A dynamic subframe set power control scheme for interference mitigation in reconfigurable TD-LTE systems

In 3GPP LTE, TDD spectrum allocation for uplink (UL) and downlink (DL) use is a function of a cell's TDD UL/DL configuration which designates which time resources (i.e., subframes) are for UL and which are for DL. TDD dynamic UL/DL reconfiguration, under discussion in LTE Release 12, enables cells to quickly adapt the ratio of allocated UL and DL subframes to changing traffic patterns which can be different for neighboring cells. Having different UL/DL directions for the same subframe in adjacent cells can result in new destructive interference components, i.e., eNB-to-eNB and UE-to-UE, with levels that can significantly differ from one subframe to another. In this paper, UL power control mechanisms are considered to manage such interference, where different sets of UL subframes use different UL power control parameters. In particular, two schemes are studied where, in one, fixed subframe sets are chosen based on expected interference and, in the other, the eNB monitors interference levels in the subframes and dynamically reconfigures the subframe sets accordingly. The performance of each scheme is evaluated through system level simulations and it is shown that the UL power control with dynamic UL subframe set configuration outperforms the one with static UL subframe sets, with significant improvement achieved at cell edge.