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Wireless LAN 802.11 Haithem AL-Balawi. Outline  Background  Design Consideration and Assumptions  Results and Findings  Questions.

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Presentation on theme: "Wireless LAN 802.11 Haithem AL-Balawi. Outline  Background  Design Consideration and Assumptions  Results and Findings  Questions."— Presentation transcript:

1 Wireless LAN Haithem AL-Balawi

2 Outline  Background  Design Consideration and Assumptions  Results and Findings  Questions

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

4 Background  Components of the IEEE

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

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  Algorithm 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; for i=1:length(Time_Access) if (Time_Access(1,i)==0) [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 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; 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 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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