I think its the MAC rate(s) used for calculating the Tx time of a packet. Yes the header is sent at basic rate always, to overcome the sync issue at all.
Well for PHY, I think it should only be related for PHY calculations as per the modulation used. So different PHY rates enable different MAC rates. basim On Fri, Nov 21, 2008 at 5:30 PM, Mayur <[EMAIL PROTECTED]> wrote: > > Dear Network and NS experts, > > Why MAC and PHY rates should be different for a given packet to be > transmitted. I could not understand the calculation of the txtime of a > packet in mac-802_11.cc. > > As observed in the txtime() calculation in mac-802_11.cc, the txtime of > any packet is calculated as : > t = tp + tm, > where tp is calculated using the PLCPDatarate for the PLCP > header length and tm is calculated using mac dataRate_ (or basicRate_.) > for the MAC Header part. Now the doubt is as follows: The complete frame > (PHY+MAC+MSDU) will go holistically or completely only. Then there > should be only one data rate which decides the tx time. Why two rates > working for each of its own layer? ie. phy data rate for phy part and > mac data rate for mac part? I could not understand what happens in > reality, and how is it tried to be put here in ns2 simulation. > > Pl clarify my doubts from both of these angles: Theoretically and from > ns Simulation point of view too. > > regards, > Mayur > >
