An Enhanced Hybrid Automatic Repeat Request (HARQ) Scheme for Non-orthogonal Multiple Access (NOMA) System of 5G

Abstract

Non-orthogonal multiple access (NOMA) has been proposed as a very promising candidate multiple access scheme for the 5th generation of wireless communication systems. The existing works of NOMA mainly focus on capacity analysis, power control, user pairing and scheduling, or combination with other technologies such as massive multiple-input multiple-output (massive MIMO) antenna system and seldom works have been found to design the hybrid automatic repeat request (HARQ) for NOMA system, which is one of the most important aspects for reliable data transmission in practical wireless communication systems. This paper investigates the sophisticated HARQ scheme design for NOMA system and proposes a novel retransmission scheme to combat the inter-user interference in the retransmission. In the proposed scheme, the superposition signals in retransmission are carefully designed in order to enable self-interference cancellation at the receiver side by exploiting the advanced interference cancellation processing. Simulation results show the proposed scheme is very effective and achieve much better performance than the existing retransmission scheme.