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The tussle over 28 GHz band has become serious

The 28 GHz band in India so far has been reserved for satellite communication services. The providers as Hughes Network Systems, Inmarsat, and Viasat have based their business plans in India on its exclusivity.

Hughes Networks’ has plans to build a satellite exclusively for India, entailing an investment of USD 500 million. (Incidentally, the company is awaiting approval since 2016 from the Indian Space Research Organisation under the Department of Space). SpaceX & Amazon’s Project Kuiper are likely to use this band for running both their satellite gateways and terminals to deliver high-speed broadband.

The satellite service providers have urged TRAI to disregard any attempts by the terrestrial 5G proponents to seek identification of the 28 GHz band in India for terrestrial 5G and to instead preserve access to the 28 GHz band for satellite broadband services. If this satellite spectrum is sliced off, it would rapidly reduce the serving capacity of satellite systems and the number of people that can be offered quality broadband services in India. They expect 100-200K users in the next couple of years.

Over 120 GSO fixed satellite service (FSS) Ka band satellites, including those being built and deployed by ISRO for use in India are now in orbit around the world, providing a wide range of services to individuals, businesses, and governments. Many more Ka band GSO satellites are under construction to meet the growing demand for service and need to use the 28 GHz band to meet this demand. The 28GHz (27.5-29.5 GHz) band is key for domestic gateways for FSS with payloads in Ka-band. On account of capacity requirements, the entire band is normally needed for gateway use.

In addition to the wide variety of conventional fixed uses of the band, the use of Earth Stations in Motion (ESIM) is growing rapidly. ESIM operation will protect terrestrial systems in the 28 GHz band. This helps explain why the 28 GHz band was not identified for possible use by IMT under WRC-19 Agenda item 1.13.

Overall, the 28GHz band is a poor candidate for global harmonization/economy of scale. Use by 5G on a national basis will disrupt global harmonization for satellite use. Satellite operators argue that the 26GHz (24.25-27.5 GHz) band is an excellent alternative to the 28 GHz one for 5G, with much better chances of global harmonization. Also, there is ample other spectrum being studied for 5G under WRC-19 Agenda Item 1.13.

SpaceX proposes that the government take this opportunity to set inventive policies that reward entities that develop and utilize efficient technologies by evolving traditional approaches into those that encourage sharing and reward efficient users. Conceptually, policies like these reward efficient users with greater spectrum availability and penalize inefficient users with higher costs. SpaceX supports a band-splitting model for spectrum sharing among NGSO satellite operators that rewards the system that uses spectrum most efficiently. Ideally, any spectrum policies should primarily set the terms for successful coordination between operators.

With that goal in mind, SpaceX has proposed a default rule under which—absent successful private coordination—two NGSO operators split the spectrum during the specific in-line events that occur between their two systems. To encourage all operators to develop systems better able to share spectrum, the NGSO operator that uses spectrum more efficiently should be awarded first choice of bands to select in the split of spectrum during in-line events. SpaceX notes that the current rule in the United States actually sets the wrong incentives by granting this right of first spectrum choice to the operator that is first to launch a satellite and operate in the frequencies in question, because it encourages operators to quickly launch a small number of satellites without consideration of actual service provision or spectral efficiency, leaving the potential for an inefficient system that hinders any that follow. Instead, a rule that assigns first choice of spectrum to the more efficient NGSO system creates a race-to-the-top in which operators compete to develop the most spectrally efficient technology. This competitive approach would inherently redound to the benefit of Indian consumers, who would accrue better speeds, greater choice and lower costs. And, ultimately, satellite operators that can share with each other are also better able to share with other technologies, such as terrestrial wireless services.

Underlying such proposals is a straightforward principle: aggressive performance metrics set by the regulator, with industry expected to compete with technology and operations that can meet that metric. Given the rapid development of all wireless technologies—terrestrial and satellite—performance-based policies like the one described above will drive more competition than a tax-based system that risks deterring competition and becoming quickly outdated.

The DoT is interested in including the band in the 5G spectrum auctions expected to be held early 2022. They would like the mobile operators, Bharti Airtel, Voda Idea, and Reliance Jio to bid for 50 percent of the spectrum available.

The telcos too are totally in favor of this. Their stand is that they cannot spend time and effort to develop trials around on these bands unless the government approves these bands for the auction. They want the Department of Telecommunication to release the revised National Frequency Allocation Plan (NFAP).

On May 17, 2021 they reiterated to DoT to include mmWave band airwaves in NFAP so that can get clear information regarding the trials and the auction. “A reminder has just been sent to DoT that the revised NFAP has still not been finalized by its Wireless Planning & Coordination wing even after various meetings of the working groups were held and inputs provided by all stakeholders,” said SP Kochhar, director-general of the COAI.

Vodafone Idea insists that to ensure optimum utilization of precious and scarce natural resource, spectrum to be used for satellite-based services should be put to auction route only before allocations. Any other administrative allocations would cause a huge loss to the national exchequer. The spectrum availability should not be blocked for any niche service like satellite-based IoT services.

Bharti Airtel has been silent on this, since it also owns OneWeb. The service provider has applied for a global mobile personal communication system (GMPCS) licence for providing satellite broadband services. OneWeb is in advance preparations to start laying the required infrastructure like ground stations in India to enable services. From June 2022 onward, upon the completion of the LEO satellite constellation, it plans to offer India and the entire South Asia 24×7 service availability. Satellite communications is extremely useful for providing broadband services in remote, hilly, and inaccessible regions. It is also the only medium through which communication can be established in disaster zones when normal communication gets affected. In satellite communications, services are provided through LEO satellites, through which a box is suspended in remote and hilly regions which creates Wi-Fi spots through which broadband services are provided. India is completely uncompetitive in this segment, satellite broadband rates in India are nearly 30 times that of 4G mobile broadband. Its costs USD 15-20 per GB, compared with USD 0.68 for mobile data.

The telcos’ choice of the 28 GHz band is motivated by several reasons. They maintain that, first, there is extensive licensed but underutilized mmWave spectrum around 28 GHz bands that have been shown to support cellular communications in the range of 500 meter. Second, 28GHz band is still useful to create multipath environments compared to higher frequencies and can be used for non-line-of-sight communications. Moreover, an additional important advantage of exploiting 28 GHz band for wireless backhauling is the possibility of reuse 3GPP LTE functionalities.

For instance, 3GPP LTE allows to reuse the LTE physical layer, originally designed to operate at carrier frequencies around 2 GHz and applied it to higher frequencies up to 40GHz for small cell backhauling. This requires small modification of the numerology to increase the subcarrier spacing. This results in a cost-effective adaptation of existing technology to accommodate the new 5G requirements as well as the opportunity of a quick launch of new features for wireless backhaul links. The 5G services might become unaffordable for consumers in the country.

The 26 GHz and 28 GHz bands provide speed up to 2 Gbps along with a huge capacity, which is important for 5G use cases and these bands are available in other countries.

IEEE in a recent study has proposed that a new method to confirm the possibility of coexistence between the existing satellite services and potential 5G cellular services in the millimeter-wave band according to the frequency-designation agenda of International Mobile Telecommunications (IMT)-2020 for 5G. To evaluate the accumulated interference power of numerous 5G systems distributed globally at a satellite receiver, satellite’s interference reception area may be extended to the entire coverage area, from which only the land area is extracted using the geospatial terrain data of Earth in three dimensions. This enables more accurate interference assessment than conventional methods that only consider the footprint of the satellite’s 3-dB beamwidth.

“The IMT-2020 (5G) systems in the coverage area using the IMT-2020 parameters and modelling documents for the International Telecommunication Union’s coexistence study may also be placed in this. The propagation loss is modelled considering the clutter loss, building entry loss, and attenuation from atmospheric gases. Subsequently, we analyze the interference power received by a fixed satellite service (FSS) satellite operating in the same band and an Earth exploration satellite service (EESS) passive sensor operating in an adjacent channel. Our simulation shows that the FSS satellite receives up to 7.9dB more interference than that obtained from the existing method. Although this is a substantial difference, we find that the protection criteria is still satisfied. However, all EESS passive sensors do not meet the protection criteria in most scenarios, and additional frequency separation or interference mitigation techniques are required to protect these sensors. The proposed method is also applicable to the analysis of non-terrestrial network interference from airships, balloons, unmanned aerial vehicles, etc.

In this work, we proposed an interference-analysis modelling method to check the coexistence of IMT-2020 and the existing satellite services in the mmWave band in relation to the IMT-2020 frequency-designation agenda. In addition, we performed interference analysis and presented the coexistence possibility of IMT-2020 and satellite services when IMT2020 is operated in the candidate bands using the proposed methodology.

TV Ramachandran
Broadband India Forum
“World over, satellite spectrum is authorised for ‘a right-to-use’ by all administrations everywhere and is allocated only by administrative process at charges essentially covering the cost of administration. Unlike terrestrial spectrum, satellite spectrum is never exclusively assigned to the operator but coordinated internationally and shared among multiple operators for different orbital slots and all types of satellites. Thus, the terrestrial concept of exclusivity does not apply and auctioning therefore not applicable.”

”For accurate simulation, we modelled the IMT-2020 using the modelling document proposed by ITU and distributed the IMT-2020 with different environments in the entire coverage area. Subsequently, IMT-2020 was sampled in consideration of only the land area of the satellite’s entire coverage area using map data, and interference analysis was performed in consideration of the various kinds of propagation losses occurring between the ground and space in the mmWave band. Then, we verified the possibility of coexistence compared with the protection criteria of each satellite system.

The simulation results show that the FSS satellite receives interference from many IMT-2020s because it is located at a high altitude. However, due to the high propagation loss and protection criteria, the operation of the FSS satellite is not affected, even when it operates in the same channel as the IMT-2020 in both the 27–27.5 and 81–86 GHz bands.

However, the EESS passive sensor is so sensitive that the low protection standards render it difficult to operate, even if the IMT-2020 is serviced in adjacent bands. In particular, when the main beam of the sensor is directed toward the urban area, the interference of most passive sensors exceeds the protection standard, which is a critical problem for the EESS passive service operations. Therefore, to ensure the coexistence of the two services, consideration should be given to reducing the interference power of the IMT-2020, such as additional frequency separation or interference mitigation techniques.

The proposed interference-analysis method is not limited to IMT-2020 and satellite systems, but can be extended to various interference scenarios such as terrestrial network services and aviation systems. Recently, satellite communication technology utilizing low-orbit satellites has been developing rapidly, and LEO satellite-based mobile communication services are expected to become common in 6th-generation mobile communication. Our study can be applied to research related to the construction of the ground-space integrated communication network,” concludes IEEE in a paper, authored by Yeongi Cho and Hyun-ki Kim; and Maziar Nekovee and Han-shin Jo; and from the Department of Electronics and Control Engineering, Hanbat National University, Daejeon South Korea and Department of Engineering and Design, University of Sussex, Brighton, UK respectively.

The Global Satellite Coalition has proposed a guard band, to reduce interference. The Dominican Republic has made provision of 100 MHz of guard band in the 3.6-3.7 GHz band, although that leads to an enhanced network equipment costs.

The Indian authorities need to take a speedy decision on this. India is way behind the rest of the world. 5G mobile worldwide subscriptions are forecast to exceed 580 million by the end of 2021, driven by an estimated one million new 5G mobile subscriptions every day. It is forecast to become the fastest adopted mobile generation.

A sustainable policy resolution would have to be based on the correct balancing of aspects of equity and respect for rights of existing players with the need for progress through adoption of new technologies.

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