Interconnection of IEEE 802.15.4 islands through free space optical communication links

This article initiates a study on interconnecting Wireless Sensor Network (WSN) islands through the use of free space optical communication links. A cluster of wireless sensors, also known as motes, can be distributed in a certain location creating an IEEE 802.15.4-based wireless sensor network island that can convey information among its nodes. In many cases, multiple 802.15.4 islands exist within the same environment, such that the islands are out of motes´ radio range of communication. In such cases, it is desirable to integrate the islands in order to exchange sensor information between them. In addition, in case of remote access of data, interconnecting the islands allows users to access information remotely from any island through a single Internet gateway. This article proposes a system for integrating 802.15.4 wireless sensor network islands. For certain applications, e.g., a battlefield, security is of high importance. Thus, in addition to providing reliable high speed communication links between the islands, these links should be secure and invulnerable to eavesdropping. Free Space Optical (FSO) links can be used to achieve these goals by providing secure, reliable, high-bandwidth communication among the 802.15.4 islands. An integration system consisting of two islands is implemented and tested. Information from one of the motes in the first island is sent to the second island through an FSO link. The integration system in this article presents a novel approach accompanied by an actual implementation. It is the author´s hope that the suggested framework can be profitably employed in a wide range of WSN applications.