HU Tian; ZHAO Bao-hua
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0001-04
Abstract ( 2285 ) PDF (197 KB)( 395 )
In wireless Ad-hoc networks, where mobile hosts are powered by batteries, the entire network may be partitioned because of the drainage of a small set of batteries. Therefore, the crucial issue is to improve the energy efficiency, with an objective of balancing energy consumption. A greedy algorithm called weighted minimum spanning tree (WMST) has been proposed, in which time complexity is . This algorithm takes into account the initial energy of each node and energy consumption of each communication. Simulation has demonstrated that the performance of the proposed algorithm improves the load balance and prolongs the lifetime.
YANG Bin; GONG Ping; LI Yong-hua; WU Wei-ling
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0005-05
Abstract ( 2565 ) PDF (209 KB)( 387 )
This article proposes a spatial multiplexing and diversity joint transmit structure for multiple input multiple output (MIMO)  orthogonal frequency division multiplexing (OFDM) system. The structure uses space-frequency block coding (SFBC) over all its spatial multiplexing layers to obtain both space diversity and frequency diversity gain. The article derives a monte carlo probabilistic data association (PDA) detector to obtain a better bit error rate (BER) performance when compared to the generic PDA detector. Computer simulation results show that the proposed detector can reduce the inter-symbol interference (ISI) greatly, improve the system performance significantly, and lower the computation complexity to a proper lever.
WANG Ying; SHEN Xiao-dong; WU Tong; LIU Bao-ling
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0010-06
Abstract ( 2582 ) PDF (385 KB)( 422 )
Introducing multiple-input multiple-output (MIMO) relay channel could offer significant capacity gain. And it is of great importance to develop effective power allocation strategies to achieve power efficiency and improve channel capacity in amplify-and-forward relay system. This article investigates a two-hop MIMO relay system with multiple antennas in relay node (RN) and receiver (RX). Maximizing capacity with antenna selection (MCAS) and maximizing capacity with eigen-decomposition (MCED) schemes are proposed to efficiently allocate power among antennas in RN under first and second hop limited scenarios. The analysis and simulation results show that both MCED and MCAS can improve the channel capacity compared with uniform power allocation (UPA) scheme in most of the studied areas. The MCAS bears comparison with MCED with an acceptable capacity loss, but lowers the complexity by saving channel state information (CSI) feedback to the transmitter (TX). Moreover, when the RN is close to RX, the performance of UPA is also close to the upper bound as the performance of first hop is limited.
YANG Fan; LI Dao-ben
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0016-06
Abstract ( 2432 ) PDF (290 KB)( 393 )
A more accurate correlated multiple input and multiple output (MIMO) channel model for IEEE 802.16n is presented. On one hand, this MIMO channel model can obtain more precise antenna correlation, which is a key character for MIMO channel and important for the research of IEEE 802.16n and MIMO technologies. On the other hand, it maintains a low complexity of simulation.
WANG Kun;PENG Mu-gen; WANG Wen-bo
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0022-06
Abstract ( 2312 ) PDF (357 KB)( 478 )
The scheduling algorithm based on the three-way handshaking scheme in IEEE 802.16d-2004 standard has some serious problems because of the complexity of the algorithm and low scheduling efficiency. To enhance the scheduling efficiency and improve the performance of multi-hop wireless mesh networks (WMNs), one distributed scheduling algorithm that can maximize the spatial and time reuse with an interference-based network model is proposed. Compared to the graph-based network model, the proposed network model can achieve a better throughput performance with maximal spatial reuse. Furthermore, this proposed scheduling algorithm also keeps fairly scheduling to all links, with a priority-based polling policy. Both the theoretical analysis and simulation results show that this proposed distributed scheduling algorithm is simple and efficient.
MA Peng-fei; ZHENG Kan; WANG Wen-bo
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0028-06
Abstract ( 2734 ) PDF (277 KB)( 466 )
In this article, a method based on max signal interference noise ratio (SINR) criterion is proposed, to mitigate the interuser interference for downlink multiuser spatial multiplexing multi-input multi-output (MIMO) systems. Unlike the zero forcing (ZF) scheme in which the SNR is decreased when the interference is eliminated completely, max SINR method makes a compromise between noise and interuser interference. When the number of substreams is larger than the difference between the number of base station antennas and the sum of interference mobile station antennas, the ZF is infeasible. An existing coordinated TX-RX block diagonalization (COOR BD) method uses preprocessing at the receiver to cancel the interuser interference. However, it cannot obtain more receive diversity gain because of the preprocessing. Analysis and simulation show that the max SINR scheme has better performance than the ZF method. Moreover, when the ZF is infeasible, the max SINR scheme can obtain more receive diversity gain than COOR BD in the two-user case.
WU Ping, LI Li-hua, ZHANG Ping
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0034-04
Abstract ( 2532 ) PDF (197 KB)( 371 )
For singular value decomposition (SVD)-based multiple input multiple output (MIMO) systems, implicit channel state information (CSI) incurs interferences amongst sub-channels if the CSI at the transmitter is not explicit. An improved SVD-based MIMO which can fully cancel the inter sub-channel interferences by reconstructing the transmitter- receiver system matrix on interferences analysis is provided. Simulation results indicate that the proposed algorithm outperforms the traditional SVD-based MIMO in a large degree.
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0038-05
Abstract ( 2327 ) PDF (233 KB)( 494 )
A user pairing method is proposed to improve the throughput gain of virtual multiple input multiple output (virtual MIMO) in 3G long-term evolution (LTE). The approach taken in this study separated the user pairing into four steps: 1) the users are divided into two groups according to their signal-to-noise ratio (SNR), and different user pairing metrics are proposed for each group; 2) the scheduler chooses a user for transmitting by a given rule; 3) the scheduler searches the pairing candidate for the selected user in each group; 4) the scheduler chooses the final pairing user from the co-group and crossover-group candidates by using a marginal utility function, to balance fairness and efficiency. The method can improve the throughput of users with high SNR, and guarantee fairness for users with low SNR, so it can be used in 3G LTE systems. The article provides both theoretical analysis and simulation results to support the idea.
JIA Peng;ZHANG Jie;GU Wan-yi
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0043-05
Abstract ( 2337 ) PDF (267 KB)( 372 )
The emergence of new services demands multicast function in optical network. Because of the high cost and complex architecture of multicast capable (MC) node, splitter- sharing switch structure is introduced in which the light splitters are shared by all input signals. To accommodate to this situation, by extending resource ReSerVation protocol-traffic engineering (RSVP-TE) and open shortest path first-traffic engineering (OSPF-TE), a new optical multicast mechanism is provided and the signaling flow and its finite state machine model are given. At the same time, a multicast routing algorithm in splitter-sharing optical network and a changing link weight policy to balance network traffic are proposed. Simulations in NSFNET show no matter with or without wavelength converters, when the number of splitters is 25% of that demanded by traditional MC nodes, the multicast performance has been close to the ideal circumstance. Wavelength converters and changing link weight help much in improving the traffic performance when the number of splitters is adequate.
ZHANG Yong-jing; LIN Yue-wei
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0048-08
Abstract ( 2282 ) PDF (334 KB)( 449 )
This article addresses the autonomy of joint radio resource management (JRRM) between heterogeneous radio access technologies (RATs) owned by multiple operators. By modeling the inter-operator competition as a general-sum Markov game, correlated-Q learning (CE-Q) is introduced to generate the operators’ pricing and admission policies at the correlated equilibrium autonomically. The heterogeneity in terms of coverage, service suitability, and cell capacity amongst different RATs are considered in the input state space, which is generalized using multi-layer feed-forward neural networks for less memory requirement. Simulation results indicate that the proposed algorithm can produce rational JRRM polices for each network under different load conditions through the autonomic learning process. Such policies guide the traffic toward an optimized distribution and improved resource utilization, which results in the highest network profits and lowest blocking probability compared to other self-learning algorithms.
CHEN Jie; ZHANG Ping
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0056-07
Abstract ( 2215 ) PDF (310 KB)( 373 )
Bargaining based mechanism for sharing spectrum between radio access networks (RANs) belonging to multi- operators is studied, to improve spectrum utilization efficiency and maximize network revenue. By introducing an intelligent agent, each RAN has the ability, which includes trading information exchanging, final decision making, and so on, to trade the spectrum with other RANs. The proposed inter-operator spectrum sharing mechanism is modeled as an infinite-horizon bargaining game with incomplete information, and the resulting bargaining game has unique sequential equilibrium. Consequently, the implementation is refined based on the analysis. Simulation results show that the proposed mechanism outperforms the conventional fixed spectrum management (FSM) method in network revenue, spectrum efficiency, and call blocking rate.
FANG Xi; WANG Jun; WANG Yong; JIANG Feng
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0063-07
Abstract ( 2196 ) PDF (220 KB)( 370 )
Owing to limited bandwidth, high bit error rate, and bursty error in the wireless environment, the performance of the transmission control protocol (TCP) degrades greatly in wireless networks. Up to now, many researchers have contributed greatly to the wireless TCP field. However, in most of their works, the wireless TCP module usually works in the TCP layer and has no idea of the actual time of the packet transmission, which is determined by the Scheduler in the media access control (MAC) layer, and this will bring the inaccuracy to the local retransmission timeout and induce the redundant local retransmission. In this article, a coordinator is introduced into the base-station (BS), which can provide efficient cooperation between the TCP module and the scheduler module. On the bais of the performance analysis and simulation results, the proposed method is shown to eliminate redundant local retransmission, increase throughput, and improve TCP-level fairness in wireless networks. Moreover, this scheme is orthogonal to those existing wireless TCP schemes, thus it can give great compatibility to the current networks, and further enhance the performance of TCP under the condition that the performance improvement benefiting from the existing approaches will not be affected.
WANG Xian-qing; LU Yue-ming; JI Yue-feng
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0070-04
Abstract ( 2218 ) PDF (184 KB)( 359 )
Risk-disjoint routing is an efficient way to improve network survivability. In this article, a partial risk-disjoint routing algorithm based on link availability (PRDRA-LA) is proposed based on the complete risk-disjoint routing algorithm (CRDRA). While calculating the protection path with PRDRA-LA, the links that share risks with the links in the working path are filtered by link availability. In addition, the risk disjoint degree between the protection path and the working path can be adjusted freely. Simulation results showed that when compared with CRDRA, routing connections with PRDRA-LA can achieve improved survivability while the number of connections that can be successfully routed over the current network is kept from serious decline.
XIE Zheng-cheng; XING Jun-wei; WU Li; JI Yue-feng
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0074-05
Abstract ( 2204 ) PDF (178 KB)( 362 )
Pre-configured cycles (p-cycles) can attain high capacity efficiency and fast protection switching times in wavelength division multiplexing (WDM) networks. This article proposes the weighted straddling link algorithm (WSLA) for generating a subset of all cycles that can guarantee 100% restorability in case of dual link failure, and give an integer linear programming (ILP) formulation that solves the shared p-cycles design problem minimizing the total spare capacities. Numerical result shows that our method can achieve 100% dual link failure restorability with acceptable spare capacity. The larger standard deviation of demand set and the larger node degree network, the better the shared p-cycles scheme performs.
WANG Jian; LIU Yan-heng; TIAN Da-xin; WEI Da
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0079-06
Abstract ( 2293 ) PDF (266 KB)( 468 )
In recent years, fast spreading worm has become one of the major threats to the security of the Internet and has an increasingly fierce tendency. In view of the insufficiency that based on Kalman filter worm detection algorithm is sensitive to interval, this article presents a new data collection plan and an improved worm early detection method which has some deferent intervals according to the epidemic worm propagation model, then proposes a worm response mechanism for slowing the wide and fast worm propagation effectively. Simulation results show that our methods are able to detect worms accurately and early.
MING Yang; SHEN Xiao-qin; WANG Yu-min
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0085-06
Abstract ( 2331 ) PDF (228 KB)( 418 )
Universal designated verifier signature schemes allows a signature holder to designate the signature to a desire designated verifier, in such a way that only designated verifier can verify this signature, but is unable to convince anyone else of this fact. The previous constructions of universal designated verifier signature rely on the underlying public key infrastructure, that needs both signers and verifiers to verify the authenticity of the public keys, and hence, the certificates are required. This article presents the first model and construction of the certificateless universal designated verifier signature scheme, in which the certificates are not needed. The proposed scheme satisfies all the requirements of the universal designated verifier signature in the certificateless system. Security proofs are provided for the scheme based on the random oracle model, assuming that the Bilinear diffie-hellman (BDH) problem is hard to solve.
HU Lan-lan;NIU Xin-xin;YANG Yi-xian
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0091-04
Abstract ( 2469 ) PDF (216 KB)( 460 )
In 2005, Liu et al. proposed an improvement to Chien et al.’s remote user authentication scheme, using smart cards, to prevent parallel session attack. This article, however, will demonstrate that Liu et al.’s scheme is vulnerable to masquerading server attack and has the system’s secret key forward secrecy problem. Therefore, an improved scheme with better security strength, by using counters instead of timestamps, is proposed. The proposed scheme does not only achieve their scheme’s advantages, but also enhances its security by withstanding the weaknesses just mentioned.
TANG Jing; SHEN Shu-qun
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0095-04
Abstract ( 2227 ) PDF (239 KB)( 388 )
The influence of phase noise (PN) present at the access point (AP) and mobile terminator (MT) may degrade the performance in orthogonal frequency division multiplexing (OFDM) system, because the OFDM system is sensitive to the PN. The method of PN approximation based on the PN power spectrum was proposed to combat the influence of the PN present. The idea of the PN cancellation is the PN is approximated for the sum of the different frequency between the AP and the MT as well as Doppler shift supposing that the fixed different frequency during several OFDM symbols are identical, so the variable phase may be considered as the combination of the fixed partition and the random partition. The approximation method is utilized to remove the fixed and the random phase partition so that the signal-to-noise ratio (SNR) may be improved. The analysis and the simulation proposed show that the method may effectively improve the performance of the OFDM system.
YANG Bing; YU He; TAO Xiao-feng
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0099-04
Abstract ( 2243 ) PDF (152 KB)( 409 )
Automatic gain control (AGC) has an important role in multi-input multi-output–orthogonal frequency-division multiplexing (MIMO–OFDM) system, especially, when receiving antennas are distributed. In recent years, much work has been done on efficiency and simplification of AGC, but few of them are aiming at multiple antennas. This article, on the assumption of ideal AGC for single receiving antenna, analyzes feasible AGC methods for MIMO system from a new aspect, then brings forward three applicable AGC methods: separate automatic gain control, joint automatic gain control, and partly-joint automatic gain control (PJ-AGC). After simulation, when parameters are properly set, PJ-AGC has the best performance and can be applied to B3G MIMO–OFDM system.
DENG Zong-yuan; SHAO Xi; YANG Zhen
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0103-05
Abstract ( 2199 ) PDF (287 KB)( 376 )
Steganalysis can be used to classify an object whether or not it contains hidden information. In this article, is presented, a novel approach to detect the presence of least significant bit (LSB) steganographic messages in the voice secure communication system. A distance measure, which has proven to be sensitive to LSB steganography by analysis of variance (ANOVA), is denoted to estimate the difference between the host signal and the stego signal. Then an maximum likelihood (ML) decision is combined to form the classifier. Statistical experiments show that the proposed approach has a highly accurate rate and low computational complexity.
ZHANG Jian-yin; YANG Fang-chun; SU Sen
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0108-05
Abstract ( 2291 ) PDF (201 KB)( 505 )
As a platform-independent software system, a Web service is designed to offer interoperability among diverse and heterogeneous applications. With the introduction of service composition in the Web service creation, various message interactions among the atomic services result in a problem resembling the feature interaction problem in the telecommunication area. This article defines the problem as feature interaction in Web services and proposes a model checking-based detection method. In the method, the Web service description is translated to the Promela language – the input language of the model checker simple promela interpreter (SPIN), and the specific properties, expressed as linear temporal logic (LTL) formulas, are formulated according to our classifi- cation of feature interaction. Then, SPIN is used to check these specific properties to detect the feature interaction in Web services.
HAN Yu-nan;LV Ying-hua;ZHANG Hong-xin
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0113-04
Abstract ( 2270 ) PDF (330 KB)( 438 )
A 3-D impedance method has been introduced to compute the electric currents induced in a human body exposed to extremely low-frequency electromagnetic field. The 3-D impedance method has been deduced from Maxwell equations and is put into the computation and simulation effectively to the visible human body model, which has 196×114×626 cells and more than 40 types of tissues. As the result, two representative cases are investigated. One is exposure of the human body to 100 µT (1 000 mG), the limit recommended by the International Commission on Non-Ionizing Radiation Protection for the public and the other one is the exposure of human body to 0.4 µT (4 mG), the level at which a statistical link appears with a doubled risk of development of childhood leukaemia. The distribution of induced current density can be obtained and the maximum of induced current are found to be 16 mA/m2 and 0.07 mA/m2.
FU Si-bao; LV Ting-jie
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0117-06
Abstract ( 2420 ) PDF (284 KB)( 388 )
The market share between China Mobile and China Unicom has stabilized since 2002. It is found that China Mobile has the superiority in the competition, for example, the scissors movement between its revenue and cost indicates that it has a strong profit generating ability and there is enough room for it to reduce the price. The ratio between its price (marginal income) and marginal cost indicates that there is a very distant limit for it to reduce the price. Its demand is obviously flexible with the price, but it does not use the price weapon abundantly. The reason for the stabilization of the market is that China Mobile withdrew from the competition.
ZHANG Xiao-hang; LV Ting-jie; YANG Tian-jian
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (3). doi： 1005-8885 (2007) 03-0123-06
Abstract ( 2209 ) PDF (160 KB)( 400 )
The mobile operators are struggling for improving the market share and the revenues. One important method is to acquire the potential customers from the competitors. This article presents a whole acquisition process and an integrated framework for customer acquisition support system (CASS). The core of the system is the customer acquisition identification models which are built based on data mining technologies. The CASS can automate the acquisition process and decrease the cost and implement precise marketing strategy for mobile operators.