• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.16 no.8
• /
• pp.710-718
• /
• 1991

In this pape, an analysis approach for the performance of serial search burst-format direct sequence spread-spectrum code acquisiion system using matched filter is presented. And an acquistion system using analog matched filter is analyzed by this approach. And special consideration is focused on the effect of the code autocorelation sideobes. The basic idea of thi approach is the constuction of state tansition digram at the time of random packet arrival and the calculation of the packet loss probability, which is deveoped in terms of the following parameters: the false alarm probability. the etection probability, and the probability of receiver blocking obtained from the blocked customers cleae queeing system model. The analysis results reveal that the performance of the acquisition system is degraded by the effet of the code autocorrelation sidelobes above a certain value of SN/chip.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.7B
• /
• pp.1351-1360
• /
• 1999

In frequency selective channels, conventional PN code acquisition schemes are not ideal candidates. This is because they are primarily designed for the AWGN channel. In this paper, a direct-sequence spread-spectrum(DSSS) PN code acquisition system based on digital matched filtering (DMF) with automatic threshold control(ATC) algorithm is presented and analyzed with regards to probability of detection and probability of false alarm. These two important probabilities, the probability of detection ($P_D$) and the probability of false alarm ($P_{FA}$) are derived and analyzed in considering Doppler shift, sampling rate, mean acquisition time, and PN chip rate in frequency selective Rayleigh fading channel when using serial-search method as detection technique. From computer simulation results of a DMF acquisition system model, it is shown that the performance of the acquisition system using ATC algorithm is better than that of constant threshold system.

• Journal of the Korean Institute of Telematics and Electronics C
• /
• v.36C no.6
• /
• pp.18-26
• /
• 1999

This paper presents the architecture and design of a DSSS MODEM ASIC chip for wireless local area networks (WLAN). The implemented MODEM chip supports the DSSS physical layer specifications of the IEEE 802.11. The chip consits of a transmitter and a receiver which contain a CRC encoder/decoder, a differential encoder/decoder, a frequency offset compensator and a timing recovery circuit. The chip supports various data rates, i.e., 4,2 and 1Mbps and provides both DBPSK and DQPSK for data modulation. We have performed logic synthesis using the $SAMSUNG^{TM}$ $0.6{\mu}m$ gate array library and the implemented chip consists of 53,355 gates. The MODEM chip operates at 44MHz, the package type is 100-pin QFP and the power consumption is 1.2watt at 44MHz. The implemented MODEM architecture shows lower BER compared with the Harris HSP3824.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.6A
• /
• pp.871-880
• /
• 1999

In this paper, a pseudo-noise(PN) tracking and demodulation circuits are analyzed and designed for a direct-sequence/spread-spectrum multiple access system under a mobile fading channel. We consider noncoherent delay locked loop(DLL) as a PN code tracking loop which has 1/8 PN chip resolution. The tracking performance of DLL is evaluated in terms of locking time from a loose state and tracking jitter. The received signal is demodulated to original data by despreading with PN code locked by DLL. Also the designed circuit supports sound service of 32Kbps and in-band signal with 4.096MHz chip clock. The circuits are implemented and verified with FPGA, which is shown completely data recovery under AWGN 7dB and will be available for IMT-2000.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.37 no.1
• /
• pp.54-65
• /
• 2000

We propose a parallel acquisition scheme using antenna arrays for initial acquisition of direct-sequence spread-spectrum (DS-SS) signals. The proposed parallel scheme can lower substantially the range of detectable signal-to-noise ratio (SNR) as compared to the conventional parallel scheme with a single antenna. The proposed scheme uses the sum of the independent decision samples from antenna arrays corresponding to an identical subsequence of the pseudonoise (PN) code as a decision variable. We derive the probabilities of detection, missing, and false alarm under an additive white Gaussian noise (AWGN) channel and a flat Rayleigh fading channel. Using these, we get the mean acquisition time of the proposed scheme. From numerical results, we see that the acquisition performance becomes improved continually as the number of antennas increases.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.41 no.5
• /
• pp.19-25
• /
• 2004

In this paper, we propose optimal and suboptimal serial code acquisition schemes for chip-asynchronous direct-sequence spread-spectrum systems. The conventional serial code acquisition scheme is to compare each value of correlator outputs with a threshold individually. However, such a scheme is optimum only under the chip-synchronous assumption which is actually very difficult to be held prior to acquisition at the receiver because the signal-to-noise ratios before despreading are very low. In this paper, an optimal serial code acquisition scheme is derived based on the maximum-likelihood criterion under the more realistic and general chip-asynchronous environments. A suboptimal scheme, which is simpler but yields comparable performance to the optimal one, is also derived based on the criterion of local detection power Numerical results show that, under the chip-asynchronous environments, both the optimal and suboptimal serial code acquisition schemes outperform the conventional serial code acquisition scheme.

• Journal of Satellite, Information and Communications
• /
• v.8 no.1
• /
• pp.8-13
• /
• 2013

It is necessary to develop the next generation FTS which is suitable for our environment and effectively operates many launch vehicles. Standard tone, Secure tone, MHA, EFTS and DSSS are studied for the next generation FTS. FTS requires a high quality of performance and reliability because of their specific mission. And few FTSs are needed but the price is very expensive. Therefore we must investigate a part of the FTS whether the part can be reused for a part of the next FTS. In this paper, we use CCDF of the transmitted signal from FTS as the method to study a possibility of reusing HPA used in the present system. The simulation results show that PEP of Standard tone is 0.21dB and Secure tone and MHA has the same PEP. CPFSK's PEP is 1.81dB and PEP of DSSS using BPSK modulation is 2.6dB.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.1
• /
• pp.47-55
• /
• 1994

This paper investigates the performance analysis of the packet DS/SS receiver with a PJED(phase-jump error detector) using the block signal processing(BSP) methods. The conventional packet DS/SS block receiver has a high probability of mistaking the phase-jump detection, which causes the frequency estimation error. The conventional receiver uses a Matched-Pulse Timing Extractor which has a complicated structure. The proposed packet DS/SS block receiver with the PJED which uses libearity of the phase has little probability of mistaking the phase-jump detection. The proposed Matched Pulse Timing Extractor gas the more simple structure but obtains the same performance on the exact matched-pluse timing as the conventional one does. The simulation results show that the proposed receiver gives about 2dB improvement in the BER compared with the conventional receiver.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.17 no.9
• /
• pp.939-950
• /
• 1992

The performance of common spreading code scheme employing multiple-capture receiver is compared to that of transmitter-oriented (T/O) code division multiple access (CDMA) scheme in view of the possibility of collision-free transmissions and the effect of secondary multiple-access interference. For performance comparisons, secondary multiple-access interference is characterized for the common code scheme and the T/O CDMA scheme that assures perfectly collision-free transmissions. Throughput performance is then evaluated for these two schemes with direct-sequence spread-spectrum/differential-phase-shift-keying (DS-SS/DPSK) data modulation and forward-error-control coding (BCH codes) in the presence of an additive white Gaussian noise (AWGN). It is shown that when the number of radios is relatively large, the maximum normalized throughput is greater for the common code scheme than for the T/O CDMA scheme at a moderate signal-to-noise ration(SNR).

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.6 no.3
• /
• pp.55-67
• /
• 1995

The error rate equations of MPSK and DS/MPSK radio signals transmitted through the m-distributed fading channel in Gaussian noise and tone interference environments have been derived. Using the derived equations, the error rate performance is evaluated and shown as functions of carrier-to-noise ratio, carrier-to-interference ratio, processing gain, fading index and the number of diversity branches. The derivation has been done for two cases. The first case assumes that only the signal is undergoing the influence of fading, and the second case assumes that both signal and interference are undergoing the influence of fading simultaneously. From the obtained results, we have known that the error performance of MPSK signal is improved by using diversity technique and direct sequence spread spectrum technique even in a fading environment. Also comparing the error rate performance of two cases, the latter is worse than the former.