[ns] CTS EIFS NAV problem in ns-2.26 ns-2.27 802.11 protocol implementation

[Ahmad Al_Hanbali]

Hello for all

I'm a Phd student, I'm working on ADhoc networks. I found these problems
in ns-2.26 implementation of 802.11 protocol.

The first problem is :
According to 802.11 protocol specification section 9.2.5.7, "a STA that
is addressed by an RTS frame shall transmit a CTS frame 
after a SIFS period if the 'NAV' at the STA receiving the RTS frame
indicates that the medium is idle", so the sensing on sending a CTS is
'only' virtually. But in protocol implementation in ns-2.26 see file
../ns-2.26/mac/mac-802_11.cc function check_pktCTRL() the sensing is
virtually and physically using the function is_idle(). 

==================================================
int
Mac802_11::check_pktCTRL()
{
        struct hdr_mac802_11 *mh;
        double timeout;

        if(pktCTRL_ == 0)
                return -1;
        if(tx_state_ == MAC_CTS || tx_state_ == MAC_ACK)
                return -1;

        mh = HDR_MAC802_11(pktCTRL_);
                                                          
        switch(mh->dh_fc.fc_subtype) {
        /*
         *  If the medium is not IDLE, don't send the CTS.
         */
        case MAC_Subtype_CTS:
                if(!is_idle()) {
                        discard(pktCTRL_, DROP_MAC_BUSY); pktCTRL_ = 0;
                        return 0;
                }
        .
        .
        .       

================================================== 

The problem second is on receiving an erronoius frame by a node the
simulator set the NAV to eifs duration see file mac-802_11.cc function
recv_timer()

==================================================

        if( ch->error() ) {
                Packet::free(pktRx_);           
                set_nav(usec(eifs_));
                goto done;
        }

==================================================

So in case of receiving RTS in this eifs duration, i will not respond by
a CTS conforming CTS procedure section 9.2.5.7. And conforming to this i
will not stop 
the EIFS period according to section 9.2.3.4.


Its pleasure to me hear your comments.
Ahmad