Generalized Self Spread-Spectrum Communications with Turbo Soft Despreading and Decoding

Tomasin Stefano,Veronesi Daniele The Korea Institute of Information and Commucation 2006 Journal of communications and networks Vol.8 No.3

Self-spreading (SSP) is a spread spectrum technique where the spreading sequence is generated from data bits. Although SSP allows communications with low probability of interception by unintended receivers, despreading by the intended receiver is prone to error propagation. In this paper, we propose both a new transmitter and a new receiver based on SSP with the aim to a) reduce error propagation and b) increase the concealment of the transmission. We first describe a new technique for the generation of SSP spreading sequence, which generalizes SSPs of existing literature. We include also coding at the transmitter, in order to further reduce the effects of error propagation at the receiver. For the receiver, we propose a turbo architecture based on the exchange of information between a soft despreader and a soft-input soft-output decoder. We design the despreader in order to fully exploit the information provided by the decoder. Lastly, we propose a chip decoder that extracts the information on data bits contained in the spreading sequence from the received signal. The performance of the proposed scheme is evaluated and compared with existing spread-spectrum systems.

Validity of Ocean Wave Spectrum Using Rayleigh Probability Density Function

Choi, Young Myung,Yang, Young Jun,Kwon, Sun Hong Korean Society of Ocean Engineers 2012 International journal of ocean system engineering Vol.2 No.4

The distribution of wave heights is assumed to be a Rayleigh distribution, based on the assumption of a narrow band and Gaussian distribution of wave elevation. The present study was started with doubts about the narrow band assumption. We selected the wave spectra widely used to simulate irregular random waves. The wave spectra used in this study included the Pierson-Moskowitz spectrum, Bretschneider-Mitsuyasu spectrum, and JONSWAP spectrum. The directionality of the waves was considered. The cosine 2-l type directional spreading function and mixed form of the half-cosine 2-s type with Mitsuyasu type directional spreading are considered here to investigate the effects of a directional spreading function on random waves. The simulated wave height distribution is compared with a Rayleigh distribution.

전력전자변환기에 적용된 Chaos PWM 기법의 스펙트럼 확산에 관한 연구

한근우,김준형,정영국 한국조명.전기설비학회 2022 조명·전기설비학회논문지 Vol.36 No.5

In this study, the power spectrum of the random PWM technique using the Linear Congruential Generator (LCG) and the PWM technique with chaotic logistic, tent and double tent map characteristics were compared with the fixed frequency switching PWM technique. The random technique generates random numbers using LCG, and the chaos number is generated using each chaos map, and a bifurcation tree with a=4.0 and λ=0.99 conditions in which a complete chaos state exists in the ranges of 0 and 1 is used. In order to prove the validity of this study, a DSP-based power electronics converter for driving a three-phase induction motor was manufactured. As a result, the chaos logistic map and tent map were limited in the spread of broadband in the spectrum of power electronics converters. However, the advanced chaos double tent map was similar to the excellent spectrum spread performance of the Random PWM technique by LCG. Harmonic Spread Factor(HSF) of the output voltages of each technique were measured according to the increase in the modulation index, and the chaos double tent map and random technique were very advantageous from the viewpoint of HSF.

A Spread Spectrum Clock Generator with Dual-tone Hershey-Kiss Modulation Profile

Seongho Kim,Taek-Joon An,Yongwoo Kim,Jin-Ku Kang 대한전자공학회 2023 Journal of semiconductor technology and science Vol.23 No.1

This paper presents a spread spectrum clock generator (SSCG) using a dual-tone Hershey-Kiss modulation profile. The modulation controller has two up/down counters and one delta-sigma modulator, and the output of the modulation controller is provided to a multi-modulus divider in a fractional-N PLL. The proposed SSCG is designed to operate in either single-tone modulation mode or dual-tone modulation mode. Once the targeted modulation frequency and spread ratio are given, the design variables for the SSCG can be controlled digitally. The proposed SSCG was designed and fabricated using the 65 nm CMOS process and consumes 8.5 mW while generating a 5 GHz spectrum-spread clock signal with 1.2 V supply voltage. After all design parameters are set for a 0.5% spread ratio using 30 and 33 kHz modulation frequencies, the measured EMI reduction is 24.6 dB while single-tone modulation is applied and 28.7 dB while dual-tone modulation is applied.

Spread current spectrum method based on model predictive control with double sampling

Sanghun Han,Seungil Choi,Younghoon Cho 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.1

This paper proposes a model predictive control (MPC) with a double-sampling technique to spread the current spectrum. Finite control set MPC has the characteristic of a switching frequency that fluctuates. Thus, the components of the switching frequency and harmonics are reduced in the current spectrum. When MPC is utilized to control current, virtual vectors are added to ensure a low current total harmonic distortion (THD). However, increasing the voltage vector reduces the switching frequency variation, which leads to degradation of the spread-spectrum performance. The proposed method allows MPC to have an additional feature to change the harmonic components while reducing the current THD. To verify the proposed scheme, a comparison of its performance according to the sampling techniques and number of the voltage vectors has been conducted. The simulation and experimental results demonstrate the effectiveness of the proposed method.

Self-Encoded Spread Spectrum and Turbo Coding

Jang, Won-Mee,Nguyen, Lim,Hempel, Michael The Korea Institute of Information and Commucation 2004 Journal of communications and networks Vol.6 No.1

Self-encoded multiple access (SEMA) is a unique realization of random spread spectrum. As the term implies, the spreading code is obtained from the random digital information source instead of the traditional pseudo noise (PN) code generators. The time-varying random codes can provide additional security in wireless communications. Multi-rate transmissions or multi-level grade of services are also easily implementable in SEMA. In this paper, we analyze the performance of SEMA in additive white Gaussian noise (AWGN) channels and Rayleigh fading channels. Differential encoding eliminates the BER effect of error propagations due to receiver detection errors. The performance of SEMA approaches the random spread spectrum discussed in literature at high signal to noise ratios. For performance improvement, we employ multiuser detection and Turbo coding. We consider a downlink synchronous system such as base station to mobile communication though the analysis can be extended to uplink communications.

직접 대역 확산 시스템을 위한 톤 간섭 제거 알고리듬

이용욱(Yongwook Lee),강동훈(Donghoon Kang),박효배(Hyobae Park),오왕록(Wangrok Oh) 大韓電子工學會 2009 電子工學會論文誌-TC (Telecommunications) Vol.46 No.8

본 논문에서는 직접 대역 확산 (direct-sequence spreading spectrum) 시스템을 위한 주파수 영역 톤 간섭 (tone interference) 제거 알고리듬을 제안한다. 기존에 제안된 주파수 영역 톤 간섭 제거 기법들에서는 FFT (Fast Fourier Transform)를 이용하여 수신 신호를 주파수 영역 신호로 전환한 다음 간섭 신호를 제거하고 그 결과로 얻어진 주파수 영역신호를 IFFT (inverse FFT)를 이용하여 시간 영역 신호로 변환한 후 나머지 수신 과정을 수행한다. 본 논문에서 제안하는 간섭 신호 제거 기법은 주파수 영역으로 변환된 수신 신호에서 간섭 신호에 해당하는 주파수 영역 신호만을 추출하고 그 추출된 신호에 대한 시간 영역 신호를 생성하여 수신 신호에서 제거하는 방법을 사용한다. 따라서 기존의 주파수 영역 간섭 제거 기법들에서 요구되는 IFFT 수행에 필요한 하드웨어 복잡도 (hardware complexity)를 크게 줄일 수 있는 장점이 있다. In this paper, we propose a frequency-domain tone interference cancellation algorithm for direct-sequence spread spectrum systems. In the previously proposed frequency-domain interference cancellation algorithms, the interference signal is estimated and compensated in the frequency-domain and then, with IFFT (inverse Fourier transform), the compensated frequency-domain signal is transformed to the time domain signal for the remaining receiver operations. Unlike the previous works, the proposed algorithm does not requires IFFT and thus, the proposed algorithm not only shows the virtually identical performance but also requires lower hardware complexity compared to the previous works.

A Double-Hybrid Spread-Spectrum Technique for EMI Mitigation in DC-DC Switching Regulators

Gamal M. Dousoky,Masahito Shoyama,Tamotsu Ninomiya 전력전자학회 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.4

Randomizing the switching frequency (RSF) to reduce the electromagnetic interference (EMI) of switching power converters is a well-known technique that has been previously discussed. The randomized pulse position (RPP) technique, in which the switching frequency is kept fixed while the pulse position (the delay from the starting of the switching cycle to the turn-on instant within the cycle) is randomized, has been previously addressed in the literature for the same purpose. This paper presents a double-hybrid technique (DHB) for EMI reduction in dc-dc switching regulators. The proposed technique employed both the RSF and the RPP techniques. To effectively spread the conducted-noise frequency spectrum and at the same time attain a satisfactory output voltage quality, two parameters (switching frequency and pulse position) were randomized, and a third parameter (the duty ratio) was controlled by a digital compensator. Implementation was achieved using field programmable gate array (FPGA) technology, which is increasingly being adopted in industrial electronic applications. To evaluate the contribution of the proposed DHB technique, investigations were carried out for each basic PWM, RPP, RSF, and DHB technique. Then a comparison was made of the performances achieved. The experimentally investigated features include the effect of each technique on the common-mode, differential-mode, and total conducted-noise characteristics, and their influence on the converter’s output ripple voltage.

MTJ Performance Analysis of Hybrid DS/SFH Spread-Spectrum System using MSK or QPSK Modulation over Rayleigh Fading Channel

Ryu, Heung-Gyoon,Chung, Byung-Ki The Korean Institute of Electromagnetic Engineerin 2002 한국전자파학회논문지 Vol.13 No.5

Performance analysis and comparison of the hybrid DS-SFH spread-spectrum (SS) system using coherent MSK and QPSK modulation techniques over Rayleigh fading channel are considered in the presence of MTJ(multi-tone jamming). To analyze the BER performance of the hybrid systems with or without the Rake receiver, signal-to-noise plus interference ratio is derived as a function of the average signal-to-noise ratio, the jammer-to-signal ratio and other system parameters. Numerical results show that the performance difference between the two modulation schemes, MSK and QPSK, is negligible for low JSR, while it becomes significant with the increase of JSR. In multi-path Rayleigh fading channel without Rake receiver, the performances of the two modulation schemes are slightly improved as the DS spreading gain is increased when the total SS bandwidth is fixed. In particular, there is an optimum DS spreading gain for large JSR, in which a minimum BER is achieved, while only DS spreading gives the best performance for small JSR. For hybrid systems with Rake receiver, it is shown that the hybrid system of the MSK modulation scheme provides better anti-jamming performance and larger performance improvement with the increase of multi-path resolution capability of Rake receiver than that of QPSK modulation for all conditions. 다중톤 재밍이 있는 경우, 레이리 페이딩 채널상에서 MSK 혹은 QPSK 변조 방식을 사용하는 하이브리드 DS/SFH 확산 스펙트럼 시스템의 성능분석과 비교를 연구한다. 신호대 잡음비, 재머전력재 신호전력비(JSR) 그리고 기타 시스템 파라미터를 이용하여 신호대 잡음과 간섭비(SNIR)를 유도하여 Rake 수신기가 있을 때와 없을 때의 BER 성능을 분석한다. 수치 분석 결과, 재머전력재 신호전력비(JSR)가 작을 때는 MSK와 QPSK 변조 방식 사이의 성능은 별차이가 없으나, 재머전력재 신호전력비(JSR)가 커짐에 따라서 큰 성은의 차이가 나타난다. Rake 수신기가 없을 때는 DS 처리 이득이 커짐에 따라서 두 변조 방식의 성능이 약간씩 개선된다. 재머전력재 신호전력비(JSR)가 작을 때는 DS 처리이득만이 최선의 성능을 좌우하지만, 재머전력재 신호전력비(JSR)가 클 때는 BER을 최소시키는 최적의 DS처리이득이 있다. Rake 수신기가 있는 경우에는, 모든 조건에서 MSK변조방식을 사용하는 하이브리드 DS/SFH 확산 스펙트럼 시스템이 QPSK 변조 방식을 사용하는 경우보다 항재밍 성능이 강하고 더 큰 성능 개선이 있음을 보인다.

순환천이변조 주파수도약대역확산/시분할다중접속 시스템의 성능 개선에 관한 연구

김은철,김승춘,이형근,Kim, Eun-Cheol,Kim, Seung-Chun,Lee, Hyung-Keun 한국전기전자학회 2012 전기전자학회논문지 Vol.16 No.1

In this paper, we propose to employ a ternary sequence as a cyclic code shift keying (CCSK) modulation sequence. And we simulate the performance in a frequency hopping spread spectrum/time division multiple access (FHSS/TDMA) system with CCSK. Wireless channel is modeled as Rayleigh fading channel. From the simulation results, it is demonstrated that the system adopting the ternary sequence as a CCSK sequence has higher performance than that with a random sequence. 본 논문에서는 순환천이변조 (CCSK: cyclic code shift keying) 시퀀스로 삼진 시퀀스를 적용하는 것을 제안하였다. 그리고 순환천이변조를 적용한 주파수도약대역확산/시분할다중접속 (FHSS/TDMA: frequency hopping spread spectrum/time division multiple access) 시스템에서 성능을 모의실험 하였다. 실험에서 무선 채널은 레일레이(Rayleigh) 페이딩 채널로 모델링하였다. 모의 실험 결과로부터 순환천이변조 시퀀스로 무작위 시퀀스를 사용한 시스템보다 삼진 시퀀스를 적용한 시스템이 더 높은 성능을 보이는 것이 증명되었다.