Cyclic Code Shift Research Articles

Performance Enhancement of Dynamic Cyclic Shift Code with Direct Detection and AND Subtraction Detection Technique of OCDMA

Optical code division multiple access system (OCDMA) has been important with increasing demands of high capacity and speed for communication in optical networks. Due to OCDMA technique high efficiency is achieved, hence fiber bandwidth is fully used .In this paper we will focus on DCS (Dynamic cyclic shift) code with their different detection technique using optiwave system design tool. Due to this codes we will eliminated MAI (multiple access interference) and improve BER (bit error rate) , PIIN( Phase induced intensity noise) and make orthogonality between users in the system .We will use two different detection technique i.e Direct detection technique and AND subtraction detection technique to implement the codes with different parameters. In this paper, the study of different parameters is based on conference a paper that is mainly demonstrated on an experiment to Enhancement a performance of DCS (Dynamic cyclic shift) code with there different parameter of OCDMA using optiwave system design tool.

CCSK 변조방식을 사용하는 LPD 시스템을 위한 동기 기법

In this paper, we propose an initial timing and frequency synchronization scheme for low probability detection (LPD) systems with cyclic code shift keying (CCSK). The performance of the LPD system with CCSK highly depend on initial timing and frequency offset. On the other hand, the operating SNR (Signal-to-Noise Ratio) of LPD systems is usually very low. Hence, to guarantee a reliable performance of the LPD system, it is crucial to develop suitable initial synchronization algorithms. In this paper, we propose an initial timing and frequency synchronization scheme suitable for CCSK based LPD system using a repeated preamble pattern.

Analysis and Simulation to the Anti-Jamming Performance of the CCSK Soft Spread Spectrum System

The soft spread spectrum realizes its function through the Cyclic Code Shift Keying (CCSK) which is not distinguished from the direct spread spectrum system (DSSS) in more literature. In this paper, the performance of the soft spread spectrum with the single-tone jamming is analyzed and simulated compared with DS. The conclusion is drawn that the capability of the anti-noise is obvious but declined seriously to the man-made interference.

TDCS-Based Cognitive Radio Networks with Multiuser Interference Avoidance

For overlay cognitive radio networks (CRNs), transform domain communication system (TDCS) has been proposed to support multiuser communications through spectrum bin nulling and frequency domain spreading. In TDCS-based CRNs, each user is assigned a specific pseudorandom spreading sequence. However, the existence of multiuser interference (MUI) is one of main concerns, due to the non-zero cross-correlations between any pair of TDCS signals. In this paper, a novel framework of TDCS-based CRNs with the joint design of sequences and modulation schemes is presented to realize MUI avoidance. With the uncertainty of spectrum sensing results in CRNs, we first introduce a unique sequence design through two-dimensional time-frequency synthesis and obtain a class of almost perfect sequences. That is, periodic auto-correlation and cross-correlations are identically zero for most circular shifts. These correlation properties are further exploited in conjunction with a specially-designed cyclic code shift keying in order to achieve the advantage of MUI avoidance. Numerical results demonstrate that the proposed TDCS-based CRNs are considered as preferable candidates for decentralized networks against the near-far problem.

Spectrally efficient transform domain communication system with quadrature cyclic code shift keying

Transform domain communication system (TDCS), as an overlay cognitive radio communication system, has been proposed to obtain a low probability of interception by using spectrum bin nulling to synthesise an adaptive waveform corresponding to the spectrum sensing output. However, its low spectral efficiency limits potential practical applications. In this study, an efficient modulation scheme, namely quadrature cyclic code shift keying (Q-CCSK), is proposed for TDCSs by generating another fundamental modulation waveform as the data-bearing quadrature branch. Although using Q-CCSK doubles the spectral efficiency for TDCSs, the instinct inter-branch interference arises from the added quadrature branch. Through the orthogonality analysis, it is proven that the two branches (in-phase and quadrature- branches) are still satisfied the property of quasi-orthogonality. Moreover, the performances of TDCSs employing Q-CCSK in additive white Gaussian noise (AWGN) and multipath fading channels are discussed, respectively. Analytical and simulation results demonstrate that, compared with conventional schemes, the TDCS employing Q-CCSK can double the spectral efficiency with comparable systematic performance.

A New Method for BCH Codes of Blind Recognition

According to the invariance property of the BCH code and Euclidean algorithm to calculate the greatest common factor (GCF) between code group and its cyclic shift code group. There is a method by using the degree distribution probability sum function of the greatest common factor to recognize the code length of BCH code. On this basis, the GCF can be extracted of the greatest degree distribution probability from the sum function, with the generator polynomial obtained by decomposing the GCF. The simulation results show that this method can achieve the recognition probability above 95% with BER of 4×10-3，and the high BER is much better to recognize the short codes.

A New Algorithm for Development of Dynamic Cyclic Shift Code for Spectral Amplitude Coding Optical Code Division Multiple Access Systems

This article presents a new code—the dynamic cyclic shift code—for spectral amplitude coding–optical code division multiple access systems. One of the important properties of the dynamic cyclic shift code is that the number of users can be increased without increasing the weight value. System performance was evaluated by using both theoretical analysis as well as the simulation experiment. The analysis results show that the proposed dynamic cyclic shift code can support more users in spectral amplitude coding–optical code division multiple access systems compared to spectral amplitude coding–optical code division multiple access codes. It was ascertained by performance evaluation that the dynamic cyclic shift code possesses ideal properties for use in spectral amplitude coding–optical code division multiple access systems.

순환천이변조 주파수도약대역확산/시분할다중접속 시스템의 성능 개선에 관한 연구

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. 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.

Enhancement of performance of a hybrid SAC-OCDMA system using dynamic cyclic shift code

A hybrid subcarrier multiplexing (SCM) technique incorporating spectral amplitude coding and optical code division multiple access (SAC-OCDMA) technologies is investigated using both numerical and simulation methods. The hybrid SCM/SAC-OCDMA system combines the two above schemes in such a way that it is robust to multiple access interference and reveals much enhanced channel data rate. We improve the overall performance of the hybrid SCM/SAC-OCDMA system based on spectral amplitude coding to suppress a number of impairments and improve its sensitivity at a bit error rate of 10 -9 . As a result, the system suggested by us, which is based on a dynamic cyclic shift code, shows better performance when compared with the standard SAC-OCDMA systems employing the conventional code.

Properties of orthogonal signals with direct spectrum spreading based on perfect binary matrices and the algorithm of their correlation processing

A fast algorithm has been developed for digital correlation processing (correlation reception) of orthogonal signals formed on the basis of perfect binary matrices (PBM) using a modified circuit of cyclic shift modulation—Cyclic Code Shift Keying (CCSK). In addition, the ensemble cross-correlation properties of orthogonal signals based on PBM were studied.

Cyclic code shift keying: a low probability of intercept communication technique

A low probability of intercept (LPI), or low probability of detection (LPD) communication technique known as cyclic code shift keying (CCSK) is described. We discuss the basic concepts of CCSK and describe a system based on the use of random or pseudorandom codes for biphase modulation. We use simulation to show that the bit error rate (BER) for CCSK can be closely estimated by using existing equations that apply to M-ary orthogonal signaling (MOS). Also, we show that significantly fewer computations are required for CCSK than for MOS when the number of bits per symbol is the same. We show that using biphase modulation results in waveforms that have a large time-bandwidth product and very low input signal-to-noise ratio (SNR) and thus inherently have an LPI by a radiometer. We evaluate detection by a radiometer and show that LPI can be achieved by using codes of lengths greater than about 2/sup 12/ (i.e., by transmitting more than about 12 bits per symbol). Results illustrate the effect that the CCSK symbol length and error probability, and the radiometer integration time and probability of false alarm (PFA), have on detection by a radiometer. We describe a variation of CCSK called truncated CCSK (TCCSK). In this system, the code of length 2/sup k/ is cyclically shifted, then truncated and transmitted. Although shortened, the truncated code still represents k bits of information, thus leading to an increased data rate. We evaluate radiometer detection of TCCSK and it is shown that the probability of detection is increased compared with the detection of CCSK.