Department Publications

In this paper, we focus on the ergodic downlink sum-rate performance of a system consisting of a set of heterogeneous users. We study three user selection schemes to group near-orthogonal users for simultaneous transmission. The first scheme is a random selection policy that achieves fairness, but does not exploit multi-user diversity. The second scheme is a greedy selection policy that fully exploits multi-user diversity, but does not achieve fairness, and the third scheme achieves fairness while partially exploiting multi-user diversity. We also consider two beamforming methods for data transmission, namely, maximum-ratio transmission and zero-forcing beamforming. In all scheduling schemes studied in the paper, there is a key parameter that controls the degrees of orthogonality of channel directions between co-scheduled users. We focus on optimally setting this parameter for each scheduling scheme such that …

The outage probability of a two-hop coordinated decode-and-forward relay network is investigated. The case of two interfering cells is considered. This is analogous to the case when network coordination is performed with the dominant cochannel interfering cell. Different levels of network coordination are studied and their performances are compared. Exact expressions are derived for of the system for each coordination method. The impact of user location randomness on the outage probability is investigated.

The outage probability of a two-hop coordinated decode-and-forward relay network is investigated. Relay coordination is performed only with the dominant interferer. Different levels of network coordination are studied and their performances are compared. Exact expressions are derived for the outage probability of a particular mobile user for each coordination scheme. Asymptotic outage probability is derived to identify the diversity and coding gains for each coordination scheme.

An ergodic rate analysis is presented for relay coordination schemes of two-hop decode-and forward relay networks. A simplified two-cell network model is used in the analysis. This model is related to a practically significant case, where the relay coordination is implemented with the cell which causes the most dominant cochannel interference level. Closed-form expressions are derived for the ergodic rate of the system. Simplified approximations are derived to approximate the ergodic rate behaviour in the asymptotically high signal-to-noise ratio regime.

The demand for high data rate wireless services has grown tremendously. The demand is expected to grow further at an increased pace. The scarcity of the usable radio frequency spectrum is a major bottleneck to cater to the growing demand for high data rate wireless services. Current cellular wireless networks rely on deploying small cells as a possible solution to cater to the growing demand. However, this practice has resulted in severe co-channel interference (CCI) levels in cellular networks. The first phase of this thesis investigates the impact of CCI on relay networks and distributed antenna systems, which are included in recent wireless standards such as long-term evolution advanced (LTE-A). The analytical results derived for system performance metrics, such as the outage probability and the ergodic rate, are used to obtain valuable insights for system design. The second stage of this thesis research …