Multiuser detection on uplink asynchronous DS-CDMA relay channel in Rayleigh fading | |
| Author | Jayatunga, Eranda Harshanath |
| Call Number | AIT Thesis no.ICT-07-01 |
| Subject(s) | Spread spectrum communications Code division multiple access |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Information and Communications Technologies, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. ICT-07-01 |
| Abstract | Transmission over wireless channels suffers from fading and co-channel interference. Diversity is a powerful technique to mitigate fading and improve robustness to interference. On the other hand, cooperative diversity is an attractive transmission technique even when the transmit diversity cannot employ with mobile terminals due to their size constraints. Code division multiple access (CDMA) is more attractive with multiuser environments and provides high data rates. But it makes problems such as multiple-access interference (MAI) that degrades the system performance. As a result of it, sub-optimal multiuser detectors are applied at the receiver to mitigate the effect of interference. Therefore, our research is mainly focused on analyzing a cooperative direct-sequence CDMA (DS-CDMA) relay channel system consisting of one source terminal and two relay nodes with multiuser detection. The system is studied over the frequency-flat fading environment for uplink communications and decode-and-forwarding (DF) scheme is used at the relay nodes. The relevant system is analyzed and validated with appropriate simulation results for binary phase shift keying (BPSK) scheme in two stages. In the first instance, the bit error rate (BER) performance is analyzed by assuming the relay nodes correctly decode information and approximately 10-2 BER performance improvement can be obtained at Eb/No = 20dB in synchronous transmission of users. Although the asynchronous transmission reduces the BER performance due to crosscorrelation properties of users, still a significant BER performance can be achieved. The effect of changing the processing gain, (N) is also studied here and verified by simulation. It shows that the BER performance can be improved by increasing the processing gain in both synchronous and asynchronous transmissions. Next, the BER expressions are obtained and verified by assuming that the relay nodes forwards information only if they correctly decode information. Furthermore, perfect cyclic redundancy check (CRC) is applied at the relays and two Bernoulli random variables are used to describe the relevant decoding process there |
| Year | 2007 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. ICT-07-01 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Information and Communication Technology (ICT) |
| Chairperson(s) | Rajatheva, R. M.A. P; |
| Examination Committee(s) | Ahmed, Kazi M;Erke, Tapio; |
| Scholarship Donor(s) | The Government of Finland; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2007 |