LTE Advanced: 3GPP Solution for IMT-Advanced

13.4 Downlink CoMP Transmission

We now want to discuss the variants of downlink CoMP transmission, which differ substantially in the way multiple cells are involved in the transmission to single or multiple terminals. The different methods can be combined depending on how cells are clustered into CoMP sets. CoMP set refers to those cells from where a UE can receive or send data. A CoMP set can be considered similar to the active set in WCDMA. The two fundamentally different variants are illustrated in Figure 13.5. The centralized controller means an entity responsible for the transmissions across different cells and may be implemented both as a master-slave relationship between distributed but fast X2-interconnected baseband modules and as a centralized baseband architecture.

Figure 13.5 Joint processing and coordinated scheduling and beamforming.

In Coordinated Scheduling and Beamforming (CS/CB), terminals receive a data transmission from their respective serving cell only, but adjacent cells perform coordinated scheduling and precoding such that inter-cell interference is avoided or mitigated to some extent. This can be considered as an extension of Release 8 inter-cell interference coordination (ICIC). In this way, the SINR is improved for the stated terminals and the scheduling freedom is reduced for the neighbour cells, how much depends on which antenna features exist in the ...