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The relative Doppler shift F and its time derivative during the passing of the satellite at 200 km height over the ground station. The satellite is at the zenith at the time t = 0. Bold points show times for which laboratory measurements were carried out.
Source publication
We report the results of the feasibility study of using LoRa modulation for radio communications between CubeSat at low Earth orbit and ground station. The main goal of the study is to define how Doppler effect affects a LoRa radio link. Results of laboratory testing have shown high immunity of LoRa radio link to Doppler shift and a possibility to...
Contexts in source publication
Context 1
... our experiments, the NI PXIe-5672 vector signal generator synthesized a RF LoRa signal with a frequency varying due to the Doppler effect in accordance with Figure 2. That is the synthesized RF signal takes into account the dynamic Doppler Effect -the changing with time Doppler shift. ...
Context 2
... the first set, the transmission time of a LoRa packet is close to the lowest possible in the standard LoRa for maximum payload size, and in the second set, it is close to the maximum possible one. Bold points in Figure 2 show the most specific elements of satellite trajectory in the context of the radio link conditions covering all extreme situations. These situations are the largest static Doppler effect when the satellite is near the horizon, the largest dynamic Doppler effect when the satellite is at the zenith, and simultaneous high Doppler shift and high velocity of its changes when the satellite is in the intermediate position. ...
Context 3
... determine the LoRa radio link immunity margin at each selected elements of satellite trajectory, the LoRa modulated radio link was tested for several F values and its derivative. First, tests were carried out at nominal values, which are calculated by the formula (3) and are shown in Figure 2. Then the Doppler shift was multiplied by the escalation factor Q > 1, and the tests were repeated for various increasing values of Q until the connection was lost. ...
Similar publications
Currently, LoRa technology is one of the most promising technologies in satellite Internet of Things. Particularly those based on satellite constellations in low Earth orbit, including the CubeSat nanosatellite constellations. However, the LoRa specification does not contain clear criteria for the applicability of the LoRa modulation under strong D...
Citations
... Only a few studies assess the LoRa robustness against the Doppler effect in LEO satellite scenario. In [23], the first study was presented that aimed at evaluating the impact of the Doppler effect on the LoRa modulation in an attempt to understand the stability of LoRa DtS communications. Specifically, laboratory experiments were conducted to test the LoRa modulation with a carrier frequency of 430 MHz and a CubeSat orbiting at 200 km. ...
... Following the laboratory and outdoor tests, the authors of [6], [23] launched a Norby-CubeSat with an on-board SX1278 transceiver, which orbits at 560 km and operates at 436.7 MHz [24]. In [9], the first flight-testing experiments are described, establishing the foundation for understanding the LoRa modulation's capabilities and constraints at 436.7 MHz. ...
... Specifically, 20 experiments were carried out to examine the LoRa robustness against the Doppler effect for different SFs, bandwidths and payload (P L ) size. Similar to results in [6], [23], the flight-testing experiments confirm LoRa's strong immunity to the Doppler effect when using 7 ≤ SF ≤ 11 and bandwidth B > 31.25 kHz. These experiments 1 assess the LoRa DtS performance accounting for both the Doppler shift and the Doppler rate, and key findings are: ...
The Long Range (LoRa) modulation enables low-cost and low-power communications, serving as the foundation for the widely adopted terrestrial low-power wide-area network (LPWAN) technology known as LoRaWAN. Owing to its effectiveness, this modulation scheme is emerging as a potential option to provide direct-to-satellite (DtS) connectivity supporting internet-of-things (IoT) applications in remote or hard-to-reach areas, and complementing existing terrestrial networks. Besides the link budget and interference, the Doppler effect is one of the main challenges in LoRa DtS connectivity. Earlier studies have extensively investigated the link budget and the network scalability aspects, confirming the feasibility of integrating LoRa with Low Earth Orbit (LEO) satellites. However, only a few studies examine the influence of the Doppler effect on LoRa DtS performance. Specifically, the majority of the available literature report empirical studies that analyze the Doppler effect solely for a specific set of communication parameters. There remains a need for extensive and comprehensive examination of LoRa DtS performance under a strong Doppler effect in the LEO scenario. In this paper, we discuss and thoroughly investigate the impact of the Doppler effect on the reliability of LoRa satellite links. In particular, we analytically study packet losses, distinguishing the effect of Doppler shift from Doppler rate, the latter being caused by the variation in the relative speed of LEO satellites with respect to a terrestrial IoT end-device. Our analysis accounts for the effects of key communications parameters and settings, such as bandwidths, carrier frequency, MAC payload, LEO satellite’s orbital height, and LoRaWAN low data rate optimization (LDRO). Notably, the results identify the LoRa boundaries for direct to LEO satellite connectivity and can facilitate the selection of suitable parameters for future system designs. Specifically, our results demonstrate that the packet delivery ratio of the most vulnerable spreading factor, i.e., SF12, exceeds 82% when using 125 kHz bandwidth, 433 MHz carrier frequency, and 59 bytes payload for a satellite orbiting at 560 km height.
... Low earth orbit satellites (LEO) using LoRa are being used for IoT applications [30, 31,32], so the tiny gamma radiation classifier could be deployed to measure radiation on board of a small satellite. ...
Machine Learning has introduced many solutions in data science, but its application in IoT faces significant challenges, due to the limitations in memory size and processing capability of constrained devices. In this paper we design an automatic gamma radiation detection and identification embedded system that exploits the power of TinyML in a SiPM micro radiation sensor leveraging the Edge Impulse platform. The model is trained using real gamma source data enhanced by software augmentation algorithms. Tests show high accuracy in real time processing. This design has promising applications in general-purpose radiation detection and identification, nuclear safety, medical diagnosis and it is also amenable for deployment in small satellites.
... Doppler effect on the LoRa modulation adopted for ground-to-space communication was presented as a major issue facing the advancement of the CubeSat industry. Multiple works deal with this issue [194], [195], [192], Authors in [195] identified the doppler frequency shift resulting from the high speed of these nanosatellites passing over the ground station. This study consists of a laboratory experiment of the LoRa modulation under similar conditions to Cubsat flaying in LEO to ground communication. ...
... Doppler effect on the LoRa modulation adopted for ground-to-space communication was presented as a major issue facing the advancement of the CubeSat industry. Multiple works deal with this issue [194], [195], [192], Authors in [195] identified the doppler frequency shift resulting from the high speed of these nanosatellites passing over the ground station. This study consists of a laboratory experiment of the LoRa modulation under similar conditions to Cubsat flaying in LEO to ground communication. ...
Long Range (LoRa) is the most widely used technology for enabling Low Power Wide Area Networks (LPWANs) on unlicensed frequency bands. Despite its modest Data Rates (DRs), it provides extensive coverage for low-power devices, making it an ideal communication system for many Internet of Things (IoT) applications. In general, LoRa radio is considered as the physical layer, whereas Long Range Wide Area Networks (LoRaWAN) is the MAC layer of the LoRa stack that adopts star topology to enable communication between multiple End Devices (EDs) and the network Gateway (GW). The Chirp Spread Spectrum (CSS) modulation deals with LoRa signals interference and ensures long-range communication. At the same time, the Adaptive Data Rate (ADR) mechanism allows EDs to dynamically alter some LoRa features such as the Spreading Factor (SF), Code Rate (CR), and carrier frequency to address the time variance of communication conditions in dense networks. Despite the high LoRa connectivity demand, LoRa signals interference and concurrent transmission collisions are major limitations. Therefore, to enhance LoRaWAN capacity, the LoRa alliance released many LoRaWAN versions, and the research community provided numerous solutions to develop scalable LoRaWAN technology. Hence, we thoroughly examined LoRaWAN scalability challenges and the state-of-the-art solutions in both the PHY and MAC layers. Most of these solutions rely on SF, logical, and frequency channel assignment, while others propose new network topologies or implement signal processing schemes to cancel the interference and allow LoRaWAN to connect more EDs efficiently. A summary of the existing solutions in the literature is provided at the end of the paper by describing the advantages and drawbacks of each solution and suggesting possible enhancements as future research directions.
... During the development of the BRC, we conducted laboratory and outdoor experimental studies to determine the possibility of applying LoRa modulation in CubeSat radio communication systems [12], [13]. The experiments showed that LoRa modulation has very high immunity to the Doppler effect. ...
... Weak signal due to CubeSat orientation (12) Low SNR due to ambient noise (12) Unclear (1) ...
... Weak signal due to CubeSat orientation (12) Low SNR due to ambient noise (12) Unclear (1) ...
At present, the use of LoRa modulation in satellite radio communications and the construction of a CubeSat constellation for the satellite Internet of Things based on LoRa technology has already begun. However, the limits of applicability of LoRa modulation in low-Earth orbits have not yet been established. This paper presents the results of the first flight tests of LoRa modulation for robustness against the Doppler effect in the satellite-to-Earth radio channel, carried out using a NORBY CubeSat operating at 560 km. Flight tests confirmed the very high immunity of LoRa modulation to the Doppler effect for modes with spreading factor
SF
≤ 11 and spread spectrum modulation bandwidth
BW
>31.25 kHz. LoRa modulation in these modes can be used in satellite communication without any limitations caused by the Doppler effect. For
BW
= 31.25 kHz, the LoRa radio channel is affected by the static Doppler effect. Communication with the satellite is possible in this case only at high elevation angles. For
SF
= 12, the dynamic Doppler effect becomes significant, and communication is possible only at low satellite elevation angles, which leads to the formation of a “hole” in the center of the coverage area directly below the satellite. In both cases, the duration of the communication session is significantly reduced because of the Doppler effect. In the case of
SF
= 11 and 12 at
BW
= 31.25 kHz, both static and dynamic Doppler effect catastrophically affect the LoRa radio channel, so that communication with the satellite becomes impossible.
... During the development of the on-board radio complex, we carried out laboratory and outdoor experimental studies to determine the possibility of applying LoRa modulation in CubeSat radio communication systems [6,7]. The experiments showed that the LoRa modulation has very high immunity to the Doppler effect. ...
The paper presents the NORBY 6U CubeSat nanosatellite, launched on 28 September 2020 into a low-Earth orbit. The design of NORBY is briefly described, the main characteristics of its subsystems are given, and the results of the first flight tests are presented. The main features of the NORBY design are full hardware duplication of all subsystems and information interfaces, as well as the use of LoRa modulation in radio communications between the satellite and a ground station. The first results of the NORBY flight tests confirm the effectiveness of the key technical solutions applied in the NORBY design. For the first time, the operability of the LoRa modulation in satellite radio communications has been experimentally confirmed. The LoRa satellite-to-ground radio channel functioned sustainably at all tested parameters.
... В то же время избыточность полосы пропускания канала относительно скорости передаваемой информации обеспечивает устойчивость технологии LoRa при возникновении эффекта Доплера в части изменения частоты сигнала (статистический эффект) и скорости его изменения (динамический эффект) [11][12][13][14][15][16]. Предел устойчивости к статическому изменению частоты, заявленный в технических описаниях чипов LoRa (SX1276/77/78/79, SX1272/73), составляет до 25% от ширины полосы частот канала при включенном режиме оптимизации структуры пакета. ...
Представлены технические параметры наиболее известных технологий LPWAN, большая часть которых относится к проприетарным. Особое место занимает LoRa – фактически единственная открытая технология. Как показал анализ возможности адаптации технологий LPWAN для использования в спутниковых сетях IoT, ориентированных на прямой доступ к оконечным устройствам, наиболее перспективная технология – LoRa. В статье приводятся графические данные взаимосвязи отношения сигнал/шум и вероятности ошибки на бит, которые обеспечивают объективную оценку бюджета абонентских радиолиний спутниковых каналов, реализованных на основе технологии LoRa.
... In [14], we performed laboratory experiments to test the LoRa modulation immunity to Doppler effect under conditions corresponding to satellite-to-Earth radio communication. A software-defined radio (SDR) transmitter was used in the experiments to synthesize a radio frequency signal with the LoRa modulation, taking into account the Doppler shift corresponding to the satellite-to-Earth radio channel. ...
... Thus, on the one hand, there is experimental data confirming the high robustness of the LoRa modulation to the Doppler effect [13], [14]. On the other hand, there is experimental data showing that the Doppler effect begins to have a significant impact on the LoRa radio channel at receiver speeds relative to the transmitter from about 8 km/h to 40 km/h [11], [12]. ...
... To do this, we performed additional laboratory and outdoor field experiments. In the laboratory, in addition to the previously performed measurements [14], we tested the LoRa modulation immunity to the Doppler effect for the same LoRa parameters that were used in [11]. We also checked, in the laboratory, the behavior of the LoRa receiver as it moves assuming multipath propagation of the LoRa signal, emulating the experimental conditions in [11] and [12]. ...
Currently, LoRa technology is one of the most promising technologies in satellite Internet of Things. Particularly those based on satellite constellations in low Earth orbit, including the CubeSat nanosatellite constellations. However, the LoRa specification does not contain clear criteria for the applicability of the LoRa modulation under strong Doppler effect conditions caused by the very high speed of satellites. This is especially true in the case of the dynamic Doppler effect, when the Doppler frequency shift changes rapidly with time. This paper presents the results of laboratory testing and outdoor experiments conducted to determine the feasibility of the LoRa modulation in CubeSat radio communication systems. Additionally, possible restrictions associated with the Doppler effect were explored. The experiments showed that the LoRa modulation has very high immunity to the Doppler effect. This immunity allows for the use of LoRa modulation in satellite radio communications in orbits above 550 km without any restrictions associated with the Doppler effect. In lower orbits, the dynamic Doppler effect leads to the destruction of the satellite-to-Earth radio channel when using the LoRa modulation mode with a maximum spreading factor of SF = 12. This destruction occurs when the satellite is flying directly above the ground station, resulting in reduced duration of the radio communication session. The reduction in the duration of a communication session increases with decreasing orbit altitude and reaches about one minute in an ultra-low orbit 200 km high.
... Additional research is needed to explore the requirements of compatibility in terms of MAC protocols, network architecture and united service patterns [10]. Another innovative line studied the behavior of an LPWA link to enable connectivity from the nanosatellite to a gateway on Earth [70,71]. Further research and experimentation will help understand and design an integrated platform that takes advantage of the different wireless technologies involved in these hybrid solutions. ...
Extending the internet of things (IoT) networks to remote areas under extreme conditions or for serving sometimes unpredictable mobile applications has increased the need for satellite technology to provide effective connectivity. However, existent medium access control (MAC) protocols deployed in commercial satellite networks were not designed to offer scalable solutions for the increasing number of devices predicted for IoT in the near future, nor do they consider other specific IoT characteristics. In particular, CubeSats—a low-cost solution for space technology—have the potential to become a wireless access network for the IoT, if additional requirements, including simplicity and low demands in processing, storage, and energy consumption are incorporated into MAC protocol design for satellite IoT systems. Here we review MAC protocols employed or proposed for satellite systems and evaluate their performance considering the IoT scenario along with the trend of using CubeSats for IoT connectivity. Criteria include channel load, throughput, energy efficiency, and complexity. We have found that Aloha-based protocols and interference cancellation-based protocols stand out on some of the performance metrics. However, the tradeoffs among communications performance, energy consumption, and complexity require improvements in future designs, for which we identify specific challenges and open research areas for MAC protocols deployed with next low-cost nanosatellite IoT systems.
Long-range (LoRa) technology is most widely used for enabling low-power wide area networks (WANs) on unlicensed frequency bands. Despite its modest data rates, it provides extensive coverage for low-power devices, making it an ideal communication system for many internet of things (IoT) applications. In general, LoRa is considered as the physical layer, whereas LoRaWAN is the medium access control (MAC) layer of the LoRa stack that adopts a star topology to enable communication between multiple end devices (EDs) and the network gateway. The chirp spread spectrum modulation deals with LoRa signal interference and ensures long-range communication. At the same time, the adaptive data rate mechanism allows EDs to dynamically alter some LoRa features, such as the spreading factor (SF), code rate, and carrier frequency to address the time variance of communication conditions in dense networks. Despite the high LoRa connectivity demand, LoRa signals interference and concurrent transmission collisions are major limitations. Therefore, to enhance LoRaWAN capacity, the LoRa Alliance released many LoRaWAN versions, and the research community has provided numerous solutions to develop scalable LoRaWAN technology. Hence, we thoroughly examine LoRaWAN scalability challenges and state-of-the-art solutions in both the physical and MAC layers. These solutions primarily rely on SF, logical, and frequency channel assignment, whereas others propose new network topologies or implement signal processing schemes to cancel the interference and allow LoRaWAN to connect more EDs efficiently. A summary of the existing solutions in the literature is provided at the end of the paper, describing the advantages and disadvantages of each solution and suggesting possible enhancements as future research directions.
