_DBPSK.rar_Binary Differential_dbpsk

%% 802.11b 1Mbps PHY link. % This M code simulates DBPSK modulation and barker code spreading % on a perfectly synchonized 802.11b link. It calculates the BER % rate at each EsNo (EbNo) and plots the result. %% Simulation parameters % For each BER loop, we specify the number of packets to transmit, the packet size and % the range of channel EsNo values to test. EsNoRange=[0:1:10]; % Range of noice levels to calculate BER NumPackets=2; PacketSizeBytes=1024; PacketSizeBits=PacketSizeBytes*8; % Here we ignore preamble and sync bits clear BERResults; %% System parameters and constants % Specify a number of system constants. % Spreading parameters Barker=[1 -1 1 1 -1 1 1 1 -1 -1 -1]'; % Barker sequence SpreadingRate=length(Barker); % Spreading rate % Upsampling rate SamplesPerChip=8; % Filter order and coefficients - root raised cosine FilterOrder=40; % Set to multiple of SamplesPerChip to make delay calculation easy h=firrcos(FilterOrder,7e6,.7,88e6,'rolloff','sqrt',FilterOrder/2,kaiser(FilterOrder+1,1)); %% Delay calculation % Calclate (specify) the net number of bits delay in the link due % to the filtering. % % * samples_delay = 2 filters x (40 coeffs / 2) = 40 samples % * chips_delay = sample_delay/SamplesPerChip = 40/8 = 5 chips % * Must recalculate delay if you change any of these parameters % We must delay the signal 6 more chips to align it with the 11 chip % boundary. This results in an 11 chip delay or one symbol/bit delay. % You must recalculate total and additional delay if you change any of these % parameters BitDelay=1; ChipDelayAdd=6; %% Main BER loop % Calculates the BER for each EsNo level. NumEsNos=length(EsNoRange); disp(' ');disp('Start Simulation'); for EsNoIndex =1:NumEsNos EsNo=EsNoRange(EsNoIndex); disp(['Simulating: EsNo=' num2str(EsNo) 'dB']); SNR=EsNo+10*log10(1/SpreadingRate)+10*log10(1/SamplesPerChip); % Initialize system and simulation measurements state % Bits TotalBits=logical(0); % Bit count for BER calculation ErrorBits=logical(0); % Error count for BER calculation LastTxSymbol=1; % Set DBPKS Modulator state LastRxSymbol=1; % Set DBPKS Demodulator state % Filters Rx_chips_delayed_store=zeros(ChipDelayAdd,1); Tx_bits_delayed_store=logical(zeros(BitDelay,1)); Tx_Filter_State=h(1:end-1); % Fill filter with a +1 symbol Rx_Filter_State=h(1:end-1); % Fill filter with a +1 symbol % Main simulation loop % Each packet is transmitted, and the recieved bits compared with the % transmitted bits to calculate the BER. for Packet=1:NumPackets % Construct frame of bits Tx_bits=rand(PacketSizeBits,1)>.5; % Random bits % Modulate Tx_bits_bp=(1-2*Tx_bits); % Convert to bipolar 0,1 --> 1, -1 Tx_symbols=LastTxSymbol*cumprod(Tx_bits_bp); % New DBPSK symbol = previous * 1 or -1 LastTxSymbol=Tx_symbols(end); % Store modulator state (last symbol) % Spread symbols with Barker code, upsampling by spreading rate Tx_chips=reshape(Barker*Tx_symbols',[],1); % Multiply by barker and reshape to a columm Tx_chips=complex(Tx_chips); % Make complex to ensure correct baseband transmission % Upsample chips by SamplesPerChip factor Tx_samples=zeros(length(Tx_chips)*SamplesPerChip,1); % Create empty Tx_samples Tx_samples(1:SamplesPerChip:end,1)=sqrt(SamplesPerChip)*Tx_chips; % Normalize power due to upsampling % Tx Filter [Tx_samples_filtered,Tx_Filter_State]=filter(h,1,Tx_samples,Tx_Filter_State); % Filter Tx_samples_filtered=Tx_samples_filtered*2.495; % Set output power to 1W var(Tx_samples_filtered); % Calculate Tx signal power, view by removing ';' % Transmit though AWGN Channel assuming 0dBW input power (check % with line above) Rx_samples_unfiltered = awgn(Tx_samples_filtered,SNR,0); % Rx Filter [Rx_samples_filtered,Rx_Filter_State]=filter(h,1,Rx_samples_unfiltered,Rx_Filter_State); % Downsample - sample chips Rx_chips=Rx_samples_filtered(1:SamplesPerChip:end); % Add 1 chip delay to move signal to 11 chip boundary Rx_chips_delayed=[Rx_chips_delayed_store; Rx_chips(1:end-ChipDelayAdd)]; Rx_chips_delayed_store=Rx_chips((end-ChipDelayAdd+1):end); % Store delayed chips % Despread - sample symbol Rx_symbols=Barker'*reshape(Rx_chips_delayed,SpreadingRate,PacketSizeBits); % Multiply by Barker Rx_symbols=Rx_symbols(:)/SpreadingRate; % Make a column and normalize % Demodulate Rx_symbols_plus_last=[LastRxSymbol; Rx_symbols]; Rx_symbols_plus_last_mult=Rx_symbols_plus_last(1:end-1).*conj(Rx_symbols_plus_last(2:end)); Rx_bits=Rx_symbols_plus_last_mult < 0; LastRxSymbol=Rx_symbols(end); % Demodulator state % Calculate BER % Add BitDelay to Tx signal to align with Rx signal Tx_bits_delayed=[Tx_bits_delayed_store; Tx_bits(1:end-BitDelay)]; Tx_bits_delayed_store=Tx_bits(end-BitDelay+1:end); % Store delayed symbol if Packet==1 % Ignore delayed bits on first packet TotalBits=TotalBits+length(Rx_bits)-BitDelay; ErrorBits=ErrorBits+sum(Tx_bits_delayed(BitDelay+1:end)~=Rx_bits(BitDelay+1:end)); else TotalBits=TotalBits+length(Rx_bits); % Calculate total bits ErrorBits=ErrorBits+sum(Tx_bits_delayed~=Rx_bits); % Compare Tx and Rx bits end end BERResults(EsNoIndex)=ErrorBits/TotalBits; % Calculate BER end %% Plot BER Results % Plot the BER results Vs EsNo. semilogy(EsNoRange,BERResults,'*-'); grid; title('802.11b 1Mbps DBPSK BER'); ylabel('BER') xlabel('EsNo');