Multibeam satellite systems make it possible to reduce the size of earth stations and hence the cost of the earth segment. Frequency re-use from one beam to another permits an increase in capacity without increasing the bandwidth allocated to the system.
With single beam antenna coverage, it is therefore necessary to choose between either extended
coverage providing service with reduced quality to geographically dispersed earth stations, or
reduced coverage providing service with improved quality to geographically concentrated earth
stations. Multibeam antenna coverage allows these two alternatives to be reconciled. Satellite extended coverage may be achieved by means of the juxtaposition of several narrow beam coverages, each beam providing an antenna gain which increases as the antenna beamwidth decreases (reduced coverage per beam).
High Throughput Satellites (HTS), using spot beam technology, started to emerge in commercial satellite communications over the last decade. These hybrid satellites deliver the unique advantages of both wide-beam coverage and high-powered spot beams that can be customized to serve specific application needs across the region.
High-throughput Satellite or HTS systems represent a new generation of satellite communications systems, that provide a significant increase in capacity than conventional communication satellites. They utilize frequency reuse and multiple spot beams to deliver vast throughput for the same amount of allocated orbital spectrum. The increase in capacity typically ranges from 2 to more than 100 times as much capacity as the conventional fixed, broadcast, and mobile satellite services (FSS, BSS, and MSS). This significantly reduces the cost per bit.
For HTS’ benefits to be fully realized, innovation on the ground is vital, while simultaneously ensuring that costs are kept down. Most communications satellites are in geostationary orbit (GEO) at an altitude of 35,786 km, naturally leading to excessive delay and infeasibility of integration with terrestrial mobile network.
Although Geostationary (GEO) satellites once dominated the outer orbits of the Earth, the increasing deployment of HTS GEO, MEO and LEOs, with alternative operating systems, is demanding that solutions providers adapt to vastly different requirements. Non-geostationary orbit (NGSO) satellite system is proposed to provide low-latency, high-bitrate global Internet connectivity and several satellite constellations are about to begin commercialization. More than a dozen such satellites have been launched in recent years and several more will go into orbit in the coming years.
Despite the higher costs associated with spot beam technology, the overall cost per circuit is considerably lower as compared to shaped beam technology. While Ku band FSS bandwidth can cost well over $100 million per gigabit per second in space, HTS like ViaSat-1 can supply a gigabit of throughput in space for less than $3 million.
Very High Throughput Satellites (V/HTS)
In contrast to mono-beam satellites, high throughput satellites split the service area into multi-spot beam service areas, which allows higher aggregate throughput and more service flexibility to satisfy a heterogeneous demand. The system architecture is shown in Fig. and comprises a Gateway (GW), a satellite, and multiple UTs.
The gateway (GW) is connected to the core network and serves a set of users that are geographically far away using the satellite as relaying node. The link from the GW to the satellite, and from the satellite to the UT are known as the feeder link and the user link, respectively. In the usual star configuration that is observed in Fig. , the feeder link presents high directivity and gain. Also, depending on the direction of the communication, the link receives the name forward link when it goes from the GW to the UT and reverse link when it goes from the UT to the GW.
The one fundamental difference in the architecture of an HTS system is the use of multiple ‘spot beams’ to cover a desired service area, rather than wide beams, which bring a two-fold benefit:
- Higher transmit/receive gain: because of its higher directivity and therefore higher gain, a narrower beam results in increased power (both transmitted and received), and therefore enables the use of smaller user terminals and permits the use of higher order modulations, thus achieving a higher rate of data transmission per unit of orbital spectrum. A better link budget allows the use of higher order modulation and coding schemes, resulting in a higher spectral efficiency, increased throughput and thus more cost-effective Mbit/s.
- Frequency reuse: when a desired service area is covered by multiple spot beams, several beams can reuse the same frequency band and polarization, boosting capacity of the satellite system for a given amount of frequency band allocated to the system. In the case of a multibeam satellite, the isolation resulting from antenna directivity can be exploited to re-use the same frequency band in separate beam coverages. The higher the spectral efficiency, the higher the rate of data transmission per unit of orbital spectrum utilized. This is a very important feature because of the congestion of orbital slots as well as the limitations in the spectrum available.
The link performance improves as the number of beams increases; the limit is determined by the antenna technology, whose complexity increases with the number of beams, and the mass.
In the last 10 years, the majority of high-throughput satellites operated in the Ka band, however this is not a defining criterion, and at the beginning of 2017, there was at least 10 Ku band HTS satellites projects, of which 3 were already launched and 7 were in construction.
The frequency selection is driven by many considerations, among them coverage and beam size, atmospheric conditions in the served region, and availability of a robust ecosystem of ground equipment technologies. For instance, current-generation GEO HTSs typically use the Ka-band, which is less congested than the C/Ku-band.
For fixed satellite services (FSS), this refers to the exclusive satellite band from 19.7 to 21.2 GHz for the forward link and from 29.5 to 31 GHz for the reverse link. In land mobile satellite services (MSS) generally use lower frequencies such as the L-band (i.e., from 1.5 to 2.5 GHz) because of its lower attenuation, which enables a less complex UT. Ka-band is more sensitive to severe atmospheric perturbations. However, these only occur during very limited time periods, and can be mitigated using Fade Mitigation Techniques (FMT)
As the connectivity industry continues to respond to the rapid development of new technologies, this latest generation of space innovation is poised to meet consumer demands in an age of big data, 5G and the Internet of Things (IoT), as well as growing hunger for bandwidth in key markets such as broadcast, cellular, and mobility. This is coupled with the proliferation of Low Earth Orbit (LEO) satellites in outer space, providing high bandwidth and low latency and offering low cost globally.
Benefiting from the increased capacity capabilities HTS bring are bandwidth-intensive services which represent a driving force in the broadband market. High throughput satellite (HTS) systems are capable of broadband Internet access service comparable to terrestrial services in terms of pricing and bandwidth.
As user demand for HD and 4K streaming services via streaming and video services rises, the market is destined to grow. These Over-The-Top (OTT) services are often consumed on smartphones and other connected devices, and the expectation of anytime, anywhere connectivity is now considered the norm.
They can provide High throughput connectivity and a range of services in a similar fashion to traditional legacy satellites. The primary user requirement of HTS is Broadband Internet access service (point-to-point) to regions unserved or underserved by terrestrial technologies. For example corporate and consumers in areas where high-quality broadband through the terrestrial infrastructure is not available. In regions where high-quality broadband through our ground infrastructure is not available or maybe not possible, satellite technology is the most appropriate solution.
They can be used for Cellular backhaul: providing high capacity links to support otherwise isolated base stations of terrestrial mobile networks. They can provide high datarate connectivity to customer platforms located at sea, and not connected by seabed submarine cables for Example: Production oil fields in the North Sea.
High Throughput Satellites (HTS), with multiple spot beam satellite designs also offer advantages to military including increased data rates, enhanced security and interference mitigation. Signals in spot beams are more difficult to jam and interference can be worked around more easily, said Intelsat General Corp. President Skot Butler. Whether it’s intentional jamming or accidental interference, the satellite’s digital payload can disconnect the uplink from the downlink and assign new frequencies and a new link to the UAV to reestablish the connection.
VHTS (Very High Throughput Satellite) systems for 5G
Significant satellite advantages can support critical usage scenarios for 5G. One such benefit is that satellites can support multi-Gbps data rates for enhanced mobile broadband (eMBB) communications. Satellites already support 2G/3G mobile backhaul in many parts of the world.
The VHTS overcomes the capacity of traditional systems that provide Fixed and Mobile Satellite Services (FSS and MSS, respectively), using contoured regional footprints. The VHTS objective is to achieve 1 Terabit/s per satellite in the near future. It is based on multibeam coverage (with polarization schemes and frequency reuse) and using higher bandwidths in the feeder link, such as Q/V frequency bands.
VHTS (Very High Throughput Satellite) systems utilizing spot beams in order to provide broadband services to end-users with bit rates in excess of Terabit/s. They are ideally suited to support 5G as they provide more flexibility than HTS and are capable of being able to better match traffic distributions, accommodate more demand per beam and support dynamic service delivery. Very High throughput satellites (V/HTS), with their multiple spot-beams, are key for delivering the future rate demands.
In addition, satellites can support massive machine-type communications (mMTC), i.e., satellites already support SCADA and other global asset tracking applications today and can scale to support future M2M and IoT communications
Two 5 GHz frequency bands are available in E-Band (i.e., 71 to 76 and 81 to 86 GHz) for commercial very high throughput satellite (VHTS) communication systems. While E-Band is attractive because of the available bandwidth and light licensing, it poses significant complexities for the uplink and downlink.
However, adopting these high frequencies makes RF component and subsystem development challenging for the satellite communications (satcom) system as well as the test and measurement (T&M) equipment and setups for working in E-Band.
- Component and subsystem technology performance and commercial availability
- Propagation losses: rain and free-space loss
- Antenna design for the ground gateway and spacecraft
- T&M equipment and measurements.
At these frequencies, propagation and atmospheric attenuation require higher power and lower noise figure components for the communication links. The mmWave components and subsystems developed for the ground gateway and spacecraft are significantly more complicated at E-Band because RF components suitable for satcom links need to be developed and qualified for the space portion of the system. Signal generation, adequate linear RF power in the band, fade mitigation techniques, the physical sizes of the RF components and regulatory challenges are a few of the elements to be examined.
InP low noise amplifier (LNA) technology or some exotic heterojunction high bandgap materials with super low noise figure will be required in both the spacecraft and gateways for E-Band systems. Hughes’ estimates a 2 to 3 dB noise figure is needed in the gateway, possibly relaxed to 4 dB in the spacecraft.
Based on the component and antenna requirements, the technologies being proposed for the PAs and LNAs at both ends will be tube-based, possibly some solid-state PAs. High-power, linear tubes will be considered, and GaN may play a role in the PA, depending on timing. Hughes is currently conducting detailed tradeoffs to determine the best technologies and the manufacturers able to support space-qualified E-Band Tbps systems. This same assessment process applies to the gateway and spacecraft antennas. Composite materials with very low surface roughness are feasible for the antennas as long as the tolerances are precise.
Further, a satellite payload using multibeam coverage must be in a position to interconnect all network earth stations and consequently must provide interconnection of coverage areas. The complexity of the payload is added to that of the multi-beam satellite antenna subsystem which is already much more complex than that of a single beam satellite.
The multibeam satellite is however susceptible to Interference between beams both co-channel interference (CCI) because of side lobes and adjacent channel interference (ACI) because of imperfect filtering. The effect of self-interference appears as an increase in thermal noise under the same conditions as interference noise.
Further increasing the frequency reuse leads to a further increase of intra-system interference among the co-channel beams, which shifts the classical noise-limited link budget analysis towards an interference-dominated situation. The sidelobes of the beam radiation patterns create interference leakage among beams, and the carrier-to interference ratio (CIR) can be severely degraded. As modern satellite systems tend to re-use frequency as much as possible to increase capacity, self-interference noise in a multibeam satellite link may contribute up to 50% of the total noise.
For these reasons, advanced Signal Processing is required in order to reduce the interference among so many multiple beams, facilitate adaptive coverage, dynamically optimize the traffic, and share the spectrum with terrestrial services, among other functions. Flexibility in the resource allocation per beam can significantly improve the quality of service and bring down the incurred cost of the V/HTS system per transmitted bit.
The final V/HTS system performance depends not only on the capabilities of the applied signal processing, but also on many system choices. Complex design trade-offs and practical aspects need to be respected. For example, if hundreds of beams are available in the system, high frequency reuse schemes can stress the payload resources of the satellite in terms of mass, power, and thermal dissipation.
Another important consequence of increasing the frequency reuse is that the frequency bandwidth of the feeder link should increase accordingly. As this is not straightforward to do, different alternatives should be studied, such as employing multiple gateways in the feeder link .
Finally, it is important to note that V/HTS systems require the most advanced transmission standards. Currently, DVB S2/S2X are the standards of both forward broadcast and broadband satellite networks. Using high efficiency modulation and coding schemes (MODCODs) up-to 256APSK combined with advanced interference management techniques enable aggressive and flexible frequency reuse. DVB-S2X incorporates the novel super-framing structure that enables the use of SP techniques such as precoding and multi-user detection at the user terminal. Among other things, it incorporates orthogonal Walsh-Hadamard (WH) sequences as reference/training sequences, allowing simultaneous estimation of the channel state information of multiple beams.
The forward link of High Throughput Satellites normally uses variable coding of modulation (VCM) and adaptive coding of modulation (ACM) which has the capability of multispot coverage and can handle atmospheric conditions and different geographical locations. The DVB-52 standard is a good example of the ACM and VCM. It provides the system to improve the modulation and coding in both static and dynamic conditions. Lower coding rates and higher order modulations are utilized at the peak performance of the beam while at the edges of the beam higher coding rates and lower order modulation are used. Mod cod (Modulation and coding) is used to sustain the optimum link under a dynamic condition or rain fade. Under critical situations, the finest data rates are offered according to the link properties at a definite terrestrial area.
The HTSs that are currently operative are ViaSat-1 , SES-12, EchoStar XVII (also known as Jupiter-1) provide more than 100 Gbit/s of capacity, which is more than 100 times the capacity offered by a conventional FSS satellite. When it was launched in October 2011 ViaSat-1 had more capacity (140 Gbit/s) than all other commercial communications satellites over North America combined.
These HTS systems use the Ku/Ka-band in both feeder and user link, and serve in the user link as much as 200 beams in the same frequency band.
VHTS systems (e.g., Viasat-3) aim at achieving data rates in the range of Tbps and, due to that, they need higher frequencies in the Q-band (30 to 50 GHz), V-band (50 to 75 GHz), and W-band (75 to 110 GHz), in order to serve as much as 3000 beams in the user link.
American company SpaceX plans to launch Starlink, a constellation of 4,425 low Earth orbit LEO) satellites and 7518 VLEO satellites in approximately 340 km orbits. The plan was authorized by the Federal Communications Commission (FCC) and will be fully deployed in 2027.
On February 27, 2019, OneWeb successfully launched its first six satellite into orbits. The constellation consists of 720 LEO satellite and has got authorization from UK and FCC.
China Aerospace Science and Technology Corporation (CASC) will launch nine LEO satellites as a pilot demonstration for the Hongyan system, which ultimately will comprise 320 satellites and be completed by 2025.
SpaceBridge Completes Delivery of Multiple Spot Beams HTS, Multi Service Ka Broadband Satellite Network to Oman’s leading operator, SCT in Oct 2021
Close to 2000 locations were connected by SpaceBridge infrastructure to support the network which provides a multi-service internet connectivity over SpaceBridge award winning WaveSwitch™ multi-waveform platform.
The network delivers services over Arabsat HTS Ka Satellite enabling communities, enterprises, mobile network operators (MNOs), maritime, consumers, government and military entities to transmit real-time application data over Satellite. SpaceBridge network architecture is supporting simultaneously layer 2 and layer 3 in compliance with article 44, from the Telecommunications Regulatory Authority (TRA) of Oman. Transfer of knowledge from SpaceBridge to SCT is being accomplished through diligent virtual and in person training sessions along with in country managed services.
The network proved its resilience when Cyclone Shaheen made landfall in Oman on October 3rd, 2021. SpaceBridge’s VSAT Network remained connected using its WaveSwitch™ technology despite the widespread flooding, heavy rain and winds of up to 150km/h (93 mph) along Oman’s northern coast.
ISRO: High-throughput satellites
India is on the cusp of a satellite-driven digital or broadband revolution, similar to DTH or direct-to-home broadcasting of the 2000s, with a plan to deploy five high-throughput communication spacecraft starting, according to a space scientist heading the project at Indian Space Research Organisation.
The first of them, GSAT-19, is slated for launch from India in December. It will showcase the country’s technology capability in the new area of spectrum efficiency that is trending across the globe, said P.K. Gupta, Project Director for this and GSAT-11
“We are also considering GSAT-20 besides two next generation spacecraft HTS-1 and HTS-2 of very high capacity of 100 gbps each, which will cover the country’s total land mass,” he said.
ISRO will also test new technologies with its HTSs, such as the new flexible ‘bus’ or satellite assembly platform, electric propulsion, Ka band, lithium ion batteries, among others.
It will drive a next generation technology revolution. Individuals, planners in government, businesses like banks, ATMs, reservation systems, cellular and private networks and users in remote areas are expected to benefit from improved connectivity.
Next-generation multibeam Very high throughput satellite (V/HTS) systems aim at achieving Terabits/s throughputs with thousands of spot beams. Conventional radio frequency (RF) Ku-/Ka- band feeder links, between gateways and satellites, are unable to achieve such throughputs due to limited spectrum availability in these bands. Free space optical (FSO) feeder links present a promising alternative to RF feeder links and have gained increased attention lately in the satellite community.
Newtech sees two key further trends on the space segment : the emergence of Low-Earth-Orbit satellite (LEO) constellations and more flexible, high-capacity GEO HTS payloads. LEO constellations will further complement the GEO HTS capacity in orbit. On the ground segment, one of the key technologies to enable commercial success of the LEO satellites is the availability of cost-effective, electronically steerable Flat-Panel-Antenna’s (FPA) to follow the satellite movement and handover between two satellites.
On the other hand, most VHTS satellite systems currently assume that the traffic requested per beam is uniform, but the real traffic demands are non-uniform in the service area. The uniform distribution of the offered capacity of VHTS systems causes some beams to waste resources while others may not have enough resources.
Thus a possible solution to this problem is to use flexible payloads. However, most of the existing SatCom payloads do not offer any flexibility in terms of bandwidth or coverage. At the same time, power flexibility can be achieved instead by modifying the working point of the onboard amplifier according to the transponder loading.
Technologies currently exist that allow the payload to allocate resources, e.g., power, bandwidth flexibly, or beam-hopping illumination time, but these technologies significantly increase the cost of the payload, consequently losing the VHTS advantages to reduce the cost of Gbps in orbit, plus it adds latency due to processing time.
For GEO satellites the trend is to introduce new concepts that bring more flexible and software-enabled satellite payloads. Most of today’s HTS have a fixed capacity and footprint allocation. Future HTS will be able to allocate the available capacity according to where demand is located geographically at any given time. Along the same lines, Newtec is innovating the ground segment so that services can be delivered in an optimal and very cost-effective way.
Beaming hopping is a technique which allows satellites to shift capacity from one beam to another in response to demand on the ground. This is done by means of time-division multiplexing using one frequency, as opposed to the older technique of separating spot beams by “color” (frequency divided by polarization).
Customer data needs can now be measured constantly and capacity can be allocated to different beams, according to demand. The flexibility is achieved by changing the distribution of capacity in different beams on a time basis using a beam illumination plan that is communicated from the gateway to the satellite and can constantly change
Beam hopping also allows for better coverage to mobile traffic, such as in-flight entertainment and connectivity (IFEC) systems. Beams can be activated and targeted at specific air and sea routes only when it is needed. This allows for a high-quality, high capacity service while also reducing power use.
Since beam hopping technology has been incorporated into the DVB-S2X standard, there is now a high degree of interoperability with different satellite systems made by different equipment vendors using the same beam.
OneWeb to Lead Beam-Hopping Satellite Project Funded by UK
OneWeb has been tapped to lead a consortium of space companies to develop a satellite that can beam hop, switching which part of the world it covers. The group has received about $45 million (32 million pounds) from the UK Space Agency, through the European Space Agency’s (ESA) Sunrise Program. A demonstration satellite is set for launch in 2022.
The satellite is nicknamed Joey-Sat, like a kangaroo joey. It will be designed to hop between beams, in order to remotely direct beams of coverage to certain locations to deal with demand.
Very High throughput satellites (V/HTS) Market
According to studies from NSR and Euroconsult, the market demand for global GEO HTS services will reach 1.9 Tbps by 2024. In its latest research titled, “High Throughput Satellites: Vertical Market Analysis & Forecasts,” Euroconsult projects that High Throughput Satellite (HTS) revenue will reach $15 billion by 2028 with aggregate capacity leasing revenue over the 10 year period reaching $85 billion by 2028.
It discusses prospects for the nine vertical markets driving growth. These include: Consumer Broadband, Rural Connectivity, Civil Government, Corporate Networks and Energy, Military Communications, Cellular Backhaul and Trunking, Aero In-Flight Connectivity, Maritime Communications, and Video Services. Demand will be driven by nine vertical markets for a 26 percent annual growth rate over the ten-year period covered in the report. Supply is expected to grow by 12 times between 2019 and 2024.
With several non-geostationary satellite orbit (NGSO) HTS constellations going into service during this time period, HTS capacity supply is on the verge of entering a period of unprecedented near-term expansion, jumping from 2,100 Gbps at the end of 2019 to 26,500 Gbps by 2024. While this jump has been anticipated, it is now imminent as high-volume manufacturing and batch launch campaigns are underway for both SpaceX and OneWeb.
“The NGSO constellations are poised to fundamentally shift the HTS landscape,” said Brent Prokosh, Senior Affiliate Consultant at Euroconsult, and Editor of the research. “As opposed to the more regionalized impacts of past HTS supply rollouts, this upcoming boom in supply will have truly global impacts due to the scale, expansive coverage and flexibility of next-generation HTS systems.”
As far as can be seen, demand is largely present in all regions: North America, as a mature and growing market, is leading but is followed by emerging markets in Asia Pacific, Latin America and Africa. The majority of the demand is for broadband services, with forecasters predicting that 1.1 Tbps of broadband services will be delivered using Ka-band. Meanwhile, “only” 50 Gbps will make use of Ku-band HTS capacity
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