This chapter mainly presents state-of-the-art green communication solutions and analytical models for both network operators and mobile users at different traffic load conditions. In particular, in green wireless networks, two categories can be distinguished for the proposed solutions and models to enhance and analyse the energy efficiency based on the call traffic load condition. At a low and/or bursty call traffic load, resource on–off switching techniques are adopted, while scheduling techniques are employed at a high and/or continuous call traffic load. In the following sections, green solutions at different traffic load conditions are first reviewed, and then a description of the existing green projects and standards is presented. Future research directions are also presented to address the limitations of the existing approaches.
On–off switching of radio resources is adopted at low and/or bursty call traffic load conditions to enhance energy efficiency as shown in Table 2.1. Network operators employ on–off switching mechanisms for their BSs at a low call traffic load. Similarly, MTs switch on–off their radio interfaces in a bursty traffic condition. The following sub-sections focus on the related research issues and modelling techniques pertaining to the adoption of these solutions.