Cognitive Radio in Digital Agriculture: A Physical Layer Overlay Based Underground Radio Propagation System

In digital agriculture, the cognitive radio technology is being envisaged as solution to spectral shortage problems by allowing agricultural cognitive users to co-exist with PU in the same spectrum on the field. Cognitive radios increase system capacity and spectral efficiency by sensing the spectrum and adapting the transmission parameters. This design requires a robust, adaptable and flexible physical layer to support cognitive radio functionality. In this paper, two different approaches are proposed to improve the application of cognitive radios in agriculture. A novel physical layer architecture for cognitive radio based on cognition, cooperation, and cognitive interference avoidance has been developed by using power control for digital agriculture applications. The design is based on sensing of spectrum usage, detecting the message/spreading code of PU, cognitive relaying, cooperation, and cognition of channel parameters. Moreover, the power and rate allocation, ergodic, and outage capacity formulas are also presented. Furthermore, a two-hop load balancing approach is presented using a cognitive radios as a relay node in the network to improve throughput and optimize the load between different area of an agricultural field.