main.m

系统分别对无线通信中的几种重要的多址接入协议进行了仿真

% Program 6-1
% main.m
%
% Packet communication system
%
% MATLAB version
%
clear;
% definition of the global variable
global STANDBY TRANSMIT COLLISION PERMIT
global Srate Plen Ttime Dtime
global Mnum Mplen Mstime Mstate
global Tint Rint
global Spnum Splen Tplen Wtime
% definition of the fixed number
STANDBY  =0;
TRANSMIT =1;
COLLISION=2;
PERMIT   =3;
% definition of tne protocol
protocol ={'paloha' ... % pure ALOHA     : pno=1
           'saloha' ... % Slotted ALOHA  : pon=2
           'npcsma' ... % np-CSMA        : pon=3
           'sapisma'... % Slotted np-ISMA: pon=4
           };
% definition of communication channel
brate =512e3;           % bit rate
Srate =256e3;           % symbol rate
Plen  =128;             % length of a packet
Dtime =0.01;            % normalized propagation delay
alfa  =3;               % decline fixed number of propagation loss
sigma =6;               % standard deviation of shadowing [dB]
% definition of the access point
r =100;                 % service area radius [m]
bxy =[0,0,5];           % position of the access terminals{x,y,z}[m]
tcn =10;                % capture ratio [dB]
% definition of the access terminals
Mnum =100;              % number of the access terminal
mcn  =30;               % C/N at the access point when transmitted from area edge
% simulation condition
pno=3;                  % protocol number
capture=1;              % capture effect  0:nothing
                        %                 1:consider
spend=10000;            % number of packets that simulation is finished
outfile='test.dat';     % result output file name

Ttime =Plen/Srate;      % transmission time of one packet
mpow =10^(mcn/10)*sqrt(r^2+bxy(3)^2)^alfa;  
                        % true value of C/N
fid = fopen(outfile,'w');
fprintf(fid,'Protocol                  = %d\n',pno);
fprintf(fid,'Capture                   = %d\n',capture);
fprintf(fid,'Normalize_delay_time      = %f\n',Dtime);
fprintf(fid,'Bit_rate           (bps)  = %d\n',brate);
fprintf(fid,'Symbol_rate        (sps)  = %d\n',Srate);
fprintf(fid,'Length_of_Packet(sbl)     = %d\n',Plen);
fprintf(fid,'Nunber_of_mobile_station  = %d\n',Mnum);
fprintf(fid,'Transmission_power (C/N)  = %f\n',mcn);
fprintf(fid,'Capture_ratio      (dB)   = %f\n',tcn);
fprintf(fid,'Number_of_Packet          = %d\n',spend);

fprintf('\n*********Simulation Start*********\n\n');
if capture==0
    fprintf('%s without capture effect\n\n',char(protocol(pno)));
else
    fprintf('%s with capture effect\n\n',char(protocol(pno)));
end
mxy =position(r,Mnum,0);        % positioning of the access terminals
randn('state',sum(100*clock));  % resetting of the random table
mrnd =randn(1,Mnum);            % decision of the shadowing
for G=[0.1:0.1:1,1.2:0.2:2]     % offered traffic
    if G >= Mnum
        break
    end
    Tint = -Ttime/log(1-G/Mnum);% expectation value of the packet generation interval
    Rint=Tint;                  % expectation value of the packet resending interval
    Spnum=0;
    Splen=0;
    Tplen=0;
    Wtime=0;
    
    now_time=feval(char(protocol(pno)),-1);     %initialize of the access terminals
    while 1
        next_time=feval(char(protocol(pno)),now_time);
        if Spnum >=spend
            break
        end
        idx=find(Mstate==TRANSMIT|Mstate==COLLISION);
        if capture==0                           % without capture effect
            if length(idx) > 1
                Mstate(idx)=COLLISION;          % collision occurs
            end
        else
            if length(idx) > 1
                dxy =distance(bxy,mxy(idx,:),1);% calculation of the distance
                pow =mpow*dxy.^-alfa.*10.^(sigma/10*mrnd(idx));
                [maxp no]=max(pow);
                if Mstate(idx(no))==TRANSMIT
                    if length(idx)==1
                        cn=10*log10(maxp);
                    else
                        cn=10*log10(maxp/(sum(pow)-maxp+1));
                    end
                    Mstate(idx)=COLLISION;
                    if cn >= tcn                 % received power larger than capture ratio
                        Mstate(idx(no))=TRANSMIT;% transmitting success
                    end
                else
                     Mstate(idx)=COLLISION;
                end
            end
        end
        now_time=next_time;                      % time is advanced until the next state
                                                 % change time
    end
traffic=Tplen/Srate/now_time;                    % calculation of the traffic
ts=theorys(pno,traffic,Dtime);          % calculation of the theory value of the throughput
fprintf(fid,'%f\t%f\t%f\t%f\t%f\t%f\t%f\n',G,now_time,Splen/Srate,Tplen/Srate,Wtime,Tint,Rint);
fprintf('G=%f\tS=%f\tTS=%f\n',traffic,Splen/Srate/now_time,ts);
end
fprintf('\n*********Simulation End*********\n\n');
fclose(fid);
graph(outfile);

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