How Physical Carrier Sense Affects System Throughput in IEEE Wireless Networks Zheng Zeng, Yong Yang and Jennifer C. Hou Department of Computer Science, University of Illinois at Urbana- Champaign IEEE INFOCOM 2008 Outline Introduction Background Material Analytical Model Simulation Conclusion Introduction IEEE DCF CSMA Detecting ongoing transmission and Mitigating interference Physical and Virtual carrier sense Back-off Resolving contention Introduction (cont.) IEEE DCF CS th is a tunable parameter Spatial reuse Transmission quality CS th Interference Spatial reuse Network Throughput Background Material p-persistent Model that Characterizes IEEE DCF in WLANs Interference Model p-persistent Model that Characterizes IEEE DCF in WLANs Interference Model Analytical Model Assumption Max transmission range : R tx SINR : Accumulative interference contributed by nodes that are outside R CS Analytical Model Multi-hop wireless network Analytical Model E(I) Analytical Model E(N c ) and E(T c ) Tpye-1 Collision Simultaneous transmission within the interference range Tpye-2 Collision Tpye-3 Collision Modification of t v Simulation setup J-sim (http://www.j-sim.org/)http://www.j-sim.org/ 480 nodes (240 senders) 900m* 900m D SR = 80m Data rate = 2Mbps and 6Mbps CW size = 8 ~ 256 R CS = 140m~220m CBR packets of size = 512 KB Simulation result Conclusion New analytical model Physical carrier sense SINR Collision caused by accumulative interference and hidden terminals Future research The effect of CW The effect of routing and MAC and intra-flow interference