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Location-aware downlink and uplink power control and throughput optimization in cellular cognitive radio networks
Zhiyao MA, Wei CHEN, Zhigang CAO, Khaled Ben LETAIEF
Front Elect Electr Eng Chin. 2010, 5 (4): 441-448.
https://doi.org/10.1007/s11460-010-0093-z
In this paper, we consider throughput maximization in cognitive radio systems with proper power control. In particular, we incorporate location-awareness into the power control design and maximize the average throughput of the cognitive system. As we shall show, the proposed approach effectively utilizes the “spatial opportunity” to maximize the system throughput, which clearly outperforms traditional power control methods. Further, the proposed approach still exhibits significant throughput gain even considering imperfect position information, with appropriate robust design modifications.
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Concatenated Alamouti codes using multi-level modulation and symbol mapping diversity technique
Mingwei CAO, Guangguo BI
Front Elect Electr Eng Chin. 2010, 5 (4): 464-469.
https://doi.org/10.1007/s11460-010-0115-x
A family of space-time block codes (STBCs) for systems with even transmit antennas and any number of receive antennas is proposed. The new codeword matrix is constructed by concatenating Alamouti space-time codes to form a block diagonal matrix, and its dimension is equal to the number of transmit antennas. All Alamouti codes in the same codeword matrix have the same information; thus, full transmit diversity can be achieved over fading channels. To improve the spectral efficiency, multi-level modulations such as multi-quadrature amplitude modulation (M-QAM) are employed. The symbol mapping diversity is then exploited between transmissions of the same information from different antennas to improve the bit error rate (BER) performance. The proposed codes outperform the diagonal algebraic space-time (DAST) codes presented by Damen [Damen et al. IEEE Transactions on Information Theory, 2002, 48(3): 628–636] when they have the same spectral efficiency. Also, they outperform the 1/2-rate codes from complex orthogonal design. Moreover, compared to DAST codes, the proposed codes have a low decoding complexity because we only need to perform linear processing to achieve single-symbol maximum-likelihood (ML) decoding.
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Simplified parasitic capacitance extraction of shield in HVDC converter system with boundary element method
Shili LIU, Zezhong WANG, Jing SUN
Front Elect Electr Eng Chin. 2010, 5 (4): 505-509.
https://doi.org/10.1007/s11460-010-0097-8
It is critical to build a wide-band circuit model to conduct research on the characteristics of the electromagnetic disturbance source during the localization of high voltage direct current (HVDC) technology. Parasitic capacitance is most essential for modeling the equivalent circuit, so a fast and accurate computation of capacitance parameters plays a vital role. Because of the large size and complex structure of the converter equipment, it is impossible to obtain capacitance parameters by means of measurement or simulating calculation with finite element software. In this paper, a simplified method of capacitance extraction based on boundary element method is proposed, which can provide an efficient means of establishing simulation models. In the method presented, simulation model of the shield may not be chamfered. Consequently, the edge and corner of the shield do not need to be handled with a sphere, cylinder and other curved surface model. The availability of this method is demonstrated by comparing the capacitance parameters of chamfered shield with that of non-chamfered shield.
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15 articles
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