دانلود رایگان مقاله سنجش طیف تعاونی زمانی کارآمد از طریق محاسبات آنالوگ بر کانال دسترسی

Abstract

Conventional cooperative spectrum sensing (CSS) schemes in cognitive radio networks (CRNs) require that the secondary users (SUs) report their sensing data separately in the time domain to the fusion center, which yields long reporting delay especially in the case of large number of cooperative SUs. By exploiting the computation over multiple-access channel (CoMAC) method, this paper proposes a novel CoMACbased CSS scheme that allows the cooperative SUs to encode their local statistics in transmit power and to transmit simultaneously the modulated symbols sequence carrying transmit power information to the fusion center. The fusion center then makes the final decision on the presence of primary users by recovering the overall test statistic of energy detection from the energy of the received signal. Performance metrics of the CoMAC-based CSS scheme, i.e., detection probability and false alarm probability, are further derived based on the central limit theorem. Finally, based on the derived detection and false alarm probabilities, both energy detection threshold and spectrum sensing time are optimized to improve the average throughput of the CRN. Simulations demonstrate the efficiency of this work.

8. Conclusion

A novel CoMAC-based CSS scheme for CRNs has been proposed in [1]. Unlike conventional CSS schemes, the proposed CoMACbased CSS scheme takes advantage of the CoMAC to accelerate the CSS process via merging the reporting and the computation steps of CSS, which noticeably reduces the reporting delay in conventional CSS schemes. Based on the estimation of the desired arithmetic mean function of local statistics, we analyze the detection probability and the false alarm probability of the proposed CoMAC-based CSS scheme. Finally, we obtain the optimal energy detection threshold and spectrum sensing time yielding the maximal average throughput of the CRN. Extensive simulations have demonstrated that, using much less reporting time, the CoMAC-based CSS scheme yields almost the same sensing performance as conventional CSS schemes, provided that the symbol sequence length L is sufficiently large. In addition, for a suitably chosen L, the average throughput of the CoMACbased CSS scheme is shown much higher than that of conventional CSS schemes, especially when the number of cooperative SUs is large. The disadvantage of the proposed CoMAC-based CSS scheme lies in the high energy consumption when the length of the symbol sequence is large. In order to address the issue of high energy consumption, we have to formulate a completely novel optimization problem instead of problem (33) and to redesign a corresponding solution method to it as well. We will leave this interesting direction as a future work.