Marco, Won't the traffic type also be of significance in such a case. While CBR/UDP will be constantly sending packets at a fixed rate, FTP/TCP will be aggressively trying to send in as many packets as possible for every round trip time. As you said, the offered load is thus certainly a factor. If TCP is used, then we observe that fairness becomes an issue as a particular flow almost captures the whole channel - specially if there are exposed nodes in the network. This flow does not allow the net throughput of the network to increase. With the RTS-CTS turned on, the exposed node continually senses the neighboring node to be sending Data packets and more often than not is not able to transmit its own RTS/CTS pkt. In such a scenario the basic access scheme does give a greater throughput.
Your point of RTS-CTS packets generating extra overhead is also certainly very relevant in this scenario. Zubair On Mon, 30 Jan 2006 Marco Fiore wrote : > >Michael, > >it may be that increasing the data rate to 5,5 or 11 Mbps >the >number of collisions is reduced a lot. As a consequence, >the RTS/CTS >mechanism only introduces overhead. >This depend on the offered load (i. >e. how much traffic >is present) in the network. > >Regards, > >Marco Fiore > >----Messaggio originale---- >Da: [EMAIL PROTECTED] >Data: 30-gen-2006 >11.55 AM >A: <[email protected]> >Ogg: [ns] lower RTS/CTS saturation >throughput > > > Hello ns users, > I have a question regarding >saturation throughput in a wireless lan. > I am examining both >basic access and rts/cts mechanisms and measure the > saturation >throughput as the number of nodes participating in the network >increases. > > I noticed that for 1Mbps channel rate the >rts/cts access scheme gives better throughput results compared with >the basic access scheme.I think that this behavior is expected as the >rts/cts mechanism reduces the number of collisions. > However when >I assume 5.5Mbps and 11 Mbps channel rate the throughput results that >I am getting from the ns-2 simulation are a lot lower than the >corresponding ones from the basic access scheme( for 5.5Mbps and 11 >Mbps ) > Is this behavior normal? > To change the channel >data rate I have put in my tcl script: > Mac/802_11 set >dataRate_ 11.0e6 ;# 11Mbps or 5,5 Mbps > Mac/802_11 set >basicRate_ 1.0e6 ;# 1 Mbps > Is the basicRate correct? > Has anyone else experienced something similar? > I am >waiting for your opinions, > Thank you for your attention, > Regards, > Michael > > > >--------------------------------- > ΧÏηÏιμοÏοιείÏε Yahoo! > ÎαÏεθήκαÏε Ïα >ενοÏληÏικά Î¼Î·Î½Ï Î¼Î±Ïα (spam); Το Yahoo! Mail >διαθÎÏει Ïην καλÏÏεÏη >Î´Ï Î½Î±Ïή ÏÏοÏÏαÏία καÏά ÏÏν ενοÏληÏικÏν >Î¼Î·Î½Ï Î¼Î¬ÏÏν > http://login.yahoo. >com/config/mail?.intl=gr > > Mohammad Zubair Ahmad PhD Student, Computer Engineering University of Central Florida, Orlando, FL 32826
