where is the TRAU practically placed???

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

krg - 17 Apr 2006 13:29 GMT

Hi,
Just wanted to know as to where is the TRAU(Transcoding and Rate
Adaptation Unit) placed in practical implementations. From what I know,
it is placed in the proximity of the MSC, but guidelines depict[not
dictate but depict] as to it being placed near or as part of the BSC.
If anybody could help me out by clarifying this. Thanks in
advance.

Care & Take Care.

Reply to this Message

R-Guy - 22 Apr 2006 06:05 GMT

It is usually part of the BSC.

> Hi,
> Just wanted to know as to where is the TRAU(Transcoding and Rate
[quoted text clipped - 5 lines]
>
> Care & Take Care.

Reply to this Message

krg - 22 Apr 2006 11:09 GMT

Thanks R-Guy. But i would like to keep this alive for a li'l more long.
What I meant when i said "From what I know", is that some
implementations I have
worked on have the TRAU sitting cosy in an MSC, and not the BSC. Now
why???
I couldn't work out the pros and cons of this situation. If somebody or
maybe
R-Guy can point out himself. If the specs really don't have some
guideline, then
it must not be of that significance technologically or either
commercially, but it
seems as demands are increasing, it suddenly seems to be a "good
practice" to
place it in the MSC.

Care & Take Care.

> It is usually part of the BSC.
>
[quoted text clipped - 7 lines]
> >
> > Care & Take Care.

Reply to this Message

Saurabh - 25 Apr 2006 12:24 GMT

Dear krg,

I hope this will help you to understand the TRAU.

Transcoding Rate and Adaptation Unit (TRAU)

It will convert 64 kbps PCM voice from transmission to a mobile
station. It will also convert 13 kbps or 8 kbps from mobile station
back to 64 kbps required for MSC.
TRAU is not used for data communication (used only for voice
communication).
TRAU can be used between the BSC and MSC or between the BTS and BSC. If
TRAU is with the MSC, the leased line costs between MSC and BSC can be
reduced significantly.
TRAU normally resides on the MSC side.

Aloha,
Saurabh

> Hi,
> Just wanted to know as to where is the TRAU(Transcoding and Rate
[quoted text clipped - 5 lines]
>
> Care & Take Care.

Reply to this Message

krg - 26 Apr 2006 10:54 GMT

hi,
and thanks saurabh. well i too had this cost and bandwidth thing
going on
in my mind, but just needed some affiliation. by the way, what actually
gave rise to this question is that in case of AMR, the codec change
indication is sent all the way to the TRAU, if it be at MSC, then so be
it. consider the latency. anyway. thanks.

Care & Take Care,

Reply to this Message

Saurabh - 26 Apr 2006 11:14 GMT

Hi krg,

>From the handset side the configuration information (supporting status)

is send to network side. Whether the handset is supporting
HR/FR/EFR/AMR. This information shows the compatibility to the network.

I hope the following will help you

AMR has been designed so that the bit rate can be changed every 20ms.
When reception between the user and the network is good, a lower bit
rate can be used, as there is less chance of errors or missed frames.
However, when the user moves to an area with worse reception, the bit
rate can be progressively increased so that errors will not cause
severe degradation.
The AMR vocoder has the following characteristics:

1. Provides 12 encoding types from 4.75 Kbps to 12.2 Kbps
2. Adapts to network and sound conditions
3. Robust design
4. Background comfort mode

AMR provides eight different vocoders, each with a different bit rate.
Three of the vocoders provided in AMR are used in today's networks:
EFR (12.2 Kbps), IS-641 (7.4 Kbps), and PDC-EFR (6.7 Kbps). The other
five vocoders have been designed for different balances of quality and
bandwidth. 'Table 1' lists the bit rates of the vocoders used in
AMR.

· AMR-WB: AMR-Wideband is closely based on standard AMR, except that
the bit rates used are about twice as high, for better quality
transmission. The bit rates range from 6.6 to 23.85 Kbps. The wideband
implementation of AMR also has a sampling rate of 16000Hz, which is
twice as high as used in standard AMR.

· SMV: Selectable Mode Vocoder is similar to AMR in that SMV has
multiple bit rates and can switch between them during a call. However,
SMV only has four modes: half as many as AMR. SMV's bit rates range
from 8.12 to 3.95 Kbps.

GSM-AMR is a standard adapted by the 3rd Generation Partnership Project
(3GPP). It is an Adaptive Multi Rate-Narrow Band (AMR-NB) speech codec.
This vocoder is used mainly in 3rd generation mobile telephony devices
to compress toll-quality speech at 8000 samples/second. GAO's GSM-AMR
codec has eight basic bit rates, 12.2, 10.2, 7.95, 7.40, 6.70, 5.90,
5.15 and 4.75 Kbit/s. GAO's algorithm utilizes the Algebraic Code
Excited Linear Prediction (ACELP) technique for all bit rates.

Features
·    Adaptive Multi-Rate ranges from 4.75 kbit/s to 12.2 kbit/s.
·    Optimized C or Assembly code.
·    Low program and data memory requirements.

Aloha,
Saurabh

Reply to this Message