Ruotong and I started the weekly project in the meeting room with our superviser as usual. Firstly, we presented the results that we had obtained in last week, mainly was about the matlab code for the signal simulations, which will be discussed in details in the next paragraph. After that, we admitted that we had met some problems and asked Dr. Zhu for help. Our great superviser gave us the answer immediately, and she explained the reasons to us very carefully. When we understood her explanation, we found that there was one step missed, and that's one of most important points in this experiment. Before recovering the signals, all of the chips should be added up and according to the properties of positive or negative, the signals could be recovered perfectly. If this step is missed in the simulation, then a high ratio of error would be happened.
An m-sequence generator is designed by us in the matlab, meanwhile, the original signal is given randomly. Since we designed the project for four users, so the related data was calculated by us and added into the code. If more users would use this project, then the Walsh code would be used, that is to say, our simulation could be applied to numerous users (the maximum is 32). Every chip of the original signal will be multiplied by the whole PN code, in this way, the spectrum is expanded. When it comes to the recovering step, the reciced signal will be multiplied by the ON code again, and then all of the chips should be added up and according to the properties of positive or negative.
However, we did not take the white noise into consideration this week, so what we are going to do in next week is to put the AWGN noise signal into the matlab code. Fortunately, Dr. Zhu e-mailed us a relevant matlab code, we could take it as a reference. Our project may be finined in next week.
No comments:
Post a Comment