LTE Uplink Interference-Aware Scheduling Using High Interference and Overload Indicators

Abstract

LTE uses single carrier-frequency division multiple access (SC-FDMA) scheme for the uplink transmission which limits the flexibility of the allocation process as the sub carriers assigned to a single user have to be contiguous. We propose an LTE uplink interference-aware search-tree based scheduling scheme using the high interference indicator (HII) and the overload indicator (OI) messages that are exchanged over the X2-interface. HII indicates the potential uplink inter-cell interference (ICI) to other cells while OI indicates the detection of low, medium or high uplink ICI from other cells. The exchanged HII and OI messages are used to scale down the proportional-fair (PF) scheduling metric before being processed by the search-tree scheduler to make interfered physical resource blocks (PRBs) less favorable to cell-edge (CE) UEs. Unlike previous work which handles these problems separately, the proposed integrated RRM framework jointly takes into account 1) interference information exchanged between neighbor eNBs, 2) constraints on max power per UE and equal power on different PRBs, and 3) constraints on the contiguity in PRBs allocation due to SC-FDMA mechanism. It is also fully integrated with the LTE uplink open and closed-loop fractional power control for proper power allocation. The proposed interference-aware scheduler reduces the effect of the generated ICI mainly on CE users and also manages to provide fair resource sharing between CE and cell-center (CC) users. Simulation results show that the proposed framework improves CE users' throughput by around 5% compared to soft frequency reuse (SFR). It also reduces the probability of not being served to 1% -- compared to 10% in SFR.