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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Electronics and Telecommunications Research Institute
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Volume & Issues
Volume 36, Issue 6 - Dec 2014
Volume 36, Issue 5 - Oct 2014
Volume 36, Issue 4 - Aug 2014
Volume 36, Issue 3 - Jun 2014
Volume 36, Issue 2 - Apr 2014
Volume 36, Issue 1 - Feb 2014
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Distributed Synchronization for OFDMA-Based Wireless Mesh Networks
Kim, Jihyung ; Kim, Jung-Hyun ; Lim, Kwangjae ;
ETRI Journal, volume 36, issue 1, 2014, Pages 1~11
DOI : 10.4218/etrij.14.0113/0223
In this paper, we propose a distributed synchronization algorithm for wireless mesh networks based on orthogonal frequency division multiple access. For time and frequency synchronization, a node requests its neighbor nodes for a change of fast Fourier transform starting points, transmission times, and carrier frequencies needed for synchronization. The node also updates its own time and frequency elements through simple formulas based on request messages received from neighbor nodes using a guard interval and a cyclic prefix. This process with the cooperation of neighbor nodes leads to a gradual synchronization of all nodes in the network. Through a performance comparison with a conventional scheme, we obtain simulation results indicating that the proposed scheme outperforms the conventional scheme in random topologies and a grid topology.
A Fast and Precise Blind I/Q Mismatch Compensation for Image Rejection in Direct-Conversion Receiver
Kim, Suna ; Yoon, Dae-Young ; Park, Hyung Chul ; Yoon, Giwan ; Lee, Sang-Gug ;
ETRI Journal, volume 36, issue 1, 2014, Pages 12~21
DOI : 10.4218/etrij.14.0113.0320
In this paper, we propose a new digital blind in-phase/quadrature-phase (I/Q) mismatch compensation technique for image rejection in a direct-conversion receiver (DCR). The proposed image-rejection circuit adopts DC offset cancellation and a sign-sign least mean squares (LMS) algorithm with a unique step size adaptation both for a fast and precise I/Q mismatch estimation. In addition, several performance-optimizing design considerations related to accuracy, speed, and hardware simplicity are discussed. The implementation of the proposed circuit in an FPGA results in an image-rejection ratio (IRR) of 65 dB, which is the best performance with modulated signals, along with an adaptation time of 0.9 seconds, which is a tenfold increase in the compensation speed as compared to previously reported circuits. The proposed technique will be a promising solution in the area of image rejection to increase both the speed and accuracy of future DCRs.
Outage Probability of Decode-and-Forward Relaying Systems with Efficient Partial Relay Selection in Nakagami Fading Channels
Lee, Sangjun ; Lee, Howon ; Choi, Hyun-Ho ; Lee, In-Ho ;
ETRI Journal, volume 36, issue 1, 2014, Pages 22~30
DOI : 10.4218/etrij.14.0113.0348
Recently, efficient partial relay selection (e-PRS) was proposed as an enhanced version of PRS. In comparing e-PRS, PRS, and the best relay selection (BRS), there is a tradeoff between complexity and performance; that is, the complexity for PRS, e-PRS, and BRS is low to high, respectively, but vice versa for performance. In this paper, we study the outage probability for e-PRS in decode-and-forward (DF) relaying systems over non-identical Nakagami-m fading channels, where the fading parameter m is an integer. In particular, we provide closed-form expressions of the exact outage probability and asymptotic outage probability for e-PRS in DF relaying systems. Numerical results show that e-PRS achieves similar outage performance to that of BRS for a low or medium signal-to-noise ratio, a high fading parameter, a small number of relays, and a large difference between the average channel powers for the first and the second hops.
Quasi-distributed Interference Coordination for HSPA HetNet
Zhang, Chi ; Chang, Yongyu ; Qin, Shuqi ; Yang, Dacheng ;
ETRI Journal, volume 36, issue 1, 2014, Pages 31~41
DOI : 10.4218/etrij.14.0113.0455
The heterogeneous network (HetNet) has been discussed in detail in the Long-Term Evolution (LTE) and LTE Advanced standards. However, the standardization of High-Speed Packet Access HetNet (HSPA HetNet) launched by 3GPP is pushing at full steam. Interference coordination (IC), which is responsible for dealing with the interference in the system, remains a subject worthy of investigation in regard to HSPA HetNet. In this paper, considering the network framework of HSPA HetNet, we propose a quasi-distributed IC (QDIC) scheme to lower the interference level in the co-channel HSPA HetNet. Our QDIC scheme is constructed as slightly different energy-efficient non-cooperative games in the downlink (DL) and uplink (UL) scenarios, respectively. The existence and uniqueness of the equilibrium for these games are first revealed. Then, we derive the closed-form best responses of these games. A feasible implementation is finally developed to achieve our QDIC scheme in the practical DL and UL. Simulation results show the notable benefits of our scheme, which can indeed control the interference level and enhance the system performance.
A Modified Method Based on the Discrete Sliding Norm Transform to Reduce the PAPR in OFDM Systems
Salmanzadeh, R. ; Mozaffari Tazehkand, B. ;
ETRI Journal, volume 36, issue 1, 2014, Pages 42~50
DOI : 10.4218/etrij.14.0113.0053
Orthogonal frequency division multiplexing (OFDM) is a modulation technique that allows the transmission of high data rates over wideband radio channels subject to frequency selective fading by dividing the data into several narrowband and flat fading channels. OFDM has high spectral efficiency and channel robustness. However, a major drawback of OFDM is that the peak-to-average power ratio (PAPR) of the transmitted signals is high, which causes nonlinear distortion in the received data and reduces the efficiency of the high power amplifier in the transmitter. The most straightforward method to solve this problem is to use a nonlinear mapping algorithm to transform the signal into a new signal that has a smaller PAPR. One of the latest nonlinear methods proposed to reduce the PAPR is the
-by-3 algorithm, which is based on the discrete sliding norm transform. In this paper, a new algorithm based on the
-by-3 method is proposed. The proposed method is very simple and has a low complexity analysis. Simulation results show that the proposed method performs better, has better power spectral density, and is less sensitive to the modulation type and number of subcarriers than
Enhancing Security in Mobile IPv6
Modares, Hero ; Moravejosharieh, Amirhossein ; Salleh, Rosli Bin ; Lloret, Jaime ;
ETRI Journal, volume 36, issue 1, 2014, Pages 51~61
DOI : 10.4218/etrij.14.0113.0177
In the Mobile IPv6 (MIPv6) protocol, a mobile node (MN) is a mobile device with a permanent home address (HoA) on its home link. The MN will acquire a care-of address (CoA) when it roams into a foreign link. It then sends a binding update (BU) message to the home agent (HA) and the correspondent node (CN) to inform them of its current CoA so that future data packets destined for its HoA will be forwarded to the CoA. The BU message, however, is vulnerable to different types of security attacks, such as the man-in-the-middle attack, the session hijacking attack, and the denial-of-service attack. The current security protocols in MIPv6 are not able to effectively protect the BU message against these attacks. The private-key-based BU (PKBU) protocol is proposed in this research to overcome the shortcomings of some existing MIPv6 protocols. PKBU incorporates a method to assert the address ownership of the MN, thus allowing the CN to validate that the MN is not a malicious node. The results obtained show that it addresses the security requirements while being able to check the address ownership of the MN. PKBU also incorporates a method to verify the reachability of the MN.
Novel SINR-Based User Selection for an MU-MIMO System with Limited Feedback
Kum, Donghyun ; Kang, Daegeun ; Choi, Seungwon ;
ETRI Journal, volume 36, issue 1, 2014, Pages 62~68
DOI : 10.4218/etrij.14.0113.0267
This paper presents a novel user selection method based on the signal-to-interference-plus-noise ratio (SINR), which is approximated using limited feedback data at the base stations (BSs) of multiple user multiple-input multiple-output (MU-MIMO) systems. In the proposed system, the codebook vector index, the quantization error obtained from the correlation between the measured channel and the codebook vector, and the measured value of the largest singular value are fed back from each user to the BS. The proposed method not only generates precoding vectors that are orthogonal to the precoding vectors of the previously selected users and are highly correlated with the codebook vector of each user but also adopts the quantization error in approximating the SINR, which eventually provides a significantly more accurate SINR than the conventional SINR-based user selection techniques. Computer simulations show that the proposed method enhances the sum rate of the conventional SINR-based methods by at least 2.4 (2.62) bps/Hz when the number of transmit antennas and number of receive antennas per user terminal is 4 and 1(2), respectively, with 100 candidate users and an SNR of 30 dB.
An Approach to Scheduling Bursty Traffic
Farzanegan, Mahmoud Daneshvar ; Saidi, Hossein ; Mahdavi, Mehdi ;
ETRI Journal, volume 36, issue 1, 2014, Pages 69~79
DOI : 10.4218/etrij.14.0112.0524
The scheduling scheme in packet switching networks is one of the most critical features that can affect the performance of the network. Hence, many scheduling algorithms have been suggested and some indices, such as fairness and latency, have been proposed for the comparison of their performances. While the nature of Internet traffic is bursty, traditional scheduling algorithms try to smooth the traffic and serve the users based on this smoothed traffic. As a result, the fairness index mainly considers this smoothed traffic and the service rate as the main parameter to differentiate among different sessions or flows. This work uses burstiness as a differentiating factor to evaluate scheduling algorithms proposed in the literature. To achieve this goal, a new index that evaluates the performance of a scheduler with bursty traffic is introduced. Additionally, this paper introduces a new scheduler that not only uses arrival rates but also considers burstiness parameters in its scheduling algorithms.
An Adaptive Smart Grid Management Scheme Based on the Coopetition Game Model
Kim, Sungwook ;
ETRI Journal, volume 36, issue 1, 2014, Pages 80~88
DOI : 10.4218/etrij.14.0113.0042
Recently, the idea of the smart grid has been gaining significant attention and has become a hot research topic. The purpose of this paper is to present a novel smart grid management scheme that uses game theory principles. In our proposed scheme, power appliances in the smart grid adaptively form groups according to the non-cooperative hedonic game model. By exploiting multi-appliance diversity, appliances in each group are dynamically scheduled in a cooperative manner. For efficient smart grid management, the proposed coopetition game approach is dynamic and flexible to adaptively respond to current system conditions. The main feature is to maximize the overall system performance while satisfying the requirements of individual appliances. Simulation results indicate that our proposed scheme achieves higher energy efficiency and better system performance than other existing schemes.
An Efficient 5-Input Exclusive-OR Circuit Based on Carbon Nanotube FETs
Zarhoun, Ronak ; Moaiyeri, Mohammad Hossein ; Farahani, Samira Shirinabadi ; Navi, Keivan ;
ETRI Journal, volume 36, issue 1, 2014, Pages 89~98
DOI : 10.4218/etrij.14.0113.0051
The integration of digital circuits has a tight relation with the scaling down of silicon technology. The continuous scaling down of the feature size of CMOS devices enters the nanoscale, which results in such destructive effects as short channel effects. Consequently, efforts to replace silicon technology with efficient substitutes have been made. The carbon nanotube field-effect transistor (CNTFET) is one of the most promising replacements for this purpose because of its essential characteristics. Various digital CNTFET-based circuits, such as standard logic cells, have been designed and the results demonstrate improvements in the delay and energy consumption of these circuits. In this paper, a new CNTFET-based 5-input XOR gate based on a novel design method is proposed and simulated using the HSPICE tool based on the compact SPICE model for the CNTFET at the 32-nm technology node. The proposed method leads to improvements in performance and device count compared to the conventional CMOS-style design.
Real-Time Locomotion Mode Recognition Employing Correlation Feature Analysis Using EMG Pattern
Kim, Deok-Hwan ; Cho, Chi-Young ; Ryu, Jaehwan ;
ETRI Journal, volume 36, issue 1, 2014, Pages 99~105
DOI : 10.4218/etrij.14.0113.0064
This paper presents a new locomotion mode recognition method based on a transformed correlation feature analysis using an electromyography (EMG) pattern. Each movement is recognized using six weighted subcorrelation filters, which are applied to the correlation feature analysis through the use of six time-domain features. The proposed method has a high recognition rate because it reflects the importance of the different features according to the movements and thereby enables one to recognize real-time EMG patterns, owing to the rapid execution of the correlation feature analysis. The experiment results show that the discriminating power of the proposed method is 85.89% (
) when walking on a level surface, 96.47% (
) when going up stairs, and 96.37% (
) when going down stairs for given normal movement data. This makes its accuracy and stability better than that found for the principal component analysis and linear discriminant analysis methods.
Study on Characteristics of Various RF Transmission Line Structures on PES Substrate for Application to Flexible MMIC
Yun, Young ; Kim, Hong Seung ; Jang, Nakwon ;
ETRI Journal, volume 36, issue 1, 2014, Pages 106~115
DOI : 10.4218/etrij.14.0113.0124
In this work, the coplanar waveguide is fabricated on a PES (poly[ether sulfone]) substrate for application to a flexible monolithic microwave integrated circuit, and its RF characteristics were thoroughly investigated. The quality factor of the coplanar waveguide on PES is 40.3 at a resonance frequency of 46.7 GHz. A fishbone-type transmission line (FTTL) structure is also fabricated on the PES substrate, and its RF characteristics are investigated. The wavelength of the FTTL on PES is 5.11 mm at 20 GHz, which is 55% of the conventional coplanar waveguide on PES. Using the FTTL, an impedance transformer is fabricated on PES. The size of the impedance transformer is
, which is 69.2% of the size of the transformer fabricated by the conventional coplanar waveguide on PES. The impedance transformer showed return loss values better than -12.9 dB from 5 GHz to 50 GHz and an insertion loss better than -1.13 dB in the same frequency range.
A Novel Unequal Broadband Out-of-Phase Power Divider Using DSPSLs
Lu, Yun Long ; Dai, Gao-Le ; Li, Kai ;
ETRI Journal, volume 36, issue 1, 2014, Pages 116~123
DOI : 10.4218/etrij.14.0113.0125
In this paper, a novel unequal broadband out-of-phase power divider (PD) is presented. Double-sided parallel-strip lines (DSPSLs) are employed to achieve an out-of-phase response. Also, an asymmetric dual-band matching structure with two external isolation resistors is utilized to obtain arbitrary unequal power division, in which the resistors are directly grounded for heat sinking. A through ground via (TGV), connecting the top and bottom sides of the DSPSLs, is used to short the isolation components. Additionally, this property can efficiently improve the broadband matching and isolation bandwidths. To investigate the proposed divider in detail, a set of design equations are derived based on the circuit theory and transmission line theory. The theoretical analysis shows that broadband responses can be obtained as proper frequency ratios are adopted. To verify the proposed concept, a sample divider with a power division of 2:1 is demonstrated. The measured results exhibit a broad bandwidth from 1.19 GHz to 2.19 GHz (59.2%) with a return loss better than 10 dB and port isolation of 18 dB.
Locality-Conscious Nested-Loops Parallelization
Parsa, Saeed ; Hamzei, Mohammad ;
ETRI Journal, volume 36, issue 1, 2014, Pages 124~133
DOI : 10.4218/etrij.14.0113.0266
To speed up data-intensive programs, two complementary techniques, namely nested loops parallelization and data locality optimization, should be considered. Effective parallelization techniques distribute the computation and necessary data across different processors, whereas data locality places data on the same processor. Therefore, locality and parallelization may demand different loop transformations. As such, an integrated approach that combines these two can generate much better results than each individual approach. This paper proposes a unified approach that integrates these two techniques to obtain an appropriate loop transformation. Applying this transformation results in coarse grain parallelism through exploiting the largest possible groups of outer permutable loops in addition to data locality through dependence satisfaction at inner loops. These groups can be further tiled to improve data locality through exploiting data reuse in multiple dimensions.
A New Parameter Estimation Method for a Zipf-like Distribution for Geospatial Data Access
Li, Rui ; Feng, Wei ; Wang, Hao ; Wu, Huayi ;
ETRI Journal, volume 36, issue 1, 2014, Pages 134~140
DOI : 10.4218/etrij.14.0113.0293
Many reports have shown that the access pattern for geospatial tiles follows Zipf's law and that its parameter
represents the access characteristics. However, visits to geospatial tiles have temporal and spatial popularities, and the
-value changes as they change. We construct a mathematical model to simulate the user's access behavior by studying the attributes of frequently visited tile objects to determine parameter estimation algorithms. Because the least squares (LS) method in common use cannot obtain an exact
-value and does not provide a suitable fit to data for frequently visited tiles, we present a new approach, which uses a moment method of estimation to obtain the value of
is close to 1. When
is further away from 1, the method uses the associated cache hit ratio for tile access and uses an LS method based on a critical cache size to estimate the value of
. The decrease in the estimation error is presented and discussed in the section on experiment results. This new method, which provides a more accurate estimate of
than earlier methods, promises more effective prediction of requests for frequently accessed tiles for better caching and load balancing.
A Fully Integrated CMOS Security-Enhanced Passive RFID Tag
Choi, Suna ; Kim, Hyunseok ; Lee, Sangyeon ; Lee, Kangbok ; Lee, Heyungsub ;
ETRI Journal, volume 36, issue 1, 2014, Pages 141~150
DOI : 10.4218/etrij.14.0112.0674
A fully integrated CMOS security-enhanced passive (SEP) tag that compensates the security weakness of ISO/IEC 18000-6C is presented in this paper. For this purpose, we propose a security-enhanced protocol that provides mutual authentication between tag and reader. We show that the proposed protocol meets the security demands of the ongoing international standard for RFID secure systems, ISO/IEC 29167-6. This paper fabricates the SEP tag with a 0.18-
CMOS technology and suggests the optimal operating frequency of the CMOS SEP tag to comply with ISO/IEC 18000-6C. Furthermore, we measure the SEP tag under a wireless environment. The measured results show that communications between the SEP tag and reader are successfully executed in both conventional passive and SEP modes, which follow ISO/IEC 18000-6C and the proposed security enhanced protocol, respectively. In particular, this paper shows that the SEP tag satisfies the timing link requirement specified in ISO/IEC 18000-6C.
CPW-Fed Arbitrary Frequency-Switchable Antenna Using CRLH Transmission Line
Lim, Inseop ; Lim, Sungjoon ;
ETRI Journal, volume 36, issue 1, 2014, Pages 151~154
DOI : 10.4218/etrij.14.0213.0027
A novel frequency-switchable antenna that uses PIN diodes and a composite right- and left-handed transmission line (CRLH TL) is proposed. The CRLH TL provides multi-order resonance, including a zeroth-order resonance (ZOR), and its shunt stub determines the ZOR frequency. Thus, the resonant frequency is arbitrarily chosen by lumped chip inductors on the shunt stub. Two prototypes are designed using different chip inductors while maintaining the antenna geometries. Antenna #1 can switch the resonant frequency from 1.8 GHz to 2.3 GHz. Antenna #2 can switch its resonance from 0.9 GHz to 2.3 GHz.
Design and Analysis of Polarization Diversity Antenna for Mobile Terminals
Lee, Won-Woo ; Rhee, Byung-Ho ;
ETRI Journal, volume 36, issue 1, 2014, Pages 155~158
DOI : 10.4218/etrij.14.0213.0280
This letter presents an antenna design method for an orthogonally-polarized dual antenna for use in mobile stations (MSs) and includes a verification method for improving the link-level throughput performance of an MS that uses a proposed multiple-input multiple-output antenna. The link-level throughput performance of an MS is strongly related to the correlation between antenna branches, which is determined by the cross polarization discrimination of the second branch antenna, both numerically and experimentally.
Generation and Detection of Terahertz Waves Using Low-Temperature-Grown GaAs with an Annealing Process
Moon, Kiwon ; Choi, Jeongyong ; Shin, Jun-Hwan ; Han, Sang-Pil ; Ko, Hyunsung ; Kim, Namje ; Park, Jeong-Woo ; Yoon, Young-Jong ; Kang, Kwang-Yong ; Ryu, Han-Cheol ; Park, Kyung Hyun ;
ETRI Journal, volume 36, issue 1, 2014, Pages 159~162
DOI : 10.4218/etrij.14.0213.0319
In this letter, we present low-temperature grown GaAs (LTG-GaAs)-based photoconductive antennas for the generation and detection of terahertz (THz) waves. The growth of LTG-GaAs and the annealing temperatures are systematically discussed based on the material characteristics and the properties of THz emission and detection. The optimum annealing temperature depends on the growth temperature, which turns out to be
for the initial excess arsenic density of
Compact Dual-Wideband Bandpass Filter with Multimode Resonator
Liu, Haiwen ; Li, Shen ; Guan, Xuehui ; Ren, Baoping ; Lei, Jiuhuai ; Wang, Yan ;
ETRI Journal, volume 36, issue 1, 2014, Pages 163~166
DOI : 10.4218/etrij.14.0213.0097
A microstrip dual-wideband bandpass filter using a multimode resonator (MMR) is proposed in this letter. The proposed MMR loaded with a T-shaped open-ended stub and a short-ended stub exhibits triple mode characteristics, and a synthesis method is developed to illustrate the wide passband with independently controllable center frequencies and bandwidths. To verify this design methodology, a dual-wideband filter with fractional bandwidths of 19.1% and 27.9% is designed and fabricated. The measured results agree with the simulations.
Speech Denoising via Low-Rank and Sparse Matrix Decomposition
Huang, Jianjun ; Zhang, Xiongwei ; Zhang, Yafei ; Zou, Xia ; Zeng, Li ;
ETRI Journal, volume 36, issue 1, 2014, Pages 167~170
DOI : 10.4218/etrij.14.0213.0033
In this letter, we propose an unsupervised framework for speech noise reduction based on the recent development of low-rank and sparse matrix decomposition. The proposed framework directly separates the speech signal from noisy speech by decomposing the noisy speech spectrogram into three submatrices: the noise structure matrix, the clean speech structure matrix, and the residual noise matrix. Evaluations on the Noisex-92 dataset show that the proposed method achieves a signal-to-distortion ratio approximately 2.48 dB and 3.23 dB higher than that of the robust principal component analysis method and the non-negative matrix factorization method, respectively, when the input SNR is -5 dB.
Lowering Error Floor of LDPC Codes Using an Improved Parallel WBF Algorithm
Ma, Kexiang ; Li, Yongzhao ; Zhu, Caizhi ; Zhang, Hailin ; Zhang, Yuming ;
ETRI Journal, volume 36, issue 1, 2014, Pages 171~174
DOI : 10.4218/etrij.14.0213.0046
In weighted bit-flipping-based algorithms for low-density parity-check (LDPC) codes, due to the existence of overconfident incorrectly received bits, the metric values of the corresponding bits will always be wrong in the decoding process. Since these bits cannot be flipped, decoding failure results. To solve this problem, an improved parallel weighted bit flipping algorithm is proposed. Specifically, a reliability-saturation strategy is adopted to increase the flipping probability of the overconfident incorrectly received bits. Simulation results show that the error floor of LDPC codes is greatly lowered.
An Introduction to Energy-Based Blind Separating Algorithm for Speech Signals
Mahdikhani, Mahdi ; Kahaei, Mohammad Hossein ;
ETRI Journal, volume 36, issue 1, 2014, Pages 175~178
DOI : 10.4218/etrij.14.0213.0130
We introduce the Energy-Based Blind Separating (EBS) algorithm for extremely fast separation of mixed speech signals without loss of quality, which is performed in two stages: iterative-form separation and closed-form separation. This algorithm significantly improves the separation speed simply due to incorporating only some specific frequency bins into computations. Simulation results show that, on average, the proposed algorithm is 43 times faster than the independent component analysis (ICA) for speech signals, while preserving the separation quality. Also, it outperforms the fast independent component analysis (FastICA), the joint approximate diagonalization of eigenmatrices (JADE), and the second-order blind identification (SOBI) algorithm in terms of separation quality.
Fast Reference Frame Selection Method Based on Best Reference Frame Index Correlation
Kim, Hyungwook ; Lim, Sojeong ; Yu, Sungwook ;
ETRI Journal, volume 36, issue 1, 2014, Pages 179~182
DOI : 10.4218/etrij.14.0213.0394
This letter presents a very simple yet very effective solution for fast reference frame (RF) selection in H.264/AVC. By efficiently making use of the correlation between the best RF indices in various inter modes, the proposed method significantly reduces the number of RFs to be examined at the expense of a very small miss rate. Simulation results show that the proposed method not only improves upon the coding performance of conventional methods but also reduces the encoding time significantly.
A Distributed Implementation Algorithm for Physical Layer Security Based on Untrusted Relay Cooperation and Artificial Noise
Li, Xiangyu ; Wang, Xueming ; Xu, Xiangyang ; Jin, Liang ;
ETRI Journal, volume 36, issue 1, 2014, Pages 183~186
DOI : 10.4218/etrij.14.0213.0090
In this letter, we consider a cooperation system with multiple untrusted relays (URs). To keep the transmitted information confidential, we obtain joint channel characteristics (JCCs) through combining the channels from the source to the destination. Then, in the null space of the JCCs, jammers construct artificial noise to confuse URs when the source node broadcasts its data. Through a distributed implementation algorithm, the weight of each node can be obtained from its own channel state information. Simulation results show that high-level security of the system can be achieved when internal and external eavesdroppers coexist.