CUI Qi-mei, LIU Jun, TAO Xiao-feng, ZHANG Ping
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0001-06
Abstract ( 1945 ) PDF (608 KB)( 386 )
Because of the wide application and great market potential of location-aware services, the research of wireless location techniques for the fourth generation (4G) mobile communications is being paid more attention. Wireless cognitive location (WCL) techniques for next generation wireless networks have been proposed in recent years. This article investigates the changes of the positioning accuracy of WCL algorithm when different methods are adopted to measure the short-range (SR) information. By first completing Cramér-Rao lower bound (CRLB) analysis of the WCL algorithm with SR measurements based on time of arrival (TOA) and received signal strength (RSS), it is discovered that TOA-based or time difference of arrival (TDOA) -based SR measurement can make WCL algorithms achieve higher accuracy than RSS mode, which is also verified by numerical simulation in the article. The conclusions can instruct the design of novel WCL-based location algorithms.
YU Jiang, LI Xiao-jun, YUE Guang-xin
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0007-05
Abstract ( 2412 ) PDF (226 KB)( 398 )
This article proposes a multistage soft decision equalization (SDE) technique for block transmission over frequency selective multi-input multi-output (MIMO) channels. Using the Toeplitz structure, the general signal model can be converted into a series of small-sized sub-signal models. For each sub-signal model, soft interference cancellation (SIC) is used firstly to remove partial effects of interfering symbols, then max-log-MAP sphere decoder is performed to get the desired a posteriori information. Simulation shows that with lower complexity the proposed method outperforms the probability data association SDE and the Schnorr-Euchner sphere decoder.
XU Wen-jun, HE Zhi-qiang
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0012-06
Abstract ( 3285 ) PDF (286 KB)( 428 )
This article studies downlink subcarrier assignment problem to maximize rate-sum capacity subject to total power and proportional rate constraints in orthogonal frequency division multiplexing (OFDM) systems. Previous algorithms assume that the initial power is equally distributed over all subcarriers. The presence of path loss makes the assumption not correct any more. This article proposes a novel subcarrier assignment algorithm which makes full use of path loss and rate proportionality information to improve rate-sum capacity. The proposed algorithm determines optimal initial power allocation according to path losses and rate proportionalities of different users, assigns subcarriers to users in a greedy fashion, and then exchanges subcarriers between users to obtain fairer rate distribution. Simulation results show that the proposed algorithm approximately achieves double the capacity of static assignment schemes, such as fixed frequency band approach, and obtains better performance than previous subcarrier assignment algorithms in the presence of different path losses and proportional rate requirements.
ZOU Yu-long, ZHENG Bao-yu
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0018-08
Abstract ( 3631 ) PDF (405 KB)( 693 )
MIMO technology proposed in recent years can effectively combat the multipath fading of wireless channel and can considerably enlarge the channel capacity, which has been investigated widely by researchers. However, its performance analysis over correlated block-fading Rayleigh channel is still an open and challenging objective. In this article, an analytic expression of bit error rate (BER) is presented for multiple phase shift keying (MPSK) space-time code, with differential detection over correlated block-fading Rayleigh channel. Through theoretical analysis of BER, it can be found that the differential space-time scheme without the need for channel state information (CSI) at receiver achieves distinct performance gain compared with the traditional nonspace-time system. And then, the system simulation is complimented to verify the above result, showing that the diversity system based on the differential space-time block coding (DSTBC) outperforms the traditional nonspace- time system with diversity gain in terms of BER. Furthermore, the numerical results also demonstrate that the error floor of the differential space-time system is much lower than that of the differential nonspace-time system.
JIA Min, GU Xue-mai, IM Se-bin, CHOI Hyung-jin
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0026-06
Abstract ( 3376 ) PDF (263 KB)( 453 )
Channel impulse response (CIR) can be estimated on the basis of cyclic correlation in time-domain for orthogonal frequency division multiplexing (OFDM) systems. This article proposes a generalized channel estimation method to reduce the estimation error by taking the average of different CIRs. Channel impulse responses are derived according to the different starting points of cyclic correlation. In addition, an effective CIR length estimation algorithm is also presented. The whole proposed methods are more effective to OFDM systems, especially to those with longer cyclic prefix. The analysis and the simulation results verify that the mean square error performance is 45 dB better than the conventional schemes under the same conditions.
TIAN Zeng-shan, ZHOU Fei, ZHANG Tian-qi
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0032-07
Abstract ( 2638 ) PDF (384 KB)( 369 )
To overcome the drawback of a short operation range and low-resolution of a passive location system using a civil communication signal, the new idea that utilizes code division multiple access (CDMA) signal and repeater is disposed off. First, the CDMA passive location model and observation function are given, and the error source and error range are analyzed. Subsequently, the CDMA passive location algorithm in a repeater environment is described and simulated. The simulation result shows that the algorithm can provide the location value with high accuracy.
CHE Wen, ZHAO Hui, WANG Wen-bo
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0039-06
Abstract ( 3097 ) PDF (222 KB)( 365 )
In the downlink of wideband code division multiple access (WCDMA) or WCDMA- high speed downlink packet access (HSDPA) system, the frequency reuse factor is equal to 1, which leads to more possible co-channel interference from neighbor cells. In this situation, user equipment (UE) with traditional receiver will suffer from significant performance degradation at the edge of the cell. To solve this problem, a receiver structure considering interference mitigation has been proposed for long term evolution (LTE) of third-generation partnership project (3GPP). Such receiver makes use of all the interfering cells’ channel information to perform a linear minimum mean square error (LMMSE) equalization algorithm. In this article, an improved equalization algorithm is presented, which simply adds more samples to perform one equalization operation. Simulations show that the proposed algorithm can obtain a considerable performance improvement in frequency selective fading channel, with relative little additional complexity introduced.
SONG Xing-hua, WU Wei-ling
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0045-05
Abstract ( 2812 ) PDF (291 KB)( 426 )
This article deals with downlink scheduling for multiuser multiple-input multiple-output (MIMO) systems, where the base station communicates with multiple users simultaneously through transmit beamforming. Most of the existing transmission schemes for multiuser MIMO systems focus on optimizing sum rate performance of the system. The individual quality of service (QoS) requirements (such as packet delay and minimum transmission rate for the data traffic) are rarely considered. In this article, a novel scheduling strategy is proposed, where we try to optimize the global system performance under individual QoS constraints. By performing scheduling into two steps, namely successive user selection and power allocation, the scheduler can achieve efficient resource utilization while maintaining the QoS requirements of all users. Extensive simulations and analysis are given to show the effectiveness of the proposed scheduler.
ZHAO Yi, ZENG Ling-kang, XIE Gang, LIU Yuan-an, XIONG Fang
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0050-06
Abstract ( 3482 ) PDF (277 KB)( 443 )
This article investigates two fairness criteria with regard to adaptive resource allocation for uplink orthogonal frequency division multiple access (OFDMA) systems. Nash bargaining solution (NBS) fairness and proportional fairness (PF) are two suitable candidates for fairness consideration, and both can provide attractive trade-offs between total throughput and each user’s capacity. Utilizing Karush-Kuhn- Tucker (KKT) condition and iterative method, two effective algorithms are designed, to achieve NBS fairness and proportional fairness, respectively. Simulation results show that the proposed resource allocation algorithms achieve good tradeoff between the overall rate and fairness, with little performance loss from the total capacity.
ZHANG Lei, YUAN Ting-ting, ZHANG Xin, YANG Da-cheng
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0056-04
Abstract ( 3083 ) PDF (148 KB)( 377 )
In this article, a new system model for sphere decoding (SD) algorithm is introduced. For the multiple- input multiple-out (MIMO) system, a simplified maximum likelihood (SML) decoding algorithm is proposed based on the new model. The SML algorithm achieves optimal maximum likelihood (ML) performance, and drastically reduces the complexity as compared to the conventional SD algorithm. The improved algorithm is presented by combining the sphere decoding algorithm based on Schnorr-Euchner strategy (SE-SD) with the SML algorithm when the number of transmit antennas exceeds 2. Compared to conventional SD, the proposed algorithm has low complexity especially at low signal to noise ratio (SNR). It is shown by simulation that the proposed algorithm has performance very close to conventional SD.
XIA Wei, LI Zhao-hui, CHEN Zeng-qiang, YUAN Zhu-zhi
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0060-07
Abstract ( 2630 ) PDF (290 KB)( 638 )
Commwarrior worm is capable of spreading through both Bluetooth and multimedia messaging service (MMS) in smart phone networks. According to the propagation characteristics of Bluetooth and MMS, we built the susceptible- exposed-infected-recovered-dormancy (SEIRD) model for the Bluetooth and MMS hybrid spread mode and performed the stability analysis. The simulation results show good correlation with our theoretical analysis and demonstrate the effectiveness of this dynamic propagation model. On the basis of the SEIRD model, we further discuss at length the influence of the propagation parameters such as user gather density in groups, moving velocity of smart phone, the time for worm to replicate itself, and other interrelated parameters on the propagation of the virus. On the basis of these analytical and simulation results, some feasible control strategies will be proposed to restrain the spread of mobile worm such as commwarrior on smart phone network.
LIN Xin-qi, WEN Xiang-ming，ZHANG Sheng-yuan，ZHENG Wei
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0067-05
Abstract ( 2670 ) PDF (121 KB)( 385 )
The type II codes have been studied widely in applications since their appearance. With analysis of the algebraic structure of finite field of order 4 (i.e., GF(4)), some necessary and sufficient conditions that a generalized H-code (i.e., GH-code) is a type II code over GF(4) are given in this article, and an efficient and simple method to generate type II codes from GH-codes over GF(4) is shown. The conclusions further extend the coding theory of type II.
CHEN Yi-cheng, ZOU Xue-cheng, LIU Zheng-lin, CHEN Xiao-fei, HAN Yu
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0072-05
Abstract ( 3391 ) PDF (289 KB)( 490 )
It is an important challenge to implement a low- cost power analysis immune advanced encryption standard (AES) circuit. The previous study proves that substitution boxes (S-Boxes) in AES are prone to being attacked, and hard to mask for its non-linear characteristic. Besides, large amounts of circuit resources in chips and power consumption are spent in protecting S-Boxes against power analysis. Thus, a novel power analysis immune scheme is proposed, which divides the data-path of AES into two parts: inhomogeneous S-Boxes instead of fixed S-Boxes are selected randomly to disturb power and logic delay in the non-linear module; at the same time, the general masking strategy is applied in the linear part of AES. This improved AES circuit was synthesized with united microelectronics corporation (UMC) 0.25 μm 1.8 V complementary metal-oxide-semiconductor (CMOS) standard cell library, and correlation power analysis experiments were executed. The results demonstrate that this secure AES implementation has very low hardware cost and can enhance the AES security effectually against power analysis.
KE Pin-hui, ZHANG Sheng-yuan
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0077-05
Abstract ( 1827 ) PDF (170 KB)( 353 )
Carlet et al. recently introduced generalized nonlinearity to measure the ability to resist the improved correlation attack of a vector output Boolean function. This article presents a construction of vector output Boolean functions with high generalized nonlinearity using the sample space. The relation between the resilient order and generalized nonlinearity is also discussed.
LI Lei-da, GUO Bao-long, GUO Lei
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0082-06
Abstract ( 2647 ) PDF (543 KB)( 509 )
In this article, a novel robust image watermarking scheme is presented to resist rotation, scaling, and translation (RST). Initially, the original image is scale normalized, and the feature points are then extracted. Furthermore, the locally most stable feature points are used to generate several nonoverlapped circular regions. These regions are then rotation normalized to generate the invariant regions. Watermark embedding and extraction are used in the invariant regions in discrete cosine transform domain. In the decoder, the watermark can be extracted without the original image. Simulation results show that the proposed scheme is robust to traditional signal processing attacks, RST attacks, as well as some combined attacks.
WANG Jian, WANG Hui-qiang, ZHAO Guo-sheng
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0088-09
Abstract ( 3217 ) PDF (348 KB)( 451 )
Survivability should be considered beyond security for information system. To assess system survivability accurately, for improvement, a formal modeling and analysis method based on stochastic process algebra is proposed in this article. By abstracting the interactive behaviors between intruders and information system, a transferring graph of system state oriented survivability is constructed. On that basis, parameters are defined and system behaviors are characterized precisely with performance evaluation process algebra (PEPA), simultaneously considering the influence of different attack modes. Ultimately the formal model for survivability is established and quantitative analysis results are obtained by PEPA Workbench tool. Simulation experiments show the effectiveness and feasibility of the developed method, and it can help to direct the designation of survivable system.
LI Qi-yue, QU Yu-gui, ZHAO Bao-hua
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0097-05
Abstract ( 2271 ) PDF (297 KB)( 389 )
In network packet processing, high-performance string lookup systems are very important. In this article, an extended Bloom filter data structure is introduced to support value retrieval string lookup, and to improve its performance, a weighted extended Bloom filter (WEBF) structure is generalized. The optimal configuration of the WEBF is then derived, and it is shown that it outperforms the traditional Bloom filter. Finally, an application-specific integrated circuit (ASIC)-based technique using WEBF is outlined.
ZHENG Zhao-xia, ZOU Lian-ying, GAO Jun
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0102-05
Abstract ( 2425 ) PDF (347 KB)( 373 )
Information appliance is the combination of traditional home appliances and the internet technology. In this article, an Ethernet controller system-on-chip (SOC) solution for information appliances is presented. To achieve high performance, the embedded 8 bits 8051 micro control unit (MCU) is optimized by an independent instruction bus and a data bus. Besides, a two-stage pipeline feature is added. Compared with the existing 8051 core, the enhanced one-cycle MCU offers ten times improvement in instruction execution efficiency. Mean- while, the performance of media access control (MAC) circuit is greatly improved by adopting various techniques such as direct memory access (DMA) control, paging strategy, etc. To reduce the power consumption, clock gating, low power supply, and multi-working-clock are adopted. Moreover, to achieve rapid data communication in different clock frequency circuits, a simple ping-pong first in first out (FIFO) circuit is realized. The chip is implemented using TSMC 0.25 µm two-poly four-metal mixed signal complementary metal oxide semiconductor (CMOS) technology. Its die area is mm. The test results show that the maximum throughput of Ethernet packets can reach 7 Mb/s while the power consumption is rather lowthe working current is just about 200 mA.
WANG Yang, WANG Ru-chuan, CHENG Xi
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0107-07
Abstract ( 1949 ) PDF (375 KB)( 403 )
Multipath routing mechanism is vital for reliable packet delivery, load balance, and flexibility in the open network because its topology is dynamic and the nodes have limited capability. This article proposes a new multipath switch approach based on traffic prediction according to some characteristics of open networks. We use wavelet neural network (WNN) to predict the node traffic because the method has not only good approximation property of wavelet, but also self-learning adaptive quality of neural network. When the traffic prediction indicates that the primary path is a failure, the alternate path will be occupied promptly according to the switch strategy, which can save time for the switch in advance. The simulation results show that the presented traffic prediction model has better prediction accuracy; and the approach based on the above model can balance network load, prolong network lifetime, and decrease the overall energy consumption of the network.
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0114-08
Abstract ( 2558 ) PDF (282 KB)( 432 )
The M/G/1 queueing system with multiclass customer arrivals, fixed feedback, and first come first served policy is considered, where different classes of customers have different arrival rates, service-time distributions, and feedback numbers. The joint probability generation function of queue size of each class and the Laplace-Stieltjes transform of the total sojourn time of a customer in each class are presented, which extended the results obtained by Choi B D. The mean queue size of each class and mean total sojourn time of a customer in each class are obtained with this result. The results can be used in computer and communication networks for their performance analysis.
XU Jun-jie, YUE Xin, XIN Zhan-hong
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0122-03
Abstract ( 2481 ) PDF (97 KB)( 379 )
To improve the performance of extended particle swarm optimizer, a novel means of stochastic weight deployment is proposed for the iterative equation of velocity updation. In this scheme, one of the weights is specified to a random number within the range of [0, 1] and the other two remain constant configurations. The simulations show that this weight strategy outperforms the previous deterministic approach with respect to success rate and convergence speed. The experi- ments also reveal that if the weight for global best neighbor is specified to a stochastic number, extended particle swarm optimizer achieves high and robust performance on the given multi-modal function.
MA Ying-cang, HE Hua-can
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0125-05
Abstract ( 2236 ) PDF (173 KB)( 349 )
The aim of this article is the partial axiomatization for 1-level universal logic. A propositional calculus formal deductive system based on 1-level universal AND operator of universal logic is built up. The corresponding algebra is introduced. The soundness and the completeness of system are proved.
ZHAO Jian, DONG Yuan, ZHAO Xian-yu, YANG Hao, WANG Hai-la
The Journal of China Universities of Posts and Telecommunications, 2008, 15 (2). doi： 1005-8885 (2008) 02-0130-05
Abstract ( 2313 ) PDF (158 KB)( 389 )
Speaker adaptive test normalization (ATnorm) is the most effective approach of the widely used score normalization in text-independent speaker verification, which selects speaker adaptive impostor cohorts with an extra development corpus in order to enhance the recognition performance. In this paper, an improved implementation of ATnorm that can offer overall significant advantages over the original ATnorm is presented. This method adopts a novel cross similarity measurement in speaker adaptive cohort model selection without an extra development corpus. It can achieve a comparable performance with the original ATnorm and reduce the computation complexity moderately. With the full use of the saved extra development corpus, the overall system performance can be improved significantly. The results are presented on NIST 2006 Speaker Recognition Evaluation data corpora where it is shown that this method provides significant improvements in system performance, with relatively 14.4% gain on equal error rate (EER) and 14.6% gain on decision cost function (DCF) obtained as a whole.