Search

We herein propose a low-approximated least-squares method for underwater drone localization that does not require depth information. On the basis of error analysis, we propose a rule to deploy a set of surface drones that minimizes the impact of measurement errors such as GPS or distance measurement errors. The Evaluation results indicate that the proposed method outperforms the least-squares method when depth information is not provided.

Signal scattering in the troposphere is a phenomenon referred to as “troposcatter”, and it is promising method for wireless communication beyond the line of sight (b-LOS). For a troposcatter communication system, it is important to develop a channel model for the tropospheric scatter. Recently, b-LOS communication using troposcatter received much attention for its application to military communication. Thus, a comprehensive review and analysis of conventional ITU-R troposcatter propagation models and recent results would be a timely study. Accordingly, in this study, we analyze and simulate the tropospheric scatter propagation model proposed by the ITU-R. Troposcatter propagation models in ITU-R recommendations consist of three parts: basic transmission loss, gaseous absorption, and a precipitation fading model. The ITU-R P.2001 simulation model shows basic transmission losses of 210 dB and 240 dB at 0.2 GHz and 2 GHz in 300 km distances, respectively. The ITU-R P.452 model results in 20 dB less loss, but this is dependent on measurement conditions. Gaseous absorption and precipitation fading have less than 1 dB loss for frequencies less than 2 GHz, but can increase to be over 10 dB in loss for frequencies of 2 GHz and above. We also review recent studies on tropospheric scatter channel models and communication systems. In addition to these reviews, we examine recent studies on ray tracing methods for tropospheric scatter channel models.