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Sun C.,Beihang University | Sun C.,China Academy of Telecommunication Research | Yang C.,Beihang University
IEEE Transactions on Vehicular Technology | Year: 2013

Two-way relaying is more spectral efficient than one-way relaying and is expected to consume less transmit power than one-way relaying to achieve the same data rate. However, when circuit power consumption is also taken into account, two-way relaying may not be more energy efficient, particularly when the bits to be transmitted from two source nodes have different numbers. To always offer high energy efficiency (EE), we propose a hybrid relay strategy, which conveys bidirectional messages with both one-way and two-way relaying. To maximize its EE, we jointly optimize the number of bits and transmission time allocated to the one- and two-way relaying stages to minimize the overall energy consumption, including the transmit power and circuit power. To reveal the behavior of the optimized hybrid relay strategy, we analyze the optimal bit allocation for the hybrid relaying under different circuit power consumption and bidirectional data amounts. Analytical and simulation results show that, in a high-traffic region where the transmit power dominates the energy consumption, the hybrid relaying degenerates into two-way relaying. By contrast, in a low-traffic region where the circuit power consumption is dominant, the proposed hybrid relaying offers significant performance gain in the sense of EE over the pure one- and two-way relaying. © 1967-2012 IEEE.

Li Y.,Beijing University of Posts and Telecommunications | Peng M.,Beijing University of Posts and Telecommunications | Wang W.,Beijing University of Posts and Telecommunications | Zhang X.,China Academy of Telecommunication Research
IEEE Wireless Communications and Networking Conference, WCNC | Year: 2013

Power allocation for orthogonal frequency division multiplexing (OFDM) based two-way relay link in cognitive relay networks is discussed in this paper. Two secondary source nodes exchange their information through a secondary relay node by using amplify-and-forward two-way relaying strategy. The goal of power allocation is to maximize the sum data rate of the secondary system subject to the constraint that the aggregation interference of the secondary system on the primary system does not exceed the given threshold. In addition, individual node power constraint is applied for both secondary source nodes and the secondary relay node. We solve the optimization problem by using dual decomposition approach, and further propose a distributed power allocation algorithm. Numerical results demonstrate the advantage of the proposed algorithm over uniform power allocation. Besides, power-constrained as well as interference-constrained regions are shown in our numerical experiments. © 2013 IEEE.

Xiuying N.,China Academy of Telecommunication Research
China Communications | Year: 2010

Services integration and network convergence is a struggling target in telecommunica-tion industry these years. The capability of IP network which can bear several services and applications, such as voice, data and video, etc. makes all-IP network a rudiment of the future convergent network by the telecommunication industry. However, current IP network can not guarantee the Q0S for real time services and the securities of networks and services. Many countries in the world have plans to do researches on next generation network, so as to obtain a predominant position in this field. This paper introduces the development of IP-based networks and services, existing issues of current IP-based network and the developments of next generation network.

Li C.,University of Science and Technology Beijing | Wu T.,China Academy of Telecommunication Research
IEEE International Symposium on Electromagnetic Compatibility | Year: 2014

This paper presents the dosimetric evaluation of the infant's exposure to electromagnetic fields from an electronic article surveillance system working at 125 kHz. A recently developed realistic infant anatomical model is deformed to achieve the standing, sitting and the supine postures. We perform the quasi-static calculation for the 99th percentile induced electric field, the peak specific absorption rate averaging over 10 g tissue and the maximum induced current density. A comparison has been made with the adult. The results show that the postures and the effective exposed part are very important factors for the dose results. The infant is not always overexposed compared with the adult. The magnetic field acquired by two methods can not be used for guidelines compliance evaluation. © 2014 The Institute of Electronics, Information and Communication Engineer.

Guo L.,Beijing University of Posts and Telecommunications | Guo L.,China Academy of Telecommunication Research | Wang Y.,Tsinghua National Laboratory for Information Sciences and Technology | Du Z.,Tsinghua National Laboratory for Information Sciences and Technology | And 2 more authors.
IEEE Antennas and Wireless Propagation Letters | Year: 2014

A compact uniplanar printed dual-antenna for laptop computers is proposed. The dual-antenna, consisting of two symmetric antenna elements and a protruded ground with an embedded T-shaped slot, is printed on a single-layer printed circuit board with a size of only 9 × 40 mm2. The antenna element is a coupled-fed loop antenna with a size of only 9 × 7 mm 2. The protruded ground with the embedded T-shaped slot reduces the mutual coupling within two frequency bands. The working mechanism is analyzed in detail for deep understanding. A prototype shows that the measured-10-dB impedance bandwidths are 190 MHz (2.38-2.57 GHz)/1.82 GHz (4.34-6.16 GHz), and the measured mutual couplings are lower than-18/-20 dB at the 2.4-and 5.2/5.8-GHz WLAN bands, respectively. The measured gains and efficiencies are better than 4.1/4.1 dBi and 65%/54% at the 2.4-and 5.2/5.8-GHz WLAN bands, respectively. © 2014 IEEE.

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