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Soft-output maximum likelihood sequence estimation with multiple channel estimators for fast time-varying mobile radio channels | |
Author | Pitukpong Kinawong |
Call Number | AIT Thesis no. TC-96-1 |
Subject(s) | Cellular radio |
Note | A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering, School of Engineering and Technology |
Publisher | Asian Institute of Technology |
Abstract | In the conventional Maximum Likelihood Sequence Estimator (MLSE), the delayed decision is used as an input to a channel estimator for channel tracking. The delayed decision can cause the degradation of tracking capability of a channel estimator if the channel change rapidly. The MLSE using multiple channel estimators has been reported to be effective in the fast time-varying mobile radio channel. In this case, each channel estimator updates its own channel estimate by using the zero-delay tentative decision derived from its corresponding survivor path in the Viterbi Algorithm (VA). The convolutional coding is exploited in IS-54 standard for F01ward Error Correction (FEC) and generally the Viterbi decoder is used at the receiver for convolutional decoding. If the MLSE is employed in the receiver of the IS-54 system, the system can be modeled as the cascade of two V As. The MLSE represents the inner VA and the Viterbi decoder represents the outer VA. And it is well known that the overall performance of the system could be significantly improved if the inner VA is able to deliver the soft outputs to be used by the outer VA. In this thesis, the soft-output MLSE with multiple channel estimators is developed. Its performance will be evaluated in term of Bit Error Rate (BER) as a function of Et/No and compare to those of the MLSE with single channel estimator by computer simulation. The IS54 parameters are used in the simulation model. From the simulation, the soft-output MLSE with multiple channel estimator results in a significant BER performance improvement over the soft-output MLSE with single channel estimator in the fast time-varying mobile radio channel. Its performance in the slowly and moderately time-varying channel are also satisfactory. However, the improvement m performance must be traded with the expense of higher computational complexity. |
Year | 1996 |
Type | Thesis |
School | School of Advanced Technologies (SAT) |
Department | Department of Information and Communications Technologies (DICT) |
Academic Program/FoS | Telecommunications (TC) |
Chairperson(s) | Makelainen, Kimmo |
Examination Committee(s) | Ahmed, Kazi Mohiuddin;Zhang, Jian-Guo |
Scholarship Donor(s) | Asian Institute of Technology Partial Scholarship |
Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1996 |