In this chapter, we discuss energy-efficient designs for wireless cellular networks, which is a major concern for operators to reduce operational expenditure and to reduce environmental impact. In cellular networks, base stations dominate energy consumption and drain approximately 60–80% of overall network energy consumption. We will discuss the energy-efficient design of cellular base stations (BSs). There are several current technologies for environmentally friendly and energy-efficient cellular networks. A few examples are:

1. (i) Link level: energy-efficient transmission, dynamic mode switching, low-power circuit design, etc.

2. (ii) Multi-user level: energy-efficient scheduling and resource management.

3. (iii) Network level: energy-efficient topological approaches from deployment to operation and energy-efficient mobility management.

In previous chapters, we have discussed both link and multi-user level energy-efficient designs. In this chapter, the focus is on network-level solutions. We will first introduce some fundamental tradeoffs in using wireless resources. Then we investigate energy-efficient network deployment and operation technologies.

Fundamental tradeoffs in network resource utilization

Both spectrum and energy efficiency emphasize communication quality in the sense that successful data transmission will help improve both metrics. From this perspective, energy efficiency also requires spectral efficiency improvement and vice versa. On the other hand, energy and spectrum are two independent fundamental resources and both are needed to meet quality of service (QoS) requirements. Tradeoff is always there and depends on network choice. Any network design can always choose to optimize the utilization of one resource over the other.