| 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 |
