Incumbent Spectrum Users Research Articles

Vehicular Networking in the TV White Space Band: Challenges, Opportunities, and a Media Access Control Layer of Access Issues

With the increase of wireless data traffic demand, supplementing dedicated short-range communications (DSRC) with additional spectral opportunities becomes very important. In many countries, due to the switchover from analog to digital television, a significant portion of the television (TV) band has been released for opportunistic cognitive access. Therefore, one possible solution to the spectrum scarcity problem in the DSRC band is to offload a portion of data traffic to the TV white space (TVWS) band. However, expansion of vehicular networks to the TVWS by means of cognitive radio technologies causes novel challenges such as random channel availability, strict protection of incumbent spectrum users, and dealing with interference among heterogeneous cognitive networks. In this article, we outline the challenges and opportunities involving TVWS access for vehicular networks, with an emphasis on media access control (MAC) layer issues. Numerical results of the DSRC system augmented with a TVWS cognitive module are also presented.

Spectrum sharing using licensed shared access: the concept and its workflow for LTE-advanced networks

Spectrum sharing between an existing incumbent spectrum user and an LTE/LTEAdvanced network with conditions that resemble exclusive licensing have become an appealing solution for mobile network operators to respond to the growing traffic and spectrum demand in a timely manner. While traditional exclusive licensing continues to be the preferred option for MNOs, the new sharing- based licensed shared access (LSA) concept is receiving growing interest in research, regulation and standardization. When applied to mobile communications, the LSA concept would allow an MNO to share spectrum from another type of incumbent spectrum user under a regulator?s supervision with predetermined rules and conditions that guarantee operational certainty for both MNO and incumbent. This article reviews different types of spectrum bands for LTE/LTE-Advanced and beyond networks, and focuses on the LSA concept as a spectrally efficient solution for spectrum access in the future. The article identifies the key stakeholders, including the incumbent spectrum user, the MNO, and the regulator, and their roles in the LSA concept. The key elements in the LSA concept are reviewed, and a work flow for the life cycle of the LSA concept is proposed, consisting of LSA preparation, licensing, deployment, and release phases. The tasks of the key stakeholders in the different phases of the LSA work flow are discussed. The LSA concept can offer a complementary approach to traditional exclusive licensing and license-exempt operations with features that benefit all involved stakeholders. It can be realized with reasonable modifications to the existing network infrastructure and regulatory framework with two new elements for managing the varying spectrum availability: the LSA Repository and LSA Controller.

Enforcement and Spectrum Sharing: Case Studies of Federal-Commercial Sharing

To promote economic growth and unleash the potential of wireless broadband, there is a need to introduce more spectrally efficient technologies and spectrum management regimes. That led to an environment where commercial wireless broadband need to share spectrum with the federal and non-federal operations. Implementing sharing regimes on a non-opportunistic basis means that sharing agreements must be implemented. To have meaning, those agreements must be enforceable. With the significant exception of license-free wireless systems, commercial wireless services are based on exclusive use. With the policy change facilitating spectrum sharing, it becomes necessary to consider how sharing might take place in practice. Beyond the technical aspects of sharing, that must be resolved lie questions about how usage rights are appropriately determined and enforced. This paper is reasoning about enforcement in a particular spectrum bands (1695-1710 MHz and 3.5 GHz) that are currently being proposed for sharing between commercial services and incumbent spectrum users in the US. We examine three enforcement approaches, exclusion zones, protection zones and pure ex post and consider their implications in terms of cost elements, opportunity cost, and their adaptability.

Low complexity distributed spectrum access algorithm for cognitive radio

The selection of optimum frequency channels by cognitive radio devices is considered challenging, particularly when such devices have to mutually co-exist and also take account of existing users of the spectrum. In addition to the problem of accurate spectrum sensing, there are additional considerations that result because of the dynamic capabilities of the terminals. Particular problems include that of allowing terminals to discover each other when they may be tuned to different frequencies, operating without a common control channel. This work has developed a spectrum access algorithm by which cognitive radio terminals monitor the available spectrum, discover each others’ presence and collaborate to select the optimum communications channel. This is achieved while avoiding interference to incumbent users. In contrast to previous work in this area, the proposed algorithm is of low complexity, requiring the terminals neither to dedicate part of their operational time to spectrum sensing, nor to periodically switch to a control channel. It is thus suitable for implementation in simple terminals. A simulation tool, which models the interaction and behaviour of the terminals, has been produced and used to test the performance of the algorithm in a demanding environment. It was shown that the algorithm permits a high level of data throughput, with protection for incumbent spectrum users.

A study of secondary spectrum use using agent-based computational economics

Wireless communication relies on access to the radiocommunications spectrum. A series of high-priced spectrum auctions has indicated that there is a scarcity or an inefficient use of spectrum resources. This paper presents an Agent-based Computational Economics (ACE) model designed to study the secondary use spectrum market, which improves spectrum usage by allowing incumbent spectrum users to lease unused portions of their assigned spectrum to third parties who could put them to a better use. In this paper, we are particularly interested in the conditions under which such a market is likely to emerge.