GPRS parameters

GPRSGPRSNOKIA Radio Network ParametersNOKIA Radio Network Parameters

• BSS parameters:• GPRS identifiers• Configuration parameters• Coding Scheme Management parameters• Power Control parameters

• SGSN Mobility Management parameters

GPRS Radio Planning Parameters Overview:

GPRS identifiers:

BVCI - BSSGP Virtual Connection Identifier.Identifies a GPRS cell (Range: 0 - 65535).Automatically created by the system - Rule: BTS_id + 10000.

NSEI - Network Service Entity Identifier.Identifies a PCU (Range: 0 - 65535).The NSEI is unique in the SGSN.Rule: BSC-Identifier_PCU-Identifier.

RAC - Routing Area Code.Last digit of the Routing Area Identifier (Range: 0 - 255).Digitel: 1 RAC per BSC.

Already planned by IP !!

Nokia GPRS configuration Parameters

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Setting parameters related to GPRS territory allocation

GPRS configuration parameters

• 3 territories defined for GPRS:

• dedicated GPRS territory: reserved for GPRS traffic

• default GPRS territory: for GPRS traffic per default. Default (but non-dedicated) territory can be used for CS in case of need (CS priority)

• additional GPRS territory: for CS traffic per default. Can be used for GPRS traffic if GPRS requests and CS traffic allows it (CS priority)

Note : for the calculation of HR activation/desactivation, only TS in CS domain are considered


• GPRS enabled TRX (Y/N):

• Indicates if the TRX can carry GPRS traffic (GPRS TS) ==> max GPRS capacity...

• Dedicated GPRS capacity (percentage)

• Indicates the percentage of the GPRS enabled TS that will carry dedicated TS.

• If > 0, at least 1 TS and number of TS are rounded down

• Default GPRS capacity (percentage)

• Indicates the percentage of the GPRS enabled TS that will carry dedicated or default TS.

• If > 0, at least 1 TS and number of TS are rounded down

As consequence, for 1 configuration, more than 1 parameter set is possible !!!


GPRS enabled TRX = Y

GPRS enabled TRX = N



Which percentage to have: 2 switchable (default) TS ?

Default territory = (2)/(6) = 33.3 % => min = 34 %(2+1)/(6) = 50 % => max = 50 %

CCCH/SDCCH

TCH

Digitel 4TRX configuration (general):How many GPRS-TS max ?

6 TS






Default territory = 25%Dedicated territory = 5%

How many dedicated TS ?

How many switchable TS ?

0.05*(6+8)=0.7=1 TS

0.25*(6+8)-1=2.5=2 TS

Which percentages to have: 3 dedicated TS and 2 switchable TS ?

3/(6+8) = 21.4 % => min = 22 %(3+1)/(6+8) = 28.6 % => max = 28 %

Dedicated territory =

Default territory = (3+2)/(6+8) = 35.7 % => min = 36 %((3+2)+1)/(6+8) = 42.9 % => max = 42 %CCCH/SDCCH

TCH

How many GPRS-TS max ?

6+8=14 TS

Example with ded. and def. TSs:

Nokia coding scheme management

Results of Link-level simulation for non-hopping environments

Data throughput versus C/I, TU3, non - hopping

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C/I (dB)

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Results of Link-level simulation for hopping environments

Data throughput versus C/I: TU3, hopping

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Coding Scheme selection

The initial Coding Scheme in the beginning of a connection is CS-2. CS-2 should be used instead of CS-1 when

BLER with CS-1 and FH is below the crosspoint of 11% CS-1 should be used instead of CS-2 when

BLER with CS-2 and FH is above the crosspoint of 43%. It means a kind of hysteresis: 43% 11%

The corresponding BLER for CS-2 can be determined at the same point as the throughput is the same (by definition). i.e. (1-BLER (CS-1))* CS-1 data rate_TSL = (1-BLER (CS-2))* CS-2 data rate_TSL =>BLER(CS2) = UpperThreshold

The same reasoning can be done for the non-hopping case.

BLER CS1

CS1

CS2

CS2

CS1

Lower Threshold PCU_DL_BLER_CP_HOPPING

Upper Threshold

Decision making / Risk level

The risk level parameter (PCU_UL/DL_LA_RISK_LEVEL) describes the probability with which the LA algorithm may make a wrong conclusion to reject a given hypothesis. In other words, it determines the sensitivity of the LA algorithm. The larger the risk level, the more quickly the LA algorithm is able to react to changes in BLER by switching the coding scheme but on the other hand the reliability of the switching decision is lowered as the risk level is increased.

Nokia Power Control parameters

GPRS Power Control – open loop case

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RX_LEV_DL [dBm]

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•MS_PWR_OUT = min (39dBm - ch - (RX_LEV_DL + 48), MS_PWR_MAX)

•PC1 : ch=30dB, =0,5•PC2 : ch=18dB, =0,7 (Nokia defaults)

• In packet idle mode, the MS measures the C value on each monitored PPCH block. Meanwhile, the BSS measures the interference of the candidate PDCHs in order to have CH values ready for the first transfer

period. This is transferred to the MS in the Packet Uplink Assignment.• In packet transfer mode, the MS measures the C value on the BCCH carrier and updates its output power. The BSS updates the MS specific CH values and transfer them to the MS when needed, i.e. when the

interference level has changed.

an example of the uplink power control function

Non transfer phase Transfer phase

MS measures the BCCH carrier and filters theobtained C value.MS updates the output power for each newmeasurement.

MS measures its own paging channels on PPCHand continuously updates C.

Cc CdCbCa

Non transfer phase Transfer phase

BSS measures all RLC blocks on the used PDCH.BSS updates the CH value when necessary.

BSS measures the interference of the PDCHs whichare candidates for the transfer phase.BSS continuously updates the CH values to be usedfor the first transfer period.

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MS uses Pa MS uses Pb MS uses Pc

Nokia SGSN Mobility Management Parameters

Documents

GPRS parameters