Nilo Casimiro Ericsson

PhD Thesis, Uppsala University, ISBN 91-506-1773-7 Sept. 2004, 214 pp.

Dissertation in Signal Processing to be publicly examined in room K23, Magistern, Dag Hammarskjölds väg 31, Uppsala on October 22, 2004 at 10.15 a.m.

Faculty Opponent: Professor Jens Zander, KTH, Stockholm.

The thesis available in Postscript 30.0M ; In Pdf: 8.1M.

Paper copies of the thesis can be obtained from Ylva Johansson, Signals and Systems Group, Uppsala University, Box 534, SE-75121 Uppsala, Sweden.

Outline:

We consider the problem of distributing a limited amount of shared resources among a number of clients, in a fashion that optimizes a revenue-based criterion. More specifically, we consider the problem of service resource scheduling to a population of clients with different and time-varying service requirements and also different and time-varying resource utilization per service unit. Furthermore, the clients generate different revenue for the owner of the server. The question we try to answer is: How do we decide who should use the shared resource when?

This problem is found in wireless mobile communications, where different mobile hosts are travelling at different speeds and directions, and at different distances to a radio signal transmitting base station. The mobile hosts therefore experience different and varying signal qualities, affecting the capacity of the resource they utilize for transmission of information. Since different users may run different applications on the mobile hosts, they also have varying service demands.

Abstract:

Revenue maximization for network operators is considered as a criterion for resource allocation in wireless cellular networks.

A business model encompassing service level agreements between network operators and service providers is presented. Admission control, through price model aware admission policing and service level control, is critical for the provisioning of useful services over a general purpose wireless network.

A technical solution consisting of a fast resource scheduler taking into account service requirements and wireless channel properties, a service level controller that provides the scheduler with a reasonable load, and an admission policy to uphold the service level agreements and maximize revenue, is presented.

Two different types of service level controllers are presented and implemented. One is based on a scalar PID controller, that adjusts the admitted data rates for all active clients. The other one is obtained with linear programming methods, that optimally assign data rates to clients, given their channel qualities and price models.

Two new scheduling criteria, and algorithms based on them, are presented and evaluated in a simulated wireless environment. One is based on a quadratic criterion, and is implemented through approximative algorithms, encompassing a search based algorithm and two diffterent linearizations of the criterion. The second one is based on statistical measures of the service rates and channel states, and is implemented as an approximation of the joint probability of achieving the delay limits while utilizing the available resources effently.

Two scheduling algorithms, one based on each criterion, are tested in combination with each of the service level controllers, and evaluated in terms of throughput, delay, and computational complexity, using a target test system.

Results show that both schedulers can, when feasible, meet explicit throughput and delay requirements, while at the same time allowing the service level controller to maximize revenue by allocating the surplus resources to less demanding services.

Keywords:

Wireless resource, scheduling, admission control, service level control, service level agreement.

Table of Contents:

1. Introduction
2. Revenue -the Criterion
3. Admission Control
4. Scheduling
5. Scheduling Algorithms
6. Power-n Scheduling Criteria
7. Probability based Scheduling Criteria
8. Simulations
9. Case Study
10. Conclusions and Future Work.

Related publications:

LicenciateThesis by Nilo Casimiro Ericsson, June 2001.
Future Telecom Conf. Dec. 2001 on Scheduling and adaptive transmission for the downlink in 4G Systems.
VTC'00-Fall on Hybrid type-II ARQ/AMS supported by channel predictive scheduling in a multi-user scenario.
Globecom'99 on adaptive modulation and scheduling.