M.Sc. Thesis
Thesis Title: Abstract: PS: You can find the presentation in PPT format at Here
Cooperative Communications Using Space-Time Codes
Diversity is a powerful technique to mitigate channel fading in a wireless network. One of
the widely used diversity techniques is spatial diversity. Space-time wireless systems
traditionally use multiple colocated antennas at the transmitter and receiver along with
appropriate signal design (also known as space-time coding) to realize spatial diversity in
the link. Typically this diversity can augment any frequency and time diversity available to
the receiver. A recent development in this area aims at dispensing with the need for
colocated antennas. Popularly known as the cooperative diversity technique, this uses the
antennas at multiple user terminals in a network in the form of a virtual antenna array to
realize spatial diversity in a distributed fashion. Such techniques create new challenges in
the design of wireless systems. There are several methods to achieve cooperative diversity,
including repetition-based and space-time coded cooperative systems. In this thesis, after
reviewing on different cooperative diversity methods, we develop space-time coded
cooperative systems which utilize distributed space-time codes among the cooperative
users. First, GABBA space-time codes in a distributed manner are introduced, which can be
generalized to any number of relays with linear orthogonal decoding in the destination.
Moreover, performance of these codes is investigated through analytical methods and
simulations. Then, we present distributed differential space-time codes with Alamouti’s
structure employing a single relay. Two decoding techniques and optimum power control
for this system are also considered. Finally, we develop several cooperative protocols based
on distributed space-time codes. These protocols include static cooperation (also known as
fixed relaying), incremental relaying which uses a limited feedback, and dynamic
cooperation in which relay selection strategies are exploited.