Gprs Radio

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NOKIA GPRS_radio.ppt 13.11.1998 / RRi page: 1

GPRS Radio interface

Riku Rimpel

Nokia Mobile Phones

Tampere, Finland

13.11.1998


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GPRS Air Interface features

Co-existence with GSM

"Two messages from Internet"-> fast and short interactions with the network

Sharing of resources-> more users per same carrier capacity-> connection open only when there is data to be sent-> independent up and downlink

Adaptable transfer speed-> multislot classes-> quick changes of configuration-> channel coding schemes


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Co-existence with GSMGSM Logical Channels used in GPRS

Synchronisation channels reused from traditional GSMFCCH, SCH, BCCH

GSM common control channel can be usedBCCH and CCCH

multiple new pure packet channels defined:PBCCH, PPCH, PRACH, PAGCH, PNCH, PDTCH, PACCH, PTCCH

Channel scan

Synchronization

BCCH reception PBCCH reception

Idle mode(PCH&BCCH)

Packet Idle Mode(PPCH&PBCCH)


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Co-existence with GSMGPRS multiframes

B0 B1 B2 X B3 B4 B5 X B6 B7 B8 X B9 B10 B11 X

PxxCH PxxCHPBCCH PxxCH PxxCH PxxCH PCCCH PxxCH PCCCH PxxCH PxxCH PCCCH

BCCH CCCHF S CCCH CCCHF S CCCH CCCHF S CCCH CCCHF S CCCH CCCHF S x

52-MF (BS_PBCCH_BLKS=1, BS_PAG_BLKS_RES=8, BS_PCC_CHANS=1)

51-MF combined

B0 B1x x B2 B3x x B4 B5x x B6 B7x x B8 B9x x x

PBCCH

51-MF dedicated (BS_PBCCH_BLKS=1, BS_PAG_BLKS_RES=6, BS_PCC_CHANS=1)

PCCCHPCCCH PCCCHPxxCH PxxCHPxxCH PxxCHPxxCH PxxCH


5/29NOKIA GPRS_radio.ppt 13.11.1998 / RRi page: 5

Co-existence with GSMGPRS channel structure

0 1 2 3 4 5 6 7

0 1 2 48 49 50 51

Normal burst

3

B0 B1 B2 x B3 B4 B5 x B10 B12 B11 x

47

52 Multiframe

Blocks

A timeslot dedicated for GPRS usage (PDCH)

Frame

4 bursts each



MS Network

Packet Channel Request

Packet Immediate Assignment

Packet Resource Request

Packet Resource Assignment

PRACH or RACH

PAGCH or AGCH

PACCH

PACCH

(Optional)

(Optional)

"Two messages from internet"Uplink access

After logging on two GPRS network, two messages are needed to access packetdata network



"Two messages from internet"Downlink access

Alternatively the access can be in the CCCH (PCH, RACH, AGCH, PACCH)

MS Network

Packet Channel Request

Packet Immediate Assignment

Packet Paging Response

Packet Resource Assignment

PRACH or RACH

PAGCH or AGCH

PACCH

PACCH

PPCH or PCHPacket Paging Request



Sharing of resources

Plenty of MSs can be served by the radio

Each user reserving the channel only if there is data to receive or transmit Several mobiles may be sharing the same channel (time slot)

Even tens of WWW surfers per carrier

Even hundreds or thousands of telemetry users per carrier

2-4 sec

IDLE

TRANSFER

IDLE

TRANSFER

IDLE

TRANSFER

2-4 sec

2-4 sec

IDLE

TRANSFER



Sharing of resourcesIndependent uplink and downlink

If you are going down in an elevator, there is noquarantee that somebody would be going up in the

other elevator at the same time.

=>

If you are sending data it is not guaranteed that

somebody is sending data to you at the same time.



Sharing of resourcesDownlink access

Permission to send (USF)

Acknowledgement request

MAC header Downlink data

PDTCH

PACCH

acknowledgement fordownlink data measurement report

Data in downlink

Acknowledgements in uplink (BSS allocates space for those)



PDTCH

uplink data

PDTCH

permission to send

PACCH acknowledgement to uplink data

Sharing of resourcesUplink access

Permission to send in downlink channels, acknowledgements from downlink

access methods: dynamic allocation (USF), extended dynamic allocation (E-USF),fixed allocation (FA)


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Sharing of resourcesDown&uplink access

+

Uplink transfer Downlink transfer

=>

BSS allocates both uplink and downlink capacity according to the multislot capacityof the mobile

acknowledgements for the other direction steal capacity from the transmission

flows need not be synchronized in any way


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Adaptable transfer speedMultislot classes

Type 1 MS are not required to transmit and receive at

the same time.

Type 2 MS are required to be able to transmit and receiveat the same time.

Tta relates to the time needed for the MS to perform

adjacent cell signal level measurement and get ready to transmit

Ttb relates to the time needed for the MS to get ready to transmit

This minimum requirement will only be used when adjacent cell

power measurements are not required by the service selected.

Tra relates to the time needed for the MS to perform adjacent

cell signal level measurement and get ready to receive.

Trb relates to the time needed for the MS to get ready to receive.

This minimum requirement will only be used when adjacent cell

power measurements are not required by the service selected.

Multislot

class

Maximum number of slots Minimum number of slots Type

Rx Tx Sum Tta Ttb Tra Trb

1 1 1 2 3 2 4 2 1

2 2 1 3 3 2 3 1 13 2 2 3 3 2 3 1 1

4 3 1 4 3 1 3 1 1

5 2 2 4 3 1 3 1 1

6 3 2 4 3 1 3 1 1

7 3 3 4 3 1 3 1 1

8 4 1 5 3 1 2 1 1

9 3 2 5 3 1 2 1 1

10 4 2 5 3 1 2 1 1

11 4 3 5 3 1 2 1 1

12 4 4 5 2 1 2 1 1

13 3 3 NA NA a) 3 a) 214 4 4 NA NA a) 3 a) 2

15 5 5 NA NA a) 3 a) 2

16 6 6 NA NA a) 2 a) 2

17 7 7 NA NA a) 1 0 2

18 8 8 NA NA 0 0 0 2

19 6 2 NA 3 b) 2 c) 1

20 6 3 NA 3 b) 2 c) 1

21 6 4 NA 3 b) 2 c) 1

22 6 4 NA 2 b) 2 c) 1

23 6 6 NA 2 b) 2 c) 1

24 8 2 NA 3 b) 2 c) 1

25 8 3 NA 3 b) 2 c) 1

26 8 4 NA 3 b) 2 c) 1

27 8 4 NA 2 b) 2 c) 1

28 8 6 NA 2 b) 2 c) 1

29 8 8 NA 2 b) 2 c) 1


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Adaptable transfer speedMultislot class 6

Figure 1. The basic timeslot configurations of theWD1/Gprs MS.

1+1 (a)

3+1

Rx

Rx Rx Rx

Tx

Tx

M

M

Rx Rx Tx M

Rx Rx Tx M

2+1 (a)

2+1 (b)

2+2 Rx Rx Tx Tx M

1+2 Rx MTx Tx

Figure 3. The Fixed Allocation configurations of theWD1/Gprs MS.

2+0 (c) Rx M

2+0 (b) Rx Rx M

0+1 MTx

Rx

1+1(d) Rx MTx

0+2 (a) MTx Tx

0+2 (b) TxM

0+2 (c) TxM Tx

Tx

1+1 (b) TxRx M

1+1 (c) TxRx M


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Adaptable transfer speedMultislot PDTCH channels

Multiple parallel PDTCHs can be allocated to a mobile according to its multislotclass:

In the air interface these channels are independent of each other

Data from these independent channels is reconstructed in RLC layer


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Adaptable transfer speedChannel coding schemes

Scheme

Bitrate(kbps)

Coderate

USF Pre-coded

USF

RadioBlock

excl.

USF and

BCS

BCS Tail Coded

bits

Punctured

bits

CS-1 9.05 3 3 181 40 4 456 0

CS-2 13.4 2/3 3 6 268 16 4 588 132

CS-3 15.6 3/4 3 6 312 16 4 676 220

CS-4 21.4 1 3 12 428 16 - 456 -

the coding scheme for a transfer is defined in signalling during startup

Automatic Link Adaption possible by re-assignments

Radio Blocks carrying RLC/MAC Control blocks code always use CS-1-> determined from stealing flags

the block received is not necessery intended to the receiving mobile-> possibly a different coding scheme used

interleaving same as in SACCH, i.e., one RLC block is sent in 4 bursts


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Adaptable transfer speedQuick changes of configuration

Base station system controls the allocation of channels

Network can allocate resources dynamically

When receiving data, each MS listens the allocated downlink timeslots to notice iftheir "address" (Temporary Flow Identity) is included in the block headers

When transmitting data, the mobile must listen downlink (Uplink State Flag) tosee if they have right to use the uplink in the next TDMA frame

=> many mobiles can be allocated to same timeslot and it is upto the network

to select the mobile it is sending to (compararable to fixed networks) Configuration of mobiles, I.e, allocated timeslots, are changed with signalling


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Sharing of resourcesAllocation of resources - TETRIS

Goal of resource allocation is to keep the GPRStimeslots reserved all the time

=> similar to the bottom row in TETRIS each data packet and mobile has individual needs:

QualityOfService parameters (priority)

data amount

multislot classes of mobiles

signal environment of mobiles

circuit switched needs

it is possible that the timeslots you are listeningto, are used to send data to a different mobile


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A carrier supporting GPRS - example

frames ->

timeslots->

PBCCH PDTCH1 PDTCH1 PDTCH1 PDTCH1 PPCH PDTCH1 PDTCH1 PPCH PDTCH5 PDTCH5 PPCH

BCCH CCCHF S CCCH CCCHF S CCCH CCCHF S CCCH CCCHF S CCCH CCCHF S x

x x x x

PDTCH3 PDTCH3 PDTCH3 PDTCH3 PDTCH3 PDTCH3 PDTCH3 PDTCH1 PDTCH1 PDTCH4 PDTCH4 PDTCH4x x x x

PDTCH2 PDTCH2 PDTCH2 PDTCH2 PDTCH2 PDTCH2 PDTCH1 PDTCH1 PDTCH1 PDTCH1 PDTCH1 PDTCH1x x x x

PDTCH2 PDTCH2 PDTCH2 PDTCH2 PDTCH2 PDTCH2 PDTCH1 PDTCH1 PDTCH1x x S x

TCH2 S TCH2 x TCH2 S TCH2 x

TCH2 x TCH2 S TCH3 x TCH3 S

TCH1 S TCH1 x TCH1 S TCH1 x

TCH4

F

four timeslots in a BCCH carrier dedicated to GPRS


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Conclusion

Data packet ->

Data packet ->

LLC PDU ->

LLC PDU ->

RLC blocks ->

RLC blocks ->

Multislot channel ->


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Additional slides


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GPRS MS Classes

Class A

Simultaneous GPRS and speech

No network coordination standardised

MS must be capable of handling two (multislot) calls/connections

Class B

GPRS and speech capabilities do not operate simultaneously

Circuit switched pagings are received while in GPRS mode GPRS may put put to suspend mode while speaking on the phone

GPRS-Speech-GPRS alternation possible without disconnection

Speech-GPRS-Speech not possible without disconnection

Class C

Manual switching between GPRS and speech modes

No circuit switched pagings while on GPRS

GPRS h l


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PBCCH B1 B2 B3 B4 PPCH B6 B7 PPCH PAGCH B10 PPCHDownlink

Uplink

GPRS channelsGPRS channels in practice

BS_PBCCH_BLKS=1, BS_PAG_BLKS_RES=8, BS_PCC_CHANS=1,BS_PRACH_BLKS=2

1

2

PBCCH usf B2 B3 PDTCH PPCH B6 usf PPCH B9 B10 PPCH

PRACH B1 B2 B3 B4 B5 PRACH B7 B8 B9 B10 B11

3 5 6

7

PRACH B1 PDTCH B3 B4 B5 PRACH B7 PDTCH B9 B10 B11

8

9 10 11 12 13 15 16

14

MULTIFRAME1

Downlink

UplinkMULT

IFRAME2

4


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Mobile states

Mobility Management (MM) state

Idle, Standby, Ready

deals only with location related issues

independent of RR state

Radio Resource (RR) state

Packet Idle Mode, Packet Transfer Mode

deals only with transfer related issues

independent of MM state


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MM State Diagram for MS

PDU

transmission

GPRS

Attach

READY timer

expiry or

Force to STANDBY

STANDBY timer

expiry

GPRS

Detach

IDLE

READY

STANDBY

=> power off

=> active mode (2-4 sec)

=> idle mode

GSM equivalents


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MM StatesIdle

GPRS network does not know anything about the mobile

No GPRS MM context

No GPRS routing context

Standby

MM information on Routing Area (RA) level

MM context and LLC link active

PTM-M and Pagings for Circuit Switched, PTP and PTM-G may be received

Routing Area Update - paging area may be different from location areasReady

MM information on cell level - Cell Update - to enable quick packet delivery

Transmission

Reception without paging - just a Packet Immediate Assignment

Supervised by a timer (Ready to Standby)

GPRS Detach if movement to Idle desired


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RR States

Packet Idle Mode

No Radio context between MS and BSS

Cell Re-Selection

Reception of Paging

Packet Transfer Mode

Radio context between MS and BSS open - Temporary Block Flow (TBF)

Downlink packet sent without paging

When TBF is released -> move to Packet Idle Mode

Cell Re-Selection done only in Packet Idle Mode - No handovers

Packet Transfer

Mode

Packet Idle Mode

change to new cell

Packet Transfer

Mode, new cell

Initiate Cell Re-Selection Re-Initiate Temporary Block Flow

MAC operations


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MAC operationsUplink access methods

Dynamic access

USF gives permission to send in thecorresponding uplink slot during thenext one or four block periods(defined by parameterUSF_GRANULARITY).

Extended Dynamic

access

USF gives permission to send in thecorresponding and all the laterallocated uplink slots during thenext block period.

Fixed allocation

Resource assignment indicates thereserved uplink blocks andacknowledgement blocks.

MAC operations


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MAC operationsMultiple transfers and mobiles

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