White space symbiotic radar: A new scheme for coexistence of radio communications and radar

There is a growing realisation that, similar to the concern about abuse of the atmosphere causing Global Warming, that the Electromagnet (EM) Spectrum is rapidly filling up, with many more applications waiting for space. This has resulted, for example, in a large scale DARPA programme to share spectrum, that we discuss. So called Passive Radars that use EM emissions from other sensors opportunistically, seem to be a potential source of relief in terms of radar applications. Up until now, the Commensal version, where the sensor uses the EM emissions from sensors without impacting the other system, have been dominant, especially in the last 10 years. However, in the case of Commensal systems, there is no attempt at collaboration, and the waveforms are seldom optimal for the sensor function. In this paper we discuss a new type of passive sensor, where there is collusion between the detection function and an underlying communication system, which we term, Symbiotic. In this case, both the communications and the radar systems have a stronger case, as they are sharing the spectrum in a collaborative way. With the advent of the first cognitive radio standard, the IEEE802.22 (also known as the whitespace standard), the possibilities of using a cognitive radio network for commensal radar purpose has become bright. In this paper we propose a system level description of symbiotic EM sensor system based on White Spaces Wireless Regional Area Radio Network (WRAN). Major use of the system will be in rural and sparsely populated areas. The system can provide high speed wireless data-network of more than 10Mbps capacity to such areas. The scheme also provides capability to be used as a Radar system, which in turn can be used to detect moving objects in the area, and with signal and data processing, track them.