Cooperative Sensing among Cognitive Radios
Cooperative Sensing among Cognitive Radios
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DOI：
10.1109/icc.2006.254957
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发表时间：
2006-12
期刊：
影响因子：
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通讯作者：
S. M. Mishra;A. Sahai;R. Brodersen
中科院分区：
文献类型：
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作者：
S. M. Mishra;A. Sahai;R. Brodersen
认知无线电作为一种机会主义地使用未充分利用的频谱的技术已经得到了发展，因为它们能够在没有检测到主用户的情况下感知频谱并使用频带。然而，所需的灵敏度是非常苛刻的，因为任何单个无线电都可能面临深度衰落。我们建议在基于硬决策的传感领域进行轻量级合作，以降低对单个无线电的灵敏度要求。我们证明了系统设计者必须为衰落保留的“链路预算”是所需的检测概率的重要函数。即使是几个面临独立衰落的合作用户(~10-20)，也足以通过大幅降低个人检测要求来达到实用的阈值水平。在实现这些收益方面，硬决策的表现几乎与软决策一样好。在阴影相关的环境中的合作收益受到合作足迹(用户合作的区域)的限制。从本质上讲，少数独立用户比许多相关用户更健壮。不幸的是，合作收益对对抗性/失败的认知无线电非常敏感。以已知方式失败的无线电(始终报告主用户的存在/不存在)可以通过审查它们来补偿。另一方面，以未建模的方式失败或可能是恶意的无线电，引入了可实现的灵敏度降低的界限。根据经验，如果我们相信1/N个用户可能会以未知的方式失败，那么合作收益将被限制在N个受信任用户的情况下。
Cognitive Radios have been advanced as a technology for the opportunistic use of under-utilized spectrum since they are able to sense the spectrum and use frequency bands if no Primary user is detected. However, the required sensitivity is very demanding since any individual radio might face a deep fade. We propose light-weight cooperation in sensing based on hard decisions to mitigate the sensitivity requirements on individual radios. We show that the "link budget" that system designers have to reserve for fading is a significant function of the required probability of detection. Even a few cooperating users (~10-20) facing independent fades are enough to achieve practical threshold levels by drastically reducing individual detection requirements. Hard decisions perform almost as well as soft decisions in achieving these gains. Cooperative gains in a environment where shadowing is correlated, is limited by the cooperation footprint (area in which users cooperate). In essence, a few independent users are more robust than many correlated users. Unfortunately, cooperative gain is very sensitive to adversarial/failing Cognitive Radios. Radios that fail in a known way (always report the presence/absence of a Primary user) can be compensated for by censoring them. On the other hand, radios that fail in unmodeled ways or may be malicious, introduce a bound on achievable sensitivity reductions. As a rule of thumb, if we believe that 1/N users can fail in an unknown way, then the cooperation gains are limited to what is possible with N trusted users.