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991.
Shao‐I Chu Wei‐Cheng Lin Hung‐Peng Lee Hsin‐Chiu Chang 《Wireless Communications and Mobile Computing》2013,13(16):1464-1481
This paper derives the asymptotic symbol error rate (SER) and outage probability of decode‐and‐forward (DF) cooperative communications over Rician fading channels. How to optimally allocate the total power is also addressed when the performance metric in terms of SER or outage probability is taken into consideration. Analysis reveals the insights that Rician factor has a great impact on the system performance as compared with the channel variance, and the relay–destination channel quality is of importance. In addition, the source–relay channel condition is irrelevant to the optimal power allocation design. Simulation and numerical evaluation substantiate the tightness of the asymptotic expressions in the high‐SNR regions and demonstrate the accuracy of our theoretical analysis. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
992.
软件无线电技术在雷达设计中的应用 总被引:1,自引:0,他引:1
软件无线电作为一种新的无线通讯概念,他的应用研究主要集中于军用通讯以及民用移动通讯领域。随着DDS,DSP,FPGA和ASIC等技术的发展,软件无线电技术在雷达信号的产生及处理等方面的应用已逐渐成熟,软件化雷达的实际应用已变得十分可行。软件无线电技术的应用使雷达系统具有可编程、可扩展、灵活性高的特点。本文将软件无线电的设计思想应用于雷达系统的设计中,并对系统的硬件设计、元器件选择及软件设计流程等进行了简单说明,给出了相应的实现方案。 相似文献
993.
Layered Access Control Schemes on Watermarked Scalable Media 总被引:8,自引:0,他引:8
Feng-Cheng Chang Hsiang-Cheh Huang Hsueh-Ming Hang 《The Journal of VLSI Signal Processing》2007,49(3):443-455
Intellectual Property (IP) protection is a critical element in multimedia transmission and delivery systems. Conventional
IP protection on multimedia data can be categorized into encryption and watermarking. In this paper, a structure to perform layered access control on scalable media by combining encryption and robust watermarking
is proposed, implemented, and verified. By taking advantages of the nature of both encryption and watermarking, copyrights
of multimedia contents can be well protected and at the same time, multiple-grade services can be provided. In the summated
examples, we assume a scalable transmission scheme over the broadcasting environment and use it to test the effectiveness
of proposed method. When the embedded watermark is extracted with high confidence, the key to decrypt the next layer can be
perfectly recovered. Then, the media contents are reconstructed and the copyrights are assured. The application examples also
demonstrate the practicality of the proposed system.
相似文献
Hsueh-Ming HangEmail: |
994.
Chang Hong Lin Yuan Xie Wolf W. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2007,15(10):1160-1171
We propose a new class of methods for VLIW code compression using variable-sized branch blocks with self-generating tables. Code compression traditionally works on fixed-sized blocks with its efficiency limited by their small size. A branch block, a series of instructions between two consecutive possible branch targets, provides larger blocks for code compression. We compare three methods for compressing branch blocks: table-based, Lempel-Ziv-Welch (LZW)-based and selective code compression. Our approaches are fully adaptive and generate the coding table on-the-fly during compression and decompression. When encountering a branch target, the coding table is cleared to ensure correctness. Decompression requires a simple table lookup and updates the coding table when necessary. When decoding sequentially, the table-based method produces 4 bytes per iteration while the LZW-based methods provide 8 bytes peak and 1.82 bytes average decompression bandwidth. Compared to Huffman's 1 byte and variable-to-fixed (V2F)'s 13-bit peak performance, our methods have higher decoding bandwidth and a comparable compression ratio. Parallel decompression could also be applied to our methods, which is more suitable for VLIW architectures. 相似文献
995.
996.
New wide-band DC-block cymbal bandpass filter 总被引:3,自引:0,他引:3
A new low-loss dc-blocking parallel-cascaded bandpass filter is presented. The filter is much easier to use and fabricate, more compact, and simpler to design than the conventional end- or parallel-coupled line filters. The filter has a wide passband with a 2:1 voltage standing-wave ratio bandwidth of around 10% and an insertion loss of 0.5 dB at 10 GHz. Simulated results agree very well with experimental results 相似文献
997.
SDMA技术是提高频谱利用率的有效技术,但在判决反馈最小均方波束形成中,在深衰落之后期望用户波束会指向干扰用户,严重影响了波束形成的性能。文中提出在波束形成和信道解码之后,经过编码、交织,重新生成波束形成的参考信号,再进行波束形成,有效克服了深衰落之后的波束指向错误。计算机仿真结果证明了该方法的有效性。 相似文献
998.
A novel broadband circularly-polarised (CP) square slot antenna fed by an asymmetric coplanar waveguide (CPW) from a corner of the slot is proposed. A CP bandwidth larger than 10% can be attained simply by using an inverted-L tuning stub protruded from the signal line of the CPW. With an additional pair of grounded strips implanted in the slot, the 3 dB axial-ratio bandwidth and the VSWR ⩽ 2 impedance bandwidth can be greatly raised to be as high as 30 and 35%, respectively. 相似文献
999.
Chiang Po-Jui Wu Chin-Lung Teng Chun-Hao Yang Chu-Sheng Chang Hung-chun 《Quantum Electronics, IEEE Journal of》2008,44(1):56-66
New full-vectorial optical waveguide eigenmode solvers using pseudospectral frequency-domain (PSFD) formulations for optical waveguides with arbitrary step-index profile are presented. Both Legendre and Chebyshev collocation methods are considered in the formulation. By applying Legendre-Lagrange or Chebyshev-Lagrange interpolating polynomials to the approximation of spatial derivatives at collocation points, the Helmholtz equations for the transverse-electric or transverse-magnetic components are converted into a matrix eigenvalue equation which is then solved for the eigenmodes by the shift inverse power method. Suitable multidomain division of the computational domain is arranged to deal with general curved interfaces of the refractive-index profile together with a curvilinear mapping technique for each subdomain so that field continuity conditions can be carefully imposed across the dielectric interfaces, which is essential in achieving high numerical accuracy. The solver is applied to the optical fiber for the assessment of its numerical performance, to the classical benchmark rib waveguide for comparing with existing high-accuracy results, and to the fused fiber structure for demonstrating its robustness in calculating the form birefingence. 相似文献
1000.
This paper introduces a novel channel-prediction technique for an orthogonal frequency-division multiplexing (OFDM)/frequency-division duplex (FDD) system to support an adaptive-modulation and coding (AMC) scheme over a rapidly time-varying multipath fading channel. Most channel-prediction techniques assume that there is no channel variation in the predefined time duration, e.g. the slot. As a result, those techniques cannot compensate for the degradation of packet-error-rate (PER) performance, resulting from the rapid channel variation over the slot duration. In this paper, we propose a novel two-step channel-prediction technique that considers the time-varying nature of a channel over the duration of interest. Simulation results show that the AMC scheme of the OFDM/FDD system utilizing the proposed channel-prediction technique can guarantee the target PER of 1% without any loss of system throughput compared with a case supported by a conventional channel prediction under ITU-R Veh A 30 km/h. 相似文献