Narrowband and Wideband Channel Sounding of an Antarctica to Spain Ionospheric Radio Link

Abstract

La Salle and Ebro Observatory have been involved in remote sensing projects in Antarctica for the last 11 years (approximately one solar cycle). The Ebro Observatory has been monitoring and analyzing the geomagnetic and the ionospheric activity in the Antarctic Spanish station Juan Carlos I (ASJI) (62.7• S, 299.6• E) for more than eighteen and ten years, respectively. La Salle has two main goals in the project. The first one is the data transmission and reception from Antarctica to Spain to obtain a historical series of measurements of channel sounding of this 12,760-km ionospheric HF (high frequency) radio link. The second one is the establishment of a stable data low power communication system between the ASJI and Cambrils, Spain (41.0• N, 1.0 • E), to transmit the data from the remote sensors located on the island. In this paper, both narrowband and wideband soundings have been carried out to figure out the channel availability performed using a frequency range from 2 to 30 MHz with 0.5 MHz step during the 24 h of the day, encompassing wider channel measurements than previously done, in terms of hours and frequency. This paper presents the results obtained for the austral summer in 2014, using a monopole antenna at the transmitter and an inverted V on the receiver side. These results led us to the final physical layer design for the long Remote Sens. 2015, 7 11713 haul link, dividing the day into two parts: daytime, with low data throughput design, and nighttime, reaching high data throughput.

Physical Layer Definition for a Long-Haul HF Antarctica to Spain Radio Link

“…The transmission frequencies vary depending on the campaign, and even for weeks or days, and have to be redefined while the tests are being conducted in order to adjust their value to the maximum propagation frequency. As it can be observed in Figures 8 and 9, two propagation zones can be defined, separated by the sunrise and the sunset, which present variable propagation performance [7]. From 00 UTC to 07 UTC, propagation is good at low frequencies, and from 18 UTC to 23 UTC.…”

“…More information about this classification can be found in [6,7,11]. The wideband sounding has also been analyzed in order to determine the maximum delay spread and Doppler spread [6,7,11]. These two channel measures give light to the most suitable modulation for each time of the day and its parameter selection.…”

“…The sunrise (around 07 UTC) and the sunset (around 17 UTC) present unstable performance in terms of propagation, as they are classified as change points from daytime to nighttime. More information about this classification can be found in [6,7,11]. The wideband sounding has also been analyzed in order to determine the maximum delay spread and Doppler spread [6,7,11].…”

“…The first one to describe in detail the final HF modem hardware, improved since [6,11]. The second one is to continue the work of [7], explaining the narrowband and wideband soundings. In this paper, we present the study of the synchronization sequences, we analyze the channel error burst rate and we choose the best modulations and their configuration to define a physical layer proposal.…”

“…First, narrowband and wideband soundings were performed in [6], in order to describe the channel performance. Afterwards, the system was improved in terms of sounding frequency availability and number of soundings per day, and more complete results were evaluated in [7], giving more details on the channel parameters. Also several modulation tests using spread spectrum modulations [8] have been performed, as well as Orthogonal Frequency-Division Multiplexing (OFDM) [9] and single carrier modulations [10].…”