07 mn1780eu09mn 0002 trau architecture

TRAU Architecture Siemens

MN1780EU09MN_0002 © 2001 Siemens AG

1

Contents

1 Functions 3

1.1 Traffic Channels 6

1.2 Other Channels 7

2 TRAU Modules 13

2.1 BSC Interface Board 16

2.2 MSC Interface Board 18

2.3 Transcoder and Rate Adapter Board 19

3 Rack Configuration 21

3.1 TRAU Rack with 4 TRAUE 22

3.2 High Capacity TRAU 26

4 Exercises 31

TRAU Architecture

Siemens TRAU Architecture

MN1780EU09MN_0002

© 2001 Siemens AG

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3

1 Functions


MN1780EU09MN_0002

© 2001 Siemens AG

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The Transcoding and Rate Adapter Unit TRAU is located between BSC and MSC featuring the (standardized) A interface.

The TRAU performs the following functions:

� Transcoding (de-/compression) of speech,

� Rate adaptation of data,

� Handling multi slot connections (for HSCSD).

Channels not carrying GSM traffic pass through the TRAU transparently:

� CCSS#7 signaling,

� Operation and Maintenance Link OMAL (between OMC and BSC) and

� Nailed-up connections NUC.

BSC MSCMSC

interface

LMT

TRAU

BSC

interface

Transcoder

Boards

T

Asub

PCMS

A

PCMA

Fig. 1 TRAU architecture



5

For each traffic channel, the TRAU adapts the different transmission rates for speech and data calls on the radio side (16 kbit/s sub slots) to the standardized 64 kbit/s transmission rate used by the MSC, i.e. the circuit-switched core network. It also maps between the different speech coding algorithms used within the fixed network and on the radio interface.

The TRAU handles up to 120 channels at 16 kbit/s submultiplexed on the BSC side (Asub interface) and the same number of channels, transcoded at 64 kbit/s, on the MSC side (A interface).

The TRAU is connected to the MSC via a maximum number of four PCMA links.

The TRAU is connected to the BSC via one PCMS link.

Due to its submultiplexing, the TRAU provides an optimum use of PCM links and reduces line costs for the network operator. Thus, the TRAU is usually located near the MSC although being part of BSS.

SBS

BSC

TRAU

0

TRAU

1

TRAU

2

TRAU

19

.

.

.

MSC

120 Traffic

channels at

64 kbit/s

Asub

(PCMS)

A

(PCMA)

120 Traffic

channels at

13+3 kbit/s

Fig. 2 TRAU functions


MN1780EU09MN_0002

© 2001 Siemens AG

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1.1 Traffic Channels

For (full rate) speech calls the TRAU transcodes the 64 kbit/s on the A interface into 13 kbit/s + 3 kbit/s on the Asub interface (and vice versa).

Adaptation is also required for data calls. Possible (single slot) data rates are e.g. 2.4 kbit/s, 4.8 kbit/s, 9.6 kbit/s and 14.4 kbit/s.

Speech traffic which requires a 64 kbit/s time slot on the A interface is compressed into one 16 kbit/s sub slot on the Asub interface.

(Circuit-switched) data traffic requires a single time slot on PCMA and up to four sub slots on PCMS (depending on the type of multislot connection).

The transmission to the BSC (Asub interface) is carried out by one PCM link, whereas the transmission to the MSC (A interface) requires up to 4 PCM links.

SBS

BSC TRAU-0 MSC

Asub A

64 kbit/s

e.g., Slot 12

e.g., Slot 12

Call 1 (13+3 kbit/s)




Call 1

Call 2

Call 3

Call 4

Fig. 3 Transcoding of speech / rate adaption of data



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1.2 Other Channels

LAPD Signaling Channel:

On the Asub interface, one 64 kbit/s timeslot is dedicated to provide communication (O&M signaling) between BSC and TRAU by means of LAPD protocol ("LPDLS"). Correspondingly, four time slots are idle on the A interface.

Note: For each TRAU, one LPDLS link (64 kbit/s) is required.

BSC

TRAU

0

TRAU

1

TRAU

2

MSC

LPDLS-0

LPDLS-1

LPDLS-2

Asub A

LAPD e.g.

in TS 31

4 TS remain

idle

SBS

Fig. 4 LAPD signaling


MN1780EU09MN_0002

© 2001 Siemens AG

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OMAL Signaling Channel:

If the OMC is connected to the BSC via the MSC, a 64 kbit/s timeslot ("OMAL") is dedicated on the Asub and the A interface for the communication between the OMC and the BSC. Since the TRAU is transparent for OMAL, three timeslots on the A interface remain unused.

BSC

TRAU

0

TRAU

1

TRAU

2

MSC

Asub A

Idle

SBS

OMAL

SIEMENS

NIXDORF

SIEMENS

NIXDORF

OMAL

64 kbit/s

OMC for SBS

Fig. 5 OMAL signaling



9

CCSS7 Signaling Channel

On the A and Asub interfaces, one timeslot is dedicated for the communication between MSC and BSC. This communication link is based on the CCSS#7 protocol and carries the signaling information for the (circuit-switched) traffic channels.

The TRAU is transparent for the CCSS7 signaling, i.e. the CCSS7 time slot is the same on PCMA and PCMS. As for OMAL, three time slots on PCMA remain unused.

A BSC supports max. 20 TRAU with (together) 8 CCSS#7 links. Thus, not every TRAU carries a CCSS#7 link.

Note: The timeslot assignment on the A interface / Asub interface for the CCSS#7 signaling channel must match the time slot assignment on the CCSS7 timeslot in the EWSD.

SBS

BSC

TRAU

0

TRAU

1

TRAU

2

TRAU

19

.

.

.

MSC

Asub A

TCH

not used

CCSS7 e.g.

in TS 16CCSS7 e.g.

in TS 16

TCH

Fig. 6 CCSS7 signaling


MN1780EU09MN_0002

© 2001 Siemens AG

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Some Details on TRAU Matrices, Multislot Connections and Pooling

Several time slots on Um / Abis / Asub can be combined and finally mapped into a single 64 kbit/s time slot on A interface in a multi slot connection. Currently, mobile stations (and SBS) support the combination of max 4 (sub) slots on Um / Abis / Asub. In order to use multi slot connections in HSCSD, the time slots on the A interface (between MSC and TRAU) must be configured according to their capabilities as belonging to a certain pool. Example: "circuit pool no. 10" means that TSLA can carry Full Rate, Enhanced Full Rate, FR data up to 9.6 kbit/s, Half Rate, Half Rate data up to 6 kbit/s as well as HSCSD with max 2 x FR data).

The most commonly used time slot distribution between PCMS and PCMA is defined in the BSC database as "not_compatible_with_cross_connect". The sorting rules are:

� All channels related to multi slot connections (from all PCMA) with max 4 TSL/connection are assigned to the first time slots on Asub.

� All channels related to multi slot connections (from all PCMA) with max 2 TSL/connection are assigned next on Asub.

� All ordinary channels are assigned in an optimal order without wasting space on Asub.

A simplified rule of thumb is:

� For each MSL with max 4/2 TSL per connection, 3/1 TSLA are configured as "no_def".

The time slots with "no_def" don't have to be located on the same PCMA.

Note: TSLA, which cannot be assigned to a TSLS, must be configured as "no_def".

For every change in multi slot configuration, the matrix is re-arranged for the (new) optimal distribution. Thus, every modification may change the time slot distribution.

Nailed-up connections are available in BSC and TRAU. Due to hardware limitations, however, NUC through TRAU require that time slots on PCMA and PCMS are identical giving an auxiliary sorting rule.

The following example shows the usage of time slots on PCMS as well as PCMA#0 and PCMA#1 for a TRAU (matrix 1) with HSCSD multislot connections, nailed-up connections, OMAL and CCSS#7 (for clarity, PCMA#3 has been omitted).



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Example: "Not compatible with cross-connect" (matrix type 1)

TS no. PCMS (sub slots) PCMA#0 PCMA#1 PCMA#2

1 0-10 0-10 0-10 0-10 1 1 1

2 0-5 0-5 2-15 2-15 2 2 2

3 0-1 1-1 2-1 3-1 3 3 3

4 0-2 1-2 2-2 3-2 4 4 4

5 0-3 1-3 2-3 3-3 MSL x 2 5 5

6 0-4 1-4 2-4 3-4 6 6 6

7 1-5 2-5 3-5 0-6 7 7 7

8 1-6 2-6 3-6 0-7 8 8 8

9 1-7 2-7 3-7 0-8 9 9 9

10 1-8 2-8 3-8 0-9 MSL x 4 10 10

11 1-9 2-9 3-9 1-10 11 11 11

12 2-10 3-10 0-11 1-11 12 12 12

13 2-11 3-11 0-12 1-12 13 13 13

14 2-12 3-12 0-13 1-13 14 14 14

15 2-13 3-13 0-14 1-14 15 15 MSL x 2

16 CCSS#7 CCSS#7 16 16

17 2-14 3-14 0-15 1-15 17 17 17

18 3-15 1-16 2-16 3-16 18 18 18

19 0-17 1-17 2-17 3-17 19 19 19

20 0-18 1-18 2-18 3-18 20 20 20

21 0-19 1-19 2-19 3-19 21 21 21

22 0-20 1-20 2-20 3-20 22 22 22

23 0-21 1-21 2-21 3-21 23 23 23

24 NUC NUC 24 24

25 0-22 1-22 2-22 3-22 25 25 25

26 0-23 1-23 2-23 3-23 26 26 26

27 1-24 2-24 3-24 0-25 27 not used not used

28 1-25 2-25 3-25 0-26 not used not used not used

29 1-26 2-26 3-26 0-27 not used not used not used

30 OMAL OMAL not used not used

31 LPDLS not used not used not used


MN1780EU09MN_0002

© 2001 Siemens AG

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13

2 TRAU Modules


MN1780EU09MN_0002

© 2001 Siemens AG

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The different TRAU modules are shown in the figure below.

BSCI-1

BSCI-0

MSCI-1

MSCI-0

TRAC-0

TRAC-4

TRAC-5Local-Control

4 PCM 30

4 x 30 TCH

Interface

to LMT

1 PCM 30

120 TCH

.

.

.

Fig. 7 TRAU internal architecture



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The following table contains the TRAU modules:

Abbreviation Full Module Name

BSCI BSC Interface Board

MSCI MSC Interface Board

TRAC Transcoder and Rate Adapter Board

In earlier variants of TRAU hardware, two dedicated power supply modules TPWR were used in the TRAU shelf. By now, all modules have their power supplies integrated "on-board".


MN1780EU09MN_0002

© 2001 Siemens AG

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2.1 BSC Interface Board

The BSC Interface Board BSCI has the following tasks:

� It houses the main controller (local control) of the TRAU, which is responsible for hardware configuration, fault management, performance measurement collection, database administration and transcoder matrix management.

� Interface from TRAC towards the BSC.

� Multiplexes in Downlink direction the signals generated by each TRAC board in order to build the whole 16 kbit/s TCH structure to be sent to the BSC. In the Uplink direction it transmits (towards the TRAC) the whole TCH structure coming from the BSC.

� Transparent for CCSS7 signaling channels (64 kbit/s), OMAL signaling channels (64 kbit/s) and NUC.

� Provides a communication link between the BSC and the TRAU controller (LAPD link).

� Provides a line clock regenerator, which is implemented as a Phase Locked Loop (PLL) voltage-controlled oscillator that can lock either to one of the PCM lines coming from the MSC or to one of the PCM lines coming from the BSC.

� The TRAU software is stored on flash EPROM, and is therefore also available after a power failure.

� Interface to LMT.

� DC/DC converter on board.

� Is protected by 1:1 redundancy (hot standby).



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TRAU

LMT

BSCI-1

Local Control

BSCI-0

Clock

Local Control

BSC

T interface

PCMS

Fig. 8 BSC interface board


MN1780EU09MN_0002

© 2001 Siemens AG

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2.2 MSC Interface Board

The MSC Interface Board MSCI performs the following functions:

� Multiplexes in uplink direction the signals generated by each TRAC board in order to build the whole 64 kbit/s TCH structure to be sent to the MSC. In the downlink direction it transmits the whole TCH structure coming from the MSC to the TRAC boards.

� Processes the LAPD protocol of the BSC control link.

� Sends to the BSCI the messages received from the BSC by using a dedicated serial communication link and receives the messages from BSCI, which are to be inserted in the link towards the BSC.


� Is protected by 1:1 redundancy (hot standby).

BSCI-1

BSCI-0

MSCI-1

MSCI-0

TRAC-0

TRAC-4

TRAC-5Local-Control

4 PCM 30

4 x 30 TCH

Interface

to LMT

1 PCM 30

120 TCH

.

.

.

Fig. 9 MSCI board



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2.3 Transcoder and Rate Adapter Board

The Transcoder and Rate Adapter Circuit TRAC performs the following functions:

� Processes 24 TRAU frames for 24 traffic channels.

� Operates with speech and data on each channel, either at full or at half rate (Transcoder and Rate Adapter function).

� Handles multi slot connections (for HSCSD).

� Performs Volume Control to compensate for possible losses of volume.

� Communicates with the TRAU controller on the BSCI board using a serial communication link. The transferred information belongs to software downloading, configuration and maintenance messages.

� Voice Activity Detection (VAD) / Discontinuous Transmission (DTX):

The discontinuous transmission DTX and its functions voice activity detection VAD and comfort noise insertion CNI for are specified for minimizing the power consumption of the MS and, at the same time, for reducing the interference level on the radio interface. During a normal conversation, the participants speak in turns so that, on average, each transmission direction is occupied only about 50% of the time. If transmission is switched on only for those frames that contain speech and is switched off during all other intervals then the power consumption in the MS is reduced considerably and the interference level in the network is reduced.

� Two different transcoding arrangements ("matrices") can be chosen (BSC database, defining the relation between the channels on A and Asub interface.


� Is protected by n:1 redundancy (n=1...5).

BSCI-1

BSCI-0

MSCI-1

MSCI-0

TRAC-0

TRAC-4

TRAC-5Local-Control

4 PCM 30

4 x 30 TCH

Interface

to LMT

1 PCM 30

120 TCH

.

.

.

Fig. 10 TRAC boards


MN1780EU09MN_0002

© 2001 Siemens AG

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21

3 Rack Configuration


MN1780EU09MN_0002

© 2001 Siemens AG

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3.1 TRAU Rack with 4 TRAUE

In one rack, up to four TRAU shelves can be housed.

For reliability, the BSCI and MSCI are duplicated (1:1 redundancy), whereas the TRAC boards are protected by one spare board (n:1 redundancy, n=1, ... , 5).

Module Redundancy Quantity Numbering

BSCI 1:1 2 BSCI-0,-1

MSCI 1:1 2 MSCI-0,-1

TRAC n:1 minimum 1:1

maximum 5:1

TRAC-0,-1

TRAC-0,-1,-2,-3,-4,-5

(PWRS) 1:1 2 TPWR-0,-1

In earlier TRAU hardware releases, the TRAU shelf also housed two separate power supply modules TPWR-0/1:

� input voltage: -48 V

� output voltage: +5.3 V and +12.3 V

The two power supplies TPWR-0 and TPWR-1 provide power to the following modules:

� TPWR-0 is responsible for BSCI-0, MSCI-0 and all TRAC boards.

� TPWR-1 is responsible for BSCI-1, MSCI-1 and all TRAC boards.

NOTE

The latest TRAU hardware (MSCIV2, BSCIV4, TRACV5 and "new" backplane) support operation without external power supply modules TPWR.

"Old" BSCI and MSCI boards can be (un)plugged only after TPWR has been powered "on(off)". "Old" TRAC modules can be un-/plugged while power is "on".

"New" modules are just plugged in (out) leading to "power on (off)" on the respective modules. (Note: before unplugging any module, it should be locked, i.e. taken out of service.)



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T

R

A

C

0

T

R

A

C

1

T

R

A

C

2

M

S

C

I

0

B

S

C

I

0

B

S

C

I

1

M

S

C

I

1

T

R

A

C

3

T

R

A

C

4

T

R

A

C

5

Fuse and Alarm Panel 0




TRAU-0

TRAU-1

TRAU-2

TRAU-3

Fig. 11 TRAU rack



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T

P

W

R

0

T

R

A

C

0

T

R

A

C

1

T

R

A

C

2

M

S

C

I

0

B

S

C

I

0

B

S

C

I

1

M

S

C

I

1

T

R

A

C

3

T

R

A

C

4

T

R

A

C

5

T

P

W

R

1

Fig. 12 DC power distribution in the (old) TRAU shelf


MN1780EU09MN_0002

© 2001 Siemens AG

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3.2 High Capacity TRAU

3.2.1 Basics

The features of the new TRAU rack are:

� New rack housing max 8 TRAUE instead of 4 TRAUE (same footprint and volume)

� New back plane capable to support 240 TCHs (2 TRAUE per sub rack)

� Reuse of the MSCI and BSCI boards

� TRAC V7 only (current TRAC V5 not foreseen)

Thus, the capacity for a TRAU rack is doubled (960 TCH instead of 480 TCH).

3.2.2 Functional Description

A new TRAU rack (able to manage up to 960 TCH) doubles the capacity of the current TRAU rack (480 TCH).

The elements, which are "re-used", comprise

� (most of) the current TRAU rack mechanic,

� (most of) the current rack cabling,

� the current LEDs/lamps signaling philosophy.

The main changes are related to

� a new back panel (2 TRAUE sharing the same sub rack, capacity: 240 TCH),

� a new top rack fans tray unit.

Backward compatibility versus the current BSCI and MSCI cards is maintained:

� in one sub rack two TRAUE are located,

� each TRAUE is composed of:

2 (current) BSCI cards ("BSCIV4"),

2 (current) MSCI cards ("MSCIV2") and

6 new TRACV7 cards.



27

TRAUE

Fig. 13 TRAU High-Capacity Rack


MN1780EU09MN_0002

© 2001 Siemens AG

28

3.2.3 Fan Alarm

With the fans tray, a fan alarm is introduced (i.e. additional attribute beside "door_open", sense point is on BSCI):

� ENVATRAUE of the first TRAUE (top left shelf) is reserved for "door_open" alarm,

� ENVATRAUE of the second TRAUE (top right) is reserved for "fan_alarm",

The fan alarm is created by the operator (on RC or LMT). Thus, for a correct "fan_alarm" reporting, the two upper TRAUEs are required (otherwise, only the "door_open" alarm is reported).

3.2.4 Man-Machine Interface

The range for the Shelf Number attribute (TRAUE object) changes to 0..7 (from 0..3).

There are no changes on the RC GUI because only TRAUE are shown (10 boards: 6 TRAC, 2 BSCI, 2 MSCI) and the boards do not change their relative position within the shelf.

Fig. 14 "Open Door" and "Fan" Alarm for new TRAU Rack (Schematic)



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TRAUE

Fig. 15 Layout for new TRAU High-Capacity Rack (Schematic)



31

4 Exercises



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� Name the major functions of the TRAU.

� Name the TRAU modules and their functions.

� If MSCI-0 breaks down, is the entire TRAU out of service?

07 mn1780eu09mn 0002 trau architecture

Documents

pcm lines

multi slot

rate adapter

time slot

tch structure

half rate

time slot

lapd protocol