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Autonomous Underwater Vehicles (AUVs) are becoming increasingly popular for large number of civil and military applications, such as environmental monitoring, oceanography, archaeology, or mine warfare. Operational safety issue still prevents the exploitation of the full potential of AUVs. Operations of AUVs are limited by constraints including the need to guarantee no collision with manned surface vehicles. To avoid collisions, a solution is to relay surface vessel positions to the AUVs by an underwater communication link. The communication must be optimized to establish a robust and reliable link at various range and depth. Commercial underwater acoustic modems are often dedicated for specific distances and bit rates with performances strongly dependent on the environmental conditions. For the considered application, the modem must be adaptive at the time and frequency selectivity of the channel which is varying according to the operation context. In this work, we propose an adaptive underwater acoustic waveform optimized to exploit at the best the time and frequency diversity the channel. To show the potential gain obtained by using diversity, the performance of the designed modem is evaluated using theoretical and realistic underwater channels. In addition, we propose a method for adapting the waveform based only on the knowledge of the transmission geometry. Finally, the proposed modem is tested to relay Automatic Identification Systems (AIS) picture of an area to AUVs.

Background and Aim: Data are scarce regarding Wolf-Parkinson White Syndrome (WPW) syndrome and asymptomatic pre-excitation in Africa. This study tried to understand the current approaches utilized in Africa for the diagnosis and management of both symptomatic and asymptomatic ventricular pre-excitation., Methods: The current prospective study was conducted in 20 centers located in 17 countries spanning all areas of Africa. Participants included had ventricular pre-excitation patterns. The data collected included symptoms, locations of accessory pathways (AP) and tachyarrhythmia, risk stratification, as well as acute and long-term management. In addition, we assessed the clinical effectiveness of the centers and the impact of socioeconomic and health metrics on these treatment approaches., Results: Among 541 participants, 93% were diagnosed with WPW syndrome, with orthodromic atrioventricular reciprocating tachycardia (AVRT) being the most prevalent arrhythmia, affecting 55% of the cases. Approximately 30% of patients in Africa, except for the southern region, received intravenous amiodarone as the first-choice drug for orthodromic AVRT while adenosine was the drug of choice in the Southern region. Electrical cardioversion was the first-line treatment for pre-excited atrial fibrillation and antidromic AVRT across all of Africa. Radiofrequency ablation (RF) was the first long-term therapy option for 88% of patients in all African regions, unlike western and central Africa where it was implemented for less than 30% of patients (p < 0.001). The rates of RF success, long-term recurrence, and complications were 93%, 4.1%, and 3.8%, respectively., Conclusion: There are significant variations between African regions in terms of diagnostic workup, accessory pathway localizations, and volume of invasive treatment. Countries in Northern and Southern Africa are more advanced than other African countries in terms of modern management strategy. Additional government investments are necessary to enhance diagnostic likelihood and curative treatments as well as to reduce the gap between different regions in Africa., (© 2025 Wiley Periodicals LLC.)