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International Conference on Communications Workshops

作者： Namei Yin Caili Guo Yang Yang Pengfei Luo Chunyan Feng Beijing Laboratory of Advanced Information Networks Beijing University of Posts and Telecommunications China Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications China Research Department of HiSilicon Huawei Technologies Co. Ltd Beijing China

ISBN: (纸本)9781509015269

In visible light communication (VLC) systems, optical orthogonal frequency division multiplexing (O-OFDM) is an appealing modulation. Among many proposed O-OFDM schemes, both direct current biased O-OFDM (DCO-OFDM) and asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) are widely used. Since VLC needs to take the dual requirements of illumination and communication into account, different dimming levels are often required. For high and low dimming level scenarios, system with ACO-OFDM normally has a better spectral efficiency performance than system with DCO-OFDM due to the smaller clipping noise. However, regarding the middle dimming level scenarios, the DCO-OFDM generally outperforms the ACO-OFDM. In order to improve system spectral efficiency within the wide dimming range, an asymmetrical and direct current biased optical orthogonal frequency division multiplexing (AAD-OFDM) is proposed in this paper. In AAD-OFDM based system, the modulation scheme is switched between ACO-OFDM and DCO-OFDM according to the required dimming level. Therefore, by adopting the proposed AAD-OFDM, the VLC system can fully utilize the dynamic range of LED at any dimming levels thus improving the performance. Simulation results show that the proposed scheme has high spectral efficiency within a wide dimming range.

关键词： Visible Light Communication

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Indoor Visible Light Localization Algorithm Based on Received Signal Strength Ratio with Multi-Directional LED Array

Indoor Visible Light Localization Algorithm Based on Receive...

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International Conference on Communications Workshops

作者： Lixuan Wang Caili Guo Pengfei Luo Qiang Li Beijing Laboratory of Advanced Information Networks Beijing University of Posts and Telecommunications China Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications China Research Department of HiSilicon Huawei Technologies Co. Ltd Beijing China

ISBN: (纸本)9781509015269

Visible light communication (VLC) based localization is a potential candidate for indoor localization. However, since the field of view (FOV) of the photodiode (PD) is normally narrow, the PD might not be capable to detect enough LEDs to perform the triangulation algorithm. Furthermore, high directionality is a significant character in VLC, and in practice, the direction of LED is commonly fixed and able to be known for once, but the direction of the PD is commonly random. In this paper, we exploit the direction of the LED in the lamp structure design and manage to mitigate the influence of the direction of the PD in the algorithm design. A localization algorithm based on received signal strength ratio (RSSR) with multi-directional LED array (MDLA) is proposed. In addition, we introduce the coverage ratio (CR) and the average angle acceptance ratio (AAAR) to evaluate the localization scheme's coverage in location and acceptance in direction, respectively. Simulation results show that when the tilt angle of LEDs is 15°, the proposed scheme can attain the root-mean-square error (RMSE) of 0.04 m and 0.06 m in 2-D and 3-D localization, respectively, and it is more probably for it to obtain enough lamps compared to the conventional scheme using the triangulation algorithm with the lamp structure of a single LED.

关键词： candidate indoor localization

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An effective visual saliency detection method based on maximum entropy random walk

An effective visual saliency detection method based on maxim...

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2016 IEEE International Conference on Multimedia and Expo Workshop, ICMEW 2016

作者： Lu, Jingyu Wen, Xiangming Hua, Shao Lu, Zhaoming Chen, Yawen Beijing Laboratory of Advanced Information Networks Beijing Key Laboratory of Network System Architecture and Convergence School of Information and Communication Engineering Beijing University of Posts and Telecommunications 100876 China

ISBN: (纸本)9781509015528

Visual saliency detection (VSD) has been attracting increasing attention due to its wide applications in computer visions. In this paper, a visual saliency detection method based on maximum entropy random walk (MEVSD) is proposed. Gaze wandering over images is modeled as a random walk process on a graph, in which the super-pixels and their similarities are regarded as nodes and edges respectively. The visual salient region is detected based on the stationary distribution of the stochastic process. Compared with the stat-of-the-art methods, MEVSD focuses on globally maximizing the entropy of walking trajectories. A two-tier neighbor scheme of super-pixels is proposed to reduce the computational complexity. Besides, a belief diffusion algorithm on weight matrix is proposed to improve precision rate. Extensive experiments with diverse content of pictures indicate that MEVSD performs well compared with 11 state-of-the-art methods. © 2016 IEEE.

关键词： Random processes

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Joint remote radio head activation and beamforming for energy efficient C-RAN 13

Joint remote radio head activation and beamforming for energ...

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13th International Symposium on Wireless Communication systems, ISWCS 2016

作者： Yan, Zeng Wen, Xiangming Lu, Zhaoming Chen, Yawen Shao, Hua Beijing Laboratory of Advanced Information Networks Beijing Advanced Innovation Center for Future Internet Technology Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications Beijing100876 China

ISBN: (纸本)9781509020614

The cloud radio access network (C-RAN) has emerged as a promising architecture to provide extremely high throughput with fantastic energy efficiency (EE) performance. However, as all the RRHs need to be connected to the baseband unit pool (BBU) through transport links, the transmit power consumption becomes significant, which result in the demands of new researches in energy efficiency optimization. In this paper, we focus on the dynamic remote radio head (RRH) activation and network EE optimization in order to fully reap the benefits brought by Green C-RAN. First, an EE optimization problem that jointly considers RRH activation and group sparse beamforming is formulated, which is hard to solve due to its non-convexity nature. Thus, we utilize the weighted minimal mean square error (WMMSE) method to transfer the non-convex EE problem into a concave-convex fractional program problem. And the Lagrangian theory is exploited to assist the problem analysis and algorithm design. Specifically, the weighted group sparse beamforming algorithm is proposed. In this algorithm, we adopt the mixed l1=lp-norm to induce group sparsity in the beamformers, which corresponds to switching off RRHs. Simulation results will show that the proposed algorithm can significantly improve the EE for C-RAN. © 2016 IEEE.

关键词： Energy efficiency

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A fair listen-before-talk mechanism for LTE-U using a coalition formation approach 13

A fair listen-before-talk mechanism for LTE-U using a coalit...

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13th International Symposium on Wireless Communication systems, ISWCS 2016

作者： Wuqiong, Ding Wen, Xiangming Lu, Zhaoming Wenpeng, Jing Yan, Zeng Beijing Key Laboratory of Network System Architecture and Convergence Beijing Advanced Innovation Center for Future Internet Technology Beijing Laboratory of Advanced Information Networks Beijing University of Posts and Telecommunications Beijing100876 China

ISBN: (纸本)9781509020614

LTE on unlicensed bands (LTE-U), which is a promising way to meet the increasing mobile data demand, has attracted world-wide interests. However, the fair coexistence of LTE-U and WLAN is a critical issue to be solved. In this paper, we devise a semi-distributed channel access approach for LTE-U in dense deployed scenario to improve its capacity and achieve fair coexistence with WLAN. Specifically, the basic listen-before-talk (LBT) mechanism is employed to guarantee the fairness for WLAN, which is similar with the medium control access (MAC) protocol of WLAN. However, in order to decrease the high collision probability at heavy traffic load, a coalition strategy is introduced, in which the LTE-U base stations (BSs) would form into groups, and each group would contend for accessing the channel as one entity. This will effectively reduce the number of stations contending for accessing the channel and the collision probability as a result. In particular, in order to obtain the coalition solution, the cooperative game theory is introduced, and a low-complexity coalition formation algorithm is proposed based on the concept of recursive core in cooperative game. Simulation results verify the effectiveness of the proposed channel access approach, especially improving the LTE-U capacity and ensuring the fairness between LTE-U and WLAN. © 2016 IEEE.

关键词： Medium access control

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Modelling and Forecasting of Commodity Trading Price

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Journal of Physics: Conference Series 2018年第1期1060卷

作者： Jun Liu Yuan Tian Qing Yan Center for Data Science BUPT Beijing 100876 China. School of Information and Communication Engineering BUPT Beijing 100876 China. Beijing Laboratory of Advanced Information Networks BUPT Beijing 100876 China. Beijing Key Laboratory of Network System Architecture and Convergence BUPT Beijing 100876 China.

This paper proposes and improves a model for China's cotton reserves trading market, generates a more accurate price level table in contrast to the widely used China Cotton Association(CCA)'s table, and predicts the future trading price with this model. Data used is all 29895 trade records of cotton reserves from May, 2016 to Sept, 2016. In this paper, we firstly give a briefly introduction to the data as well as basic knowledge of cotton, especially the CCA's price level table as the target to improve accuracy. We then present a multiple linear regression with dummy variable model, which can reduce the error on predicting the trading price of current month, but still remains some problems such as the result shows a batch of cotton with better quality may get a lower price. So we finally advance the model with multidimensional isotonic regression and more factors taken into consideration. Our last model could be used to predict the trade price of both current month and next month with approximately 4% mean absolute percentage error(MAPE).

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A modified Matérn hard core point process for modeling and analysis of dense IEEE 802.11 networks 13

A modified Matérn hard core point process for modeling and ...

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13th International Symposium on Wireless Communication systems, ISWCS 2016

作者： Tao, Lei Wen, Xiangming Lu, Zhaoming Jing, Wenpeng Chen, Kun Zhao, Xiaoguang Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications Beijing China Beijing Laboratory of Advanced Information Networks Beijing China Beijing Advanced Innovation Center for Future Internet Technology China

ISBN: (纸本)9781509020614

Stochastic geometry is a powerful tool for modeling wireless networks employing various MAC protocols with random topologies. For wireless networks operating carrier sense multiple access/collision avoidance (CSMA/CA) protocol, there are distance constraints between simultaneous transmitters, and only one node is allowed to transmit within its carrier sensing range. Matérn hard core point process is generally used to model and analyze the performance of this type of networks, because it is a repulsive point process that also defines a minimum distance between any two points. However, the traditional Matérn HCPP has the defect of underestimating the intensity of concurrent transmission nodes, which will affect the accuracy of analysis results, when wireless nodes are densely deployed. In this paper, we propose a modified Matérn HCPP called TM-HCPP which can mitigate the intensity underestimation problem to model dense IEEE 802.11 networks. Then, we simulate the network coverage probability using the traditional Matérn HCPP and the proposed TM-HCPP, and compare the simulated results with the theoretical analyzed results. Simulation results validate the accuracy of the proposed TM-HCPP. © 2016 IEEE.

关键词： Wireless networks

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Handoff management scheme based on frame loss rate and RSSI prediction for IEEE 802.11 networks 13

Handoff management scheme based on frame loss rate and RSSI ...

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13th International Symposium on Wireless Communication systems, ISWCS 2016

作者： Tao, Lei Wen, Xiangming Lu, Zhaoming Wenpeng, Jing Biao, Zhang Gang, Cao Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications Beijing China Beijing Laboratory of Advanced Information Networks Beijing China Beijing Advanced Innovation Center for Future Internet Technology China

ISBN: (纸本)9781509020614

This paper proposes a frame loss rate (FLR) and received signal strength indicator (RSSI) prediction based handoff management scheme to reduce the ping-pong effect caused by the purely RSSI based handoff decision schemes in IEEE 802.11 networks. The proposed scheme is performed by each mobile station (MS) in a decentralized manner. In the proposed scheme, the FLR information is used as handoff trigger criterion. To perceive the change trends of wireless link thus reducing the target AP selection time, the proposed scheme adopts polynomial regression-based RSSI prediction approach. The predicted RSSI together with FLR information is used for target access point (AP) selection. Moreover, we construct neighboring AP information list (NAIL) for MSs to store the above information. Therefore, the proposed scheme can also be called NAIL-based handoff management scheme. The results indicate that the proposed scheme can effectively reduce the invalid handoffs and avoid the ping-pong effect. © 2016 IEEE.

关键词： Forecasting

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Oscillation resolution for massive cell phone traffic data 1

Oscillation resolution for massive cell phone traffic data

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1st Workshop on Mobile Data, MobiData 2016, co-located with MobiSys 2016

作者： Qi, Ling Qiao, Yuanyuan Abdesslem, Fehmi Ben Ma, Zhanyu Yang, Jie Center for Data Science Beijing Key Laboratory of Network System Architecture and Convergence Beijing Laboratory of Advanced Information Network BUPT Beijing China Decisions Networks and Analytics Laboratory SICS Stockholm Sweden Center for Data Science Pattern Recognition and Intelligent System Lab BUPT Beijing China

ISBN: (纸本)9781450343275

Cellular towers capture logs of mobile subscribers whenever their devices connect to the network. When the logs show data traffic at a cell tower generated by a device, it reveals that this device is close to the tower. The logs can then be used to trace the locations of mobile subscribers for different applications, such as studying customer behaviour, improving location-based services, or helping urban planning. However, the logs often suffer from an oscillation phenomenon. Oscillations may happen when a device, even when not moving, does not only connect to the nearest cell tower, but is instead unpredictably switching between multiple cell towers because of random noise, load balancing, or simply dynamic changes in signal strength. Detecting and removing oscillations are a challenge when analyzing location data collected from the cellular network. In this paper, we propose an algorithm called SOL (Stable, Oscillation, Leap periods) aimed at discovering and reducing oscillations in the collected logs. We apply our algorithm on real datasets which contain about 18.9 TB of traffic logs generated by more than 3 million mobile subscribers covering about 21000 cell towers and collected during 27 days from both GSM and UMTS networks in northern China. Experimental results demonstrate the ability and effectiveness of SOL to reduce oscillations in cellular network logs. © 2016 ACM.

关键词： Location based services

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On stochastic geometry analysis of dense WLAN with dynamic carrier sense threshold and rate control

On stochastic geometry analysis of dense WLAN with dynamic c...

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International Symposium on Wireless Personal Multimedia Communications (WPMC)

作者： Xiaoguang Zhao Xiangming Wen Tao Lei Zhaoming Lu Biao Zhang Beijing Key Laboratory of Network System Architecture and Convergence Beijing Beijing Laboratory of Advanced Information Networks Beijing

ISBN: (纸本)9781509053773

Recently, wireless local area networks (WLANs) have been densely deployed. In high density WLANs, co-channel interference has become one of the biggest challenges for the network performance. The IEEE 802.11 based WLANs have limited wireless channels, therefore, not all the adjacent APs can work in different non-overlapping channels and co-channel interference will affect the network performance severely. To get better network performance, transmit power control scheme is used to reduce the co-channel interference from neighbour nodes. However, transmit power control scheme may cause asymmetric links, we propose a dynamic carrier sense and rate control (DCR) scheme to improve the network performance in dense WLANs. The DCR scheme mainly tunes the carrier sense threshold (CST) and rate for the edge stations (STAs). A stochastic geometry model is also demonstrated for the analysis of the network performance. The network performance is evaluated by the coverage probability. Then, we simulate the coverage probability of WLAN which uses the existing static carrier sense threshold scheme and the proposed DCR scheme. Simulation results show that the proposed DCR scheme yields better coverage probability compared with the existing static carrier sense threshold scheme.

关键词： Stochastic processes Geometry Wireless LAN IEEE 802.11 Standard Throughput Interchannel interference

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