# Study of NVIS Channel for USN Protocol Definition in Antarctica
)1 La Salle Campus, Ramon Llull University, 08022 Barcelona, Spain; [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] (D.B. )1 La Salle Campus, Ramon Llull University, 08022 Barcelona, Spain; [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] (D.B. )1 La Salle Campus, Ramon Llull University, 08022 Barcelona, Spain; [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] (J.P.); [EMAIL_ADDRESS] (D.B. )1 La Salle Campus, Ramon Llull University, 08022 Barcelona, Spain; [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] (J.P.); [EMAIL_ADDRESS] (D.B. )1 La Salle Campus, Ramon Llull University, 08022 Barcelona, Spain; [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] (J.P.); [EMAIL_ADDRESS] (D.B. )1 La Salle Campus, Ramon Llull University, 08022 Barcelona, Spain; [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] (J.M.M. ); [EMAIL_ADDRESS] (J.P.); [EMAIL_ADDRESS] (D.B. )1 La Salle Campus, Ramon Llull University, 08022 Barcelona, Spain; [EMAIL_ADDRESS] ([PERSON]); [EMAIL_ADDRESS] (J.M.M. ); [EMAIL_ADDRESS] (J.P.); [EMAIL_ADDRESS] (J.P.); [EMAIL_ADDRESS] (D.B. )1 La Salle Campus, Ramon Llull University, 08022 Barcelona, Spain; [EMAIL_ADDRESS] (J.M.M. ); [EMAIL_ADDRESS] (J.M.M. ); [EMAIL_ADDRESS] (J.P.); [EMAIL_ADDRESS] (D.B. )1 La Salle Campus, Ramon Llull University, 08022 Barcelona, Spain; [EMAIL_ADDRESS] (J.M.M. ); [EMAIL_ADDRESS] (J.M.M. ); [EMAIL_ADDRESS] (J.P.); [EMAIL_ADDRESS] (D.B. )1 La Salle Campus, Ramon Llull University, 08022 Barcelona, Spainusable frequencies range from 3 MHz to 10 MHz. As the power transmission is low, typically below 10 W, it is a good option for RIoT in locations without an electrical network with a self-sufficient energy system. On the other hand, the maximum of the radiation diagram must be upward, large horizontal dipoles and inverted-V antennas are commonly used with masks up to 15 m high. However, we can also use smaller antennas such as loops if we keep the antenna losses under control. Although the power transmission is low and the antenna gain is negative, the use of low consumption NVIS communications for USN becomes feasible since the losses due to obstacles are negligible. Even in the presence of mountains in between, the free space propagation losses are the only ones to be taken into account [13]. However, NVIS low power transmissions cannot reach high bitrates as 3G and 4G networks. In this case, the bandwidth usage is about 3 kHz to obtain bitrates of 6 Kbps as maximum [14], which is enough for most USN. Actually, we can find some previous works related to the improvement of the ionospheric communications based on the analysis of the ionospheric channel, polarization techniques, narrowband modulations, and multicarrier modulations. [PERSON] [15], [PERSON] [16], [PERSON] [17] and [PERSON] [18] study the main characteristics of the NVIS channel as the availability, delay spread, Doppler spread, and Doppler shift for 3 kHz transmissions. In our work, we will study the main characteristics of the NVIS channel and by the analysis of it, we will design a new NVIS frame protocol. [PERSON] [19] and [PERSON] [20] study different polarization ways to receive the NVIS signal with the purpose of applying by multiple input multiple output (MIMO) polarization techniques to improve the transmissions. In our work, we focused the study on the improvement of the transmissions by the redefinition of the frame protocol. In addition, [PERSON] [21] studies narrowband modulations with 3 kHz of bandwidth to analyse the performance of each modulation. In our work, we compare the robustness of two narrowband modulations real tested in comparison to a multicarrier modulation designed taking into account the NVIS channel effects measured. [PERSON] [22] studies a comparison between spread spectrum and multicarrier modulations based on previous studies of a long haul HF channel effects.