WU Tong, QU Xin-chun, WANG Ying
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0001-06
Abstract ( 3422 ) PDF (379 KB)( 429 )
On the basis of the amplify-and-forward relaying mode, a two-hop distributed cooperative multi-relay system is proposed combining with the space-time block coding OFDM (STBC-OFDM) technique. Taking the maximum end-to-end data rate as optimization criterion, the signal-to-noise ratio (SNR) of receiving terminal is deduced. On the basis of the water-filling theory, the optimal power allocation (OPA) is achieved for each subcarrier in each antenna and each relay node (RN) of the two-hop, to realize the resource optimization. Monte Carlo method is adopted in simulation. The simulation results show that compared with the uniform resource allocation scheme, the proposed OPA strategy can improve the system capacity. And the energy consumption of each transmission bit will be decreased, indicating the improvement of resource efficiency. In the scenario that the total power is limited, the system performance can be enhanced further by the distributed cooperative multi-relay through the diversity gain.
MA Shu-hui; JI Hong;YUE Guang-xin
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0007-07
Abstract ( 2529 ) PDF (319 KB)( 374 )
A novel topology scheme, cell with multiple mobile sinks method (CMMSM), is proposed in this article for the collection of information and for the environment monitoring in wireless sensor networks. The system consists of many static sensors, scattered in a large scale sensing field and multiple mobile sinks, cruising among the clusters. Conservation of energy and simplification of protocol are important design considerations in this scheme. The noninterference topology scheme largely simplifies the full-distributed communication protocol with the ability of collision avoidance and random routing. The total number of cluster heads in such a topology was analyzed, and then an approximate evaluation of the total energy consumption in one round was carried out. Simulation results show that CMMSM can save considerable energy and obtain higher throughput than low-energy adaptive clustering hierarchy (LEACH) and geographical adaptive fidelity (GAF).
ZHAO Fa-yong;FENG Guang-zeng
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0019-04
Abstract ( 2929 ) PDF (199 KB)( 541 )
Multicarrier code division multiple access (MC-CDMA) has the ability to combat with frequency selective fading and antenna array can enhance the performance of system. The paper proposes a novel joint spatial-frequency blind multiuser detection for antenna array MC-CDMA based on linear constraint constant modulation algorithm (LCCMA), which has robust performance and can ensue the weight vectors to converge to that of the desired user. Simulation indicates the proposed algorithm has better bit error ratio (BER) performance than that of the traditional beamforming-based two-step algorithm.
ZENG Yi; ZHANG Zu-fan
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0014-05
Abstract ( 2769 ) PDF (304 KB)( 423 )
This study addresses the problem of jointly optimizing the transmit beamformers and power control in multi-user multiple-input multiple-output (MIMO) downlink. The objective is minimizing the total transmission power while satisfying the signal-to-noise plus interference ratio (SINR) requirement of each user. Before power control, it uses the maximum ratio transmission (MRT) scheme to determine the beamformers due to its attractive properties and the simplicity of handling. For power control it introduces a supermodular game approach and proposes an iterated strict dominance elimination algorithm. The algorithm is proved to converge to the Nash equilibrium. Simulation results indicate that this joint optimization method assures the improvement of performance.
ZHOU Ming-yu;LI Li-hua;JIANG Jun; ZHONG Ming-hua; TAO Xiao-feng
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0023-05
Abstract ( 3022 ) PDF (226 KB)( 393 )
This article proposes a simple pilot-aided channel estimation method based on correlation in time domain for multiple-input and multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. Pilot symbols in all transmit antennas are generated from different circular shifting of a certain sequence. Through once correlation, the receiver can obtain time-domain pulse responses for channel fading from all transmit antennas to a certain receive antenna, from which channel estimation in frequency domain can be obtained. Beyond 3G time-division duplex (B3G-TDD) uplink is introduced, and the channel estimation method is used in it. Theoretical analysis and simulation are both carried out. Mean square error (MSE) performance shows that the method can exhibit precise estimation. Complexity analysis proves it requires very low complexity. System simulation result shows that it guarantees the performance of B3G-TDD uplink very well.
ZHANG Yong, WEI Yi-fei, ZHANG Li-kun, SONG Jun-de
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0028-05
Abstract ( 2667 ) PDF (149 KB)( 519 )
Smart antenna technology is introduced to wireless mesh networks. Smart antennas based wider-range access medium access control (MAC) protocol (SWAMP) is used as MAC protocol for IEEE 802.11 mesh networks in this study. The calculation method of node throughput in chain and arbitrary topology is proposed under nodes fairness guarantee. Network scale and interference among nodes are key factors that influence node throughput. Node distribution pattern near the gateway also affects the node throughput. Experiment based on network simulator-2 (NS-2) simulation platform compares node throughput between smart antenna scenario and omni-antenna scenario. As smart antenna technology reduces the bottle collision domain, node throughput increases observably.
SU Huan;ZHANG Jian-hua
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0033-05
Abstract ( 3214 ) PDF (261 KB)( 536 )
This article presents downlink initial synchronization and cell identification algorithms for long term evolution (LTE) of third-generation (3G) mobile communication systems, which are based on synchronization channel (SCH) and cell specific pilot symbols, respectively. The key features of the proposed scheme are: it can improve performance of the frequency synchronization through oversampling of the SCH, it can support a large number of target cells by modulating a cell-specific pilot sequence over two symbols within a subframe, and it can guarantee cell identification performance by maximally ratio combining the frequency domain differential cross-correlation. Simulations show that the proposed scheme has a potential use in 3G LTE.
LIU Jun;CUI Qi-mei;TAO Xiao-feng
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0038-07
Abstract ( 2593 ) PDF (408 KB)( 455 )
This article presents an iterative algorithm for estimating the location of the destination mobile station (DS) when some extra mobile stations around the DS are involved in and assist the base stations to complete the localization process. The proposed method is based on the taylor-series (TS) method and jointly estimates both the DS and the extra mobile stations, named reference mobile station (RS) in this article, positions simultaneously. Moreover, the time-differential-of-arrival (TDOA) measurements between DS and pairs of RSs are obtained by ultra-wide-band (UWB) signal, which is adept in accurate ranging application. According to the theoretic analysis, the Cramér-Rao lower bound (CRLB) of the modified TS algorithm reduces significantly. The actual performance, under a given simulation scenario, is enhanced by 25% at best.
LI Xiao-hui; HAN Ming;YI Ke-chu;TIAN Bin
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0045-06
Abstract ( 2775 ) PDF (259 KB)( 478 )
According to the quality of service (QoS) requirements of differentiated service (DiffServ), a cross-layer resource allocation algorithm for multi-user orthogonal frequency division multiplexing（OFDM）systems is presented. The constant rate is maintained by adjusting the power dynamically for the voice traffics with high priority, whereas the fairness amongst the data traffics is guaranteed by weighted fairness queued (WFQ) algorithm. The two above-mentioned strategies are used for video traffics to realize variable data rate with the constraint of the minimum rate. Combing all these methods, both the throughput and the fairness are ensured when there are multiple users in the OFDM system. Simulation results indicate the validity of the proposed algorithm, which can work well even if the SNR is less than 0 dB.
WANG Qing-hua;QU Yu-gui; LIN Zhi-ting;BAI Rong-gang;ZHAO Bao-hua; PAN Quan-ke
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0051-07
Abstract ( 3088 ) PDF (238 KB)( 519 )
Wireless sensor networks (WSN) using cooperative multiple-input multiple-output (MIMO) communication are effective tools to collect data in several environments. However, how to apply cooperative MIMO in WSN remains a critical challenge, especially in sparse WSN. In this article, a novel clustering scheme is proposed for the application of cooperative MIMO in sparse WSN by extending the traditional low-energy adaptive clustering hierarchy (LEACH) protocol. This clustering scheme solves the problem that the cluster heads (CH) cannot find enough secondary cluster heads (SCH), which are used to cooperate and inform multiple-antenna transmitters with CHs. On the basis of this protocol, the overall energy consumption of the networks model is developed, and the optimal number of CHs is obtained. The simulation results show that this protocol is feasible for the sparse WSN. The simulation results also illustrate that this protocol provides significant energy efficiencies, even after allowing for additional overheads.
ZHANG Deng-yin;CHEN Jia-ping; SUN Jun-cai
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0058-06
Abstract ( 2634 ) PDF (472 KB)( 487 )
This article presents a watermarking algorithm based on one-dimensional (1-D) chaotic map in wavelet transform (WT) domain. Traditional encryption and watermarking technologies in the WT domain are combined in this algorithm. First, the watermark is encoded by a chaotic sequence, which is generated by a key. On the basis of human visual system (HVS), it is then divided into two parts and embedded into the low- and intermediate-frequency bands of three-layer WT domain. The encryption of the watermark and the choice of embedded areas based on the perceptivity not only confer the watermark with good invisibility but also with good robustness. Meanwhile, it is difficult to decrypt the watermark extracted from the WT domain.
QIN Ning-ning; ZHANG Lin; SHAN Xiu-ming; XU Bao-guo
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0064-05
Abstract ( 2437 ) PDF (287 KB)( 427 )
Detection coverage control is one of the most important topics in the intrusion detection problem of wireless sensor networks (WSN). However, its converse, i.e., to design an object locomotion trajectory in WSN, has not received enough attention. This article proposes a heuristic algorithm, namely, the security & speed (SS) algorithm, to depict such a trajectory that takes into consideration both security and speed. The merit of the SS algorithm is its topology independency. When compared with traditional algorithms, the SS algorithm approaches the optimal trajectory better, and enjoys considerably lower computational load, and a better and adjustable tradeoff between trajectory security and speed.
YU Yong; YANG Bo; SUN Ying
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0069-06
Abstract ( 2590 ) PDF (170 KB)( 480 )
Proxy signature schemes allow an original signer to delegate his signing rights to a proxy signer. However, many proxy signature schemes have the defect which is the inability to solve the proxy revocation problem. In this article, we firstly propose an identity-based threshold signature scheme and show that it has the properties of unforgeability and robustness. In our threshold signature scheme, we adopt such a method that the private key associated with an identity rather than the master key is shared. Then, based on the threshold signature scheme, an identity-based mediated proxy signature scheme is proposed where a security mediator (SEM) is introduced to help a proxy signer to generate valid proxy signatures, examine whether a proxy signer signs according to the warrant, and check the revocation of a proxy signer. It is shown that the proposed scheme satisfies all the security requirements of a secure proxy signature. Moreover, a proxy signer must cooperate with the SEM to generate a valid proxy signature, which makes the new scheme have an effective and fast proxy revocation.
YANG Chen;MA Wen-ping;WANG Xin-mei
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0075-04
Abstract ( 2501 ) PDF (109 KB)( 425 )
Ju et al. proposed a certificateless signature scheme with instantaneous revocation by introducing security mediator (SEM) mechanism. This article presents a detailed cryptoanalysis of this scheme and shows that, in their proposed scheme, once a valid signature has been produced, the signer can recover his private key information and the instantaneous revocation property will be damaged. Furthermore, an improved mediated signature scheme, which can eliminate these disadvantages, is proposed, and security proof of the improved scheme under elliptic curve factorization problem (ECFP) assumption and bilinear computational diffie-hellman problem (BCDH) assumption is also proposed.
XU Yong;LU Ying-hua
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0079-05
Abstract ( 2620 ) PDF (371 KB)( 426 )
In this article, a novel scattering center extraction method using genetic algorithm is proposed to deal with the ultra-wideband (UWB) localization image, which is called evolutionary programming (EP) CLEAN algorithm. Because of the UWB characters, the ideal point scattering model and EP method are used in the algorithm for optimizing the UWB localization images. After introducing the algorithm detail, the actual model is used to realize the EP CLEAN algorithm. Compared with the conventional localization imaging algorithm, this algorithm has advantages fitting the UWB characters such as accuracy, robustness, and better resolution, which are verified by the numerical simulations. Therefore the EP CLEAN algorithm could improve localization image performance to expand the UWB technique application.
ZHAN Song-tao;XU Guo-xin
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0084-05
Abstract ( 2571 ) PDF (264 KB)( 446 )
Wireless mobile Ad-hoc network is a special network that all nodes can self-organize and work together. It is flexible to form a network and extend the coverage area dynamically without infrastructure, so Ad-hoc network is envisioned as cornerstones of future generation networking technologies (B3G or 4G). However, the dynamic network topology makes the communication cost not only the energy of source/destination nodes, but also the relay nodes. Another problem of the Ad-hoc network is it is hard to provide a stable and persistent quality of service (QoS), which is strongly required by the beyond 3rd generation (B3G) system. In this article, the authors establish a scenario that contains B3G cellular base station and Ad-hoc mobile nodes, and propose two algorithms minimum incremental rate algorithm and power feed-back rate allocation algorithm in multipath routing. The algorithms can maintain a constant total transmission rate and bit error ratio (BER) to provide the QoS guarantee and reach the minimum power consumption of the relay nodes by adjusting the rate of each path in the multipath routing.
LI Ya-zhuo; Zhou Ming-yu;ZHANG Ping
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0089-05
Abstract ( 2772 ) PDF (252 KB)( 414 )
Radio frequency (RF) front-end nonidealities in multi-input and multi-output (MIMO) systems are more serious than in single-input and single-output systems and must be calibrated. According to the effects of RF power and in-phase/quadrature-phase (I/Q) imbalance, calibration methods for multi-input and multi-outputorthogonal frequency division multiplexing (MIMC-OFDM) systems in transmitter and interference in receiver are improved, respectively, in this article. Furthermore, a calibration scheme including I/Q imbalance errors and amplitude variations is proposed and implemented in the B3G/4G time division duplex communication system. Simulation results show that the calibration algorithms are feasible, and the bit error rate (BER) performances for MIMO-OFDM systems are improved after calibrations.
TANG Tian;DENG Gang;JIANG Jun
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0094-05
Abstract ( 2580 ) PDF (209 KB)( 460 )
Orthogonal frequency division multiplexing (OFDM) systems encounter performance degradations because of the time-varying (TV) channels common in wireless environments. The channel variations within one OFDM symbol introduce intercarrier interference. In this case, the frequency domain channel matrix is no longer diagonal, hence the corresponding channel estimation is challenging. In this article, two novel TV channel estimation approaches are proposed for the pilot-assisted OFDM systems, where the channel is approximated by the high-order linear model or the piece-wise linear model in time domain. The least square estimation is derived for the two kinds of channel approximations. The simulation is performed based on realistic TV channels with a fairly high Doppler spread. The results show the significant decreasing of the estimation mean square error using the proposed approaches.
CHE Shu-liang; ZHANG Hong-xin;LU Ying-hua;HE Peng-fei
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： TN914.3
Abstract ( 2913 ) PDF (275 KB)( 541 )
This study investigates a novel method to numerically generate orthogonal ultrawide band (UWB) shaping pulses based on compressed chirp signal. First, a pulse template with less than 1 ns duration time, which is used to construct a Hermitian matrix, is produced with a compressed chirp pulse. Sub-nanosecond orthogonal pulses are then generated for UWB by using the Hermitian matrix eigenvectors. The simulation results show that the power spectral density distribution of the UWB shaping pulses met the constraint of Federal communications commissions (FCC) spectral mask. The shaping pulses not only have higher spectrum utilization ratio and very short time duration but also have excellent autocorrelation and cross-correlation properties, which is an advantage to reduce the interference between multiusers. Especially, a method to produce sub-nanosecond orthogonal UWB shaping pulses by using a relatively longer duration chirp signal is presented.
LIU Yu-liang;ZHU Jie; DING Da-wei
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0103-03
Abstract ( 2809 ) PDF (132 KB)( 662 )
By the control method independent of system parameters, synchronization of two Chen chaotic systems with identical, but uncertain parameters is discussed in this article. Based on Lyapunov’s theorem, an adaptive controller and the parameters estimate update law are derived to make the solution of the error dynamical equation converge at the point E(0, 0, 0) with a quick speed, that is, the states of two Chen chaotic systems can be asymptotically synchronized. Numerical simulations verify the effectiveness and the adaptivity to the variation of Chen system parameters.
ZHU Yue; RONG Meng-tian
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0106-06
Abstract ( 2661 ) PDF (176 KB)( 441 )
This article presents an M-algorithm (MA) decoder with 4 survival paths (MA4) for Institute of Electrical and Electronics Engineers (IEEE) 802.3ab 1000BASE-T gigabit Ethernet (GbE) transceiver. To fulfill the entire requirements, various methods were introduced to accelerate the MA4 decoder while retaining the desired high performance and low complexity. Optimized look-ahead architecture was employed to solve the critical path problem with minimal gate consumption. Symbol compression methods saved registers during pipeline stages. A sorting network accelerated the kernel sorting operation at low hardware cost by utilizing the special characteristics of MA4. Simulations and synthesis results show that the proposed decoder achieves 125 MHz clock frequency and 1 Gb/s throughput in 1.8 V 0.18 μm standard cell complementary metal-oxide-semiconductor (CMOS) process. It achieves additional 0.4 dB coding gain over 14tap parallel decision feedback decoder (PDFD) with 39% area reduction.
CHEN Qiang, CHEN He-xin, SANG Ai-jun
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0112-08
Abstract ( 2969 ) PDF (398 KB)( 400 )
In this article, a new way to evaluate the quality of color images is proposed, in which the properties of human vision psychology, objective fidelity, edge information, and color distortion will be combined through utilizing 3-D matrix transform. There exists color redundancy and structural similarity between three different frames of a color image, the definition of vision properties will be measured by 3-D submatrix integration transform (SIT), in which three color components are integrated into one model and color redundancy can be exploited fully. The simulation results show that the measure index is very effective and objective in accord with vision properties.
YUE Xin, XU Jun-jie, XIN Zhan-hong
The Journal of China Universities of Posts and Telecommunications, 2007, 14 (2). doi： 1005-8885 (2007) 02-0120-05
Abstract ( 2264 ) PDF (168 KB)( 398 )
Based on the premise of obtaining optimal revenue, a mathematical model about operation strategies of service provider (SP) in duopoly telecom market was established in this article. In consideration of complexities, the model was transformed from a tri-game to two-party game model under four hypotheses. Nash equilibrium solution between SP and two carriers was proposed with detailed analyses. The value ranges under different cases provided a reference for carriers and SP while deciding share ratios.