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manufacturing environment [2]–[7]. e research activities reported here (called the “Flexible Factory Project”) is an eort carried out under interdisciplinary cooperation be-tween industrial sectors and enterprises [8].ere are two aspects of the challenges discussed: the current status and future challenge of wireless communica-tion in factories, and the requirement specications for introducing safe and reliable wireless-controlled manufac-turing equipment.2Challenges of wireless communication technology used in the factoryrough various experiments and reviews, we have come to know that there are three major challenges to use wireless communication technology in the factory.(1) Dynamic uctuations in wireless environmentere are many metallic bodies that shield electromag-netic waves in the factory as well as frequent trac of personnel and vehicles. Such conditions in closed space can easily become a nest of a multipath environment where ephemeral (several milliseconds to several seconds) blind zones appear, disappears and move around. e manufac-turing environment is commonly associated with dynamic and unpredictable changes that make operations of a xed wireless system with a predetermined strategy dicult. Such changes include: set-up changes in processes, on and o of system power, layout changes and introduction of a new production line that takes place in short and random periods (in several hours to several days). All these changes can make the wireless environment transform into a signicantly dierent entity in several months or in several years.(2) Diversity of wireless environmentDepending on the location of the factory, the wireless environment inside a factory is subject to electromagnetic waves from outside (foreign wave) and necessitates mea-sures against it. Figure 2 shows a screen capture of a 2.4 GHz range spectrum analyzer operated in a factory located near a residential area. e measurement was a part of a frequency usage survey in the 2.4 GHz range. e horizontal axis represents the level of received signal strength and the horizontal axis represents the used chan-nel: the display color becomes redder as the time of radio wave reception becomes longer. e identication name (ESSID) of a Wi-Fi hot spot installed by a telecommunica-FiF2　Effect of residential Wi-Fi access points measured in small and medium-sized factories adjacent to residential areasFiF3　 Effect of manufacturing equipment noise measured in isolated large factories(a) 2015, July(b) 2015, DecemberTrialOperationNew sysatemFiF4　Temporal change in 920 MHz band usage2 Terrestrial Communication Technology Research and Development38　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)