11.2.7 Packet Downlink Assignment

04.603GPPGeneral Packet Radio Service (GPRS)Mobile Station (MS) - Base Station System (BSS) interfaceRadio Link Control / Medium Access Control (RLC/MAC) protocolRelease 1999TS

This message is sent on the PCCCH or PACCH by the network to the mobile station to assign downlink resources to the mobile station.

For a mobile station assigned to operate in the fixed allocation MAC mode, the network may assign regularly repeating intervals during which the mobile station shall measure neighbour cell power levels. A mobile allocation or reference frequency list received as part of this assignment message shall be valid until a new assignment is received or each TBF of the MS are terminated.

Message type: PACKET DOWNLINK ASSIGNMENT

Direction: network to mobile station

Classification: non-distribution message

Table 11.2.7.1: Packet Downlink ASSIGNMENT information elements

< Packet Downlink Assignment message content > ::=

< PAGE_MODE : bit (2) >

{ 0 | 1 <PERSISTENCE_LEVEL : bit (4) > * 4 }

{ { 0 < Global TFI : < Global TFI IE > >

| 10 < TLLI : bit (32) > }

{ 0 — Message escape

{ < MAC_MODE : bit (2) >

< RLC_MODE : bit (1) >

< CONTROL_ACK : bit (1) >

< TIMESLOT_ALLOCATION : bit (8) >

< Packet Timing Advance : < Packet Timing Advance IE > >

{ 0 | 1 < P0 : bit (4) >

< BTS_PWR_CTRL_MODE : bit (1) >

< PR_MODE : bit (1) > }

{ { 0 | 1 < Frequency Parameters : < Frequency Parameters IE > > }

{ 0 | 1 < DOWNLINK_TFI_ASSIGNMENT : bit (5) > }

{ 0 | 1 < Power Control Parameters : < Power Control Parameters IE > > }

{ 0 | 1 < TBF Starting Time : < Starting Frame Number Description IE > > }

{ 0 | 1 < Measurement Mapping : < Measurement Mapping struct > > }

{ null | 0 bit** = <no string> — Receiver backward compatible with earlier version

| 1 — Additional contents for Release 1999

{ 0 | 1 < EGPRS Window Size : < EGPRS Window Size IE >>

< LINK_QUALITY_MEASUREMENT_MODE : bit (2) >

{ 0 | 1 < BEP_PERIOD2 : bit(4) > }}

{ 0 | 1 <Packet Extended Timing Advance : bit (2)> }

{ 0 | 1 < COMPACT reduced MA : < COMPACT reduced MA IE >> }

< padding bits > }} // — truncation at end of message allowed, bits ‘0’ assumed

! < Non-distribution part error : bit (*) = < no string > > }

! < Message escape : 1 bit (*) = <no string> > }

! < Address information part error : bit (*) = < no string > > }

! < Distribution part error : bit (*) = < no string > > ;

< Measurement Mapping struct > ::=

< Measurement Starting Time : < Starting Frame Number Description IE > >

< MEASUREMENT_INTERVAL : bit (5) >

< MEASUREMENT_BITMAP : bit (8) > ;

Table 11.2.7.2: PACKET Downlink ASSIGNMENT information element details

PAGE_MODE (2 bit field)
This field is defined in sub-clause 12.20.

PERSISTENCE_LEVEL (4 bit field for each Radio Priority 1…4)
This field is defined in sub-clause 12.14, PRACH Control Parameters.

Global TFI
This information element contains the TFI of the mobile station’s downlink TBF or uplink TBF. This field is defined in sub-clause 12.10.

TLLI (32 bit field)
This field is defined in sub-clause 12.16.

MAC_MODE (2 bit field)
This information field indicates the medium access method to be used during the TBF.

bit
2 1
0 0 Dynamic Allocation
0 1 Extended Dynamic Allocation
1 0 Fixed Allocation, not half duplex mode
1 1 Fixed Allocation, half duplex mode

RLC_MODE (1 bit field)
This field indicates the RLC mode of the requested TBF.

0 RLC acknowledged mode
1 RLC unacknowledged mode

CONTROL_ACK (1 bit field)
This field shall be set to ‘1’ if the network establishes a new downlink TBF for the mobile station whose timer T3192 is running. Otherwise this field shall be set to ‘0’.

TIMESLOT_ALLOCATION (8 bit field)
This field is defined in sub-clause 12.18.

Packet Timing Advance
This information element is defined in sub-clause 12.12.

P0 (4 bit field)
For description and encoding, see the Packet Uplink Assignment message.

BTS_PWR_CTRL_MODE (1 bit field)
For description and encoding, see the Packet Uplink Assignment message.

PR_MODE (1 bit field)
For description and encoding, see the Packet Uplink Assignment message.

Power Control Parameters
This information element is defined in sub-clause 12.13.

Frequency Parameters
This information element is defined in sub-clause 12.8.

DOWNLINK_TFI_ASSIGNMENT (5 bit field)
This information element, if present, assigns the TFI to the mobile station to identify the downlink TBF described by this message. TFI is encoded as defined in sub-clause 12.15.

TBF Starting Time
The TBF Starting Time field contains a starting time that indicates the TDMA frame number during which the assigned TBF may start. If no downlink TBF is in progress, the mobile station need not monitor the TFI field of downlink RLC data blocks until the indicated TDMA frame number. After the indicated TDMA frame number, the mobile station shall operate as during a downlink TBF. If a downlink TBF is already in progress, the mobile station shall continue to use the parameters of the existing TBF until the TDMA frame number occurs. When the indicated TDMA frame number occurs, the mobile station shall immediately begin to use the new parameters assigned. This information element is defined in sub-clause 12.21.

Measurement Starting Time
The Measurement Starting Time field contains a starting time that indicates the frame number during which the first assigned measurement period shall occur. The mobile station must make one or more neighbour cell power measurements during the assigned frame number and during the following 3 TDMA frames. This information element is defined in sub-clause 12.21.

MEASUREMENT_BITMAP (8 bit field)
This information field indicates the timeslots assigned for use during measurement periods. The field is a bitmap where each bit corresponds with a timeslot number. Bit 1 corresponds to TS0; Bit 2 to TS1, etc.

0 the MS shall receive downlink data during this timeslot
1 the MS shall make measurements during the timeslot

MEASUREMENT_INTERVAL (5 bit field)
The Measurement Interval field indicates the number of block periods from the start of one assigned measurement period to the beginning of the next measurement period.

bit
5 4 3 2 1
0 0 0 0 0 make measurements during every block period
0 0 0 0 1 make measurements during every other block period
0 0 0 1 0 make measurements during every 3rd block period
. . .
1 1 1 1 1 make measurements during every 32nd block period

EGPRS Window Size
This information element is defined in sub-clause 12.5.2.

LINK_QUALITY_MEASUREMENT_MODE (2 bit field)

This field determines the measurements to be included within the EGPRS Timeslot Link Quality Measurements IE.

bit
2 1

0 0 The MS shall not report either interference measurements ( values) or per slot BEP measurements.

0 1 The MS shall report available interference measurements ( values) for timeslots 0 through 7. The  value is defined in 3GPP TS 05.08. No per slot mean BEP measurements shall be reported.

1 0 The MS shall report mean BEP on each allocated time slot. The MS shall report the mean BEP measurement corresponding to the modulation for which it has received a larger number of blocks since the previous report. The MS shall make BEP measurements only on Radio Blocks intended for it. No interference measurements ( values) shall be reported.

1 1 The MS shall report mean BEP on each allocated time slot. The MS shall report the mean BEP measurement corresponding to the modulation for which it has received a larger number of blocks since the previous report. The MS shall make BEP measurements only on Radio Blocks intended for it. In addition to mean BEP, the MS shall report interference measurements ( values) for no more than four time slots. The MS shall first report available interference measurements for time slots 0, 1, 2, and 3; the MS shall next report available interference measurements for time slots 4, 5, 6, and 7; and the MS shall alternate between these two groups for subsequent reports. If any of the interference measurements are unavailable for reporting for reasons specified in 3GPP TS 05.08, the MS shall substitute least-recently-reported and available interference measurements for time slots not already included in the report.

Packet Extended Timing Advance (2 bit field)
This field is defined in sub-clause 12.12b.

COMPACT reduced MA

This information element is defined in sub-clause 12.29.

BEP_PERIOD2 (4 bit field)
This field contains a constant which is used for filtering channel quality measurements in EGPRS. BEP_PERIOD2 when present, or if not, when received in a previous message of the same TBF session, shall be used instead of BEP_PERIOD. For details see 3GPP TS 05.08.

Range: 0 to 15

11.2.7.1 Special requirements in dual transfer mode for downlink TBF

Special requirements apply when a downlink TBF is assigned to a mobile station in dual transfer mode or a mobile station about to enter dual transfer mode.

If the mobile station has an RR connection to the network on a half-rate TCH, the network may assign a downlink TBF using the other sub-channel of the same timeslot for a half-rate PDCH (see 3GPP TS 05.02). In this case, the downlink assignment message shall be encoded with a timeslot allocation including the timeslot number for the half-rate TCH and the half-rate PDCH and only that timeslot number. The mobile station shall interpret this allocation as an allocation of a half-rate PDCH.