Design of Low Latency and High Reliable Industrial Wireless Lan System

Industrial wireless system, particularly Factory Automation (FA) system has been recognized as one of potential applications in machine type communication. A wireless system for an industrial network is preferable due to its primary advantages: flexibility for controlling mobile clients, low-complexity installation and low-cost maintenance by reducing physical connectivity in factory environment, and also applicable for hazardous sites. Several existing wireless technologies have been deployed for industrial wireless system, including Zigbee, WirelssHART and WLAN based system. However, the existing technologies have several limitations in terms of low throughput, poor reliability, as well as non deterministic. These drawbacks restrict the deployment of these technologies in critical industrial control system where low latency and high reliability are the primary requirements. In order to overcome the limitations of current technology, this thesis proposes low latency and high reliable industrial wireless LAN system, particularly for FA system. Specifically, two main topics are presented: (1) Design of high throughput of WLAN PHY transceiver for industrial wireless system. The first topic is presented to deal with fast transmission requirements. Typically, a WLAN system is deployed for home or office network scenarios. Since this scenario incorporates large data payload, throughput metric is higher priority than latency metric. Hence, to adopt WLAN based PHY transceiver for industrial wireless network, the issue of latency should be addressed as the top priority with respect to maintain reliability performance as well as low-complexity implementation. Therefore, as a first step, cross layer design approach is carried out in order to achieve optimum trade-off between QoS performance, implementation complexity, as well as lower power consumption. Later, the obtained PHY system parameters from cross layer design stage are employed for designing PHY transceiver system. In addition, several design optimizations are also incorporated during designing transceiver system that was conducted based on Model based RTL design. (2) Retransmission diversity based on channel selectivity scheme. The second part discusses performance improvement, specifically reliability performance in regard to low latency communication. The proposed work leverages frequency diversity that is available in the employed transmission bandwidth. A low complexity sub channel selection method by utilizing adjacent channel selection is considered. To confirm the effectiveness of this proposal, the performance results in terms of latency and reliability are evaluated, covering link level and system level performance of the FAWLAN system. Hardware implementation and verification result confirms that the designed PHY system achieves processing latency for about 13μs, corresponding to total transmission delay for about 85μs. This performance could satisfy the performance target in terms of FA WLAN protocol which requires transmission delay less than 100μs. Furthermore, the proposed PHY design also offers better normalize power consumption per transmitted bit (e.g. energy efficiency performance) for around 6.76 mJ/Mb. Moreover, the proposed retransmission scheme could also offer control duration per user (cycle time) from 52-63μs, improving the control duration per user for approximately 36% from the conventional system. Therefore, the proposed retransmission scheme is an sub-optimum method in terms of low complexity and low latency, as compared to CSI based retransmission. This could be potentially applied in industrial wireless system.九州工業大学博士学位論文 学位記番号:情工博甲第350号 学位授与年月日:令和2年9月25日1 Introduction|2 Overview of Low Latency and High Reliable Industrial Wireless System|3 Cross Layer Design|4 Low Latency and High Throughput PHY Design|5 High Reliable Transceiver System|6 Conclusion and Future Work九州工業大学令和2年