05 um interface and radio channels issue2.0

8/12/2019 05 Um Interface and Radio Channels ISSUE2.0

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Internal

OMF000001 Um Interface

and Radio Channels

ISSUE2.0




Chapter 1 Overview

Chapter 2 Processing of

voice signal

Chapter 3 Radio channel




Radio Interface

Another MSC

HLR/AUC/LR

SMC

PSTN

ISDN

OMC

MS

Um interfaceMS

Um

Um

A-bis

interface

BSC

A interface

MAP interface

BTS

MSC




Radio Access TechnologyTime

FDMA

Frequency

TDMATime

Frequency

CDMA

Frequency

Time

Code


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Chapter 1 Overview

Chapter 2 Processing of

voice signal

Chapter 3 Radio channel




Voice A/D8KHz 13bit Speech

coding

Segme

ntation

20ms

13kbit/sChannel coding

Interleaving Burst formattingEncryption

22.8kbit/s

Modulation

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.




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

B

8

16.

.

.

456

2

10.

.

.

450

6

14.

.

.

454

1

9.

.

.

449

4

12.

.

.

452

7

15.

.

.

455

3

11.

.

.

451

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}

First interleaving:

Second interleaving:

Interleaving




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.




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.

Prolong

battery life

and reduce

interference




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 GP8.25TB: 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/T

FACCH

Frame




Frame0 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 bitTB3

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




8bit41 synchronous

bits

36 encrypted

bits 3bit 68.25bit

Tail bit Tail bitGuard interval

Data

• Access b urst (AB): Used in MS ini t ial access

Guard interval

3bit 142bit 3bit 8.25bit

Tail bit Tail bitData

• Frequency correct ion b urst (FB): Used in frequency sy nch ronizat ionbetween MS and BTS

3bit 39 encrypted

bits

39 encrypted

bits3bit 8.25bit

Tail bit Tail bit Guard intervalDataData

64 synchronous bits

• Synchron ous b urst (SB): Used in t iming sy nch ronization b etween MS

and BTS

Burst




3bit 142 modulation bits 3bit 8.25bit

Tail bit Tail bit Guard interval

• Dummy bu rst (DB): Used in transm ission o f f i l ling frames byBTS at t imeslots when there is no inform at ion del ivered

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 c arry the informat ion of the traf f ic c hannel

and the control channel except for RACH




Broadcast control channel

(BCCH) Control channelCommon control channel

(CCCH)

Voice channel

(TCH)

FCH SCH BCCH

(system information)

TCH/FAGCH RACH SDCCH FACCH

SACCH

TCH/HPCH

Common channel

(CCH)

Dedicated channel

(DCH)

Logical channel

Logical Channel Type

GSM900 and DCS1800 have the same logical channelcategory




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

TCHFACCH

idle mode

“off” state

dedicated

mode

idle mode




26-frame multi-frame

TCH/F+SACCH/F (full-rate TCH)

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

51-frames multi-frame

FCCH+SCH+BCCH+CCCH (main BCCH)

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

BCCH)

BCCH+CCCH (extended BCCH)

SDCCH/8+SACCH/8 (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

Number 0 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

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

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

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




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 S T……T T I

Frame Number 0 1 2 3 4 5 6 7 8 9 10 11 12 13…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”.




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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Thank You

05 um interface and radio channels issue2.0

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