| Author | Kafle, Padam Lal |
| Call Number | AIT Thesis no.TC-98-11 |
| Subject(s) | Wireless communication systems
|
| Note | A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering, School of Advanced Technologies |
| Publisher | Asian Institute of Technology |
| Abstract | Proposed third generation of mobile radio systems such as UMTS have to support
very high bit rates up to 2 Mbit/s with BER as low as 10-6 for real-time data applications.
Recently, wideband DS-CDMA based radio interface has been shown to fulfill the
requirements of third generation systems. One of the problems for high rate data transmission
in a wideband wireless system is correlated multipath fading characteristics of the mobile
radio channel. Powerful error correcting codes and diversity schemes are required to mitigate
the degradation in performance. A new coding technique of turbo code, shown to have very
good performance in A WGN channels, is one of possible channel coding options also for
next-generation wireless systems.
In this thesis, performance of turbo code is studied over a correlated Rayleigh
multipath fading channel through simulation. Application to high-bit-rate data transmission is
considered in a wideband DS-CDMA based system for UMTS requirement. The effect on bit
error performance with correlated multipath fading is investigated by considering typical
high and low mobile speeds and varying the size of external interleaver. Performance on
fully interleaved fading channel is also evaluated for comparison. Comparison is also made
with equal decoding complexity convolutional code.
Based on the simulation results, performance of turbo code degrades significantly for
increased correlation in fading for low mobile speed when a short external interleaver is
used. Role of external interleaving is found to be critical and a relatively large-size external
interleaver is required to compensate the performance loss for low mobile speed.
Nevertheless, turbo codes still perform better than conventional convolutional codes, even in
correlated channels. A simple turbo code with moderate block size, and relatively short
interleaving delay can be used to achieve good BER performance at normal range of mobile
speeds. Hence, turbo code is found attractive to be used in third generation WCDMA based
systems, especially for high bit rate applications that can tolerate some interleaving delay. |
| Year | 1998 |
| Type | Thesis |
| School | School of Advanced Technologies |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Telecommunications (TC) |
| Chairperson(s) | Makelainen, Kimmo;Rajatheva, R.M.A.P.
; |
| Examination Committee(s) | Ahmed, Kazi Mohiuddin;; |
| Scholarship Donor(s) | DAAD; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1988 |