Abstract:
Cooperative data transmission is one of the most significant techniques to mitigate
fading induced errors in wireless networks. The key idea in cooperative data
transmission is that of resource sharing among multiple nodes in a network. This idea
enables to design technologies using efficient spectrum utilizations. Although
multiple input multiple output system provides a single node to be equipped with
multiple antennas, relative higher cost in implementing this system is a barrier.
Spatial diversity for wireless transmission requires more than one antenna at the
transmitter. However, mobile devices are usually limited by size, so installation of
multiple antennas increases the hardware complexity significantly. Due to the
omnidirectional nature of wireless signal, a data transmission between a source node
and a destination node can be overheard by many other neighbor nodes. By
exploiting this characteristic, a number of recent research activities on cooperative
Medium Access Control (MAC) have been devised where low data rate stations are
assisted by the high data rate stations in forwarding data traffics. Therefore, wireless
devices with a single antenna can effectively form a virtual array of antennas by
sharing each other’s antennas in a multiuser environment. In this thesis a
mathematical model is derived for the performance analysis of the legacy IEEE
802.11 DCF MAC using markov chain. This thesis proposes a new distributed
cooperative MAC protocol and evaluates the proposed protocol’s performances using
mathematical modeling. In the proposed protocol a potential relay node initiates
itself to participate in the cooperation by calculating supported data transmission rate
between source to relay and relay to destination links. Mathematical analysis of the
proposed protocol in error prone channel and flat fading Rayleigh environment is
presented in this thesis. Performance of the proposed scheme is compared with that
of the existing IEEE 802.11 DCF MAC. Numerical results show that the proposed
scheme can increase throughput and decrease average frame delay of any IEEE
802.11 Wireless LAN’s low data rate station comprehensively.
