Space-Time Block Codes for Wireless Systems - The ...

In our RMTCM design, a regular trellis constructed specifically for fading channels
is generated by shift-register chains. NHCs, which admit a natural set partitioning as in
[Ung82], form the constituent codes. The parameters of the regular trellis and set partitioning
are matched to exploit the layered structure of the constituent NHCs optimally.
Several factors which affect performance in both quasi-static and fast block fading channels
are analyzed and exploited to improve the overall performance. Set expansion is used
to improve high rate MTCM designs. In each design, the performance/rate/complexity
tradeoffs are gracefully balanced and optimized. The general design procedure can be
used to serve two purposes: for a given set of NHCs, provide MTCM designs with various
rates, and, for a given rate, provide MTCM designs with various complexity and
performance.
The MTCM design in [JS02] is a special case of the RMTCM design in this work,
where the constituent codes are restricted to orthogonal codes and signal expansion is
limited to a special isometry; the set partitioning and trellis structure of [JS02] are not
systematic. RMTCM design can achieve a half dB gain over the rate 3 MTCM design in
[JS02] by doubling the number of states via adjusting trellis parameters. With even more
states, as much as 2dB gain can be achieved. The observation, that parallel transitions
should be avoided for better performance in quasi-static channels, is made in [JS02] for
orthogonal constituent codes only, we will show that it holds for more general cases.
The design principles of RMTCM do not rely on quasi-static fading channels. Thus
they can be employed to design RMTCM even for fast block fading channels, where fast
block fading is achieved due to perfect block interleaving. Both analysis and simulation
show that parallel transitions are the major detrimental factor which should be avoided
for fast block fading channels. A similar conclusion is drawn for MTCM design over
Single-Input-Single-Output fast-fading (due to perfect interleaving) channels [BDMS91].
This thesis is organized as follows: Chapter 2 discusses space-time block codes in
multipath CDMA systems. Chapter 3 discusses suboptimal linear decoders. Chapter 4
discusses the construction and properties of NHC. Chapter 5 discusses the design procedure
and performance analysis of RMTCM. Chapter 6 summarizes this work and points
out future work.
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