2 GSM GPRS Radio Access

7/30/2019 2 GSM GPRS Radio Access

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Mobile Communications

1. Basic concepts

2. GSM/GPRS radio access

3. GSM/GPRS architecture and protocols

4. Universal Mobile Telecommunications System radio access

5. UMTS radio resource management

6. UMTS architecture and protocols

7. High Speed Down Link Packet Access

8 LTE

9. LTE ADVANCED

10. Mobile Network Engineering


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2.1 Physical layer2.2 Radio resource management



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2.1 Physical layer

frequencies and accessTDMA and GSM;

physical and logical channels in GSM and GPRS

coding

modulation techniques

GPRS physical layer

extensions:frames, super-frames, hyper-framese2.1

modulation techniquee2.2

e2.3 acquisition

GPRS timing advance

and power controle2.4


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FREQUENCY

SYSTEMBANDWIDTH

TIME

SCPC / FDMAsingle channel per carrier/frequency division multiple access


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FREQUENCY

FRAME INTERVAL

TIME

TDMATime Division Multiple Access


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FREQUENCYCODE

TIME

DS-CDMA

Direct Sequence - Code Division Multiple Access


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Space Division Multiple Access

.other words for frequency re-use

Theoretical Cluster

1

23

4

5

6

7 1

2

3

4

56

7

1

2

3

4

56

7

1 2 3 4 5 6 7

bandwidth


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Duplex operation

Rx RxTx Tx

frame

Time Division

Duplex mode

Frequency Division

Duplex mode

t

f-up f-down

f

system bandwidth


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GSM: the available bandwidth

Uplink

(MHz)

Downlink

(MHz)

Duplex

spacing

(MHz)

Bandwidth

(MHz)

P-GSM 900

E-GSM 900

R-GSM 900

GSM 450

GSM 480

GSM 750

890 915

880 915

876 915

1710 17851850 1910

450,4 457,6

478,8 486

747 762

824 849

935 960

925 960

921 960

1805 18801930 1990

460,4 467,6

488,8 496

777 792

869 894

DL=UL+45

DL=UL+45

DL=UL+45

DL=UL+95DL=UL+80

DL=UL+10

DL=UL+10

DL=UL+30

DL=UL+45

25

35

39

7560

7,2

7,2

15

25

GSM 900

DCS 1800PCS 1900

GSM 400

GSM 700

GSM 850


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GSM frequencies @ 900 MHz in Italy

TIM

WIND

OPIGSM TIMTACS GSM OPI

880,0 892,0 892,3 900,5 905,5 913,741 channels 41 channels

15 chann 9 channels16 cities

chan. 12-67 chan. 69-118

925,0 937,0 937,3 945,5 950,5 958,7

Other Italy (chan. 54-76)outside the 16 towns

TIM

WIND

OPI

GSM TIMTACS GSM OPI

41 channels 41 channels880,0 891,8 892,1 900,3 905,5 913,7

925,0 936,8 937,1 945,3 950,5 958,7

Other Italy (chan. 53-76)

outside the 16 towns

15 channels 10 channels16 citt

chan. 11-66 chan. 68-118

01.11.1998

01.03.1999


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TIM

WIND


43 channels * 42 channels880,0 891,2 891,5 900,1 905,3 913,7

925,0 936,2 936,5 945,1 950,3 958,7

Other Italy 24 channelsoutside the 16 towns

57 channels 53 channels16 towns

CTI

915

960

15.09.1999

900 MHz frequencies - evolution

TIM

WIND


42 channels 42 channels880,0 891,4 891,7 900,1 905,3 913,7

925,0 936,4 936,7 945,1 950,3 958,7

Other Italy 24 channelsoutside the 16 towns

57 channels 52 channels16 towns

CTI

915

960

01.07.1999


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Frequencies @ 1800 MHz

TIMTIM

1755

1850

WINDWIND

1865

1770

24 channels

1855

1760

24 channels50 channels

4th Operator4th Operator OPIOPI

1780

1875

1780

1880

50 channels

from 01.01.99 in 8 towns:RM, MI, NA, TO, BO, PA, FI, GE

from 01.07.99 over the whole national territory


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MSCMSC

BSCBSC

BSCBSC

BSCBSC

900 MHz900 MHz

BTSBTS

900 MHz900 MHz

BTSBTS

1800 MHz1800 MHz

BTSBTS

1800 MHz1800 MHz

BTSBTS

GSM 1800: the compatibility value


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BURSTTRANSMITTED

BY

TDMA FRAME(4.6 ms)

MOBILE 1

MOBILE 2

MOBILE 8TIME

TIME-SLOT: 577 s SIGNAL BURST: 543 s

GSM functions - TDMA access technique


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Time and power control

MS

p

t

BTS

tr, pr

tr: time of arrival of the MS burst

pr: received power

d

t

TS TS

Timing advance

TS TS

power control

. . . . . .

2dB granularity


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Time and power control (II)

-70

+4

-6

-30

power (dB)

10 8 10 10 8 10

s s

542.8 s

28 s to rump-up and 28 s to

switch-off max dynamic range of 70 dB 542 s to transmit

information

148 bit


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Burst structure

normal burst

T3

S1

S1

13

GP8.25

Coded Data57

Training Seq.26

Coded Data57

TypeNumber of Bits

148 Bit = 546.12 s

Stealing flagGuard Time

Tail bits

(guard bits)


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Burst structure (II)

random access burst

T

8T

3

Synchr. Seq.

41

Coded Data

36

GP

68.25

Type

Number of Bits

88 Bit = 324.72 s

TrainingGuard Period

Tails

Guard Period limiting

the max cell radius


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Burst structure (III)

frequency correction and synchronisation burst

T

3

T

3

Fixed bit sequence

142

GP

8.25

Type

Number of Bits

148 Bit = 546.12 s

Guard Period as for

the Normal BurstTails

Guard Period limiting

the max cell radius

Found syncr.


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GSM traffic channels

TCH/FS: Traffic Channel Full rate Speech

Speech transmission at a net bit rate of 13 Kbit/s (up anddown link)

TCH/HS: Traffic Channel Half rate Speech Speech transmission at half bit rate (up and down link)

TCH/F: Traffic Channel for Data transmission Data transmission at 9.6/4.8/2.4 Kbit/s (with different coding

schemes)

TCH/H: Traffic Channel for Data transmission Data transmission at halved speed (with different coding

schemes)


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BCCH: Broadcast Control Channel

point-to-multipoint unidirectional control channelbroadcasting system information to MS

CCCH: Common Control Channelup-link: RACH (Random Access CHannel)

down-link: PCH (Paging Channel)AGCH (Access Grant CHannel)

DCCH: Dedicated Control CHannel point-to-point bidirectional control channel

SACCH (Slow Associated Control CHannel)

FACCH (Fast Associated Control CHannel)

SDCCH (Stand Alone Dedicated Control CHannel)

GSM signalling channels


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..some other broadcast channels

FCCH: the Frequency Correction Channel Gives the mobile station the reference frequency of the

system

SCH: the Synchronisation Channel Gives the mobile station the training sequence for

demodulate the down-link information


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R

51 frames - 235.38 ms

D0 D1 D2 I I ID4 D5 D6 D7 A0 A1 A2 A3D3

D0 D1 D2 I I ID4 D5 D6 D7 A4 A5 A6 A7D3

F S B C F S F S F S F S IC C C C C C C C

D0 D1 D2I I I D4 D5 D6 D7 A0

A1 A2 A3

D3

D0 D1 D2I I I D4 D5 D6 D7 A4

A5 A6 A7

D3

BCCH + CCCH

(downlink)

BCCH + CCCH

(uplink)

8 SDCCH/8(downlink)

8 SDCCH/8

(uplink)

R R R R R R R R R R R R R R R R R R R R R R RR R R R R R R R R R R R R R R R R R R R R R R R R R R

F: TDMA frame for frequency correction burst

B: TDMA frame for BCCH

D: TDMA frame for SDCCH

R: TDMA frame for RACH

S: TDMA frame for synchronization burst

C: TDMA frame for CCCH

A: TDMA frame for SACCH/C

GSM - logical and physical channels


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51 frames - 235.38 ms

D3 RR A2 A3 D1 RR D2D0RRRRRRRRRRRRRRRRRRRRRRR

D3 RR A0 A1 D1 RR D2D0RRRRRRRRRRRRRRRRRRRRRRR

F S B C F S F S F S F S IC C D1 D2 D3 A0 A1

F S B C F S F S F S IC C

D0

D1 D2 D3 A2 A3D0 F S

BCCH + CCCH

+ 4 SDCCH/4(downlink)

BCCH + CCCH+ 4 SDCCH/4

(uplink)

F: TDMA frame for frequency correction burst

B: TDMA frame for BCCH

D: TDMA frame for SDCCH

R: TDMA frame for RACH

S: TDMA frame for synchronization burst

C: TDMA frame for CCCH

A: TDMA frame for SACCH/C

GSM - logical and physical channels


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T T IT T T T T T T T T T T T A T T T T T T T T T T

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

120 ms

TDMA Frame

T: Traffic Channel (TCH)A: Slow Associated Control Channel (SACCH)

2 1 21 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1

120 ms

T T AT T T T T T T T T T T T A T T T T T T T T T T

Full Rate Channel

Half Rate Channels

GSM - associated channels


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GSM radio transmission and reception chain

a conceptual scheme

Channelencoder

orderingpartitioning

interleaving

ciphering burstformat

TxGSMmodulator

filters,

coherent

demodulat.

synchronisation

Viterbi equaliserBB demodulation

deciphering

burst

de-muxde-format

de-interleavingchannel decoder

Propagation channel

Source data

Output bits


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Speech coding

band-pass

AD

D

Alow pass

speech

decoder

speechencoder

channelcoder

channel

decoder

300 Hz

3.4 KHz

4 KHz

microphone

loud

speaker

t

analogue sampled

coded

1111111011011100

213

coding levels


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Channel codingand other protection mechanisms

Block codes

Convolutional codes

Distinction between: Speech data

Data services

Signalling data

Interleaving

Retransmission

Detection

Correction


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Channel coding

speech data

skbitsKbit /833.27012/138114/25.156/8.22 =

# of bits transmitted

per normal burst

information bits

per normal burst

multiframe inefficiency

for associated channel

voice

coding

13 Kbit/s

4 tail bitsReordering

(185)

convolutional

encoding

(1/2; L=5)

block code

(53, 50)

Channel encoding

260 bit

20 ms

50(1a)

132

(1b)

189

78 (2)

456 bit (20 ms)

22.8 kbit/s

Global bit rate

needed


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Reordering and Interleaving

speech data

10 1065432 987 13 141211 15

odd

even

burst

Voice sub-frames (reordering)

1 0 + i 8

2 1 + i 83 2 + i 8

4 3 + i 8

5 4 + i 8

6 5 + i 8

7 6 + i 88 7 + i 8

i = 0, 1, 2, .

114 bits transmitted

in each burst

Interleaving depth

= 8 bursts


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Channel coding and interleaving

data streams

data stream 9.6 kbit/s

terminal

codingdata stream 12 kbit/s

240 bit (12 kbit/s)

488 bit

456 bit

4

Convolutional encoding

R=1/2; L=5

Puncturing of 32 bit

6 12 18 24 24 24

6 12 18 24 24

10 1065432 987 13 141211 15

24 24 18 12 6

16 19 201817 21

22 blocks fromthe 456 data frame:

16 x 24 bit

2 x 18 bit

2 x 12 bit

2 x 6 bit


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Channel coding

signaling streams

10 1065432 987 13 141211 15

456 bit

Convolutional encoding

R=1/2; L=5

signaling info 184 bit parity 40 4

signaling info 184 bit

Block code (224, 1840)

odd

even

Spreading of the signalingblock over 4 consecutive

bursts

burst


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Base band frequency hopping

fi

fj

fk

TDMA frame

original allocation of the connection in progress

new frequency allocation through a frequency hopping mechanism

carriers

assigned to the

cell

network assigned jumping scheme


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Base band frequency hopping (I)

fk(t)

fk(r)

fi(r)

fj(r)

fl(r)

fi(t)

fj(t)

fl(t)

TDMA frame

TDMA frame

MS receiving

MS transmitting

measuring windows


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Modulation techniques

I

Q

Binary Phase Shift Keying

Quadrature Phase Shift KeyingI

Q

10

00

01

10

11


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GPRS - the physical layer

sharing resources and functions with GSM

Radio resource sharing withGSM voice and data services

Dynamic & static allocation of

the physical channels One or more slots to a singleGPRS user

One or more GPRS users on asingle slot

Radio-frequency partunchanged

Voice serviceGPRS service

dynamic border

variation

priority to voice

services

TDMA frame

slot sharingdata 2data 1


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GPRS data flow

BH Info Field BH Info Field BHBH Info FieldPrimary Block Following Blocks ...

FH Information Field FCSFrame

(LL-PDU)

Blocks

SNDCP layer

LLC layer

Physical layer

PH User DataPacket (N-PDU) Network layer

Compression/Decompression

Segmentation/Re-assembly (not shown)

Channel coding

Reordering & Partitioning

Interleaving

Burst formatting

RLC/MAC layer

Normal Burst Normal Burst Normal BurstNormal Burst

SH Information FieldSN-PDU

FH = Frame Header

FCS = Frame Check Sequence

BH = Block HeaderPH = Packet Header SH = SN-PDU Header


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Radio block coding

USF pre-coding

4 tail bits

rate 1/2 convolutional coding

puncturing

456 bits

USF BCSPayload

stealing flags

normal burst

CS1

CS2

CS3

CS4


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Coding parameters

SchemeCode

rate

Payload

(bits)

BCS

(bits)

Coded

bits

Tail

bits

Punctured

bits

Data rate

(kbps)

CS-1 1/2 181 40 4564 0 9.05

CS-2 ~ 2/3 268 16 5884 132 13.4

CS-3 ~ 3/4 312 16 6764 220 15.6

CS-4 1 428 16 456- - 21.4

Pre-coded

USF (bits)

3

6

6

12


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Scheme Maximum net payload(bytes)

Maximum netRLC/MAC data

rate (kbit/s)

Nominal data rate(kbit/s)

Application datarate (kbit/s)

CS-1 20 8 9.05 7.7

CS-2 30 12 13.4 11.5

CS-3 36 14.4 15.6 13.8

CS-4 50 20 21.4 19.2

Data rates

Application data rate (kbit/s) @ IP packet size (bytes)

Coding scheme 576 1200 1500

CS-1 7.3 7.7 7.7

CS-2 11 11.5 11.6

CS-3 13.2 13.8 13.9

CS-4 18.3 19.2 19.4


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00 11 77

RxTra

Rx

00 11 77

Tx

00 11

TtTt TxTx

00 77 00 11

TtaRx

Rx

00 77 00 11

Tra

11

Tx

Symmetric servicehalf-duplex terminal

Asymmetric service

half-duplex terminal

Tta : time to Tx

Tra: time to Rx

Time Slot Utilisation - simplex Terminal

Ttb : time to Tx,

no measures

Trb: time to Rx,

no measures

GPRS ph sical la er performance (II)


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GPRS: physical layer performance (II)

GSM @ 900 MHz (05.05) PDCH BLER 10%USF BLER 1%

PRACH BLER 15%

propagation

sensitivity

levels

C/I levels

PDTCH/CS1 (dBm) -104 -104 -104 -104 -103

PDTCH/CS4 (dBm) -101 -90 -90 --- ---

USF/CS1 (dBm) -104 -101 -103 -103 -101

PRACH/11 bit (dBm) -104 -104 -104 -103 -103

PDTCH/CS1 (dB) 13 9 10 9 9

PDTCH/CS4 (dB) 21 23 24 24 ---

USF/CS1 (dB) 19 10 12 10 10

PRACH/11 bit (dB) 8 8 8 8 10

Propagat. Charact.: static TU50 TU50 RA250 HT100

noFH ideal no FH no FH

FH

Propagat. Charact.: TU3 TU3 TU50 TU50 RA250

no FH ideal no FH ideal no FH

FH FH


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Reordering and interleaving

10 1065432 987 13 141211 15

odd

even

burst

456 bit (8x57bit)

4 bursts for transmission

rectangular interleaving

Interleaving depth 8:

minimising the BER (afterdecoding)

increasing the probability of blockre-transmission or erasure

Interleaving depth 4:

increasing the BERdecreasing the

probability of block re-

transmission or erasure


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BCCH

(CCCH)

radio packetsystem

broadcasting

GPRS channels - general

BTS

PBCCH(PCCCH)

GPRS dedicated broadcast

and Common Control

channels

Broadcast and Common

Control Channels shared with

GSM

GPRS specific system data

+

GSM system data

Only PCCCH has to be tracked by MS


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Packet Data Logical Channels (I)

Packet Common Control Channel (PCCCH): PRACH: random access (uplink)

PPCH: paging (downlink)

PAGCH: access grant (downlink)

PNCH: PTM-M notification (downlink)

Packet Broadcast Control Channel (PBCCH) (downlink)

Packet Traffic Channels: PDTCH: data traffic (up and down link)

Packet Dedicated Control Channels: PACCH: associated control (up and down link)

PTCCH/U: timing advance estimation (uplink))

PTCCH/D: timing advance information (downlink)

P k D L i l Ch l (II)


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Packet Data Logical Channels (II)

The radio blocks are transmitted over 4 bursts belonging to 4 consecutive

TDMA frames

Transmission on a Packet Data CHannel (PDCH):

transmission on PRACH and PTCCH/U is performed by sending anaccess burst

transmission on all the other packet data logical channels isperformed by sending radio blocks constituted by four consecutivenormal bursts

a Packet Control Acknowledgement can be sent via 4 accessbursts, if required by the network

P k t D t L i l Ch l (III)


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Packet Data Logical Channels (III)

PBCCH is mapped on one physical channel

PCCCH is mapped on one or several physical channels, following a 52-multiframe

PRACH is determined by Uplink State Flag (USF) set FREE and broadcaston the downlink or by a fixed allocation

A given PDTCH is mapped on one physical channel An MS can use up to 8 PDTCHs on the same carrier

A given PACCH is mapped on one physical channel and is allocateddynamically on a block basis

PTCCH/U is mapped on one of the PDCHs where PDTCHs are allocated to theMS; PTCCH/D is associated to several PTCCH/Us sharing the same PDCH

M ltif St t


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Multiframe Structure

52 TDMA frames divided in:

12 radio blocks B0-B11 (of 4consecutive frames)

2 frames used for PTCCH (T)

2 idle frames (X)

TDMA Frame 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

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

Idle frames

Radio Blocks

Frames for PTCCH

BCCH

MS

PDCH on which

PBCCH and

PCCCH are

mapped

A i l ltif d t


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A single multiframe - advantages

GSM multi-frames:

26 TDMA frames for voice/data

51 TDMA frames for BCCH, CCCH, SDCCH

26 frame voice, data

51 frame signaling

52 frame for signaling and traffic

GPRS multi-frame:

52 TDMA frames for data and signaling

statistical behaviour of data services

need for higher degree of flexibility

Key elements

for a choice:



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2.1 Physical layer

2.2 Radio resource management


2 GSM/GPRS radio access


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2.2 Radio resource management

GPRS radio resource management

static and dynamic channel allocation

GPRS Downlink Radio Blocks


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Data Block

Control Block

RLC/MAC Control Block

Radio block

MAC HdrControl Header

(optional)RLC/MAC Signaling

MAC Header

RLC Data Block

Radio block

RLC Header RLC Data

USF S/P RRBP

Payload

Type

MAC Hdr

Spare bits

(if any)




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The radio blocks adopt different configurations in function of the transmission direction (upordown link). Moreover, their configuration depends on the role they are assigned to: data orcontrol transport.

The radio block is subject to retransmission for error protection. The retransmission doesnot take place for a single radio block but for a group of radio blocks: those contained in theretransmission window, concerning 64 radio blocks (both in the up and in the down link).The retransmission involves then more than one GPRS users: those who can share the same

time slot. The MAC layer contains the headerof the upper layer frames (RLC). As for the MACheader, it contains some data range driving the retransmission mode.

The Up Link State Flag (USF) transmitted on the down link, is composed of 3 bits. It specifiesthe MS which is allowed to transmit on the up link along the 4 subsequent time slots (1block) and, set to 0, the presence of a Packet Random Access Channel (PRACH) always onthe up link. Hence, the maximum user multiplexing level on the up link over the same timeslot is 7. Often on the up link, some signalling messages associated to the traffic received on

the down link are to be transmitted: another USF value has then to be reserved. This reducesto 6 the maximum multiplexing degree on the up link.

The supplementary/polling (S/P) range contains1 bit; it states the presence (or the absence)of the subsequent range.

The Relative Reserved Block Period (RRBP) is composed of 2 bits specifying the radio blockperiod when the MS must transmit a control packet which may be for instance a PacketControl Acknowledgement (PACK) transmitted over a Packet Associated Control Channel

(PACCH). The MS that has to transmit is the one identified by the Temporary Flow Identity(TFI) specified in the RLC header.

The Payload Type (2 bits) specifies the kind of information transported by the radio block(Data or Control) and, whenever the block is a control block, it specifies if the subsequentrange (RLC header) present or not present.

GPRS Uplink Radio Blocks


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Data Block

RLC Data Block

Radio block

RLC Header RLC Data

Control Block


Radio block

MAC Hdr

MAC Hdr RLC/MAC Signaling

MAC Header

RCountdown

value

Payload

TypeSI

MAC Header

R sparePayload

Type

Spare bits

(if any)




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On the up link the following ranges are present: The Retry (R) (1 bit) designates if the MS has sent the Packet Channel

Request at least one time within the Temporary Block Flow (TBF). The TBFdefines a physical connection utilised for one or more LL-PDU over one or

more PDCH in a point-to-point mode between the MS and the Network. The Stall Indicator(SI) is composed by 1 bit. It establishes if the counter of

the transmission window at the RLC level can be either increased or not.

The Countdown Value bears 4 bits specifying how many RLC data blocksare still to be transmitted within the current Temporary Block Flow. The

Spare range (5 bit) are not utilised by teh network.

The Payload Type (2 bits) specifies as for the down link, the kind ofinformation carried by the radio block (Data or Control) and, whenever theblock is a control block, it specifies if the subsequent range (RLC header)is either present or not.

p

RLC header and data - data block


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Data Block

up and down link)

Control Block

(down link)


Radio block

MAC HdrControl Header

(optional)RLC/MAC Signaling

RLC Header

RLC Data Block

Radio block

RLC Header RLC Data

2 byte

MAC Hdr

Spare bits

(if any)

RLC header and data data block

2 byte

RLC Header


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Uplink Transmission and contention resolution


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p

MS NetworkPacket Channel Request

Packet Uplink Assignment

Packet Resource Request


PRACH or RACH

PAGCH or AGCH

PACCH

PACCH

(Optional)

(Optional)

Access

PRACH

random choiceMS

retransmission

MS network

Packet Channel Req.

Packet uplink assig.

PRACH

PAGCH

physical channels

assigned (PDCH)

USF for each

PDCH assigned

TFI (TBF)

established

1 physical channel

assigned (PDCH)

Packet resource req.

MS>netw. over PDCH

Packet uplink assign.

(USF, TFI)

1-phase 2-phases

Contention resolution and resource allocation


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Data Block

Packet Uplink Ack/Nack

Data Block (last)

Access and Assignment

MS Network

PDTCH

PACCH

PDTCH


Packet Control AcknowledgementPACCH

PACCH

Data BlockPDTCH

Data BlockPDTCH

Data Block (last in send window)

PDTCH

Data BlockPDTCH

Data BlockPDTCH

Data BlockPDTCH

Data BlockPDTCH

Packet Uplink Ack/Nack (final) PACCH

Uplink data transfer

Resource allocation

Possible limitations (network side) on

the number of transmitted blocks

Selective retransmission required

through Packet uplink Ack/Nack

Resource re-assignment along the

packet transfer:

packet uplink assign. (over PACCH andbearing the RRBP for answer)

packet control acknowledgment viaPACCH reserved through RRBP

Resource release started by MS throughcount/down procedure.

Packet uplink final ACK (netw.) and

Packet control ack (MS) are sent

Uplink transfer channel allocation


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p

Dynamic Allocation:

the MS transmits its radio blocks on the assigned time

slots with the assigned USF

Fixed Allocation:

fixed uplink resource allocation to the MS based on a

bitmap indicating the assigned blocks per time slot No need to monitor the downlink for the USF

Extended Dynamic Allocation:

monitoring of the USF without transmitting and receivingsimultaneously

2 GSM GPRS Radio Access

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