Reception Ratio Research Articles

An Experimental Study on the Use of LoRa Technology in Vehicle Communication

Among the profound changes that will come with the Internet of Things is vehicular communication. Shortly the vehicles will be connected between themselves (V2V) and their infrastructure. For the full achievement of these objectives, the challenges of new technologies are enormous due to the requirement of high reliability, high speed, and low latency. None of the technologies under development for this application has reached a satisfactory stage be assumed to as definitive. The LoRa technology, operating at frequencies below 1 GHz, presents a good signal spread and penetration in obstacles. It has a considerable range, open-source, simple, robust, and low-cost hardware, vast configuration possibilities, and applications, ranging from medicine to agriculture, do not use licensed bands. The tests proved to have good reach even in a dense urban environment. They can become a viable alternative in applications that require short message transmissions with few characters that do not require the constant sending of information packages. The purpose of this work is to evaluate the communication between V2I, V2V, and stationary vehicles using LoRa technology in field tests with measurements of signal strength, reception ratio, and signal-to-noise ratio. It will be using different SF (scattering factors) inherent to LoRa (SF7 and SF12) and evaluate the influence of the Doppler effect on communication.

Multi-Hop Dynamic Map Data Propagation Algorithm for Clustered Vehicular Networks

To ensure the driving safety in vehicular network, it is necessary to construct a local dynamic map (LDM) for an extended range. Using the standard vehicular communication protocols, however, vehicles can construct the LDM for only one-hop range. Constructing large-scale LDM is highly challenging because vehicles randomly change their position. This paper proposes a dynamic map propagation (DMP) method, which builds a large aggregated LDM data using a multi-hop communication. To reduce the data overhead, we introduce an efficient clustering method based on a half-circle of the forwarder’s wireless range. The DMP elects one forwarder per cluster, which constructs LDM and forwards it to a neighbor cluster. The inter-cluster interference is minimized by allocating a different transmit window to each cluster. DMP copes with a dynamic environment by frequently re-electing the forwarders and their associated transmission windows. Simulation results reveal that DMP enhances the forwarders’ reception ratio by 20%, while extending LDM dissemination range by 29% over a previous work.

REFIACC: Reliable, efficient, fair and interference-aware congestion control protocol for wireless sensor networks

The recent wireless sensor network applications are resource greedy in terms of throughput and network reliability. However, the wireless shared medium leads to links interferences in addition to wireless losses due to the harsh environment. The effect of these two points translates on differences in links bandwidth capacities, lack of reliability and throughput degradation. In this study, we tackle the problem of throughput maximization by proposing an efficient congestion control-based schedule algorithm, dubbed REFIACC (Reliable, Efficient, Fair and Interference-Aware Congestion Control) protocol. REFIACC prevents the interferences and ensures a high fairness of bandwidth utilization among sensor nodes by scheduling the communications. The congestion and the interference in inter and intra paths hot spots are mitigated through tacking into account the dissimilarity between links’ capacities at the scheduling process. Linear programming is used to reach optimum utilization efficiency of the maximum available bandwidth. REFIACC has been evaluated by simulation and compared with two pertinent works. The results show that the proposed solution outperforms the others in terms of throughput and reception ratio (more than 80%) and can scale for large networks.

IEEE 802.15.4a와 센서를 이용한 실시간 실내위치인식 시스템

고정노드 2개를 사용하는 이변측위 방법은 건물이나 선박의 복도와 같은 좁은 공간에서 실시간 실내위치인식 시스템 분야에 사용되고 있다. 하지만 이러한 공간에서 고정노드 간 거리가 멀어지거나 장애물이 있을 경우 위치정보 수신율 저하로 인하여 이동노드(사용자)의 위치 추정이 어렵게 된다. 본 논문에서는 이와 같은 문제를 보완하기 위하여 IEEE 802.15.4a Chirp 신호를 기반으로 사용자에게 부착된 센서를 통하여 위치를 계산할 수 있는 보폭 측정 알고리즘을 이용하는 새로운 실시간 실내위치인식 시스템을 제안한다. 제안한 시스템은 다리길이 측정을 위한 초음파센서, 사용자의 방향을 인식하는 지자기 센서 및 다리사이 각을 획득하기 위한 관성센서로 구성된다. 실험 결과 제안한 시스템은 통신도달성이 결여된 구간에서 기존 실내위치인식 방법에 비해 2배 이상 정교한 결과를 나타내었다.