salmanpolito
commented
4 years ago Sorry, I think my query was very simple: I finally figured out how to do it. --> As mentioned in previous issues, RT-AC86U (or any other nexmon supported devices ) contains core for each antenna. there are four cores in RT-AC86U and hence supporting four antenna, 3 external and one internal. rsxx is the spatial streams received on each antenna. --> Unlike Atheros_CSI tool that extracts CSI in parallel at all antenna for each packet, Nexmon CSI is extracting it sequentially. for instance, by selecting core=3 and rsxx=0 (i.e. one stream), it will receive first packet on antenna 1, second on antenna 2 and 3rd on antenna 3 and will loop again for the subsequent packets. --> I noticed that the CSI was received very slow at my receiver AP, (I have used two RT-AC86U APs, one as transmitter and second as a receiver). The normal speed was around 40-50 Hz, and I required at least 1k packets. I, therefore, used iperf on a laptop connected to transmitter AP and transferred 100Gb file to the server. The packet rate increased significantly. --> I have done some minor changes in the MATLAB file, which I believe will help the new users to get the CSI stream from all antenna. I have done it for three antennas and one stream only. (please ignore the device orientation part) --> I am still looking forward to your insightful comments. clc clear all close all %% configuration CHIP = '4366c0'; % wifi chip (possible values 4339, 4358, 43455c0, 4366c0) BW = 80; % bandwidth FILE = './asus/static2'; % capture file NPKTS_MAX = 18000; % max number of UDPs to process
%% read file HOFFSET = 16; % header offset NFFT = BW3.2; % fft size p = readpcap(); p.open(FILE); n = min(length(p.all()),NPKTS_MAX); p.from_start(); csi_buff = complex(zeros(n,NFFT),0); k = 1; core=zeros(1,n); rxss=core; while (k <= n) f = p.next(); if isempty(f) disp('no more frames'); break; end if f.header.orig_len-(HOFFSET-1)4 ~= NFFT4 disp('skipped frame with incorrect size'); continue; end payload = f.payload; if length(payload)<NFFT break; end payloadbytes = typecast(payload ,'uint8'); core(k) = bitand(payloadbytes(56),3); rxss(k) = bitand(bitshift(payloadbytes(56),-3),3); H = payload(HOFFSET:HOFFSET+NFFT-1)'; if (strcmp(CHIP,'4339') || strcmp(CHIP,'43455c0')) Hout = typecast(H, 'int16'); elseif (strcmp(CHIP,'4358')) Hout = unpack_float(int32(0), int32(NFFT), H); elseif (strcmp(CHIP,'4366c0')) Hout = unpack_float(int32(1), int32(NFFT), H); else disp('invalid CHIP'); break; end Hout = reshape(Hout,2,[]).'; cmplx = double(Hout(1:NFFT,1))+1jdouble(Hout(1:NFFT,2)); csi_buff(k,:) = cmplx.'; time_stamp(k)=f.header.ts_sec; k = k + 1; end
% pilot Removal %https://www.oreilly.com/library/view/80211ac-a-survival/9781449357702/ch02.html % csi_buff(:,230:234)=[]; csi_buff(:,124:134)=[]; csi_buff(:,245)=[]; csi_buff(:,235)=[]; csi_buff(:,207)=[]; csi_buff(:,171)=[]; csi_buff(:,143)=[]; csi_buff(:,120:123)=[]; csi_buff(:,104)=[]; csi_buff(:,76)=[]; csi_buff(:,40)=[]; csi_buff(:,12)=[]; csi_buff(:,1:5)=[]; max_csi=max(core); if(max_csi==0) antenna_1=csi_buff(core==0,:); csi_data=[antenna_1]; elseif(max_csi==1) antenna_1=csi_buff(core==0,:); antenna_2=csi_buff(core==1,:); csi_data=[antenna_1,antenna_2]; elseif(max_csi==2) antenna_1=csi_buff(core==0,:); antenna_2=csi_buff(core==1,:); antenna_3=csi_buff(core==2,:); % time_stamp=time_stamp(core==2); % time_stamp=typecast(time_stamp,'double'); time_stamp=sort(time_stamp); if (length(antenna_1)~=length(antenna_2)~=length(antenna_3)) xx=min([length(antenna_1),length(antenna_2),length(antenna_3)]); antenna_1(xx:end,:)=[]; antenna_2(xx:end,:)=[]; antenna_3(xx:end,:)=[]; % time_stamp(xx:end)=[]; end csi_data=[antenna_1,antenna_2,antenna_3]/128; % fc = 80; % fs = 2312.5e3; % [b,a] = butter(6,fc/(fs/2)); % csi_data = filter(b,a,csi_data); else antenna_1=csi_buff(core==0,:); antenna_2=csi_buff(core==1,:); antenna_3=csi_buff(core==2,:); antenna_4=csi_buff(core==3,:); csi_data=[antenna_1,antenna_2,antenna_3,antenna_4]; end x=length(csi_data)1e-3; time_stamp=linspace(double(min(time_stamp)),double(max(time_stamp))+x*1e6,length(csi_data))'; ind1= find(time_stamp==0); time_stamp(ind1)=[];
% deivice orientation c=299792458; tx_loc=[0;0]; rx_loc=[1.5;0]; sample_rate=1000; xb=[0,1.5]; yb=[0,10]; carrier_frequency=5.785e9; save('D:\Widar2\exp\T05.mat','csi_data','time_stamp'); save('D:\Widar2\exp\device_config.mat','c','carrier_frequency','rx_loc','sample_rate','tx_loc','xb','yb');
fatihoezdemir
wen-young
zel602
Dr-Yongqiang
I think zel may want to ask the core values of the four antennas of the router. For example, in the figure, antenna 1 corresponds to the core = 0x0001? This is just an example, and I also want to know the correct answer.Thanks！ @DanielAW @derfalx @schmittner @qtux @Kjili
Hi @matthiasseemoo @jlinktu I am using the Nexmon_CSI on RT-AC86U. I am working on a passive sensing project. I want to get the CSI from all the available streams, so that I can sanitize it. Is it possible to get the CSI streams for all the four antenna simultaneously? I checked almost all the issues, but it seems that we have to manually change the Core "C" and "N" value and then we can get the CSI stream for that particular Antenna. Looking forward to hearing from you. Thanks in advance.