Wireless communications in industrial environments are seriously affected by reliability and performance issues, due to the multipath nature of obstacles within such environments. In order to utilize wireless systems for machineto-machine applications in industrial environments, it is necessary to investigate and model their channel characteristics for optimal design and reliability assessment. However, the wireless channel characterization in such environments has not been sufficiently addressed in the literature within the scope of our knowledge. In this paper, to shed light on the channel modeling for plant applications, we measure and analyze the indoor channel characteristics in a typical thermal power plant. Our results indicate that the channel characterization of the plant environment is specific when compared with the general environments such as houses and offices. The findings in this paper provide a useful guidance to the design of wireless system for the realization of reliable control systems in power plants. C⃝ 2016 Wiley Periodicals, Inc. Electron Comm Jpn, 99(11): 3-12, 2016; Published online in Wiley Online Library (wileyonlinelibrary.com).
The standardization of IEEE802.11n aims to achieve 100Mbps at MAC-SAP (Medium Access Control -Service Access Point). The Frame Aggregation scheme in which MAC (Medium Access Control) frames are aggregated into one PHY (Physical) frame is proposed as the main MAC technique of IEEE802.11n, because it decreases MAC overhead. The Block Ack mechanism of IEEE802.11e is applied as a selective repeat method of the Frame Aggregation. In this paper, we propose the Extended Block Ack mechanism as a selective repeat mechanism to be adapted to the Frame Aggregation scheme. We present the performance evaluation to compare the throughput of the Extended Block Ack mechanism and the Legacy Block Ack of IEEE802.11e and show that the average improvement is expected to be around 10% and the maximum improvement is about 39% compared with the conventional method.
The next generation wireless LAN standard IEEE 802.11ax aims to provide improved throughput performance in dense environments. We have proposed an efficient channel sounding mechanism for DL-MU-MIMO that has been adopted as a new sounding protocol in the 802.11ax standard. In this paper, we evaluate the overhead reduction in the 802.11ax sounding protocol compared with the 802.11ac sounding protocol. Sounding is frequently performed to obtain accurate channel information from the associated stations in order to improve overall system throughput. However, there is a trade-off between accurate channel information and the overhead incurred due to frequent sounding. Therefore, the sounding interval is an important factor that determines system throughput in DL-MU-MIMO transmission. We also evaluate the effect of sounding interval on the system throughput performance using both sounding protocols and provide a comparative analysis of the performance improvement. key words: channel sounding protocol, IEEE 802.11ax, wireless LANs
Measuring the living condition and health status of users using small sensing devices and collecting the data of each user over wireless networks is expected to be a new trend in healthcare. Body Area Network (BAN) is an emerging area of personal data communications that will facilitate the capture of data and its collection. Although the IEEE 802.15.6 standard for wireless body area networks was created for this purpose, it is very complex and is unsuitable for ultra low power sensors. A new BAN specification, under the Technical Committee (TC) on SmartBAN, is now being considered in the European Telecommunications Standards Institute (ETSI) targeting ultra low power devices. Some of the technical requirements of the new Smart BAN system includes ultra-low power consumption, coexistence with other wireless systems, a timely access mechanism and optimum control of quality of service (QoS) for emergency signals. A simple and energy efficient MAC/PHY system has been proposed by the authors as part of the ETSI TC Smart BAN specifications.In this paper, we introduce and evaluate our proposed Smart BAN system which is based on two channels, a control channel and a data channel. The control channel is used for announcements from which both nodes and neighboring hubs are able to gather information for use in co-existence algorithms as well as for initial connection setup. Our proposed system uses simple time division multiple access (TDMA) in the data channel so that the power consumption of nodes is kept low. A shared access mechanism has also been proposed to reduce the latency of emergency signals. We evaluate the access delay and power consumption of our system in this paper, and show that the proposed shared access mechanism reduces the latency of emergency signals.
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