Joint Beamforming and Power Control Algorithm for Cognitive Radio Network with the Multi-Antenna Base Station
ABSTRACT Cognitive radio (CR) has been studied as a useful solution for efficient utilization of scarce radio spectrums. For it to succeed, two conflicting challenges are imposed on the secondary users: one is to ensure the quality of service (QoS) of the primary link, and the other is to maximize their own transmit throughput. To balance this tradeoff, beamforming and power control employing the multi-antenna in the base station (BS) of the CR network have been introduced. In the perfect beamforming situation, the power control algorithms suitable in the CR network with a multi-antenna BS (MBS) have been proposed in previous works. However, those algorithms are meaningless for realizing a practical CR network with the MBS since perfect beamforming is impossible. Therefore, unlike previous works, this paper proposes a joint beamforming and power control algorithm as a more practical strategy for realizing a CR network with the MBS. The algorithm is proposed so as to maximize the sum-rate of secondary users, while not degrading QoS for the primary link. Numerical results verify its effectiveness in a CR network with the MBS.
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ABSTRACT: Traditionally, interference protection is guaranteed through a policy of spectrum licensing, whereby wireless systems get exclusive access to spectrum. This is an effective way to prevent interference, but it leads to highly inefficient use of spectrum. Cognitive radio along with software radio, spectrum sensors, mesh networks, and other emerging technologies can facilitate new forms of spectrum sharing that greatly improve spectral efficiency and alleviate scarcity, if policies are in place that support these forms of sharing. On the other hand, new technology that is inconsistent with spectrum policy will have little impact. This paper discusses policies that can enable or facilitate use of many spectrum-sharing arrangements, where the arrangements are categorized as being based on coexistence or cooperation and as sharing among equals or primary-secondary sharing . A shared spectrum band may be managed directly by the regulator, or this responsibility may be delegated in large part to a license-holder. The type of sharing arrangement and the entity that manages it have a great impact on which technical approaches are viable and effective. The most efficient and cost-effective form of spectrum sharing will depend on the type of systems involved, where systems under current consideration are as diverse as television broadcasters, cellular carriers, public safety systems, point-to-point links, and personal and local-area networks. In addition, while cognitive radio offers policy-makers the opportunity to improve spectral efficiency, cognitive radio also provides new challenges for policy enforcement. A responsible regulator will not allow a device into the marketplace that might harm other systems. Thus, designers must seek innovative ways to assure regulators that new devices will comply with policy requirements and will not cause harmful interference.Proceedings of the IEEE 05/2009; · 6.91 Impact Factor
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ABSTRACT: This article presents a high-level overview of the IEEE 802.22 standard for cognitive wireless regional area networks (WRANs) that is under development in the IEEE 802 LAN/MAN Standards Committee.IEEE Communications Magazine 02/2009; · 3.66 Impact Factor
Conference Proceeding: Exploiting Hidden Power-Feedback Loops for Cognitive Radio[show abstract] [hide abstract]
ABSTRACT: Prior study on the cognitive radio (CR) has mostly adopted the passive sensing protocol, where the CR keeps monitoring the spectrum of interest, and decides to transmit when the sensing result indicates that the primary radio (PR) is inactive. In this paper, we propose an alternative active sensing protocol where, prior to the sensing, the CR generates a temporary jamming signal to deliberately interfere with the PR. The jamming signal is aimed to trigger an interesting interaction between the CR and PR, named as the hidden power-feedback loop: If the PR is indeed active and reacts upon receiving the jamming signal by increasing its transmit power, the CR will receive a power-boosted PR signal that is more easily detectable. Moreover, this paper demonstrates the usefulness of exploiting the power-feedback loop for the CR to effectively estimate the channel from the CR to the PR. This is well-known as a crucial task to implement for the CR operating under the so-called interference temperature constraint, where the CR is allowed to transmit regardless of the PR's on/off status, provided that the resultant interference power level at the PR is kept below some predefined threshold.New Frontiers in Dynamic Spectrum Access Networks, 2008. DySPAN 2008. 3rd IEEE Symposium on; 11/2008