Báo cáo hóa học: Research Article Distributed Cooperation among Cognitive Radios with Complete and Incomplete Information

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Distributed Cooperation among Cognitive Radios with Complete and Incomplete Information
Nội dung trích xuất từ tài liệu:
Báo cáo hóa học: " Research Article Distributed Cooperation among Cognitive Radios with Complete and Incomplete Information"Hindawi Publishing CorporationEURASIP Journal on Advances in Signal ProcessingVolume 2009, Article ID 905185, 13 pagesdoi:10.1155/2009/905185Research ArticleDistributed Cooperation among Cognitive Radios withComplete and Incomplete Information Lorenza Giupponi and Christian Ibars Centre Tecnologic de Telecomunicacions de Catalunya (CTTC), Av. del Canal Olimpic, s/n, 08860 Castelldefels, Spain Correspondence should be addressed to Lorenza Giupponi, lorenza.giupponi@cttc.es Received 30 January 2009; Accepted 20 May 2009 Recommended by John Chapin This paper proposes that secondary unlicensed users are allowed to opportunistically use the radio spectrum allocated to the primary licensed users, as long as they agree on facilitating the primary user communications by cooperating with them. The proposal is characterized by feasibility since the half-duplex option is considered, and incomplete knowledge of channel state information can be assumed. In particular, we consider two situations, where the users in the scenario have complete or incomplete knowledge of the surrounding environment. In the first case, we make the hypothesis of the existence of a Common Control Channel (CCC) where users share this information. In the second case, the hypothesis of the CCC is avoided, which improves the robustness and feasibility of the cognitive radio network. To model these schemes we make use of theory of exact and Bayesian potential games. We analyze the convergence properties of the proposed games, and we evaluate the outputs in terms of quality of service perceived by both primary and secondary users, showing that cooperation for cognitive radios is a promising framework and that the lack of complete information in the decision process only slightly reduces system performance. Copyright © 2009 L. Giupponi and C. Ibars. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.1. Introduction that they have knowledge of the interference caused by its transmitter to the receivers of the primary users (PUs). Specifically, the underlay paradigm mandates that concur-Cognitive Radio is a new paradigm in wireless communica- rent primary and secondary transmissions may occur as longtions to enhance utilization of limited spectrum resources. It as the aggregated interference generated by the SUs is belowis defined as a radio able to utilize available side information,in a decentralized fashion, in order to efficiently use the radio some acceptable threshold. The overlay paradigm allows the coexistence of simultaneous primary and secondaryspectrum left unused by licensed systems. The basic idea is communications in the same frequency channel as long asthat a secondary user (a cognitive unlicensed user) is able the SUs somehow aid the PUs, for example, by means ofto properly sense the spectrum conditions, and, to increaseefficiency in spectrum utilization, it seeks to underlay, advanced coding or cooperative techniques. In particular, in a cooperative scenario the SUs may decide to assign part ofoverlay, or interweave its signals with those of the primary their power to their own secondary communications and the(licensed) users, without impacting their transmission [1]. remaining power to relay the PUs transmission [2].The interweave paradigm was the original motivation for While the most important challenge of the interweavecognitive radio and is based on the idea of opportunistic paradigm is that of spectrum sensing, in order to realizecommunications. In fact, numerous measurement cam- a reliable detection of the PUs, the significant challengepaigns have demonstrated the existence of temporary space- to face in the underlay paradigm is that of estimating thetime frequency voids, referred to as spectrum holes, which aggregated interference at the PUs receivers that is beingare not in constant use in both licensed and unlicensed bands caused by the opportunistic activity of multiple SUs. Inand which can be exploited by secondary users (SUs) for literature, the analysis of the underlay paradigm for cognitivetheir communications. The underlay paradigm encompasses ...