Interference Management and Exploitation in Emerging Wireless Networks

Abstract

In the past decade, with the prevalence of smart phones, the main use of cellphones has been shifted from phone call to multimedia access. This paradigm shift has resulted in the demand for higher and higher transmission rate. Many sophisticated physical layer techniques, such as IDMA (interleave division multiple access), OFDM (orthogonal division multiple access), MIMO (multiple input multiple output), IA (interference alignment) and massive MIMO) have been proposed to cater for this demand. Meanwhile, cognitive radio networks and femtocell networks are proposed to strengthen the cellular networks.

Given these new exciting techniques, how to incorporate them into current wireless networks is one of the main issues need to be addressed. Moreover, taking a close look at these techniques, how to manage interference so that the throughput can be enhanced is one of the most important problems.

The first part of this dissertation investigates how to incorporate IDMA into two-tier femtocell networks so that the throughput of femtocell networks can be enhanced. Based on the computational capability of the femtocells, three schemes are proposed for the femtocell networks.

The second part of this dissertation addresses the problem of incorporating interference alignment to OFDM and MIMO-OFDM system. We firstly prove the upper bound of the throughput with an integer programming formulation. Then considering practical constraints of the (MIMO) OFDM system, effective algorithms are proposed to approach the theoretical bounds.

In the third part of this dissertation, how will the primary user and secondary users equipped with multiple antennas behave in cognitive radio networks is studied. With a Stackelberg game formulation, we derive the unique Stackelberg game equilibrium for the primary user and secondary users. The proposed scheme is also shown to outperform the non-spectrum-leasing scheme and a cooperative scheme in the literature.

In the fourth part the this dissertation, the problem of incorporating massive MIMO to FDD system is addressed. To reduce the cost of acquiring channel state information, two-stage precoding was proposed. The problems of user grouping and user scheduling thus arise. Three user grouping schemes and a greedy user scheduling scheme are proposed and validated. The problem of load balancing when the number of user is small is studied as well. Effective algorithm is proposed to solve this load balancing problem.

In summary, this dissertation aims to enhance the throughput of current or future wireless systems by managing interferences among different data streams or different users or different base stations. In-depth analysis and comprehensive results are also provided. Some of the findings may shed light on how to put emerging techniques into real applications.