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en: Perspectives on IoT-oriented network simulation systems

en: The Internet of Things (IoT) paradigm is assumed to be a major component in the present and future Internet, with forecasts claiming a humongous number of devices connected in the near future, and applications fields spanning from agriculture, to healthcare. Despite this, the standardization efforts have not yet resulted in widely adopted standards, and the market is fragmented into multiple solutions both at physical andcommunication protocol levels. Moreover, IoT systems exacerbate the usual test bed limitations, e.g., scalability(very large number of devices), hardware compatibility, space, and price. Due to the above problems, simulation tools become an extremely interesting tool for studying IoT systems both for academia (newalgorithms), standardization (new protocols), and industry (what-if analysis). In this paper we will discuss what are the most relevant features and models that a simulation tool like ns-3 should prioritize to enable the above-mentioned needs from academia, standardization, and industry, and if they are achievable in the short,medium, or long term.

en: Computer Networks

ja: Computer Networks


en: 自動車内における高信頼通信の実証的検討

ja: 自動車内における高信頼通信の実証的検討

en: 近年，自動車内における快適性と利便性の向上に，小型かつ配線が不要なため設置が容易な無線センサノードの活用が検討されている．このとき，コスト削減のためには広く普及した汎用デバイスを利用することが望ましいが，WiFiやZigBeeに代表される既存プロトコルでは，実用上十分な信頼性が得られない．そこで本論文では，既存のデバイスを用いて，所定の値以下の遅延で十分に高い成功率で完了する方法について実証的に検討する．具体的には，自動車内の電波伝搬特性を実験によって明らかにした上で，オーバーヒアしたフレームを中継することでロス率を下げる代理通信方式を提案する．そして，CSMA/CAのコンテンションウィンドウサイズ調整を行い，必要となる回線速度を明らかにする．最後に，実験データに基づく性能評価によって，自動車内でのセンサノード間通信が，10ms以内に99.9%以上の成功率で達成できることを確認した．

en: The Transactions of the Institute of Electronics, Information and Communication Engineers B

ja: 電子情報通信学会論文誌(B)


en: Enhanced Fallback+: An Efficient Multiconstraint Path Selection Algorithm for QoS Routing

en: In future high-speed networks, provision of diverse multimedia services with strict quality-of-service (QoS) requirements, such as bandwidth, delay and so on, is desired. QoS routing is a possible solution to handle these services. Generally, a path selection for QoS routing is formulated as a shortest path problem subject to multiple constraints. However, it is known to be NP-complete when more than one QoS constraint is imposed. As a result, many heuristic algorithms have been proposed so far. The authors proposed a path selection algorithm Fallback+ for QoS routing, which focuses not only on the path selection with multiple constraints but also on the efficient use of network resources. This paper proposes an enhanced version of Fallbacks, named Enhanced Fallback+, where in a shrewd way, it keeps tentative paths produced in the conventional Fallback algorithm with Dijkstra's algorithm. Simulation experiments prove the excellent performance of Enhanced Fallbacks, compared with the original Fallback+ and other existing path selection algorithms.

en: IEICE Transactions on Communications

ja: IEICE Transactions on Communications


en: A Study on Estimation of Mobility of Terminals for Hierarchical Mobility Management Scheme

en: Hierarchical Mobile IPv6 (HMIPv6) has been proposed to manage the mobility of Mobile Terminals (MTs) hierarchically to reduce packet losses during local handover. HMIPv6 uses a mobility manageable router in a domain visited by the MTs to manage the micromobility of the MTs. The router is called Mobility Anchor Point (MAP). As a hierarchical mobility management scheme based on HMIPv6, we have already proposed a multilevel hierarchical distributed IP mobility management scheme to manage the mobility of MTs in a decentralized manner using multiple MAPs. Our scheme manages the mobility of an MT using a MAP having a suitable management domain. This usage of MAPs aims to efficiently decentralize the load of mobility management. Our scheme estimates the movement speed of the MT and then estimates the mobility of the MT based on the estimated movement speed of the MT to achieve the objective. However, recent simulation results obtained with more realistic mobility model indicate that our scheme has two problems in estimating the mobility of MTs: One is that our current scheme misestimates the movement speed of an MT in some cases, and the other is that our current scheme does not notice the changes in the mobility of an MT when the MT decelerates and stays in the same access area for a long time. Thus, an enhanced mobility estimation method is proposed in this paper. The enhanced method has an ability to estimate the movement speed of MTs more correctly and an ability to urge decelerated MTs to degrade their MAP quickly. Finally, the performance of the proposed mobility estimation method is evaluated using simulation experiments. The simulation results show that the enhanced method allows our scheme to estimate the mobility of MTs more correctly and so achieve more efficient load sharing.


en: A Design for Integrated Wireless Network with Flexible Bandwidth Assignment

en: As various mobile communication systems have developed, dramatically integrated wireless network, where users can communicate seamlessly via several wireless access systems, have become expected. At present, there are many studies of integrated wireless network, but no study of a network design method. Therefore, in this paper, we discuss a network design method for integrated wireless networks. Because of the handover procedure, the network design where adjacent base stations are connected to the same router, regardless of radio system type, is simply considered. However, in such a design, where mobile users crowd into a particular area and users' access to the base stations located there increases, the load of these accesses is centralized to the single router. To overcome this problem, we propose a new network design wherein the base stations of heterogeneous wireless communication systems, the service areas of which overlap, are connected to a different router. In the proposed network design, although users' accesses are concentrated on the base stations located in a particular area, users in that area can be assigned bandwidth of several upper links according to the access conditions of the base stations in neighboring areas. Finally, we show the excellent performance of the proposed design by simulation experiments.


en: A Mobility-Based Terminal Management in Ipv6 Networks