On the Performance of HARQ Protocols With Blanking in NOMA Systems

Abstract

In this paper, we investigate the throughput performance of single-packet and multi-packet hybrid-automatic repeat request (HARQ) with blanking for downlink non-orthogonal multiple access (NOMA) systems. While conventional singlepacket HARQ achieves high throughput at the expense of high latency, multi-packet HARQ, where several data packets are sent in the same channel block, can achieve high throughput with low latency. Previous works have shown that multi-packet HARQ outperforms single-packet HARQ in orthogonal multiple access (OMA) systems, especially in the moderate to high signal-tonoise ratio regime. This work amalgamates multi-packet HARQ with NOMA to achieve higher throughput than the conventional single-packet HARQ and OMA, which has been adopted in the legacy mobile networks. We conduct theoretical analysis for the throughput per user and also investigate the optimization of the power and rate allocations of the packets, in order to maximize the weighted-sum throughput. It is demonstrated that the gain of multi-packet HARQ over the single-packet HARQ in NOMA systems is reduced compared to that obtained in OMA systems due to inter-user interference. It is also shown that NOMA-HARQ cannot achieve any throughput gain with respect to OMA-HARQ when the error propagation rate of the NOMA detector is above a certain threshold.

Hybrid Automatic Repeat Request (HARQ) in Wireless Communications Systems and Standards: A Contemporary Survey

“…The multi-layer HARQ is interchangeably termed as a multi-packet or multi-channel HARQ in the literature. Multi-layer HARQ is a non-orthogonal protocol where multiple packets can be transmitted in the same time slot [193]. In a typical multi-layer HARQ system the transmitter is composed of multiple transmission channels, where packets are produced in parallel by multiple channels and are transmitted in parallel [194].…”

“…If the transmitter receives an ACK, it transmits new packets in the next time slot. On the contrary, if the transmitter receives a NACK, it transmits new packets, along with the retransmission of old packets [193] or additional parity bits only for the uncoded layers [195], [196].…”

Outage Performance of Cross-Packet HARQ

“…3.381.3], respectively. By identifying the integral of Mellin-Branes type in (5) with the generalized upper incomplete Fox's H function…”

“…So far, two main resource sharing modes have been proposed for MP-HARQ, including superposition coding (SC) and joint encoding, which are implemented in power domain and code domain, respectively. In particular, the idea of power-domain non-orthogonal multiple access (NOMA) was transferred to realize MP-HARQ in [5], where the SC was applied to multiplex all users' data. Furthermore, in [6], the SC was used to superimpose the redundant information of failed message and new information, which yields multi-layer HARQ.…”

Reinforcement Learning Aided Link Adaptation for Downlink NOMA Systems With Channel Imperfections

“…To augment NOMA advantages, AMC has been widely considered [1], [3], [7]- [9]. A joint power allocation and AMC algorithm for downlink NOMA was developed in [1] to improve the SE and user fairness.…”