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using IEEE 802.11 a. e control channel occupation rate for this purpose was several percent at most.Figure 7 shows the plot of delay time observed while the broadcast data (54 bytes) was sent repeatedly for 20 minutes (transmission rate 6 Mbps, interval 10 ms) using the common channel with AGV control communication.e broadcast data was successfully sent within 5 ms on average. It is to be noted, however, that lumps of longer than average delays appeared in a cyclic fashion. Analysis of the data revealed that the long delays are synchronized with the signal transmission to control the two AGVs. e occurrence of the delay can be ascribed to the fact that the system sends the start control packet multiple times. is strategy is adopted to make the system more robust against accidental stoppage of AGV, which may cause entire halt of the line. If the number of AGVs increases that share a common frequency band, communication may be dis-rupted even if the frequency band still has plenty of space as a whole. e same is true for the introduction of a new system adjacent to the existing ones, if it shares the same frequency band.③ -2 Application Specic Optimization StageIn this stage, wireless communication is introduced mainly for such purposes as: transition of manual data gathering into an automated system, utilization of hitherto untapped information for new perspectives, improvement of process control and preventive maintenance. is stage generally requires technologies for long-term, large-scale data gathering and analysis. Momentum is gathering for the use of the 920 MHz range (e.g. Wi-SUN [10]) in the factory in line with the accelerated development of small and low-cost sensor devices. However, careful validation in advance is needed before introducing these applications because they may share the same frequency band with existing systems. Shared use of common frequencies may hinder proper operation of existing production systems, and the newly introduced system itself may suer interfer-ence from the other systems, resulting in failure to make the most of its capability.4Reliable implementation of wireless communication system in the factoryWhen a new wireless communication system is intro-duced into a factory, users regard the following four aspects of the system as important. First, they generally do not favor the system if the internal mechanism is incompre-hensible to them, and if it attempts full automation. A part of the reasons for this attitude can be ascribed to the fact that the users are themselves engineers: it is important for them to understand how the system works and locate and identify problems if it steps out of normal operation, at least the system conguration should be transparent enough for them to easily guess what is going on. Second, the system should allow gradual updates rather than com-plete replacement of the systems in the factory because heavy investment in factories and equipment directly af-fects product prices. Introduction of a new technology can generally progress only very slowly if it needs total system revamping in the factory. ird, guarantee of continued factory operation is essential. is involves transparency of system internals for the on-site engineers to understand what is going on, and what will take place next, enabling them to recover the system quickly at the time of produc-tion line failure.In view of these considerations, construction of a platform is needed that allows the user to select and t together the functions in need. e platform should also facilitate partial addition/modication of the existing sys-tem. Above all, in the factory, the establishment of an in-formation sharing system is needed to allow the engineers on site to correctly grasp the current situation and assist their decision to update the system without sacricing continued performance of the production line. NICT has proposed a framework to be implemented in the factory, Smart Resource Flow (SRF), to streamline the ow of all resources (material, power, manufacturing machinery, radio waves, and human resources), and is conducting research and development of a wireless communication-oriented variant, the SRF wireless platform, to make full FiF8Wireless platform protocol stack in the proposed Smart Resource Flow (SRF) scheme412-6 Toward Smart Factory using Wireless Communication Technologies