Showing papers by "Beijing University of Posts and Telecommunications published in 2007"

Cryptanalysis of the Hillery-Bužek-Berthiaume quantum secret-sharing protocol

Abstract: The participant attack is the most serious threat for quantum secret-sharing protocols. We present a method to analyze the security of quantum secret-sharing protocols against this kind of attack taking the scheme of Hillery, Buzek, and Berthiaume (HBB) [Phys. Rev. A 59 1829 (1999)] as an example. By distinguishing between two mixed states, we derive the necessary and sufficient conditions under which a dishonest participant can attain all the information without introducing any error, which shows that the HBB protocol is insecure against dishonest participants. It is easy to verify that the attack scheme of Karlsson, Koashi, and Imoto [Phys. Rev. A 59, 162 (1999)] is a special example of our results. To demonstrate our results further, we construct an explicit attack scheme according to the necessary and sufficient conditions. Our work completes the security analysis of the HBB protocol, and the method presented may be useful for the analysis of other similar protocols.

A simple participant attack on the brádler-dušek protocol

Abstract: The ring-arrangement quantum secret sharing protocol in the paper [K. Bradler and M. Dusek (2004) J. Opt. B: Quantum Semiclass. Opt. 6 63] is analyzed and it is shown that this protocol is secure for any eavesdropper except for a dishonest participant. For example, by a special strategy, Bob can steal Charlie's portion of information without being detected and then recover Alice's secret by himself. We give a description of this strategy and point out a possible way to improve the protocol to stand against this attack.

Community detection in large-scale social networks

Abstract: Recent years have seen that WWW is becoming a flourishing social media which enables individuals to easily share opinions, experiences and expertise at the push of a single button. With the pervasive usage of instant messaging systems and the fundamental shift in the ease of publishing content, social network researchers and graph theory researchers are now concerned with inferring community structures by analyzing the linkage patterns among individuals and web pages. Although the investigation of community structures has motivated many diverse algorithms, most of them are unsuitable for large-scale social networks because of the computational cost. Moreover, in addition to identify the possible community structures, how to define and explain the discovered communities is also significant in many practical scenarios.In this paper, we present the algorithm ComTector(Community DeTector) which is more efficient for the community detection in large-scale social networks based on the nature of overlapping communities in the real world. This algorithm does not require any priori knowledge about the number or the original division of the communities. Because real networks are often large sparse graphs, its running time is thus O(C × Tri2), where C is the number of the detected communities and Tri is the number of the triangles in the given network for the worst case. Then we propose a general naming method by combining the topological information with the entity attributes to define the discovered communities. With respected to practical applications, ComTector is challenged with several real life networks including the Zachary Karate Club, American College Football, Scientific Collaboration, and Telecommunications Call networks. Experimental results show that this algorithm can extract meaningful communities that are agreed with both of the objective facts and our intuitions.

Principle and Performance of Semi-Persistent Scheduling for VoIP in LTE System

Abstract: This paper presents an effective scheduling scheme called semi-persistent scheduling for VoIP service in LTE system. The main challenges of effectively supporting VoIP service in LTE system are 1) the tight delay requirement combined with the frequent arrival of small packets of VoIP traffic and 2) the scarcity of radio resources along with control channel restriction in LTE system. Simulation results show that semi-persistent scheduling can support high system capacity while at the same time guaranteeing the QoS requirements such as packet delay and packet loss rate of VoIP. Furthermore, semi- persistent scheduling requires less control signaling overhead which is very important for efficient resources utilization in a practical system.

A Novel Multi-Cell OFDMA System Structure using Fractional Frequency Reuse

Abstract: In this paper, we propose a novel frequency reuse scheme for multi-cell orthogonal frequency division multiplexing access (OFDMA) systems for co-channel interference reduction. Each cell is partitioned into three sectors. All the available subcarriers are divided into two groups. One is reused in the central region of the sectors, and another is divided into three parts used orthogonally for the edge of the three sectors (no overlap). Which subcarrier group a user can use is dependent on the location or the received signal to interference plus noise ratio (SINR) of the user. Thus, intra-cell orthogonality is guaranteed, and inter-cell interference can be greatly reduced. All the subcarriers may use the same transmit power in this scheme. Simulation results show that this scheme can bring higher system throughput and lower CCI, and it also can increase the data rate at the cell edge.

Mobile Wireless Sensor Network: Architecture and Enabling Technologies for Ubiquitous Computing

Abstract: A mobile wireless sensor network owes its name to the presence of mobile sink or sensor nodes within the network. The advantages of mobile WSN over static WSN are better energy efficiency, improved coverage, enhanced target tracking and superior channel capacity. In this paper we present and discuss hierarchical multi-tiered architecture for mobile wireless sensor network. This architecture is proposed for the future pervasive computing age. We also elaborate on the impact of mobility on different performance metrics in mobile WSN. A study of some of the possible application scenarios for pervasive computing involving mobile WSN is also presented. These application scenarios will be discussed in their implementation context. While discussing the possible applications, we also study related technologies that appear promising to be integrated with mobile WSN in the ubiquitous computing. With an enormous growth in number of cellular subscribers, we therefore place the mobile phone as the key element in future ubiquitous wireless networks. With the powerful computing, communicating and storage capacities of these mobile devices, the network performance can benefit from the architecture in terms of scalability, energy efficiency and packet delay, etc.

Fiber Dispersion Influence on Transmission of the Optical Millimeter-Waves Generated Using LN-MZM Intensity Modulation

Abstract: We have theoretically investigated the transmission performance of the optical millimeter-waves (mm-waves) generated using intensity modulation via a Mach-Zehnder modulator, with the double and single sidebands (DSB and SSB) and optical carrier suppression (OCS) schemes. According to our theoretical analysis, fiber chromatic dispersion leads to fading effect and time shifting of the codes; therefore, signals are greatly degraded. Of all signals, DSB optical mm-wave suffers from both the fading effect and the time shifting of the codes. However, the optical mm-waves generated by SSB and OCS schemes are immune to the fading effect, while the time shifting of the codes limits their transmission distance. Experimental and simulation results confirm the theoretical analysis.

On the non-planar dust-ion-acoustic waves in cosmic dusty plasmas with transverse perturbations

Abstract: Dust-ion-acoustic waves in a cosmic dusty plasma is investigated, in spherical geometry with both azimuthal and zenith perturbations existing. (3+1)-dimensional spherical Kadomtsev-Petviashvili ((3+1)DsKP) model is constructed with symbolic computation, 4th-ordered and with variable coefficients. Auto-Backlund transformation and (3+1)DsKP nebulons are analytically obtained for such a generic model. Astromechanical and physical implications are discussed, of the supernova-shell-type expanding bright and Saturn-F-ring-type expanding dark (3+1)DsKP nebulons. Possibly observable nebulonic effects are proposed for future cosmic experiments.

Automatic Extraction of Power Lines From Aerial Images

Abstract: There has been little investigation for the automatic extraction of power lines from aerial images due to the low resolution of aerial images in the past decades. With increasing aerial photogrammetric technology and sensor technology, it is possible for photogrammetrists to monitor the status of power lines. This letter analyzes the property of imaged power lines and presents an algorithm to automatically extract the power line from aerial images acquired by an aerial digital camera onboard a helicopter. This algorithm first uses a Radon transform to extract line segments of the power line, then uses the grouping method to link each segment, and finally applies the Kalman filter technology to connect the segments into an entire line. We compared our algorithm with the line mask detector method and the ratio line detector, and evaluated their performances. The experimental results demonstrated that our algorithm can successfully extract the power lines from aerial images regardless of background complexity. This presented method has successfully been applied in China National 863 project for power line surveillance, 3-D reconstruction, and modeling.

Power Allocation and Subcarrier Pairing Algorithm for Regenerative OFDM Relay System

Abstract: Relayed transmission is a promising technique that helps in attaining broader coverage and in combating the impairment of the wireless channel. Orthogonal frequency division multiplexing (OFDM) technique is promising for the next generation wireless communication system. Therefore, the combination of two techniques named OFDM-relay will be a good candidate technology for future wideband wireless communication. This paper investigates the resource allocation of two-hop regenerative OFDM relay system with/without diversity. Optimization of power allocation (PA) is proposed to maximize the channel capacity and subcarrier pairing strategy is adopted to improve the system performance further. In addition, the resource allocation for multi-hop OFDM system without diversity is also presented. The resource allocation is based on the instantaneous channel state information (ICSI) and aims to maximize the system capacity. The order pairing strategy is proved to be a good choice for multi-hop regenerative OFDM relay system without diversity. The simulation results show that combining with the pairing algorithm, efficient power allocation will greatly improve the system capacity.

Some problems of directional sensor networks

Abstract: Wireless sensor networks are often based on omni-sensing and communication models. In contrast, in this paper, we investigate sensor networks with directional sensing and communication capability. Due to the distinct characteristics and potential effects on coverage and connectivity of the network, novel analysis and solutions are demanded. Towards this end, this paper analyses deployment strategies for satisfying given coverage probability requirements with directional sensing models. Moreover, for sensors with directional communication model, we propose methods for checking and repairing the connectivity of the network. We design efficient protocols to implement our idea. A set of experiments are also performed to prove the effectiveness of our solution.

Optimal Power Control Under Interference Temperature Constraints in Cognitive Radio Network

Abstract: In cognitive radio network, the interference of the unlicensed users to the licensed users should be limited under interference temperature constraints. In this paper, the optimal power control scheme of a network is analyzed without interference temperature constraints firstly. Based on this, considering interference temperature constraints, the optimal power control in cognitive radio network is modeled as a concave minimization problem. Some useful properties of the power control optimization problem are exploited. According to these properties, an improved branch and bound algorithm which is more efficient than the general branch and bound algorithm is proposed for optimal power control optimization problem in cognitive radio network.

Optical soliton solutions for two coupled nonlinear Schrödinger systems via Darboux transformation

Abstract: In nonlinear optical fibers, the vector solitons can be governed by the systems of coupled nonlinear Schrodinger from polarized optical waves in an isotropic medium. Based on the Ablowitz–Kaup–Newell–Segur technology, the Darboux transformation method is successfully applied to two coupled nonlinear Schrodinger systems. With the help of symbolic computation, the bright vector one- and two-soliton solutions including one-peak and two-peak solitons are further constructed via the iterative algorithm of Darboux transformation. Through the figures for several sample solutions, the stable propagation and elastic collisions for these kinds of bright vector solitons are discussed and the possible applications are pointed out in optical communications and relevant optical experiments.In addition, the conserved quantities of such two systems, i.e., the energy, momentum and Hamiltonian, are also presented.

Interworking of Wimax and 3GPP networks based on IMS [IP Multimedia Systems (IMS) Infrastructure and Services]

Abstract: The 3GPP specifies the IP multimedia subsystem (IMS) to provide several kinds of multimedia services in UMTS Release 5 and later releases. Interworking at the service layer between 3GPP and Wimax networks requires interworking between IMS functionality. By studying several interconnection scenarios and the main functionality of IMS, this article analyzes how the interworking of 3GPP and Wimax networks can be performed to support different levels of service interconnection. Special attention is paid to the interconnection at the session negotiation level, using SIP (the base protocol of the IMS), COPS/Go, and diameter protocols/interface to provide session negotiation with QoS and AAA (authentication authorization accounting) support

Quasi-secure quantum dialogue using single photons

Abstract: A quasi-secure quantum dialogue protocol using single photons was proposed. Different from the previous entanglement-based protocols, the present protocol uses batches of single photons which run back and forth between the two parties. A round run for each photon makes the two parties each obtain a classical bit of information. So the efficiency of information transmission can be increased. The present scheme is practical and well within the present-day technology.

Keyword Extraction Based on PageRank

Abstract: Keywords are viewed as the words that represent the topic and the content of the whole text. Keyword extraction is an important technology in many areas of document processing, such as text clustering, text summarization, and text retrieval. This paper provides a keyword extraction algorithm based on WordNet and PageRank. Firstly, a text is represented as a rough undirected weighted semantic graph with WordNet, which defines synsets as vertices and relations of vertices as edges, and assigns the weight of edges with the relatedness of connected synsets. Then we apply UW-PageRank in the rough graph to do word sense disambiguation, prune the graph, and finally apply UW-PageRank again on the pruned graph to extract keywords. The experimental results show our algorithm is practical and effective.

Comment on “Multiparty quantum secret sharing of classical messages based on entanglement swapping”

Abstract: In a recent paper [Z. J. Zhang and Z. X. Man, Phys. Rev. A 72, 022303 (2005)], a multiparty quantum secret sharing protocol based on entanglement swapping was presented. However, as we show, this protocol is insecure in the sense that an unauthorized agent group can recover the secret from the dealer. Hence we propose an improved version of this protocol which can stand against this kind of attack.

Fuzzy Logic Based Congestion Estimation for QoS in Wireless Sensor Network

Abstract: In this paper, we present a model for fuzzy logic based congestion estimation within a proposed QoS architecture. The architecture comprises of a QoS management and control module which is implemented both at node level and at the sink for a system level QoS administration. The QoS module implemented at sensor node forms a subset of the larger QoS Management and Control module implemented for the system wide information, so as not to encumber the resource constrained wireless sensor network While much research has been conducted in wireless sensor network, little attention has been given to a holistic QoS approach for WSN. Energy efficiency has been the main QoS metric in research efforts. In this paper, we present a congestion estimation model for QoS in wireless sensor network, and implement it using fuzzy logic with fuzzy set variables. Simulations are conducted for our scheme which shows that with increased network dynamics and with increased packets generation rate, our implementation efficiently sorts out the traffic and minimizes the packet loss for prioritized event-driven traffic.

A Cross-layer Packet Scheduling and Subchannel Allocation Scheme in 802.16e OFDMA System

Abstract: The IEEE 802.16e standard is a rapidly developing technology for broadband wireless access system. Its PHY OFDMA mode defines two subchannel building methods: diversity permutation and contiguous permutation (AMC subchannel). In this paper we propose a joint packet scheduling and subchannel allocation scheme applicable for the IEEE 802.16e OFDMA AMC subchannel. Since it is a multiuser, multi-service and multichannel packet-switched system, we define a distinct scheduling priority for each packet on each subchannel that integrates MAC QoS requirements, service type and PHY channel state information (CSI). Based on these scheduling priorities and specific scheduling mechanism, efficient QoS guaranteed resource allocation is achieved in our scheme. Intensive simulations show that our scheme outperforms throughput-oriented maximum C/I (MCI) and QoS-oriented priority schemes under various conditions.