Scheduling and Resource Allocation in Multi-user Wireless Systems
Date
2014-10-15
Authors
Wang, Xuan
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
In this dissertation, we discuss various aspects of scheduling and resource allocation in multi-user wireless systems.
This work starts from how to utilize advanced physical-layer technology to improve the system performance in a multi-user environment.
We show that by using superposition coding (SPC) and successive interference cancellation, the system performance can be greatly improved with utility-based scheduling. Several observations are made as the design guideline for such system. Scheduling algorithms are designed for a system with hierarchical modulation which is a practical implementation of SPC.
However, when the utility-based scheduling is designed, it is based on the assumption that the system is saturated, {\em i.e.}, users in the system always have data to transmit. It is pointed out in the literature that in a system with stochastic traffic, even if the arrival rate lies inside the capacity region, the system in terms of queue might not be stable with the utility-based scheduling. Motivated by this, we have studied the stability region of a general utility-based scheduling in a multi-user system with stochastic traffic. We show that the stability region is generally less than the capacity region, depends on how to interpret an intermediate control variable, and the resultant stability region may be even non-convex and exhibits undesirable properties which should be avoided.
As the utility-based scheduling cannot achieve throughput-optimal, we turn our attentions to the throughput-optimal scheduling algorithms, whose stability region is identical to the capacity region. The limiting properties of an overloaded wireless system with throughput-optimal scheduling algorithms are studied. The results show that the queue length is unstable however the scheduling function of the queue length is stable, and the average throughput of the system converges.
Finally we study how to schedule users in a multi-user wireless system with information-theoretic security support, which is focused on the secrecy outage probability. The problem is essentially about how to schedule users, and allocate resources to stabilize the system and minimize the secrecy outage probability. We show that there is a tradeoff between the arrival rate of the traffic and the secrecy outage probability. The relative channel condition of the eavesdropper also plays an important role to the secrecy outage probability.
In summary, we showed utility-based scheduling using SPC can improve the system performance greatly, but the utility-based scheduling has limitations: the stability region might not have desired properties. On the contrary throughput-optimal scheduling has its own drawbacks: the traffic cannot be handled properly if the system is overloaded. The further study on the secrecy outage probability gives guideline on how to design a scheduler in a system with information-theoretic security support.
Description
Keywords
scheduling, wireless networks, wireless systems, resource allocation