The word dissolves in Paragraph 4 refers to ______.A.collapseB.convokeC.meltD.terminate
The word dissolves in Paragraph 4 refers to ______.
A.collapse
B.convoke
C.melt
D.terminate
The word dissolves in Paragraph 4 refers to ______.
A.collapse
B.convoke
C.melt
D.terminate
B.products that are made from fossil fuels
C.factors that stop the climate change
D.changes that happen after the temperatures rise
B.birds which sing early in the morning
C.people who like to stay up late at night
D.people who are early to rise in the morning
A、course book
B、college lecture
C、user manual
D、experiment report
B.His daily striving
C.His superhuman will
D.His irresistible energy
Write MATLAB codes to implement DSSS system sinmulation, The system is a 2-user system with a 2-path frequency selective fadingchannel for each user, The power for each path is half the total transmit power for each user. A RAKR receiver with ideal channel estimation should be used in the receiver for each user. The relative delay between two paths is 1 chip. BPSK modulation is assumed. The BER-versus SNR curve should be drawn for both users. The SNR is defined by, and is assumed to change from 0 dB to 10 dB with step 1 dB. The simulation results should be compared with the theoretical BER versus SNR curve in flat Rayleigh fading channel.
A、N_Trials=300; N_number=100; N_snr=10; N_users=2; N_path=2; Delay=1; Q=16; N_samples=N_number*Q; E_M=0; for trials=1:N_Trials trials noise=randn(N_users.*N_path,Q*N_number)+j.*randn(N_users*N_path,Q*N_number); s10=round(rand(N_users,N_number)); ss_user=s10*2-1; % without consideration of delayed path pn01=round(rand(N_users,Q)); pn=(pn01.*2-1)./sqrt(Q); S_spread=[]; for user=1:N_users s=kron(ss_user(user,:), pn(user,:)); S_spread=[S_spread; s]; end S_multipath=[]; for user=1:N_users s_user=S_spread(user,:); Suser_delayed=[zeros(1,Delay), s_user(1,1:(N_samples-Delay))]; S_multipath=[S_multipath; [s_user;Suser_delayed]]; end %___________the following is to generate Rayleigh fading coefficients N=N_users.*N_path; fad_c=fading(8,0.005,N_samples, N); fad=fad_c.'; % only use the amplitude; %phase is not used, which is equivalent to have an ideal phase %compensation by using channel equalization S_spread=S_multipath.*fad; %S_spread is the signal matrix of size users x N_number sgma=1; Error_M=[ ]; for snr_db=0:1:N_snr snr=10.^(snr_db./10)/2; %Evaluate the SNR from SNR in dB N0=2*sgma.^2; Eb=snr.*N0; yy=sqrt(Eb./2)*S_spread+noise; %received spread signals in the baseband Error_v_user=[]; for user=1:N_users y_path1=yy((user-1).*N_path+1, :); y_path_temp=yy((user-1).*N_path+2, :); y_path2=[y_path_temp(1,Delay+1:N_samples), zeros(1,Delay)]; Y_M_path1=[ ]; Y_M_path2=[]; for k=1:N_number ym1=y_path1(1,(k-1)*Q+1:k*Q); ym2=y_path2(1,(k-1)*Q+1:k*Q); Y_M_path1=[Y_M_path1;ym1]; Y_M_path2=[Y_M_path2;ym2]; end % Y_M is a matrix of size N_number x Q, each row correspinding to a % BPSK symbol ys=Y_M_path1*pn(user,:).'+Y_M_path2*pn(user,:).'; %despreading for a user y=ys.'; y_real=real(y); s_e=sign(y_real); s_e10=(s_e+1)./2; Error_snr=sum(abs(s10(user,:)-s_e10)); Error_v_user=[Error_v_user;Error_snr./N_number]; %A BER collumn vector for all the users and for each snr end %for user Error_M=[Error_M,Error_v_user]; %BER matrix for all users and for all the SNRs end % end for snr E_M=E_M+Error_M ; end % end for trials BER=E_M./N_Trials; BER_T=[ ]; for snr_db=0:1:N_snr snr=10.^(snr_db./10); temp=sqrt(snr./(1+snr)); BER_THEROY=(1-temp)/2; BER_T=[BER_T,BER_THEROY]; end i=0:1:N_snr; semilogy(i,BER(1,:),'-r',i,BER(2,:),'ob',i,BER_T ,'*g'); xlabel('E_b/N_0(dB)') ylabel('BER') legend('User1 RAKE','User2 RAKE', 'Theoretical flat fading');
B、no need
C、no need
D、no need
A.avian influenza
B.pneumonia
C.cardiopathy
D.tuberculosis
A.The invitations business people receive from their colleagues.
B.Three cups of tea or coffee are presented in offices and during social calls.
C.Business people connect with tangibles and colleagues exchange presents.
D.Visitors needn"t take flowers or other unusual delicacies.
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