5. The Eighth Category: Joint Precoding with Ideal Backhaul

For the eighth category of multipoint cooperative communication technology, we discuss joint precoding schemes with ideal backhaul conditions for the downlink cellular network in this chapter. First, we introduce some of the well-known precoding schemes for joint transmission (JT), that is, the global precoding (GP), local precoding (LP), weighted local precoding (WLP), and single-frequency network precoding (SFNP) schemes. Second, we propose an enhanced SFNP scheme with smart antenna selection (AS) operated at the cooperating base stations (BSs), which is named AS-SFNP scheme. Third, for single-antenna UEs, both analytical lower bounds and simulation results are provided to show that both the proposed AS-SFNP scheme and the WLP scheme achieve performance close to that of the optimal GP scheme in terms of average signal-to-interference-plus-noise ratio (SINR). For multi-antenna UEs, simulation results demonstrate that the proposed AS-SFNP scheme can achieve a larger capacity than the LP, WLP, and SFNP schemes in high-SNR regime. Furthermore, from a system-level simulation of a practical cellular network, the AS-SFNP scheme with a low feedback overhead and low-complexity implementation shows comparable performance of the cell-edge spectral efficiency with the WLP and GP schemes.