• The Journal of the Korea Contents Association
• /
• v.9 no.2
• /
• pp.10-17
• /
• 2009

This paper analyze the effect of frequency offset for the IEEE 802.15.4b LR-WPAN(Low-Rate Wireless Personal Area Network) with 915MHz bandwidth noncoherent DSSS O-QPSK based receiver system, and presents a compensation method with addition of differential filter to the system for compensation of frequency offset problem. DSSS PSSS-ASK and DSSS O-QPSK modulation techniques are accepted within the regularization of IEEE 802.15.4b. These new method can obtain 250kbps transmission rate. The DSSS O-QPSK modulation method that is used in this paper has no BER variation below 40ppm(frequency offset 36.6kHz), but if the offset frequency become high above 40ppm, then the system cannot have stable receiving condition due to worse BER. To solve this problem, we present a more stabilized receiver system at maximum frequency offset ${\pm}80ppm$ using MDDF unti a correlator of DSSS O-QPSK modulator. Moreover computer simulation results will be presented to evaluate the performance of the proposed algorithm unde various AWGN and frequency offset environment.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.41 no.11
• /
• pp.25-32
• /
• 2004

In this paper, we first analysed the ability of DSSS resistance against noises, which are main interferences to the four types in power line communications. Based on the characteristic of these noises, we made a noise source of power line which is similar with the result measured, in practice. We simulated and analysed the BER performance of BPSK with DSSS over this noise model and one without the DSSS, for comparison. Result showed that the BPSK with DSSS system has improved by 8 dB, as compared to those without the DSSS, as against power line noises.

• Aerospace Engineering and Technology
• /
• v.10 no.1
• /
• pp.45-53
• /
• 2011

This paper is technical review about Direct Sequence Spread Spectrum(DSSS) to apply in launch vehicle system. First, we introduce communication protocol(carrier frequency, code length, process gain, data rate, chip rate etc) about several application system using DSSS. And then, we survey and summarize the effect of doppler shift to the DSSS. The doppler shift is important error factor for PN code tracking in the fast moving system like launch vehicle. So, spread spectrum code acquisition technique for a direct sequence system in the presence of doppler effect must be investigated.

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.303-304
• /
• 2008

In this paper, the performance of DSSS OQPSK architecture for 868/915MHz LR-WPAN(Low-Rate Wire less Personal Area Network) is analyzed. Since the frequency offset of ${\pm}40ppm$ on 868/915MHz band is recommended in IEEE 802.15.4 LR-WPAN specification. it is required to have a non-coherent detection that is stable operation in the channel environment with large frequency offset is required.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.1737-1738
• /
• 2008

In this paper, the performance of DSSS O-QPSK architecture for IEEE 802.15.4b LR-WPAN (Low-Rate Wire less Personal Area Network) is analyzed. Since the frequency offset of $\pm$40ppm on 868/915MHz band is recommended in IEEE 802.15.4b LR-WPAN specification. it is required to have a non-coherent detection that is stable operation in the channel environment with large frequency offset is required.

• Journal of Communications and Networks
• /
• v.14 no.2
• /
• pp.206-212
• /
• 2012

In this paper, in order to effectively apply unitary space-time modulation to the direct-sequence spread-spectrum multiple-access (DSSS-MA) networks, we propose a low-rate, noncoherent, unitary, and space-time modulated DSSS system supporting any number of transmit antennas based on Walsh matrices. The proposed scheme simultaneously performs bandwidth spreading and space-time coding and outperforms those using high-rate, conventional unitary space-time constellations. Furthermore, the proposed scheme allows for a simple detector structure based on fast Walsh transforms.

• Proceedings of the Korea Society for Industrial Systems Conference
• /
• 2007.02a
• /
• pp.139-151
• /
• 2007

Decision-making in the crisis management happens in dynamic, rapidly changing, and often unpredictable distributed environments. Crisis management Decision Support Systems (DSSs) in E-Government are challenged by the need to use it availably at anytime, from anywhere, and even under any-situation. In this paper the reasons of developing distributed architecture for crisis management Decision Support Systems (DSSs) in E-Government are analyzed. Consequently, a distributed architecture for crisis management Decision Support System (DSS) is proposed in this paper. Finally it is implemented by Web Services. If crisis management Decision Support System (DSS) based on distributed architecture is implemented by Web Service, then it can provide decision support for decision-makers to deal with crisis at anytime, from anywhere, and even under any-situation.

• Journal of Digital Contents Society
• /
• v.7 no.2
• /
• pp.103-108
• /
• 2006

Short-range wireless communication and networking technologies are becoming increasingly important in enabling useful mobile applications. for example, ZigBee technology is expected to provide low cost and low power connectivity for equipment that needs battery life as long as several months to several years. In addition, ZigBee can be implemented in mesh networks larger than is possible with Bluetooth. The main features of this ZigBee standard are network flexibility, low cost, very low power consumption, and low data rate in an adhoc self-organizing network among fixed, portable and moving devices. Home network/Home automation is one of the key market areas for Zigbee, with an example of a simple network This paper investigates the effect of short range wireless channel on the performance of Zigbee system and DSSS-BPSK signal transmission in AWGN, interference and Rician fading environments. And we investigate performance degradation due to interference and fading effects in short range wireless channel. In particular, the impacts of the fading and interference level on the bit error probability is shown in BER performance figures.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.8
• /
• pp.110-118
• /
• 2013

This paper describes the development of DSSS wireless communication uplink system for missile remote control. In consideration of low probability of intercept, low probability of exploitation, anti-jam, low latency, and doppler frequency offset, we used DSSS partially DBPSK. Also we used the selective diversity with two receiving antennas to mitigate multipath interference which is the dominant channel impairment and the turbo product code(TPC) for forward error correction(FEC) to improve bit error rate performance.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.2C
• /
• pp.91-99
• /
• 2003

In this paper, We analyze performance of ZFE MUD receiver in DSSS unidirectional wireless transceiver operating in 2.4㎓ ISM band and indoor environment. This system has the shortcomings that many burst error is occurred because of long term deep fade experienced by some user and impossibility of power control. Therefore, the solution to this problem is important because the performance of DS-CDMA system is guaranteed under, the perfect power control. MUD receive. which improves the performance of this system is not required to perform rigorous power control and is able to remove MAI using linear equalization. From the result of performance comparison, we show that ZFE MUD receiver is more adequate for this system than other receivers.