移动无线信道COS207模型MATLAB程序

% Retrieve the power delay spectrum P(tau), the impulse response h(tau,t) % and the transfer function H(f,t) of a sample COST-207 mobile channel % using the "Gaussian Stationary Uncorrelated Scattering" (GSUS) % stochastic channel model by Schulze/Hoeher. % % function [PDS_out, h_out, tau_out, C207par, H_out, f_Ts_out] = ... % GSUS (mPDS, N_echo, fs, fDmax, tau_M, g_Ta, ... % [t_fs, [tau_axis, [f_axis [, verbose[, ch_name[, rseed]]]]]]) % ---------------------------------------------------------------------- % INPUT: % ---------------------------------------------------------------------- % mPDS : String designating the desired transmission environment, % i.e. the physical channel, according to COST-207: % - 'TU': "Typical Urban" (non-hilly urban environment), % - 'RA': "Rural Area" (non-hilly rural environment), % - 'BU': "Bad Urban" (hilly urban environment), % - 'HT': "Hilly Terrain" (hilly rural environment). % Note: These environments correspond to different mean power % delay spectra (PDS, "Verzoegerungsleistungsspektren"). % N.B.: To obtain non-standardized environments, see "COST207.m". % N_echo : Desired number of echo paths. Example: N_echo=100. % fs : Symbol frequency in baud (=> Symbol period: Ts=1/fs). % Ex.: fs=13e6/48=270833 (GSM); fs=1228800 (QualComm-CDMA). % fDmax : Maximum Doppler frequency fDmax := v*f0/c0, where % - v is the speed in m/s of the mobile unit % - f0 is the carrier frequency in Hertz % - c0=3e8 is the speed of light in m/s in empty space. % tau_M : Oversampling factor determining the sampling period on the % tau axis: Ta = Ts/tau_M, where Ts is the symbol period. % N.B.: The continuous echo delay times are also quantized to fit % a Ta-spaced delay time grid. % g_Ta : Impulse response g(tau) sampled at tau=n*Ta of a band- % limiting filter. This may either be the receive filter or % -- for linear modulation schemes -- the overall filter com- % posed of transmit and receive filter (refer to "get_gTR.m"). % N.B.: For linear modulation, fDmax << 1/L_gTx must be satisfied, % where L_gTx is the transmit filter's length, because other- % wise, g_Ta is not simply the convolution of the transmit % and receive filter impulse responses. % [t_fs] : Vector giving the time instants t in multiples of Ts, % where the impulse response h(tau,t) will be evaluated. % To retrieve a single slice of the impulse response, set % t_fs to a scalar value. To cover a t-range of D Doppler % periods 1/fDmax, choose e.g. t_fs=((0:D/39:D)/fDmax)*fs. % Default value is: t_fs=((0:1/40:1-1/40)/fDmax)*fs. % [tau_axis]: The tau output range is determined by these two relative % factors used to suppress outputs close to zero. The 1st % [2nd] factor gives a percentage of how many symbol periods % are to be appended to the tau axis BEFORE min{tau} [AFTER % max{tau}]. Thus, setting tau_axis=[0 0] yields very tight % bounds, while the max. tau range is obtained by [1.0 1.0]. % Default value is tau_axis=[0.3 0.2]. % [f_axis]: Optional two-element vector determining the range and re- % solution of the frequency axis for the transfer function: % - f_axis(1): norm. freq. (must be <= tau_M) used to deter- % mine the frequency range: |f|<= f_axis(1)/(2Ts). The va- % lue 1.0 [2.0] corresponds to the Nyquist [symbol] freq. % - f_axis(2) is the desired number of FFT points in each % frequency interval with length 1/Ts. % Default value is f_axis = [min(1.5,tau_M), 128]. % [verbose]: Optional vector determining the kind of info given: % verbose(1)==1: print warnings only (default) % ==2: print warnings and info % verbose(2)==1: draw random parameters % verbose(3)==1: draw power delay spectrum P(tau) % verbose(4)==1: draw magn. impulse response |h(tau,t)| % verbose(5)==1: draw magn. transfer function |H(f,t)|, % where H(f,t) := F{h(tau,t)} w.r.t. tau % [ch_name]: Optional string for the figure titles designating the ch.: % Default value is 'COST207-<mPDS> channel' (if isstr(mPDS)). % [rseed] : If this parameter is given, rseed is used to set the % seeds for the random numbers generator. In this way, % the mobile channel's parameters can be reproduced. % ---------------------------------------------------------------------- % OUTPUT: % ---------------------------------------------------------------------- % PDS_out : Length N column vector containing a sample power delay % spectrum (PDS) P(tau) for tau = n*Ta. To obtain the symbol % rate sampled PDS, use PDS_out(1:tau_M:length(PDS_out)). % Note: N = L*tau_M+1, where L is an integer depending on tau_axis. % N.B.: If tau_axis==[1.0 1.0], the following is exactly true: % sum(PDS_out)/tau_M = sum(abs(g_Ta).^2)/tau_M, i.e. the ex- % pected mean power amplification of the GSUS channel is one, % if and only if the power amplification of g(tau) is unity. % h_out : (N x length(t_fs)) matrix with a sample impulse response % h(tau,t) of the selected time-variant COST207 channel. % Each column contains one slice h(tau,t0) where the tau % axis is sampled at tau=n*Ta=n*Ts/tau_M and t0 is fixed. % Conversely, each row represents one channel coefficient % h(tau0,t) sampled at t=t_fs*Ts for a fixed value tau0. % Note: Use h_out(1:tau_M:size(h_out,1),:) to obtain the % corresponding symbol rate impulse response. % N.B.: For tau_axis==[1.0 1.0], the GSUS channel has an expected % mean power amplification equal to sum(abs(g_Ta).^2)/tau_M. % However, the actual mean power amplification of h_out % will differ from this value as long as length(t_fs)~=inf. % tau_out : Length N column vector with the normalized time delay axis % tau_out=tau*fa=tau/Ta for use with graphics commands. % C207par : "COST207.m" outputs. The 1st column contains the quantized % and shifted echo delay times in multiples of Ts, the 2nd col. % the norm. Doppler frequencies and the 3rd col. the phases. % H_out : (NFFT x length(t_fs)) matrix with a sample transfer func- % tion H(f,t) of the selected time-variant COST207 channel. % Each column contains one slice H(f,t0) of the transfer % function for a fixed value of t0. Conversely, each row re- % presents the rate of change of each coefficient H(f0,t). % f_Ts_out : Length NFFT column vector with the normalized freq. axis % -f_axis(1)/2Ts<=f<f_axis(1)/2Ts for use with graphics cmds. % ---------------------------------------------------------------------- % PREREQUISITES: % ---------------------------------------------------------------------- % Required functions: "COST207.m" % ---------------------------------------------------------------------- % REFERENCES: % ---------------------------------------------------------------------- % - H. Schulze: "Stochastische Modelle und digitale Simulation von Mobil- % funkkanaelen", Kleinheubacher Berichte, Vol.32, pp 473-483, 1989. % - P. Hoeher: "A Statistical Discrete-Time Model for the WSSUS Multipath % Channel", IEEE Trans. on Veh. Technol, Vol.41, no.4, pp 461-468, 1992. % ---------------------------------------------------------------------- % AUTHOR: Marcus