Abstract

Evolving communication systems rely on using increasingly higher frequencies for larger channel bandwidths. The increased channel capacities enabled by higher carrier frequencies provide high speed communication for commercial and active users, however, these benefits do not extend to passive users, such as radio astronomy. The focus of the proposed effort is to create a framework for spectrum coexistence that is beneficial for both active and passive users. Instead of simply switching to higher and undeveloped frequencies – which passive users cannot – the proposed research uses high frequency, optical signal carriers for interference separation, enabling the coexistence of active and passive users at the same time and in the same physical location. The proposed coexistence solution will enable continuous availability of wideband spectrum for passive users, an important requirement for detecting unknown signals, since the bandwidth and the time window for unknown astronomical, atmospheric and geospace signals cannot be manipulated. The proposal involves collaboration between one private and two state universities in New Jersey, and will support education at various levels: for pre-college students, the PIs will develop games and instructive presentations that integrate the explanation of science fundamentals. Undergraduate students will access the evolution of communication technologies through Rowan University’s 8-semester research-based Engineering Clinic program. Commercial applications will be explored through industrial partners within local area of the PI campuses.

Since there is a projected increase in interference at both high and low RF frequencies, which will impair the success of both commercial and scientific use of spectrum, it is necessary to develop technologies that will mitigate the interference observed by all users of the radio spectrum, ultimately allowing better coexistence between the wide range of applications dependent on radio spectrum. The proposed system is implemented by redesigning the hardware and exploring communication protocols at multiple layers. In the physical layer, the photonic system separates a mixed received signal in the congested radio spectrum by upconverting the signal carriers to optical frequencies, providing over 100GHz of bandwidth in a single channel. In the network level, communication protocols are redesigned to enable passive users to continuously access to wideband spectrum and coexist with active users. The network layer protocol will optimize the deployment of the hardware system to minimize the cost of new infrastructures, better share spectrum, and improve communication throughput. The intellectual merit stems from the completely orthogonal approach proposed to address the challenges of radio spectrum, and the seamless integration of hardware innovation with communication protocols. By harnessing the unique properties of optical carriers, the photonic system processes analog signals before digitization, which eliminates both the current bandwidth limit and the resolution limit. The hardware innovation creates unprecedented resources for communication applications. The photonic system functions as a platform that provides new resources for both the existing and emerging spectrum sharing methods, specifically, dynamic spectrum allocation, interference alignment, etc. With a multi-layer design, the proposed system will advance the understanding of spectrum usage by enabling conexistence of systems with diverse power levels and large bandwidths.