Hello Saravanan, Thanks for your reply! Ok, I checked this function and basically and if I understood correctly, in function "sendData" for broadcast packets we call txtime() as below: ch->txtime() = txtime(ch->size(), basicRate_); So, roughly speaking the txtime for a broadcast data packet is as following: txtime= plcp_hdr/plcpdataRate + datalength/dataRate_ where basicRate_=bandwidth_ according to implementation of constructor of mac-802.11.cc. But I still have some questions, that I would really be greateful if you reply: 1) How we know the value of "bandwidth_" is "Phy/WirelessPhy set bandwidth_", I though that I should find something like "Mac 802.11 set bandwidth_" in "ns-default.tcl" 2)How should I choose the value of "basicRate_", if I would like to set it my self? Thanks, Best regards, Behnaz ----- Original Message ----- Expéditeur: Saravanan Kandasamy <svana...@gmail.com> à: "ns-users@ISI.EDU" <ns-users@ISI.EDU> Sujet: Re: [ns] Default Channel bandwidth in 802.11? Date: Sun, 2 Dec 2012 13:28:46 +0000
> Dear Behnaz, > > Looks like you don't quite understand how MAC 802.11 > works. > > "Phy/WirelessPhy set bandwidth_ 2e6" will only be used if > you have not set basicRate_ or dataRate_ in your MAC > setup. > > Even so the transmission time does not do "packet > size/channel bandwidth", suggest you to study how > Mac802_11::txtime(double psz, double drt) function works > in mac-802.11.cc > > Good Luck. > > rgds > Saravanan K > > On Sun, Dec 2, 2012 at 1:02 PM, Behnaz Bostanipour > <behnaz.bostanip...@unil.ch> wrote: > > > > Hello, > > > > I would like to calculate transmission time (tx_time) > for packets sent by CMU MAC 802.11. > > > Usually we have tx_time=packet size/channel bandwidth. > > > > I looked in the "ns-default.tcl" file and I have found > this value: > > > Phy/WirelessPhy set bandwidth_ 2e6 > > > > Is this the value used for calculation of tx_time by > 802.11? > > > Thanks, > > Behnaz > > >
