In this chapter and Chapter 8, we do not consider the burstiness of arrival streams and investigate resource allocation and scheduling for best-effort traffic. Therefore, rate-based utility functions are used to perform cross-layer optimization and balance efficiency and fairness in this chapter. In Section 7.1, we discuss the general properties of rate-based utility functions. In Section 7.2, we investigate the optimization problems at an instantaneous time, which are formulated based on utility functions with respect to instantaneous data rates. In Section 7.2, we focus on the orthogonal frequency division multiplexing (OFDM) network that contains an infinite number of subcarriers and employs continuous rate adaptation. In the first four sections of Chapter 8, we develop efficient resource allocation algorithms for cross-layer optimization in various system configurations. In Section 8.5, we discuss channel-aware scheduling based on utility functions with respect to average data rates. The algorithms developed can be directly used for the channel-aware scheduling. In Section 8.6, we discuss efficiency and fairness issues. The relationship between a utility function and a certain type of fairness is revealed. In Section 8.7, we demonstrate performance improvement in cross-layer optimization through numerical results.

Rate-based utility functions

Utility functions are used for cross-layer optimization and balancing efficiency and fairness. A utility function maps the network resources that a user utilizes into a real number. In almost all wireless applications, a reliable data transmission rate is the most important factor to determine the satisfaction of users.