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Radio propagation models play a crucial role in realizing effective spectrum sharing. Unlike propagation models that do not use the exact details of terrain, terrain-based propagation models are effective in identifying spatial spectrum sharing opportunities for the secondary users (SUs) around an incumbent user (IU). Unfortunately, terrain-based propagation models, such as the Irregular Terrain Model...
Although using geolocation databases for spectrum sharing has many pragmatic advantages, it also raises potentially serious operational security (OPSEC) issues. OPSEC is especially a paramount consideration in the light of recent calls in the U.S. for spectrum sharing between federal government (including military) systems and non- government systems (e.g., cellular service providers). In this paper,...
We are in the midst of a major paradigm shift in how we manage radio spectrum. This paradigm shift is necessitated by the growth of wireless services of all types and the demand pressure imposed on limited spectrum resources under legacy management regimes. The shift is feasible because of advances in radio and networking technologies that make it possible to share spectrum dynamically in all possible...
The legacy concept of exclusion zones (EZs) is inept at enabling efficient utilization of fallow spectrum by secondary users (SUs), since legacy EZs are static and overly-conservative. The notion of a static EZ implies that it has to protect incumbent users (IUs) from the union of likely interference scenarios, leading to a worst-case, conservative solution. In this paper, we propose the concept of...
Cooperative transmit beamforming (CTB) is a practical approach for addressing the challenging problem of spectrum scarcity in broadband 5G wireless communication systems. It is a technique that allows a group of secondary users (SUs), each equipped with a single omni-directional antenna, to collaborate and steer the signal towards the intended receiver. CTB allows SUs to co-exist with primary users...
Transmit beamforming is one of the promising ways of accessing spectrum in an underlay cognitive radio network (CRN). In this paper, a robust cooperative transmit beamforming scheme is proposed for a mobile (or stationary) secondary receiver in a CRN where steering vector available at the distributed transmitters is error prone. The solution to the beamforming problem is based on stochastic optimization...
In spectrum sharing, a spatial separation region is defined around primary users (PUs) to protect them from secondary user (SU)-induced interference. This protection region — referred to by a number of names, such as an exclusion zone (EZ) or a protection zone (PZ) — has a static boundary, and this boundary is determined very conservatively to provide an additional margin of protection for the PUs...
Reducing the size of exclusion zones (EZs) in spectrum sharing is vital for efficient utilization of fallow spectrum as well as for the economic viability of spectrum sharing itself. In this paper, we explore two approaches for reducing the size of EZs. We show that multi-tiered EZs can be used to improve spectrum utilization efficiency by implementing the concept of differential spectrum access hierarchy...
Although using geolocation databases is a practical approach for enabling spectrum sharing, it poses a potentially serious privacy problem. Secondary users (queriers), through seemingly innocuous queries to the database, can determine the types and locations of incumbent systems operating in a given region of interest, and thus compromise the incumbents' operational privacy. When the incumbent systems...
A robust transmit beamforming scheme is proposed for green cognitive radio networks in presence of incorrect steering vector estimations. The beamformer is designed using a stochastic optimization approach. The proposed beamforming scheme achieves three objectives: a) Probability for large-than-a-threshold for secondary user's received power in the steering direction is maximized; b) Probabilities...
This paper proposes a robust beamforming scheme under steering vector uncertainty for cognitive radio based vehicular communication. The service probability of secondary users (SU) is maximized, the SU's transmission power is uniform within the target mobility range, and the probability of interference level to primary users (PU) is constrained. Simulation results show significant BER improvement...
Cognitive Radio (CR) is a promising intelligent technology to increase the spectral efficiency by permitting Primary Users (PU) and Secondary Users (SU) to share the radio spectrum. This paper proposes an optimum transmit beamforming scheme that allows multiple SU, stationary and/or moving, to co-exist with a stationary PU. With knowledge of channel information only between the secondary transmitter...
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