A reduced complexity soft-output algorithm based on sequential decoding technique and its applications | |
| Author | Eakapong Tungsrisaguan |
| Call Number | AIT Diss no.TC-02-02 |
| Subject(s) | Algorithms Coding theory |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Advanced Technologies |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation; no. TC-02-02 |
| Abstract | The performance of concatenated decoding systems can be improved if the inner decoder is capable of delivering the reliability information together with hard decisions to the outer decoder. The decoding algorithms with such a capability are referred to as softoutput decoding algorithms. The most commonly used algorithms of this class include the Maximum A Posteriori probability (MAP) algorithm, the Soft-Output Viterbi algorithm (SOVA), as well as their variations. However, in spite of their near-optimum performance, their computational complexity depends exponentially on the constraint length of the code trellis and makes them impractical for various types of applications. This has led to the examination of a number of reduced complexity decoding algorithms. In this dissertation, a novel reduced complexity soft-output decoding algorithm based on the sequential decoding technique called the Soft-Output Sequential Algorithm (SOSA) is developed. The advantage of SOSA comes from the inherent property of sequential algorithm, in which the decoding complexity is only linearly dependent on the code constraint length, as opposed to MAP and SOVA algorithms. It is possible to apply SOSA to various applications where long constraint length is unavoidable, such as the equalization and multiuser detection systems. Furthermore, SOSA can readily be applied in the iterative ("Turbo") processing configuration, which greatly improves the receiver performance over the conventional concatenated decoding techniques. The applications of SOSA on turbo equalization and iterative multiuser detection have been investigated. The results have shown that SOSA offers a significantly better performance and complexity trade-off compared to various soft-output algorithms, especially for systems with very high computational requirement. Apart from these, it can also be applied to various types of applications, e.g., the joint source and channel decoding, where it is possible to expect the same degree of performance/complexity trade-off advantage over the conventional approaches. In conclusion, SOSA is a promising solution to various applications in high-speed digital communication systems, where substantial reduction in computational complexity is required. |
| Year | 2002 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation; no. TC-02-02 |
| Type | Dissertation |
| School | School of Advanced Technologies |
| Department | Department of Information and Communications Technologies (DICT) |
| Academic Program/FoS | Telecommunications (TC) |
| Chairperson(s) | Rajatheva, R.M.A.P.;Kazi M. Ahmed; |
| Examination Committee(s) | Phien, H.N.;Teerapat Sanguankotchakorn;Shwedyk, Edward ; |
| Scholarship Donor(s) | Government of Austria; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2002 |