Hi All I have simulated a performance of the receiver for time varying frequency selective channel. I am using adaptive equalizer to combat multipath. What I would like to do is to derive closed form solution such as lower/upper bound or exact solution for BER. However, there are many variables: time varying channel, no channel state information at the receiver, adaptive equalizer and channel coding. By time varying I mean, channel changes at every symbol. How can I approach such problem? Many thanks. Chintan Shah

# Derive closed form solution for a receiver

Started by ●January 5, 2010

Reply by ●January 5, 20102010-01-05

On Jan 5, 12:38 pm, "cpshah99" <cpsha...@rediffmail.com> wrote:> Hi All > > I have simulated a performance of the receiver for time varying frequency > selective channel. I am using adaptive equalizer to combat multipath. > > What I would like to do is to derive closed form solution such as > lower/upper bound or exact solution for BER. > > However, there are many variables: time varying channel, no channel state > information at the receiver, adaptive equalizer and channel coding. > > By time varying I mean, channel changes at every symbol. > > How can I approach such problem? > > Many thanks. > > Chintan ShahChintan, First, think about whether you really need a closed-form expression. In most cases, you will get better understanding by doing a simulation and estimating the bit error rate. If you indeed want to analytically find the closed-form expression, you should probably consult a textbook like Digital Communications by John Proakis. Upper and lower bounds are calculated for many cases there. Dilip.

Reply by ●January 5, 20102010-01-05

cpshah99 wrote:> Hi All > > I have simulated a performance of the receiver for time varying frequency > selective channel. I am using adaptive equalizer to combat multipath. > > What I would like to do is to derive closed form solution such as > lower/upper bound or exact solution for BER.> However, there are many variables: time varying channel, no channel state > information at the receiver, adaptive equalizer and channel coding. > > By time varying I mean, channel changes at every symbol. > > How can I approach such problem?Let the multipath energy be W, speading function S. Equalizer reduces W by the factor E. Assume equalizer is optimal Kalman filter, then E is a function of SNR and S. The W times E adds to the signal; that is Raleigh process. Find error rate from there.> Many thanks. > Chintan ShahSTUPIDENT MATLABI

Reply by ●January 6, 20102010-01-06

Hi Dilip Thanks. Although simulation is good to understand, somebody can ask how to derive the same results thru analysis. Proakis does not have such treatment. Please tell me the page number if you have come across.>Let the multipath energy be W, speading function S. >Equalizer reduces W by the factor E. >Assume equalizer is optimal Kalman filter, then E is a function of SNR >and S. The W times E adds to the signal; that is Raleigh process. Find >error rate from there. >Hi Vlad I am sorry but I did not understand it. It will be great if you can expalin a bit further.> >STUPIDENT MATLABI >Yeah I think so.

Reply by ●January 6, 20102010-01-06

On Jan 6, 5:21�am, "cpshah99" <cpsha...@rediffmail.com> wrote:> Hi Dilip > > Thanks. > > Although simulation is good to understand, somebody can ask how to derive > the same results thru analysis. Proakis does not have such treatment. > Please tell me the page number if you have come across. >In my 3rd edition, there is a section on "Performance Characteristics of the MSE Equalizer" in a chapter titled "Communication through Band- limited channels".

Reply by ●January 7, 20102010-01-07

>On Jan 6, 5:21=A0am, "cpshah99" <cpsha...@rediffmail.com> wrote: >> Hi Dilip >> >> Thanks. >> >> Although simulation is good to understand, somebody can ask how toderive>> the same results thru analysis. Proakis does not have such treatment. >> Please tell me the page number if you have come across. >> > >In my 3rd edition, there is a section on "Performance Characteristics >of the MSE Equalizer" in a chapter titled "Communication through Band- >limited channels". >Hi Dilip Thanks again. I found the section in my 4th edition in Chapter 10. I have seen this treatment but it considers fixed channel not 'Time varying'. I think the problem that I am trying to solve needs some assumptions. Because it matters a lot how we model the time varying frequency selective channel. Also if the receiver has the channel knowledge or not, which type of adaptive algorithm we use etc... Thanks again. Chintan Shah

Reply by ●January 7, 20102010-01-07

Performance Analysis over fading channel can be quite complicated. As general approach, assuming that the received signal is corrupted by Gaussian noise, you need to: 1. Derive the SNR expression conditioned to the channel (i.e., for a given channel realization). Then the instantaneous Bit Error Probability will in the form of the Q() function. 2. Next, you need to average the instantaneous BEP over the statistic of the channel fading (such as Rayleigh, Nakagami, etc. ). This is the difficult part, and coming up with a close form solution is not trivial. On my opinion, the most complete treatment on this subject is the book "Digital Communication over Fading Channels, 2nd Edition" Marvin K. Simon, Mohamed-Slim Alouini If you are interested in performance analysis of wireless communication systems over fading channels, this is absolutely the book you must look at.

Reply by ●January 7, 20102010-01-07

>Performance Analysis over fading channel can be quite complicated. > >As general approach, assuming that the received signal is corrupted by >Gaussian noise, you need to: > >1. Derive the SNR expression conditioned to the channel (i.e., for agiven>channel realization). Then the instantaneous Bit Error Probability willin>the form of the Q() function. > >2. Next, you need to average the instantaneous BEP over the statistic of >the channel fading (such as Rayleigh, Nakagami, etc. ). This is the >difficult part, and coming up with a close form solution is not trivial. > >On my opinion, the most complete treatment on this subject is the book > >"Digital Communication over Fading Channels, 2nd Edition" >Marvin K. Simon, Mohamed-Slim Alouini > >If you are interested in performance analysis of wireless communication >systems over fading channels, this is absolutely the book you must look >at. > >%%%% Hi Marco Thanks. I have seen this book vaguely. Most of the books deal with frequency flat fading, very few deal with frequency selective fading. I will still have a look at the book u have suggested. I might find something. Thanks again. Chintan Shah