Modified lee algorithm with soft decision feedback and backward recursion using m-algorithm | |
| Author | Piyapun Kaokitvirach |
| Call Number | AIT Thesis no.TC-00-10 |
| Subject(s) | Algorithms Wireless communication systems |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering. School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. TC-00-10 |
| Abstract | Wireless communication systems require signal processing techniques that improve the link performance in hostile radio environments. As we know, equalization is one of techniques that is used to improve received signal quality. If the modulation bandwidth exceeds the coherence bandwidth of the radio channel, inter-symbol interference (ISI) occurs and modulation pulses are spread in time. Equalization compensates for ISI created by multipath within time dispersive channels. Maximum a posteriori probability (MAP) equalization technique is well known as a powerful ISI reduction technique, which provides optimum performance at the cost of very high complexity. The complexity grows exponentially with the number of symbols affected by the ISL Therefore, it is important to develop suboptimal algorithms that require less computing resources without significant degradation in performance. In this thesis, a new reduced-state MAP equalization algorithm, called M-Lee algorithm, is presented with a tradeoff between complexity reduction and performance degradation. Its performance will be evaluated in terms of bit error rate (BER) as a function of Eb/No with a comparison to Max-Log-MAP and modified Lee algorithm by the computer simulation. Max-Log-MAP is a suboptimum version ofBahl's MAP algorithm, which has a large computation complexity. From the simulation results, the M-Lee algorithm gives a reduction in complexity with the same performance as the modified Lee algorithm. In addition a better performance is obtained than the modified Lee algorithm at less complexity but with more memory requirement. When compared with Max-log-MAP algorithm, M-Lee algorithm gives a large reduction in complexity at a performance degradation of 2-4 dB with suitable parameters and modulation schemes. However, the high level modulation schemes does not work well with M-Lee algorithm. |
| Year | 2000 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. TC-00-10 |
| 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) | Ahmed, Kazi M.;Tapio Erke; |
| Scholarship Donor(s) | Asian Institute of Technology (Partial Scholarship) |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2000 |