One of the most contentious areas of current wireless spectrum policy relates to the 6 Gigahertz (GHz) band, which spans the 1200 Megahertz (MHz) range from 5.925 to 7.125 GHz. In some areas of the world, the band is considered in two sections: the lower part from 5.925 to 6.425 GHz and the upper part from 6.425 to 7.125 GHz.
A number of countries, including the US, South Korea, and Brazil, have already released the entire 6 GHz band for unlicensed use, while others (notably in Europe) have allocated just the lower part. Others have released none for unlicensed use — notably China.
There is much ongoing lobbying and regulatory discussion, especially about the upper part of the band, which is due for consideration at the next World Radiocommunication Congress in November/December 2023.
Three options have been discussed:
- Exclusive licenses: The cellular industry has stated its case for extra frequency allocations in the 6 GHz band, especially for improving 5G in urban areas. It seeks exclusive licenses for large regions or entire countries, which would be available for high-power and outdoor (macro) use
- Unlicensed: The Wi-Fi® industry wants the 6 GHz band to be made license-exempt to enable new, high-bandwidth use cases and overcome congestion and interference in the existing, heavily used 2.4 GHz and 5 GHz unlicensed bands. It also wants to use the extra bandwidth for wider channels and other techniques to enable lower latencies and better reliability, primarily indoors
- Shared licensed: A third option is for a localized, light-touch shared licensing model similar to Citizens Broadband Radio Service (CBRS) in the US, shared access licenses in the UK, or campus licenses in Germany. This is suitable for private 4G/5G enterprise networks, local extra capacity for mobile operators, or perhaps a future licensed-spectrum version of Wi-Fi. There are already other bands for this model, rather than 6 GHz
Importantly, the 6 GHz band is also home to various incumbents, including satellite operators, microwave fixed links (used in sectors such as utility grids), and various government services. The precise allocations and applications vary by country, but they generally mean that high-power, outdoor use of 6 GHz must be carefully localized.
Dissecting the 5G industry’s claims
Disruptive Analysis believes that the arguments advanced by the cellular industry are flawed:
- Forecasts of mobile bandwidth demand, implied value, and mid-band spectrum needs are unrealistic. 5G advocates use an old and arbitrary definition of 5G requirements (continual 100 Mbps downlink and 50 Mbps uplink), which is not reflected in several years of real-world 5G usage and applications. Advocates also fail to specify indoor versus outdoor usage and explain the important differences in network and spectrum requirements for each. Their analysis also contains an unjustified multiplier (“activity factor”), which seems arbitrary and poorly analyzed.
- Alternative options exist for 5G and future 6G expansion besides 6 GHz. There is already discussion about the potential for extra 3 to 5 GHz allocations, plus new 7 to 8 GHz and 12 GHz bands for 5G. Many 6G presentations identify the entire 7 to 24 GHz span as suitable for future cellular use. Also, existing mmWave bands suitable for localized and indoor 5G usage are underutilized.
- The inability of 5G to coexist with 6 GHz incumbent users would entail expensive and complex movement of critical wireless services such as fixed links for utility and broadcast networks. Probable legal and technical challenges could mean many years of litigation, and if won, further years of migration.
- 5G at 6 GHz will struggle with outdoor-to-indoor penetration. Dedicated indoor systems do not yet support the 6 GHz band, especially for multiple mobile network operators’ (MNOs’) networks. The cellular industry itself estimates most cellular use is indoors — as much as 80 percent — and many new applications such as augmented- and virtual-reality (AR/VR), medical monitoring, robotics, gaming, and immersive entertainment are predominantly consumed indoors in residential or industrial/commercial settings. However, indoor 5G systems cannot be economically deployed in more than a tiny fraction of properties, and even that would take many years (likely 10-20 years) to become commonplace.
- Energy inefficiency will become problematic for wide-area 6 GHz 5G. It will likely need very power-hungry multiple-input and multiple-output (MIMO) radios to work with good range on the existing cell grid without new sites. Even then, its poor indoor coverage characteristics would mean much of the energy is wasted.
- It will likely take many years for 6 GHz cellular devices and infrastructure components to be widely available. Existing unlicensed allocations may mean US and South Korean vendors view them as a low priority, while geopolitical concerns have led other countries to eschew Chinese suppliers.
To be clear — ultimately there is likely to be a need for more spectrum to support 5G and future 6G public and private networks in some places with particular needs. However, the case for national or even city-wide 6 GHz exclusive licenses for public MNOs’ “macro” networks is weak. Instead, the focus should be on flexibility for indoor use, localized campus networks for enterprises, or shared-infrastructure neutral hosts. 6 GHz is not essential for these applications.
Wi-Fi’s need for more unlicensed spectrum
Unlicensed 6 GHz is central to Wi-Fi 6E and the forthcoming Wi-Fi 7. It is also likely to be used by other radio local area networks (RLANs) and unlicensed versions of 5G. There are many good arguments for 6 GHz to be released for unlicensed use:
- Capacity is critical. Wi-Fi is hugely popular, forming the backbone of most connectivity in homes, offices, schools, and many commercial spaces, especially indoors. Many devices such as TVs and displays, laptops, home Internet of Things (IoT) products, payment terminals, retail tills, and industrial automation systems are connected via Wi-Fi only. Home-based work and education also rely on Wi-Fi. Some Wi-Fi spaces now suffer from congestion and interference — and availability of expanded spectrum is long overdue. The 6 GHz band is highly suitable for this need.
- Performance and latency. Features in Wi-Fi 6E and Wi-Fi 7 make newer 6 GHz networks better for demanding applications such as industrial controls needing “deterministic” (predictable) timing, immersive/metaverse experiences, robotics, and so on.
- Neutrality. 5G connections can be “offloaded” to Wi-Fi indoors if enough capacity is available via 6 GHz. This also means that all devices can connect to Wi-Fi, making it a “neutral” platform — there is no MNO-specific dependency.
- Unlicensed spectrum fosters innovation. As well as Wi-Fi, other specialized technologies may also emerge to use the band. To use an ecological analogy, an unlicensed 6 GHz band can be expected to drive future network “biodiversity” and reduce the risks of a “5G monoculture.”
- Localized and/or dynamic use of higher-power transmission in unlicensed bands can improve overall efficiency of spectrum use. It can also protect incumbents where they are present, as Wi-Fi is specifically designed for sharing scenarios.
- The low energy requirements of Wi-Fi correlate with its majority indoor use. Unlicensed 6 GHz technologies, running at low power levels, offer the opportunity for cellular networks to offload not just capacity but also energy consumption and CO2 footprint. Wi-Fi 6E and Wi-Fi 7 would connect to a building’s fiber broadband and reduce system-wide energy needs for both the network and user devices.
- Timing is important for many reasons, including the value of likely near-term economic gains compared to uncertain future revenue flows. Wi-Fi 6E equipment using 6 GHz is already in the market in large volumes and is showing real-world benefits in active use. Wi-Fi 7 will be commercially available during 2023, several years ahead of 5G’s best-equivalent Release 17 version. By 2025, unlicensed 6 GHz can be a major contributor to the economic benefits of wireless.
Overall, there are many good arguments for 6 GHz to be released for unlicensed use, with availability of the full 1.2 GHz increasing the upside substantially compared to just the lower part of the band.
Policymakers should forensically consider how wireless networks are likely to be used in the future. A critical aspect is to understand how indoor and outdoor use of wireless connectivity differs, and to insist that any numerical models and forecasts give sufficient granular detail to permit the adoption of good policies. Predictions of mobile traffic at a national or even city level are insufficient and may even be obfuscation, as they often muddle the use of public networks either on private property or for specific localized applications.
As well as aggregated traffic, regulators should also pay attention to the importance of how and where new use cases consume wireless resources, the strategic importance of network diversity and innovation options, energy consumption, and market timing for the use of 6 GHz.
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