Can't Find a Chip for Video Delivery Using OFDM Systems

[Shahil]

I've been searching for HOURS and i still can't find anything...

Okay..i got a project ... quite an intensive one .. Video Delivery using OFDM comm. systems (Orthogonal Frequency Division Multiplexing)

Basically..get video..modulate it (I chose BPSK because of the simplicity) sed it into a DSP board and the DSP will do the OFDM things and transmit to another DSP board which will undo the OFDM thing and then send to a BPSK demod that will give back the original bitstream so as to be broadcast as video.

Now..I need a chip to do the BPSK (or QPSK or QAM) modulation...I can't find a proper one..grrr...google aint my friend!

Can somebody suggest a part PLEASE or at least tell me where to look and find one?

Ta

 

[berkeman]

Is the original video stream already digitized? Or is it an analog baseband or analog IF or analog RF broadcast waveform?

Once it's digitized, can you just send a clock and baseband digital data to the OFDM uplink board? Why bother with BPSK just to get a baseband digital signal into the OFDM board?

 

[Shahil]

Getting an MPEG2 digital stream in ... sending it into a DSP where I'm going to program in the OFDM ..

The BPSK (or QPSK) modulation is just for, how can i put it, signal integrity .. like an error check .. kinda making sure that the received signal will be off rather good quality. It's kinda just a error reduction process.

Also, the DSP board that I'm going to have can't handle large datarates so modulation is quite necessary

 

[berkeman]

Getting an MPEG2 digital stream in ... sending it into a DSP where I'm going to program in the OFDM ..

The BPSK (or QPSK) modulation is just for, how can i put it, signal integrity .. like an error check .. kinda making sure that the received signal will be off rather good quality. It's kinda just a error reduction process.

Also, the DSP board that I'm going to have can't handle large datarates so modulation is quite necessary

I'm not understanding what you are saying. PSK modulation does nothing for signal improvement -- it's already a digital MPEG2 data stream. If anything, modulating it into an analog PSK waveform can degrade the content.

And I don't get your comment about how modulation will decrease the datarate.

 

[chroot]

This doesn't make any sense at all, in fact. Perhaps you don't really understand OFDM?

The "OFDM" board must necessarily already be doing some kind of digital modulation (like BPSK) on each of its output subbands.

BPSK (and QPSK, etc.) are essentially methods of converting digital information into analog waveforms, and OFDM is essentially just a collection of these analog waveforms on adjacent narrowband channels.

You claim to have an OFDM board, which has a DSP, and presumably accepts digital data. But you claim you're looking for a device which does BPSK modulation, the output of which would be an analog waveform. It doesn't really make any sense to hook up a device with an analog output into another with a digital input.

I also have no clue why you think that BPSK is a way to do "error-checking," because it isn't. You would perform error checking at the byte or block level, well before the modulator.

And BPSK does not do anything to reduce data rate -- it just converts a digital waveform into an analog waveform, carrying exactly the same information in a different form.

- Warren

 

[Shahil]

Ya .. i do think I'm talking nonsense:P um..

I have a DSP board that I am going to implement OFDM on ... not the other way around..

Hmm...I think I have confused myself .. lol .. let me get back to my books

i did discuss this with my supervisor and he suggested that i take in the MPEG2 video into a BPSK modulator and feed it into the DSP ... it made sense and you ...

I'll get back to you guys