packet_sim.m

source Matlab traites the UWB

%
%
clear all, close all;
%
% Necessary path
addpath ../rng;
addpath ../util;
addpath ../pulse;
addpath ../receiver;
addpath ../data_signal;
addpath ../reed_solomon;
addpath ../../src/channel;
addpath ../../src/scrambling_timehopping;


% Simulation parameters
PLOT_DEBUG = 0;
FS_CONT = 12e9;
RSCODE  = 1;
if RSCODE == 1
  DATA_LENGTH = 870
  fullblock = floor(DATA_LENGTH/330);
  PACKET_LENGTH = fullblock*378 + (DATA_LENGTH-fullblock*330) + 48;
else
  DATA_LENGTH = 127*8;
  PACKET_LENGTH = DATA_LENGTH;
end
% Physical layer
TC = 2e-9; % Chip length in seconds
%BURST_LENGTH = 4; % LPRF, in chip
BURST_LENGTH = 16; % HPRF, in chip
SYMBOL_LENGTH = 512; % In chip
% Multipath channel
CH_MODEL = 1;
CH_ATT_THLD_DB = 30; %rays with bigger attenuation are considered 0
CH_RNG_SEED = sum(100*clock);

%group all the parameters corresponding to the channel
channel_p = group_channel_params(CH_RNG_SEED,CH_MODEL,CH_ATT_THLD_DB,0.5,1e-9);


% Receiver
T_INT = 1e-9;
N_INT = 1;
channel_mask       = ones(1,50);
channel_mask_unit  = T_INT*N_INT;

t0 = clock;

% Get the data signal of interest
[burst, ths, compound_channel, ...
 samples_per_symbol, samples_per_burst, Ls] ...
    = init_data_signal(FS_CONT, PACKET_LENGTH, TC,BURST_LENGTH,SYMBOL_LENGTH, ...
                       channel_p);


[rx_data  data_bit, symbol_start, signal_start] ... 
    = get_data_signal(PACKET_LENGTH, ...
                      samples_per_burst, samples_per_symbol, Ls, ...
                      burst, ths);


if(PLOT_DEBUG)
    figure;
    plot(rx_data);
    hold on;
    samples_per_chip = TC * FS_CONT;
    samples_per_burst = samples_per_chip*BURST_LENGTH;
    samples_per_symbol = samples_per_chip*SYMBOL_LENGTH;
    burst_start = cumsum(ones(1,PACKET_LENGTH*SYMBOL_LENGTH/BURST_LENGTH)* ...
                         samples_per_burst)-samples_per_burst;
    plot(burst_start,zeros(1,length(burst_start)),'.g');
    symbol_start = cumsum(ones(1,PACKET_LENGTH)*samples_per_symbol) - ...
        samples_per_symbol;
    plot(symbol_start,zeros(1,length(symbol_start)),'*m');
    plot(signal_start,zeros(1,length(signal_start)),'*r');
    hold off;
end

% Add AWGN


% Receiver
% Get the signal only where necessary
burst_start_0 = symbol_start + ths*samples_per_burst;
burst_start_1 = burst_start_0 + (samples_per_symbol/2);

% Energy detection receiver and decoding
if isempty(channel_mask)
  n = Ls-rem(Ls,T_INT*FS_CONT*N_INT);
else
  n = round(length(channel_mask)*channel_mask_unit*FS_CONT);
end


signal_idx_0 = repmat(burst_start_0,n,1)+repmat((0:n-1)',1,PACKET_LENGTH) + 1;
signal_idx_1 = signal_idx_0 + samples_per_symbol/2 + 1;

if(PLOT_DEBUG)
  figure;
  subplot(2,1,1);
  plot(rx_data(reshape(signal_idx_0,1,PACKET_LENGTH*n)));
  subplot(2,1,2);
  plot(rx_data(reshape(signal_idx_1,1,PACKET_LENGTH*n)));
  disp(data_bit);
end

% Energy receiver
[rx_down_0,samples_per_tint] = ed_receiver(rx_data(reshape(signal_idx_0,1, ...
                                                  PACKET_LENGTH*n)),T_INT, ...
                                           FS_CONT,N_INT,-1);
[rx_down_1,samples_per_tint] = ed_receiver(rx_data(reshape(signal_idx_1,1, ...
                                                  PACKET_LENGTH*n)),T_INT, ...
                                           FS_CONT,N_INT,-1);

if(PLOT_DEBUG)
  figure;
  subplot(2,1,1);
  plot(rx_down_0);
  subplot(2,1,2);
  plot(rx_down_1);
end

% Decision rule and detection
rx_down = sum(reshape((rx_down_0 - rx_down_1), ...
                      n/(T_INT*FS_CONT),PACKET_LENGTH),1);

idx_dec0 = find(rx_down>0);
idx_dec1 = find(rx_down<0);
idx_unknown = find(rx_down==0);

demod_bit = [];
demod_bit(idx_dec0) = 0;
demod_bit(idx_dec1) = 1;
demod_bit(idx_unknown) = round(rand(1,length(idx_unknown)));

if RSCODE == 1
  % RS decoding
  dec_bit = rs_decoder_154a(demod_bit);
else
  dec_bit = demod_bit;
end
% Compute the BER
[num_err,ber_sim] = symerr(data_bit,dec_bit);

dt=etime(clock,t0);
fprintf('(dt = %.2f), ber = %.4f\n',dt,ber_sim);