Forums

GSM Co-channel Interference Reduction

Started by hardheart August 20, 2010
Dear All,

I am doing a project of GSM baseband signal processing and now facing the
problem of how to reduce the cochannel and adjacent channel interference.
The main modules I have implemented are channel estimation and MLSE
equalizer, but I find the MLSE performance in terms of Bit Error Rate is
not good enough when interference exits.

I have three questions here.

1, some internet articles say that to use a noise whitening filter (not
implemented in my design yet) after matched filter (done already in my
design) can reduce interference. Is it a correct way or standard method for
mitigating GSM interference?

2, what is the typical anti-interference algorithm used in a commercial
mobile phone?

3, can anybody give a useful link on algorithms on anti-interference/noise
whitening filter?

hope somebody can help. Thank you.


Richard


On Fri, 20 Aug 2010 07:13:09 -0500, "hardheart"
<hardheartcn@n_o_s_p_a_m.yahoo.com.cn> wrote:

>Dear All, > >I am doing a project of GSM baseband signal processing and now facing the >problem of how to reduce the cochannel and adjacent channel interference. >The main modules I have implemented are channel estimation and MLSE >equalizer, but I find the MLSE performance in terms of Bit Error Rate is >not good enough when interference exits. > >I have three questions here. > >1, some internet articles say that to use a noise whitening filter (not >implemented in my design yet) after matched filter (done already in my >design) can reduce interference. Is it a correct way or standard method for >mitigating GSM interference? > >2, what is the typical anti-interference algorithm used in a commercial >mobile phone? > >3, can anybody give a useful link on algorithms on anti-interference/noise >whitening filter? > >hope somebody can help. Thank you. > > >Richard
For out-of-band or band edge interference, filtering is always a good strategy. For in-band interference it's a much more difficult problem. Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com

hardheart wrote:

> Dear All, > > I am doing a project of GSM baseband signal processing and now facing the > problem of how to reduce the cochannel and adjacent channel interference. > what is the typical anti-interference algorithm used in a commercial > mobile phone?
1. The adjacent channel is simply filtered out. 2. The nonlinear effects between the adjacent channels could be a big problem. Therefore the system is planned in such way so the adjacent channels are never used within a cluster or a group of neighboring clusters. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
On Aug 20, 8:13&#2013266080;am, "hardheart" <hardheartcn@n_o_s_p_a_m.yahoo.com.cn>
wrote:
> Dear All, > > I am doing a project of GSM baseband signal processing and now facing the > problem of how to reduce the cochannel and adjacent channel interference. > The main modules I have implemented are channel estimation and MLSE > equalizer, but I find the MLSE performance in terms of Bit Error Rate is > not good enough when interference exits. > > I have three questions here. > > 1, some internet articles say that to use a noise whitening filter (not > implemented in my design yet) after matched filter (done already in my > design) can reduce interference. Is it a correct way or standard method for > mitigating GSM interference? > > 2, what is the typical anti-interference algorithm used in a commercial > mobile phone? > > 3, can anybody give a useful link on algorithms on anti-interference/noise > whitening filter? > > hope somebody can help. Thank you. > > Richard
For co-channel interference, search on "GSM Multiuser Detection" -- there is plenty of info. It's not an easy problem though. John
Search SAIC. The technique for suppressing co-channel is quite mature. 

cfy30

>On Aug 20, 8:13=A0am, "hardheart" <hardheartcn@n_o_s_p_a_m.yahoo.com.cn> >wrote: >> Dear All, >> >> I am doing a project of GSM baseband signal processing and now facing
the
>> problem of how to reduce the cochannel and adjacent channel
interference.
>> The main modules I have implemented are channel estimation and MLSE >> equalizer, but I find the MLSE performance in terms of Bit Error Rate
is
>> not good enough when interference exits. >> >> I have three questions here. >> >> 1, some internet articles say that to use a noise whitening filter (not >> implemented in my design yet) after matched filter (done already in my >> design) can reduce interference. Is it a correct way or standard method
f=
>or >> mitigating GSM interference? >> >> 2, what is the typical anti-interference algorithm used in a commercial >> mobile phone? >> >> 3, can anybody give a useful link on algorithms on
anti-interference/nois=
>e >> whitening filter? >> >> hope somebody can help. Thank you. >> >> Richard > >For co-channel interference, search on "GSM Multiuser Detection" -- >there is plenty of info. It's not an easy problem though. > >John >
On Aug 20, 8:13&#2013266080;am, "hardheart" <hardheartcn@n_o_s_p_a_m.yahoo.com.cn>
wrote:
> Dear All, > > I am doing a project of GSM baseband signal processing and now facing the > problem of how to reduce the cochannel and adjacent channel interference. > The main modules I have implemented are channel estimation and MLSE > equalizer, but I find the MLSE performance in terms of Bit Error Rate is > not good enough when interference exits. > > I have three questions here. > > 1, some internet articles say that to use a noise whitening filter (not > implemented in my design yet) after matched filter (done already in my > design) can reduce interference. Is it a correct way or standard method for > mitigating GSM interference?
Yes. Because MLSE works best for white noise. If you do not have white noise, then it is not maximum likely any more.
> 2, what is the typical anti-interference algorithm used in a commercial > mobile phone?
For out-of-band interference, use filter. But I do not think it will be a big issue as the interference is presumably very small. For in-band interference, other people already suggested SAIC, you can find a lot of references about the algorithm.
> > 3, can anybody give a useful link on algorithms on anti-interference/noise > whitening filter? > > hope somebody can help. Thank you. > > Richard