Abstract:While underwater acoustic (UWA) communication offers a practical way to establish a wireless link with underwater vehicles, designing a UWA communication system onboard a small autonomous underwater vehicle (AUV) still poses significant challenges. As the adoption of the low-complexity, robust noncoherent communication technology is limited by low bandwidth efficiency and a low data rate, coherent UWA communication requires Doppler mitigation and channel equalization measures to achieve a relatively high data … Show more
“…where For the Ka-band 100 MHz signal applied in this paper, the maximum spreading of the bandwidth is 3.3 kHz. Given that the time-varying Doppler effect has been solved by mature techniques [19][20][21][22], so it is not the focus of our study. Consequently, the LEO satellite-ground transmission channel is modeled as an AWGN channel in this paper.…”
A novel joint satellite-transmitter and ground-receiver (JSG) digital pre-distortion (DPD) (JSG-DPD) technique is proposed to improve the linearity and power efficiency of the space-borne active phased arrays (APAs) in low Earth orbit (LEO) satellite communications. Different from the conventional DPD technique that requires a complex RF feedback loop, the DPD coefficients based on a generalized memory polynomial (GMP) model are extracted at the ground-receiver and then transmitted to the digital baseband front-end of the LEO satellite-transmitter via a satellite–ground bi-directional transmission link. The issue of the additive white Gaussian noise (AWGN) of the satellite–ground channel affecting the extraction of DPD coefficients is tackled using a superimposing training sequences (STS) method. The proposed technique has been experimentally verified using a 28 GHz phased array. The performance improvements in terms of error vector amplitude (EVM) and adjacent channel power ratio (ACPR) are 7.5% and 3.6 dB, respectively. Requiring limited space-borne resources, this technique offers a promising solution to achieve APA DPD for LEO satellite communications.
“…where For the Ka-band 100 MHz signal applied in this paper, the maximum spreading of the bandwidth is 3.3 kHz. Given that the time-varying Doppler effect has been solved by mature techniques [19][20][21][22], so it is not the focus of our study. Consequently, the LEO satellite-ground transmission channel is modeled as an AWGN channel in this paper.…”
A novel joint satellite-transmitter and ground-receiver (JSG) digital pre-distortion (DPD) (JSG-DPD) technique is proposed to improve the linearity and power efficiency of the space-borne active phased arrays (APAs) in low Earth orbit (LEO) satellite communications. Different from the conventional DPD technique that requires a complex RF feedback loop, the DPD coefficients based on a generalized memory polynomial (GMP) model are extracted at the ground-receiver and then transmitted to the digital baseband front-end of the LEO satellite-transmitter via a satellite–ground bi-directional transmission link. The issue of the additive white Gaussian noise (AWGN) of the satellite–ground channel affecting the extraction of DPD coefficients is tackled using a superimposing training sequences (STS) method. The proposed technique has been experimentally verified using a 28 GHz phased array. The performance improvements in terms of error vector amplitude (EVM) and adjacent channel power ratio (ACPR) are 7.5% and 3.6 dB, respectively. Requiring limited space-borne resources, this technique offers a promising solution to achieve APA DPD for LEO satellite communications.
“…there are three main technologies used in underwater communication: (i) Acoustics communication: this is the most common and used technology for underwater communication because it can provide long-distance propagation which can be in tens of kilometers. The major drawback of this technology is the latency in communication since the transmission baud rate is only up to several kilobits per second (kbps) [3]. (ii) Wireless Optical communication: by using wireless optical communication we can achieve a data rate of hundreds of Megabits per second (Mbps) with a distance of tens of meters, this is considered the best technology for a high data rate.…”
Autonomous Underwater Vehicles (AUVs) require long-distance communication, especially in the deep sea. Radiofrequency (RF) communication provides a high data rate. However, electromagnetic wave is seriously limited by high attenuation in the water medium. In this study, we investigate Radiofrequency communication in seawater. The experiment results show the effects of the distance between the transmitter and receiver, and the stability of the antennas. We achieved HD video transmission with 25fps.
“…The technology of underwater acoustic networks (UAN) has drawn substantial attention due to its significant potential in extensive civil and military fields, e.g., marine environment monitoring [1], marine resource exploration [2], marine disaster warning [3], underwater information acquisition and transmission [4], autonomous underwater vehicleassisted navigation [5], communication between scuba divers [6], military applications [7], etc. Evolved from the concept of cognitive radio, the cognitive network (CN) technique has characteristics that optimize a network via environmental sensing, adaptive adjustment, intelligent decision-making, and reconfiguration.…”
Section: Introductionmentioning
confidence: 99%
“…However, while cognitive networks have achieved significant progress in academic research, the R&D of the standard network model, and practical commercial applications based on established wireless channel sensing and cognitive optimization strategies [1][2][3][4][5][6][7][8], the specific implementation of CNs in the underwater acoustic channel still encounter many difficulties due to the highly diverse channel patterns, underwater acoustic (UWA) communication modes, and network protocols.…”
Originating from the concept of cognitive networks (CNs), which are becoming popular in wireless terrestrial communication scenarios, underwater acoustic cognitive networks (UACNs) are drawing more and more attention in the field of the Internet of Underwater Things (IoUT). However, as the implementation of cognitive mechanisms in underwater acoustic networks is different from that of wireless scenarios, it is impossible or difficult for traditional simulation platforms to carry out simulations of UACNs. There is a lack of specialized simulation tools in terms of UACNs. To enable the quantitative evaluation of the effectiveness and performance enhancement of a UACNs in an adverse underwater environment, a simulation platform of acoustic cognitive networks (SPACNet) was designed and investigated in this article. First, based on a state machine-based protocol programming framework, the SPACNet is capable of supporting the implementation of different state-transform types associated with cognitive networking protocols. Moreover, to facilitate the realization of cognitive function at comprehensive levels of signal, information, and link, an underwater acoustic channel model with an environmental parameter input is integrated in SPACNet to generate underwater environment-driven multiple-aspect behaviors. Moreover, a simplified collision model consisting of an environment factor, channel response, and node location is used to reduce the complexity of the simulation of UACNs signal reception. A simulation was carried out to verify the effectiveness of SPACNet in evaluating the cognitive capabilities of UACNs. Finally, a field UACNs experiment was performed to validate the general consistency between the conclusion obtained with the SPACNet-based simulation and that from the field test.
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