Better Binary List Decodable Codes Via Multilevel Concatenation

A polynomial time construction of binary codes with the currently best known tradeoff between rate and error-correction radius is given. Specifically, linear codes over fixed alphabets are constructed that can be list decoded in polynomial time up to the so-called Blokh–Zyablov bound. The work builds upon earlier work by the authors where codes list decodable up to the Zyablov bound (the standard product bound on distance of concatenated codes) were constructed. The new codes are constructed via a (known) generalization of code concatenation called multilevel code concatenation. A probabilistic argument, which is also derandomized via conditional expectations, is used to show the existence of inner codes with a certain nested list decodability property that is appropriate for use in multilevel concatenated codes. A “level-by-level” decoding algorithm, which crucially uses the list recovery algorithm for the outer folded Reed–Solomon codes, enables list decoding up to the designed distance bound, aka the Blokh–Zyablov bound, for multilevel concatenated codes.      

On the Performance of Chaos-Based Multicode DS-CDMA Systems

Multicode DS-CDMA systems assign more than one spreading sequence to each of the users. In these systems multiple access interference (MAI) is made of a synchronous and an asynchronous component. It is well known that asynchronous MAI alone can be minimized by means of chaos-based spreading. Here we address the trade-off between synchronous and asynchronous MAI by tuning the autocorrelation profile of the chaosbased spreading codes. Improvements in the number of users allowed in the system is demonstrated in certain load conditions with respect to the classical approach of providing each user with a set of orthogonal sequences taken from an i.i.d. process.     

适用于串行级联结构的广义递归网格空时码设计

该文结合网格空时码(STTC)和分层空时码(BLAST)的优点,利用多个高码率卷积码,设计了一类适用于串行级联结构的广义递归STTC(G-RSTTC)。相比于传统以递归STTC为内码的串行级联空时码(SCSTC),其数据速率可随发送天线数增加而线性增加;相比于以BLAST为内码的SCSTC,基于G-RSTTC的SCSTC可获得更大的分集增益和编码增益。     

Serial Concatenation of Space‐Time and Recursive Convolutional Codes

We propose a new serial concatenation scheme for space‐time and recursive convolutional codes, in which a space‐time code is used as the outer code and a single recursive convolutional code as the inner code. We discuss previously proposed serial concatenation schemes employing multiple inner codes and compare them with the new one. The proposed method and the previous one with joint decoding, both performing a combined decoding of the simultaneous output signals from multiple antennas, give a large performance gain over the separate decoding method. In decoding complexity, the new concatenation scheme has a lower complexity compared with the multiple encoding/joint decoding scheme due to the use of the single inner code. Simulation results for a communication system with two transmit and one receive antennas in a quasi‐static Rayleigh fading channel show that the proposed scheme outperforms the previous schemes.     

Performance of Chaos-Based Digital Communication Systems in the Presence of a Pulsed-Noise Jammer

Chaos-based communication systems are known to offer advantages that are shared by spread-spectrum communications. One important aspect of the performance of any spread-spectrum communication system is the ability to resist jamming. In this paper, an analysis of the antijamming performance of a coherent chaos shift keying system under the influence of a common pulsed-noise jammer is presented. Two types of pulsed-noise jammers, slowly switching and fast switching jammers, are considered in our studies. The performance is evaluated in terms of the bit error rate (BER) under different levels of noise power, jamming power, spreading factor, and duty factor. The maximum (worst-case) BERs are also obtained analytically for the case where the jammer is slowly switching. Computer simulations are performed to verify the analytical results. Finally, the BERs are compared with those of a conventional direct-sequence spread-spectrum communication system.     

On the Performance Analysis of Digital Modulations in Generalized-K Fading Channels

In this paper we present novel expressions for several performance metrics of communication systems operating over a composite fading environment modelled by the generalized-K distribution. Initially, for a generalized-K fading channel with arbitrary values for the small and large-scale fading parameters we derive a closed-form expression for the moment generating function (MGF) of the received signal-to-noise ratio (SNR) and utilize it to obtain the exact average symbol error probability for a variety of digital modulations using the MGF based approach. Then, for integer values of the small-scale fading parameter, we derive a novel closed-form expression for the cumulative distribution function of the received SNR, which is then used to obtain closed-form expressions for the outage probability, the average bit error probability of various digital modulations, and the ergodic capacity of the generalized-K fading channel.     

通过USS协议实现变频调速器与PLC的通讯控制

以前的控制设备中西门子可编程控制器S7-200与变频调速器之间的控制大多是通过并口连接的,西门子S7-200 PLC不能实时读取和设置变频调速器的参数。采用USS协议作为通信链路进行数字化的信息传递,从而实现实时读取和设置变频调速器的相关参数,通讯速率可达187.5 kb/s。通信介质采用RS 485屏蔽双绞线,可有效地减少电缆的数量,提高了系统的自动化水平及运行的可靠性。     

串行干扰抵消器性能分析

结合工程实际,系统、全面地考虑了可能影响串行干扰抵消器性能的各个因素。对基于信号重构的串行干扰抵消器的性能进行了理论分析,得到了干扰抑制比与干扰信号载波相位估计方差、幅度估计方差、信道估计方差、定时估计方差以及误码率的关系表达式。结论可作为设计串行干扰抵消器时选择具体的参数估计算法及进行算法参数设计的理论依据。     

Performance of Direct-Oversampling Correlator-Type Receivers in Chaos-Based DS-CDMA Systems Over Frequency Non-selective Fading Channels

Wireless Personal Communications - In this paper, we present a study on the performance of direct-oversampling correlator-type receivers in chaos-based direct-sequence code division multiple access...     

MC-PSK在远程水声通信中的应用及其性能仿真

介绍了基于多载波-相移键控(MC-PSK)调制在远程水声通信系统中的应用,并对调制过程中的相关参数进行了分析比较,最后通过仿真得到了一系列有用结论。     

Lightweight Chaos-Based Nonlinear Component of Block Ciphers

Chaos influence different fields of science and technology. The development of sciences is at peak expected to the rapid broadcast of information with the smart machine in constrained resources atmosphere. With the help of our smartphone, we can easily access the information within no time and with much ease. This ease makes our information open and can be accessed from the web or misuse by any person. To secure our information on the internet of things (IOTs), lightweight cryptographic algorithms were introduced. We offered an efficient lightweight confusion component scheme constructed on the composition of chaotic iterative maps. The proposed chaotic lightweight substitution box (S-box) offers decent cryptographic characteristics. The suggested chaotic S-box is used for adding a confusion layer in small lightweight block cipher algorithms. The outcome of cryptographic characteristics displays that the anticipated chaotic Substitution box is appropriate for the lightweight block cipher in a constrained source environment.

     

Performance of Coherent Phase and Amplitude Digital Modulations with Carrier Recovery Noise

A model of decision feedback carrier recovery noise is presented as a function of the number of symbols over which the carrier is derived. For this model, quantitative results for performance degradation in BPSK, QPSK, 8-phase, 16-QAM, 32-QAM, and 64-QAM coherent demodulators are presented. When the carrier is derived from only the last symbol, these results reduce to the performance for differential detection. Carrier integration over 100 symbols is shown to be adequate to provide performance quite close to ideal for all the modulations considered.     

空心硅通孔的设计及其传输性能

硅通孔(TSV)能够实现信号的垂直传输,是微系统三维集成中的关键技术,在微波毫米波领域,硅通孔的高频传输特性成为研究的重点。针对微系统三维集成中,无源集成的硅基转接板的空心TSV垂直传输结构低损耗的传输要求,进行硅通孔的互连设计和传输性能分析。采用传输线校准方式,首先在硅基转接板上设计TSV阵列接地的共面波导(CPW)传输线和带TSV过孔的传输结构,并分别进行仿真分析,计算得出带TSV过孔的传输结构的插入损耗;然后通过后道TSV工艺,在硅基转接板上制作传输线和带TSV过孔的传输结构,用矢量网络分析仪法测试传输线和带TSV过孔的传输结构的插入损耗;最后计算得到单个TSV过孔的插入损耗,结果显示在0.1～30 GHz频段内其插入损耗S21≤0.1 dB,实现了基于TSV的低损耗信号传输。     

玻璃通孔的高频传输性能

随着玻璃通孔(TGV)制作工艺的成熟,微波毫米波系统采用玻璃基板进行集成,其高频传输特性成为研究的重点.对玻璃通孔的互连设计、制作和传输性能进行研究.在玻璃基板上分别设计直通传输线和带两个TGV、等长传输线的TGV传输结构;通过激光改性、腐蚀扩孔和电镀填充的TGV工艺制作技术以及薄膜电路布线技术,在玻璃基板上制作直通传...     

基于混沌的高速真随机数发生器的设计与实现

选取分段线性的混沌表达式来设计真随机数发生器,具体分析了表达式中参数对迭代产生的序列的影响,并给出了最佳的参数选择范围.真随机数发生器由模拟电路实现,整个电路由八级结构相同的子电路和一级抗饱和电路构成.每级子电路都由运算电路和采样/保持电路两部分组成,同时,分析了它们的工作过程和仿真结果.介绍了如何在开关电容电路中消除电荷注入对电路的影响.所设计的真随机数发生器芯片采用TSMC的0.25μm,mixed signal的工艺进行流片,芯片面积为2.34mm2,并完成了对芯片的测试工作.     

Improved Phase-Locked Loop Performance Via Nonlinear Loop Filters

A new structure for the loop filter of a PLL which consists of a conventional linear first order filter connected in a feedback arrangement with a static nonlinearity is analyzed. In the absence of noise, the steady state operating conditions (i.e., equilibrium points) are independent of the parameters of the nonlinearity, and asymptotic stability of the PLL for sufficiently small frequency detuning is established independent of the initial conditions of the VCO. Due to the nonlinearity, the resulting performance of the PLL during the acquisition node is greatly improved with little resulting loss in the narrowband filtering capability of the loop. Using Volterra methods, an explicit expression for the variance of the phase error for a cubic nonlinearity is developed which compares favorably with simulation studies.     

Performance Analysis of Serial and Parallel Six-Port Modulators

We have derived the transfer functions for two types of six-port quadrature phase-shift keying (QPSK) modulators and investigated their performances in terms of carrier leakage, Gray mapping, and conversion efficiencies. Our result shows that the carrier leakage is minimized when $Gamma_{rm ON} =-Gamma_{rm OFF}$. In addition, our analysis reveals here that only the parallel six-port QPSK modulator demonstrates a Gray mapping feature. Our analysis further proves that the serial and parallel modulator give a maximum conversion efficiency of 100% and 50%, respectively, but the efficiency of the serial modulator deteriorates faster than the parallel modulator when the terminations are not ideal. We have also shown that the serial modulator requires tighter design tolerances due to its cascaded topology. Our theoretical and measured results show good agreements with the six-port modulators developed for 4.2 GHz.      

Performance of OOK and Low-Order PPM Modulations in Optical Communications When Using APD-Based Receivers

This correspondence compares OOK and low-order PPM signaling formats in terms of bit error probabilities versus required signal counts per bit. The results show that QPPM requires 3 dB less signal than OOK, while BPPM requires the same or slightly more than OOK for the same performance. Optimum APD gain values are from 200 to 400. When using QPPM,k_{eff} = 0.006, and optimum gain, 60 signal counts/bit are required at 500 Mbits/s for a 10^-6bit error probability.     

Improving the Performance of New Product Teams

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