Short length CDMA codes for wireless sensor networks

Wireless sensor networks consist of a large number sensors spread across a given geographical area. Each sensor has its own communication capability as well as certain level of intelligence for signal processing and networking. As the sensor nodes are densely populated, communication range requirement for these nodes is smaller. After signal detection, a number of sensor nodes communicate over the same wireless multiuser channel. This necessitates the use of orthogonal codes with good cross correlation properties to mitigate multi access interference (MAI). In sensor networks, due to the dense placement of nodes, limited availability of power brings different metrics for optimality where short length spreading codes might be utilized for coding purposes. In this paper, a design methodology for the generation of such short length varying power orthogonal code sets with multiple levels of chip values is presented. BER characteristics of these short length codes are presented for two user and multiuser scenarios in AWG noise environment. As dynamic utilization of spreading code libraries consisting of multiple orthogonal sets brings additional network security at the code level, we expect spreading code rich system solutions in the future.