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Luo Z.,Shanghai JiaoTong University | Ding M.,Sharp Laboratories of China Company | Luo H.,Shanghai JiaoTong University | Luo H.,Shanghai Normal University
IEEE Communications Letters | Year: 2014

In this letter, we propose a novel dynamic cell on/off scheduling algorithm in small cell networks based on the Stackelberg game. The objective of the proposed algorithm is to optimize the packet throughput performance with a tradeoff of energy consumption. In our system-level simulations, the proposed algorithm exhibits considerable performance gains, in terms of packet throughput per unit of energy consumption, compared with two existing algorithms respectively based on random on/off and packet arrival-triggered cell activation. © 2014 IEEE. Source

Ding M.,Shanghai JiaoTong University | Ding M.,Sharp Laboratories of China Company | Zou J.,Shanghai JiaoTong University | Yang Z.,Laboratories of China Co. | And 2 more authors.
IEEE Transactions on Vehicular Technology | Year: 2012

In this paper, we propose a sequential and incremental precoder design for downlink joint transmission (JT) network multiple-input-multiple-output (MIMO) systems with imperfect backhaul links. The objective of our design is to minimize the maximum of the substream mean square errors, which dominates the average bit error rate (BER) performance of the system. In the proposed scheme, we first optimize the precoder at the serving base station (BS) and then sequentially optimize the precoders of nonserving BSs in the JT set according to the descending order of their probabilities of participating in the JT. The BS-wise sequential optimization process can improve system performance when some BSs have to temporarily quit the JT operations because of poor instant backhaul conditions. In addition, the precoder of an additional BS is derived in an incremental way, i.e., the sequentially optimized precoders of the previous BSs are fixed, and thus, the additional precoder plays an incremental part in multi-BS JT operations. An iterative algorithm is designed to jointly optimize the substream precoder and substream power allocation for each additional BS in the proposed sequential and incremental optimization scheme. Simulations show that, under the practical backhaul link conditions, our scheme significantly outperforms the autonomous global precoding scheme in terms of BER performance. © 2012 IEEE. Source

Ding M.,Sharp Laboratories of China Company | Luo H.,Shanghai Normal University | Luo H.,Shanghai JiaoTong University | Chen W.,Shanghai JiaoTong University | Chen W.,Guilin University of Electronic Technology
IEEE Transactions on Wireless Communications | Year: 2014

In this paper, we investigate the robust beamforming for multi-user multiple-input single-output systems underquantized channel direction information (CDI) with per-antenna power constraints. The robustness of the consideredbeamforming design is achieved in the sense that the stochastic interference leakage is below a certain level by a givenprobability. Our design objective is to maximize the expectation of the weighted sum-rate performance. From thediscussion of the non-robust optimal beamforming based on the polyblock algorithm, we propose a robust beamformingscheme for the quantized CDI case with per-antenna power constraints. In the proposed beamforming scheme, we useJensen's inequality to generate a tractable feasibility problem for the polyblock algorithm and apply the semi-definiteprogramming relaxation, as well as the randomization technique to find its approximate rank-one matrix solution and userequipments' beamforming vectors. Simulation results show that substantial gains can be achieved by the proposed schemecompared with the existing schemes in terms of the average weighted sum-rate performance. Although very high complexityis required for the implementation of the proposed scheme, it stands as a good benchmark for robust beamformingdesigns. © 2002-2012 IEEE. Source

Zhao P.,Shanghai JiaoTong University | Zhang M.,Shanghai JiaoTong University | Zhang M.,Sharp Laboratories of China Company | Yu H.,Shanghai JiaoTong University | And 3 more authors.
IEEE Transactions on Information Forensics and Security | Year: 2015

This paper studies the beamforming design problem of a multiuser downlink network, assuming imperfect channel state information known to the base station. In this scenario, the base station is equipped with multiple antennas, and each user is wiretapped by a specific eavesdropper where each user or eavesdropper is equipped with one antenna. It is supposed that the base station employs transmit beamforming with a given requirement on sum transmitting power. The objective is to maximize the sum secrecy rate of the network. Due to the uncertainty of the channel, it is difficult to calculate the exact sum secrecy rate of the system. Thus, the maximum of lower bound of sum secrecy rate is considered. The optimization of the lower bound of sum secrecy rate still makes the considered beamforming design problem difficult to handle. To solve this problem, a beamforming design scheme is proposed to transform the original problem into a convex approximation problem, by employing semidefinite relaxation and first-order approximation technique based on Taylor expansion. In addition, with the advantage of low complexity, a zero-forcing-based beamforming method is presented in the case that base station is able to nullify the eavesdroppers' rate. When the base station does not have the ability, user selection algorithm would be in use. Numerical results show that the former strategy achieves better performance than the latter one, which is mainly due to the ability of optimizing beamforming direction, and both outperform the signal-to-leakage-and-noise ratio-based algorithm. © 2005-2012 IEEE. Source

Li Y.,Shanghai JiaoTong University | Ying K.,Shanghai JiaoTong University | Huang L.,Sharp Laboratories of China Company | Yu H.,Shanghai JiaoTong University | Luo H.,Shanghai JiaoTong University
IEEE Wireless Communications and Networking Conference, WCNC | Year: 2013

The heterogeneous multicast networks are the networks with several wireless technologies that provide multicast service. Due to the high data rate of the service, point-to-point (P2P) transmission mode, which is employed by unicast channels, is no longer the best mode because of its inefficiency in power consumption and spectrum utilization. Compared with P2P, point-to-multipoint (P2M) transmission mode is recognized as a more promising mode for multicast service. But since P2M mode is provided by mulitcast channels who have turn-on thresholds, the P2M link of a transmission point (TP) is not always available for User Equipments (UEs). To deal with the UEs' cell/transmission mode selection problem in heterogeneous multicast networks, this paper proposes a novel auction mechanism. In the auction process, TPs act as auctioneers who own channel resource and UEs act as bidders who wish to buy these channels for multicast service. Different from many auction based mechanism, we design two kinds of prices, one for unicast channels providing P2P links and the other for multicast channels providing P2M links. In auction, the equilibrium is defined as the state that no UE wishes to change it decision. Through simulation, we show that the auction process converges to a equilibrium state, and the mechanism achieves about 40%-50% power efficiency compared with that of random access. © 2013 IEEE. Source

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