Comments on: BPSK BER with OFDM modulation http://www.dsplog.com/2008/06/10/ofdm-bpsk-bit-error/ Signal Processing for Communication Fri, 30 Jul 2010 01:36:27 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: Krishna Sankar http://www.dsplog.com/2008/06/10/ofdm-bpsk-bit-error/#comment-33954 Krishna Sankar Tue, 27 Jul 2010 02:11:40 +0000 http://www.dsplog.com/?p=166#comment-33954 @makra: I have not do written anything on LTE till now. Its on my growing to-do list :) @makra: I have not do written anything on LTE till now. Its on my growing to-do list :)

]]> By: makra http://www.dsplog.com/2008/06/10/ofdm-bpsk-bit-error/#comment-33931 makra Mon, 26 Jul 2010 13:52:42 +0000 http://www.dsplog.com/?p=166#comment-33931 Hello, I was wonder if you are going to post anything related to Basic LTE transmission which might be similar to this post. Hello,
I was wonder if you are going to post anything related to Basic LTE transmission which might be similar to this post.

]]> By: Krishna Sankar http://www.dsplog.com/2008/06/10/ofdm-bpsk-bit-error/#comment-33895 Krishna Sankar Mon, 26 Jul 2010 01:50:54 +0000 http://www.dsplog.com/?p=166#comment-33895 @Neil: 1/ Its a system design choice. For indoor wireless lan, the worst case delay spread is found to be around 0.8us (and 0.8us with 20MHz sampling gives 16 samples) 2/ Scaling factor for 16QAM is 1/sqrt(10). Please refer http://www.dsplog.com/2007/09/23/scaling-factor-in-qam/ @Neil:
1/ Its a system design choice. For indoor wireless lan, the worst case delay spread is found to be around 0.8us (and 0.8us with 20MHz sampling gives 16 samples)
2/ Scaling factor for 16QAM is 1/sqrt(10). Please refer http://www.dsplog.com/2007/09/23/scaling-factor-in-qam/

]]> By: Krishna Sankar http://www.dsplog.com/2008/06/10/ofdm-bpsk-bit-error/#comment-33691 Krishna Sankar Thu, 22 Jul 2010 01:01:57 +0000 http://www.dsplog.com/?p=166#comment-33691 @Xudong Wu: Ok, will do so. @Xudong Wu: Ok, will do so.

]]> By: Xudong Wu http://www.dsplog.com/2008/06/10/ofdm-bpsk-bit-error/#comment-33657 Xudong Wu Wed, 21 Jul 2010 11:34:45 +0000 http://www.dsplog.com/?p=166#comment-33657 Thank you for your explaination, so, can you make a post to illustrate channel estimation in OFDM system? Thank you for your explaination, so, can you make a post to illustrate channel estimation in OFDM system?

]]> By: Krishna Sankar http://www.dsplog.com/2008/06/10/ofdm-bpsk-bit-error/#comment-33621 Krishna Sankar Wed, 21 Jul 2010 00:59:33 +0000 http://www.dsplog.com/?p=166#comment-33621 @Xudong Wu: Well, in 802.11a we have a preamble portion defined as "Long Training Field" at the beginning of the packet. All the subcarriers in this preamble is known at the receiver, and this is used to estimate the channel. As the packet duration is in the order of 100's of us, the channel can be assumed to be constant for the duration of the packet. The pilots are used to correct for residual frequency errors, sampling clock offset etc. @Xudong Wu: Well, in 802.11a we have a preamble portion defined as “Long Training Field” at the beginning of the packet. All the subcarriers in this preamble is known at the receiver, and this is used to estimate the channel. As the packet duration is in the order of 100’s of us, the channel can be assumed to be constant for the duration of the packet.

The pilots are used to correct for residual frequency errors, sampling clock offset etc.

]]> By: Xudong Wu http://www.dsplog.com/2008/06/10/ofdm-bpsk-bit-error/#comment-33590 Xudong Wu Tue, 20 Jul 2010 13:17:08 +0000 http://www.dsplog.com/?p=166#comment-33590 Hi, Krishna Sankar, thank you for this wonderful post, but, when I come to my project which is based on the OFDM system, I need to use pilots to estimate the channel, and according to the IEEE802.11a and your statement, we would allocate 4 pilot subcarriers at -21, -7, 7, and 21, and the data is allocated from -26 to 26, so, my question is that how can we estimate the channel for the data from -26 to -21 and from -7 to 0(DC, and from your source code, this DC would be removed) by linear interpolation? Hi, Krishna Sankar, thank you for this wonderful post, but, when I come to my project which is based on the OFDM system, I need to use pilots to estimate the channel, and according to the IEEE802.11a and your statement, we would allocate 4 pilot subcarriers at -21, -7, 7, and 21, and the data is allocated from -26 to 26, so, my question is that how can we estimate the channel for the data from -26 to -21 and from -7 to 0(DC, and from your source code, this DC would be removed) by linear interpolation?

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