Enabling Downlink Coordinated Multi-Point Transmission in TDD Heterogeneous Network

Downlink coordinated multi-point (CoMP) is one of the key technologies in the 3rd generation partner project (3GPP) long term evolution (LTE) release 11 & 12. With the multi-point joint transmission or coordinated scheduling/beamforming, the inter-cell interference could be significantly decreased. So the cell edge users' performance could be greatly increased. However, it always requires to introduce non-ignorable signalling overhead, such as downlink control signal or uplink feedback, which will offset the CoMP gain over the single cell transmission. Then scenarios and algorithms that could enable downlink CoMP transmission with minimum standard impact seems more desirable. This paper studies the downlink CoMP transmission in a time duplex division (TDD) heterogeneous network (HetNet). With the reuse of the currently available reference signal and feedback scheme, the beamforming algorithm with the per-point and per-antenna power constraint has been proposed, together with a channel quality information (CQI) modification algorithm. Simulation results show that the proposed algorithms could provide significant CoMP gain over the single cell transmission scheme. In addition, the algorithms are compatible with available terminals, which could also benefit from CoMP operations.