[ns] Problem with using different frequency while simulating 802.11

[minhong]

Hello ns-users,
         I got problem in the simulation secnario :
Let 25 nodes move into the overlapped of two Access Points, lots of packets 
were dropped by DSDV_Agent.
ex: AP1 at (250, 250)   , and AP2 is 50 meters away from AP1, i.e. (300,250)
      Both APs have the transmission range with 50 meters

      let these nodes move into the position of ( 275, 250 )


when the number of nodes is under 20, it works well with low packet loss rate.
Does anyone have ideas about the situation ?

    I have traced dsdv/dsdv.cc , at the line of 900 about

    dst = node_->base_stn();
    prte = table_->GetEntry (dst);
    if ( prte && prte->metric != BIG )
        goto send ;
    else {
        fprintf(stderr, "warning: Route to base_stn not known: dropping pkt\n") 
;
        Packet::free(p);
        return ;
    }

    however, the condition prte->metric != BIG is false, so packets were 
dropped.



Therefore, is it possible that we can configure these nodes with different 
frequency
( ex: assign channel 1 for 10 nodes, channel 6 for others )
such that we can reduce lots of packet loss rate in above simulation scenario ?


Thanks in advance for your reading.
minhong.