The main goal of this chapter is to describe proven techniques employed to mitigate interference. We focus on dynamic and system level mechanisms that are able to adapt to the interference environment. Interference suppression techniques including coding, modulation, and filtering, in addition to others related to physical layer technologies such as CDMA and OFDM, abound in the open literature. The interested reader is referred to other texts such as ref. for an in-depth treatment of these technologies.

The system level coexistence techniques that we are concerned with can be classified into two broad categories. The first category of solutions consists of some form of sharing, making use of either temporal or spectral sharing, and, in some instances, a joint time and frequency domain technique. The second category of solutions is about adaptation and the opportunity to choose either the radio or the network that is best suited to the environment. This class of solutions includes handovers and the ability to roam across different networks.

Sharing the medium is synonymous with multiple access techniques. In Chapter 2, we briefly overviewed three types of multiple access techniques, namely TDMA, FDMA, and CDMA. Since the emphasis is on system level solutions, we consider TDMA and FDMA. Although CDMA is considered to be an effective interference suppression technique, it is specific to coding functionality at the physical layer and therefore it is not pertinent to a system level solution.