hdl implementation of wlan receiver -凯发k8网页登录

model architecture

open the wlanhdlreceiver model to run the example. this figure shows the high-level overview of a wlan receiver model.

modelname = 'wlanhdlreceiver';
open_system(modelname);

time and frequency synchronization

the time and frequency synchronization subsystem performs receiver filtering and coarse time and frequency estimation and corrections on the filtered signal. then, the subsystem fine tunes the time and frequency estimation and corrections to remove any residual offsets. the wlanhdlreceiverinit.m file initializes filter coefficients.

open the wlantimeandfrequencysynchronization subsystem to see the synchronization process.

open_system([modelname '/wlanhdlreceiver/wlantimeandfrequencysynchronization'],'force');

ofdm demodulation

the ofdm demodulator block converts time-domain signals to frequency-domain subcarriers. the block provides the flexibility to change the orthogonal frequency division multiplexing (ofdm) parameters fft length, cyclic prefix length, number of left guard subcarriers, and number of right guard subcarriers during the runtime. in this example, based on bandwidth option, the cyclic prefix (cp) length varies for different fields in the wlan signal. for example, the first symbol of l-ltf uses a cp length of 32 or 64, the second symbol of the l-ltf uses a cp length of 0, and the remaining fields of the wlan signal uses a cp length of 16 or 32 for 20 mhz and 40 mhz, respectively. in this example, the fft length parameter is set to 64 for 20 mhz and 128 for 40 mhz and the number of left guard subcarriers and number of right guard subcarriers parameters are set to 4 and 3 for 20 mhz and 6 and 5 for 40 mhz, respectively.

open_system([modelname '/wlanhdlreceiver/ofdmdemodulation']);

the ofdmdemodulationparametercalculator matlab function controls the ofdm demodulator block parameters for different fields of the wlan packet. the ofdmdemodulationparametercalculator matlab function calculates the number of used subcarriers to determine the number of ofdm symbols in the wlan packet.

non-ht channel estimation and equalization

the nonhtchannelestandequalize subsystem is used for l-ltf channel estimation. the input is given to the ofdm channel estimator block. the ofdm channel estimator block implements least squares (ls) estimation for the channel estimation and performs averaging on the estimates from two l-ltf symbols of the wlan signal. the ofdm equalizer block uses the resultant averaged channel estimate to perform zero forcing (zf) equalization on data.

open_system([modelname '/wlanhdlreceiver/nonhtchannelestandequalize']);

ht or vht channel estimation and equalization

the htorvhtchannelestandequalize subsystem is similar to the nonhtchannelestandequalize subsystem. for a siso configuration, only one ht or vht ltf exists, so averaging is disabled in the ofdm channel estimator block.

open_system([modelname '/wlanhdlreceiver/ht_vhtchannelestandequalize']);

non-ht common phase noise estimation and correction

the nonhtcpeestandcorrection subsystem estimates the common phase noise or residual frequency offset for the non-ht portion of the wlan signal. cpe estimation requires references such as non-ht pilot positions, a non-ht pilot sequence, and pseudo-noise (pn) sequence as described in equation 17-25 in [ 1 ]. the wlanhdlrxinint.m script initializes these known references and stores them in 1-d lookup tables in the subsystem. the polaritygenerator subsystem gives the polarity of the pilots based on the symbol number. the reference pilots are multiplied with polarity for cpe estimation. the estimated cpe is averaged on all of the pilot subcarriers in an ofdm symbol and is used for the correction of data subcarriers of non-ht portion of the wlan packet.

open_system([modelname '/wlanhdlreceiver/nonhtcpeestandcorrection']);

ht or vht common phase noise estimation and correction

the htorvhtcpeestandcorrect subsystem is similar to the nonhtcpeestandcorrect subsystem. this subsystem performs cpe estimation and correction using ht or vht pilot positions and a ht or vht pilot sequence.

open_system([modelname '/wlanhdlreceiver/ht_vhtcpeestandcorrection']);

frame format identification and controller

to recover the signal and data field information from a wlan signal, you must use the wlan receiver frame format. this example supports non-ht, ht, and vht frame formats. the frameformatdetector subsystem detects the frame format as non-ht, ht, or vht by buffering 3 ofdm symbols after l-ltfs, at the output of the nonhtcpeestandcorrect subsystem. this flow chart describes the frame format detection. for more information, see [ 2 ].

the signal recovery subsystem decodes the mcs from the first symbol l-sig. if the mcs is not 0, the frameformatdetector subsystem detects the frame format as non-ht. if the mcs is 0, it checks the modulation scheme of ofdm symbol 2. if the modulation scheme of symbol 2 is qbpsk, the subsystem detects the format as ht. if the modulation scheme of symbol 2 is bpsk, it checks the modulation scheme of ofdm symbol 3. if the modulation scheme of symbol 3 is qbpsk, the subsystem detects the format as vht. if the modulation scheme of symbol 3 is bpsk, the subsystem detects the format as non-ht.

if the frameformatdetector subsystem detects frame format as non-ht, then the remaining ofdm symbols, including ofdm symbols 2 and 3, are treated as l-data. the frameformatcontroller subsystem passes the output of the nonhtcpeestandcorrect subsystem to the datarecovery subsystem to decode l-data.

if the frameformatdetector subsystem detects the frame format as ht or vht, the frameformatcontroller subsystem passes the output of the ht_vhtcpeestandcorrect subsystem to the datarecovery subsystem to recover ht-data or vht-data.

signal recovery

the signalrecovery subsystem recovers the header information to decode data bits from l-sig, ht-sig, and vht-sig fields. the output of the nonhtcpeestandcorrect subsystem corresponding to signal fields is streamed into the signalrecovery subsystem. the symbol demodulator block performs bpsk and qbpsk soft symbol demodulation on signal fields in the wlan packet. the channel decoding includes deinterleaver subsystem and viterbi decoder block.

the deinterleaver subsystem performs deinterleaving on the symbol demodulated data with a maximum block size of 48 and the number of columns as 16. the viterbi decoder block performs 1/2 rate viterbi decoding on deinterleaved data. for more information on the deinterleaver subsystem, see .

l-sig uses the parity to check the error in wlan l-sig field, whereas 8-bit cyclic redundancy check (crc) is used to check the error in the wlan ht-sig 1 and 2 and vht-sig-b field. the general crc syndrome detector hdl optimized block is used for crc error detection and paritycalculator subsystem performs parity calculation. if the crc checksum or parity fails, the signal field recovery returns the status of parity check or crc (pass or fail).

open_system([modelname '/wlanhdlreceiver/frameformatdetectionandsignalrecovery/signalbitrecovery']);

data recovery

the datarecovery subsystem uses the wlan signal fields to decode data bits. the registers are used to store wlan signal field information. these registers access the wlan signal field information. the symbol demodulator block performs soft-bit bpsk, qpsk, 16-qam, or 64-qam symbol demodulation associated with the modulation type retrieved from the wlan signal field information.

if the decoded wlan channel coding type is bcc, the deinterleaver and the bcc decoder subsystems perform deinterleaving and viterbi decoding on the symbol demodulated data. the deinterleaver subsystem consists of different deinterleavers for non-ht and ht or vht data. the deinterleaver for non-ht data is configured with a block size of 48 and number of columns as 16. the deinterleaver for ht or vht data is configured with a block size of 52 and number of columns as 13 for 20 mhz and a block size of 216 and number of columns as 18 for 40 mhz, respectively. the bcc decoder subsystem is equipped with depuncturer and viterbi decoder blocks. each code rate is assigned a predefined punctured vector pattern. based on the code rate retrieved from the wlan signal field information, the bcc decoder subsystem performs depuncturing followed by viterbi decoding.

if the decoded wlan channel coding is ldpc, the ldpctonedemapping subsystem in the dataselector subsystem performs the ldpc tone demapping for vht data before symbol demodulation. the ldpc decoder subsystem in this example decodes one ldpc codeword data. the ldpcparameterscalculator subsystem computes the required ldpc parameters such as the ldpc length, the number of payload bits, the number of shortened bits, and the number of punctured bits for the codeword. the ldpc codeword formation subsystem depunctures the symbol demodulated data to form one ldpc codeword using the ldpc parameters. the block decodes the depunctured data based on the codeword block length index and the code rate index.

the decoded bits are streamed through the descrambler subsystem.

open_system([modelname '/wlanhdlreceiver/datarecovery']);

file structure

this example uses one simulink models and three matlab files.

model inputs and outputs

the inputs and outputs to the example model are described below

verification and results

this example model accepts a wlan transmit waveform as an input along with valid and start signals. the model returns decoded information bits as an output along with a valid signal. the wlanhdlreceiverinit.m script provides the input to the model. for the demonstration of the example, the wlanwaveformgenerator.m function in the script generates the vht mode, 20 mhz bcc channel coded frame, which is passed through the tgac channel with a delay profile of model a. the additive white gaussian noise (awgn) at a 30 db signal-to-noise ratio (snr) is added to the transmit waveform with other channel impairments such as 20 khz cfo and a timing offset of 256. to verify the example for ldpc channel coding, set the channel coding parameter to ldpc on the input generation subsystem, and run the example.

fprintf('\n simulating wlan hdl receiver \n');
out = sim(modelname);
close_system(modelname,0);
fprintf('\n hdl simulation complete. data decoded. \n');

 simulating wlan hdl receiver 
 hdl simulation complete. data decoded. 

verify the outputs of this example using wlan toolbox™ functions. specify the same input waveform to the simulink model and to the matlab equivalent receiver. compare the outputs to validate the example.

fprintf('\n comparing wlan matlab reference receiver \n')
wlanhdlmatlabrxreference;
fprintf('\n matlab simulation complete. \n');
simout = squeeze(out.rxbits(out.rxbitsvalid));
errsig = (bitxor(logical(psdu),simout));
err = sum(errsig);
hconstdata = out.headerconstellation(out.headerconstellationvalid);
figure;
plot(hconstdata,'o');
xlabel('in-phase'); ylabel('quadrature')
title('equalized signal field constellation');
m = double(max(abs([real(hconstdata(:)); imag(hconstdata(:))])) * 1.1);
axis([-m m -m m]);
dconstdata = out.dataconstellation(out.dataconstellationvalid);
figure;
plot(dconstdata,'o');
xlabel('in-phase'); ylabel('quadrature')
title('equalized data field constellation');
m = double(max(abs([real(dconstdata(:)); imag(dconstdata(:))])) * 1.1);
axis([-m m -m m]);
figure;
plot(errsig);
xlabel('sample number');
ylabel('error magnitude');
legend('error')
title('error magnitude between simulink and matlab wlan receiver output');
if err == 0
    fprintf('\n simulink and matlab outputs match \n');
else
    fprintf('\n simulink and matlab outputs do not match  \n');
end

 comparing wlan matlab reference receiver 
 matlab simulation complete. 
 simulink and matlab outputs match 

hdl code generation and implementation results

to generate the hdl code for this example, you must have the hdl coder™ product. to generate hdl code and an hdl testbench for wlanhdlreceiver subsystem, use the makehdl and makehdltb commands. the resulting hdl code was synthesized for a xilinx® zynq® ultrascale rfsoc zcu111 evaluation board. the table shows the post place and route resource utilization results. the design meets timing with a clock frequency of 306 mhz for 20 mhz and 40 mhz bandwidth options.

f = table(...
    categorical({'clb lut'; 'clb registers'; 'ramb36'; 'ramb18';...
    'dsp48'}),...
    categorical({'99,978'; '94,294'; '262'; '10'; '323'}),...
    categorical({'1,02,237'; '96,758'; '266'; '14'; '351'}),...
    'variablenames',...
    {'resources','usage for 20 mhz', 'usage for 40 mhz'});
disp(f);

      resources      usage for 20 mhz    usage for 40 mhz
    _____________    ________________    ________________
    clb lut               99,978             1,02,237    
    clb registers         94,294             96,758      
    ramb36                262                266         
    ramb18                10                 14          
    dsp48                 323                351         

references