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Understanding 5G frequency spectrum bands
Over the last few years, there has been an increase in connected devices and a growing trend towards interactive media. High-band spectrum provides the anticipated leap in data speed, capacity, quality and low latency promised by 5G.
Introduction to the largest frequency spectrum range ever
Over the last few years, there has been a growing trend towards interactive media such as video programming, and generating more immersive experiences in the form of Virtual Reality (VR) and Augmented Reality (AR). This trend will bring about great challenges and expectations. This places incredible amounts of trust on mobile systems as users will require large amounts of data in order to gain the amount of information required at the same time.
These requirements do not only affect the capacity of air interfaces, but also impose an architectural re-design of transport networks and cloud systems to form a more distributed topology that extends to the converged mobile core, with storage and computing being spread all the way to the wireless edge.
Second, is the demand of the number of devices within the IoT world. 5G will play an instrumental role in ensuring universal connectivity for a myriad of devices which have very different characteristics, most of all not requiring high performance connection demand in terms of high throughput and short latency, but instead deep indoor coverage and low power consumption.
Indeed, prior system designs have not delivered the required IoT capabilities. This provides an opportunity which 5G may be able to capitalize on.
5G technology promises to combine and manage IoT where technically a very large number of devices require very small resources, low performance and Ultra Broadband.
The role of different frequency portions: use cases and applications
Low-band spectrum is currently being used for 2G, 3G and 4G services for voice, MBB services and Internet of Things (IoT). Newly allocated spectrum for mobile networks include the 600 MHz and 700 MHz bands. These bands are ideal for wide-area and outside-in coverage as well as for deep indoor coverage, typically required for eMBB and voice services, but also required for M2M type of communication from outside to inside the building, even in deep basements.
Mid-band spectrum is currently used for 2G, 3G and 4G services. New spectrum has been widely allocated in the 3.5 GHz band, with more spectrum planned to be made available in the 1.5 GHz (L-band) and 5 GHz (unlicensed) bands. Bandwidths of 50 megahertz to 100 megahertz per network will enable high-capacity and low-latency networks ideal for 5G use cases such as enhanced MBB (eMBB) and Ultra Reliable Low Latency Communications (URLLC), for critical IoT applications. With better wide- area and indoor coverage than high-band spectrum, the mid-band spectrum is an optimal compromise between coverage, quality, throughput, capacity and latency. Combining the mid-band spectrum with low-band spectrum leads to exceptional network improvements in terms of capacity and efficiency.
High-band spectrum clearly provides the anticipated leap in data speed, capacity, quality and low latency promised by 5G. New spectrum bands are typically in the range of 24 GHz to 50 GHz, with contiguous bandwidths of more than 100 megahertz per network. The high-band provides a significant opportunity for very high throughput services for xMBB, localized deployments and low latency use cases, e.g. industrial IoT, venues, etc, both for indoor and outdoor deployments. Fixed wireless access (FWA) will also benefit from these higher bands in terms of capacity. As the coverage range is very limited (hundred-meter magnitude), for wider-area coverage, combinations with low-band and mid-band are essential.
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Each spectrum band represents unique properties, meaning there are diverse opportunities for a service provider to balance between throughput, coverage, quality and latency, as well as reliability and spectral efficiency. Availability of spectrum will vary globally between countries and regions, both in terms of bands, amounts and timing. The 5G standards also include end-to-end network slicing and mobile edge computing which are vital in supporting the needs of industry vertical sectors. In particular, network slicing will allow operators to create virtual sub-network slices with tailored features for specific types of user or usage requirements. Slicing, among the other characteristics, includes spectrum bands and channels choices. For example, ultra-low latency and high availability slices are a good fit for automated manufacturing, connected cars and remote surgery. Contrastingly, IoT networks with vast numbers of sensors and devices like streaming video cameras can be allocated a slice that is tailored for uplink heavy communications.
Some verticals depend on ultra-low latency capabilities while others need superfast download speeds. Some need highly localized connectivity (e.g. small cells for a factory) while others will need nationwide connectivity (e.g. a vast macro network to support sensors for utility companies). Each of these examples need different spectrum and network resources.
Ultra-low latency services and high-speed broadband services need different spectrum bands, as their radio resource requirements are incompatible. Similarly, high-capacity, localized services better suit capacity bands (i.e. above 1 GHz) whereas nationwide services benefit from coverage bands (i.e. sub-1GHz). Mobile operators are the best placed to provide the wide variety of services envisaged, including private networks with leased spectrum in cases where that is needed due to the specific requirements from verticals. If we consider the bandwidth and penetration requirement, a row subdivision of use cases per frequency spectrum portion can be outlined as follows.
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Low-band use cases: small amounts of data need to be exchanged from a large number of distributed devices to the network and vice versa. Low-band is useful in covering large spaces (rural areas) and to penetrate deep indoor (basements). Low latency can be achieved also in this part of the spectrum with ad-hoc slicing strategies.
Mid-band use cases: this band category is the perfect balance between large bandwidth (500Mbps to 1-2Gbps) and coverage of few tenths meters per cell. For the indoor cases, there should be a particular attention to repeat the signal from outdoor to indoor. A trade-off between throughput and latency can be achieved by network slicing.
High-band use cases: this band ensures the support of all those cases requiring a very high data rate especially in media and entertainment market. The user must be close to the access point (few meters). Usually the use cases are those requiring maximum speed, but a trade-off between throughput and latency can be achieved by network slicing, also in this frequency range.
What is the regulatory status and the evolution expected?
Regulators around the world are actively developing their 5G spectrum plans and some have completed the first assignments. The key focus is on new mobile bands including spectrum in the 3.5 GHz range (i.e. 3.3-3.8 GHz) that has been assigned in numerous countries. However, other bands are also being considered. For example:
• Several countries plan to use spectrum in the 4.5-5 GHz range for 5G, including China and Japan;
• A growing number of countries are considering the 3.8- 4.2 GHz5 range, and 5925/6425 – 7125 MHz;
• There is also interest in assigning the 2.3 GHz and 2.5/2.6 GHz bands for 5G, replacing the current 4G technology.
The fastest 5G speeds actually depend on the identification of new millimeter wave bands above 24 GHz. These have been largely agreed at WRC-19, which is assessing a range of bands from 24.25-86 GHz. At the other end of the spectrum, Europe has prioritized the 700 MHz band for wide area 5G deployments and the US has already licensed the 600 MHz band. The new 5G bands that regulators are making available will also affect how networks are deployed. First 5G mid-bands (e.g. 3.5 GHz) and millimeter wave bands (e.g. 26 GHz and 28 GHz) serves dense 5G small cell networks in urban hotspots where additional capacity is vital. However, these frequency bands can also suit macro cells for wider area coverage – including fixed wireless access – using beamforming. These technological, enhancement means that the 3.5 GHz band can provide the same coverage, and use the same cell sites, as the current 2.6 GHz and 1800 MHz mobile bands used in the 4G coverage.
Spectrum allocation status in Europe
The first allocated bands are the low and mid. The majority of European Countries have already assigned those frequencies or have planned to do so in the first Half of 2020. The higher bands allocation procedure is still ongoing for most of the countries. Italy is the first country, where all spectrum ranges have already been allocated.
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