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Hi,
I am using OFDM reference design version 12.1 with certain modifications like switching off certain sub-carriers and changing the low-pass filter bandwidth on the transceiver (MAX2829) chip for video transmission using VLC player. When I transmit using UDP connection by giving the destination machine's IP, then Tx doesn't take place. But when I provide the Broadcast IP for the given pair of IP addresses then I can clearly see that Tx is happening (by using another board called USRP which works as a spectrum analyser). I cannot understand why the Rx is not receiving the video. I made the following changes to the original code:
1. Changing the first argument of WarpRadio_v1_TxLpfCornFreqCoarseAdj(0x0, FIRST_RADIO | SECOND_RADIO) from 0x1 to 0x0. ( to make Tx BW = 15Mhz)
2. Changing the modMasks[192] variable in warpphy.c by selectively shutting off 24 carriers in each block of 64 (Hence using 24 sub-carriers for Tx instead of 48).
3. Changing the value of bytesPerSymbol (from 6 * (0xF & packet->header.fullRate) to 3 * (0xF & packet->header.fullRate) ).
Given that my objective is to reduce the Tx bandwidth from 15Mhz to 7.5Mhz, are these changes sufficient ?
Does the bandwidth per sub-carrier change if we change the modulation mask such that the net bandwidth remains the same (15MHz in my case)? Incase if I want to change the bandwidth per subcarrier then what has to be done ?
Please help. I am confused.
Last edited by Rohan Surana (2009-Jun-30 06:57:09)
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Sounds like your computers aren't resolving each other's MAC addresses (via ARP), which will prevent any communication. This is usually a sign that the link between them isn't functioning. You can hard-code ARP entries (using arp -s) to force transmissions even when they aren't being received correctly.
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