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BPSK + OFDM over a very wideband channel

Started by lsw00kor November 8, 2005
Hello, everyone.
I would like to discuss OFDM's robustnesss againt freq-selective channel.

1) I'm using BPSK( for some reasons, even though mostly we use QPSK, or
QAM..) on a very very wide channel.
2) I didn't employ a channel equalizer at the frontend before fft.
3) I, as a reference, followed Richard Van Nee's 'OFDM for wireless
multimedia communications' to set the parameters:

[1] worst case delay spread = 10 nsec.
[2] 4 times [1] = 40 nsec.
[3] 6 times [2] = 240 nsec is set as an OFDM symbol's duration
[4] For Rs bits (BPSK) per an OFDM symbol, Rs * 240 nsec bits are
assigned.
[5] deltaf = 1/200nsec = 5MHz

4) But, weirdly, I always have very very bad error performance. I can't
figure it out. I think I followed the guidelines exactly to setup the
parameters.

5) But on the other hand, we usually don't test OFDM in this kind of wide
bandwidth..  So, the guidelines in [1] - [5], I wonder if they can really
work in my scheme, too.

6) Could anybody give me some advice please?

Your advice is highly appreciated. Thank you very much.





lsw00kor wrote:
> Hello, everyone. > I would like to discuss OFDM's robustnesss againt freq-selective channel. > > 1) I'm using BPSK( for some reasons, even though mostly we use QPSK, or > QAM..) on a very very wide channel. > 2) I didn't employ a channel equalizer at the frontend before fft. > 3) I, as a reference, followed Richard Van Nee's 'OFDM for wireless > multimedia communications' to set the parameters: > > [1] worst case delay spread = 10 nsec. > [2] 4 times [1] = 40 nsec. > [3] 6 times [2] = 240 nsec is set as an OFDM symbol's duration > [4] For Rs bits (BPSK) per an OFDM symbol, Rs * 240 nsec bits are > assigned. > [5] deltaf = 1/200nsec = 5MHz > > 4) But, weirdly, I always have very very bad error performance. I can't > figure it out. I think I followed the guidelines exactly to setup the > parameters. > > 5) But on the other hand, we usually don't test OFDM in this kind of wide > bandwidth.. So, the guidelines in [1] - [5], I wonder if they can really > work in my scheme, too. > > 6) Could anybody give me some advice please? > > Your advice is highly appreciated. Thank you very much.
1. lsw00kor Nov 8, 4:23 pm show options Newsgroups: comp.dsp From: "lsw00kor" <lsw00...@hotmail.com> - Find messages by this author Date: Tue, 08 Nov 2005 15:23:58 -0600 Local: Tues, Nov 8 2005 4:23 pm Subject: BPSK + OFDM over a very wideband channel Reply | Reply to Author | Forward | Print | Individual Message | Show original | Report Abuse Hello, everyone. I would like to discuss OFDM's robustnesss againt freq-selective channel. 1) I'm using BPSK( for some reasons, even though mostly we use QPSK, or QAM..) on a very very wide channel. 2) I didn't employ a channel equalizer at the frontend before fft. 3) I, as a reference, followed Richard Van Nee's 'OFDM for wireless multimedia communications' to set the parameters: [1] worst case delay spread = 10 nsec. really? what kind of channel is it? Mark