Important steps are being made towards increasing the range of spectrum options for 5G in the UK, gradually progressing to the stage where 5G will be able to serve its full range of potential use cases and realise its full performance potential. A reminder that key spectrum identified for 5G in the UK and EU is as follows:
- 700 MHz (band n28—within the 5G “low-band”), FDD with a maximum of 20 MHz uplink/downlink paired per carrier.
- Provides a core “coverage layer”, useful for some IoT and a wide range of low-rate applications given the coverage/reliability/availability implied. It is nevertheless very low capacity due to its low bandwidth, and is not able to optimally take advantage of many of the benefits of 5G due to that bandwidth, and being low frequency (long wavelength) and FDD.
- 3.4-3.8 GHz (the vast majority of band n78—within the 5G “mid-band”), TDD with a maximum of 100 MHz per carrier.
- Higher capacity due to the availability of the FR1 maximum carrier bandwidth of 100 MHz, and able to serve higher data rates (of up to near 1 Gbps—and higher under some MIMO scenarios) and many 5G use cases accordingly. Also, due to its TDD duplexing and the frequency, able to better serve technologies increasingly prevalent or made possible through 5G—such as MIMO/mMIMO. This is through using the principles of reciprocity to set parameters, and shorter wavelengths meaning more antenna elements are possible in a given antenna space. TDD also leads to better downlink/uplink resource optimisation through allocating more/less time to downlink/uplink as needed based on downlink/uplink traffic loads and noting that 5G can (ultimately) even change this dynamically, whereas FDD is fixed. Slightly lower latency is possible through being able to use a greater subcarrier spacing (hence, shorter symbols) in this band, among other benefits.
- 24.25-27.5 GHz (band n258—within the 5G “high-band”), TDD with a maximum of 400 MHz per carrier.
- Only this can achieve the highest 5G capacity and lowest latency, through having the greatest bandwidth available (400 MHz, the maximum in FR2) and allowing the greatest subcarrier spacing hence shortest symbols.
Learn more here.
The current deployments for 5G in the UK and much of the world have been using the 3.4-3.6 GHz sub-part of the mid-band spectrum, or more recently up to 3.68 GHz in the UK including the 3.605-3.68 GHz spectrum of Three UK (extended downwards to 3.6 GHz recently by Ofcom, permitting Three to use a contiguous 100 MHz at 3.58-3.68 GHz including the 3.58-3.6 GHz spectrum it also owns). Such deployments can only achieve a small sub-part of what 5G might ultimately be capable of, and coverage using such deployments will be limited—including to indoor locations. However, recent developments taking place both in the UK and in the international arena are improving the situation. In addition to the remaining upper 120 MHz (3.68-3.8 GHz) of the 3.4-3.8 GHz range, Ofcom is due to auction the 700 MHz spectrum this Spring. This 700 MHz “coverage layer” in the UK has 30 MHz available paired in downlink and uplink, plus an additional 20 MHz of “supplemental downlink” spectrum in the duplexing gap. In terms of raw averages, the paired spectrum is only an average of 7.5 MHz downlink/uplink per operator, and the supplemental downlink is only an average of 5 MHz per operator. Given the 5G NR Band n28 (in which this is) minimum carrier bandwidth of 5 MHz, the minimum allocation and indeed the lot size will be 5 MHz for the supplemental downlink spectrum, and 2x 5 MHz (paired uplink/downlink) for the conventional paired spectrum. Other carrier sizes possible include 10 MHz, 15 MHz and 20 MHz, where it is of course possible to combine contiguous 5 MHz lots to be able to use larger carriers. The essence of this is that, assuming that each operator will have to have at least some of this vital spectrum the bandwidth per operator is likely to be 5 or 10 MHz, or 15 MHz in the extreme (i.e., comparable to that seen for 4G/LTE in the UK), and performance of deployments based on such spectrum will therefore be only somewhat better than what is already achieved in 4G/LTE. This is noting that at through such frequencies/bandwidths and FDD spectrum, many of the capacity-related benefits of 5G don’t apply, and that as a baseline 5G is after all—irrespective of higher-order modulation and coding schemes—just an OFDM waveform (like 4G/LTE).
Interestingly, the lot size is also 5 MHz for the 3.68-3.8 GHz auction—despite the minimum bandwidth in this case being 10 MHz. This lot size allows for 15 MHz and 25 MHz carriers without wastage, as are possible in 5G NR bands n78 and n77. Moreover, for the 3.68-3.8 GHz auction, Ofcom is including at the end of this auction process a negotiation phase, where operators will negotiate to defragment the spectrum. This is important, as all winners of the 3.68-3.8 GHz auction would have two non-contiguous chunks of spectrum as a result, and therefore would require two radios and aggregation support (at the base station, and in terminals) to be able to use that spectrum. Of course, Three UK already have 100 MHz contiguous spectrum, as mentioned previously. They do also have 20 MHz of non-contiguous spectrum lower in the band, at 3.48-3.5 GHz, which might play a part in the negotiation, however, Three UK would benefit little from the defragmentation as the 100 MHz it has is already the maximum carrier bandwidth for 5G in this band. Other operators would benefit greatly from (indeed, even need) such a defragmentation process.
The end result of this and the 5G spectrum changes in the UK that will result, applicable at least for the medium-term future and not considering possible spectrum refarming by operators for 5G, is:
- A good 5G coverage will eventually be achieved—perhaps as early as next year. However, that will be with very limited data rates, not much in advance of what can already be achieved with 4G/LTE.
- Will be good for applications such as IoT, reliability and availability of service, low-capacity data (e.g., web browsing, HD streaming), etc.
- Excellent 5G performance, around 1 Gbps or perhaps more in some cases, will be possible—again, perhaps as early as next year. However, that is likely to be only the case in a smaller subset of areas of the UK, e.g., in big cities.
- Will be good for high-capacity applications, such as VR/AR, 4K/8K streaming, fixed wireless access, etc.
- Some latency benefits will be achieved.
More information on the auction/award, including its terms and strategy, can be obtained here:
Another important relatively-recent (November 2019) development internationally is the ITU World Radiocommunication Conference (WRC) 2019 deciding (affirming, in many cases) the mm-wave bands for 5G (see here). We use the term “affirming”, as some of the bands were already used and equipment therefore available supporting them in some countries, and the results of such events are often also a foregone conclusion based on the proposals that various regulatory regional groupings—such as the European Conference of Postal and Telecommunications Administrations (CEPT) to which the UK participates—bring to them. WRC 2019 has affirmed the 24.25-27.5 GHz band—which is the most prominent of the mm-wave bands applicable in the UK/EU case—as well as allocating numerous other bands for 5G. It will likely be some considerable time before such spectrum is widely used in the UK, however, because a detailed consultation process, and likely an auction and actual deployment must be undertaken—noting that due to the nature of such bands deployments will have to be at a much higher density. Indeed, to the best of our knowledge, only Telecom Italia Mobile (TIM) in Italy are far advanced in terms of actually using that spectrum in Europe/Scandinavia, although others—such as Telenor in Norway—have undertaken extensive trials with it.
Also highly-relevant to the 5G context—and indeed aimed partly at 5G by Ofcom—are developments and approaches around shared spectrum in the UK. Specifically, through the Shared Spectrum Access bands localised 5G deployments can be undertaken, or indeed 5G networks or other capabilities in general might be bolstered through such local licenses. This approach and the bands were consulted and later affirmed through an Ofcom Statement back in July 2019 (see here). Generally, two options are available: (i) “medium power” licensing of a single base station, or “low power” licensing of an area of radius 50m in which any number of low power base stations can be deployed. “Low power” is defined as 24 dBm EIRP per carrier per sector for carriers ≤ 20 MHz (or 18 dBm / 5 MHz per sector for carriers > 20 MHz), and “medium power” is defined as 42 dBm (approximately 16 Watts) EIRP per carrier per sector for carriers ≤ 20 MHz (or 36 dBm / 5 MHz per sector for carriers > 20 MHz). For a 100 MHz carrier, this equates to 49 dBm (approximately 80 Watts) EIRP, which is a very significant power. License-exempt terminals are allowed if they are associated with one of the deployed base stations, operating at a maximum transmission power of 23 dBm TRP (23 dBm EIRP for fixed/installed terminals). Various other constraints apply; please refer to through the abovementioned Ofcom Statement for detail on these. Although the way forward for such an approach was affirmed through this statement back in July last year, only in December was it made possible to actually use the concept and spectrum through the shared access license application process.
The bands of interest to 5G here are:
- 8-4.2 GHz (upper part of 5G NR band n77—within the 5G “mid-band”):
- Maximum bandwidth 100 MHz—i.e., same as maximum bandwidth for 5G at this frequency—TDD.
- Might be particularly useful for high-capacity private networks, including industrial networks (e.g., Industry 4.0) in some scenarios. Indoor and outdoor usage although constraints do apply.
- Cost is £80 per 10 MHz per base station or area (for “medium power” or “low power” respectively—as described earlier in this post).
- 24.25-26.5 GHz (lower part of 5G NR band n258—within the 5G “high-band”):
- Maximum bandwidth in this case 200 MHz—i.e., half the maximum bandwidth of 5G in FR2—TDD.
- Also applicable to high-rate private networks. Useful to extreme high-capacity, and also very low-latency scenarios. Limited to indoor use only.
- Cost is £320 fixed irrespective of bandwidth per base station or area (for “medium power” or “low power” respectively—as described earlier in this post).
- 2.39-2.4 GHz (a small part of 5G NR band n40—within the 5G “mid-band”):
- 10 MHz only, so low capacity—TDD.
- Suitable for low-rate private networks, although with considerably better propagation/coverage than the alternatives above.
- Currently limited to indoor use only, although that could change.
- Cost is £80 per base station or area (for “medium power” or “low power” respectively—as defined earlier in this post).
It must be emphasised that in addition to all of the above, operator spectrum refarming can and likely will occur opening up more spectrum to 5G. This is an unknown that will perhaps significantly affect the analysis above. In particular, it is noted that this has already taken place extensively in the US, for example, given challenges around access to the key 3.5 GHz spectrum in early 5G deployments there. Examples of such refarming—or dual use with 4G/LTE—include 2.5 GHz TDD 5G NR Band n41 spectrum by Sprint (T-Mobile), and 600 MHz (T-Mobile) and 800 MHz (Verizon) FDD Bands n71 and n5 respectively. Importantly, the 3GPP has already defined a large number of legacy 4G/LTE, 3G/UMTS and other bands also as 5G NR bands, setting the framework for such refarming to 5G usage.
Much has been publicised about “5G” network launches in the UK and internationally. However, those networks can only achieve a pale shadow of what 5G is, largely due to their use of a very limited subset of the complete range of 5G spectrum bands. Big steps forward in the UK will be made this year and into 2021 with the auctioning and deployment of the 700 MHz and rest of the 3.4-3.8 GHz spectrum, and perhaps in late 2021 or 2022 5G will be “complete” in the UK through the eventual allocation and use of mm-wave. Watch this space!
Useful Reference Graphics: