Enabling Satellite Communication Technologies

Digital predistortion (DPD), based on complex-valued memory polynomials (MP), is established as an efficient method for power amplifier (PA) linearization. The DPD facilitates compliance of the telecommunication infrastructure to strict standard specifications (transmit spectrum mask (TSM), error vector magnitude (EVM), bit error rate (BER), [Formula: see text]) by making PA more linear, while at the same time reduces the running cost of the wireless infrastructure (at both Base Transceiver Station (BTS) and User Equipment (UE) sides) by making PA more power efficient. Even when DPD is utilized, signals with high peak-to-average power ratio (PAPR) produce out-of-band PA spectrum emission due to intermodulation products affecting all above-mentioned critical standard specified parameters. The novelty proposed in this paper is as follows. PA is restricted to operate within “reasonably above” PA linear region using PAPR reduction technique. The residual nonlinearity is taken care of by DPD. The combination of DPD and PAPR PA linearization methods is implemented on software-defined radio board. The necessary steps for efficient PA linearization are presented, compensating both out-of-band and in-band signal distortions. We achieved EVM = 2.0%, ACPR [Formula: see text]50[Formula: see text]dBc, at 10[Formula: see text]W LTE modulated PA output, antenna point and PA output power of 39.5[Formula: see text]dBm.

Long-term-evolution (LTE) communication enables high data-rates but degrades the efficiency of the power amplifiers (PAs) due to high peak-to-average power ratios of transmitted signals. Envelope tracking (ET) and envelope-elimination-and-restoration (EER) techniques have been proposed to improve the PA efficiency by adapting the PA supply voltage to the envelope. Linear PAs in ET systems are mostly implemented in non-CMOS technologies for high efficiency [1]. However, the growing demand for low-cost integrated systems has motivated the use of CMOS PAs [2]. The main drawback of this is that linear CMOS PAs have poor efficiency. The high efficiency of switching PAs makes them a promising candidate in CMOS [3]. In EER systems, where switching PAs are used, the supply modulator must satisfy stringent noise and bandwidth specifications in order to recover the amplitude information of the LTE signal. Thus, it is a challenge for supply modulators to maintain high efficiency. Recently, a number of methods have been adopted to improve supply-modulator efficiency. In [1], a dual-switching topology is proposed, but it requires an additional inductor and results in an unpredictable noise spectrum. In [4], an AC-coupling topology is adopted to reduce the supply voltage of the linear amplifier. However, due to the slow response of the switching amplifier, the efficiency is still low.

[Abstract] This paper proposes dynamic bandwidth/channel access technique using FFT based block signal transmission for future broadband mobile satellite communication systems, which is to supplement next generation terrestrial mobile networks. One of the key issues for next generation mobile satellite communication systems is flexible and scalable access technique in terms of data rate and traffic type, to accommodate various satellite users. OFDMA is a technique to meet the above-mentioned requirements, however it needs large output backoff at HPA. To solve this problem, this paper proposes a new bandwidth/channel access technique using FFT based block signal transmission. The proposed technique uses single carrier modulation suitable for small output backoff operation in HPA, keeping flexibility and scalability as OFDMA has. This paper describes basic principle of the proposed dynamic bandwidth/channel access technique and preliminary performance evaluation results by computer simulation.

In the world of portable wireless electronics, battery life and therefore power efficiency are key parameters, and RF power amplifiers (PAs) are severe limiting agents in this regard because of their power-intensive demands. Spectral density is also critical to extend the effective bandwidth of a wireless transmitter, which is why linear PAs are popular, in spite of their inherently low power efficiency levels. An asynchronous power-tracking scheme is therefore proposed to more efficiently power-condition the supply of linear RF PAs and extend overall battery life performance. The RF supply is comprised of a high power but slow-responding voltage regulator with a lower power but fast-responding parallel nonlinear clamping circuit. Simulations with a SiGe HBT class-A RF PA show that the proposed circuit consumes 10-15% less total power and achieves 1.5% better overall power efficiency than the state-of-the-art power-tracking scheme while meeting the same error-vector magnitude (EVM) performance.

Experiments on mobile satellite communications are being carried out to determine if they are technically feasible for future domestic satellite services in the Experimental Mobile Satellite System project, which uses Engineering Test Satellite-V. Experimental ISDN (integrated services digital network) basic-rate communications services have also been offered for marine vehicles. The authors describe the configuration of an experimental system for maritime ISDN satellite communications, and the characteristics of ISDN basic-rate interface connections for the digital telephones, G4 facsimiles, and color video-phone terminals of terrestrial ISDN services. This experiment provided much information for designing future mobile satellite communications systems. Moreover, it indicates that forward error correction in a mobile satellite link with poor transmission quality is very effective at improving the communication quality of mobile satellite systems. >

Future sixth-generation (6G) low Earth orbit (LEO) satellite systems will utilize large-scale multi-beam phased arrays operating at millimeter-wave (mmWave) frequencies, with embedded power amplifiers (PAs) at each antenna element. However, the severe path loss drives PAs near saturation, and dynamic beamforming leads to nonuniform, time-varying PA conditions, jointly resulting in complex memory nonlinearities that degrade system performance. Such in-band distortions require mitigation by PA linearization, which remains highly constrained in LEO satellite systems. Therefore, accurate modeling and quantification of these nonlinearities are critical for realistic performance evaluation and to guide the development of effective linearization strategies. Current analytical methods focus on single-PA or memoryless-array models, without addressing the frequency-dependent statistical characteristics and spatially varying radiation patterns of nonlinear distortions in multi-beam phased arrays. In this paper, we develop statistical models for the PA output and the received signals in multi-beam phased arrays, explicitly decomposing the distortion structure and deriving closed-form expressions for each distortion component’s statistical properties. Furthermore, we analyze the spatial beam-pattern distortions and derive a closed-form expression for the signal-to-distortion-plus-interference-and-noise ratio (SDINR) under nonlinear distortion. Extensive simulations, conducted measurements, and over-the-air (OTA) experiments validate that the proposed model reduces optimal input back-off estimation error by 2 dB and improves SDINR prediction accuracy by approximately 3 dB. This research establishes a robust analytical foundation for future LEO satellite system design and linearization technology development.

The blower with Active Magnetic Bearing (AMB) has the advantage of high speed, high reliability, small size, good adaptability. Power amplifier is an important part of the magnetic bearing system, directly determines the magnetic bearing system performance. The three-level PWM signal generation algorithm is analyses in this paper, and the IR2113 gate driven circuits with a negative bias is designed, and build a three-level magnetic bearing power amplifier. The gate driven signal of circuit is test, and entire power amplifier tracking step signal and sinusoidal signal also be test, the test results indicate that the three-level power amplifier meet the design requirements. At last, the power amplifier application on the blowers with AMB successful. Introduction Active Magnetic Bearings (AMB) using electromagnetic force to suspend rotor, with no friction loss, no lubrication, high-speed, non-polluting characteristics.The blower with AMB has the advantage of high speed, high reliability, small size, good adaptability Power amplifier is an important part of the overall magnetic bearing system, directly determines the magnetic bearing system performance . Depending on the realization of the principle, magnetic bearings power amplifier divided into linear power amplifier and switching power amplifier. With respect to the linear power amplifier, switching power amplifier has the advantage of low power consumption and high conversion efficiency; occupy a dominant position in large power amplifiers. Switching power amplifier can be divided into two-level amplifier switching amplifier and three-level switching amplifier depending on the switching signal. In two-level switching amplifier, the magnitude of current ripple is related to the DC voltage. Increases the DC voltage to improve the dynamic characteristics of the system, it will increase the electromagnetic coil current ripple at the same time. The current ripple of three-level switching power amplifier is not only smaller than the two-level power amplifier, but also nothing affected by the DC voltage , and therefore more suitable for high-power active magnetic bearings. In this paper, using FPGA chip to generate three-level switching signals, half-bridge circuit using IGBT modules and IGBT gate drive circuit is designed based on the drive requirements. The Three-level PWM Signal Generation Algorithm: D2 L Drive circuit FPGA Current sensor feedback AD circuit A D1 Vref S1 S2 I Reference signal Q1

This study proposes a reinforcement learning-based link selection method for Low Earth Orbit satellite networks, aiming to reduce handover frequency while extending link duration under highly dynamic orbital environments. The proposed approach relies solely on basic satellite positional information, namely latitude, longitude, and altitude, to construct compact state representations without requiring complex sensing or prediction mechanisms. Using relative satellite and terminal geometry, each state is represented as a vector consisting of azimuth, elevation, range, and direction difference. To validate the feasibility of policy learning under realistic conditions, a total of 871,105 orbit based data samples were generated through simulations of 300 LEO satellite orbits. The reinforcement learning environment was implemented using the OpenAI Gym framework, in which an agent selects an optimal communication target from a prefiltered set of candidate satellites at each time step. Three reinforcement learning algorithms, namely SARSA, Q-Learning, and Deep Q-Network, were evaluated under identical experimental conditions. Performance was assessed in terms of smoothed total reward per episode, average handover count, and average link duration. The results show that the Deep Q-Network-based approach achieves approximately 77.4% fewer handovers than SARSA and 49.9% fewer than Q-Learning, while providing the longest average link duration. These findings demonstrate that effective handover control can be achieved using lightweight state information and indicate the potential of deep reinforcement learning for future LEO satellite communication systems.

High Throughput Satellite (HTS) systems still offer much less bandwidth per user with respect terrestrial broadband networks. In order to reach a very high throughput towards “Tbit/s connectivity”, an important breakthrough is needed in terms of bandwidth availability which can be offered by the use of Extremely High Frequency (EHF) bands (30–300 GHz). In particular, Q-V band (30–50 GHz) and W-band (70–110 GHz) offer very promising perspectives, being not used for commercial systems and offering a large part of the spectrum allocated for satellite services. However, it is well known that EHF band transmission through the atmosphere is subject to absorption and dispersive effects in amplitude and phase that have to be carefully characterized. In this framework, some mitigation techniques have to be analyzed and properly tuned in order to realize an efficient transmission. In this paper, the current experimental activities to support future EHF satellite communication systems are reported, with reference to the Italian Space Agency Q/V-band satellite communication experimental campaign. In particular, a new error model for QPSK modulation scheme has been developed from the experimental data. This error model can be used for the design of optimized channel coding and adaptive transmission schemes for Q/V band satellite channels.

The design of a K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</inf> -band coplanar waveguide slot-coupled patch antenna ESA with integrated MEMS phase shifters has been described above. The incorporation of MEMS phase shifters into the ESA design results in a compact, efficient uplink mechanism for a future Army satellite communication system. A control board for biasing the phase shifters and initiating beam steering will be incorporated into the final array. The details of this design and the measured beam steering results of the fully-fabricated demonstrator array will be presented at the 2009 IEEE Antennas and Propagation Society Conference.

This paper considers satellite communication networks where each satellite terminal is equipped with energy harvesting (EH) devices to supply energy continuously, and randomly transmits bursty packets to a geostationary satellite over a shared wireless channel. Packet replicas combined with a successive iteration cancellation scheme can reduce the negative impact of packet collisions but consume more energy. Hence, appropriate energy management policies are required to mitigate the adverse effect of energy outages. Although centralized access schemes can provide better performance on the networks’ throughput, they expend extra signallings to allocate the resources, which leads to non-negligible communication latencies, especially for the satellite communication networks. In order to reduce the communication overhead and delay, a distributed random access (RA) scheme considering the energy constraints is studied. Each EH satellite terminal (EH-ST) decides whether to transmit the packet and how many replicas are transmitted according to its local energy and EH rates to maximize the average long-term network throughput. Owing to the nonconvexity of this problem, we adopted a game theoretic method to approximate the optimal solution. By forcing all the EH-STs to employ the same policy, we characterized and proved the existence and uniqueness of the symmetric Nash equilibrium (NE) of the game. Moreover, an efficient algorithm is proposed to calculate the symmetric NE by combining a policy iteration algorithm and the bisection method. The performance of the proposed RA scheme was investigated via numerous simulations. Simulation results showed that the proposed RA scheme is applicable to the EH devices in the future low-cost interactive satellite communication system.

The scope of the present paper is to outline ESA’s R&D directions for the development of new technologies required for future broadband satellite communication systems. The document outlines likely trends and technological issues that will need to be tackled in the medium and long term (e.g. 5 to 10 years) to improve by more than one order of magnitude satellite communication networks efficiency, thus increasing their economical appeal. It is shown that by timely developing in a co-ordinated fashion a number of techniques and technologies encompassing both ground and space segment it is possible to attain the ambitious target set forth above.

Many waveforms for future military satellite communication systems rely on spectrally-confined waveforms to increase the number of users and maintain capacity. These waveforms stress the performance of the transmitting amplifiers. The design and planning stages of communication systems often use memory-less nonlinear models, such as amplitude-to-amplitude modulation and amplitude-to-phase modulation models. These models are based on single-tone measurements and do not accurately predict the amplifier performance for wider bandwidth modulations. This paper presents measured comparisons of single-tone characteristics and spectrally-confined waveform performance in solid-state amplifiers at millimeter-wave frequencies. Measurements are performed over a range of data rates with PSK and QAM modulations, with comparison of devices with and without nonlinear memory.

This paper presents the 128-Channel Multicarrier Demodulator (MCD) developed at Bosch Telecom for use in the future European OBP satellite communications system. The development has been supported by the European Space Agency (ESA). In the uplink of this communication system a Multi-Frequenc y Time Division Multiple Access (MF-TDMA) scheme is used. The MCD presented here is capable of demultiplexing and demodulating of a MF-TDMA carrier group with a total bandwidth of 70 MHz comprising 128 single carriers. The MCD equipment consists of three major units: - the service board containing the power supply, clock generation and TM/TC interface. - the analog input section for down converting the input IF to an intermediate frequency suitable for A/D conversion.

A multibeam digital beamforming (DBF) antenna, developed for a future mobile satellite communications system, is mounted on a vehicle for a receiving experiment in a mobile environment using a satellite signal in the L band. The multibeam is formed by 2-dimensional FFT signal processing. Automatic acquisition and tracking of an arriving signal are achieved by selecting a maximum beam out of the multiple beams in real-time.