Cooperative communications is a new wireless networking paradigm that allows networking nodes to collaborate through distributed transmission and signal processing to implement spatial and time signal diversity to combat the effects of fading channels. These systems exploit the wireless broadcast advantage, where transmissions from an omnidirectional antenna can be received by networking nodes that lie within its communication range.

Internet became one of life’s basics in these days. More networks are connected to the Internet every day, which increases the amount of valuable data and the number of resources that can be attacked. Some systems have been designed and developed to secure these data and prevent attacks on resources. Unfortunately, new attacks are being created everyday, which make it hard to design a system that will catch these attacks. The need is not only for preventing the attack but also for detecting such attacks if it happened.

This paper is concerned with the power allocation problem in a transmit diversity wireless system with mean channel gain information. For a given set of mean channel gains between nodes, the aim is to find the power allocation and corresponding network topology that minimizes the total transmit power for nodes involved in the cooperative communications between the source and the destination, where all of the transmitters use single omnidirectional antennas.

This paper presents our initial investigations of noise enhancement control when decoding uplink transmissions in multi-cell multiuser multiple- input multiple-output (MU-MIMO) systems with zero- forcing (ZF) post-processing. This problem has been partially addressed within simplified cellular system topologies and with single antenna terminals. However, applying existing solutions directly to a multi cell system is not viable due to the noise enhancement that would heavily affect the inter-cell interference (ICI).

This dissertation investigates cross-layer designs in spatial division multiplexing (SDM) for multiuser multiple-input multiple-output (MU-MIMO) transmissions on the uplink. The MU systems which allow simultaneous transmissions on the downlink offer various improvements, such as an increase in total system throughput, and have already been standardized in IEEE 802.11ac wireless local area networks (WLANs) and cellular networks. However, the implementation of MU-MIMO SDM on the uplink is still considered to be an open problem.