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which fpga ofdm implementation

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kusenth

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ofdm pulse shaping filter

hello sir i am final yr student doing project in ofdm implementation using vhdl.can any one help me to systematic approach of these project.
 

tiger_shark

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ofdm implementation using vhdl

Hi there,

What part of an OFDM Transceiver are you going to design. Designing the whole chain is quite overwhelming and not realistic for a student project. If you could givee us more specifically what the objective of your project is, it would be easier to comment.

REgards - TS
 

kusenth

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ofdm implementation in vhdl

Nice.thank for ur reply.actually our concentration is designing the ofdm modem,just design of ifft,bpsk at the trx.and fft,demod at the rx.since it is an demo,we can do upto this.i am somewhat fam with vhdl and modelsim tool.
waiting for reply.
 

tiger_shark

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Re: ofdm implementation

So, I believe you are not impmenting any channel impairment s (multi-path, fading, ...) or any frequency-time offset. Then You don't need to implement FEC encoding in the Tx and decoding in Rx, and you don't need to do synchronization or ... in demod.

You will need to implement just a BPSK modulator, FFT, BPSK Slicer (just comparator with zero to see if you are in the right or left of axis). You may need to implement the cyclic prefix.

Depending on number of subcarriers, you may need a pulse shaping filter (Square root raised cosine) but if the number of subcarriers are high, you don't need.

If the tx data is going out of FPGA and then received back using A/D and D/A, then you will need a resampling filter, but if all the Tx/Rx chain is in FPGA, then you dont.

For FFT you can find Verilog / VHDL cores and sample codes on web. You usually don't design these fundamental blocks and just use the IPs or available codes.

A more complicated example of what you are designing can be found in PHY layer (chapter 8.3) of IEEE 802.16-2004 (wimax) standard. If you could, look in there and see the chain.

One thing which might be important in your design is how u use best of bits when you go through FFT or filtering. You should use full range of your coefficients and outputs (say 18 bits) so that you will have least level of noise floor and spur (if important for you).

The rest of modules that you might build would probably be a random signal generator (LFSR pseudo-random generator) in the input, and a comparator in the output to compare the received signal with the transmitted signal and count the errors. You can then add some kind of noise to the tx signal as channel effects and simulate your design to see how much BER you will get.

Lots can be done in such project but if you are going to graduate soon, I recommend that you have a look at 802.16 standards so that when you are being interviewed, you can claim that you are familiar with this standard.

If you have any specific question, let me know. I have only worked with Xilinx though.

Regards - TS
 

senthils

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Re: ofdm implementation

hello kusenth,
u may just grasp ieee std format protocol before doing this pro.
 

kusenth

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Re: ofdm implementation

thank u mr.tiger_shark.
i just have a sence of realistic, when i read ur comments.i may do as by ur comment,but ill little bit struck up while skipping some of the blocks,i dont know which block should i skip which should not and if i design by without knowlege of blocks it would results in error.so can u please give me a block which r essentially needed for this(simulation purpose).i may use some ips from ip cores and please mention how much radix-fft,bpsk bit size,should i needed etc..(specification).
waiting for reply.
 

Harshash

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Re: ofdm implementation

Hi Sir..

Sir i'm workng on PAPR rduction of OFDM signals..
Can u pls help me regardiing th same..

i.e how to calculate the PAPR of OFDm Signals..

Expecting your fruitful reply..

With Regards..
Harsha
 

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