Performance investigation of iterative multiuser receiver for turbo-coded DS-CDMA | |
| Author | Vu Gia Huy |
| Call Number | AIT Thesis no.TC-01-12 |
| Subject(s) | Mobile communication systems Code division multiple access |
| Note | A thesis submitted in partial fulfillment of requirements for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. TC-01-12 |
| Abstract | Multiple access interference (MAI) is one of the factors that limits the capacity as well as the perfo1mance of direct sequence CDMA systems. Several effective techniques to combat this problem are code waveform design, power control, adaptive antennas, forward error control codes and multiuser detection. Combination of these ยท techniques would be more effective due to different advantages of each technique. A new technique; applying the principle of Turbo decoding for multiuser detection block and decoding block, illustrates the validity of this claim. Such multiuser detectors, called turbo multiuser detectors or iterative multiuser detectors, have attracted quite a lot attention of researchers. In this thesis, a low computational complexity iterative multiuser receiver is analyzed for a turbo-coded CDMA system. The receiver includes a soft multiuser detector and the decoders for users. The simulation considers an uplink asynchronous transmission over a correlated frequency selective fading channel. The results show that the performance of the receiver approaches the single user performance after only two iterations. Compared with the two-stages/decoder scheme, the performance of iterative multiuser receivers is improved significantly. This improvement illustrates the effect of combined decoding and interference cancellation instead of the separate approach. However, the trade-off is the complexity of a turbo decoder and the delay of a turbo decoder, a channel interleaver and a channel deinterleaver. Channel estimation algorithms cause estimation errors and result in imperfect performance of the receiver. Hence, the performance of the receiver against amplitude and phase errors of channel coefficients needs to be investigated. The simulation results show that the performance is more sensitive to phase errors than to amplitude errors. Moreover, The degradation due to combined amplitude and phase errors is greater than the summation of degradation due to each factor. This effect is more pronounced with large errors. This result is caused by increased degradation rate when the amplitude or phase errors increase. The results indicate that the allowable estimation errors of channel parameters to be used in the receiver for acceptable BER values. |
| Year | 2001 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. TC-01-12 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Telecommunications (TC) |
| Chairperson(s) | Rajatheva, R.M.A.P.; |
| Examination Committee(s) | Miikelainen, Kimmo ;Fernando, W. A. C.; |
| Scholarship Donor(s) | NOKIA Telecommunication Finland |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2001 |