求助：NS2无线仿真中TCP吞吐量过低问题

问题是这样的：在NS2里设置 $err set rate_ 0.05 的时候，这个0.05指的是每个比特的错误率还是每个包的丢包率？如果加了
$err unit packet 这句是不是意味着每发100个包，会丢5个呢？
我还在tcl文件里写了设置带宽的语句如下：
set mac_($i) [$node_($i) getMac 0]
        $mac_($i) set dataRate_ 11Mb
        $mac_($i) set basicRate_ 1Mb
传输层用了一个TCP Vegas协议。 但是最后统计吞吐量的时候吞吐量大小只有2Mbps，与11Mbps差很多，这对于无线TCP是正常的吗？
谢谢！
代码如下：
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set val(chan)           Channel/WirelessChannel    ;# channel type
set val(prop)           Propagation/TwoRayGround   ;# radio-propagation model
set val(netif)          Phy/WirelessPhy            ;# network interface type
set val(mac)            Mac/802_11                 ;# MAC type
set val(ifq)            Queue/DropTail/PriQueue    ;# interface queue type
set val(ll)             LL                         ;# link layer type
set val(ant)            Antenna/OmniAntenna        ;# antenna model
set val(ifqlen)         50                         ;# max packet in ifq
set val(nn)             2                          ;# number of mobilenodes
set val(rp)             AODV                       ;# routing protocol
set val(x)              100                        ;# X dimension of the topography
set val(y)              100
set val(err)                UniformErrorProc
set loss_rate 0.05
set chan_1_ [new $val(chan)]
# *** Throughput Trace ***
set f0 [open test-single-tcp-out-tcp.tr w]
# *** Throughput Trace ***
set ns [new Simulator]
set tracefd [open test-single-tcp.tr w]
$ns trace-all $tracefd
proc UniformErrorProc {} {
        global loss_rate
        puts "dfdfad-----------------------------"
        set err [new ErrorModel]
        $err unit packet
        $err set rate_ $loss_rate
        return $err
}
proc finish {} {
        global ns tracefd f0
        # Close Trace Files
        close $f0
      # Plot Recorded Statistics
        exec xgraph test-single-tcp-out-tcp.tr  -geometry 800x400 &
        $ns flush-trace
        close $tracefd
        exit 0    
}
set topo [new Topography]
$topo load_flatgrid $val(x) $val(y)
create-god $val(nn)
$ns node-config -adhocRouting $val(rp) \
                -llType $val(ll) \
                -macType $val(mac) \
                -ifqType $val(ifq) \
                -ifqLen $val(ifqlen) \
                -antType $val(ant) \
                -propType $val(prop) \
                -phyType $val(netif) \
                -channel $chan_1_ \
                -topoInstance $topo \
                -agentTrace ON \
                -routerTrace ON \
                -macTrace OFF \
                -movementTrace OFF \
                -OutgoingErrProc $val(err)
for {set i 0} {$i < $val(nn) } {incr i} {
        set node_($i) [$ns node]        
        $node_($i) random-motion 0                ;# disable random motion
        set mac_($i) [$node_($i) getMac 0]
        $mac_($i) set dataRate_ 11Mb
        $mac_($i) set basicRate_ 1Mb
}
$node_(0) set X_ 5.0
$node_(0) set Y_ 2.0
$node_(0) set Z_ 0.0
$node_(1) set X_ 50.0
$node_(1) set Y_ 20.0
$node_(1) set Z_ 0.0
$ns at 1.0 "$node_(0) setdest 5.0 2.0 1.0"
$ns at 1.0 "$node_(1) setdest 50.0 20.0 15.0"
#$ns at 100.0 "$node_(1) setdest 490.0 480.0 15.0"
set tcp1 [new Agent/TCP/Vegas]
$tcp1 set class_ 2
set sink1 [new Agent/TCPSink]
$ns attach-agent $node_(0) $tcp1
$ns attach-agent $node_(1) $sink1
$ns connect $tcp1 $sink1
set ftp1 [new Application/FTP]
$ftp1 attach-agent $tcp1
# Initialize Flags
set holdtime1 0
set holdseq1 0
set holdtime2 0
set holdseq2 0
set holdrate1 0
set holdrate2 0
proc record {} {
        global sink1 f0  holdtime1 holdseq1 holdtime2 holdseq2 holdrate1 holdrate2
        set ns_ [Simulator instance]      
        set time 10.0 ;#Set Sampling Time to 0.9 Sec
set bw0 [$sink1 set bytes_]
            set now [$ns_ now]
         puts $f0 "$now [expr (($bw0+$holdrate1)*8)/(2*$time*1000000)]"
        $sink1 set bytes_ 0
       set holdrate1 $bw0
    $ns_ at [expr $now+$time] "record" ;# Schedule Record after $time interval sec
}
# Start Recording at Time 0
$ns at 0.0 "record"
$ns at 1.0 "$ftp1 start"
for {set i 0} {$i < $val(nn) } {incr i} {
    $ns at 1000.0 "$node_($i) reset";
}
$ns at 1000.0 "finish"
$ns run

出两兆的带宽正常
考虑三个节点的chain，你会发现至少有3个节点需要总是竞争带宽
11 / 3 差不多是4；考虑丢包，balance的问题，最后出个2兆可以接受