Kajima Corporation (President: Yoshikazu Oshimi) and Fujikura Ltd. (President & CEO: Yoichi Nagahama) have jointly started making use of vertical installation of wireless broadband leaky coaxial cables (WBLCXs) technology. The patent pending method enabled cost reduction for introducing and maintaining local access network environment within buildings. By laying WBLCXs in vertically penetrating holes such as pipe shafts during the constructing phase of buildings, the number of wireless access points (APs) is drastically decreased, although the placement needs to be well-planned. As a result, both the initial and maintenance costs are reduced.
This innovative technology was applied in the private residential home (Owner: Social welfare service corporation Soseikai, Completed in February, 2015) in Izumi Osawa senior town (Izumi-ku, Sendai City) for the first time. It will also be adopted by Kajima Tokyo Architectural Construction branch and Kajima Tokyo Civil Engineering branch building (Completed in August, 2016), which is currently under construction.
[Background of development]
Wi-Fi (Wireless LAN) has been widely used recently, and wireless local access network environments are increasingly being introduced in newly constructed buildings. In many cases, reinforced concrete or metal deck plates are used for floor slabs, and it is difficult to transmit electric waves through floors. Consequently, many APs should be installed in each floor to create a wireless local access network environment in the whole building, and there is a problem not only in terms of construction cost but also electricity, maintenance and renewal fees.
[Strength of the technology]
Wireless broadband leaky coaxial cables are external antennas placed in wireless local access network environment access points. They not only transmit electric signals but also spread out parts of electric waves from their slots, and have been used as antennas in dead zones in tunnels in the Tokaido Shinkansen line since around 1965. Recently, they have been installed horizontally in ceilings of hotels and other buildings as measures against dead zones that are shades of obstacles such as walls made from reinforced- concrete.
[Structure of wireless broadband leaky coaxial cables]
[Measure to dead zone]
This technology allows a drastic reduction in the number of APs by installing WBLCXs vertically in penetrating holes of floor slabs and by minimizing the difference in electric waves on each floor by laying them above floor and below one alternately. Antennas have characteristics which make the reach of electric waves shorter like shapes of umbrellas according to the distance from the APs.
[Applied case: Izumi Osawa senior town]
This technology was applied in the building of a private residential home in Izumi Osawa senior town in Izumi-ku, Sendai City for the first time. As part of resident monitoring system to check the entrances and exits from any location, a wireless local access network environment was planned. 27 APs were planned to be installed initially, but the number has been reduced to 3 thanks to this technology. In principle, the APs were laid out above and below alternatively, but electric waves to the east and below floors are strengthened, as they are used more than other areas.
As a result, the initial cost of buying equipment, the construction costs and others have been reduced by approximately 50%, maintenance costs by approximately 90%. APs usually need to be renewed every 5 years, thus the life cycle costs for 20 years including the renewal costs are estimated to be reduced by 70 % and above.
[Our future policy]
Needs to construct wireless local access network environment in buildings are expected to be increasing more than ever. It is our policy to promote this technology that enables the reduction of initial and maintenance costs in the future.