EAM-LoRaNet: Energy Aware Multi-hop LoRa Network for Internet of Things

LoRa Technology is one of the devices used on Low-Power Wide Area Networks (LPWAN), which is a viable alternative wireless communication technology for the Internet of Things (IoT). The LoRa device is meant to traverse a large distance while using minimal power. However, because it uses single-hop communication, the Gateway's farthest nodes will die prematurely as a result of the increased energy usage. This research attempts to improve the range of LoRa networks utilizing multi-hop uplink communication while also reducing energy consumption by adjusting the LoRa transmission power to the lowest possible dBm in each hop. As a network model, a star topology-based tree made of some rings with a gateway as the central point is chosen. The performance of two forms of uplink communication, single-hop and multi-hop models was tested in terms of energy consumption and coverage. The results show that the network structure in the multi-hop uplink model can extend coverage over a greater distance while using less energy than the single-hop uplink model. This model can be used as a supplement to the LPWAN's uplink communication in the IoT to enhance the network's coverage range and lifetime

Scalability Analysis of a LoRa Network under Imperfect Orthogonality

Low-power wide-area network (LPWAN) technologies are gaining momentum for internet-of-things (IoT) applications since they promise wide coverage to a massive number of battery-operated devices using grant-free medium access. LoRaWAN, with its physical (PHY) layer design and regulatory efforts, has emerged as the widely adopted LPWAN solution. By using chirp spread spectrum modulation with qausi-orthogonal spreading factors (SFs), LoRa PHY offers coverage to wide-area applications while supporting high-density of devices. However, thus far its scalability performance has been inadequately modeled and the effect of interference resulting from the imperfect orthogonality of the SFs has not been considered. In this paper, we present an analytical model of a single-cell LoRa system that accounts for the impact of interference among transmissions over the same SF (co-SF) as well as different SFs (inter-SF). By modeling the interference field as Poisson point process under duty-cycled ALOHA, we derive the signal-to-interference ratio (SIR) distributions for several interference conditions. Results show that, for a duty cycle as low as 0.33%, the network performance under co-SF interference alone is considerably optimistic as the inclusion of inter-SF interference unveils a further drop in the success probability and the coverage probability of approximately 10% and 15%, respectively for 1500 devices in a LoRa channel. Finally, we illustrate how our analysis can characterize the critical device density with respect to cell size for a given reliability target

南極昭和基地におけるIoT 活用に向けた920 MHz 帯小電力通信試験

2017 年より国内での利用が始まった920 MHz 帯小電力無線システム用の電波を活用し，昭和基地における観測機器のデータ収集を始めとした基地インフラの監視を実現することを目的として，第61 次南極地域観測隊において東オングル島及びその周辺地域における920 MHz 帯電波の到達状況と既存の基地観測への影響を調査した．調査においてはLoRaマルチホップが可能な通信機器を製作し，隊員が携帯する送信装置から発信されるGPS の位置・時刻情報を，昭和基地基本観測棟の3 階階段手摺に設置したLoRa ゲートウェイで受信することで，各地における受信信号強度や信号対雑音比などのデータを収集した．越冬期間中6 回に及ぶ調査の結果，920 MHz 帯電波の特性から小電力にも関わらず広い範囲で電波の到達が確認され，将来の観測への応用及び，基地インフラの監視等IoT 活用への応用が期待できることが判明した．LoRa communication protocol using 920 MHz-band has been opened to thepublic for Internet of Things (IoT) application and a wide variety of telemeter usage since2017 in Japan. It is expected to be used for collection of scientific observations and monitoring data at Syowa Station. In JARE61, we have investigated the radio environment of the 920 MHz-band, and its possible impact on the ongoing scientific observations in Syowa Station．A member of the wintering team carries a handy transmitter in the nearby area of Syowa Station, East-ongul Island. The transmitter sends GPS location and time data to the receiver (LoRa gateway) located at the roof handrail of the observation building. Six surveys have been conducted, and we confirmed the reachability of the radiosignal in and outside of the Syowa Station. The possibilities of the 920 MHz-bandapplication have been suggested to use monitoring station infrastructure and scientific observations