Adaptive filtering and its applications in satellite communications

Turbo codes have a wide range of applications in 3G mobile communications, deep-sea communications, satellite communications and other power constrained fields. In the paper, the Turbo Code Decoding Principle and several major decoding methods are introduced. Simulations of Turbo code performance under different parameters of AWGN channel are made and the effects of the different interleaving length, the number of iterations, and the decoding algorithm to Turbo code performance are also discussed in AWGN channel. Simulation results show that under the same signal-to-noise ratio, the more the number of iterations is, the longer the sequence of information is, and the more excellent decoding algorithm is, the better the performance of Turbo codes is.

For the next generation applications in mobile communication, radar and satellite communication we need the devices that can operate at high frequencies and high power with minimum power consumption. There is a growing importance in the recent years for the development of GaN transistors.This paper presents design of the power efficient GaN based high power amplifier operating in the bandwidth of 5GHz – 7GHz based on a 12 Watt Discrete Power GaN on SiC HEMT from TriQuint. In this manuscript the design of RF power amplifier, its stability, input and output matching impedance and performance for 5-7GHz is presented. Design and simulations of the power amplifier are carried out using Advanced Design System (ADS). Simulation results of device stability, gain and Power Added Efficiency (PAE) shows good accordance with the specifications and parameters of the device.In the design process, for better correlation in measurement and simulation results precision of passive element models are specially considered. In 1 dB compression point for the designed high power amplifier, the experiment and the simulation results show a Power Efficiency of 68%.

From the moment the air/aero/aerial objects appeared the necessity of monitoring for them arose and were solved using different tools, such as radio communications, radio direction finding, radar and others. With the advent of global satellite navigation, the massive introduction of navigation equipment began in almost all areas of human activity and especially in mobile (moving) objects (cars, aircraft, ships, etc.). This allowed aircraft crews to accurately determine their coordinates in real time under any weather conditions. However, the organization of uninterrupted data transmission to ground control centers remained problematic. In this regard, aircraft monitoring systems were primarily installed on military and civil aircraft, while the other categories and types of aircraft were equipped only with communication systems. Thus, currently, there is the lack of navigation devices allowing flight monitoring and communication in small aviation. As a result, in case of emergency landing of small aircraft, it takes a lot of time and effort to find its location, therefore providing emergency assistance to passengers and crew is not possible. This problem can be solved by the system for determining the location of small aircraft using technologies of global navigation satellite systems and mobile satellite communications. This system includes devices for registering the location of the observed object, transmitting data via mobile cellular and satellite communications, processing, storage and displaying of data. The proposed system, by continuously recording and transmitting aircraft location data to the ground control center, helps minimize time and narrow the search area of the aircraft that made an emergency landing.

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. >

This article introduces the basic principle of turbo codes and the basic overview of satellite communication system and analyzes the feasibility of turbo codes in satellite communication and proves its unique advantages over other coding methods in satellite communication through simulation. Finally, we analyze the performance of multiple turbo codes and discuss the feasibility of their application in satellite communication by combining the previous studies and make limitations on their performance above triple turbo codes.

For time-division multiplexed satellite communications links, a multi-rate waveform can enable substantial capacity gains over waveforms employing static coding and modulation. Using a multi-rate waveform such as DVB-S2 with adaptive coding and modulation (ACM), a user's data is transported with the most efficient modulation and forward error correction coding point that specific user can reliably receive. Many mobile satellite communication applications require a substantially smaller aperture or a lower-profile antenna as compared to typical fixed-site very small aperture terminals (VSATs) for which DVB-S2 was designed. Over a wide area of operation, these smaller mobile terminals often cannot establish a link that observes regulatory power-spectral density limits using even the most robust modulation and code point that the DVB-S2 waveform offers. By adding the concept of adaptive direct sequence spreading to the adaptive coding and modulation, a more capable multi-rate waveform emerges that addresses a comprehensive set of mobile terminal platform types and scenarios. In this paper, the Adaptive Coding Spreading and Modulation (ACSM) concept is described and the capacity gains are quantified for several case studies. Also, a blockage mitigation technique employed within the ACSM concept that enables communications on train or helicopter mounted platforms is discussed.

This paper presents a novel phased-array antenna system with multifrequency, full-duplex operation, and wide-beam scanning. The system consists of a wideband power divider, a low-loss and low-cost multiline phase shifter controlled by dual piezoelectric transducers (PETS), a four-channel multiplexer, microwave monolithic integrated circuit (MMIC) amplifiers, and a stripline-fed Vivaldi antenna array. The multiline PET phase shifter has a low perturbation loss of less than 2 dB and a total loss of less than 4 dB up to 40 GHz, with a maximum phase shift of 650/spl deg/. Using dual-aligned PETS for bidirectional phase shifting results in wide scan angles of 38.6/spl deg/, 37.6/spl deg/, 43/spl deg/, and 40/spl deg/ for the four channels at 10, 12, 19, and 21 GHz, respectively. The four-channel diplexer demonstrates low insertion loss with high isolation between channels. The new multifrequency phased-array system provides wide-beam scanning and full-duplex capability using a simple, low-cost architecture. The system can be used for applications in mobile satellite communications.

Dual-frequency microstrip antennas are expected to find applications in mobile satellite communications. The authors present a multiplayer microstrip structure with a radiating disc. Theoretical results are compared with experiment. Input impedance and mutual coupling between the two feeds are discussed.

Monofilar and multifilar helical antennas are the most widely proposed antennas in satellite communications systems. The main reason why these antennas constitute an asset in applications concerning satellite and space communications generally is circular polarization. Good axial ratio provides precise measurement of the polarization of the received signal due to immunity of the circularly polarized wave to Faraday rotation of the signal propagating through the ionosphere. In addition to circular polarization, monofilar helical antennas offer the advantage of high gain in axial direction over a wide range of frequencies which makes them suitable for applications in broadband satellite communications.

Mobile satellite communication is becoming a crucial component for broadcast and broadband coverage in professional, commercial, military and emergency scenarios. Mobile devices and network control center (NCC) are the basic components of Low-Earth-Orbit (LEO) satellites which communicate with each other with the help of gateways. The communication between these components needs high security. The various existing protocols for the environment of mobile satellite communication are insecure against numerous attacks and can be easily attacked by an adversary. So, there is an indispensable requirement of a reliable protocol which can offer efficient and secure communication for mobile satellite system. Therefore, a robust key agreement authentication scheme for mobile satellite environment is proposed in this article. The proposed protocol is developed according to the major security demands in the satellite communication networks. Our protocol provides mutual-authentication, session-key agreement and correct notion of user anonymity. The performance analysis for evaluation shows that the storage, communication and computation cost of the proposed protocol is less than many of existing protocols. Moreover, our protocol offers additional security features than that are available in the existing protocols. Hence, our protocol offers a secure authentication and key agreement for mobile satellite systems.

Communication satellites have a much longer propagation delay than terrestrial communication networks such as cellular or WiFi. In addition, as the carrier frequency moves up, mobile satellite communications show worse performances than the conventional fixed satellite communications. The mobile satellite service (MSS) has not been actively pursued with long latency at high-frequency bands for future applications. In this paper, the adverse impact of long propagation delay in the conventional satellite system is investigated with various user mobility and Doppler-shifted carrier frequency. The satellite network is modeled as a basic delayed feedback channel system and the communication performance is analyzed under delayed channel state information (CSI) for assessing the system feasibility in mobile conditions. The results of performance analysis are provided at high-frequency bands with high-speed user movement, specifically on the outage probability and the channel capacity exploiting three types of channel models: conventional land mobile satellite (LMS) channel models of E. Lutz and C. Loo, and Nakagami fading model. In the circumstance with various user speeds, system performances are evaluated with different propagation delays in the LMS channel models and for line-of-sight (LOS) components in the Nakagami fading. In addition, the conventional models are compared depending on different altitudes for geostationary orbit (GEO), medium earth orbit (MEO), and low earth orbit (LEO) satellites, as well as high-altitude platforms (HAP).

This paper discusses the design of an 8×8 phased array antenna tile for Ku-band mobile satellite communications. The array has low-profile, high-gain, and wide-angle scanning properties. The design steps and electromagnetic analysis of a dual-polarized radiating antenna element and an 8×8 array tile comprised of these radiating elements are presented. The array structure makes it possible for satellite communication (SATCOM) terminals with compact sizes, because the whole front-end might be on the same multilayer printed circuit board (PCB). With a compact geometry and 25% bandwidth, the array promises an excellent performance for satellite communication applications. The radiation characteristics and other array parameters are evaluated with respect to the application requirements.

We propose a low-profile broadband planar circularly polarized folded transmitarray antenna (CPFTA) based on well-designed top and bottom metasurfaces (MSs). The top MS is employed to reflect the x-polarized wave as a ground and, at the same time, to convert the y-polarized wave into circularly polarized waves with arbitrary phase shifts in the operation band. A bottom MS is applied to reflect the incident wave and twist its polarization by 90°. The whole CPFTA, including the feeding source of microstrip antenna, and the top and bottom MSs can be fully integrated and fabricated using low-cost printed circuit board technology. Both simulated and measured results demonstrate significant advantages of the proposed antenna, including broad bandwidth, high gain, lower profile, planar geometry, and easy integration. The fabricated sample shows 3 dB axial ratio (AR) bandwidth of 23.2%, 3 dBi gain bandwidth of 11.6%, and the maximum gain of 22.8 dBi at 10.3 GHz with the antenna efficiency of 21.8%. The proposed CPFTA is promising for applications in satellite communications with circularly polarized antennas.

A dual anode convergent electron gun of perveance 0.14μp has been designed for Ka-Band helix Traveling Wave Tube (TWT) which would ultimately have application in satellite communications. Gun has been designed using codes EGUN, TRAK & OMNITRAK. Pierce type electron gun with isolated beam forming electrode (BFE) & M-Type dispenser cathode with 3.1mm button diameter has been opted. It consists of two isolated anodes to meet the requirement of long life & high reliability. Initially, in cathode selection, life considerations are ignored, the gun is designed with available cathode. Periodic Permanent (PPM) focusing has been designed using Sm <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</inf> high intensity magnet in order to reduce the size & weight of the overall TWT. Confined flow beam focusing has been adopted. A compact small size electron gun assembly has been designed using ceramic insulator & suitable support structure. High voltage analysis has been carried out using code ESTAT. This paper presents the approach for overall design of gun assembly with dual anode.

Data transmission over the wireless transmission channel is adversely affected by attenuation, distortion, interference, and noise, that hampers the ability of the receiver to correctly receive the transmitted message signal. Thus error detection and correction methods are implemented to mitigate these effects. Convolution encoder is one such channel encoding technique used at transmitter end for deep space and wireless communication whereas at receiver end the Viterbi decoder decodes the encoded data. Viterbi algorithm is based on principles of maximum likelihood where the optimal trellis path is identified that is followed at the encoder using cumulative hamming distance. This paper presents an SoC based Hardware-Software codesign approach of implementing the Viterbi Decoder along with the entire communication system comperising of random binary pattern generator, convolution encoder, QPSK modulator, QPSK demodulator and quantizer built on a Zynq-7000 All Programmable SoC chip. The blocks are designed using Verilog HDL (Hardware Description Language) using the tools Vivado IDE (Integrated Development Environment) 2017.4 by Xilinx and HDL coder toolbox of MATLAB 2018 $a$ by MathWorks. Simulink model of the communication chain is implemented to simulate the design considering the effect of AWGN (Additive White Gaussian Noise) through the channel and then the partial design is translated to be implemented on a Zynq-7000 AP SoC. This design can find potential applications in Satellite communication, SDR (Software Defined Radio).