gusucode.com > wlan工具箱matlab源码程序 > wlan/wlanexamples/vhtBeamformingNoiseVariance.m
function noiseVar = vhtBeamformingNoiseVariance(noisePower,cfgVHT) % vhtBeamformingNoiseVariance returns the noise variance after OFDM % demodulation for a given noise power. % % NOISEVAR = vhtBeamformingNoiseVariance(NOISEPOWER,CFGVHT) returns the % nosie variance after OFDM demodulation for a given noise power, % NOISEPOWER, and VHT format configuration object, CFGFORMAT. % % NOISEPOWER is the noise power applied to each receive antenna in dBW. % % CFGVHT is the format configuration object of type <a href="matlab:help('wlanVHTConfig')">wlanVHTConfig</a>. % Copyright 2015-2016 The MathWorks, Inc. %#codegen % An estimate of the noise power after OFDM demodulation is required to % perform MMSE equalization on the received OFDM symbols. The noise % variance after demodulation is calculated and is used during field % recovery. The noise variance after OFDM demodulation in VHT fields is a % scaled version of the applied noise power. This scaling accounts for: % % * The noise energy in unused subcarriers which are removed during % demodulation % * Scaling by the number of space-time streams during demodulation % Get the number of occupied subcarriers in VHT fields ofdmInfo = wlan.internal.wlanGetOFDMConfig(cfgVHT.ChannelBandwidth,'Long','VHT'); Nst = numel(ofdmInfo.DataIndices)+numel(ofdmInfo.PilotIndices); % Calculate VHT noise variance noiseVar = 10^(noisePower/10)*cfgVHT.NumSpaceTimeStreams*(Nst/ofdmInfo.FFTLength); end