It is generally recognized that efficient multiplexing of users with highly diverse requirements needs a flexible frame structure. For a new 5th generation mobile networks (5G) air interface, the hybrid automatic repeat request (HARQ) solution should also be revised to harvest all possible performance benefits that can be obtained with a flexible frame structure. In this paper, we outline a number of HARQ enhancements and design principles for a 5G wide area solution. This includes a flexible asynchronous HARQ scheme with options for dedicated per-link configurations of feedback timing and multi-bit richness. Among others, the proposed solution supports asymmetric link operation, network implementations with different fronthaul latencies, and multi-bit feedback to facilitate variable block length HARQ retransmissions for improved resource utilization. Numerical results are presented for different link configurations.
['Saeed R. Khosravirad', 'Gilberto Berardinelli', 'Klaus I. Pedersen', 'Frank Frederiksen']
Enhanced HARQ Design for 5G Wide Area Technology