Uplink coordinated multi-point reception in LTE heterogeneous networks

In a 3GPP Long-Term Evolution (LTE) network where base stations with widely different transmit powers coexist, such as macro and pico nodes, traditional cell selection based on Downlink (DL) received signal strength gives rise to suboptimal Uplink (UL) cell selection. Thus, the pico node may receive the UL signal of close-by macro users better than their respective serving macro Base Station (BS). The good channel to other nodes than the serving macro BS may be exploited through UL Coordinated Multi-Point (CoMP) schemes. UL CoMP may therefore yield higher gains in a heterogeneous network setting than in a macro network where the base station transmit powers are similar. In this paper two UL CoMP schemes are evaluated through dynamic radio network simulations: selection combining in which the cooperating BSs try to decode the signal separately and share the outcome, and multi-cell Interference Rejection Combining (IRC) which is a joint reception scheme. Especially the users that are connected to the macro BS but have a lower pathloss to a pico node exhibit large gains from both schemes. The designed user transmit power adjustment algorithm enables further improvement of the pico users´ performance.