Shared Hybrid ARQ With Incremental Redundancy (SHARQ IR) in Overloaded MIMO Systems to Support Energy-Efficient Transmissions

Abstract

Multiple Input and Multiple Output is a technology through which data are transmitted over the channel through multiple antennas. However, during its deployment and implementation, some pragmatic issues arise such as interference, multipath fading and noise leading to potential packet losses and consume substantial energy. To address such issues, Hybrid ARQ transmissions provide effective means for error correction, especially in a noisy wireless channel. More often few bits in packets are found to be in error and it is unnecessary to use the entire MIMO channel for retransmission to correct these errors. Hence, this paper proposes a novel approach, i.e., Shared Hybrid ARQ (SHARQ IR) using the piggyback technique in an overloaded MIMO system where the transmitting antennas are more than the receiving antennas. Additionally, the concept of a simple retransmission method is used to transform an overloaded MIMO system into either the critically loaded or under loaded MIMO systems. Simulation results outperform the contemporary approaches through reduced BER and 20% throughput gain. Such improvements have the potential to support energy-efficient transmissions for encouraging green IoT applications.

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

“…AoI is an important metric in real-time applications, where the access point (AP) is always looking for the updated information from the end devices. On the other hand, a multiuser overloaded MIMO system with HARQ-IR is considered in [249] where the number of transmitting antennas is larger than the number of receiving antennas. In the proposed model, retransmissions and new transmissions share the same MIMO channel.…”

Post-Cancellation-Based LLR Refining for MIMO Multiple ARQ Systems

“…Because the proposed LLR refining scheme needs to be performed after the conventional reception procedure is over, the overall latency for the receiver increases. Thus, for the HARQ protocols designed for a low-latency transmission [2,3,7,29], the overall process of the receiver with LLR refining has to be redesigned. Furthermore, because the LLR refining is performed for non-terminated packets that will be retransmitted, the proposed scheme cannot directly improve the performance of initially transmitted packets.…”

“…When HARQ is employed to multiple-input multiple-output (MIMO) systems, various applications are possible by using the natures of HARQ retransmissions and MIMO transmission/reception. Thus, many studies have been conducted on MIMO systems with HARQ in recent years [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], e.g., the transmission efficiently analysis [16], utilization of the acknowledgment/non-acknowledgment (ACK/NACK) feedback bundling [17], modulation design considering a MIMO-coordinated multi-point scenario [18], optimization of the energy efficiency for a point-to-point massive MIMO system [19], adaptive modulation and coding design [20], integration for vehicle-to-vehicle communications [21], etc.…”

“…In particular, it is possible to simultaneously operate multiple HARQ processes using multiple inputs. MIMO multiple ARQ (MMARQ) systems simultaneously operate multiple HARQ processes in antenna domain, e.g., each transmit antenna sends a packet having an independent HARQ process from the other packets with the same time and frequency resources [23][24][25][26][27][28][29][30]. Unlike MIMO single ARQ (MSARQ) systems that operate a single HARQ process (e.g., a single packet) in the antenna domain, e.g., the modulated symbols of a packet are spatially multiplexed and sent together from all transmit antennas [23], MMARQ systems can benefit from a partial decoding success, i.e., a situation where some of the packets sent during a given transmission time interval (TTI) are successfully decoded.…”

“…The performance characteristics of MMARQ systems according to the combining scheme at the receiver were analyzed in [27], and a hybrid combining scheme based on the interference-to-noise reformulation was developed in [28]. In [29], a shared HARQ scheme using the piggyback technique was proposed for overloaded MIMO systems. In [30], a Kalman filtering-based combining scheme applicable for both MMARQ and MSARQ regardless of the employed HARQ retransmission strategy was investigated, which was extended to perform iterative detection and decoding for MSARQ systems in [22].…”