Low-complexity multiple-relay strategies for improving uplink coverage in 4G wireless networks

In this work we present low-complexity coded-modulation strategies for distributed relaying in 4G wireless networks. The primary goal of these strategies is to improve coverage on the uplink while retaining high spectral efficiency through multiuser spatial-multiplexing using two or more relays between the users and the base station. We contrast layer 2 techniques based on full decoding at relay stations and simple compression-based (quantization) techniques with QAM alphabets. Mutual-information and error-exponent analysis clearly show the benefits of distributed quantization both in the high and medium spectral efficiency regions. We further present these results in the context of evolving LTE-Advanced standardization activities, primarily by suggesting adaptations to standardized coding and retransmission mechanisms for a multiple-relay system.