Nobuyoshi Komuro

A green and reliable communication modeling for industrial internet of things

An improved protocol (HTP) is proposed through combining SW-ARQ and NCRT scheme.HTP protocol is a strategy which can optimize multiple performances at the same time.HTP protocol is proved to improve lifetime above 15% under same reliability.HTP protocol is proved to improve reliability by 10%45% under same lifetime.HTP protocol is more practicality which allows low complexity implementation. Green and reliable communication has great significance for Industrial Internet of Things. Unfortunately, because of the loss nature, achieving reliable transmission is challenging. In this paper, a novel hybrid transmission protocol (HTP) is proposed to maximize lifetime while the reliability is still guaranteed. The proposed protocol adopts Send-Wait automatic Repeat-Request protocol in hotspot areas to reduce the energy consumption and network coding based redundant transmission approach with adaptive redundancy level in non-hotspot areas to guarantee the reliability. The proposed protocol could improve the lifetime and shorten the delay on the premise of ensuring the reliability. Comparing with Send-Wait automatic Repeat-Request protocol, it can improve lifetime by 15%30% under the same reliability and improve the reliability by 12%45% under the same lifetime. Comparing with network coding based redundant transmission approach, the lifetime has increased by more than one time under the same reliability. Display Omitted

Maximum throughput analysis for RTS/CTS-used IEEE 802.11 DCF in wireless multi-hop networks

The purpose of this paper is to analyze the maximum throughput when using RTS/CTS (Request To Send/Clear To Send) in IEEE 802.11 Distributed Coordination Function (DCF) multi-hop networks with a novel approach. Wireless multi-hop networks, in which nodes communicate with each other and convey packets via intermediate nodes without centralized control, have gained increasing attention because of the extension of the wireless communication range associated with such networks. In wireless multi-hop networks, the IEEE 802.11 DCF based on the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) has been commonly used as a Medium Access Control (MAC) protocol. IEEE 802.11 DCF is specifically designed for single-hop wireless LANs, which makes quantitative analyses of the contention behaviors occurring at nodes in typical network topologies important. Although several quantitative throughput analyses for wireless multi-hop networks have been reported, few analyses have examined the use of RTS/CTS in IEEE 802.11 DCF multi-hop networks. While RTS/CTS is effective for avoiding packet collisions caused by hidden terminals, an overhead problem occurs due to the increase in the number of RTS/CTS control packets. As the number of RTS/CTS control packets increases, the collisions between RTS/CTS control packets occur more frequently. The analysis of networks that use RTS/CTS has been considered difficult because of the complex behaviors of RTS/CTS. The present paper introduces a novel approach to the analysis of throughput for networks that use RTS/CTS by considering one-way flow in string multi-hop networks. The end-to-end network maximum throughput is obtained by analyzing the maximum throughput of bottleneck nodes. This analysis provides the transmission failure probability considering not only RTS-RTS collisions but also the influence of the Network Allocation Vector (NAV). A simulation is carried out, and a comparison of the analytical and simulated results validates the proposed analytical expressions.

A Reasonable Throughput Analysis of the CSK/SSMA Unslotted ALOHA System with Nonorthogonal Sequences *

In this paper, the throughput performance of the CSK/SSMA ALOHA system with nonorthogonal sequences which combines the ALOHA system with Code Shift Keying using nonorthogonal sequences is analyzed. In this system, the nonorthogonal sequences are constructed by concatenating Mcon orthogonal sequences. The throughput performance of the CSK/SSMA ALOHA system with nonorthogonal sequences is analyzed in consideration that the number of packets changes at intervals of one orthogonal sequence. Moreover, the throughput performance of our system with Channel Load Sensing Protocol (CLSP) is also analyzed. We also examine the influence of unreachable control signal of CLSP. Consequently, it is found that the throughput performance of our system decreases significantly by this analysis. It is also found that the throughput performance of our system improves greatly by using CLSP. However, the unreachable control signal affects the throughput performance of this system, seriously.

Analytical Expression of Maximum Throughput for Long-Frame Communications in One-way String Wireless Multihop Networks

It is important to obtain analytical expressions of the maximum throughput in IEEE 802.11 Distributed Coordination Function multi-hop networks. In the previous works, the analytical expressions of the maximum throughput for one-way string multi-hop networks taking into account the signal capture effect were obtained. In other researches, the analytical expressions of the maximum throughput for one-way string multi-hop networks were also obtained, which are, however, valid only for short-frame communications. There is no analytical expression for maximum throughput, which is valid for long-frame communications. This paper presents an analytical expression of the maximum throughput for long-frame communications. For the long-frame-communication analysis, we make different assumptions from those in the previous-analyses. In the short-frame-communication analyses, it is assumed that all nodes always have frames. In the long-frame-communication analysis, however, it should be assumed that every equal to or more than three nodes in a string-topology network have frames. The comprehension of this behavior is the most important progression in this paper. The assumptions and the analytical expression are validated by the simulation results.

End-to-end throughput and delay analysis for IEEE 802.11 string topology multi-hop network using Markov-chain model

This paper proposes the analytical expressions for the IEEE 802.11 string-topology multi-hop networks using Markov-chain model. For achieving that, the proposed analysis procedure includes two proposals, which are: (i) Bianchis Markov-chain model is modified for considering a relationship between the backoff timer and frame length, and (ii) the interferences, such as hidden node collision and carrier sensing, among network nodes are expressed by merging the proposed Markov-chain model and airtime expression. The analytical expressions are verified by comparisons with simulation results.

Priority and admission control for assuring quality of I2V emergency services in VANETs integrated with Wireless LAN Mesh Networks

In this paper, we introduce a new priority and admission control mechanism for applications in the Vehicular Communication Networks (VCNs). The adopted network architecture integrates Vehicular Ad-hoc Networks (VANETs) based on the standard IEEE 802.11p and Wireless LAN Mesh Networks (WMNs) based on IEEE 802.11s. The proposed scheme is designed to ensure seamless provision of infrastructure-to-vehicle (I2V) emergency services such as video data streaming between content servers and vehicles. Simulation experiments are intensively investigated to evaluate the effectiveness of the proposed priority and admission control mechanisms. The results show that the proposed mechanism minimizes the end-to-end delay and increases the throughput as well as packet delivery ratio (PDR) of the emergency data flow.

Receiving opportunity control used admission control scheme for wireless multi-hop networks

The purpose of this study is to guarantee Quality of Service (QoS) in wireless multi-hop networks by introducing an admission control scheme. In wireless single-hop networks, IEEE 802.11e Enhanced Distributed Channel Access (EDCA) is the standard for QoS control. However, to control QoS, it is necessary to modify the currently used IEEE 802.11 Distributed Coordination Function (DCF)-compliant terminals and to improve the throughput performance of IEEE 802.11e EDCA, which significantly deteriorates in heavy traffic. The authors previously proposed a per-flow QoS control scheme, called Receiving Opportunity Control in MAC Frame (ROC), in which the Access Point (AP) intentionally does not return ACKs for low-priority data frames. Using ROC and IEEE 802.11 DCF mechanisms, the back-off timer of low-priority flows increases and higher transmission opportunities are provided for high-priority flows. Although ROC causes slight performance degradation in total throughput, it is not necessary to modify existing terminals and ROC provides flexible and more fine-tuned QoS control in heavy loads compared to IEEE 802.11e EDCA. This paper proposes a novel scheme to guarantee the QoS of high-priority flows in wireless multi-hop networks with ROC-employed per-flow admission control. In the proposed scheme, the edge APs that connect terminals apply ROC to low-priority flows according to the buffer occupancy rate at the network nodes, and the admission control suppresses the inflow of low-priority frames to core networks. As a result, QoS of high-priority flows is guaranteed without modifying existing terminals. Simulation results show that the proposed scheme can achieve QoS, as required, in comparison to conventional schemes.

Efficient Thread Mapping for Heterogeneous Multicore IoT Systems

This paper proposes a thread scheduling mechanism primed for heterogeneously configured multicore systems. Our approach considers CPU utilization for mapping running threads with the appropriate core that can potentially deliver the actual needed capacity. The paper also introduces a mapping algorithm that is able to map threads to cores in an time complexity, where is the number of cores and is the number of types of cores. In addition to that we also introduced a method of profiling heterogeneous architectures based on the discrepancy between the performances of individual cores. Our heterogeneity aware scheduler was able to speed up processing by 52.62% and save power by 2.22% as compared to the CFS scheduler that is a default in Linux systems.

Channel assignment for multi-interface multi-hop wireless networks

For public safety or military purposes, it is needed to introduce a unified architecture of multi-hop wireless networks that include both flat (ad-hoc) networks and hierarchical (mesh) networks, where devices can access multiple channels using multiple radio interfaces thanks to the advance of mobile devices. In such networks, it is a challenging issue how to assign channels in a distributed manner by avoiding interference and maintaining connectivity. In this paper, we propose a distributed heuristic channel assignment scheme, based on channel utilization and even adaptive against jamming. We use the OPNET simulator to perform a rigorous simulation and confirm that the performance of the proposed scheme outperforms existing schemes.

Multi-channel MAC protocol with channel grouping in wireless ad-hoc network

This paper proposes a MAC protocol using multiple control channels for multi-channel ad-hoc network. In the proposed protocol, all channels are divided into some groups. Each group has a control channel. All nodes hops the control channels for searching a receiver. Because of using multiple control-channels, control frame collisions and the effect of searching overhead are mitigated in the proposed protocol. This paper also derives the optimum number of groups and the optimum contention window size, which maximizes the system throughput. Analysis results and simulation results show the effectiveness of the proposed protocol.