Interfaces of  Wireless MAC in ns-2

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General Architecture of a mobile node in ns-2:

 

the relationship of MAC could be found in ns-mobilenode.tcl. The source code:

........
#
# The following setups up link layer, mac layer, network interface
# and physical layer structures for the mobile node.
#
Node/MobileNode instproc add-interface { channel pmodel lltype mactype \
		qtype qlen iftype anttype topo inerrproc outerrproc fecproc} {
	$self instvar arptable_ nifs_ netif_ mac_ ifq_ ll_ imep_ inerr_ outerr_ fec_
	
  .......    
   	#
	# Link Layer
	#
	$ll arptable $arptable_
	$ll mac $mac
	$ll down-target $ifq

	if {$imepflag == "ON" } {
		$imep recvtarget [$self entry]
		$imep sendtarget $ll
		$ll up-target $imep

        } else {
		$ll up-target [$self entry]
	}
	#
	# Interface Queue
	#
	$ifq target $mac
	$ifq set limit_ $qlen
	if {$imepflag != ""} {
		set drpT [$self mobility-trace Drop "IFQ"]
	} else {
		set drpT [cmu-trace Drop "IFQ" $self]
        }
	$ifq drop-target $drpT
	if { $namfp != "" } {
		$drpT namattach $namfp
	}
         
        # Mac Layer
	#
	$mac netif $netif
	$mac up-target $ll

	if {$outerr == "" && $fec == ""} {
		$mac down-target $netif
	} elseif {$outerr != "" && $fec == ""} {
		$mac down-target $outerr
		$outerr target $netif
	} elseif {$outerr == "" && $fec != ""} {
		$mac down-target $fec
		$fec down-target $netif
	} else {
		$mac down-target $fec
		$fec down-target $outerr
		$err target $netif
	}

Actually, from top to down path, the structure is  ll  --->  ifq ----> mac ---> netif . for packets going up, it is netif ---> mac --->ll. Thus, ifq is only used for down path of . however, a scheduler is also only useful to handle outgoing packets. Thus, if we want to implement a scheduler, we have to use something to replace this "ifq" and remake the interface in tcl script.