADIO RESOURCE MANAGEMENT Directed Retry When no TCH is available in the serving cell, TCH can be allocated in an adjacent cell • Mobile Originated and Mobile Terminated Calls Traffic (TCH)

It is actually handover from SDCCH to TCH. • Imperative Handover (only equation 1) • Candidates ranked based on radio properties.

BTS B

Queueing can take place in source cell, not in target cell.

Time

minTimeLimitDR  Assignment Request maxTimeLimitDR

Call Setup (SDCCH)

BTS A

rxLevAccessMin

DR not allowed : improves the reliability of  the measurements of adjacent cells and gives th queueing processs time DR allowed

RADIO RESOURCE MANAGEMENT Directed Retry parameters

Parameters drInUse MinTimeLimitDR  MaxTimeLimitDR 

Value Yes/No 0 … 14 (sec.) 1 … 15 (sec.)

BTS

RADIO RESOURCE MANAGEMENT Directed Retry Improvement •

DR: to avoid the loss of a call in call-setup if the accessed cell is congested

•

improvement: new criterion in candidate cell selection

•

drThreshold > RXLEV_MIN

TCH SDCCH congested Parameters

Value

drMethod

0: Improvement not in use 1: Threshold evaluation method

drThreshold

-47 … -110 dBm

BTS ADJC

RADIO RESOURCE MANAGEMENT Intelligent Directed Retry

macro cell (GSM cell)

• Based

on Directed Retry : Target Cell selection depends upon IDR micro cells congestion • Classmark of the MS or MS Priority (MCN cells) •  Adjacent Cell Type MCN subscriber  • Subscribers Classified in GSM or MCN • Based on Classmark ( bitmap in BSC associates classmarks to GSM / MCN ) • No TCH Available on Accessed Cell • GSM or MCN subscriber ? • Based on MS Priority ( bitmap in BSC associates MS Priorities to GSM / MCN ) • MCN => IDR in Use in the Cell ? • Criterion defined in the BSC • Yes => Directed Retry Only to MCN Cells • DR and IDR enabled / disabled independently • No => Reject Call on a per cell basis. • GSM => DR in Use in the Cell ? •Yes

=> Directed Retry (any Cell) • No => Reject Call

Parameters IdrUsed CellType adjCellType

Value Yes/No GSM / MCN BTS GSM / MCN ADJC

macro cell (GSM cell) DR congestion GSM subscriber 

micro cells (MCN cells)

RADIO RESOURCE MANAGEMENT Frequency Hopping

Frequency hopping is changing the carrier  frequency during the connection.

•

•

The Frequency Hopping (FH) in GSM is slow FH which means that the frequency changes per burst bases ,it does not change during the transmission of the burst. The frequency remains the same during the burst (0. 577 ms).

• All

dedicated channel types can hop (TCH/SDCCH/FACCH/SACCH)

RADIO RESOURCE MANAGEMENT Frequency Hopping Two main benefits of using FH •

Frequency Diversity (Rayleigh Fading)

•

Interference Diversity (Interference averaged over multiple users)

E [V/m]

f 2 f 2

f 1

f 1 D [m]

RADIO RESOURCE MANAGEMENT BB Hopping B= BCCH TSL. It does not hop.

TSL 1….7 of all TRXs hop over  (f1,f2,f3,f4)

BB hopping on 4 TRXs. Also the BCCH TRX is hopping except on RTSL-0. The call is hopping over TRX (TRX keeps the same frequency as planned)

RADIO RESOURCE MANAGEMENT RF Hopping B= BCCH TSL. TRX does not hop.

Non BCCH TRXs are hopping over  the MA-list (f1,f2,f3).

RF hopping in 2-TRX cell. The BCCH TRX cannot hop because the BCCH frequency must be continuously transmitted in a cell. TRX will physically change frequency along a specified MAL.

RADIO RESOURCE MANAGEMENT Frequency Hopping Parameter summary General Parameters btsIsHopping

BB (BaseBand Hopping) RF (Radio Frequency Hopping) N (No Hopping) BTS

Baseband Hopping hoppingSequenceNumber1 (TS 0) 0 ... 63 (0 = cyclic, 1 ... 63 = pseudorandom) hoppingSequenceNumber2 (TS 1 ... 7) 0 ... 63 (0 = cyclic, 1 ... 63 = pseudorandom)

BTS

TRX 1

CA MA MAIO HSN

= Cell Allocation = Mobile Allocation = Mobile Allocation Index Off  = Hopping Sequence Number 

0

2

B

1

7 TS f1

TRX 2

f2

TRX 3

f3

TRX 4

f4

RADIO RESOURCE MANAGEMENT Frequency Hopping Parameter summary RF ( Synthesized Hopping) (from 3rd generation BTS onward) mobileAllocationList 1 ... 124 (GSM) Note! Max. 63 Frequencies mobileAllocationId 1 … 128 BSC 0 1 2

7 TS f1

TRX 1 B

usedMobileAllocation 1 … 128 hoppingSequenceNumber1 0 … 63 (0 = cyclic, 1 ... 63 = pseudorandom) BTS

TRXMAL 2 TRX 3 TRX 4

MAL

MAL

MAL

MAL(f3,f4..fn)

RADIO RESOURCE MANAGEMENT RF Hopping (Site based MAIO allocation) MAIO HSN offset

   )    1    1  r   -   t   o    S  c    T  e   s    B    (

   )    2    2  r   -   t   o    S  c    T  e   s    (    B

   )    3    3  r   -   t   o    S  c    T  e   s    (    B

0

3

6

3

MAIO

TRX-1

BCCH -

TRX-2

TCH

0

TRX-3

TCH

1

TRX-4

TCH

2

TRX-5

BCCH

-

TRX-6

TCH

3

TRX-7

TCH

4

TRX-8

TCH

5

TRX-9

BCCH

-

TRX-10

TCH

6

TRX-11

TCH

7

TRX-12

TCH

8

3

3

f1

f2

f3

f4 f5 f6 f7 f8 f9 f10 f11 f12

RADIO RESOURCE MANAGEMENT Flexible MAIO Management Allows More Flexible RF Hopping

• enables Frequency Sharing i.e. sharing an MA list between the sectors at same site

• longer MA lists possible • minimised interference New MAIO Step Parameter in BSS7

• When used together with MAIO offset, no successive MAIOs will be allocated for  TCHs sharing the same MA list

RADIO RESOURCE MANAGEMENT Single MA/HSN per Site - with MAIO Step MA = f1, f2, f3, f4,....

HSN same for all sectors

Sector

HSN

MAIO Offset MAIO step

1 1

N

0

2

2 2

N

6

2

3 3

N

12

Operator can set the lowest MAIOs for the cells

2

TRX

MAIO, same for all RTSLs within the TRX

TRX-1

BCCH, not hopping

TRX-2

0

TRX-3

2

TRX-4

4

TRX-5

BCCH, not hopping

TRX-6

6

TRX-7

8

TRX-8

10

TRX-9

BCCH, not hopping

TRX-10

12

TRX-11

14

TRX-12

16

Operator can also set the MAIO step size

MA list can include adjacent frequencies

Band allocation: BCCH

Hopping Freq's

Nor co-channels neither adj. channels used simultaneouly if number of  frequencies > 2*number of TRXs

RADIO RESOURCE MANAGEMENT RF-FH with reuse '1/1'using fractional loading MAIO Offset

Hopping frequencies

MAIO Offset + Step Band allocation:

Band allocation:

BCCH

BCCH

Hopping Freq's

MA list

MA list

MA list and BCCH need planning

No need for MA list planning

MA list possibly shorter -> reduced gain

BCCH frequencies planned as usual

RADIO RESOURCE MANAGEMENT Flexible MAIO Management will bring the following benefits: • One MA list per site •

One MA list can contain a continuous band

•

No risk of co-channel nor adjacent channel being used simultaneously within a site •

Single MA/HSN possible -> only BCCH frequency planning •

More tighter reuse possible e.g. RF-FH (1/1) and thus more capacity can be achieved Parameters

Value

MaioStep

1..62

UnderlayMaioStep

1..62

BTS

RADIO RESOURCE MANAGEMENT Queuing of Radio Resources Purpose •

to avoid rejecting call setup or handover attempt by waiting for the release of a suitable traffic channel

Queuing Environment •

queuing is a BTS specific procedure (controlled by the BSC)

•

each BTS has a queue of its own

•

individual queue parameters and queue management for each BTS

RADIO RESOURCE MANAGEMENT Queuing •

Queuing is BTS specific controlled by the BSC

•Only

traffic channels are queued

•

Call attempts and Handovers in the same queue

•

The maximum queue length is relative to the number of traffic channels

•

The maximum queuing time can be set individually for both queue types •

The queuing can be deactivated by setting queuing time or queue length to zero •

Different priorities according to queue type (Call/Ho) and/or MS priority

RADIO RESOURCE MANAGEMENT Queue Management: SDCCH aspect •

Queuing reserves SDCCH • SDCCH • If

occupation for call setup 7 seconds.

maximum queuing time for calls is 10 s

=> in case of queuing 50-60 % more load on SDCCH / call attempt!! • (2 • If

TRXs cell) with Combined BCCH / SDCCH

maximum queue is 50 % of TRX x 8 = 8 queuing

positions => if there are 4 call attempts in queue, SDCCHs are fully booked => no space for short messages or for location updates on SDCCH => cell is fully overloaded!!

RADIO RESOURCE MANAGEMENT Queuing Parameters Parameters maxQueueLength

Values 0 ... 100

(% of TRXs x 8) BTS

timeLimitCall timeLimitHandover

0 ... 15 (s) 0 ... 10 (s)

msPriorityUsedInQueuing queuePriorityUsed

Yes / No Yes / No

queuingPriorityCall queuingPriorityHandover queuingPriorityNonUrgentHO

1 ... 14 1 ... 14 1 …14

disabled with value 0 disabled with value 0

BTS

lower value, higher priority BTS

RADIO RESOURCE MANAGEMENT Queuing and DR Directed retry and queuing are parallel procedures.

When the queuing and DR process are both active for a call , MaxTimeLimitDR time elapses without any DR  if attempt , the queing will be terminated even if the queueing timer have not elapsed as well as DR process itself   if a TCH is released in the serving cell during the period when DR is not allowed/allowed, DR process is terminated.

RADIO RESOURCE MANAGEMENT Dropped Call Control Radio Link Timeout • A

counter is initialized at the value of  the radioLinkTimeout

Call re-establishment (GSM 05.08) •In

case of a Radio Link Failure (radioLinkTimeout) within 20 seconds. •Measurements

When SACCH is not correctly received Counter decremented by 1 •When

SACCH correctly received Counter incremented by 2

When counter reaches 0 call is released •Same

behaviour UL and DL

Parameters radioLinkTimeout callReestablishmentAllowed

averaged over 5

seconds for  serving Cell BCCH adjacent Cell BCCHs •Strongest is considered BCCH data decoded (cell selection param.) If  C1 greater than 0, Cell not barred Cell belong to selected PLMN, Call re-establishment allowed Call re-establishment attempted

Values 4 ... 64 (SACCH period) Yes/No

BTS

RADIO RESOURCE MANAGEMENT Radio Link Timeout radioLinkTimeout (default) = 20(SACCH)

Outdoor 

Indoor  Elevator 

radioLinkTimeout = 40 Tunnel (short)

5. floor 

MS MS 1. floor 

RADIO RESOURCE MANAGEMENT Call Re-establishment

Outdoor 

radioLinkTimeout (default) = 20 (SACCH) BTS B Tunnel (long) BTS A

MS

It would beUnsuccessfull Handover--> dropped call => use Call Re-Establishment

RADIO RESOURCE MANAGEMENT FACCH Call Set-Up (OPTIONAL) •

When an idle SDCCH is not available for the request ; BSC tries to allocate a TCH for signalling instead of an SDCCH.  After the signalling is finished the channel mode is modified as TCH and the call continues on the same channel. Parameters

Value 

pagingAnsOnFACCH

Y/N

restablishOnFACCH

Y/N

emerCallOnFACCH

Y/N

ordinaryCallOnFACCH

Y/N BSC

RADIO RESOURCE MANAGEMENT SDCCH Dynamic allocation (1/3) •

In case of the congestion in SDCCH, one free traffic channel can be changed dynamically to SDCCH/8

•

When SDCCH/8 is not needed anymore it is changed dynamically back to TCH

•

In IUO case, SDCCH/8 from the regular TRX

TCH

SDCCH  /8

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

RADIO RESOURCE MANAGEMENT SDCCH Dynamic allocation (2/3) •

Static SDCCH resource SDCCH resource created by O&M BTS must have minimum static SDCCH capacity BCCH TRX must have a static SDCCH resource

•

Dynamic SDCCH resource Reconfigured dynamically from TCH resource

Can originally be FR, DR or HR TCH resource Placement of the SDCCH resource: - Regular TRX - A TCH RTSL of least uplink interference - A TRX with minimum SDCCH configuration - A TRX with least working channels - Priority between TCH resources: HR->FR->DR