Power control, Neighbor Discovery, and Backup Scheme for Emerging Wireless Networks

Abstract

With the booming wireless applications and services there has been a drastic increase in mobile data in recent years, as observed in several industrial white papers (e.g., Cisco Visual Network Index Report and Qualcomm’s 1000 Mobile Data Challenge). The trend is expected to continue during the next decade. The predicted 1000 times mobile data increase poses unprecedented challenges to existing and future wireless networks, and triggers huge interests in the future development of wireless communication and networking technologies.

To enhance the ability of next generation’s wireless communication networks, two directions are considered: to increase the efficiency of the allocated spectrum, or move to new, higher frequencies for greatly increased bandwidth. This dissertation aims to improve the efficiency of existing and future wireless communication networks through power control for full-duplex (FD) transmissions, and support the directional wireless transmissions in millimeter wave (mmWave) wireless networks. Furthermore, a backup base station based directional indoor network is studied for reducing the link outage probability of the vulnerable directional mmWave links.

The first part of this work investigates the problem of distributed power control for a wireless network where the nodes are capable of FD transmissions. The distributed algorithms for near optimal power control in FD wireless networks is developed. For the case of a single pair of FD nodes, a simple algorithm that computes the optimal power allocation is presented. For the case of multiple pairs of FD nodes, a distributed algorithm by applying a high SINR approximation is firstly developed, and a distributed algorithm based on an iterative approximation method for the logarithm function is proposed. For general FD networks, the performance for the basic 3-node FD mode is examined, and it shows that a general FD network can be decomposed into isolated nodes, paths, cycles, based on which the power control problem is solved with a proposed distributed algorithm.

The second part of this dissertation is focused on directional neighbor discovery in mmWave wireless networks. Although the employment of directional antennas brings many benefits, it also causes great challenges to neighbor discovery due to the deafness problem. we first consider the basic case of a transmitter-receiver pair, derive the condition for the transmitter and receiver beams to meet in space, and derive the distribution of the overlap angle of the two beams and the condition for a successful beacon-ACK handshake. The analysis also sheds useful insights on how to set the protocol parameters to ensure successful neighbor discovery. We then examine the case of a distributed network with autonomous nodes, adopt a special sequence design presented in prior work, to coordinate the transmission/reception mode of every node without centralized control. We show that combined with the basic case design of a transmitter-receiver pair, the proposed scheme can ensure neighbor discovery with bounded discovery time. We derive the procedure for ensured discovery, as well as a bound for the worst case discovery time.

The third part of this research digs deeper into directional neighbor discovery, which provides a fully bounded time directional neighbor discovery algorithm with multi-channel, multi-sector, and real two-way handshake beacon is proposed. Furthermore, a rigorous analysis is made for the conditions for a successful two-way handshake and multi-channel discovery in bounded time directional neighbor discovery. The proposed algorithm is fully distributed without requiring any previous information, which satisfies the practical condition for blind neighbor discovery. The algorithm and theorem provide useful fundamental conditions for sector based multi-channel directional neighbor discovery.

The last part of this study examine the performance of an mmWave network in indoor environments with and without a backup system. We first apply the Brownian motion model to develop an analysis of link outrage performance, and then develop an effective backup system to reduce the waste of air time due to broken links. With a rigorous analysis based on queuing theory and a Brownian motion based mobility model, we derive the average waiting time for the two systems with the general antenna model, and then analyze the performance under two ideal antenna models. The proposed design aims to reduce the waste of air time caused by broken mmWave links. We found each systems, i.e., with or without backup, have their advantages in certain operation scenarios.