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Optimal power allocation for cognitive relay networks: amplify-and-forward versus selection relay

Science china(Information Sciences) 2011年第4期54卷 861-872页

作者： yue wenjing 1,2,zheng baoyu 1,2,meng qingmin 1,yue wenjie 3 & cui jingwu 1 1 institute of signal processing and transmission,nanjing university of posts and telecommunications,nanjing 210003,china 2 Department of Electronic Engineering,Shanghai Jiaotong university,Shanghai 200240,china 3 Shanxi institute of Educational Science,Taiyuan 030009,china 1. institute of signal processing and transmission Nanjing University of Posts and Telecommunications Nanjing 210003 China2. Department of Electronic Engineering Shanghai Jiaotong University Shanghai 200240 China3. Shanxi Institute of Educational Science Taiyuan 030009 China

We consider a cognitive relay network which is defined by a source,a destination,and cognitive relay nodes and primary user *** this network,a source is assisted by cognitive relay nodes which allow coexisting with primary user nodes by imposing severe constraints on the transmission power so that they operate below the noise floor of primary user *** this paper,we mainly study the power allocation strategies of this system to minimize the outage probability subject to total and individual power constraints for cognitive relay nodes and subject to interference constraints for primary user nodes.A relay transmission scheme,namely amplify-and-forward (AF),is *** first present an optimal power allocation (OPA) scheme to minimize the system outage probability,based on instantaneous channel state information among the source,destination and relay nodes and mean channel gains between primary user nodes and cognitive ***,we propose a selection AF scheme (S-AF) where the single best relay is chosen to assist in the transmission and study power allocation strategy for S-AF to minimize outage *** analytical power allocation strategies have been validated through numerical *** results indicate that the AF with OPA and S-AF with OPA have significantly better outage behavior and average throughput than AF and S-AF schemes *** also find that S-AF with OPA achieves a higher throughput,and hence lower outage probability than AF with OPA.

关键词： cognitive radio (CR) relay networks power allocation outage probability

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Robust cooperative spectrum sensing schemes for fading channels in cognitive radio networks

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Science china(Information Sciences) 2011年第2期54卷 348-359页

作者： yue wenjing1,2, zheng baoyu1,2, meng qingmin1, cui jingwu1 & XIE PeiZhong1 1institute of signal processing and transmission, nanjing university of posts and telecommunications, nanjing 210003, china 2Department of Electronic Engineering, Shanghai Jiaotong university, Shanghai 200240, china 1. institute of signal processing and transmission Nanjing University of Posts and Telecommunications Nanjing 210003 China2. Department of Electronic Engineering Shanghai Jiaotong University Shanghai 200240 China

In cognitive radio systems, cooperative spectrum sensing can detect the presence of the primary user accurately. In practice, however, since the sensing observations are forwarded to a data collector through fading channels, the sensing performance is severely degraded. To deal with this problem, in this paper, we first propose a secondary user selection based cooperative spectrum sensing method to improve sensing performance by decreasing the reporting errors introduced by the fading channels. More specifically, only the secondary users with better signal-to-noise ratio (SNR) for reporting channels are allowed to send their local binary decisions (0 or 1) to the data collector while the others will send nothing. Additionally, we further propose a diversity based cooperative spectrum sensing method which applies existing space-time coding. By exploiting space diversity in CR network, the reporting errors introduced by the fading channel can be decreased and then the sensing performance is improved significantly. For either proposed cooperative spectrum sensing method, the sensing performance is derived and the analytical performance results are given. Our analysis and numerical results verify that proposed methods outperform the conventional cooperative spectrum sensing with OR-rule by taking into account the error effect on the reporting channels.

关键词： cognitive radio (CR) spectrum sensing energy detection diversity technique space-time coding

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