Innovative use of building reinforced steel bars to transmit signals within a building

Intelligent building, smart home, and home networking are hot topics in building industry. These systems rely on a physical layer to transmit signal. Wire and wireless physical layer are commonly used. However, both layers have their limitations and associated problems especially in old building. In more than 20 year old public rental housing in HK, there is usually no spare cable containment for future cabling. Concrete chasing to install a new conduit in public corridor and tenant area is unavoidable for adding new network. In view of higher cost and great nuisance to the tenants during concrete chasing, an innovative use of building reinforced steel bars to transmit signals is introduced in this paper. The principle of signal transmission in reinforced steel bars is similar as signal coupling in a transformer. Signals are transmitted as magnetic flux by means of a transmission coil, which is installed through a reinforced steel bar. The magnetic flux flows all around the reinforced steel bars in the entire building. Another coil acting as receiver is installed in a remote area to receive the signals from the transmission coil. From the experiment, we proved that the idea is flexible. Signals can be received anywhere in the entire building with good performance.