Constellation Constraining-Based Coverage Enhancement Technique for MTC Devices in LTE-A

Cellular-based machine type communication (MTC) is expected to be a major technology revolution in future. Several MTC specific enhancements have been proposed by 3GPP for long term evolution-advanced (LTE-A), including coverage enhancement (CE). Improving SNR at the receiver is considered to be one of the preferred ways to enhance the coverage. In this letter, we propose to use a priori known bits in receiver-centric constellation constraining (CC) technique to improve SNR. We have identified two categories of known bits: 1) reserve and 2) conditionally deterministic bits, to improve SNR of physical broadcast channel (PBCH) of LTE-A using CC technique as a novelty. This proposed solution is software implementable and does not require any changes to transmitter and standard. Closed form analytical expression for probability of bit error has been derived and simulation results are shown to match with analytical results closely. Simulation results show that at the operating point of 1% block error rate (BLER), as specified by 3GPP, the proposed technique achieves a significant SNR gain of 1.8 dB.