LTE Rel-13 MTC device receiver algorithms for coverage enhancement

Machine Type Communication (MTC) device for cellular communication is being defined by 3GPP based on LTE in Rel-12 and Rel-13. Low cost has been the major objective of the definition for Rel-12 based specification. In Rel-13, coverage enhancement of MTC devices has been the major focus along with reduced power consumption, complexity and narrow bandwidth operation. Coverage enhancement (CE) of ∼15dB is expected to be achieved by using multiple power aggregation techniques, e.g. boosting Power Spectral Density (PSD), repetitions and relaxed requirements in few other cases. In CE scenarios, many of the receiver algorithms designed for normal coverage (NC) do not perform well. Requirement to operate at very low SINR changes the problem setup for few receiver algorithms. In this paper we introduce multiple UE receiver algorithms spanning various receiver functions, for coverage enhancement with reduced complexity. Specifically, practical cell search algorithm with complete procedure with joint time and frequency uncertainty hypothesis, novel timing estimation algorithm using PBCH, improved Channel Quality Index (CQI) estimation and novel method for opportunistic early decoding criterion based on mutual information metric. Algorithms proposed in this paper are first of its kind addressing coverage enhancement requirement for 3GPP LTE Rel-13 MTC devices. We show the performance of different algorithms proposed at very low SNRs as required for CE case.