Conventional Retransmission Scheme Research Articles

On the Performance Evaluations of Cooperative Retransmission Scheme for Cell-Edge Users of URLLC in Multi-Carrier Downlink NOMA Systems.

Non-orthogonal multiple access (NOMA) has a key feature that the cell-center user (CCU) has prior information about the messages of the cell-edge user (CEU) in the same user-pair. It means that CCU can be used for retransmission when the CEU requests retransmission. As ultra-reliability and low-latency communication (URLLC) requires high-reliability constraints (e.g., 99.999%), using CCU for retransmission can be useful to satisfy the reliability constraint. In this study, to ensure the reliability of CEU, cooperative retransmission (CR) scheme for downlink NOMA systems is proposed. And the CR scheme is evaluated with Block error rate (BLER) considering reliability and with packet loss rate (PLR) in terms of reliability and latency constraints. And the evaluation results showed that the proposed CR scheme can satisfy the target BLER for URLLC low SNR compared to the conventional retransmission scheme, and showed the improved PLR compared to the conventional retransmission scheme in low SNRs.

Probabilistic Network Coding Based on Buyer/Seller Games for Retransmissions in Wireless Networks

In wireless networks, retransmissions are used by senders to recover lost packets. The conventional retransmission schemes usually retransmit only one lost packet each time, resulting in a low retransmission efficiency. However, using broadcasting nature of a wireless channel with network coding (NC), we can recover more than one lost packet per transmission. Different from single-sender multiple-receiver wireless networks as considered in the existing works, this paper explores the ways to use NC for retransmissions in multiple-sender multiple-receiver scenarios. In addition, this paper also aims to investigate the advantages and shortcomings of using NC in retransmissions. In order to maximize the gain and minimize the impact in NC retransmissions, a probabilistic network coding retransmission (PNCR) scheme is proposed, where a buyer/seller game-theoretic approach is adopted to optimize the performance. The experimental results confirm the effectiveness of the PNCR scheme.

IEEE 802.11 무선랜에서의 멀티미디어 전송을 위한 스케일러블 비디오 코딩 인지형 재전송 기법

멀티미디어 스트리밍을 위해 널리 사용되고 있는 스케일러블 비디오 코딩 (Scalable Video Coding: SVC)의 경우 가변적인 네트워크 상황에 적응적으로 대처하기 위해 기본 계층과 향상 계층으로 나누어 데이터를 인코딩하여 전송하게 된다. 특히 향상 계층의 디코딩은 기본 계층의 데이터가 수신되었을 때 가능하다는 특성을 가지고 있다. 이러한 특성에도 불구하고 IEEE 802.11 무선랜에서의 재전송 기법은 기본/향상 계층의 특성을 고려하지 않고 설계되어 있다. 본 논문에서는 스케일러블 비디오 코딩의 특성을 고려한 새로운 재전송 기법을 제안한다. 제안한 재전송 기법은 기본 계층과 향상 계층을 나누어서 채널상태에 따라 디코딩에 필요한 수 만큼의 데이터를 재전송하여 불필요한 재전송을 방지하고 총 전송시간을 감소시킨다. 시뮬레이션 결과는 제안한 재전송 기법이 기존의 재전송 기법보다 불필요한 데이터 전송을 12.6% 감소시키며 이로 인해 전송 시간도 6.6~19.1% 만큼 감소됨을 보여준다. Scalable video coding (SVC) encodes multimedia data into a base layer and enhancement layers to cope with variable network conditions in an adaptive manner. In SVC, enhancement layers can be decoded only when the base layer is successively received. However, existing works on SVC transmissions in IEEE 802.11 WLANs do not fully investigate this characteristic and thus their performance can be degraded. In this paper, we propose a SVC-aware retransmission (SAR) scheme in IEEE 802.11 WLANs. The SAR scheme applies different retransmission policies for base and enhancement layers by obtaining the optimal number of frames to be retransmitted. As a result, the SAR scheme can reduce unnecessary retransmissions and minimize the transmission latency. Simulation results demonstrate that the SAR scheme can reduce unnecessary data transmission by 12.6% and the transmission latency by 6.6~19.1% compared to conventional retransmission schemes.