Coding, Decoding and Multiuser Detection for Wireless CommunicationsCoding, Decoding and Multiuser Detection for Wireless Communications
Licentiate thesis, 1997
In the strive for making the Universal Mobile Telecommunication System
(UMTS) a reality, concepts and techniques are to be developed which can
provide both high system capacity and sufficient quality for the increasing
number of mobile users. To obtain these objectives, powerful and flexible
error control coding is needed, as well as efficient means for many users
to share the same commmication medium. This thesis contributes by presenting
new optimum convolutional channel codes, outperforming those previously
reported. These new and improved codes are then used as a basis for deriving
flexible and powerful families of codes with many code rates. The various
wireless services require different levels of error protection as well
as a means for matching different data rates to the rate of the channel.
Rate matching in multirate direct-sequence code-division multiple-access
(DS-CDMA) systems is described and the performance is evaluated in terms
of efficiency. Furthermore an error control scheme capable of providing
extremely low error rates is proposed and shown to be a good candidate
for some services in wireless mobile systems. A wireless system using DS-CDMA
as its multiple access technique is normally severely interference limited.
Joint detection of many users as well as interference cancellation techniques
have in recent years been proposed to reduce the impact of the interference.
The performance of a number of detectors is compared and shown to be very
sensitive to errors in the time and phase estimates.
direct-sequence code division multiple access (DS-CDMA)
optimum distance spectrum
rate compatible punctured convolutional codes