HTML5 Webook

32/182

devices in the multi-hop communication pathway as con-trol support devices. As the control target devices and the control support terminals handle the data transmission for the control action, the devices adjust the sleep period above and operate so that the delay time falls within an acceptable range. Figure 5 shows clear operating examples where both the control target device and the control support devices do not apply the sleep period.For the evaluation test to conrm the action of the proposed low-latency communications, Fig. 6 shows an overview and Table 1 presents the results, respectively. Table 1 consolidates the characteristics related to the delay time on the data transmission from CS for D4 and D5 in Fig. 6 (b). In Figure 6 (b). Although each device uses the multi-hop communication topology where the beacon in-terval is 10 seconds, it is assumed that D5 and D2 are set to the control target device and the control support device, respectively, and that they operate without introducing the sleep period. As a result, as per Table 1, if not implement-ing low-latency action, the delay occurs due to the beacon interval, but it has been found that low-latency action eliminates the eect.3Development and implementation of low-energy radio3.1Overview of low-energy radio moduleFigure 7 shows the developed low-energy radio module. In addition, Table 2 shows the specications for this mod-ule. is module is successfully implemented in the mini-mum composition on the circuit board (4 cm × 2 cm) of the integrated circuit for the physical layer, MAC layer and MCU (Micro Controller Unit: embedded microprocessor) for control, including additional functions such as FEC (Forward Error Correction) aer assuming various utility FiF6　Overview of evaluation test for low-latency communicationsFiF7　Appearance of low-energy radio module(a) Configuration(b) Overview of topology and data transmissionTabT1 Evaluation results of low-latency communicationsControl signal destinationAverage latencyVariance of latencyD5 (with low-latency action)0.0 s0.0 s2D4 (without low-latency action)15.15 s16.87 s2TabT2 Specifications of low-energy radio moduleSize20 mm × 40 mm × 3 mmWeight4 gFrequency band920.6-928.0 MHzTransmission power20 mWModulation scheme2 GFSKData rate50, 100, 200 kb/sConsumption currentActive state: 50 mASleep state: 30 μAI/O interfaceSerial2 Terrestrial Communication Technology Research and Development28　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)