Mobile Satellite Channel Research Articles

Statistical channel modeling for low-elevation in LEO satellite communication

Channel modeling plays a crucial role in measuring wireless communication performance. This paper describes statistical channel modeling for a recorded signal from a ground station in an urban area in Tehran. This signal was recorded from the GRBALPHA satellite at 170–180° elevation and fixed azimuth. The three-state Markov channel modeling is used for this case. Markov models are often used for Land Mobile Satellite Channels (LMSC) because when the user is moving at different speeds between different environments, this causes, Variety in received power. By analyzing the communication channel in the lower elevations, the link budget can be designed with a suitable margin by considering the channel specification and its limitations. In addition to increasing communication time, reducing the bit error rate (BER), lowering costs, etc., this causes a more accurate channel analysis from the beginning to the end of the satellite passage.This work presents a statistical model for channel simulation using the Markov multi-state chain, estimating the Markov channel model between a fixed ground station and a Low Earth Orbit (LEO) Satellite at low elevations. The comparison of simulation data with recorded data demonstrates the proposed approach's effectiveness in modeling the channel.

Dynamic Mobile Satellite Channel Analysis in MEO Orbit Using Overlap and Overlay Approaches

Dynamic Mobile Satellite Channel Analysis in MEO Orbit Using Overlap and Overlay Approaches

Extensive analysis and evaluation of the DVB S2X superframe for multi-state land mobile satellite channel

The key enabling technology for satellite communication is the digital video broadcasting via satellite (DVB-S) standards. It featured high modulation and coding (MODCOD) schemes for reliable high quality communication link. Its operation under the clear line of sight condition has been outstanding. However, in situation where the user terminal is mobile, additional propagation challenges are introduced which further exhaust system resources and increase system design complexity. The extension of its second generation is the DVB-S2X, which offers additional functionality such as very narrow filtering roll-off factor and the superframe structure, suitable for operation at even very low signal-to-noise ratio (SNR). In this paper, a novel multi-state land mobile satellite (LMS) channel was modelled, leading to three different channel conditions – lightly-shadowed, shadowed and heavily-shadowed. Using these channels, the new system's performance is extensively analysed to determine the gains it offer to mobile channels. As a novel approach, the number of bundled Physical Layer (PL) frames contained in the superframe was made variable, and the results show that increasing the number of PL frames per superframe further improves system performance depending on the channel condition and MODCOD. For instance, for a lightly shadowed channel, superframe implementation for the 64-APSK (7/9) presents a 1 dB gain for 9 bundled PL frames and increasing the number of bundled PL frames to 12 offered an additional 0.7 dB gain. Thus, adaptive MODCOD may be combined with a variable-frame superframe implementation to improve the performance of a mobile satellite communication system and achieve a more efficient trade-off between power and spectral efficiencies than is possible with adaptive MODCOD alone.

Markov modelling of land mobile satellite channel for DVB S2X superframing performance evaluation

Markov modelling of land mobile satellite channel for DVB S2X superframing performance evaluation

Performance of Improved-DCSK system over land mobile satellite channel under effect of time-reversed chaotic sequences

Among non-coherent chaos-based communication schemes, improved-differential chaos-shift keying (I-DCSK) with the use of time-reversed chaotic sequences shows good achievement in bit-error-rate (BER) performance and spectral efficiency. To date, BER performance of the I-DCSK system has been investigated over various transmission channels in the presence of Gaussian noise and Rayleigh fading. In this paper, we studied for the first time the performance of the I-DCSK system over a land mobile satellite channel. Discrete-time models of the transmitter and receiver over a two-state Lutz channel typically describing satellite environments are studied. We point out that there are differences in cross-correlation characteristics between the time-reversed and conventional chaotic sequences. From this aspect, BER performance of the studied system is analyzed in scenario of taking into account the cross-correlation effect of time-reversed chaotic sequences. BER expressions are verified by Monte Carlo simulations. Performance comparison between I-DCSK and DCSK-based schemes over the studied channel is carried out. Obtained results prove that the I-DCSK system is able to be used as a physical-layer modulation method using chaos for land mobile satellite applications.

On the Queuing Delay of Time-Varying Channels in Low Earth Orbit Satellite Constellations

Low Earth Orbit (LEO) satellite constellations are envisioned as a complementary or integrated part of 5G and future 6G networks for broadband or massive access, given their capabilities of full Earth coverage in inaccessible or very isolated environments. Although the queuing and end-to-end delays of such networks have been analyzed for channels with fixed statistics, currently there is a lack in understanding the effects of more realistic time-varying channels for traffic aggregation across such networks. Therefore, in this work we propose a queuing model for LEO constellation-based networks that captures the inherent variability of realistic satellite channels, where ground-to-satellite/satellite-to-ground links may present extremely poor connection periods due to the Land Mobile Satellite (LMS) channel. We verify the validity of our model with an extensive event-driven simulator framework analysis capturing the characteristics of the considered scenario. We later study the queuing and end-to-end delay distributions under such channels with various link, traffic, packet and background conditions, while observing good match between theory and simulation. Our results show that ground-to-satellite/satellite-to-ground links and background traffic have a much stronger impact over the end-to-end delay in mean and particularly variance, even with moderate queues, than unobstructed inter-satellite connections in outer space on an established path between two ground stations and through the constellation. This might hinder the usability of these networks for services with stringent time requirements.

Concatenated Coding for GNSS Signals in Urban Environments

This work investigated concatenated coding schemes for Global Navigation Satellite System (GNSS) signals in order to increase their error correction capability in urban environments. In particular, a serial concatenated code that combines an outer Reed–Solomon (RS) code with an inner low-density parity-check (LDPC) code was designed, and the performance was investigated over the land mobile satellite (LMS) channel for characterizing multipath and shadow fading in urban environments. The performance of the proposed concatenated coding scheme was compared to that of a B-CNAV1 message, in which two interleaved 64-ary LDPC codes were employed. The simulation results demonstrate that the proposed concatenated code can obtain a similar error correction performance to the two interleaved 64-ary LDPC codes in both the additive white Gaussian noise (AWGN) and LMS channels at a lower complexity level.

A Novel Multipath Mitigation Technique for GNSS Signals in Urban Scenarios

In typical urban or suburban environments, multipath poses a serious threat to the accuracy of position determined by a global navigation satellite system (GNSS) receiver. In this paper, a novel multipath mitigation technique is proposed for general multipath scenarios encountered in the urban settings. In the proposed technique, a double differentiated correlation function based histogram output is used to estimate the code delay. It is shown that the proposed technique provides significant improvements over the current state of the art techniques like high resolution correlator/double delta correlator and narrow correlator. The results hold for general multipath models for the mobile-satellite channels. The performance guarantees include closed form expressions for the probability of correct delay estimate and simulation results for the average range error variation with respect to carrier to noise ratio (CNR), signal bandwidth and different channel settings.

Performance analysis for DCSK system over land mobile satellite channel

Performance analysis for DCSK system over land mobile satellite channel

Performance analysis for DCSK system over land mobile satellite channel

In chaos-based digital communications, differential chaos-shift keying (DCSK) system has been widely studied thanks to its non-coherent demodulation without chaotic sequence synchronisation. In respect of the performance evaluation, bit error rate (BER) of the DCSK system was investigated over various transmission environments such as noise, fading, and multi-path-affected channels which are radio-propagation models from simple to complex. In this paper, the idea of applying DCSK for operation in land mobile satellite environments is proposed. A land mobile satellite channel, i.e., Lutz model with two states, is used to evaluate the system performance. Discrete-time models of transmitter and receiver over the studied channel are described. BER analysis is performed by means of Gaussian approximation and discrete integration. The analysed expressions are verified by Monte Carlo simulation. Performance comparison between different DCSK-based schemes over the studied channel is carried out. Obtained results point out that DCSK system can be used as a physical-layer modulation method using chaos for land mobile satellite applications.

Performance Analysis and FPGA Prototype of Variable Rate GO-OFDMA Baseband Transmission Scheme

To fulfill the increasing demand for high speed Variable Bit Rate (VBR) broadcast services with reliable Quality of Service, Group Orthogonal-Orthogonal Frequency Division Multiple Access (GO-OFDMA) and Variable Spreading Length Multicarrier Code Division Multiple Access transmission schemes are examined over Land Mobile Satellite (LMS) channel. This paper presents the performance analysis of aforementioned multiple access transmission schemes in terms of computation complexity, Peak-to-Average-Power-Ratio (PAPR) and the average Bit Error Rate (BER) performance over L-band LMS channel. Minimum Mean Square Equalizer (MMSE) equalizer is employed at the receiver. Based on the simulation results, GO-OFDMA stems out to be a better variable rate transmission scheme in respect of both PAPR and BER performance for higher data rate users. Further, GO-OFDMA based VBR transmitter and MMSE equalizer are prototyped on commercially available virtex5 xc5vlx110t–1ff1136 Field Programmable Gate Array (FPGA) device. A block-by-block analysis of hardware resource utilization and power dissipation for the VBR GO-OFDMA transmitter is provided. The achieved baud rate for VBR GO-OFDMA transmission scheme on FPGA is 103.874 Msps. Thus, GO-OFDMA transmission scheme could be appropriate for VBR communication over LMS channel.

Analysis of Variable Bit Rate SOFDM Transmission Scheme Over Multi-Relay Hybrid Satellite-Terrestrial System in the Presence of CFO and Phase Noise

In this paper, the exact closed-form signal-to-interference-noise ratio (SINR) expression, for the joint impact of carrier frequency offset (CFO) and phase noise (PHN), is derived for each channel link in a multi-relay hybrid satellite-terrestrial broadcast system, employing the Walsh Hadamard (WH) based spread-orthogonal frequency multiplexing (S-OFDM) and OFDM transmission scheme at satellite terminal and terrestrial repeaters (relays) respectively. Additionally, bit error rate and spectral efficiency are analyzed for such hybrid system with $M$ -relay, based on the obtained SINR expressions. To examine that, an adaptive decode and forward (ADF) strategy is employed at relay terminals. Also, three-state Fontan Land Mobile Satellite and six-path typical urban terrestrial channel models are considered. This analysis is performed to support variable bit rate (VBR) quality of service at the physical layer of Digital Video Broadcast Satellite Handheld (DVB-SH)-A architecture, the provision of which is absent in the DVB-SH standard. VBRs are assumed for S-OFDM. The results illustrate that both single-relay and three-relay ADF-based VBR WH-SOFDM yield an identical performance in the presence of the combined effect of CFO and PHN, under both performance measures. However, the improvement in performance for the three-relay strategy is observed in the presence of CFO only. Further, a pilot-based channel estimation technique is performed at the receiver, and the estimated error variance is evaluated for every channel link. Later, the block-by-block system computational complexity of single-relay and $M$ -relay ADF-based VBR WH-SOFDM is evaluated. It is shown that the complexity of the $M$ -relay ADF strategy is rate dependent and almost $M-1$ times the single-relay strategy. Hence, an increase in the number of relays would not yield any significant performance gain, but would enhance the system computational complexity considerably. Therefore, for high data rate transmission, the single-relay ADF-based WH-SOFDM scheme could be a suitable candidate for hybrid satellite-terrestrial communication systems in future.

Performance Evaluation of High-Frequency Mobile Satellite Communications

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).

Decoding Performance Analysis of GNSS Messages with Land Mobile Satellite Channel in Urban Environment

Demand for Global Navigation Satellite System (GNSS) applications in the urban environment has experienced a remarkable growth in recent years. However, the received signals are subjected to various urban channel impairments, like shadowing and multipath fading. Therefore, the decoding performance is different from that in open-sky conditions. In this paper, a two-state Land Mobile Satellite (LMS) channel based on the Markov process is used to model the urban channel properties, and then, the analysis of decoding performance in terms of frame error rate (FER) in the LMS channel is performed by evaluating the effect of three major influencing factors, specifically, coding and interleaving in the GNSS message, terminal speed, and satellite elevation angle. Extensive simulations are conducted on BDS-3 B1C B-CNAV1 message and GALILEO E5a F/NAV message. The results validate the excellent error correcting performance of the nonbinary low density parity check (NB-LDPC) code of the B-CNAV1 message and the effectiveness of interleaving in both of the messages in urban condition. Furthermore, it also shows that decoding performance improvement can be achieved with higher terminal speed and higher elevation angle in urban scenarios.

Multiple Scattering Modeling for Dual-Polarized MIMO Land Mobile Satellite Channels

This communication investigates the validity of application of a multiple-scattering model to a dual-polarized multiple-input-multiple-output land mobile satellite (LMS) channel based on a measurement campaign. Two LMS link scenarios in an urban pedestrian environment are examined. In the first one, the transmitter was located at the top of a tall building and in the second one, on an airship. The third-order scattering model is utilized to statistically characterize the measured channels, and the results reveal that the model provides an excellent fit to the LMS composite fading amplitude in the line-of-sight (LOS) and non-LOS scenarios. For this generic radio channel, asymptotic expressions for the theoretical probability density function and the cumulative distribution function are derived. The comparison of the third-order scattering model with existing LMS ones showed that it provides better overall accuracy together with a physical interpretation of the propagation mechanisms involved.

Link-Layer Coding for GNSS Navigation Messages

In this paper, we face the problem of ensuring reliability of Global Navigation Satellite Systems (GNSSs) in harsh channel conditions, where obstacles and scatter cause long outage events that cannot be counteracted with channel coding only. Our novel approach, stemming from information-theoretic considerations, is based on link-layer coding (LLC). LLC allows us to significantly improve the efficiency in terms of time-to-first-fix with respect to current operational GNSSs, which adopt carousel transmission. First, we investigate the maximum theoretical LLC gain under different Land Mobile Satellite channel conditions. Then, some practical LLC coding schemes, namely, fountain codes and a novel low-density parity-check plus low-rate repetition coding, are proposed and tested in realistic single-satellite and multi-satellite Land Mobile Satellite scenarios, considering the Galileo I/NAV message as study case. Simulation results show that our designed schemes largely improve on carousel transmission and achieve near-optimal performance with limited increase in complexity. Also, back-compatibility of LLC is assessed with respect to present-time GNSS specifications.

RLNC in satellite networks: A cooperative scenario for delivering M2M traffic

SummaryThe fraction of machine‐to‐machine traffic carried by satellite networks is increasing, and an efficient delivery is required in order to enable a large set of applications that can benefit from the advantages provided by the use of satellites. This work analyses the use of random linear network coding techniques in land mobile satellite channels to reliably deliver machine‐to‐machine traffic to mobile nodes in urban areas. The considered scenario takes into account a cooperative coverage extension in land mobile satellite vehicular networks, where the use of random linear network coding techniques can remove the need for any fixed equipment on the ground at least in urban environments, where the density of mobile nodes is typically high.

Modelling of Land Mobile Satellite Channel to Counter Channel Outage

Modelling of Land Mobile Satellite Channel to Counter Channel Outage

Capacity of the broadband dual-orthogonal polarized MIMO Land Mobile Satellite (LMS) channel: Channel modeling and influenced factors analysis

Generally, the channel capacity of a MIMO system is closely related to its Channel Characteristic Matrix (CCM). In most current studies, the CCMs are formed by an independent identical distribution (i.i.d) model with Rayleigh or Rice distribution and nevertheless incomplete and inaccurate to describe a Broadband Dual-orthogonal Polarized MIMO Land Mobile Satellite (BDM-LMS) channel. In this paper, we build up the BDM-LMS channel model combining a 4-states broadband LMS channel model, time selective fading features, Channel Covariance Information (CCI) model and polarization correlation between antennas. Modeling steps of the channel model are introduced. The main emphasis is placed on the effects of the factors on the channel capacity in BDM-LMS system, such as antenna numbers, temporal correlations, terminal environments, elevation angles and polarization correlations between the DPAs. We provide simulation results to illustrate the effects of these factors through comparisons of the transmit rate, Ergodic Capacity and Outage Capacity. Moreover, the MIMO outage capacity advantages, indicating the benefits of MIMO compared with SISO systems under the same channel condition, are also studied under i.i.d and BDM-LMS channel.

Channel Measurements, Characterization, and Modeling for Land Mobile Satellite Terminals in Tropical Regions at Ku-band

Severe tropical weather dynamics impairments on the earth-sky signal quality at the Ku-band relative to temperate weather increase the demand for land mobile satellite (LMS) channel characterization and modeling specific to tropical regions. Variation in weather dynamics decreases the accuracy of the existing LMS channel models if applied to the tropics. This paper presents a tropical weather-aware LMS channel model that can be applied at areas with diverse atmospheric (rain, clouds, and tropospheric scintillation) and mobility impairments. The proposed tropical-LMS channel (TRO-LMSC) model is designed based on actual experimental measurements conducted in a tropical area. The TRO-LMSC model involves multipath design, mobility model, rain impairment model, cloud impairment model, tropospheric scintillation model, and link budget module (LBM). The proposed model shows improved channel modeling accuracy and comprehensiveness with relatively less root mean square error (rmse), compared with existing models. Consequently, this improvement enhances the identification of the type and performance of the fade mitigation technique, the management of available communication resources, and the reliability and efficiency of the communication services.