Spectrum explained
On 15 January 2021, the U.S. Federal Communications Commission (FCC) announced the conclusion of the so-called ‘clock phase’ of the U.S. C-Band auction for operating licences in the frequency range 3.7 - 3.98 GHz (280 MHz bandwidth).
Based on an accelerated clearing schedule, 100 MHz of the auctioned C-Band spectrum will be cleared in 46 of the top U.S. markets by 5 December 2021. By 5 December 2023, the remaining 180 MHz in these same 46 markets, as well as the full 280 MHz in the other markets will be cleared for use by 5G services. It is anticipated that the rollout of Communications Service Providers (CSP) networks in the C-Band will start in the coming months in 2021 in the initial 100 MHz and continue as the additional 180 MHz of spectrum is made available in 2022 and 2023.
But what is ‘C-Band’ and where does it fit into the wider topic of spectrum bands?
The range of radio frequencies being allocated to 5G around the world is much broader than to previous generations of mobile technologies. Initial 5G network deployments in the U.S. have been in what the telecommunications industry calls the ‘high-band’ and ‘low-band’. High-band is suited to densely populated cities and locations that generate lots of mobile data traffic and so need higher capacity that the high-band has to offer. However, high-band coverage is generally limited and is affected by the environment in which it is deployed, e.g., the surrounding buildings. By contrast, low-band offers far greater coverage and much better buildings penetration capabilities. For that reason, it is used to provide wide area coverage often to less densely populated rural areas, where there is generally much less traffic but the need to provide coverage remains. Low-band requires fewer base-station sites compared to high-band and is therefore a more cost-effective solution to the coverage needs of areas where the business case might otherwise be challenging. For that reason, low-band is a valuable spectrum asset.
The C-Band spectrum just auctioned in the U.S. falls within the ‘mid-band’ range. This provides a good balance of both capacity and coverage, while also allowing rapid initial 5G rollout and fast introduction of services, vital in all markets.
| Bands | Frequency | Auctions/licensing complete (not an exhaustive list) |
|---|---|---|
| High-band (including millimeter Waves (mmWaves)) | >6 GHz | US, South Korea, Japan, Italy, Finland, Germany, UK, etc. |
| Mid-band (including US 2.5 GHz and C-band) | 2-6 GHz | US, UK, Germany, Italy, South Korea, Japan, China, Finland, France, Saudi Arabia, Qatar, UAE, etc. |
| Low-band (including “newer” bands like 600 MHz & 700 MHz and re-farming of existing bands) | <2 GHz | US, Canada, Austria, Denmark, Finland, France, Germany, Greece, Sweden, etc. |
Understanding spectrum and its uses
The electromagnetic spectrum is a natural finite resource. Humankind has learned to use some of it to its advantage. For example, at low frequencies it is associated with radio waves, at much higher frequencies with visible light, and at extreme frequencies with X-rays, etc.
Radio frequencies are part of the electromagnetic spectrum. As the name suggests, radio frequency spectrum is used for a wide variety of radio communications purposes. e.g., radio, terrestrial and satellite TV, mobile communications, GPS, Wi-Fi, Bluetooth, public safety and radar, etc.
However, as spectrum is finite, the same spectrum band is sometimes shared by several services, e.g. 28 GHz or 3.8 GHz is used by both satellites and 5G services. The diagram below shows just a few of the many uses of spectrum and example operating frequencies, it is not exhaustive.
For CSPs, the available spectrum within a given band is allocated and licensed for use by governmental regulatory authorities.
Mobile network technology takes advantage of the different characteristics within the radio frequency spectrum. Within each band, low- mid- high-, spectrum is allocated to different uses and within a given band there are multiple assignments to the same use. For example, in the high-band, the spectrum around 24 GHz, 26 GHz, 28 GHz and 39 GHz has been allocated to 5G services in several countries. (N.B. this is not an exhaustive list of spectrum bands within the high-band, nor does it imply that all these spectrum bands are available or in use in a given country).
Low-band
Spectrum in the low-band (<2 GHz) has been licenced and used for 5G deployments in US, Canada, European Union countries, etc. Some of the characteristics of this spectrum include:
- Widest coverage
- Limited available bandwidth
- Better able to penetrate buildings
- Wide coverage means fewer base stations need to be deployed and so ideal in rural locations where population is smaller and return on investment might otherwise be challenging.
Mid-band
The mid-band is a term used to describe spectrum in the range 2 GHz to 6 GHz with 5G mid-band deployments tending to be in the range 2 GHz to 4 GHz. Examples include 2.5 GHz and C-band (3.4 - 4.2 GHz range). It provides:
- Comparable coverage to 4G and so can enable the re-use of existing cell-sites to help 5G roll-out and lower costs
- The mid-bands generally have higher available bandwidth than the low-band and so more capacity.
High-band
High-band (>6 GHz), which includes millimeter Wave (mmWave), is licenced in a growing number of countries. The high-band spectrum is of interest because of its characteristics:
- High bandwidth and so high capacity, resulting in extreme mobile broadband capabilities (very fast data rates)
- mmWaves tend to travel shorter distances and do not readily penetrate physical structures such as buildings
- In areas of high network traffic – urban areas, stadia, airports etc., operators can use higher frequency spectrum to deliver the high bandwidth necessary for the best end-experience or application.
How can 5G data rates be higher than other technologies?
In the higher frequency bands, namely the mid- and high-bands, there tends to be more available spectrum than in the low-band. The greater availability of spectrum means that more bandwidth can be allocated and licensed for use by 5G services in given frequency ranges. More bandwidth = more capacity.
For instance, channel bandwidth for a typical 4G network operating in the 2.1 GHz band (low frequency end of mid-band) would be up to 20 MHz, whereas in the mid-band frequencies around 3.5 GHz the bandwidths are up to 100 MHz; in the high-band, say the 28 GHz band, the channel bandwidth could be up to 800 MHz (8 x 100 MHz).
The role of telecommunications equipment vendors
When we make a call or connect to a remote server e.g. to watch a YouTube video, the network transmits and receives signals to and from our phones.
Mobile networks must support a range of frequency bands and radio access technologies (2G/3G/4G…). Telco equipment vendors therefore need to provide an equivalent wide range of radio access network solutions to enable CSPs to build their networks.
Nokia has an industry-leading portfolio range and has pioneered many innovations. Its radio platforms are all 5G ready, meaning that CPSs can re-use existing hardware to support 5G when the time is right. The company also offers solutions that minimize the impact of deploying 5G on existing cell-sites, such as so-called passive active antennas. These modular antenna solutions integrate antennas and radio enabling support for all technologies in a single unit. Additionally, Nokia AirScale portfolio is a single RAN solution, meaning all radio access technologies (2G to 5G) can be supported using the same hardware platforms, which can help significantly lower costs.
Resources
- Nokia product information : Nokia AirScale
- Press release: Nokia’s comprehensive C-Band portfolio ready for 5G build-out in U.S.
- Press release: Nokia can instantly migrate 5 Million legacy 4G radio units to 5G
- Nokia spectrum work: web page
- 5G at 3.5 GHz: The Global Opportunity: Nokia blog
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