Can Sun

Beijing University of Aeronautics and Astronautics (Beihang University), Peping, Beijing, China

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Publications (12)15.36 Total impact

  • Can Sun, Chenyang Yang
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    ABSTRACT: 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.
    IEEE Transactions on Vehicular Technology 01/2013; 62(8):3737-3751. · 2.06 Impact Factor
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    ABSTRACT: In this paper, we study energy efficient orthogonal frequency division multiplexing (OFDM) relay system, where two source nodes communicate with each other via a half-duplex amplify-and-forward relay node. We aim to maximize the energy efficiency (EE), where both the transmit and circuit power consumptions are taken into consideration. To this end, we optimize the active number of subcarriers and the number of bits to each subcarrier at the two source nodes. The optimal solution turns out to be a bidirectional water-filling bit allocation to minimize the overall transmit power, and a subcarrier reduction algorithm to balance the transmit and circuit power consumptions. When the data amounts at the two source nodes are unequal, the bidirectional water-filling leads to a hybrid one- and two-way relaying strategy, which employs one-way relaying on some subcarriers and two-way relaying on some of the other subcarriers. Simulation results demonstrate that the hybrid one- and two-way relaying with subcarrier reduction, which is optimized towards EE, is more energy efficient than that without subcarrier reduction, which only minimizes the transmit power.
    IEEE Transactions on Communications 01/2013; 61(5):1797-1809. · 1.75 Impact Factor
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    ABSTRACT: In this paper, we design interference free transceivers for multi-user two-way relay systems, where a multi-antenna base station (BS) simultaneously exchanges information with multiple single-antenna users via a multi-antenna amplify-and-forward relay station (RS). To offer a performance benchmark and provide useful insight into the transceiver structure, we employ alternating optimization to find optimal transceivers at the BS and RS that maximizes the bidirectional sum rate. We then propose a low complexity scheme, where the BS transceiver is the zero-forcing precoder and detector, and the RS transceiver is designed to balance the uplink and downlink sum rates. Simulation results demonstrate that the proposed scheme is superior to the existing zero forcing and signal alignment schemes, and the performance gap between the proposed scheme and the alternating optimization is minor.
    IEEE Transactions on Communications 06/2012; · 1.75 Impact Factor
  • Can Sun, Chenyang Yang
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    ABSTRACT: In this paper, we compare the energy efficiencies (EEs) of direct transmission (DT), one-way relay transmission (OWRT) and two-way relay transmission (TWRT) in a system where two sourcie nodes transmit to each other and may be assisted by an amplify-and-forward relay node. We first find the maximum EEs of DT, OWRT and TWRT by jointly optimizing the transmission time and the transmit powers at each node. Then we compare the maximum EEs of the three strategies, and analyze the impact of circuit powers and bidirectional data amounts. Analytical and simulation results show that relaying is not always more energy efficient than DT. The EE of TWRT is higher than those of DT and OWRT when the bidirectional data amounts are equal. Otherwise, the advantage of TWRT diminishes, while either DT or OWRT may provide higher EE.
    Communications (ICC), 2012 IEEE International Conference on; 01/2012
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    ABSTRACT: In this paper, we design energy efficient relay transmission strategy for an orthogonal frequency division multiplexing (OFDM) system, where two source nodes exchange information with each other via an amplify-and-forward relay node. To maximize the energy efficiency (EE), which is defined as the number of transmitted bits per unit of energy, we jointly optimize the bidirectional bit allocation, which leads to a hybrid one- and two-way relay scheme. In particular, we propose a bit allocation algorithm to balance the transmit and circuit power consumptions of the hybrid relay in order to minimize the overall power consumption. Simulation results show that the proposed algorithm achieves much higher EE than the approach that only minimizes the transmit power, and the hybrid relay is more energy efficient than the pure one- and two-way relay.
    Personal Indoor and Mobile Radio Communications (PIMRC), 2012 IEEE 23rd International Symposium on; 01/2012
  • Can Sun, Chenyang Yang
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    ABSTRACT: In this paper, we design energy efficient relay transmission strategy in a system where two source nodes transmit to each other assisted by an amplify-and-forward relay node. We first compare the energy efficiencies (EEs) between one-way relay transmission (OWRT) and two-way relay transmission (TWRT), which shows that when the bidirectional data amounts are equal, TWRT performs better, otherwise, OWRT may offer higher EE. To achieve the maximal EE in various settings, we propose hybrid relay transmission (HRT) that transmits partial messages with OWRT and the remaining messages with TWRT, and jointly optimize the data amounts and transmission time allocated to the OWRT and TWRT parts. Simulation results show the superiority of the HRT over both OWRT and TWRT.
    Acoustics, Speech and Signal Processing (ICASSP), 2012 IEEE International Conference on; 01/2012 · 4.63 Impact Factor
  • Source
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    ABSTRACT: In this paper, we study a multi-user multi-antenna two-way relay system, where a multi-antenna base station (BS) exchanges uplink and downlink signals with multiple users via a multi-antenna amplify-and-forward relay station (RS). We jointly design the BS and RS transceivers, aiming to maximize the system bidirectional sum rate under inter-user interference free constraint. Since the optimization problem is non-convex, we employ alternating optimization algorithm to design the transmit and receive weighting matrices at the BS and RS. Simulation results show that the proposed solution offers higher bidirectional sum rate than existing schemes.
    Acoustics, Speech and Signal Processing (ICASSP), 2011 IEEE International Conference on; 06/2011 · 4.63 Impact Factor
  • Source
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    ABSTRACT: In this paper, we design transceivers in a multi-user multi-antenna two-way relay system, where a single multi-antenna base station exchanges information with multiple users via a single multi-antenna relay station. We consider the half-duplex amplify-and-forward relay protocol. We aim to maximize the bidirectional sum rate under the constraint of no interference among different users. Suboptimal solutions to the problem that respectively maximizing the uplink and downlink rates are derived. We then introduce a threshold to balance the uplink and downlink rates so as to maximize the bidirectional sum rate. Simulation results show that the proposed scheme achieves considerably higher bidirectional sum rate than existing schemes.
    Global Telecommunications Conference (GLOBECOM 2010), 2010 IEEE; 01/2011
  • Can Sun, Chenyang Yang
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    ABSTRACT: Two-way relay transmission (TWRT) is more spectral efficient than direct transmission (DT) and one-way relay transmission (OWRT). In this paper, we try to find out if TWRT is also more energy efficient in practice. To this end, we first derive and compare the energy efficiency of DT, OWRT and TWRT systems, when either the receiver processing power consumption is taken into account or not. We then compare the maximal energy efficiency achieved by TWRT and OWRT, as well as the corresponding spectral efficiency. Both analytical and simulation results show that TWRT is not always more energy efficient than DT and OWRT, depending on the channel condition, processing power consumption and the bidirectional date rate requirements. Generally speaking, in high spectral efficiency and large path loss attenuation region, the TWRT provides high energy efficiency.
    Proceedings of the Global Communications Conference, GLOBECOM 2011, 5-9 December 2011, Houston, Texas, USA; 01/2011
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    ABSTRACT: In this paper, we study low feedback user grouping in downlink cooperative transmission multi-antenna systems. Users in the same group are served on the same frequency and time resource by multiple cooperative BSs using the zero-forcing precoder. We first derive the user's average received signal to interference and noise ratio (SINR). It shows that each user's SINR is an increasing function of the large scale signal to interference ratio (SIR) of users in neighbor cells, which can be obtained using the large scale channel information. We then propose a novel fair user grouping algorithm based on the large scale SIR. Simulation results show that our algorithm achieves better cell edge throughput compared with existing methods with minor reduction of cell throughput.
    01/2010;
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    ABSTRACT: In this paper, we analyze the performance of beamforming and its combination with link adaptive technologies in the presence of co-channel interference (CCI) of downlink multiple-input multiple-output (MIMO) - code division multiple access (CDMA) cellular systems. The results show that the performance of MIMO systems with beamforming will mainly be degraded by the bursty nature of the CCI.
    01/2008;
  • Source
    Can Sun, Chenyang Yang
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    ABSTRACT: Relaying is supposed to be a low energy consumption technique since the long distance transmission is divided into several short distance transmissions. When the power consumptions (PCs) other than that consumed by transmitting information bits is taken into account, however, relaying may not be energy efficient. In this article, we study the energy efficiencies (EEs) of one-way relay transmission (OWRT) and two-way relay transmission (TWRT) by comparing with direct transmission (DT). We consider a system where two source nodes transmit to each other with the assistance of a half-duplex amplify-and-forward relay node. We first find the maximum EEs of DT, OWRT, and TWRT by optimizing the transmission time and the transmit powers at each node. Then we compare the maximum EEs of the three strategies, and analyze the impact of circuit PCs and data amount. Analytical and simulation results show that relaying is not always more energy efficient than DT. Moreover, TWRT is not always more energy efficient than OWRT, despite that it is more spectral efficient. The EE of TWRT is higher than those of DT and OWRT in symmetric systems where the circuit PCs at each node are identical and the numbers of bits to be transmitted in two directions are equal. In asymmetric systems, however, OWRT may provide higher EE than TWRT when the numbers of bits in two directions differ significantly.
    EURASIP Journal on Wireless Communications and Networking 2012(1). · 0.54 Impact Factor