A Cooperationbased Scheme for Secondary Users to Enhance the Utilization of TV Spectra Space shadowed by obstacles, e.g., buildings and indoor structures, is traditionally considered as occupied and is unable to provide any useful incumbent services due to poor incumbent signaling. The timefrequency slots in this case are ignored for a long time and can be further used if an agile coexisting scheme is applied by secondary users (SUs). In this paper, we propose a new scheme for SUs to reuse these spatial opportunities in an incumbent digital TV (DTV) environment. These spatial opportunities can be used either by the SUs for private applications or by TV viewers (TVVs) provided that TV programs are suitably relayed. We analyze the applicability of the proposed scheme, which paves a way for enhancing the spectral efficiency in the spatial domain.

Increasing Spectrum Sharing Opportunities by Radio Link Design in an Urban Environment Modern mobile communication systems like 5G require more frequency bands to achieve such user needs as higher data rate, low latency, and massive device connectivity. This paper describes our dynamic spectrumsharing scheme to obtain more bandwidth. Our scheme collects the frequency band usage information at each location and time, and determines such appropriate spectrumsharing conditions, as available spectrum band and transmission power based on the spectrum usage. If interference between the primary and secondary users occurs during spectrum sharing, the sharing condition is changed. This paper also proposes a detection method for primary user communication areas to increase the opportunity for spectrumsharing and improve the ordinally Interference Temperature Model. We conclude that spectrumsharing can be achieved in an urban radio propagation environment through a computer simulation.