How do I lock to a channel while in ad hoc mode?

[Tom Izard]

Hello List,

I am running EnGenius 2511CD Plus EXT2 cards in Soekris 4511's using 
Pebble Linux which has HostAP.  I can get them set up and running just 
fine in ad hoc mode.  Right now I am only dealing with two such systems.

The Problem:
Once they are talking, I would like to be able to change the channel 
they are using.  And have them remain on the new channel!  So far, I 
have had very spotty results using

iwconfig wlan0 channel <new_channel>

Sometimes, it will change the channel on system A and then system B will 
change automatically to match.

Sometimes, I can not get the channel on either system A or B to change

Analysis So Far:
I have googled quite a bit and found a half dozen other similar 
complaints but never a follow-up reply.

Sort-of Solution:

If I start with both systems ping'ing (say on channel 1)

system_a > iwconfig wlan0 channel 3           --- often, no channel 
change occurs, pings work
system_b > iwpriv wlan0 host_roaming 2     --- both remain on channel 1 
but pings fail
system_a > iwconfig wlan0 channel 3           --- channel changes to 3 
on A only
system_b > iwpriv wlan0 host_roaming 0     --- channel changes to 3 on B 
and pings work
system_b > iwpriv wlan0 host_roaming 2     --- both channels at 3, pings 
fail
system_b > iwconfig wlan0 channel 9           --- no channel change 
occurs, pings fail
system_a > iwconfig wlan0 channel 9           --- channel changes to 9 
on A only, pings fail
system_b > iwconfig wlan0 channel 9           --- no channel change on 
B, pings fail
system_b > iwpriv wlan0 host_roaming 0     --- channel changes to 9 on 
B, pings work

Questions:

Is this the proper method for channel changing in ad hoc mode?
Is there a better way to do things? (I do not like that the second 
system "find"s the first one; I would prefer to be able to set [lock] 
the channel.)
Why does the intial channel change request (when both systemes have 
host_roaming=0) work some times but not others?

Thanks for your consideration,

Tom
 
-----------------------------------------

Tom Izard
Apple Aid Inc.
4246 Ridge Lea Rd
Amherst, NY 14226