• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.7
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• pp.1549-1558
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• 2012

Location-aware system is utilized in various fields such as Logistics, Home Network, Healthcare, Military and Transportation systems. In this paper, we designed and implemented a Location-aware system based on IEEE 802.15.4a CSS (Chirp Spread Spectrum) technology in variable environment. The CSS is possible to precision location awareness using RF signal. According to experimental result, the implemented system has recognition error less than 0.5m within 20m radius in space.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.1937-1939
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• 2015

In order to improve the performance of a chirp based transmission scheme, the cross-coherence property should be carefully considered. In this paper, we propose two pairs of combinations using multiple linear chirp (MLC) which can reduce the cross-coherence for improving IEEE 802.15.4a chirp spread spectrum systems. The simulation results show that the proposed MLC scheme can improve the performance by considering the cross-coherence.

• IEMEK Journal of Embedded Systems and Applications
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• v.4 no.4
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• pp.148-155
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• 2009

Precise localization heavily relies on the accuracy of its underlying ranging technique. It has been known that the Chirp Spread Spectrum (CSS) defined in the IEEE 802.15.4a provides more dependable ranging accuracy than the Received Signal Strength Indicator (RSSI) in the IEEE 802.15.4. This paper examines the accuracy of the CSS-based ranging technique in the indoor/outdoor environments and discovers its consistent inaccuracy in different environments. Next, it proposes an error-correction architecture for the CSS-based ranging technique that exploits the per-environment consistent inaccuracy information and user visiting patterns (represented by weights for each environment).

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.658-665
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• 2013

While the chirp signal is extensively used in radar and sonar systems for target decision in wireless communication systems, it has not been widely used for positioning in indoor environments. Recently, the IEEE 802.15.4a standard has adopted the chirp spread spectrum (CSS) as an underlying technique for low-power and low-complexity precise localization. Chirp signal based ranging solutions have been established and deployed but their ranging performance has not been analyzed in multipath environments. This paper presents a ranging performance analysis of a chirp signal and suggests a method to suppress multipath error by using a type of non-linear chirp signal. Multipath ranging performance is evaluated using a conventional linear chirp signal and the proposed non-linear chirp signal. We verify the feasibility of both methods using two-ray multipath model simulation. Our results demonstrate that the proposed non-linear chirp signal can successfully suppress the multipath error.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4C
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• pp.453-459
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• 2009

Due to its capability to resist jamming signals, chirp spread spectrum (CSS) technique has attracted much attention in the field of wireless communications. However, there has been little rigorous analysis for the performance of CSS systems in the presence of jamming signals. In this paper, thus, we present analytic results on the performance of a CSS system: specifically, symbol error rate (SER) expressions are derived for a CSS M-ary phase shift keying (MPSK) system in the presence of broadband and tone jamming signals, respectively. The numerical results show that the empirical SER closely agree with the analytic result.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.10
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• pp.1-7
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• 2010

A new frequency offset estimation algorithm for chirp spread spectrum based on matched filter is proposed. Generally, the differential phase between successive symbols is used for the conventional frequency offset estimation algorithm. However, if the conventional frequency offset estimation algorithm is used for CSS, phase ambiguity arises because of long symbol duration and guard time. The phase ambiguity causes performance degradation of matched filter since the received signal is corrupted by the integer frequency offset. In this paper, we propose a new frequency offset estimation algorithm which separates integer and fractional frequency offset estimation for removing the phase ambiguity. The proposed algorithm estimates the integer frequency offset by using differential phase between matched filtering results of sub-chirps and successive symbols. Then, the fractional frequency offset is estimated by using the differential phase between successive symbols Simulation results show that the proposed algorithm well removes the phase ambiguity, and have almost same estimation performance compared with conventional one when there is not the phase ambiguity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.4
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• pp.59-64
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• 2007

In this paper, we propose a new decoding method for differentially biorthogonal chirp spread spectrum (DBO-CSS). In DBO-CSS, the information is carried on the differential phase not between the adjacent sub-chirp symbols but between the sub-chirp symbols in the same position of adjacent full-chirp symbol. So, the conventional multiple symbol differential detection (MSDD) algorithms to enhance the BER performance can not be applied to the DBO-CSS directly. In this paper, we propose a new differential detection algorithm based on a partial MSD(multiple symbol detection) and a viterbi algorithm. It is shown that the performance gain of the proposed algorithm when compared with that of the conventional detection algorithm is around 2.5dB at BER = 10-5.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.5
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• pp.106-121
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• 2008

In this paper, we proposed and designed the protocol for energy efficiency and the center of data aiming at the design of a Multi Location Awareness System that recognizes a shadow site in parking and tunnel, which stands on the basis of CSS(Chirp Spread Spectrum) method using ISM Band of IEEE 802.15.4a that aware close location with wireless RF only. As a result of the protocol measurement, it displays the observation errors of less than 15cm, the data error rate of less than 5%, and can implement the Multi Location Awareness System with maximum length of life for 13.5 days using battery of 3V(1500 mAh).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3C
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• pp.314-319
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• 2010

The chirp spread spectrum (CSS) technique that spreads the data signal over a wider frequency band via chirp signal for transmission has attracted much attention in the field of wireless communications due to capability to resist multipath fading signals. However, there has been little mathematical analysis for the performance of CSS-based communication systems in the multipath fading environments. In this paper, we study the influence of the multipath channel on the direct modulation (DM) scheme with M-ary phase shift keying (MPSK). When a chirp signal is transmitted on the Rayleigh fading channel and affected by additive white Gaussian noise (AWGN), we derive the theoretical performance. From numerical results, it is confirmed that the analytic symbol error rate (SER) agrees closely with the empirical SER.

• ETRI Journal
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• v.32 no.2
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• pp.330-332
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• 2010

We propose a new matched filter architecture for chirp spread spectrum in IEEE 802.15.4a. By using relations among the four subchirps, the proposed architecture comprises four subfilters utilizing only a set of coefficients matched to the first subchirp. The four subfilters share adders and registers, and as a result, the required adders and registers for implementation are reduced.