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International Conference on Mobile Ad-hoc and Sensor Networks, MSN

作者： Lili Xie Chunjing Hu Wenjun Wu Zhenning Shi Wireless Signal Processing and Network Lab Key Laboratory of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing China France Telecom Research and Development Beijing Beijing China

Since the Quality of Experience (QoE) metric directly reflects the subjective experiences of users, the resource allocation techniques with the objective to improve QoE instead of conventional metrics are efficient in resource utilization. This kind of techniques can avoid wasting resources in providing perfect objective metric which may have little or even no effect on user experience. This paper presents a QoE-aware power allocation algorithm in multiuser Orthogonal Frequency Division Multiplexing (OFDM) systems. The power allocation problem is formulated to maximize the overall QoE subject to the total transmit power constraint. The original model is solved by means of transformation and approximation, since it is difficult to develop a closed-form solution. Simulation results show that the proposed algorithm can enhance the performance in terms of both the overall QoE and single user QoE in comparison with the classical water-filling algorithm.

关键词： Resource management OFDM Measurement Quality of service Throughput Optimization Convex functions

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Average interference analysis in two-tier wireless networks

Average interference analysis in two-tier wireless networks

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IEEE Globecom Workshops

作者： Wenjun Wu Lili Xie Wenbo Wang Xuanyi Zhang Wireless Signal Processing and Network Lab Key Laboratory of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing China IT Department Beijing Capital International Airport Company Limited Beijing China

The two-tier wireless network comprising a conventional cellular network overlaid with femtocells is considered as an economical network configuration to provide high quality indoor coverage. However, the cross-tier interference induced by femtocells will cause significant performance degradations to cellular users. In this paper, the closed-form expressions of the average cross-tier interference powers are derived, with the spacial distributions of home eNodeBs (HeNBs) and home user equipments (HUEs) modeled as a homogeneous spatial poisson point processes (SPPP). Considering the receiver sensitivity degradations of macro eNodeBs (MeNBs) and macro user equipments (MUEs), the acceptable cross-tier interference power can be obtained. Combining the acceptable power and the closed-form expressions of the average cross-tier interference, the constraints on the femto-tier configurations are given in terms of the transmit power and the density of femtocells as well as the required minimum distance between the aggressor and the victim. Analytical results of the required minimum distances between MUEs (resp. MeNBs) and HeNBs (resp. HUEs) are calculated when the transmit power and the density of femtocells are fixed. At last, simulation results validate our analysis.

关键词： Interference Receivers Degradation Sensitivity Fading Feedback amplifier Noise

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Coordinated Eigen Beamforming for Multi-Pair MIMO Two-Way Relay Network

Coordinated Eigen Beamforming for Multi-Pair MIMO Two-Way Re...

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2011 IEEE Global Telecommunications Conference - GLOBECOM 2011

作者： Haiyang Xin Yuexing Peng Chenwei Wang Yunchuan Yang Wenbo Wang Wireless Signal Processing and Network Lab Key Laboratory of Universal Wireless Comm. Ministry of Education Beijing University of Posts and Telecommunications Beijing China CPCC EECS Dept University of California Irvine Irvine CA USA

We consider a multi-pair two-way relay (TWR) network where the multi-antenna users of each pair exchange information via a multi-antenna relay. The interesting challenge is how to deal with the inter- user interference and explore the potential of multiple antennas concurrently. Beamforming methods in previous works are based on the criteria of zero forcing (ZF) and minimum mean square error (MMSE) to mitigate the inter-user interference. However, since the user already knows its own information, it is unnecessary to mitigate the intra-pair interference at the relay. In this paper, we propose a coordinated eigen beamforming (CEB) scheme, which maximizes the effective channel gain of each user in the sub-space nulling the inter-pair interference. The CEB scheme is implemented with an iterative optimization algorithm with limited iterations. Additionally, the power loading scheme is adopted after convergence to guarantee fairness among users. Simulation results indicate our scheme achieves near full diversity order within the sub-space, outperforming pervious works.

关键词： Relays Array signal processing Vectors Interference Antennas Optimization Bit error rate

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A Simple Approach of Gaussian Approximation for Channel Capacity in Multiple-Antenna Systems

A Simple Approach of Gaussian Approximation for Channel Capa...

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IEEE Conference on Vehicular Technology (VTC)

作者： Rongrong Qian Yuan Qi Peng Tao Wenbo Wang Jun Yang School of Automation Engineering Beijing University of Posts and Telecommunications (BUPT) Beijing China School of Electronic Engineering Beijing University of Posts and Telecommunications (BUPT) Beijing China Wireless Signal Processing and Network Lab Key Laboratory of Universal Wireless Communication Ministry of Education Beijing University of Posts and Telecommunications (BUPT) Beijing China

In this paper, the theoretical insight into Gaussian approximation of channel capacity for several classes of Rayleighfading multiple-antenna systems is presented. In particular, a theorem, which has not been developed by the former studies of Gaussian approximation, is introduced to these systems. Then guided by this theorem, a new approach of determining the approximate mean and variance for Gaussian approximation is proposed, which is simpler and more intuitive than the existed approach. The simulation results show the availability of such new approach.

关键词： Gaussian approximation Channel capacity Approximation methods MIMO Receiving antennas Rayleigh channels Monte Carlo methods

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Inter-carrier Interference Analysis and Mitigation for OFDM System over Fast Fading Channels

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电子学报(英文版) 2010年第1期19卷 181-186页

作者： PENG Yuexing ZHAO Hui WANG Wenbo Key Lab of Universal Wireless Communications Ministry of Education Wireless Signal Processing and Network Lab Schoolof Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing China

Inter-carrier interference (ICI) due to Doppler spread is analyzed for OFDM system in highly mobile applications, and then an iterative ICI mitigation method is developed. With the Jakes' model for the Doppler power spectrum and linear model in one OFDM symbol interval for time-varying channel, the analytical closed-form expression of signal-to-interference ratio (SIR) and signal-to-interference-plus-noise ratio (SINR) are developed with neither assumption on the statistical characteristic of ICI nor constraint on the statistical model for the fading channels. Then, a joint detection algorithm is proposed to iteratively mitigate ICI and estimate channel and detect symbols, where the ICI from a few neighboring interfering subcarriers which contribute the majority of ICI power is regenerates and partially subtracted from the received signal in order to mitigate decision error accumulation. The number of concerned interfering subcarriers and the optimal partial ICI cancellation factor are investigated for the tradeoff of complexity reduction and Mean square error (MSE) minimization. Simulation results verify the proposed method can mitigate ICI effectively.

关键词： OFDM系统干扰分析衰落信道运营商信号干扰比减灾线性模型统计特性

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Bit error probability of distributed Turbo coded relay systems over quasi-static Rayleigh fading channels

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The Journal of China Universities of Posts and Telecommunications 2010年第2期17卷 41-45页

作者： PENG Yue-xing WU Mu-zi ZHAO Hui WANG Wen-bo Wireless Signal Processing and Network Laboratory Key Lab of Universal Wireless Communications Ministry of Education School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

As is known, distributed Turbo coding （DTC） performs close to the theoretic outage probability bound of a relay channel when correct decoding is assumed at the relay. However, decoding error is inevitable in practical fading channels due to the error-prone feature of radio channels, and the decoding error propagation in DTC scheme will severely degrade the error performance of the relay system. As a result, it is necessary to evaluate the error performance of the DTC scheme in multi-hop relaying wireless systems in practical fading channels. Moreover, the theoretical method of analysis provides an effective tool for obtaining the error performance besides lengthy simulations. In this article, the concept of equivalent signal-to-noise ratio （SNR） of the two-hop relay channel and the method of computing equivalent SNR are developed, and then the upper bound on the bit error probability （BEP） of DTC relay systems is analyzed by use of Turbo code＇s distance spectrum, the concept of uniform interleaver, the limit-before-averaging technique, and the union bound method. Both theoretical analysis and numerical simulation are implemented for relay systems with DTC scheme over quasi-static Rayleigh fading channels. The results show that the upper bound approaches the simulation results in the medium to high SNR region.

关键词： bit error probability distributed Turbo code relay network union bound distance spectrum SNR

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An uplink hybrid multiple access scheme for wireless communication systems

An uplink hybrid multiple access scheme for wireless communi...

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作者： Zheng, Kan Wang, Yuyu Long, Hang Wei, Meiying Wang, Wenbo Wireless Signal Processing and Network Lab. Key Laboratory of Universal Wireless Communication Beijing University of PostsandTelecommunications Beijing 100088 China

ISBN: (纸本)9780984589333

Both orthogonal frequency division multiplexing (OFDM) and single-carrier (SC) with frequency division multiple access (FDMA) have been regarded as a possible solution for improving the performance of future generation wireless communication systems. OFDM can better exploit the frequency diversity gain while SC-FDMA is less sensitivity to non-linearity of amplifier with lower peak-to-average power ratio (PAPR). In this paper, a new hybrid multiple access scheme is proposed in order to combine the advantages of both OFDM and SC-FDMA schemes, while the effects of both schemes on the realistic system assumptions of the practical high power amplifier (HPA) model and adaptive modulation/coding (AMC) technique are considered. Our simulation results have demonstrated the effectiveness of the proposed scheme and the conclusion is given.

关键词： Frequency division multiple access

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Complexity study of sphere decoding in multi-antenna systems

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The Journal of China Universities of Posts and Telecommunications 2010年第3期17卷 1-5页

作者： QIAN Rong-rong QI Yuan PENG Zao WANG Wen-bo Wireless Signal Processing and Network Lab (Key Lab of Universal Wireless Communication Ministry of Education) Beijing University of Posts and Telecommunications Beijing 100876 China School of Electronic Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

In this article a bridge between the expected complexity and performance of sphere decoding （SD） is built. The expected complexity of SD for infinite lattices is then investigated, which naturally is the upper-bound of those for all the finite lattices if given by the same channel matrix and signal noise ratio （SNR）. Such expected complexity is an important characterization of SD in multi-antenna systems, because no matter what modulation scheme is used in practice （generally it has finite constellation size） this upper-bound holds. Above bridge also leads to a new method of determining the radius for SD. The numerical results show both the real value and upper-bound of average searched number of candidates in SD for 16-QAM modulated system using the proposed sphere radius determining method. Most important of all new understandings of expected complexity of SD are given based on above mentioned theoretic analysis and numerical results.

关键词： MIMO sphere decoding expected complexity

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Cross-layer performance analysis in cooperative relay networks with poission and self-similar traffic input

Cross-layer performance analysis in cooperative relay networ...

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2010 IEEE International Conference on wireless Information Technology and Systems, ICWITS 2010

作者： Xiao, Jing Ji, Xiaodong Zhang, Xing Wang, Wenbo Wireless Signal Processing and Network Laboratory Key Lab of Universal Wireless Communication Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

ISBN: (纸本)9781424470914

Considering the self-similarity and the fading characteristic of wireless channels, this paper mainly studies the queuing performance difference between self-similar traffic input which is characterized by FBM model and SRD traffic input by Poisson model, in terms of tail distribution and loss probability of the queue length respectively under infinite and finite buffer size for infrastructure based two-hop relay wireless network. Assuming the same average traffic arrival rate, we find that the natural property of self-similar traffic and Poisson traffic constitutes the root causes of network performance differences, specifically, referring to Hurst parameter and the variance value. By many simulation measurements, the major contributions and main conclusions in this paper can be summarized as follows:(1) Compared with Poisson traffics, effects of Hurst on network performance are constrained on the variance and buffer size, and the variance has a greater impact;(2) When the variance coefficient is large, the larger the Hurst value is, the more evident the network performance difference between these two traffic flows is and the worse queuing performance of FBM traffic input is;In particular, when Hurst is 0.5, that is to say traffic is non-self-similar traffic, performances of the both are almost the same;(3) When the variance coefficient is small, no matter how much the Hurst value is, both traffic flows perform little differences, therefore, most existing studies of the self-similar traffic on network performance concentrate on the Hurst parameter is not overall;(4) Given the average traffic arrival rate, as variance coefficient increases, queue length increases rapidly judging from the tail distribution, and packet loss probability becomes larger under a finite buffer size;(5) Adopting different relay transmission strategies can not change but only amplify the performance differences under these two traffic inputs. © 2010 IEEE.

关键词： Network performance

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Performance analysis of physical downlink and uplink channels in TD-LTE system

Performance analysis of physical downlink and uplink channel...

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2010 IEEE 12th International Conference on communication Technology, ICCT'2010

作者： Wu, Muzi Peng, Yuexing Yang, Xiao Zhang, Xiaofeng Wang, Wenbo Wireless Signal Processing and Network Lab. Key Lab. of Universal Wireless Communication Beijing University of Posts and Telecommunications Beijing China

ISBN: (纸本)9781424468690

TD-LTE as the evolution of TD-SCDMA is designed to support high data rates and reduced radio link delays. To reach these goals, new air interface is specified for TD-LTE. In this paper, the performance of physical uplink and downlink channels are evaluated by means of numerical simulations. Since the deployment of smart antennas is the unique feature of TD-SCDMA, special attentions are paid to the case of TD-LTE with dual-polarized smart antennas scheme, which can greatly facilitate practical application by smaller antenna array size and better stability relative to traditional mono-polarized smart antennas. The error performance is simulated for multiple physical channels with both mono- and dual-polarized smart antennas, and the simulation results on link level show that the dual-polarization scheme pays slight penalty of signal-to-noise ratio (SNR) loss, but brings significant benefits to practical application. It is intensively recommended to deploy the dual-polarized smart antennas in TD-LTE. © 2010 IEEE.

关键词： Radio links

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