• ETRI Journal
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• v.33 no.6
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• pp.841-848
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• 2011

A signal-to-noise ratio (SNR) enhancement algorithm using multiple chirp symbols with clock drift is proposed for accurate ranging. Improvement of the ranging performance can be achieved by using the multiple chirp symbols according to Cramer-Rao lower bound; however, distortion caused by clock drift is inevitable practically. The distortion induced by the clock drift is approximated as a linear phase term, caused by carrier frequency offset, sampling time offset, and symbol time offset. SNR of the averaged chirp symbol obtained from the proposed algorithm based on the phase derotation and the symbol averaging is enhanced. Hence, the ranging performance is improved. The mathematical analysis of the SNR enhancement agrees with the simulations.

• 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.