Abstract

Nowadays, the concept of spatial diversity and cooperative networks attract a lot
of interest because they improve the reliability of transmission in wireless networks.
Spatial diversity is achieved when multiple antennas are at the transmitter. With great
growth and demand for high speed high data rate wireless communication, more and
more antennas are required. In order to achieve maximum diversity, these antennas
should be well separated so that the fading on each link is uncorrelated. This condition
makes it difficult to have more than two antennas on a mobile terminal. The relay's
cooperation helps increase the diversity order without extra hardware cost. However, its
main inconvenience is the use of multiple time slots compared to the direct link
transmission.
In this thesis, we develop a cooperation model which is composed of three
terminals: source, relay and destination. The transmitters (source and relay) are composed
of 2 antennas at the transmitter and the receivers (relay and destination) have 4 antennas.
In the first proposed model, transmitters and decoders are composed of an Alamouti
encoder and decoder respectively. In the second model, we also add a turbo encoder at
transmitters and iterative decoding takes place at receivers. In both cases, the
transmission cycle is composed of two time slots and the decode and forward (DF)
protocol is applied. Multiple scenarios are considered by changing the environment of the
transmission, such as line of sight (LOS) or non line of sight (NLOS) or by modifying the
location of the relay between the source and destination. We also simulate an uplink and
a downlink communication. All the scenarios show a coding gain with the turbo coded
space-time cooperation.