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Spectrum, a shared gem

Importance of coexistence

Spectrum, a shared gem

Opportunities for the coexistence of other radio services in parts of the 6–15 GHz range is the latest hot topic in backhaul spectrum.

Microwave and millimeter-wave spectrums are key assets for the wireless backhaul of 5G, and beyond, with around 10 million transceivers installed around the world. Different frequency bands are used to provide critical transport network infrastructure in all areas, from dense urban to deep rural areas, for ranges from hundreds of meters to beyond 100 km. The traditional bands, 6–42 GHz, remain the backbone for (point-to-point) wireless backhaul, as shown in Figure 2.

Figure 2: Wireless backhaul bands under consideration for radio access

Wireless backhaul bands under consideration for radio access

Source: Ericsson (2024)

A remarkable journey

The E-band (80 GHz) has been on a remarkable journey over the last decade and is now extensively used as a 5G backhaul band. In recent years, there has also been a rapid maturation of radio technology for beyond 100 GHz. Today, there are regulatory recommendations on channel arrangements, ongoing equipment standardization and pre-commercial wireless backhaul equipment available for trials in the W-band (92–114 GHz). Both W-band and D-band (130–175 GHz) are untapped high-capacity spectrum resources for the future wireless backhaul demand.

Coexistence in 6–15 GHz

Spectrum is a scarce and very valuable resource. Spectrum sharing and coexistence capabilities are becoming more important than ever due to the demand for more spectrum for different types of wireless broadband use, with technologies such as 5G/6G, Wi-Fi, satellite and wireless backhaul. Opportunities for coexistence in parts of the 6–15 GHz range is the latest hot topic in backhaul spectrum, as shown in Figure 2.

Access to spectrum can be achieved in different ways, such as through the ITU World Radiocommunication Conferences (WRC), regional decisions, or decisions on a per-country basis. Whichever method is pursued, harmonization of the selected frequency bands and technical conditions, ideally on a global or at least a regional basis, is key to unlocking economies of scale and to provide numerous benefits to consumers and enterprises.

Some countries have allocated 5.925–6.425 GHz (lower 6 GHz) for unlicensed use, also known as license-exempt, including Wi-Fi and 5G NR-U (NR in unlicensed spectrum).

A few countries, such as the US, have expanded this allocation up to 7.125 GHz. Although technical conditions have been established with the aim of protecting incumbent wireless backhaul, introducing unlicensed use in a licensed backhaul band raises some concerns. There continues to be debate about whether the backhaul is sufficiently protected in worst-case scenarios. The Electronic Communications Committee (ECC) is also studying the impact of a bursty interference, such as Wi-Fi beacon signals. It remains to be seen what impact the growing use of unlicensed 6 GHz Wi-Fi devices will have on the incumbent licensed wireless backhaul use. And if interference issues arise, how will they be resolved, as unlicensed spectrum is not controlled?

International harmonization

The WRC in 2023 (WRC-23) decided on an international harmonization of the upper 6 GHz spectrum, 6.425–7.125 GHz (or parts thereof), for International Mobile Telecommunications (IMT). This is the generic term used by ITU for mobile systems, such as 5G. The decision had support from countries representing 60 percent of the global population, and more countries are expected to support this at the next WRC in 2027. The intention of identifying a frequency band for IMT is to provide equipment manufacturers with guidance on which spectrum may be made available for mobile services, while leaving the final decision on implementation up to each nation.

WRC-23 also decided on the agenda items for WRC-27. One agenda item is to consider studies on sharing and compatibility and develop technical conditions for the use of IMT, which includes the bands 7.125–8.4 GHz (or parts thereof), and 14.8–15.35 GHz.These bands have a large overlap with the 7, 8 and 15 GHz wireless backhaul bands (see Figure 2). Notably, in addition to the decisions taken at WRC-23, an initiative in the US included 7.125–8.4 GHz in the National Spectrum Strategy to be studied for wireless broadband use. For more comprehensive information on 6G spectrum, see the Ericsson white paper. [1]

Long-range wireless backhaul use

It is interesting to look at wireless backhaul use in the 6–15 GHz bands today, as well as considering future demand. These bands, especially 6–8 GHz, are essential for long-range wireless backhaul due to their superior propagation characteristics for distances from about 20 km to beyond 100 km. These are typically used in rural areas and for connecting them to urban centers.

A global and regional overview of the use of wireless backhaul spectrum can be found in the Ericsson Microwave Outlook 2022, [2] reporting around 10 million transceivers globally.

Figure 3: Wireless backhaul spectrum use in seven countries with public deployment data

Wireless backhaul spectrum use in seven countries with public deployment data

Source: Ericsson (2024)

30%

Of more than 1 million transceivers in seven large countries, 30 percent are below 10 GHz.

National usage of wireless backhaul spectrum

Some countries have public data on wireless backhaul installations, which can be used for a deeper analysis. Figure 3 shows national usage of wireless backhaul spectrum in seven large countries around the world. The size of each circle represents the installed base of transceivers, with in total more than 1 million for these countries. There are large variations in how much each backhaul band is used in different locations, countries and regions. Many of the bands are used in most countries, but the relative use varies. For example, 30 percent of all transceivers in Figure 3 are used for the essential long-range bands in 6–8 GHz, but it varies per country from around 10 percent to more than 60 percent. This depends on the local demand and historic decisions on what is the most valuable use of a frequency band in each region and country. One example is the 11 GHz band, (10.7–11.7 GHz), which some countries have prioritized for extensive wireless backhaul use, while others have prioritized it for uncoordinated satellite earth station (receiver) use with no, or very restricted, wireless backhaul use.

Figure 4 shows a useful geographical overview of the wireless backhaul deployments for the bands in each of these countries. Each red line corresponds to a point-to-point wireless backhaul link. The 6–8 GHz bands, or parts thereof, are used for long-range wireless backhauling in all parts of these countries, except for the most remote rural areas where there are few people and no terrestrial transport networks. The 10–15 GHz bands are useful for shorter distances and therefore are used closer to urban centers.

Figure 4: Extensive use of 6–8 GHz and 10–15 GHz for long-range wireless backhaul

Extensive use of 6–8 GHz and 10–15 GHz for long-range wireless backhaul

Source: Ericsson (2024)

Importance of coexistence

How much these bands are used also depends on the penetration of fiber transport networks in these countries and areas. Even if there are many advantages of fiber transport, it is simply too costly and not sufficiently reliable to be used in all locations.

Spectrum in the 6 GHz band, as well as 7–15 GHz bands, is being considered by national regulators for the future growth of mobile networks. Notably, mobile systems are less challenging in terms of coexistence with incumbent wireless backhaul, which is in fixed known locations, uses passive antennas with very narrow beamwidths, and features such as automatic transmit power control (ATPC) that further reduce any interference. The licensed nature of mobile and backhaul allows for coordination, including geographical coordination.

Conclusion

Wireless backhaul is a somewhat “unsung hero” that has helped to enable the current global communication networks. It is important to carefully consider the extensive and essential use of long-range wireless backhaul in these bands – today, as well as tomorrow. Introducing unlicensed use raises many concerns, while there are opportunities for coexistence with licensed mobile systems. It is expected that the most valuable use of a frequency band will also, in the future, vary in different regions, countries and locations.

Ericsson Microwave Outlook report 2024

The Ericsson Microwave Outlook report, published annually, contains the latest trends, developments and insights into wireless backhaul industry.

Download the report

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