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Wireless LAN 802.11

Wireless LAN 802.11. Haithem AL-Balawi. Outline. Background Design Consideration and Assumptions Results and Findings Questions. Background. IEEE 802.11  Defines the Medium Access Control (MAC) and Physical Layer (PHY) specified for wireless connection. Background.

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Wireless LAN 802.11

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  1. Wireless LAN802.11 Haithem AL-Balawi

  2. Outline • Background • Design Consideration and Assumptions • Results and Findings • Questions

  3. Background • IEEE 802.11  Defines the Medium Access Control (MAC) and Physical Layer (PHY) specified for wireless connection

  4. Background • Components of the IEEE 802.11

  5. Network PCF MAC DCF PHY Background • MAC Overview • Distributed Coordination Function (DCF) is the Media Access Function of 802.11 MAC and used for contention services • Point Coordination Function (PCF) is used for contention free services

  6. Background • DCF Operation

  7. Design Consideration and Assumptions • STAs are transmitting randomly through a Bernoulli distribution • Hidden STAs are ignored • CW is randomly and equally likely selected between [0 CW] • STA will transmit whenever it’s P_STA >P_Tx

  8. for i=1:length(Time_Access) if (Time_Access(1,i)==0) elseif (Ready_Tx >1) N_Colision=N_Colision+1; for z=1:length(Ready_STA) N_Backoff(1,Ready_STA(z))= randint(1,1,[1 2^randint(1,1,CW-1)]); end end clear all STA=50; %Number of Terminals P_Tx=0.5; for N=1:STA data_Tx=10; %Transmitted data size IFS=2; %Interframe Space size %N_Success=zeros(1,N); % Number of successful trials CW=5; %Contention Wendow Time_Access=zeros(1,100000); N_Backoff=zeros(1,N); %Backoff Counter for each STA N_Count=zeros(1,N); IFS_Count=0; Idle=0; N_Colision=0; Ready_STA=0; • Algorithm [min_N,indx_N]=min(N_Backoff); Ready_Tx=0; y=1; if (min_N ==0) %Backoff timer is "0" if not non of the STAs are ready to transmit for a=1:N if (N_Backoff(1,a) ==0) if (P_STA(1,a) >= P_Tx) Ready_STA(y)=a; y=y+1; Ready_Tx=Ready_Tx+1; end end end if (Ready_Tx ==1) Time_Access(1,i:i+data_Tx-1)=indx_N; N_Backoff(1,indx_N)=randint(1,1,[1 2^randint(1,1,CW-1)]); Time_Access(1,i+data_Tx:i+data_Tx+IFS-1)=-1; else N_Backoff=N_Backoff-1; end

  9. Results and Findings • System Behavior for Random Access • the throughput is high for large number of STAs (65% for 50 STA) • the number of collided attempts is almost negligible • by using longer data packet size throughput improves

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