OMF000001 Um Interface and Radio Channels ISSUE1.4

HUAWEI TECHNOLOGIES CO., LTD.

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OMF000001 Um interface and radio channels

ISSUE1.4

HUAWEI TECHNOLOGIES CO., LTD. Page 2All rights reserved

Chapter 1 OverviewChapter 1 Overview

Chapter 2 Chapter 2 Processing of vProcessing of v

oice signaloice signal

Chapter 3 Radio channelChapter 3 Radio channel


Radio Interface

Another MSC

HLR/AUC/LR

SMC

PSTN ISDN

OMC

MS

Um interfaceMS

Um

Um

A-bis interface

BSCMSC/VLR

A interface

MAP interface

BTS

MSC


Communication management (CM)Communication management (CM)

Radio resources management (RR)Radio resources management (RR)

Mobility and security management (MM)

Mobility and security management (MM)

Integrated managementIntegrated management

TCH0 TCH1 TCH2 。。 SACCH 。。 TCH23 IDLTCH0 TCH1 TCH2 。。 SACCH 。。 TCH23 IDL

MultiframePhysical link layer (L1)

Data link layer (L2)

Network application layer (L3)

Hierarchical Structure of Um Interface

RACH BCCH AGCH/PCH SDCCH SACCH TCH FACCH


Radio Access Technology

Time

FDMA

Frequency

TDMATime

Frequency

CDMA

Frequency

Time

Code







Voice A/DA/D8KHz， 13bit Speech

codingSpeech coding

SegmentationSegmentation

20ms

13kbit/sChannel codingChannel coding

InterleavingInterleaving Burst formattingBurst formattingEncryptionEncryption

22.8kbit/s

ModulationModulation

33.8kbit/s

Transmission

Voice Signal Processing


Speech Coding

The coding mode is called Regular Pulse Excited-Long Term

Prediction (RPE-LTP). It works as follow: 8KHZ of sampling is

performed first, then divided into frames with 20ms; every frame has

4 sub-frames; the duration of every sub-frame is 5ms; and the pure

bit rate is 13kbit/s.


Block coderBlock coder

Excited coder

Excited coder

50bit

+3 *2+4

132bit

78bit

456bit

Channel Coding


Interleaving

1 2 3 4 5 6 7 8 ... ... 452 453 454 455 4561 2 3 4 5 6 7 8 ... ... 452 453 454 455 456

B

8

16

.

.

.

456

8

16

.

.

.

456

2

10

.

.

.

450

2

10

.

.

.

450

6

14

.

.

.

454

6

14

.

.

.

454

1

9

.

.

.

449

1

9

.

.

.

449

4

12

.

.

.

452

4

12

.

.

.

452

7

15

.

.

.

455

7

15

.

.

.

455

3

11

.

.

.

451

3

11

.

.

.

451

5

13

.

.

.

453

5

13

.

.

.

453

.... ....

B0 B1 B2 B3 B4 B5 B6 B7

{A4,B0} {A5,B1} {A6,B2} {A7,B3} {B4,C0} {B5,C1} {B6,C2} {B7,C3}{A4,B0} {A5,B1} {A6,B2} {A7,B3} {B4,C0} {B5,C1} {B6,C2} {B7,C3}

First interleaving:

Second interleaving:


33 5757 11 2626 11 5757 33

Voice Burst


Transmission delay t


TA

The mobile phone should

send the signal in advance!!

Timing Advance (TA)


Timing Advance (TA)



TA

The mobile phone should

send the signal in advance!!


Frequency Hopping

Frequency

f 0

Frame

f 1

f 2

f 3

f 4

Time


Prolong battery life and reduce interference

DTX

DTX: Discontinuous Transmission

Shut off the transmission at voice intervals;

Only transmit SID frames’

The transcoder at the RX terminal produces comfortable noise.

VAD: Voice Activity Detection

Implemented by the transcoder.


Power Control

Prolong battery life

Reduce network interference

Include both uplink power control and downlink power control

Level and quality are taken into account

BSC is the final adjudicator

BCCH Carrier is not involved in power control.

Time

Signal level

Target level value:e.g. -85 dm







Frequency

200kHz

15/26ms

BP

Slit

Time

Frame and Channel


0 1 2 3 2044 2045 2046 2047

0 1 2 3 48 49 5047

0 1 24 25

0 1 24 25 1 49 500

0 1 4 5 762 3

TB3

TB3

GP8.25 TB: Tail bit

TB3

TB3

GP8.25

GP: Guard periodTB3

TB3

GP8.25

TB3

TB3 GP 68.25

58 information bits 26 training sequences 58 information bits

Constant bit 142

Information bit 39 Extended training sequence 64Information bit 39

Synchronous sequence 41 Information bit 36

Normal burst (NB)

Frequency correction burst (FB)

Synchronous burst (SB)

Access burst (AB)

1 hyper frame=2048 super-frames=2715648TDMA frames (3 hours, 28 minutes, 53 seconds and 760 milliseconds)

1 super-frame=1326TDMA frames (6.12 seconds)

1 multiframe=26TDMA frames (120ms) 1 multiframe=51TDMA frames (3060/13ms)

1TDMA frame=8 timeslots (120/26=4.615ms)

1 timeslot=156.25 bit duration (15/26=0.577ms)(1 bit duration: 48/13=3.68us)

BCCHCCCHSDCCH

TCHSACCH/TFACCH

Frame


8bit 41 synchronous bits

36 encrypted bits 3bit 68.25bit

Tail bit Tail bit Guard intervalData

• Access burst (AB): Used in MS initial access

Guard interval

3bit 142bit 3bit 8.25bit

Tail bit Tail bitData

• Frequency correction burst (FB): Used in frequency synchronization between MS and BTS

3bit 39 encrypted bits

39 encrypted bits

3bit 8.25bit

Tail bit Tail bit Guard intervalDataData

64 synchronous bits

• Synchronous burst (SB): Used in timing synchronization between MS and BTS

Burst


3bit 142 modulation bits 3bit 8.25bit

Tail bit Tail bit Guard interval

• Dummy burst (DB): Used in transmission of filling frames by BTS at timeslots when there is no information delivered

Burst

3bit 57 encrypted bits 57 encrypted bits 3bit 8.25bit

Tail bit Tail bit Guard intervalDataData

26bit1 1

Training sequence

Frame stealing

flag

• Normal burst (NB): Used to carry the information of the traffic channel and the control channel except for RACH


Broadcast control channel (BCCH) Control channel

Common control channel (CCCH)

Voice channel(TCH)

FCH SCH BCCH(system information)

TCH/FAGCH RACH SDCCH FACCH

SACCH

TCH/H

TCH/9.6FTCH/ 4.8F, HTCH/ 2.4F, H

PCH

Common channel (CCH)

Dedicated channel (DCH)

Logical channel

Logical Channel Type

GSM900 and DCS1800 have the same logical channel categor

y


FCCH

SCH

BCCH

PCH

AGCH

BCCH

CCCH

Common Channel

SDCCH

SACCH

FACCH

TCH/F

TCH/H

DCCH

TCH

Dedicated Channel

Downlink Logical Channel


RACH CCCH

Common channel

SDCCH

SACCH

FACCH

TCH/F

TCH/H

DCCH

TCH

Dedicated channel

Uplink Logical Channel


Use of Logical Channels

Search for frequency correction burst

Search for synchronization sequence

Read system information

Listen paging message

Send access burst

Wait for signaling channel allocation

Call setup

Assign traffic channel

Conversation

Call release

FCCH

SCH

BCCH

PCH

RACH

AGCH

SDCCH

SDCCH

TCH

FACCH

idle mode

“off” state

dedicated mode

idle mode


26-frame multiframeTCH/F+FACCH/F+SACCH/TF (full-rate TCH)

TCH/H+FACCH/H+SACCH/TH (half-rate TCH)

51-frames multiframeFCCH+SCH+BCCH+CCCH (main BCCH)

FCCH+SCH+BCCH+CCCH+SDCCH/4+SACCH/C4 (combined B

CCH)

BCCH+CCCH (extended BCCH)

SDCCH/8+SACCH/C8 (main SDCCH)

Physical Combination of Logical Channel


Structure of Main BCCH

1 multi-frame (51TDMA Frames) 235.38ms Downlink

Group Group1 Group2

Group3,4

(same as

Group2)

Grpup5

Channel F S BX4 CX4 F S CX4 CX4 …… F S CX4 CX4 I

Frame

Number0 1 2-5 6-9 10 11 12-15 16-19 20-39 40 41 42-45 46-49 50

1 multi-frame (51TDMA Frames) 235.38ms Uplink

Channel R R R R R R R R R R R R R R……R R R R R

Frame

Number0 1 2 3 4 5 6 7 8 9 10 11 12 13-46 47 48 49 50

F:FCCH; S:SCH; B:BCCH; C:CCCH; I:IDLE; R:RACH


Structure of Combined BCCH1 multi-frame (51TDMA Frames) 235.38ms Downlink

Group Group1 Group2 Group3 Group4 Grpup5

Channel F SB×

4

C×

4F S

C×

4

C×

4F S

D0

×4

D1

×4F S

D2

×4

D3

×4F S

A0

×4

A1

×4I

Channel F SB×

4

C×

4F S

C×

4

C×

4F S

D0

×4

D1

×4F S

D2

×4

D3

×4F S

A2

×4

A3

×4I

Frame

Number0 1 2-5 6-9 10 11

12-

15

16-

1920 21

22-

25

26-

2930 31

32-

35

36-

3940 41

42-

45

46-

4950


Channel D3×4 R R A2×4 A3×4 R……R D0×4 D1×4 R R D2×4

Channel D0×4 R R A0×4 A1×4 R……R D0×4 D1×4 R R D2×4

Frame Number 0-3 4 5 6-9 10-13 14-36 37-40 41-44 45 46 47-50



Structure of Logical Channel Combination Frame-Main SDCCH

1 multi-frame (51TDMA Frames) 235.38ms Downlink

Channel D0×4 D1×4 D2×4 D3×4 D4×4 D5×4 D6×4 D7×4 A0×4 A1×4 A2×4 A3×4 I I I

Channel D0×4 D1×4 D2×4 D3×4 D4×4 D5×4 D6×4 D7×4 A4×4 A5×4 A6×4 A7×4 I I I

Frame Number 0-3 4-7 8-11 12-15 16-19 20-23 24-27 28-31 32-35 36-39 40-43 44-47 48 49 50


Channel A5×4 A6×4 A7×4 I I I D0×4D1×

4D2×4 D3×4 D4×4 D5×4 D6×4 D7×4 A0×4

Channel A1×4 A2×4 A3×4 I I I D0×4D1×

4D2×4 D3×4 D4×4 D5×4 D6×4 D7×4 A4×4

Frame

Number0-3 4-7 8-11 12 13 14 15-18

19-

2223-26 27-30 31-34 35-38 39-42 43-46 47-50



Structure of Logical Channel Combination Frame-TCH

T:TCH; I:IDLE

1 multi-frame (26TDMA Frames) 120ms

Channel T T T T T T T T T T T……T T T T T I

Frame Number 0 1 2 3 4 5 6 7 8 9 10－ 20 21 22 23 24 25


PCH RACHAGCH

Downlink CCCH Uplink CCCH

How to determine the total CCCH resources of the cell? How to

allocate AGCH and PCH reasonably?

Configuration of Common Control Channel


CCCH Grouping

The GSM system supports various kinds of channel combinations

(GPRS not taken into account), in which the main BCCH, extended

BCCH, combined BCCH, and the BCCH+CBCH combination

contain the CCCH, i.e. all of the four combinations support the MS

access. The MS are distributed to different CCCH groups based on

this fact.


CCCH Grouping

The GSM specifies that the CCCH can be mapped to timeslots 0, 2,

4 and 6 but the extended BCCH combination can only be mapped to

timeslots 2, 4 and 6 because it does not contain FCCH and SCH.

Therefore, all MS synchronize with the base station at timeslot 0 and

access the network via different CCCH.


Paging Group

The GSM system supports a maximum of 99=81 paging groups.

the MS can be divided into 81 sub-groups at most from the opinion

of the paging group. No matter what combination mode is adopted,

the number of blocks used for paging in every 51 multi-frame does

not exceed 9. The system enables the 51 multi-frame to cycle

again , with a quantity of “BS-PA-MFRAMS” (number of frames of

the same paging) of 51 multi-frames as a period.


Paging Group

In GSM terms, the paging block in any 51 multiframe is called a

paging super-group. Therefore, the number of paging super-frames

in the system is the “number of frames of the same paging”. The

number of paging groups in each super-group is 9 or 3 – “number of

access granted reserved blocks”.


Calculation of CCCH and Paging Group

CCCH group number of MS=[(IMSI mod 1000) mod (BS_CC_CHAN

S x N)] div N

Paging group number of MS=[(IMSI mod 1000) mod (BS_CC_CHAN

S x N)] mod N

In the formula:

N = Number of paging groups x BS-PA-MFRAMS

IMSI = IMSI number of the mobile phone

mod = Modulo calculation

div = Divide exactly


Questions

What’s the rate of voice coding ?

What are the advantages of discontinuous

transmission (DTX)?

What types of logical channels are there?

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OMF000001 Um Interface and Radio Channels ISSUE1.4

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