scholarly journals Reliable and Low-Complexity Chirp Spread Spectrum-Based Aerial Acoustic Communication

IEEE Access ◽  
2020 ◽  
Vol 8 ◽  
pp. 151589-151601
Author(s):  
Jihwan Lee ◽  
Chulyoung Kwak ◽  
Seongwon Kim ◽  
Saewoong Bahk
Keyword(s):  
Acoustic Communication ◽  
Spread Spectrum ◽  
Low Complexity ◽  
Chirp Spread Spectrum

scholarly journals M-ary nonlinear sine chirp spread spectrum for underwater acoustic communication based on virtual time-reversal mirror method

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Songzuo Liu ◽  
Habib Hussain Zuberi ◽  
Yi Lou ◽  
Muhmmad Bilal Farooq ◽  
Shahabuddin Shaikh ◽  
...  
Keyword(s):  
Acoustic Communication ◽  
Time Reversal ◽  
Spread Spectrum ◽  
Underwater Acoustic Communication ◽  
Half Cycle ◽  
Spreading Factor ◽  
Underwater Acoustic ◽  
Virtual Time ◽  
Chirp Spread Spectrum ◽  
Time Reversal Mirror

AbstractLinear chirp spread spectrum technique is widely used in underwater acoustic communication because of their resilience to high multipath and Doppler shift. Linear frequency modulated signal requires a high spreading factor to nearly reach orthogonality between two pairs of signals. On the other hand, nonlinear chirp spread spectrum signals can provide orthogonality at a low spreading factor. As a result, it improves spectral efficiency and is more insensitive to Doppler spread than the linear counterpart. To achieve a higher data rate, we propose two variants (half cycle sine and full cycle sine) of the M-ary nonlinear sine chirp spread spectrum technique based on virtual time-reversal mirror (VTRM). The proposed scheme uses different frequency bands to transmit chirp, and VTRM is used to improve the bit error rate due to high multipath. Its superior Doppler sensitivity makes it suitable for underwater acoustic communication. Furthermore, the proposed method uses a simple, low-power bank of matched filters; thus, it reduces the overall system complexity. Simulations are performed in different underwater acoustic channels to verify the robustness of the proposed scheme.

scholarly journals A Low-Complexity Demodulation for Oversampled LoRa Signal

2021 ◽  
Author(s):  
Vincent Savaux
Keyword(s):  
Performance Analysis ◽  
Spread Spectrum ◽  
Fourier Transforms ◽  
Additive White Gaussian Noise ◽  
Low Complexity ◽  
Discrete Fourier Transforms ◽  
Rayleigh Channel ◽  
Nyquist Rate ◽  
Chirp Spread Spectrum ◽  
Demodulation Method

This paper deals with a method of demodulation for oversampled LoRa signal. The usual maximum likelihood (ML) based demodulation method for LoRa chirp spread spectrum (CSS) waveform is dedicated to signals sampled at Nyquist rate, whereas considering oversampled signals may improve the performance of the LoRa demodulation process. In this respect, when an oversampling rate (OSR) 2 is assumed, the method suggested in this paper consists in applying two demodulation processes to the even and odd samples of the oversampled LoRa signal, and then combining the results. This principle is then generalized to any OSR, and we show that the complexity of the method is low since it only involves discrete Fourier transforms (DFT). Moreover, a performance analysis in terms of symbol and bit error rate (SER and BER) is presented considering both additive white Gaussian noise (AWGN) and Rayleigh channel models. Simulations show the relevance of the method and the performance analysis as a gain of 3 dB is achieved by the demodulation at OSR 2 compared with OSR 1.

scholarly journals A Low-Complexity Demodulation for Oversampled LoRa Signal

2021 ◽  
Author(s):  
Vincent Savaux
Keyword(s):  
Performance Analysis ◽  
Spread Spectrum ◽  
Fourier Transforms ◽  
Additive White Gaussian Noise ◽  
Low Complexity ◽  
Discrete Fourier Transforms ◽  
Rayleigh Channel ◽  
Nyquist Rate ◽  
Chirp Spread Spectrum ◽  
Demodulation Method

This paper deals with a method of demodulation for oversampled LoRa signal. The usual maximum likelihood (ML) based demodulation method for LoRa chirp spread spectrum (CSS) waveform is dedicated to signals sampled at Nyquist rate, whereas considering oversampled signals may improve the performance of the LoRa demodulation process. In this respect, when an oversampling rate (OSR) 2 is assumed, the method suggested in this paper consists in applying two demodulation processes to the even and odd samples of the oversampled LoRa signal, and then combining the results. This principle is then generalized to any OSR, and we show that the complexity of the method is low since it only involves discrete Fourier transforms (DFT). Moreover, a performance analysis in terms of symbol and bit error rate (SER and BER) is presented considering both additive white Gaussian noise (AWGN) and Rayleigh channel models. Simulations show the relevance of the method and the performance analysis as a gain of 3 dB is achieved by the demodulation at OSR 2 compared with OSR 1.

scholarly journals Long-Range Acoustic Communication Using Differential Chirp Spread Spectrum

2020 ◽  
Vol 10 (24) ◽  
pp. 8835
Author(s):  
Joohyoung Lee ◽  
Jeongha An ◽  
Hyung-in Ra ◽  
Kiman Kim
Keyword(s):  
Long Range ◽  
Acoustic Communication ◽  
Bit Error Rate ◽  
Spread Spectrum ◽  
Matched Filter ◽  
Modulation Method ◽  
Differential Encoding ◽  
Time Bandwidth Product ◽  
Chirp Spread Spectrum ◽  
The Difference

Here, we propose a new modulation method using chirp spread spectrum (CSS) modulation to indicate the result of long-range acoustic communication (LRAC). CSS modulation had outstanding matched filter characteristics even though the channel was complex. The performance of the matched filter depends on the time–bandwidth product. We studied the method of using the same modulation method while increasing the amount of the time–bandwidth product. When differential encoding is applied, the de-modulation is made using the difference between the current symbol and the previous symbol. If the matched filter is applied using both the current and the previous symbol, such as the use of two symbols, the amount of the time–bandwidth product can be doubled, and this method can make the output of the matched filter larger. The proposed method was verified in lake and sea experiments, in which the experimental environment was analyzed and compared with the result using the channel impulse response (CIR) of the lake and sea. The lake experiment was conducted over a distance of about 100–300 m between the transmitter and receiver and at a depth of ~40 m. As a result of the communication, the conventional method’s bit error rate (BER) was 1.22×10−1, but the proposed method’s BER was 1.98×10−2. The sea experiment was conducted over a distance of ~90 km and at a depth of ~1 km, and the conventional method BER in this experiment was 1.83×10−4, while the proposed method’s BER was 0.

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