Hi Adrian, Thanks for the reply.
I am realize there might be hardware constraint for me to use sectorised antenna. I currently have a NIC with only one antenna exposed . I have reconsidered my scenario and now I am planning to use switched beam antennas (specifically ESPAR antenna). This antenna technology has only one feed line similar to the omnidirectional antenna. In this case, I don't have to worry about modifying HAL code. ESPAR antenna can be configured as either omnidirectional or directional. Directional beams can be achieved by electronically controlling the parasitic elements, for instance by sending a byte value via a serial port on a per packet basis. If I can rephrase the idea, this is what I would like to explore. I want to create a scenario where upon start up, each node uses omnidirectional antenna. Then, once a neigboring node requests association, i want to perform a scan using each of the 4 antenna beams and based on the beam which gives me max RSSI, I assume it is the best sector/beam to be used to communicate with that neighbor. So an extra parameter can be introduced in the neighbor's table to flag the antenna sector/sector which has to be used whenever a node communicates with that specific neighbor. I am assuming the all nodes receive using omnidirectional antenna configuration but transmit (per packet level) using directional beam configuration. It would be more interesting if such a routine is automatically performed within the driver for every station that is added into the neighbor's table. For simplicity I am assuming static network topology. The directional beam configuration is achieved by sending appropriate byte value via serial port (RS232) to control and direct the antenna radiation pattern towards desired direction. I have already achieved this by modifying MADAWIFI. I have to try it using mac80211 and ath5k driver. The only challenge is achieving neighbor discovery especially in ad-hoc mode. With thanks, Mofolo On 13 May 2013 19:29, Adrian Chadd <adr...@freebsd.org> wrote: > Hi, > > I figure I'll give a 30 second introduction into "sectored antenna" > support. > > So the AR5212 era chips have four antenna control bits. They're ANTA -> > ANTD. > > Now, there's some switch table registers. By default the HAL code sets > these up so BB_ANTENNA_CONTROL, BB_SWITCH_TABLE1 and BB_SWITCH_TABLE2 > map to "idle", "stuff with antenna 1" and "stuff with antenna 2." This > is for non-sectored operation. I can go into more detail here if you'd > like. > > For sectored operation, you don't leave ANTA:ANTD up to the switch > table. You control the TX antenna configuration and you use the single > "omni" antenna for receiving frames (normal RX, RTS, listening for ACK > too I guess.) There's four antenna config bits in the TX descriptor > for each rate attempt, along with DEFANT for the omni antenna > configuration. In this mode (sector AP mode) its up to the driver and > wifi stack to track the per-client, per-sector behaviour and choose an > optimal sector configuration for that. > > The 11n chips have something but not quite similar for this kind of > antenna selection. > > So, if you have a modified NIC that exposes ANTA->ANTD and you can > make up a sectored antenna configuration + omni antenna configuration, > I can attempt to help you. I haven't done this myself; I'm just going > on what I have here. > > Thanks, > > > > Adrian >
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