Abstract
Every year more interest is focused on high frequencies (HF) communications for remote sensing platforms due to their capacity to establish links of more than 250 km without a line of sight and due to them being a low-cost alternative to satellite communications. In this article, we study the ionospheric ordinary and extraordinary waves to improve the applications of near vertical incidence skywave (NVIS) on a single input multiple output (SIMO) configuration. To obtain the results, we established a link of 95 km to test the diversity combining of ordinary and extraordinary waves by using selection combining (SC) and equal-gain combining (EGC) on a remote sensing platform. The testbench is based on digital modulation transmissions with power transmission between 3 and 100 W. The results show us the main energy per bit to noise spectral density ratio (Eb/N0) and the bit error rate (BER) differences between ordinary and extraordinary waves, SC, and EGC. To conclude, diversity techniques show us a decrease of the power transmission need, allowing for the use of compact antennas and increasing battery autonomy. Furthermore, we present three different improvement options for NVIS SIMO remote sensing platforms depending on the requirements of bitrate, power consumption, and efficiency of communication.
Highlights
The world’s communications have gone from the communication between millions and millions of people to billions and billions of “things.” The current networks are focused in urban areas with many devices (NB-IoT, Lora-Wan, Sigfox [1,2]) and people (3G, 4G, GSM)
Some works [3,4,5,6,7,8,9] in high frequency (HF) communications validate the viability of ionospheric communications in remote areas [10]
There are some previous works related to the performance of this channel [3,4,5,6,7,8,9], this study shows how some physical characteristics of the ionosphere will improve the performance of the near vertical incidence skywave (NVIS) channel
Summary
The world’s communications have gone from the communication between millions and millions of people to billions and billions of “things.” The current networks are focused in urban areas with many devices (NB-IoT, Lora-Wan, Sigfox [1,2]) and people (3G, 4G, GSM). As the ionization of the atmosphere is directly affected by the Sun, the star’s variation makes the NVIS channel very unstable, leading to undesired fading, interferences, and link losses This ionization affects the refraction index, creating two characteristic waves, the ordinary and the extraordinary. This work proves that the understanding and use of the ordinary and extraordinary waves [11] from the F2 layer of the ionosphere [12] lead to an improvement in the NVIS channel’s performance. Our work studies the behavior of the characteristic waves and demonstrates that this channel de-correlation can lead to an improvement in the ionospheric link. Our work proposes a comparison with different diversity combining algorithms (selection combining and equal-gain combining), merging both waves to improve the performance and the robustness of the NVIS channel.
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