As a low-complexity and energy-efficient multiple input multiple output (MIMO) technique, spatial modulation (SM) has received much interest recently. Combining SM with cooperative relaying, the performance of SM systems can be significantly improved. Considering joint transmit-receive-correlated Rayleigh channels, the error performance and power allocation (PA) of the amplify-and-forward (AF) relaying aided cooperative SM system are presented in this paper. Based on the moment generating function (MGF), the probability density function (PDF) of effective signal-to-noise ratio (SNR) is derived. With this PDF, a closed-form expression of the pairwise error probability (PEP) is obtained. Utilizing the obtained PEP and the union bound of bit error rate (BER), the approximate average BER expression is further derived, which will benefit the performance analysis of the system in spatially correlated channels. According to the asymptotical performance analysis at high SNR, an asymptotic BER expression is also derived. By minimizing this asymptotic BER, a suboptimal power allocation scheme is developed, and the closedform PA coefficients are attained. Besides, the diversity order of system is also analyzed and derived for the performance evaluation. Numerical results show that our theoretical analysis is valid, and can match the corresponding simulation well. Moreover, the proposed PA scheme can achieve superior BER performance over the conventional equal PA scheme since the powers are well allocated in terms of channel information. INDEX TERMS Amplify and forward, power allocation, spatial modulation, bit error rate, spatial correlation. XIANGBIN YU received the Ph.D. degree in communication and information systems from the
Finger seal is a new type of compliant seal configuration, which is an important part of an aero-engine and its accessory systems. It has superior sealing performance compared with conventional labyrinth seals and a lower manufacturing cost than brush seals. However, numerical simulation of the leakage characteristics of an entitative finger seal structure are very difficult to implement, because the finger laminates are in close contact with one another and the radial deformation of the fingers caused by interference between seal and rotor as well as the centrifugal and thermal expansion of the rotor can change the geometric structure of seal. The published leakage analysis models of finger seal ignore the leakage throughout the interstices between fingers or finger laminates. In view of this, the authors propose an anisotropic porous media model for leakage analysis of finger seal. The model considers the effects of the seal structure parameters, upstream and downstream axial pressure differences and the fit status between seal and rotor. First, the equations of the model and their parameters were obtained by theoretical derivations, while the correction factors were determined based on experiment leakage data in the literature. Second, the accuracy of the model was validated by calculating the leakage of a known seal structure in the literature and comparing these results with the experimental data. At last, a comparison between the anisotropic and isotropic porous media model is carried out. The results of the validation examples show that the model can simulate the leakage of finger seal very well with the errors between numerical results and experimental data are less than 10% for two-thirds of the data points.
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