tag:blogger.com,1999:blog-1630484231907758382.comments2016-12-12T17:01:47.190-08:00DSP & Communication Knowledge BaseUbaid Abdullahhttp://www.blogger.com/profile/09369678715275853829noreply@blogger.comBlogger216125tag:blogger.com,1999:blog-1630484231907758382.post-4880123451389757062016-12-12T17:01:47.190-08:002016-12-12T17:01:47.190-08:00I am graduate student doing research in ICI in OFD...I am graduate student doing research in ICI in OFDM due high mobility and i have many problem in channel <br /><br />1.the channel assumed to be linear time varying as follows hn=c+a*n and NCP<n<N-1,is the relation bet i/p and o/p is still convolution or not?<br /><br />2.the PDP as follows:<br /><br />TAU = [0 0.2 0.5 1.6 2.3 5.0]*1e-6<br />Pdb = [-3 0 -2 -6 -8 -10]<br />I consider a max doppler shift of Fd = 100 Hz<br />and Each channel delay tap is generated by Jake’s model.How can i get the channel?<br />thanksAnas Mohammedhttps://www.blogger.com/profile/00436133114295385567noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-13692646424367137412016-12-12T17:00:13.748-08:002016-12-12T17:00:13.748-08:00This comment has been removed by the author.Anas Mohammedhttps://www.blogger.com/profile/00436133114295385567noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-70874016706036172602016-12-12T16:38:27.984-08:002016-12-12T16:38:27.984-08:00This comment has been removed by the author.Mohammed Sobhy El-Bakryhttps://www.blogger.com/profile/00436133114295385567noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-21488881564100849022015-08-26T02:37:54.565-07:002015-08-26T02:37:54.565-07:00Asslam Aliukm Dear Ubiad,
My name is Adam, and I ...Asslam Aliukm Dear Ubiad,<br /><br />My name is Adam, and I am graduate student doing research in WCDMA erea.<br /><br />I read you article on "http://dspdotcomm.blogspot.com/2008/11/simulating-sample-spaced-rayleigh.html" which is titled as "Simulation Sample Spaced Rayleigh Channel".<br /><br />Actually I am working on performance analysis of MAI in WCDMA system using different spreading codes. I tried many times to generate Rayleigh selective fading channel and calculate its BER performance<br />I think I have problem with the channel itself but I could not figure it out.<br /><br />I tried your code also by convolving the input signal with the "taps" in your code. However, i did not get the correct answer or figure.<br /><br /><br />I am really stuck in this fore weeks now so any help or hints are really appreciated. thanks in advance.<br /><br />Best Regards,<br />Adam,<br />Adam Mohamed Alihttps://www.blogger.com/profile/16071871365281263503noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-32389594940192216612015-08-26T02:37:26.515-07:002015-08-26T02:37:26.515-07:00Asslam Aliukm Dear Ubiad,
My name is Adam, and I ...Asslam Aliukm Dear Ubiad,<br /><br />My name is Adam, and I am graduate student doing research in WCDMA erea.<br /><br />I read you article on "http://dspdotcomm.blogspot.com/2008/11/simulating-sample-spaced-rayleigh.html" which is titled as "Simulation Sample Spaced Rayleigh Channel".<br /><br />Actually I am working on performance analysis of MAI in WCDMA system using different spreading codes. I tried many times to generate Rayleigh selective fading channel and calculate its BER performance<br />I think I have problem with the channel itself but I could not figure it out.<br /><br />I tried your code also by convolving the input signal with the "taps" in your code. However, i did not get the correct answer or figure.<br /><br /><br />I am really stuck in this fore weeks now so any help or hints are really appreciated. thanks in advance.<br /><br />Best Regards,<br />Adam,<br />Adam Mohamed Alihttps://www.blogger.com/profile/16071871365281263503noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-39028492589406035112014-10-17T03:13:18.877-07:002014-10-17T03:13:18.877-07:00We didn't use tap_delays in generating channel...We didn't use tap_delays in generating channel matrix because all delays are equally-spaced, i.e., they all are 5 microseconds apart. In this special case and under the assumption that symbol period is 5 microseconds, each channel tap is one sample apart. The code will not work for any other case in which the condition of sample-spaced channel taps is not true. For example, the code will not work in the case of tap_delays = [0 1e-6 17e-6 20e-6]. You will need interpolation techniques to interpolate the channel at sample-spaced position in this case.Ubaid Abdullahhttps://www.blogger.com/profile/09369678715275853829noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-31367541485007002662014-10-16T02:36:09.479-07:002014-10-16T02:36:09.479-07:00Also why you didn't use the "tap_delays&q...Also why you didn't use the "tap_delays" in generating the channel matrix?Fatima .Ahttps://www.blogger.com/profile/16592076547786495123noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-75683942436316539422014-10-15T08:36:43.188-07:002014-10-15T08:36:43.188-07:00Hello Sir,
Thank you for the well explained topic...Hello Sir,<br /><br />Thank you for the well explained topic.<br />I have some questions:<br />1- what o you mean by averaging_interval<br />2- how can I get the channel impulse response<br /><br />Awaiting your reply!<br />Many thanks in advanceFatima .Ahttps://www.blogger.com/profile/16592076547786495123noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-17694916991751297622014-10-07T06:17:07.217-07:002014-10-07T06:17:07.217-07:00Hi Ubaid Abdullah,
dear i am Mohammed , i try now...Hi Ubaid Abdullah,<br /><br />dear i am Mohammed , i try now to make matlab code that explain the Bidirectional LMS algorithm over fast fading channel , and this subject is related to above your simulating of Rayleigh fading channel , please if you have any information about this code for BI-LMS please support me.<br /><br />Thanks a lot Mohammed Kadhumhttps://www.blogger.com/profile/00665705823338996083noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-43737516601120030312014-07-17T14:13:08.391-07:002014-07-17T14:13:08.391-07:00HELLO,
THANK YOU FOR YOUR CODE AND EXPLANATION. W...HELLO, <br />THANK YOU FOR YOUR CODE AND EXPLANATION. WHEN I TRY TO LOT YOUR CODE, ITS NOT SAME AS A FADING CHANNEL, ISN'T IT. WOULD YOU PLEASE LET ME KNOW HOW CAN I PLOT THE HISTOGRAM OF THAT?<br />AND HOW WE CAN CREAT THE CHANNEL ANALYTICALLY. I MEAN WITH WHICH KIND OF DISTRIBUTION WE CAN MAKE A SAME HISTOGRAM THAT YOU HAVE MADE NUMERICALLY.<br />THANKSAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-44434351192127868152013-12-16T07:32:33.982-08:002013-12-16T07:32:33.982-08:00What is 4 by 3 and 1 by 3 ?What is 4 by 3 and 1 by 3 ?Ubaid Abdullahhttps://www.blogger.com/profile/09369678715275853829noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-65149901914640289122013-12-16T07:31:39.503-08:002013-12-16T07:31:39.503-08:00Can you please explain what do you mean by path ga...Can you please explain what do you mean by path gains? In my opinion, $[0.4544 -0.0036 0.0065 -0.0107 0.0169 -0.0267]$ are path gains?Ubaid Abdullahhttps://www.blogger.com/profile/09369678715275853829noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-60342681738113781262013-12-16T04:38:47.757-08:002013-12-16T04:38:47.757-08:00Hi Ubaid Abdullah ,
if we have channel impulse re...Hi Ubaid Abdullah ,<br /><br />if we have channel impulse response = [0.4544 -0.0036 0.0065 -0.0107 0.0169 -0.0267] , how i can extract the path gain from the channel impulse response.<br /><br />cheers ,<br /><br />cheers ,bil maurihttps://www.blogger.com/profile/02405788883199911880noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-17487974275150342992013-11-12T03:23:58.148-08:002013-11-12T03:23:58.148-08:00sir,
can u tell me how to generate oversampled imp...sir,<br />can u tell me how to generate oversampled impulse response (4 by 3) that i can use to simulate my channel estimation code.<br />my code is working for (1 by 3) but not for (4 by 3) .my impulse response is time varying.<br /><br />VanitaVanita Pawarhttps://www.blogger.com/profile/04716324878770000253noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-76985590235378035862013-03-11T08:19:15.451-07:002013-03-11T08:19:15.451-07:00As it appears from your description, you have a lo...As it appears from your description, you have a longer length of the signal after convolution, and you don't understand how to equalize that longer length. If your OFDM system is adequately designed such that the longest path delay is within the cyclic prefix length, this longer length shouldn't matter. All you need to do at the receiver is to take an N-length FFT window, where N is your FFT length and equalize it using your channel inverse operation. So no matter what the length of your signal is after convolution, you can take the N-length window and equalize it using the method of your choice.Ubaid Abdullahhttps://www.blogger.com/profile/09369678715275853829noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-27498589576765278342013-03-07T03:05:54.001-08:002013-03-07T03:05:54.001-08:00The problem remains .....i was using both randn be...The problem remains .....i was using both randn before but while typing here i forgot to put 'n' in the second rand. <br /><br />Now please make any clearification about channel equalization. I am using SC-FDMA and when i convolve my delayed version of the signal with faded coefficients i.e. gain1 gain2 gain3 (3 tap channel), i increase my faded signal length. and equalization is not helping me.....<br /><br />Thank You for ur patience and Time<br />Talhahttps://www.blogger.com/profile/15453056151642386814noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-18382487732619819882013-03-06T06:40:05.735-08:002013-03-06T06:40:05.735-08:00gain1 = sqrt(powerTap1/2)*[randn (data) + 1j*rand(...gain1 = sqrt(powerTap1/2)*[randn (data) + 1j*rand(data)];<br /><br />in this line the first tap is normally distributed and the second one is uniformly distributed? To make gain1 Rayleigh distributed, make sure both the taps are distributed according to Gaussian pdf. I think you should first make this correction and then see if you still have problem with your simulation.Ubaid Abdullahhttps://www.blogger.com/profile/09369678715275853829noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-32522886992255172652013-02-28T02:12:55.149-08:002013-02-28T02:12:55.149-08:00There's a comment in your "Sample spaced ...There's a comment in your "Sample spaced multipath channel" by Bari ....i am trying to equalise my signal with channel_inv (as i mentioned in my previous comment) but i think equalisation has not been done properly with this channel_inv. For that reason, BER is 0.5 for all SNRs ....<br />gain1 = sqrt(powerTap1/2)*[randn (data) + 1j*rand(data)];<br />same for gain2 and gain3...<br />channel_inv = fft([gain1 gain2 gain3], N);<br /><br />any suggestionTalhanoreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-26064717127986790882013-02-27T15:57:57.570-08:002013-02-27T15:57:57.570-08:00Can you elaborate a little more? Which comment of ...Can you elaborate a little more? Which comment of mine are you referring to ? How channel_inv is related to BER? etc.Ubaid Abdullahhttps://www.blogger.com/profile/09369678715275853829noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-77736428125686916072013-02-27T15:56:06.471-08:002013-02-27T15:56:06.471-08:00Dear Obaid,
I was going through you blog and i ca...Dear Obaid,<br /><br />I was going through you blog and i came across one of your answers in which a person asked you about equalization and you answerd him with<br /><br />channel_inv = fft([gain1 gain2 gain3], N);<br /><br />where gain1, gain2 and gain3 are the gains for 3 tap channel and N is the FFT size.<br /><br />I was trying this but couldnt get the result as my BER wobbles around 0.5 with snr increases from 0 to 30. <br /><br /><br />Could you explain to me what could be wrong?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-5476676814175461462012-11-17T14:21:30.882-08:002012-11-17T14:21:30.882-08:00Thank You for this answer. I understand this now. ...Thank You for this answer. I understand this now. :)Talhahttps://www.blogger.com/profile/15453056151642386814noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-24811471157366568062012-11-17T14:20:30.516-08:002012-11-17T14:20:30.516-08:00I am sorry....but i m still confused here....I am sorry....but i m still confused here....Talhahttps://www.blogger.com/profile/15453056151642386814noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-75159068885607808642012-11-17T14:15:40.430-08:002012-11-17T14:15:40.430-08:00If you use complex path gains, you can account for...If you use complex path gains, you can account for the randomness in phase delays. If you remember a complex number can be written as a+bi = Aexp(j x theta). So, if your path gains are real, you won't be able to introduce the randomness in the phase of the signal.Ubaid Abdullahhttps://www.blogger.com/profile/09369678715275853829noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-50369317323876314082012-11-17T14:05:50.687-08:002012-11-17T14:05:50.687-08:00The tap values reflect their relative power w.r.t....The tap values reflect their relative power w.r.t. the 0-delay tap. This is the reason we take square root to convert them to a voltage value and then multiply with the unit power signal.<br />Ubaid Abdullahhttps://www.blogger.com/profile/09369678715275853829noreply@blogger.comtag:blogger.com,1999:blog-1630484231907758382.post-5686710164405953332012-11-17T13:01:07.373-08:002012-11-17T13:01:07.373-08:00Dear Ubaid,
One more thing, how would be the imp...Dear Ubaid, <br /><br />One more thing, how would be the impact of complex pathgains on our signal .....like from ur rayleigh function we have complex (real + imag) path gains ...i have seen codes that consider only real paths gains (tap values).<br /><br />Can you please explain this.<br /><br />ThanksTalhahttps://www.blogger.com/profile/15453056151642386814noreply@blogger.com