Since I want set transmission range to 10m and interference range to 30m, I use 
the indep-utils/.../"threshold" utility to calculate transmission and 
interference range. 
Firstly I use:
threshold -m TwoRayGround -Pt 0.1 -fr 2.4e+9 10 
Receiving threshold RXThresh_ is: 9.89465e-08
threshold -m TwoRayGround -Pt 0.1 -fr 2.4e+9 10 
Receiving threshold RXThresh_ is: 1.09941e-08
so here is my setting:
Phy/WirelessPhy set bandwidth_ 1MbPhy/WirelessPhy set Pt_ 0.1Phy/WirelessPhy 
set freq_ 2.4e+9Phy/WirelessPhy set L_ 1.0  
# 10mPhy/WirelessPhy set RXThresh_ 9.89465e-8# 30mPhy/WirelessPhy set CSThresh_ 
1.09941e-8Phy/WirelessPhy set CPThresh_ 10.0
#RTS/CTS disabledMac/802_11 set RTSThreshold_ 3000
There are only 2 nodes, src and sink. The problem is: when I am using 
MAC/Simple as following settings, from trace file I see everything works as 
if node distance <=10m, pkt are received successfully, if distance is between 
11m to 30m then pkt is sensed but dropped, if dist >30 then sink node can not 
hear any pkt at all.
set val(chan)           Channel/WirelessChannel    ;#Channel Type 
set val(prop)           Propagation/TwoRayGround   ;# radio-propagation model
set val(netif)          Phy/WirelessPhy            ;# network interface typeset 
val(mac)  Mac/Simpleset val(ifq)            Queue/DropTail/PriQueue    ;# 
interface queue typeset val(ll)             LL                         ;# link 
layer typeset val(ant)            Antenna/OmniAntenna        ;# antenna model
However, when I switch to Mac/802_11 (set val(mac)  Mac/802_11) and keep 
everything else unchanged, sink can receive all pkt when distance <=10m, 
however, when dist > 10m, sink CAN NOT hear any pkt, no "dropped packet" in 
trace file, same when dist > 30m.
When I switched to 802_11Ext and WirelessPhyExt, now the Receiving threshold 
RXThresh_ calculated by "threshold" utility is not correct, and again there is 
no "grey zone" like in Mac/802_11.
Since there are only 2 nodes, I expect to observe the "pkt heard but dropped" 
range of (10,30) as in both MAC/Simple and MAC/802_11 at least, but results are 
I am not sure if the threhold utility can apply to 802_11Ext/WirelessPhyExt or 
Any one can advise me what could be the problem or I misunderstood the ns2 
802_11 implementation? 
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