• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.11
• /
• pp.2991-3000
• /
• 1996

In this paper, an effective neural acquisition system is suggested for acquisition of the DS/SS communication system. The suggested system uses a binary neural network which geometrically analyzes and learns a given PN sequence in the binary field. the probabilities of detection and false alarm are obtained and are compared to simulation values. The equation of the mean acquisition time is derived and is compared to the doubledwell time of the serial serial search system. The significant improvement of the performance is demonstrated. As the length of synchronization sequence becomes longer and the number is increased, the performance is improved.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.10C
• /
• pp.995-1006
• /
• 2003

It is well know that in the wireless communication systems the transmitted signals can suffer from multipath fading due to the wave propagation characteristics and the obstacles over the paths, resulting in serious reduction in the power of the received signals. However, it is possible to take advantage of the inherent diversity imposed in the multipath reception if the underlying channel can be properly estimated. One of the diversity reception methods in this case is Rake processing. In this paper we study the Rake receivers for the direct-sequence spread-spectrum communication systems utilizing PN (pseudo noise) sequences to achieve spread spectrum. A conventional Rake receiver can use the finite-duration impulse (FIR) filter followed by the PN sequence demodulator, where the FIR filter coefficients are the reverse-ordered complex conjugate values of the fading channel impulse response estimates. Here, we propose a new Rake processing method by replacing the aforementioned PN code sequence with a new set of optimum demodulator coefficients. More specifically, the concept of the new optimum Rake processing is first introduced and then the optimum demodulator coefficients are theoretically derived. The performance obtained using the new optimum Rake processing is also calculated. The analytical results are verified by computer simulation. As a result, it is shown that the new optimum Rake processing method improves the MSE performance more than 10 dB over the conventional one using the fixed PN sequence demodulator. It is also shown that the new optimum Rake processing method improves the MSE performance about 10 dB over the Adaptive Correlator that performs the combining of the multipath components and PN demodulation concurrently. And finally, the MSE performance of the optimum Rake demodulator is very close to the MSE performance of OPSK demodulator under the AWGN channel.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39A no.11
• /
• pp.637-644
• /
• 2014

This paper investigates the detection performance of fault location using STDR(sequence time domain reflectometry) and SSTDR(spread spectrum time domain reflectometry) with various length and types of sequences, and then, proposes an improved detection technique by eliminating the injected signal in SSTDR. The detection error rates are compared and analyzed in power line channel model with various fault locations, fault types, and spreading sequences such as m-sequence, binary Barker sequence, and 4-phase Frank sequence. It is shown that the proposed technique is able to improve the detection performance obviously when the reflected signal is weak or the fault location is extremely close.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.5C
• /
• pp.555-560
• /
• 2009

A vehicle radar has been studied to avoid the collision of vehicles. A vehicle radar using direct sequence-ultra wideband (DS-UWB) measures the distance between a vehicle and an objective with a sufficient time margin. Therefore, the receiver should estimate the distance by processing the short UWB pulse rapidly. There have been several investigations for distance measuring based on DS-UWB signals. In this paper, we propose a novel method for rapid measuring processing time. Simulation results show that the proposed method has a shorter processing time than the conventional method.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.10C
• /
• pp.967-983
• /
• 2003

In wireless spread-spectrum communication systems utilizing PN (pseudo noise) sequences, a variety of noise sources from the channel affect the data reception performance. Among them, in this paper we are concerned with the narrowband interference that may arise from the use of the spectral bands overlapped by the existing narrowband users or the intentional jammers as in military communication. The effect of this interference can be reduced to some extent at the receiver with the PN demodulation by processing gain. It is known, however, that when the interferers are strong, the reduction cannot be sufficient and thereby requiring the extra use of narrowband interference cancellers (NIC's) at the receivers. A class of adaptive NIC's are studied here based on different two cost functions. One is the chip mean-squared error (MSE) computed prior to the PN demodulation and used in the conventional cancellers. Since thses conventional cancellers should be operated at the chip rate, the computational requirements are enormous. The other is the symbol MSE computed after the PN demodulation in which case the weights of the NIC's can be updated at a lot lower symbol rate. To compare the performance of these NIC's, we derive a common measure of performance, i.e., the symbol MSE after the PN demodulation. The analytical results are verified by computer simulation. As a result, it is shown that the cancellation capability of the symbol-rate NIC's are similar or better than the conventional one while the computational complexity can be reduced a lot.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.3C
• /
• pp.226-233
• /
• 2007

In this paper, we construct new LCZ sequence sets with parameters $(2^{n+1}-2,M,L,2)$. In this scheme, we can relatively freely choose the LCZ length L and the resulting LCZ sequence set has the size in which is nearly optimal with respect to Tang, Fan, and Matsufuji bound.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.12
• /
• pp.2875-2882
• /
• 2013

The design of PN(Pseudo Noise) sequences with good cross-correlation properties is important for many research areas in communication systems. Also analyses of cross-correlation frequency between designed sequences have been researched. In this paper we analyze of cross-correlation distribution and properties of non-linear binary sequences family $S^r=\{Tr^m_1\{[Tr^n_m(a{\alpha}^t+{\alpha}^{dt}]^r\}{\mid}a{\in}GF(2^m),0{\leq}t < 2^n-1\}$, where $gcd(r,2^m-1)=1$ with 5-valued cross-correlation.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.46 no.4
• /
• pp.34-41
• /
• 2009

In this paper we propose a new image encryption method which utilizes Complemented MLCA(Complemented Maximum Length Cellular Automata) based on IBCA(Intermediate Boundary CA) and 2D CAT(Cellular Automata Transform). The encryption method is processed in the following order. First, Complemented MLCA is used to create a PN (pseudo noise) sequence, which matches the size of the original image. And, the original image goes through a XOR operation with the created sequence to convert the image into Complemented MLCA image. Then, the gateway value is set to produce a 2D CAT basis function. The produced basis function is multiplied by the encrypted MLCA image that has been converted to process the encipherment. Lastly, the stability analysis and PSNR(Peak Signal to Noise Ratio) verifies that the proposed method holds a high encryption quality status.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.7C
• /
• pp.725-734
• /
• 2006

As a sequel to Part 1, the performance characteristics of the cell averaging (CA), greatest of (GO), and smallest of (SO) constant false alarm rate (CFAR) processors in nonhomogeneous environment are obtained and compared when receiving antenna diversity is employed in the pseudonoise (PN) code acquisition of direct-sequence code division multiple access (DS/CDMA) systems. Unlike in homogeneous environment, the GO CFAR processor is observed to exhibit the best performance in nonhomogeneous environment, with the CA CFAR processor performing the second best.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.26 no.5B
• /
• pp.599-607
• /
• 2001

이 논문에서는 부호와 순위를 바탕으로 한 비모수 검파기를 쓰는 직접수열 대역확산 시스템의 의사잡음 부호획득을 다루었다. 먼저 국소 최적 순위 검파기의 검정통계량을 얻고, 점근 점수 함수를 쓰는 국소 준최적 순위 검파기와 변형 부호순위 검파기의 검정통계량을 제외한다. 제안한 국소 준최적 순위 검파기와 변형 부호순위 검파기를 쓴 한 우물기법과 이제까지의 제곱합 검파기와 변형 부호 검파기를 쓴 것을 견주어 본다. 제안한 국소 준최적 순위 검파기와 변형 부호순위 검파기의 성능이 이제까지의 변형 부호 검파기의 성능보다 2-3dB쯤 낮고, 거의 최적임을 모의실험을 통해 확인하였다.