Point-to-point links and networks

The simplest wireless communication link is between a single transmitter and a single receiver. In point-to-point systems, data communication rates depend on factors such as bandwidth, signal power, noise power, acceptable bit-error rate, and spatial degrees of freedom.

Many wireless systems, however, comprise multiple interacting links. The parameters and trade-offs associated with point-to-point links hold for networks as well. Additional factors play a role in networks, however. For instance, interference between links can reduce data communication rates. An exciting possibility is for nodes to cooperate and help convey data for each other, which has the potential to increase data communication rates. Table 13.1 summarizes some of the key common and differentiating features of point-to-point links versus networks.

In this chapter, we analyze the performance of various multiantenna approaches in the context of cellular networks whereby signal and interference strengths are influenced by the spatial distribution of nodes and base stations. Note that we use the term cellular in a broader context than many works in the literature, which refer specifically to mobile telephone systems. Here we consider any kind of network with one-to-many (downlink) and many-to-one topologies (uplink). For most of this chapter except for Section 13.5.1, we shall focus on characterizing systems without out-of-cell interference, whereby we assume that there is some channel allocation mechanism with a reuse factor that results in negligible out-of-cell interference.