WARP Project Forums - Wireless Open-Access Research Platform

1) How does warpmac_carriersense() function work? Is it measuring the received signal strength over some period of time? If it does can i change the time?
3) carriersense threshold is set to 12000. What does that mean? Also for EnergyDetThresh which is 7000?

This function reads the state of the carrier sensing logic in the PHY. This logic uses the radio's RSSI signal. It takes a running sum of RSSI samples and compares the sum to a fixed threshold. The carrier sensing and energy detection thresholds are expressed in units of summed RSSI. The raw RSSI value spans [0,1023], and the sum length defaults to 16, so the value of 12000 corresponds to a "real" RSSI threshold of 750 (12000/16).

2) How can i deactivate automatic ACK?

The auto-Tx of ACKs is implemented using the PHY's auto-responder logic. You can change the auto-responder configuration in C code (line 564 in csmamac.c for example).

I should also add that if you're using WARP v3 hardware, the 802.11 Reference Design is a much cleaner real-time MAC+PHY implementation and would be a good starting point for many research applications that previously relied on the OFDM Reference Design.

The problem with that approach is that you aren't going to be able to poll RSSI from software at regular enough intervals to get a meaningful average. Plus, you probably don't want the software spending time polling RSSI when it could be doing more important things like running the MAC. As murphpo mentioned above, the value of the RSSI being read from the OFDM Reference Design is actually already averaged. More accurately, it is a windowed sum of the last N samples of RSSI from the MAX2829 tranceiver. You can adjust the length of the sum with this register. I don't recall off hand what the maximum sum length is -- you'd have to open the PHY core and check.