This chapter deals with another major challenge connected to CoMP, namely the synchronization of cooperating and cooperatively served devices in time and frequency. On one hand, there are different local oscillators in each base station and mobile terminal that lead to deviations in the carrier frequency according to its nominal value. On the other hand, there are variations in the symbol timing between each transmitter and receiver station. Both effects need to be compensated by synchronization techniques.

In cellular networks, we can distinguish between a network synchronization among all involved base stations and the alignment of the user equipments to that time and frequency reference. The basic definitions of the synchronization terms as well as procedures for the reference network synchronization are described in Section 8.1. The impact of symbol timing mismatches on CoMP is then treated in Section 8.2, before Section 8.3 concludes this chapter with the analysis of the impact of residual carrier frequency offsets on CoMP performance.

Synchronization Concepts

Synchronization is the process of establishing a common notion of time among two or more entities. In the context of wired and wireless communication networks, synchronization enables coordination among the nodes in the network and can facilitate applications such as distributed sensing. Precise synchronization can also facilitate scheduling of communication resources as well as interference avoidance in multi-access networks.