No abstract

Spectrum sensing plays an essential role in the detection of unused spectrum whole in cognitive radio networks, including cooperative spectrum sensing (CSS) and independent spectrum sensing. In cognitive radio ad hoc networks (CRAHNs), CSS enhances the sensing performance of cognitive nodes by exploring the spectrum partial homogeneity and fully utilizing the knowledge of neighboring nodes, e.g., sensing results and topological information. However, CSS may also open a door for malicious nodes, i.e., spectrum sensing data falsification (SSDF) attackers, which report fake sensing results to deteriorate the performance of CSS. Generally, the performance of CSS has an inverse relationship with the fraction of SSDF attackers. On the contrary, independent spectrum sensing is robust to SSDF attacks. Therefore, it is desirable to choose a proper sensing strategy between independent sensing and collaborative sensing for CRAHNs coexisting with various fractions of SSDF attackers. In this paper, a novel algorithm called Spectrum Sensing Strategy Selection (4S) is proposed to select better sensing strategies either in a collaborative or in an independent manner. To derive the maximum a posteriori estimation of nodes’ spectrum status, we investigated the graph cut-based CSS method, through which the topological information cost function and the sensing results cost function were constructed. Moreover, the reputation value was applied to evaluate the performance of CSS and independent sensing. The reputation threshold was theoretically analyzed to minimize the probability of choosing the sensing manner with worse performance. Simulations were carried out to verify the viability and the efficiency of the proposed algorithm.

In order to suppress the imaginary intrinsic part interference of OFDM/OQAM system in radio channel, a new pilot design approach is proposed. The new design approach can suppress the intrinsic imaginary interference in quasi-stationary channel and reduce the pilot peak power due to sparse data forms. This paper analyzes the reason why the imaginary intrinsic interference produces in the PLC (power line communication) channel and the new pilot eliminates the imaginary intrinsic interference. Compared with the pilot design of OFDM/CP,OFDM/OQAM system, it is verified that the new pilot design approach is better than OFDM/CP ,IAM-R,IAM-I and almost the same as IAM-new under MATLAB simulation platform in the PLC channel with the same channel estimation and equalization mode.

In recent years, high-speed railway and subway are being built rapidly in China. Tunnel scenario is a major scenario in some of the high-speed railways and most of the subways. Channel characteristic is the decisive condition of wireless communication system design in tunnel. The availability of multiple-input multiple-output (MIMO) in tunnel is an important issue in the next generation communication network. This paper presents results from a wideband measurement campaign at center frequency of 1.4725 and 6 GHz in a tunnel laboratory. The path loss, root-mean-square delay spread (RMS-DS) characteristics by single-input single-output (SISO) measurement and the angle spread, channel matrix singular values, and MIMO capacity at various link distances by MIMO measurement are illustrated. and these provide insights for MIMO system deployment. And also, the threshold of singular value for channel matrix rank reduction is given.

No abstract

No abstract

No abstract

No abstract