共查询到20条相似文献,搜索用时 15 毫秒
1.
《Quantum Electronics, IEEE Journal of》2010,46(2):258-264
2.
Time synchronization is a critical component of the infrastructure of wireless sensor networks (WSN). In a high latency environment
such as underwater, traditional approaches to time synchronization have limited accuracy. A new method is describe for time
synchronization that takes into account clock skew, clock offset, and also propagation delay. Minimum message communication
is used as a performance measure of the quality of this new time synchronization protocol. 相似文献
3.
Effects of message encoding and decoding on synchronized chaotic optical communications 总被引:3,自引:0,他引:3
Shuo Tang Jia-Ming Liu 《Quantum Electronics, IEEE Journal of》2003,39(11):1468-1475
Chaotic optical communication at 2.5 Gb/s is experimentally investigated using three major encoding and decoding schemes, namely chaos shift keying (CSK), chaos masking (CMS), and additive chaos modulation (ACM). The effects of message encoding and decoding on the chaotic dynamics, the chaos synchronization, and the chaotic communication performance are compared among the three schemes. In the schemes of CSK and ACM, it is found that a small amount of message injected into the chaotic dynamics can increase the complexity of the chaotic state dramatically. In the CMS scheme, the chaotic dynamics are found not to be influenced by the encoded message. The synchronization quality deteriorates dramatically with an increase in the message strength in CSK and CMS. The ACM scheme is found to have the best synchronization quality among the three schemes when there is an encoded message. Message recovery is demonstrated for each of the three schemes. The ACM scheme is found to have the best communication performance. 相似文献
4.
Bogris A. Rizomiliotis P. Chlouverakis K.E. Argyris A. Syvridis D. 《Quantum Electronics, IEEE Journal of》2008,44(2):119-124
The feedback phase in a chaotic system consisting of a semiconductor laser subject to delayed optical feedback is considered for the first time as a secret key for secure chaotic communications not exclusively based on hardware uniqueness. Extensive numerical simulations illustrate that the feedback phase is of extreme importance as far as synchronization is concerned. The ability of an eavesdropper to attack the intensity-modulated message when a pseudorandom variation of the feedback phase is imposed at the transmitter's side is numerically quantified by bit-error-rate calculations. The analysis demonstrates that the eavesdropper is not able to synchronize and hence to extract the message when he is not aware of the phase variations even if he is equipped with an identical chaotic device. 相似文献
5.
Rhee Injong Warrier Ajit Min Jeongki Xu Lisong 《Mobile Computing, IEEE Transactions on》2009,8(10):1384-1396
This paper presents a distributed implementation of RAND, a randomized time slot scheduling algorithm, called DRAND. DRAND runs in O(delta ) time and message complexity where delta is the maximum size of a two-hop neighborhood in a wireless network while message complexity remains O(delta ), assuming that message delays can be bounded by an unknown constant. DRAND is the first fully distributed version of RAND. The algorithm is suitable for a wireless network where most nodes do not move, such as wireless mesh networks and wireless sensor networks. We implement the algorithm in TinyOS and demonstrate its performance in a real testbed of Mica2 nodes. The algorithm does not require any time synchronization and is shown to be effective in adapting to local topology changes without incurring global overhead in the scheduling. Because of these features, it can also be used even for other scheduling problems such as frequency or code scheduling (for FDMA or CDMA) or local identifier assignment for wireless networks where time synchronization is not enforced. We further evaluate the effect of the time-varying nature of wireless links on the conflict-free property of DRAND-assigned time slots. This experiment is conducted on a 55-node testbed consisting of the more recent MicaZ sensor nodes. 相似文献
6.
Yanhua Hong Min Won Lee Paul J. Spencer P.S. Shore K.A. 《Lightwave Technology, Journal of》2009,27(22):5099-5105
Chaotic message encoding and decoding in unidirectionally coupled vertical-cavity surface-emitting lasers (VCSELs) with polarization-preserved and polarization-selected optical injection has been studied experimentally. A GHz message has been successfully encoded in the chaotic transmitter and decoded from the receiver with polarization-preserved optical injection. In contrast decoding using polarization-selected optical injection was achieved at only 330 MHz. It has also been demonstrated that GHz message extraction can be achieved using both normal and inverse chaos synchronization thus providing an opportunity for exploiting polarization properties of VCSELs for duplexed chaotic message transmission. 相似文献
7.
首先研究了非相干光反馈同步系统内部参数失配对系统同步性能的影响,并与相干光反馈的完全同步系统以及广义同步系统进行了比较,其次研究了非相干光反馈采用三种不同的信号调制解调方式(CSK,CMS,ACM),对三种不同频率(250 MHz,2.5GHz和12.5GHz)的信号进行了调制解调。通过MATLAB仿真实验可知,非相干光反馈混沌同步系统相对于相干光反馈完全同步系统更易于实现,同时保留了一定的对参数失配的敏感特性,从而确保了该系统比相干光反馈广义同步具有更高的安全性;在信号解调时,CSK只能解调出250MHz信号,CMS能解调出2.5GHz信号,ACM能够解调出高达12.5GHz的信号。 相似文献
8.
Sivaprakasam S. Spencer P.S. Rees P. Shore K.A. 《Quantum Electronics, IEEE Journal of》2002,38(9):1155-1161
Chaotic synchronization is investigated experimentally using two diode lasers as transmitter and receiver. The transmitter laser is rendered chaotic by application of an optical feedback in an external-cavity configuration. Experimental conditions are found under which the synchronization diagram makes a transition from a positive to a negative gradient. A regime of operating conditions is identified in which the receiver laser is found to anticipate the dynamics of the transmitter laser. The anticipation time does not depend on the external-cavity length, but rather on the time of flight between the two lasers. Changes in the spectrum of the synchronized system are shown to be associated with the transition between anticipating and lag synchronization. 相似文献
9.
Sanchez-Diaz A. Mirasso C.R. Colet P. Garcia-Fernandez P. 《Quantum Electronics, IEEE Journal of》1999,35(3):292-297
We numerically study the synchronization of two chaotic semiconductor lasers in a master-slave configuration. To synchronize the lasers, a small amount of output power from the master laser is injected, after propagating through an optical fiber, into the slave laser. We show that the output of the master laser can be used as a chaotic carrier to encode a digital message which can be recovered after propagating long distances. We also check the robustness of this scheme when the two lasers are slightly different 相似文献
10.
Annovazzi-Lodi V. Aromataris G. Benedetti M. Cristiani I. Merlo S. Minzioni P. 《Photonics Technology Letters, IEEE》2007,19(22):1783-1785
Wavelength conversion in the transmission of a message masked by optical chaos is experimentally demonstrated. In our setup, chaos is generated by a distributed-feedback laser subject to delayed optical feedback, and hides a message by additive chaos masking. The optical wavelength is converted, along the transmission line, by four-wave mixing in a semiconductor optical amplifier. At the receiver, the message is extracted by master-slave synchronization. Our experiments demonstrate that secure communications based on chaos are compatible with channel switching as required in reconfigurable optical networks. 相似文献
11.
We numerically study the synchronization or entrainment of two unidirectional coupled single-mode semiconductor lasers in a master-slave configuration. The emitter laser is an external-cavity laser subject to optical feedback that operates in a chaotic regime. The receiver can either operate at a chaotic regime similar to the emitter (closed-loop configuration) or without optical feedback and consequently under continuous-wave conditions when it is uncoupled (open-loop configuration). We compute the degree of synchronization of the two lasers as a function of the emitter-receiver coupling constant, the feedback rate of the receiver, and the detuning. We find that the closed-loop scheme has, in general, a larger region of synchronization when compared with the open loop. We also study the possibility of message encoding and decoding in both open and closed loops and their robustness against parameter mismatch. Finally, we compute the time it takes the system to recover the synchronization or entrainment state when the coupling between the two subsystems is lost. We find that this time is much larger in the closed loop than in the open one. 相似文献
12.
13.
Polarization-preserved and polarization-rotated synchronization of chaotic vertical-cavity surface-emitting lasers 总被引:1,自引:0,他引:1
The synchronization process in a vertical-cavity surface-emitting laser (VCSEL) based master-slave configuration, where the master laser has been destabilised by optical feedback from an external mirror, has been investigated. The dynamics of both VCSEL polarization modes have been modeled and used to study the chaos synchronization mechanism in both polarization preserved, and polarization rotated unidirectionally coupled master and slave configurations. Two types of synchronization have been identified in the polarization rotated case, one of which may afford an opportunity to effect multiplexed message encoding using orthogonal laser modes. 相似文献
14.
Unidirectional chaotic synchronization between two remote injection-locked semiconductor lasers to achieve chaotic communications is investigated numerically. Different from the direct chaotic masking methods, the chaotic carrier wave is generated from different chaotic states in transience instead of a fixed chaotic state in static to prevent it from being reproduced through a reconstructed embedding phase space. The testing digital and sinusoidal message signals in the gigahertz range can be easily recovered without the use of any electronic or optical filter to filter out the synchronization error. The robustness of synchronization is examined by using the intrinsic white noise of the transmitter and the receiver as the perturbation. The effects of parameter mismatches on the quality and robustness of synchronization are analyzed in detail. The results show that different internal parameters have very different tolerances for parameter mismatch. A short discussion on the phase sensitivity of synchronization is also given 相似文献
15.
Demultiplexing chaos from multimode semiconductor lasers 总被引:3,自引:0,他引:3
We show numerically that the injection of two chaotic modes of a multimode semiconductor laser with optical feedback into two single-mode stand-alone semiconductor lasers leads to chaotic synchronization between the respective intensities. The effect of parameter mismatch between the transmitter and receiver lasers is examined, and it is concluded that the observed synchronization is a consequence of injection locking. Under these conditions, the possibility of using this demultiplexing scheme for message transmission is examined. 相似文献
16.
为了研究多信道全光混沌通信系统中信道串扰对系统同步及解码性能的影响,构建了基于垂直腔面发射激光器的多信道混沌通信系统模型.通过利用描述其特性的数率方程模型,采用相似指数作为参考标准来评价同步性能,并进行了2.5Gbit/s混沌掩藏方式的编解码数值模拟.结果表明,相对注入强度越小,信道间隔越大,系统同步的性能越好;双信道系统的同步质量相比主从式单信道系统会有明显下降,而进一步增加信道数量,同步品质并不发生显著改变.在同步质量足够高时,信号可以得到较好的恢复. 相似文献
17.
Rees P. McEvoy P. Valle A. O'Gorman J. Lynch S. Landais P. Pesquera L. Hegarty J. 《Quantum Electronics, IEEE Journal of》1999,35(2):221-227
The potential for using inexpensive compact disc laser diodes as optical clock extraction elements in transparent networks has led to an increase in research into the dynamics of self-pulsating laser diodes. We use a rate-equation model to simulate the synchronization of the self-pulsating laser output pulses to a periodic optical signal, In particular, we investigate the time it takes for the laser to synchronize to the input signal and also, the time taken for the laser to unlock when the signal is removed. The effect of varying the power of the optical signal and the detuning of the input signal frequency relative to the laser's self-pulsation frequency are determined. Our results enable us to identify important issues which need to be addressed when a self-pulsating laser diode is used in a clock extraction subsystem, In particular, we find that the signal frequency and laser free-running frequency must be as close as possibility to minimize errors. Also, the higher the signal power the quicker the laser synchronizes to the signal, although we find that if the power becomes too large the laser can no longer lock, which would cause a significant increase in detection errors 相似文献
18.
延时反馈双环掺铒光纤激光器互注入系统中的混沌同步研究 总被引:1,自引:1,他引:0
分析了延时反馈双环掺铒光纤(EDF)激光器互注入 系统的动态特性,并引入一种量化时间序列复杂度的评 价方法——排列熵(PE,permutation entropy),对激光器输出状 态和混沌同步质量与复杂度的关系进行讨论。研究表明,通过调节反馈 延迟时间和反馈强度可控制系统的输出状态,使系统输出为周期态和混沌态,而且利用PE熵计算激光器 输出信号的复杂度相对于分岔图同样能直观准确的反映出系统动态行为;在激光器独立工作 情况下,输出 信号的混沌区域内夹杂有较多的周期态,而在互注入情况下,混沌区域增宽且较为平坦,同 时输出信号复 杂度的PE值较高,互注入系统有利于参数选择的范围和提高混沌通信系统的安全性;提 高注入强度可 得到高质量的混沌同步,两个激光器在同步和不同步时输出信号的复杂度是 不同的,可见 研究激光器输出信号的复杂度可成为分析混沌同步质量的一种参考。 相似文献
19.
基于双区半导体激光器的速率方程,研究了双区半导体激光器的超混沌现象,给出了双区半导体激光器产生超混沌的条件;利用驱动-响应法实现了双区半导体激光器的超混沌同步,通过计算激光系统最大条件李亚谱诺夫指数随注入强度的变化,得到实现超混沌同步的注入参量的取值范围. 相似文献
20.
Synchronized chaotic optical communications at high bit rates 总被引:7,自引:0,他引:7
Jia-ming Liu How-foo Chen Shuo Tang 《Quantum Electronics, IEEE Journal of》2002,38(9):1184-1196
Basic issues regarding synchronized chaotic optical communications at high bit rates using semiconductor lasers are considered. Recent experimental results on broadband, high-frequency, phase-locked chaos synchronization, and message encoding-decoding at 2.5 Gb/s are presented. System performance at a bit rate of 10 Gb/s is numerically studied for the application of three encryption schemes, namely chaos shift keying, chaos masking, and additive chaos modulation, to three chaotic semiconductor laser systems, namely the optical injection system, the optical feedback system, and the optoelectronic feedback system. By causing synchronization error in the forms of synchronization deviation and desynchronization bursts, the channel noise and the laser noise both have significant effects on the system performance at high bit rates. Among the three laser systems, the optoelectronic feedback system has the best performance while the optical feedback system has the worst. Among the three encryption schemes, only the performance of additive chaos modulation with low-noise lasers is acceptable at high bit rates. 相似文献