Long-Range Acoustic Communication Using Differential Chirp Spread Spectrum

Abstract

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.

Spread spectrum modulation recognition based on phase diagram entropy

“…FB methods are based on the identification of defining features capable of discriminating between the analyzed signals. The most used features in FB scenarios are given by instantaneous features (Yu et al, 2019), high-order statistical features (Xiao-Ming and Zhong-Zhao, 2006), wavelet features (Huang et al, 2010) and time-frequency representations (Lee et al, 2020;Khan et al, 2022). But the performance of these FB methods largely depends on empirical feature extraction.…”

“…The thresholds used in this approach can be an impediment, because the choice of values is not automatic. The CSS signal recognition was improved in (Lee et al, 2020) by using the matched filter method on the spectrogram approach. The authors showed that the size of the matched filter can be doubled by applying a differential coding method and the performance is improved even if the SNR value is SNR 0dB.…”

“…Also, the performance of the linear discriminant analysis method in (Khan et al, 2022) degraded for the FHSS signals at low SNR value because the frequencies of the signals are overlapping with the background noise. The visual method analyzed in (Lee et al, 2020) is the most susceptible to noise. At low SNR values, the spectrograms of CSS signals lose their interpretability and advanced processing techniques are needed to be able to eliminate the effects of noise.…”

Wake-Up Receiver for Underwater Acoustic Communication Using in Shallow Water

“…Moreover, such systems may use a multi-antenna technique [ 12 , 13 ]. The most popular representatives of the spread spectrum technique are frequency-hopping spread spectrum (FHSS), direct-sequence spread spectrum (DSSS), and chirp spread spectrum (CSS), although there are also several variations [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. Among them, there are mainly systems with solutions that ensure data transmission with the highest possible transmission rate in vertical channels and a relatively lower rate in horizontal channels.…”

Asynchronous Chirp Slope Keying for Underwater Acoustic Communication

“…Interference cancellation is crucial for underwater communication, this topic has been addressed by Diamant [ 43 ]. In the more recent work of Lee et al [ 44 ], the authors explore the parameter space of chirp spread spectrum (CSS) methods in context of long range communication.…”