High Technology Letters ISSN NO : 1006-6748

Satellite Backhaul Architecture for Next-Generation Cellular Networks: Necessity and Opportunities

Dimov Stojce Ilcev Space Science Centre (SSC), Durban University of Technology (DUT), Durban, South Africa, E-mail: [email protected]

Abstract: In this paper is introduced a new cellular communication systems and their possible integration with other radio or satellite networks, such as Digital Video Broadcasting-Return Channel via Satellite (DVB-RCS) standards as backhaul for rural, remote cellular networks. Within the next generation 5G framework, the Terrestrial Network (TTN) can be augmented with the backhaul of the development of High Throughput Satellite (HTS) and modern mega DVB-RCS constellations meeting 5G requirements, such as high , low latency, and increased coverage for rural, remote and mobile environments. This integration of 5G with DVB-RCS standards will upgrade satellite and IPTV for urban, remote, and mobile applications for ships, road, rails, and aeronautical applications via Geostationary Erath Orbit (GEO) satellites. Mobile Satellite Internet aims at providing the backbone for next-generation 5G broadcasting service through C, Ku and Ka-band DVB-S2 standard for ground and mobile subscribers. It is de facto a mobile interactive broadcast satellite access system, which provides both IPTV broadcasting and high-speed Internet broadband based on DVB-S/DVB-RCS standards, Internet Protocol (IP) network, World Wide Web, and E-solutions globally.

Key Words: DVB-RCS, TTN, HTS, GEO, LTE, MIMO, eMBB, mMTC, LEO, MEO, URLLC, VSAT, HTS ISDN, ATM, UMTS, GPRS

1. Introduction

Since the predominant Japanese cellular phone operator Nippon Telegraph and Telephone Public Corporation (NTT) DoCoMo Inc. initiated the world’s first cellular communication service in December 1979, the modern technology of personal communications has continued to develop every decade, evolving to new generation systems. Together with the progress of technology and innovations services have continued to evolve, from the first generation (1G) to the second generation () providing phone calls as a main means of communication, SMS as short E-mail messages. Besides, from the third generation (), data transfer of “i-mode” and multimedia information such as photos, music, and videoconferencing could be communicated using cellular personal devices. From the current fourth- generation (), have been explosively popularized by high-speed communication technology exceeding 100 Mb/s using the Long Term Evolution (LTE), and a wide variety of multimedia communication services have appeared. Thus, the 4G technology continues to evolve in the form of LTE-Advanced and has now reached a maximum communication speed close to 1 Gb/s. In the next stage of cellular improvements, the NTT DoCoMo Company plans to initiate services based on the fifth-generation (5G) cellular communication system in the spring of 2020, as a more technologically advanced system.

2. Development and Deployment of the New Generations Cellular Networks

Menwhile after the announcement of further development of new 5g cellular techniques a fierce race, has begun which country de facto will be the first in technological and political terms. Thus, it turns out that Japan was the first to start that 5G race, but that China was the first to reach the finish line. Based on an article "China is racing ahead in 5G. Here’s what that means", published online on 18 December 2018 by Elizabeth Woyke, the following is quoted: "Last fall, the Fangshan government and China Mobile, the country’s largest mobile operator, outfitted a 6-mile (10-kilometer) road with 5G cell towers. Since September 2018, companies have been using the connectivity to test 5G communications between autonomous vehicles and their surroundings. The 5G network transmits data from car sensors, roadside sensors, and video cameras installed above the road to a local data center, which analyzes the information and sends it back to the vehicles to help them navigate". In that plan of development, for the first time during October 2019, three major wireless carriers in China launched 5G networks, such as China Mobile, China Telecom, and China Unicom. While coverage is limited in some areas, Beijing, Shanghai, and Shenzhen are the cities with the best coverage thus far. Because Chinese authorities control the implementation of the technology, some experts wonder if the 5G rollout processes throughout the vast nation will be slow. Although the implementation of 4G technologies did not occur until late 2013, many years after , Japan, the United States, and other nations had 4G technologies. However, China's top companies seem determined to not replicate earlier 4G mistakes and have done an impressive amount of testing and infrastructure build-out of the 5G network. The Global System for Mobile Communications (GSMA) projects China will have 460 million 5G connections by 2025.

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In April 2019 South Korea is ahead of other countries in 5G deployments, which has rolled out 5G to 85 cities as of Jan. 2020. Government officials estimate 90% of Korea's mobile users will be on a 5G network by 2026. The key to South Korea's success seems to stem from the collaboration of three carriers that have worked on 5G deployment: SK Telecom, LG Uplus, and KT Corp. This KT Company completed a successful trial of a system from NEC Corp. using extremely high frequencies for transmitting data at up to 3.2 Gb/s (gigabits per second) in the Taebaek Mountains. NEC’s iPasolink EX ultra-compact microwave system links between LTE base stations to enable telecommunication, which is much easier than laying fiber for the links. The microwave system conveys data at frequencies of 70 to 80 GHz, which keeps more signals going through the air than other systems and uses a form of encoding that lets more data be transmitted. In July 2016, the US Federal Communications (FCC) began creating rules for 5G technologies, making the USA the first country opening a high-band spectrum for the technology. However, in reality only on 3 April 2019 the US government introduced 5G mobile services in parts of Chicago and Minneapolis. As the US governemnt officially announced, customers in those cities were the first in the world to have a 5G-enabled smart phone connected to a 5G network. Japan was the first to start developing 5G technology, but it has met its goal to launch 5G mobile service by 2020. Japan’s largest wireless carrier, NTT DoCoMO began its quest for 5G in 2010 with initial experiments. However, only in September 2019, the company rolled out pre-commercial 5G services. The test phase went well, and NTT DoCoMo began offering consumer 5G services on 25 March 2020. The Swedish company Ericsson and have launched Russia's first 5G zone in central Moscow on Tele2's commercial network, setting into motion an agreement they signed in June 2019. Ericsson said it has supported Russian operator Tele2 in upgrading its infrastructure with 25,000 5G-ready base stations across Russia in an 18-month period. The update of vendor, the new 5G networks will cover all 27 regions of Russia and will increase capacity and enhance network performance. The 5G networks in the UK are launching in a very staggered manner, as some have been available since May 2019, while we're still waiting for others to roll out. Even with the new networks that have launched, their 5G offerings aren't available nationwide, and on top of that most phones don't support 5G yet, so most people can't take advantage of the new, super-speedy connectivity yet. One year on from launching 5G in the UK, has become the first UK operator to showcase the next phase of 5G technologies, with a new network built for Coventry University. The new network, which uses what is known as ‘Standalone’ 5G technologies, will be used to show the true benefits of 5G, including ultra-low latency, guaranteed speed performance, and the Internet of Things (IoT) on a never-before-seen scale.

3. How does 5G Network Work?

The 5G technologies is a new digital wireless system for transforming bytes or data units over the air. It uses a 5G New Radio interface, along with other modern technologies, that utilizes much higher radio frequencies (28 GHz compared to 700 to 2500 MHz for 4G) to transfer exponentially more data over the air for faster speeds of transmission reduced congestion, and lower latency, which is the delay before a transfer of data begins following an instruction. This new interface, which uses a millimetre wave spectrum, enables more cellular devices to be used within the same geographic area; 4G can support about 4,000 devices per square kilometre, whereas 5G will support around one million. This means more Netflix streaming, voice calls, and You Tube carried, without interruption, over the limited air space. In Table 1 is presented comparison of the main features for 3G, 4G and 5G cellular networks. The old 3G bandwidth was 2 Megabit per second (Mb/s), while the current 4G is 200 Mb/s and 5G is 1 Gb/s or 5 times higher than 4G. As stated, the values of latency for the 5G networks are much better and transmission speed is higher up to 16 times.

Table 1. Comparison of 3G, 4G and 5G Main Features

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The 5G network also uses a new digital technology called Massive Multiple-Input Multiple-Output (MIMO) technology, which stands for multiple input multiple output, that uses multiple targeted beams to spotlight and follow users around a cell site, improving coverage, speed and capacity. Current network technologies operate like floodlights, illuminating an area but with lots of wastage of the light and signal. Part of the roll-out of 5G involves installing Massive MIMO and 5G New Radio to all mobile network base stations on top of the existing 4G cellular infrastructure. Compared to third-generation mobile networking, 4G enabled previously impossible quality video streaming and calling on the go, meaning live TV is now routinely watched on the daily commute. More video streaming, however, has increased congestion in the . Overall, due to the new technologies, spectrum, and frequencies it uses, 5G has several benefits over 4G; higher speeds, less latency, capacity for a larger number of connected devices, less interference and better efficiency. Many of these use cases for security could benefit from network slicing - splitting of the network to tailor speed, capacity, coverage, encryption, and overall security, which can be achieved much more easily with 5G networks.

4. Main Challenges Facing 5G Networks

It’s expected that 5G, the much-discussed upcoming broadband cellular communications standard, will have a big impact once the network rollout is on the market. By 2025, 5G networks are likely to cover one-third of the world’s population. The impact on the mobile industry and its customers will be profound. Thus, the speed and bandwidth of the 5G cellular networks would be such that it could effectively replace home internet connections currently using Wi-Fi. The Consumer Technology Association has reported that 5G will reach speeds of 10 Gb/s, making it 100 times faster than 4G. This means that a two-hour movie that would take six minutes to download on 4G, would take less than four seconds to download on a 5G system. Making it a reality comes with some challenges along the way. Here are five that will figure prominently throughout the process. The 5G networks is more than a new generation of technologies; it denotes a new era in which connectivity will become increasingly fluid and flexible. It will adapt to applications and performance will be tailored precisely to the needs of the user. Working closely with the mobile operators pioneering 5G, the Global Mobile Operator Data (GSMA) is engaging with governments, vertical industries including automotive, financial services, healthcare providers, education, transport operators, tourism, utilities, and other industry sectors to develop business cases for 5G applications. There are several challenges to developing and deploying 5G cellular networks on the road worldwide and that will figure prominently throughout the process, such as follows: Frequency bands, Cost to build and cost to buy, Regulations and standards, Security and privacy, Deployment and coverage, Improvement of the ecosystem, and last is the necessity for the further new development of 6G networks.

5. Evolution and Enhanced Coverage of 5G into 6G Wireless Networks

As stated above, the commercial introduction of 5G has already begun worldwide, however, in November 2019 China has officially launched research and development work for its 6G wireless networks. The country only just turned on its 5G networks earlier this month, ahead of an initial 2020 schedule. Namely, the biggest Chinese cellular operator Huawei is beginning 6G researches for the development-advanced networks that may evaluate and move far beyond smartphones today. On the other hand, although the Japanese NTT DoCoMo company started 5G pre-service in September 2019 and is scheduled to start 5G commercial service in the spring of 2020. However, some technical issues and further expectations that need to be actualized in 5G have already been found, and so further technological enhancements in the form of 6G evolutions became necessary as well. However, some technical issues and further expectations that need to be actualized in 5G wireless networks have already been found, and further technological enhancements in the form of 6G evolutions are necessary for the near future. In particular, the current technical challenges facing 5G are high-frequency uplink millimeter wave (mmW) band coverage and mobility improvement, uplink performance enhancement, high requirements for industry and society users cases, new approaches for enhancing cybersecurity, improving the coverage and uplink performance in Non-Line-of-Sight (NLOS) environments are issues that can be discerned from 6G- related trials, and what is the biggest challenges of all generations cellular networks to provide backhaul some suburban, rural and remote regions via satellite networks or Stratospheric Platform Systems (SPS). Although there are barriers to the technology becoming commercially viable, GEO satellites supported by SPS as High-Altitude Pseudo Satellites (HAPS) constellations are also being presented as a new possible alternative for backhaul of cellular networks. It is hoped these satellites, deployed in the stratosphere at an altitude of 20km, will provide connectivity to remote areas, such as rural, coastal, or mountainous regions.

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Figure 1. Evolution of Technological Development Toward 6G Wireless Networks

In the initial 5G standardized radio technologies focused on Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC) and a part of Ultra-Reliable and Low Latency Communications (URLLC) networks. In Figure 1 is illustrated the evolution schemes of the technological development toward 6G to actualize the above-stated concepts. In the future, there will be use cases that require extreme performance that even 5G cannot achieve, as well as new combinations of requirements that do not fall into the three categories of 5G: eMBB, mMTC, and URLLC technological concepts. In order to examine requirements, the main task will be to investigate 6G use cases, technological evolution, society issues, and the worldview in the 2030s when 6G systems will be introduced. The use cases and problem solutions expected in 5G will mostly be actualized in the 2020s and expand from there. Thus, it is considered that wider and deeper diffusion will be required as a type of further development in the 2030s.

6. Expanding Cellular Connectivity via GEO Satellite Backhaul

Cellular operators already use backhaul of several transmission means, such as fiber optics liner, microwave, and satellite, to connect their cell sites to the backbone and/or to back-up unreliable terrestrial connections. In developed markets, the satellite systems are already playing a key role as cellular network deploy satellite- enabled backhaul to improve their 4G coverage and relieve congestion in metro areas. Satellite backhaul is also frequently used to backup critical sites served by a single fibre or by unreliable terrestrial connections, as well as in cases of emergency response. In case of outage of the main connection, traffic is instantly swapped over to the always-on satellite connection resulting in little or no traffic loss. In addition as innovations in technology such as High Throughput Satellites (HTS) at GEO and Non-GEO satellite constellations at medium and low orbits continue to be deployed, the cost of satellite service for backhaul has dramatically reduced in price. In Figure 2 is illustrated the difference between the traditional GEO satellite beam and HTS GEO satellite spot beam.

Figure 2. Difference between Traditional GEO Satellite Beam & HTS GEO Satellite Spot Beams

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Figure 3. Shared Bandwidth Architecture of Fixed DVB-RCS+F Backbone for 5G Cellular Networks in Remote Environments

The use of GEO satellite constellations to provide support cellular-backhaul began in the early 2000s and has increased as many countries adopted universal service policies and mobile operators had to cover more and more rural and remote locations where terrestrial backhaul was not available in many cases, or could not be deployed on a timely or cost-effective basis. The traditional GEO satellite communication constellations, as the best cellular backbone solutions with shared bandwidth provide a very large coverage footprint of about 1/3 of Earth surface, typically have transmission capacity below 1 Gb/s and deliver low data rate. However, the enhanced GEO HTS satellites use a large number of spot beams over a particular area and reuse the allocated frequency multiple times to increase the throughput several times. In such a way, spot satellite beams provide high signal strength and increased signal gain, such as Effective Isotropically Radiated Power (EIRP) and Antenna Gain-to-noise-Temperature, (G/T) for the small aperture terminals on the ground, such as interactive (two way) Very Small Aperture Terminal (VSAT) satellite fixed or mobile stations. In Figure 3 is illustrated the C/Ku/Ka-band GEO satellite using shared bandwidth architecture of the fixed DVB-RCS+F backbone for Extension 5G and other new generation of the cellular network in rural or remote environments. The Base Station Controller (BSC) located in the urban area is linked to the DVB-RCS Hub or Ground Earth Station (GES) and manages the 4G/5G cellular networks with ISP via land or fiber-optic links. Besides, the BSC terminal is connecting ISDN, ISDN/Broadcasting (ISDN/B), ATM, Universal Mobile Telecommunications Service (UMTS), and General Packet Radio Services (GPRS). The GES terminal via DVB-RCS Hub antenna provides the backbone to remote 4G and 5G repeater towers via GEO satellite forward and return links connecting many VSAT fixed transceivers (transmitter and receiver) or FIT. Each VSAT can connect via land, fiber, or wireless links many repeater towers in one rural or remote cellular network. Because, GEO satellite networks are providing coverage approximately up to 80o North and 80o South are not providing both polar coverage, at the same time there is a resurgence in the deployment Non-GEO satellite networks, such as already developed Medium Earth Orbits (MEO) and Low Earth Orbits (LEO) HTS constellation approaches. These Non-GEO satellite constellations provides true global coverage including both Polar Regions, network-wide uniform service delivery, and substantially reduced latency. Thus, a variety of HTS satellite constellation approaches offer connectivity ranging from fibre replacement services, private wide- area networks, and consumer broadband.

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Figure 4. Architectures of VSAT Modems Connecting in Star Topology for SCPC and TDMA Satellite Networks

The most common GEO satellite backhaul technologies have been either a dedicated point-to-point satellite link known as Single Channel Per Carrier (SCPC), shown in Figure 4 (Left), or a shared link using Multi- Frequency (MF) Time-Division Access (TDMA), shown in Figure 4 (Right). For instance each connection of the SCPC satellite link requires 3 (or more) separate modems with antenna located in the GES or Hub terminal connected via the GEO satellite to 3 or more separate VSAT modems with antennas. However, each connection of MF-TDMA satellite link requires only 1 VSAT modem with antenna located in the GES or Hub connected via GEO satellite to another separate VSAT modem with an antenna. In Figure 5 is illustrated the C/Ku/Ka-band GEO satellite using dedicated bandwidth architecture of the fixed DVB-RCS+F backbone for Extension 4G/5G and other new generation of the cellular network in rural or remote environments. The repeater tower located in the urban area is linked to the DVB-RCS Hub or GES terminal and via DVB-RCS Hub antenna provides the backbone to fixed VSAT station which is connected to just 1 remote 4G/5G rural repeater tower. This one rural repeater tower provides a backhaul link to other rural repeater towers via terrestrial microwave or fiber optic links providing extended rural cellular networks. Therefore, HTS links from GEO or Non-GEO satellite constellations have the capability to complement existing and new coming generations cellular connectivity to enable very high-speed trunking of Voice, Data and Video (VDV), IoT, and other services to a central site, with further terrestrial distribution to local cell sites (e.g. current and future cellular networks), for instance neighboring villages, as shown in Figure 5. In this category, the different interactive (bidirectional) broadband communications are supported via GEO satellite and VSAT to the rural 5G cellular networks.

Figure 5. Rural DVB-RCS Backhaul for 5G via GEO Dedicated Satellite Bandwidth

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Figure 6. Shared Bandwidth Architecture of Mobile DVB-RCS+M Backbone for 5G Cellular Networks in Mobile Environments

Similar to the Fixed DVB-RCS+F Backbone for 5G Cellular Networks in Remote Environments in Figure 6 is illustrated the C/Ku/Ka-band GEO satellite constellation using shared bandwidth architecture of the mobile DVB-RCS+M backbone for extension of cellular network in mobile environments. The BSC terminal in the urban area is linked to the DVB-RCS Hub or GES terminal and via GEO satellites and VSAT or MIT provides the backbone to remote 4G/5G cellular phones onboard ships, land vehicles (road and rail), and aircraft.

7. Ground HUB and Remote VSAT Terminals with Antenna Systems

A dedicated large Hub supports a full single network with up to hundred of thousands of VSAT units connected to 5G cellular networks. The Hub may be located at the customer’s organization central site, with the host computer directly connected to its infrastructure and it offers the cellular customer full control of the network. In periods of expansion, changes in the network, or problems, this option may simplify the cellular customer’s life in one country or globally. In Table 2 are presented different models of Advantech Hub terminals that can be used as backhaul to support from 500 to 180,000 fixed or mobile VSAT in 5G rural or mobile environments.

Table 2. Comparison of Advantech Series of VSAT HUB Terminals

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Figure 7. Grounf VSAT HUB Transceivers (Left Avntech & Right ViaSat) with Ground VSAT Antenna for transmission 5G data

The multi-mode connectivity of Advantech Wireless producer is offering revolves around taking the DVB-RCS standard and evolving it one step further, which most used Discovery 300mHube configurations are illustrated in Figure 7 (Left). This Hub is more cost-effective and can accommodate up to 45 thousand VSAT stations (remotes) and this multi-mode approach delivers open standard benefits to fixed and mobile users for extension of 5G networks in rural or mobile environments. It provides throughput is up to 2x200 Mb/s on each chain and the total forward link capacity is up to 1 Gb/s. However, it provides a throughput of up to 240 Mb/s on each return link block. In Figure 7 (Middle) is illustrated Hub ground antenna that connects Hub with satellites. The ViaSat LinkStar Pro Hub ground terminal can bring to the DVB-RCS networks increased security, reduced total operational costs, and improved network management using the advanced satellite communications technology for IP routing, QoS, security, data acceleration, and compression in one single platform, shown in Figure 7 (Right).

Figure 8. Fixed VSAT Antenna and Units, Shipborne and Airborne Mobile VSAT Antennas for 5G data Transfer

The parabolic antennas for mobile application installations on transport vehicles should be equipped with mechanical satellite tracking systems, which can provide constant tracking of the GEO satellite to provide stable communication when the unit is in motion by keeping the antenna dish constantly directed to the GEO satellite. The VSAT antenna for fixed DVB-RCS applications with VSAT units for fixed and mobile applications are illustrated in Figure 8 (Left) operating on radio frequency C, Ku, or Ka-band. The same or similar VSAT units can be used for installations onboard oceangoing ships with shipborne VSAT antenna shown in Figure 8 (Middle), and for installation onboard aircraft or helicopters can be used airborne VSAT antenna depicted in Figuere 8 (Right). The phased antenna array is a contemporary alternative to parabolic antennas. This type of antenna has many tangible advantages to the parabolic antennas. As an example of the phased antenna array, which is “SpeedRay 1000” low-profile Ku-band satellite antenna, is depicted in Figure 9.

Figure 9. Low Profile VSAT Ku-band Antenna for Trains and Buses

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Conclusion

Satellite backhaul is being used extensively today supporting cellular operators efforts to extend their network coverage in fixed and mobile environments. Urban and semi-urban areas enjoy congestion relief and seamless connectivity by using satellite backhaul, but rural coverage worldwide remains poor with the necessity for more reliable satellite backhaul. Given the technological and business options available for using satellite backhaul and recent technological innovations such as GEO and Non-GEO satellite HTS constellations, there is good reason for cellular operators to implement satellite service for backhaul. In addition to the socio-economic impact, cellular backhaul via satellite significantly increases the subscriber base and allows them to guarantee full reach in rural, remote, and mobile environments.

References

[1] ETSI, (2012), “DVB Standards”, Sophia Antipolis Cedex, France, 112 [2] ETRI, (2005), “Mobile DVB-RCS Systems”, Daejeon, South Korea, 23. [3] Ilcev D. S. (2009), “Satellite DVB-RCS Standards for Fixed and Mobile Commercial and Military Applications”, Microwave Journal, Norwood, USA, 16. [4] Ilcev, (2017), “Global Mobile Satellite Communications for Maritime, Land and Aeronautical Applications - Volume2”, Springer, Boston, US, 686. [5] Maral G. (2003), “VSAT Networks”, John Wiley, Chichester, UK, 296. [6] ViaSat, (2006), “Fixed and Mobile DVB-RCS Routers”, Carlsbad, CA, US, 26. [7] Ilcev D. S. (2008), “Presentation of Mobile DVB-RCS”, DUT, Durban, South Africa, 55. [8] Orbit, (2015), “ Mobile DVB-RCS VSAT Outdoor Units”, Netanya, Israel, 21. [9] Everett J., (1992), “VSAT- Very Small Aperture Terminals”, IEE, Peter Peregrinus, London, UK, 192. [10] Advantech, (2006), “DVB-RCS VSAT Hub Series”, Montreal, Canada, 29. [11] Richharia M. (2001), “Mobile Satellite Communications – Principles and Trends”, Addison-Wesley, Harlow, UK, 560. [12] Ilcev D. S. (2011), “Global Mobile CNS”, Manual, CNS Systems, Durban, South Africa, 285. [13] GT&T, (2003), “VSAT Equipment”, Louvain-La-Neuve, France, 25 [14] Ilcev D. S. (2011), “Mobile Antenna Handbook”, ”, Manual, CNS Systems, Durban, South Africa, 211. [15] RaySat, (2015), “Mobile DVB Antenna Solutions”, Gilat, Israel, 29. [16] Minoli D. (2008), “IP Multicast with Applications to IPTV and Mobile DVB-H”, John Wiley, Chichester, UK, 376.

BIOGRAPHY OF AUTHOR

Prof. Dimov Stojce Ilcev is a research leader and founder of the Space Science Centre (SSC) for research and postgraduate studies at Durban University of Technology (DUT). He has three BSc degrees in Radio, Nautical Science and Maritime Electronics and Communications. He got MSc and PhD in Mobile Satellite Communications and Navigation as well. Prof. Ilcev also holds the certificates for Radio operator 1st class (Morse), for GMDSS 1st class Radio Electronic Operator and Maintainer and for Master Mariner without Limitations. He is the author of several books in mobile Radio and Satellite CNS, DVB-RCS, Satellite Asset Tracking (SAT), Stratospheric Platform Systems (SCP) for maritime, land (road and railways), and aeronautical applications.

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