Highly informative communication systems HTS and LEO / MEO-HTS: Paper projects or cutting-edge area of the space industry

The global telecommunications and IT market development is based on continuous growth of the volume of information generated in the global community. Figures 1 and 2 present traffic volume assessments based on CISCO research.

By 2020, the number of user terminals will exceed 25 billion (see Fig. 3). Other researches yield similar forecasts. It is obvious that these forecasts incentivize the search for new efficient ways of information dissemination and delivery to end users. There is an ongoing search for appropriate technological solutions both for terrestrial communication systems and for satellite communications.

Today, development of the satellite communication and broadcasting market is associated with creation of new fixed satellite service systems based on super high information capacity, multi-spot beam geostationary HTS satellites. Indeed, modern satellite communication and broadcasting technologies are already actively competing with terrestrial technologies [1, 2]. The performance of an HTS-based system surpasses that of traditional communication satellites by over 30 times [2]. Moreover, subscriber connection costs are lower [2], and channel speeds provided with the use of HTS satellites are higher than the average speed of Internet access in cellular networks (see Fig. 4).

Today, satellite channels provided with the use of HTS are practically identical to the average Internet access speeds when using cable channels (see Fig. 5).

This is also corroborated by the results of actual average access channel speed measurements in the USA (see Fig. 6) for various operators and technologies [3]. It should be noted that Hughes and Viasat exhibit an average access speed reduction trend for satellite technology (see Fig. 6). This signifies that their satellite networks are already oversaturated and require additional resources (a new additional Echostar 19 (Jupiter 2) HTS satellite was launched on December 20, 2016 for Hughes network, and Viasat-2 satellite launch is planned for early 2017).

Judging by analytical researches of Russian (VISAT-TEL, Jonson & Partners Consulting) and foreign (Euroconsult, NSR, etc.) companies, a new market segment has taken shape – broadband access based on HTS technology in Ka and Ku bands. Thanks to the Federal State Unitary Enterprise "Russian Satellite Communications Company" (RSCC), the Russian satellite fleet currently possesses the Express-AM5, Express-AM6 and Express-AM1 satellites with payloads that include HTS retransmission equipment (see Fig. 7).

Broadband access systems on the basis of these satellites are now operating and offering services that are accessible in at least 50% of Russia. Recently, Gazprom Space Systems has also started creation of a Yamal-601 satellite that belongs to the HTS type. After it is put in operation, satellite broadband services will be available in 90% of Russia.

HTS-based systems (according to information of analytical research companies NSR, Euroconsult and publications [2]) have the advantage of significantly lower cost of information unit transmission in comparison to traditional satellites. The HTS satellite communication technology advantages are especially evident with respect to Fiber Optic Lines and 4G in areas with low household density. As a result, usage of HTS satellite-based system resources is expanding in global practices for provision of services to small enterprises, public institutions, and private subscribers in the framework of digital inequality elimination (for example, under national programs in Australia (NBN), in the UK (BDUK)). One of the priority areas for commercial usage of HTS satellite resources today is considered to be creation of communication systems on the basis of these satellites for provision of services for sea-going vessels and airplanes, as well as for unmanned aerial vehicles.

Information capacity of a modern purpose-built HTS satellite reaches 130 Gbps. Their total capacity in the world already amounts to almost 1200 Gbps, which is approximately two times bigger than the resources of all traditional communication and broadcasting satellites currently operating in geostationary orbit (GSO). Launches of HTS satellites with 300 Gbps capacity are planned for early 2017, and, according to forecasts, by the year 2020 the capacity of a single HTS will reach 500-1000 Gbps.

HTS drawbacks

Along with the advantages of HTS systems, however, they also have a number of essential drawbacks as follows.

1. As opposed to traditional satellite systems, the HTS based ones are "closed systems" – it is impossible to simultaneously use terrestrial subscriber satellite equipment of different manufacturers.
2. It is impossible to flexibly redistribute terrestrial central gateways when new tasks arise in the process of system operation, because their linkage to geographical coordinates and subscriber spot beams is fixed even at the satellite payload planning stage.
3. A prolonged signal propagation delay (up to 400 ms) is a physical limitation for any types of GSO satellites.
4. Using GSO satellites, it is impossible to provide services to regions with latitudes within 65-70 deg. North in an efficient and reliable manner, and within 75-78 deg. N services can only be provided with the use of narrowband channels.

Attempts to raise the system flexibility by creating flexible payload, including by way of switching to digital methods of onboard information processing, result in reduction of the system cost effectiveness. In other words, system cost effectiveness is traded in for its flexibility. One example of such a solution is the HTS satellites in the Epic system that is being created by Intelsat.

Deterioration of communication quality at high latitudes is common to all geostationary communication and broadcasting satellites, but for HTS satellites this problem is exacerbated by the need to use Ku/Ka bands.

Creation of multiple-satellite systems

It is obvious that signal transmission delay can only be reduced by switching from GSO usage to lower orbits and creation of multiple-satellite systems. The lower the orbit, the fewer satellites are required to serve the given operation area. Moreover, when multi-beam technology is used, like geostationary HTS satellites, such systems acquire additional advantages. Satellite mass can be significantly lower than that of GSO satellites, but their information capacity reaches several Gbps, and system capacity – dozens or more Tbps. Besides, the cost of a single satellite can be lower by several orders of magnitude, and the cost of putting them in orbit can be essentially lower in comparison to geostationary satellites.

Such satellites in 800–1500 km orbits received the name of LЕO-HTS, and the name of MEO-HTS in orbits of about 8 thousand km, i. e. in minimum radiation activity zones (see Tables 1 and 2). Collectively, they can form a space fleet with a capacity that is by an order of magnitude greater than a "heavy" GSO HTS satellite. As of today, there is only one actually existing system that can conditionally be classified as MEO-HTS type, the O3b system. The number of planned LEO/MEO-HTS systems, however, is growing at extremely high rates. The interest to these systems is generated by many factors that include resolution of the above mentioned problems of geostationary HTS satellite systems. Judging by design performance specifications and investor statements, the cost of information unit transmission in LEO/MEO-HTS systems is several times lower than in case of geostationary HTS satellite usage. Besides, such systems are intrinsically global.

Among the better known examples are the OneWeb (L5 network) and the SpaceX (Strem network) projects. There are at least 10 announced (or in preparation for submission to ITU) LEO/MEO-HTS projects that are known today (see Tables 1 and 2). And at least 10 more projects that are next in turn, including the BRICS countries' projects – The Star of Happiness (China) and Astome (India). An overwhelming majority of projects have been declared through the US Federal Communications Commission (FCC). In Russia, the only MEO-HTS system that has been brought to the level of preliminary application to ITU is the so-called "Skif" initiative.

Projects with the use of multiple spot beam HTS satellites in highly elliptical orbits are also emerging. These projects are referred to as HEO-HTS, but their significance is yet to be clarified, because their effectiveness is incomparably lower than in LEO/MEO-HTS systems [4].

Russia's participation in LEO/MEO-HTS projects

LEO/MEO-HTS systems are not specified in the Federal Space Program of Russia for 2016-2025 (hereinafter – Federal Space Program). Such systems are not included in the plans of Russian satellite operators either. There are various opinions in the global and Russian expert communities with respect to expediency and cost-effectiveness of such systems. Judging by the declared project parameters, however, these new systems have a high level of cost-effectiveness.

The expediency of Russia's participation in implementation of international LEO/MEO-HTS projects and the problems of developing a Russian LEO/MEO-HTS project with international participation were actively debated and discussed during the conference at the level of expert community.

In the opinion of speakers and experts who participated in the discussions, international cooperation is required for creation of any LEO/MEO-HTS systems due to their intrinsically global nature.

In this respect, special attention should be paid to participation of Russian companies and specialists in international organizations that are currently developing new standards and rules for participation in the future digital telecommunications market.

Quite naturally for an independent expert community, there were many critical comments with respect to establishment of state programs related to development of satellite communications and application of satellite communication technologies.

In particular, the experts noted that wider application of advanced satellite communication technologies with the use of already existing Russian HTS satellites can ensure significant and quick progress in the development of telecommunications infrastructure. Moreover, subscriber connection costs in many cases (e. g., for connection of small communities) will be noticeably lower than in case of countrywide usage of Fiber Optic Lines, as stipulated in Article 57 of the Federal Law "On communications". These advantages are especially noticeable in areas with low household densities. Naturally, the issues of creating space programs were also touched upon. It was noted that potential projects included in the Federal Space Program are not in line with the current development trends in the satellite communication and broadcasting segment of the global industry. Once again, critical attitude was stated with respect to the "Gonets" system, which, in the experts' opinion, is now obsolete.

Besides, the experts are noting that practical implementation of any of the LEO/MEO-HTS projects in Ku/Ka bands will lead to problems of satellite usage (or even make it impossible) for these frequency bands in Molniya and Tundra type orbits (including their usage for HEO-HTS projects). These orbits are optimum for provision of services to Russia's northern and arctic regions and they are stated as promising in the Federal Space Program.

Conclusions

For now, it is problematic to provide an unequivocal answer to the question of practical feasibility of the new LEO/MEO-HTS projects. The technologies stated in the projects for implementation of LEO/MEO-HTS communication satellites are currently still in research phases. The new LEO/MEO-HTS projects require exhaustive research, including simulations of these systems and their comprehensive technical and economic analysis. But it is manifestly obvious, however, that LEO/MEO-HTS projects are really needed for development of the scientific and technological potential of the space industry as a whole and of communication systems in particular. Moreover, satellite fleet creation is not the only important task. Success of the LEO/MEO-HTS projects is no less dependent on resolution of technology problems in implementation of the subscriber segment. Exploration work in this area is no less important than scientific research in the sphere of space segment creation. Technological solutions in creation of subscriber segment equipment may become a major factor in assessment of LEO/MEO-HTS projects' investment attractiveness.

Literature

1. Anpilogov V. R., Mass service satellite systems in Ka band // Communication Technologies and Equipment Magazine. Special issue of Satellite Communications & Broadcasting-2011. – 2010. No. 6-2 – Pgs. 16-21.
2. Anpilogov V. R., Urlichich Yu. M., Satellite technology development trends and criteria for assessment of their technical and economic efficiency // Communication Technologies and Equipment Magazine. – 2016. No. 2. – Pgs. 46-53.
3. Measuring Broadband America. Fixed Broadband Report. A Report on Consumer Fixed Broadband Performance in the United States. Federal Communications Commission, 2016.
4. Multiple-spot beam high-throughput satellite systems. Satellite broadband based on HTS technology. Analytical report by Jonson & Partners Consulting, under general editorship by Anpilogov V. R. – December 2016.

Published: Communication Technologies and Equipment Magazine, №6, 2016, special issue ”Satellite Communications & Broadcasting 2017”, pp.44-48