ds-cdma in matlab (code implementation)

[debeelab]

Help pls! am working on ds-cdma project i'm new to matlab can any one pls help with the simulation of ds-cdma. I have gone through the communications toolbox and signal processing toolbox examples in matlab, i'm still not sure which of these two components or is it possible to incorporate both component to simulate the ds-cdma.

 

[Communications_Engineer]

first try to understand how ds-cdma works and how its tx and rx are designed before simulating it

 

[debeelab]

Re: ds-cdma MUD in matlab(code implementation)

Thanks for your response, Yes i do understand the modulation and demodulation of ds-cdma, the problem is how do i implement this in matlab. Please if you have any previous work or experience in ds-cdma multiuser detection i won't mind you send it by mail to me.

 

[Communications_Engineer]

Yes, I have experience of ds-cdma simulation in Matlab and beyond, but I cannot "send" it to you.

However, first implement ds-cdma SUD with multiple users and then go through the book of verdu (MUD)

You only have to implement the equations given in that book

I'm here to guide you

 

[assadabbasi]

Hellooo,

Mr. Communication Engineer,

can you help me in implementing DS-CDMA in MATLAB. I have written a code that works perfectly when there is no noise. But when I add AWGN then the results are not appropriate. if you can guide me, then i'll discuss my code with you.

waiting for your reply.

Thanks

 

[debeelab]

Hey check this out Ds-Cdma

 

[assadabbasi]

Dear debeelab,

Thanks for your reply and sharing the code. In your code you are using carrier. I just want to simulate simple DS-CDMA for BPSK in AWGN channel. I have written a code and i can decode signals for different users when there is no noise. I am simulating for 8 users and using Walsh code. Now when I simulate using AWGN channel, the problem is that when there are all the eight users and when there are less users (say 1, 2 or 3 etc.) present in the system, the BER curve is the same. But it should give better BER performance when there are less users as compared to the all 8 users. I know I am doing some mistake in decoding after noise addition but I don't know what is that mistake. I am attaching my code also, if you or someone else can help me in decoding the signal properly, I'll be thankful to you.

Please if anyone can help me understand this concept!!!!

Thanks

 

[lsight]

Dear debeelab,

Thanks for your reply and sharing the code. In your code you are using carrier. I just want to simulate simple DS-CDMA for BPSK in AWGN channel. I have written a code and i can decode signals for different users when there is no noise. I am simulating for 8 users and using Walsh code. Now when I simulate using AWGN channel, the problem is that when there are all the eight users and when there are less users (say 1, 2 or 3 etc.) present in the system, the BER curve is the same. But it should give better BER performance when there are less users as compared to the all 8 users. I know I am doing some mistake in decoding after noise addition but I don't know what is that mistake. I am attaching my code also, if you or someone else can help me in decoding the signal properly, I'll be thankful to you.

Please if anyone can help me understand this concept!!!!

Thanks

Added after 1 minutes:

in fact you use walsh code which make different users orthogonal(condition on synchronization),so no matter there are 1,2,3 users of 8 users in system,multipe user interface have no effect on the intended user,and the ber keep constant

1 try to lose the synchronization for different user then you could see multipe interface

2 try to lower the snr of the channel then you could see ber do change

 

[osam/]

Hi helpful

could u plz help me,,i have tried to simulate the ds-cdma using matlab, but the the erro make me crazy

could u have a look for the attached file and tell me what can i do to run smoothly.

best regards

 

[fatimak_415]

can some one correct my code