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I have three questions:
1. I am implementing a system wherein I have OFDM transmission from one board to another. I want to configure the receiver's two radio cards separately.
One daughter card will be a proper receiver (just receives the data). The other daughter card in my Rx will keep hopping from one channel to another and compute
the channel utilization (1 to 14) (some amount of signal processing which I intend to do in PowerPC itself) .
For this, I wish to use the OFDM reference design_v12 provided in the repository itself. I wanted to ask that is it possible to implement it because I think my signal processing function for spectrum estimation might stop the reception on other radio card as the processor can handle one call at a time. What should I do ?
2. I intend to use the FFT block in your OFDM reference design for some processing on received data. How do I do that ?
3. In which buffer is the received data stored?
Last edited by Rohan Surana (2009-Jun-15 06:20:39)
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1) I would recommend implementing the signal processing for calcuating channel utilization in the FPGA fabric. It would be possible to do in the PowerPC, but it will likely consume enough time to interfere with performance of the MAC protocol.
You can access the RSSI signal for the second radio in the FPGA, and use this to monitor the energy received. RSSI is a good choice for this as its dynamic range covers the full Rx power range (i.e. you can monitor RSSI values without having to adjust Rx gains). The RSSI output is proportional to Rx power on whatever channel the radio is tuned to. Both the OFDM PHY and WARPLab System Generator models are good examples of models which use the RSSI input.
2) You won't be able to use the same FFT core as the OFDM Rx; this core is utilized heavily during a packet reception.
3) Received packets are stored in a BRAM block which is also attached to the PLB. This BRAM is divided into 32 sub-buffers; the PHY can write received packets into any of them. The index of the current Rx buffer is controlled via C code (warpphy_setBuffs(TxBuf, RxBuf)).
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