Systematic Research on Concurrent Transmission Technology

時刻同期された複数のノードから同時に同一パケットを送信する同時送信技術により,マルチホップネットワークにおけるMAC層やネットワーク層を抜本的に簡略化することができる.本研究では,同時送信の物理層における性能解析に加えて,同時送信技術の効率化を図る技術の開発を進めている.具体的には,受信性能劣化を理論的に解析するため,周波数オフセットによるうなりの踏切率と平均フェージング期間とを定式化している.また,同時送信が適用可能な無線通信システムの条件を明らかにすべく,ZigBee, Wi-Sun, LoRaなどの無線通信規格への適用可能性をシミュレーション,エミュレーション,実機実験により評価している,さらに,MAC層での冗長性に着目した受信機会に基づく送信回数の制御や,複数ソースノードの同一スロット同時送信フラッディングにより,省電力化やスループット向上を可能とする手法についても検討を進めている.

Concurrent transmission (CT), a technique that intentionally transmits packets simultaneously through multiple synchronized nodes, has revolutionarily simplified MAC and network layer in wireless multi-hop networks. In this research, we aim to investigate the impact of CT on the physical layer as well as to further enhance the efficiency of the protocol itself. Firstly, we provide a systematic investigation on the physical layer effect of CT, which includes a theoretical analysis of the channel characteristics and comprehensive evaluations of the receiver performance with ZigBee, Wi-Sun, and the resent LoRa technology. Specifically, we theoretically derive the closed form of the average fading duration (AFD) of the beating under CT in order to quantify the receiver performance degradation resulted from CT. By extensive simulations, emulations, and experiments, we comprehensively evaluate the receiver performance of the aforementioned wireless technologies to identify the suitable systems for CT. Moreover, in order to reduce the network energy consumption, we propose to control the packet retransmissions based on the opportunity of successful receiving. Also, we evaluate the throughput improvement by conducting multiple CT floodings in parallel.