On the performance of CoMP transmission in unsynchronized networks with timing offset

Coordinated Multipoint (CoMP) transmission is a promising technology in 4G Long Term Evolution (LTE) systems to enable coverage and high data rates for cell edge User Equipments (UEs). However, the presence of Timing Offset (TO) between the received signals from multiple transmitters at the UE could prove prohibitive for CoMP transmission. Such TO affects the estimation of the transmit covariance matrix for Pre-coding Matrix Index (PMI) selection significantly. Especially, the promised advantages of closed-loop CoMP transmission vanishes and it performs even worse than the open-loop in presence of a large TO due to the improper PMI selection. With analytical and numerical results we show that keeping the TO small, the promised advantages of closed-loop CoMP transmission can be guaranteed and as a result near optimum performance is achieved for CoMP transmission in unsynchronized networks with TO present.