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Doppler shift and communication delay variation characterization curves with the maximum elevation angle βmax = 30 • , 45 • and 90 • .
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The integration of satellite and terrestrial 5G networks aims to provide ubiquitous coverage, improve service reliability, and enable the network scalability. However, the inherent characteristics of satellite channels bring challenges on the air interface design of integrated terrestrial-satellite networks. For example, for low earth orbits (LEO)...
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... a LEO mobile SatCom system with a carrier frequency of 2.6GHz, a 600km altitude orbit, and the minimum elevation angle and the down-tilt angle being 10 • and 60 • , respectively, Fig.2 presents the Doppler shift value and the variation of propagation delay during the visible window. ...
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... To manage high data transfers and [21] enhance connectivity features, satellites in low -earth orbit (LEO) utilize a multitude of frequencies. The Ka -band and V -band are the two crucial bandwidths used by LEO satellites, each with its own set of benefits and drawbacks. ...
This research explores the Low Earth Orbit (LEO) satellite constellations, replicating the commercial OneWeb system. This work is divided into two key sections: Distance & Geometric Analysis and Link Performance Analysis. We start by designing a Walker-star network of 12 orbital planes featuring a dozen satellites orbiting 950 km above the Earth's surface. To enhance coverage and connectivity, we carefully adjust the constellation's phasing parameters in MATLAB. We set up links with the satellite network by fixing a ground station at RMIT University. After locating the satellites closest to the base terminal, we determine their distances and plot their azimuth and elevation values on Skyplot. In the second phase, a thorough link budget analysis is conducted, including a comparison of modulation techniques 4PSK and 16QAM. The purpose is to find the best method for terminal use out of the two modulation schemes.
... Given the rapid and dramatic changes in the channel environment of Low Earth Orbit (LEO) satellite mobile communication systems, signals are affected by various fading phenomena during transmission, resulting in inter-symbol interference in the received signal [21], [22]. Therefore, it is crucial to study reliable channel estimation to obtain exact channel state information (CSI) for minimizing interference from the channel to the signal. ...
... In doing so, the ocean disperses heat and evens out the unequal distribution of solar energy that strikes Earth. Temperatures at the poles would be considerably lower, and temperatures in the tropics would be substantially higher without the currents that circulate the warm and cold seas [14]. The use of fossil fuels like natural gas, oil, and coal has boosted atmospheric carbon dioxide levels by 30% since 1950, which has led to an average temperature increase of 1.4°F throughout the course of the twentieth century. ...
... k l w , , 1 By combining Eqs. (14) and (15), we get the transformed objective for the direct IoTs asshown in (16) and (17): ...
Every day of the week, wireless communication is almost all around us. The Internet of Things (IoT) is a standard protocol used to describe the rapidly advancing technology in which almost every electronic device is or may be connected to the Internet. These electronic gadgets constantly provide data signals to the gateways, which satellites such as those in Low Earth Orbit may transmit. Because of these networks’ limited resources and the IoT, these transactions must be completed with the least amount of latency and data loss possible. We also analyze the performance implications of implementing RF-based powering for such a network. The techniques presented in this paper may benefit the scientific community and industry in general when it comes to the dynamic distributed parameter allocation methodology for IoT network devices. We will also discuss how research on animals and the natural environment has been impacted by IoT breakthroughs, in particular, animal sensors’ limits and incapacity to broadcast from everywhere. Our analysis illustrates the most effective data transmission technique and establishes the bounds of these restrictions. Furthermore, the physics of the RF channel plays a critical role in the uncertainty of the channel as well as the amount of energy harvested. By employing simulation based on the physics of the RF channel, the article shows the performance of the system considering both the uncertainty of data arrival as well as the variability of the channel. The findings of the simulation show that the devices consume less energy overall as the signal-to-noise ratio rises. Furthermore, a timing factor of 10–15% is shown to be effective in maintaining a constant mean rate and increasing the energy efficiency of the system.
... Step 1: Set y Ns = ⌈N sample /N ⌉ Step 9: Find the maximum for each segment, and select the peak location greater than the threshold using (9), and substitute those values to (8) for residual Doppler frequency estimation ...
In recent years, integrating Non-Terrestrial Networks (NTN) components with 5G Terrestrial Networks (TN) has led to considerable attention from academia and industry, leading to the standardization of 5G-NTN in 3GPP. Among the various NTN solutions, a notable one is the Low Earth Orbit (LEO)-based 5G-NTN with a regenerative payload. This system stands out because it can provide latency and throughput levels similar to terrestrial 5G networks. However, a significant challenge in this integration arises from the substantial Doppler effect caused by the rapid movement of LEO satellites. This effect must be effectively addressed to establish a successful data link between the User Equipment (UE) and the gNodeB (gNB). This study proposes a simple yet efficient method to tackle this issue. The method involves using a regenerative LEO satellite-based 5G gNB, which pre-compensates the Doppler frequency with respect to its beam center before initiating any data transmission. Subsequently, the UE performs postcompensation to handle residual Doppler frequency and achieve accurate initial synchronization. We evaluated the performance through simulations and demonstrated the effectiveness of the proposed system. The results indicate successful mitigation of Doppler effects, facilitating seamless communication between LEO satellite-based 5G NTN.
... A random access (RA) technique without requiring any modification to the current narrowband Internet of Things RA waveform for multiuser time frequency synchronization and TA for data scheduling was proposed in [8]. A local synchronization sequence by using modulated discrete prolate spheroidal sequence vectors and recast the timing offset estimation as a one-dimensional peak search problem was proposed [9]. In [10], the authors investigated location-based TA estimation for 5G integrated low Earth orbit (LEO) satellite communication systems. ...
... Although consensus on specific demands of 6G has not been reached, ubiquitous global network coverage, higher data transmission rates, lower propagation delays, and higher energy efficiency (EE) are widely agreed. Under this circumstance, satellite communications that can achieve global coverage and long-distance communications could be an indispensable part of 6G [5][6][7][8][9][10][11]. ...
Satellite communication is an indispensable part of future wireless communications given its global coverage and long-distance propagation. In satellite communication systems, channel acquisition and energy consumption are two critical issues. To this end, we investigate the tradeoff between the total energy efficiency (TEE) and minimum EE (MEE) for robust multigroup multicast satellite communication systems in this paper. Specifically, under the total power constraint, we investigate the robust beamforming aimed at balancing the TEE-MEE, so as to achieve the balance between the fairness and total performance on the system EE. For this optimization problem, we first model the balancing problem as a nonconvex problem while deriving its approximate closed-form average user rate. Then, the nonconvex problem is handled by solving convex programs sequentially with the help of the semidefinite relaxation and the concave-convex procedure. In addition, depending on the solution rank value, Gaussian randomization and eigenvalue decomposition method are applied to generate the feasible solutions. Finally, simulation results illustrate that the proposed approach can effectively achieve the balance between the TEE and MEE, thus realizing a tradeoff between fairness and system EE performance. It is also indicated that the proposed robust approach outperforms the conventional baselines in terms of EE performance.
... As a result, current terrestrial GFRA schemes are not directly applicable to LEO satellite communications. To facilitate transmissions, precompensation technique [7] for delay and Doppler shift may be adopted before GFRA, but it introduces extra complexity which may decrease the battery life of remote IoT devices, and the most of conventional schemes cannot handle the Doppler spread effectively. ...
This paper investigates joint device identification, channel estimation, and signal detection for LEO satellite-enabled grant-free random access, where a multiple-input multipleoutput (MIMO) system with orthogonal time-frequency space modulation (OTFS) is utilized to combat the dynamics of the terrestrial-satellite link (TSL). We divide the receiver structure into three modules: first, a linear module for identifying active devices, which leverages the generalized approximate message passing (GAMP) algorithm to eliminate inter-user interference in the delay-Doppler domain; second, a non-linear module adopting the message passing algorithm to jointly estimate channel and detect transmit signals; the third aided by Markov random field (MRF) aims to explore the three dimensional block sparsity of channel in the delay-Doppler-angle domain. The soft information is exchanged iteratively between these three modules by careful scheduling. Furthermore, the expectation-maximization algorithm is embedded to learn the hyperparameters in prior distributions. Simulation results demonstrate that the proposed scheme outperforms the conventional methods significantly in terms of activity error rate, channel estimation accuracy, and symbol error rate.
... Closedform expressions for the throughput, EE, and DOR of the considered LEO STT system will be derived in each adaptive transmission scheme. Besides, we assumed that Doppler frequency shift, caused by the mobility of the satellite, can be estimated perfectly and mitigated by the mature precompensation method [27], [43]. Moreover, we assume that the channel is perfectly estimated with pilot signals [44] at the terrestrial terminal and known to the terrestrial terminal, through a noiseless feedback channel. ...
In this paper, we investigate the effect of the strong time-varying transmission distance on the performance of the low-earth orbit (LEO) satellite-terrestrial transmission (STT) system. We propose a new analytical framework using finite-state Markov channel (FSMC) model and time discretization method. Moreover, to demonstrate the applications of the proposed framework, the performances of two adaptive transmissions, rate-adaptive transmission (RAT) and power-adaptive transmission (PAT) schemes, are evaluated for the cases when the transmit power or the transmission rate at the LEO satellite is fixed. Closed-form expressions for the throughput, energy efficiency (EE), and delay outage rate (DOR) of the considered systems are derived and verified, which are capable of addressing the capacity, energy efficiency, and outage rate performance of the considered LEO STT scenarios with the proposed analytical framework.
... Closedform expressions for the throughput, EE, and DOR of the considered LEO STT system will be derived in each adaptive transmission scheme. Besides, we assumed that Doppler frequency shift, caused by the mobility of the satellite, can be estimated perfectly and mitigated by the mature precompensation method [27], [43]. Moreover, we assume that the channel is perfectly estimated with pilot signals [44] at the terrestrial terminal and known to the terrestrial terminal, through a noiseless feedback channel. ...
In this paper, we investigate the effect of strong time-varying transmission distance on the performance of the low earth orbit (LEO) satellite-terrestrial transmission (STT) system. We propose a new analytical framework of using the finite-state Markov channel (FSMC) model and time discretization method. Moreover, to demonstrate the applications of the proposed framework, the performances of two adaptive transmissions, rate-adaptive transmission (RAT) and power-adaptive transmission (PAT) schemes, are evaluated for the cases when the transmit power or the transmission rate at the LEO satellite is fixed. Closed-form expressions for the throughput, energy efficiency (EE), and delay outage rate (DOR) of the considered systems are derived and verified, which are capable of addressing the capacity, energy efficiency, and outage rate performance of the considered LEO STT scenarios with the proposed analytical framework.
... Thus, maintaining a prescribed level of quality of service becomes significantly challenging, especially for IoT technologies that employ random access via the shared radio spectrum. In order to maximize the performance of these systems, various aspects of IoT-over-Satellite systems are investigated in the literature, such as the performance analysis of IoT-over-Satellite system using different communication schemes [5]- [7], Doppler shift compensation [8], [9], Satellite antenna design [10], and under different network architectures [3], [11]. ...
Recent satellite constellations are being deployed to serve massive numbers of wireless devices, especially targeting those located in rural and offshore settings. Accordingly, business models relying on data reported via wireless Internet-of-Things (IoT) networks can now easily utilize satellite constellations to expand their offerings. In this paper, we present an analytic framework for modeling the uplink performance of massive IoT-over-Satellite networks. The framework utilizes tools from stochastic geometry to model the satellites and the users as two random point processes enabling the development of a tractable analytic model for the uplink outage probability. Furthermore, the paper derives the expected normalized throughput and compares the results to Monte-Carlo simulations for intractable constellations such as the Walker models adopted by current satellite deployments. Comparisons show that random constellations provide a tractable lower bound to the performance and average throughput compared to Walker constellations. The analytic model can provide the fast estimation of the uplink performance aiding in designing the IoT-over-Satellite system.
