Leveraging multiuser diversity for adaptive hybrid satellite‐LTE downlink scheduler (H‐MUDoS) in emerging 5G‐satellite network

In order to achieve ubiquitous coverage and service continuity in future 5G network, satellite‐based access is the best solution to complement the terrestrial LTE‐A. In light of this, we introduce a channel‐aware hybrid scheduling technique on the basis of satellite‐LTE spectrum sharing. According to the user‐experienced channel, base stations (eNodeB) and the satellite will work cooperatively. The eNodeB mainly provides service in urban area for high density population. Meanwhile, the satellite will perform either offloading, providing service for under‐served users, or extra coverage for users in rural and remote areas having no coverage of eNodeB. Leveraging the multiuser diversity, we implement a new metrics computation method for hybrid satellite‐LTE downlink scheduler (H‐MUDoS). Compared with other existing schedulers, simulation results clearly demonstrate the high performance of H‐MUDoS in terms of spectral efficiency in addition to improvement of the quality‐of‐service requirements and capacity maximization.     

Experimental proof of concept of an SDN‐based traffic engineering solution for hybrid satellite‐terrestrial mobile backhauling

Satellite networks are expected to be an integral part of 5G service deployment. One compelling use case is mobile backhauling, where the exploitation of a satellite component can improve the reach, robustness, and economics of 5G rollout. The envisaged availability of new satellite capacity, together with the development of better integration approaches for the provisioning and operation of the satellite component in a more flexible, agile, and cost‐effective manner than done today, are expected to revamp such use case within the 5G ecosystem. In this context, sustained in the architectural designs proposed within H2020 VITAL research project, this paper presents an experimental proof of concept (PoC) of a satellite‐terrestrial integration solution that builds upon software‐defined networking (SDN) technologies for the realization of end‐to‐end traffic engineering (E2E TE) in mobile backhauling networks with a satellite component. A laboratory test bed has been developed and validated, consisting of a small‐scale private mobile network with a backhaul setting that combines Ethernet‐wired links, a satellite link emulator (OpenSAND), OpenFlow switches, and an OpenFlow controller running the network application for E2E TE. Provided results show the operation of a E2E TE application able to enforce different traffic routing and path failure restoration policies as well as the performance impact that it has on the mobile network connectivity services.     

Symbol error rate calculation and data pre‐distortion for 16‐QAM transmission over nonlinear memoryless satellite channels

This paper presents a simplified mathematical approach to evaluate the performance of any given circular constellation of 16‐level quadrature amplitude modulation (16‐QAM) in terms of symbol error rate (SER). Following this approach, with the aim to work with memoryless nonlinear satellite channels, a model is derived as a generalized form for both linear and nonlinear channels in the presence of down link additive white Gaussian noise (AWGN). The analysis provides means to calculate the optimal ring ratio (RR) and phase difference (PD) for several possible candidates of 16‐QAM circular constellations. The effects of RR and PD on the SER performance are investigated in the analysis. To overcome the nonlinear distortion, data pre‐distortion is taken into account in the study. The paper gives a general procedure for data pre‐distortion implementation for all circular 16‐QAM constellations. The analytical formulation has been extended for total degradation (TD) performance measure as a function of input back‐off (IBO) of the nonlinear amplifier. A SER performance‐comparison between different constellations for 16‐QAM systems has also been presented in this paper. The analytical results are validated by simulation. Copyright © 2006 John Wiley & Sons, Ltd.     

Digital video broadcasting over satellite (DVB‐S): a system for broadcasting and contribution applications

The general system concepts for digital television transmission and broadcasting by satellite, developed within the European digital video broadcasting (DVB) Project and standardized by ETSI are described. The system (EN 300 421) is designed to provide direct‐to‐home (DTH) multi‐programme TV services in the BSS and FSS bands and is addressed to consumer integrated receiver decoders (IRDs), as well as collective antenna systems (SMATV) and cable television head‐end stations, with a likelihood of remodulation. The system operational modes have been extended in 1998 (EN 301 210) to cover also ‘contribution’ applications by satellite, such as conveying vision and sound material between TV studios, or from remote locations directly to the broadcaster's premises through light and portable up‐link terminal digital satellite news gathering (DSNG). The exploitation of the multiplex flexibility allows the use of the transmission capacity for a variety of TV service configurations. The use of flexible and advanced error protection techniques, based on the concatenation of Reed‐Solomon and convolutional codes (with Viterbi decoding), allows optimum adaptation to different satellite transponder characteristics, i.e. bandwidth and power, providing high service quality and availability with small receiving antennas (DTH applications) or transmitting terminals (DSNG applications). Copyright © 2000 John Wiley & Sons, Ltd.     

Co‐channel interference cancelation at the user terminal in multibeam satellite systems

We study the applicability of soft interference cancelation in the forward link of multibeam satellite systems with focus on mobile terminals. We adopt a standard currently used in commercial satellite systems as a reference. The multibeam satellite antenna radiation diagram has been generated using a physical optics reflector model while a widely adopted channel model has been used for the land mobile satellite channel. The interference pattern has been derived using a system simulator developed by the European Space Agency. Starting from the analysis of the interference pattern, we study the application of a low‐complexity soft interference cancelation scheme for commercial applications. Our results show that, under realistic conditions, a two‐colors frequency reuse scheme can be employed while guaranteeing service availability across the coverage and keeping the complexity at the user terminals relatively low. Copyright © 2015 John Wiley & Sons, Ltd.     

Tri‐orthogonal polarization diversity reception for non‐geosynchronous satellite orbit ionospheric channels

Electromagnetic signals propagating through the ionosphere are subject to path delay and the depolarizing effect of Faraday rotation. These are both dependent on global position and link geometry, which constantly vary for satellites in non‐geosynchronous orbits. These effects introduce performance error and reduce range resolution of remote sensing polarimetric measurements. Communication with ground receivers may be severely degraded by these effects. In this paper, a tri‐orthogonal approach at the receiver is introduced to enhance performance of conventional polarization diverse receive schemes. Performance is measured through a capacity metric. The work presented forms part of a large‐field‐of‐view, non‐geosynchronous satellite model exploiting tri‐orthogonal receive polarimetry as a means to enhancing link performance in a field‐of‐view. Copyright © 2016 John Wiley & Sons, Ltd.     

LTE‐based satellite communications in LEO mega‐constellations

The integration of satellite and terrestrial networks is a promising solution for extending broadband coverage to areas not connected to a terrestrial infrastructure, as also demonstrated by recent commercial and standardisation endeavours. However, the large delays and Doppler shifts over the satellite channel pose severe technical challenges to traditional terrestrial systems, as long‐term evolution (LTE) or 5G. In this paper, 2 architectures are proposed for a low Earth orbit mega‐constellation realising a satellite‐enabled LTE system, in which the on‐ground LTE entity is either an eNB (Sat‐eNB) or a relay node (Sat‐RN). The impact of satellite channel impairments as large delays and Doppler shifts on LTE PHY/MAC procedures is discussed and assessed. The proposed analysis shows that, while carrier spacings, random access and RN attach procedures do not pose specific issues and hybrid automatic repeat request requires substantial modifications. Moreover, advanced handover procedures will be also required due to the satellites' movement.     

Filter bank‐based multiple access in next‐generation satellite uplinks: A DVB‐RCS2‐based experimental study

In the context of the on‐going evolution of satellite communications (SatCom) systems to their next generation, and in the direction of their integration with fifth generation (5G) terrestrial networks, it is of interest to study in depth the applicability in realistic SatCom of waveforms that have shown promise to meet the 5G requirements. This paper presents a comparative study, based on total degradation (TD) over a range of output back‐off (OBO) values, on out‐of‐band emission and spectral efficiency, of frequency division multiple access (FDMA) schemes employing offset quadrature amplitude modulation‐based filter bank multi‐carrier (FBMC /OQAM), classical orthogonal FDMA (OFDMA), and their single‐carrier counterparts to illustrate the potential gains from the integration of the FBMC waveforms in the satellite context and standards. The air interface simulated follows the digital video broadcasting (DVB) family of standards for the satellite uplink, considering both time and frequency synchronization impairments and two typical input constellations. Our results confirm the superiority of the single‐carrier (SC) schemes in such a nonlinear environment. The SC‐FBMC waveform is shown to be the most practical candidate since it is shown to attain a TD performance similar to that of SC‐OFDM at absolutely no cost in spectral efficiency.     

Implementing polarization shift keying over satellite – system design and measurement results

Polarization shift keying (PolSK) is a digital modulation technique using the state of polarization of an electromagnetic wave as the signalling quantity. PolSK comes from fibre communications, where the channel offers two orthogonal states of polarization. This article develops on the idea to adapt this technology to satellite communications, where similar channel conditions exist. For this purpose, a digital PolSK modem was implemented on a programmable logic board. A proposal for constellation design as well as thoughts on synchronization of PolSK over satellite is presented. The modem was used to demonstrate a 16‐state Polarization Shift Keying link over a commercial satellite in K_u band. Measurements have been conducted in a back‐to‐back setup on intermediate frequency and on a K_u band transponder simulator to assess the impact of path‐length differences, carrier recovery and non‐linearity. Copyright © 2015 John Wiley & Sons, Ltd.     

On the secrecy performance of integrated satellite‐aerial‐terrestrial networks

This paper investigates secure transmission of an integrated satellite‐aerial‐terrestrial network (ISATN), where multiple eavesdroppers (Eves) attempt to overhear the satellite signals cooperatively. The ISATN adopts an unmanned aerial vehicle (UAV) equipped with multiple antennas as a relay with threshold‐based decode‐and‐forward (DF) protocol. By assuming that perfect instantaneous channel state information (CSI) of the satellite‐UAV link and the statistical CSI of the UAV‐user link are available, we first propose a beamforming (BF) scheme for maximizing the achievable secrecy rate (ASR) of the considered network. Then, we derive the analytical expressions of the secrecy outage probability (SOP) and ergodic secrecy rate (ESR) of the considered system with the BF strategy under an assumption that the satellite‐UAV link undergoes the shadowed‐Rician fading, while the UAV‐user link experiences the correlated Rayleigh fading. Finally, numerical results are given to demonstrate the superiority of the proposed BF scheme against zero forcing (ZF) and maximal ratio transmission (MRT) schemes and the validity of the secrecy performance analysis.     

On the performance of UNB for machine‐to‐machine low earth orbit (LEO) satellite communications

Ultra narrow band (UNB) is a widely used technology for machine‐to‐machine and low‐power wide‐area communications. Its properties, long range with small RF power, make it naturally attractive for satellite communications but also draw new challenges compared with terrestrial systems where this technology is already deployed. Indeed, the main advantage of UNB signals, their small bandwidth, makes them more sensitive to frequency drifts that are particularly present in the case of LEO satellite systems. It also implies the use of a random access method in which the carrier frequency is a parameter unknown by the receiver. In this paper, we propose a general semianalytical model to evaluate the performance of a terrestrial or satellite system using UNB technology, taking into account the multiuser interference and the frequency drift. This model is then used to assess the performance (packet loss ratio and throughput) on the return link medium access control (MAC) of a representative LEO satellite system. With our model, we analyze the effect of frequency drift on the system performance. This paper also proposes to investigate more deeply the multiuser interference modeling in order to estimate accurately the performances of a UNB system in terms of bit error rate (BER). We propose a semianalytical approach to study the interference in presence of arbitrary power imbalance that includes the effect of frequency offset and frequency drift and applicable for any linear modulation and any pulse‐shaping filter. The expression of the multiuser interference is established in the general case. We then propose a methodology to compare this exact model to the Gaussian interference approximation (mainly used through the central limit theorem) in order to assess its accuracy.     

Adaptive frequency‐hopping schemes for CR‐based multi‐link satellite networks

In this paper, we study two dynamic frequency hopping (DFH)–based interference mitigation approaches for satellite communications. These techniques exploit the sensing capabilities of a cognitive radio to predict future interference on the upcoming frequency hops. We consider a topology where multiple low Earth orbit satellites transmit packets to a common geostationary equatorial orbit satellite. The FH sequence of each low Earth orbit–geostationary equatorial orbit link is adjusted according to the outcome of out‐of‐band proactive sensing scheme, performed by a cognitive radio module in the geostationary equatorial orbit satellite. On the basis of sensing results, new frequency assignments are made for the upcoming slots, taking into account the transmit powers, achievable rates, and overhead of modifying the FH sequences. In addition, we ensure that all satellite links are assigned channels such that their minimum signal‐to‐interference‐plus‐noise ratio requirements are met, if such an assignment is possible. We formulate two multi‐objective optimization problems: DFH‐Power and DFH‐Rate. Discrete‐time Markov chain analysis is used to predict future channel conditions, where the number of states are inferred using k‐means clustering, and the state transition probabilities are computed using maximum likelihood estimation. Finally, simulation results are presented to evaluate the effects of different system parameters on the performance of the proposed designs.     

A Dual‐Mode Narrow‐Band Channel Filter and Group‐Delay Equalizer for a Ka‐Band Satellite Transponder

This paper presents the design of a narrow‐band channel filter and its group‐delay equalizer for a Ka‐band satellite transponder. We used an 8th order channel filter for high selectivity with an elliptic‐integral function response and an inline configuration. We designed a 2‐pole, reflection‐type, group‐delay equalizer to compensate for the steep variation of the group‐delay at the output of the channel filter, keeping the thermal stability at ±7 ns of group‐delay variation at the band edges over 15–55 ·C. We devised a new tuning technique using short‐ended dummy cavities and used it for tuning both the filter and equalizer; this removes the necessity of additional tuning after the cavities are assembled. Through measurement, we demonstrate that the group‐delay‐equalized filter meets the equipment requirements and is appropriate for satellite input multiplexers.     

Performance comparison of end‐to‐end and on‐the‐spot traffic‐aware techniques

Traffic‐aware routing protocols have recently received considerable attention. This has been motivated by the role that it could play in extending the network's lifetime (or operational time) as it target the reservation of node's power and better utilisation of channel bandwidth, which could lead to performance improvement in terms of important performance metrics including throughput and end‐to‐end delay. Traffic‐aware techniques can be classified into two categories, namely end‐to‐end and on‐the‐spot, based on the way of establishing and maintaining routes between any source and destination. Although there has been much work on both categories, there has been no comparative performance study of the two approaches. To the best of our knowledge, this is the first work that carries out such a performance comparison. To this end, we have adapted our traffic‐aware technique namely load density to suggest a new ‘on‐the‐spot’ traffic‐aware technique. The main reason for doing this adaptation is to ensure that the comparison between the two approaches is fair and realistic. The study will reveal the main performance characteristics of the two approaches under various traffic and network conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

A high‐speed long‐haul wavelength division multiplexing–based inter‐satellite optical wireless communication link using spectral‐efficient 2‐D orthogonal modulation scheme

In this work, we propose a novel multi‐bit/symbol spectral‐efficient optical orthogonal modulation scheme based on simultaneously modulating differential quadrature phase shift keying (DQPSK)‐polarization shift keying (PolSK) in a 16‐channel wavelength division multiplexing (WDM)‐based inter‐satellite optical wireless communication (IsOWC) system. Through numerical simulations, we demonstrate a reliable transportation of 16 × 100 Gbps information over 25 000 km of transmission range with acceptable bit error rate (BER) using the proposed system. Further, the impact of space turbulences (ie, pointing error losses) on the BER performance of the proposed IsOWC link has been evaluated using numerical simulations. The simulation results report a successful transportation of information up to 2.7 μrad receiver pointing error angle with acceptable performance.     

Packet scheduling in MIMO satellite long term evolution networks

This paper deals with the performance evaluation of different packet scheduling schemes for Long Term Evolution mobile satellite systems based on the adoption of a multi‐user MIMO technique. The major breakthrough of MIMO technology in terrestrial networks has motivated the interest here for the adoption of MIMO in mobile satellite systems as well. In particular, a land mobile dual‐polarized GEO satellite system has been considered in this work. The aim of this paper is to propose new cross‐layer packet scheduling schemes that achieve a good trade‐off among throughput, QoS and fairness and to conduct performance comparisons with other scheduling schemes in the literature. This is the reason why this paper also proposes a new performance index that can be used to evaluate the overall performance of each scheduler. The work shows that the new cross‐layer scheduler, called channel‐based queue sensitive scheduler, attains the best performance in terms of the new comprehensive performance index, thus representing an interesting solution for future mobile satellite systems. Copyright © 2015 John Wiley & Sons, Ltd.     

Novel down link rain fade mitigation technique for Ka‐band multibeam systems

Rain fades at Ka‐Band degrades the link quality and performance significantly. Several rain fade mitigation techniques for Ka‐band satellite systems are being investigated to improve the channel capacity. Methods such as power control and adaptive waveform techniques have been proposed for use in the uplink as they are capable of straightforward implementation. A novel down link power control technique for multi‐beam Ka‐band system has been proposed in this paper. It is based on the use of multi‐port amplifier, which is commonly used for dynamic power sharing of the beams depending upon the traffic. Payload architecture for multi‐beam coverage using multi‐port amplifiers has been designed for the proposed technique. The simulation results to compensate for the rain fade attenuation of one beam by sharing the unused power from other beams have been presented Copyright © 2006 John Wiley & Sons, Ltd.     

Low complexity multi‐channel synchronization for satellite systems with adjacent channel interference

In satellite communications, the space segment is a large slice of the operating costs. Therefore every effort should be made to increase the spectral efficiency, thereby reducing the space segment costs. In order to optimize spectral efficiency, channel spacing (CS) should be reduced. Unfortunately, this introduces spectrally overlapping transmissions, thereby creating adjacent channel interference (ACI), which impairs the performance of satellite communication systems. To overcome this problem, intelligent interference mitigation schemes should be considered. This paper considers the problem of multi‐channel synchronization of several spectrally overlapping transmissions in a satellite TDMA/frequency division multiple access burst system. The synchronization aims to estimate carrier frequency, carrier phase and symbol timing in the presence of ACI. The potential performance gain of multi‐channel processing over conventional single channel processing is shown. Two types of low‐complexity algorithms are proposed: ‘channelized’ expectation maximization and ‘channelized’ interference cancellation. Both of these algorithms attain this performance gain. Computer simulations show a 78% improvement in spectral efficiency for a wide range of carrier‐imbalance values. This translates into a large potential saving in space segment costs compared to conventional CS. Copyright © 2006 John Wiley & Sons, Ltd.     

Frequency shift filter‐based multi‐carrier transceiver

It is well known that orthogonal frequency division multiplexing (OFDM) is sensitive to carrier frequency offset (CFO) and suffers from a high peak‐to‐average ratio. In addition, the performance of OFDM is severely affected by strong co‐channel interference and strong narrowband interference. To mitigate the limitations of OFDM, we propose a new multi‐carrier transceiver based on frequency‐shift filter. A frequency‐shift filter can separate spectrally overlapping sub‐carrier signals by exploiting the spectral correlation inherent in the cyclostationary modulated signals. To increase spectral efficiency, we increase the percentage of spectral overlap between two adjacent sub‐channels. We derive an upper bound and a lower bound on the bit error rate performance of the proposed multi‐carrier transceiver in additive white Gaussian noise channel and frequency‐nonselective Rayleigh fading channel, respectively. Compared with OFDM, our simulation results show that the proposed multi‐carrier transceiver is much less sensitive to CFO and has a lower peak‐to‐average ratio; moreover, without any additional interference suppression technique, the proposed transceiver has the advantage of being able to mitigate strong co‐channel interference with CFO from the intended multi‐carrier signal and mitigate strong narrowband interference in additive white Gaussian noise channel and in Rayleigh fading channel in which a large CFO between the transmitted signal and the received signal often occurs. Copyright © 2011 John Wiley & Sons, Ltd.