Stability and Performance of Emerging Wireless Networks

Abstract

In this work, we analysis the application of emerging wireless communications on the stability of computing and transmission queues of mobile devices. Firstly, we present a Lyapunov optimization-based scheme for cloud offloading scheduling, as well as download scheduling for cloud execution output, for multiple applications running in a mobile device with a multi-core CPU. We derive an online algorithm and prove performance bounds for the proposed algorithm with respect to average power consumption and average queue length. which is indicative of delay, and reveal the fundamental trade-off between the two optimization goals.

Extending Long Term Evolution (LTE) to unlicensed bands, termed LTE-unlicensed promises tremendous spectrum to meet the increasing wireless data transmission demands and we proposed a novel distributed online algorithm for opportunistic sharing of unlicensed bands among LTE-unlicensed base stations (BS), while guaranteeing the QoS of user equipments (UE). We first derive a Lyapunov optimization based algorithm for BS's to evaluate the true value of unlicensed spectrum, guarantee a maximum delay, and minimize the packet drop rate. We then develop a distributed auction mechanism to maximize the social welfare in each auction and enable optimal spectrum reuse. We prove that BS's bid truthfully with the proposed algorithm, while UEs' QoS requirements on delay and packet drop rate can be guaranteed with bounded optimality gaps. We also reveal an interesting trade-off between delay and packet drop rate.

Full-duplex is gaining significant interest recently and can double the system throughput theoretically. In this work, we investigate the trade-off between energy consumption and delay in a multi-channel full-duplex wireless LAN (WLAN). The goal is to minimize the energy consumption while keeping the packet queues stable. With Lyapunov optimization, we develop an online scheme to achieve the goals with optimized channel assignment, transmission scheduling, and transmission mode selection. We prove the optimality of the proposed algorithm and derive upper bounds for the average queue length and energy consumption, which demonstrate the energy-delay trade-off.

We finally studied the problem of joint access control and spectrum resource allocation in a two-tier femtocell network with one macro base station (MBS) and multiple Femto Access Points (FAP). The objective is to maximize the overall network capacity, while guaranteeing the quality of service (QoS) requirement of all UE. We develop an access scheme for Macro User Equipments (MUE) and a spectrum allocation mechanism for the FAPs. Spectrum allocation is employed as an incentive mechanism to encourage FAPs to serve more MUEs. We also derive an upper bound of the network-wide capacity through a reformulation of the problem.