mmWave – Capacity for 5G

The history of mobile technology generations – 1G, 2G, 3G, 4G – is closely linked to frequency bands. Early cellular radio systems were developed in the spectrum below 1 GHz. While subsequent G’s also employ frequencies below 1 GHz, as technologies have evolved, use of higher and higher frequencies has been enabled. This also provides for greater capacity for mobile data, video and Internet services, the current bread-and-butter of the industry. Much of the more recent development has capitalized on the increased capacity available in the range from 1-6 GHz, what is now referred to as mid-band, most notably the 3.4 GHz to 3.8 GHz portion of the C Band.

Three Legged Stool

With 5G, a third set of frequencies will come into play, essentially necessitated by the desire to deliver even higher levels of broadband speed and capacity.

The promise of 5G is to deliver multi-Gbps speeds on mobile. For this, carriers will need to deploy frequencies far beyond what they have now. The “place” to get massive increases in capacity is in the mmWave bands.

In the US, the FCC’s Spectrum Frontiers docket recognizes this and is focused on planning for a mmWave spectrum auction – for licensed and unlicensed frequencies above 24 GHz. Its initial approach for licensed bands was to focus on the 28 GHz LMDS range along with 37 GHz and 39 GHz. These bands represent a total of 3,850 MHz of spectrum capacity, with a couple of wrinkles. First the 28 GHz band is largely licensed already, notably to XO/Nextlink (Verizon), and the 37 GHz range has to be shared with Federal users. There are also a number of incumbents operating in the 39 GHz range, notably Straight Path (also now Verizon).

The FCC had planned to auction licenses in these bands, with a pre-auction screen of 1,250 MHz. In other words, individual licensees would be capped at 1,250 MHz of capacity across the three bands.

Following industry comment, the FCC released a new notice adding two more licensed bands to the docket – 24 GHz and 47 GHz – and changed its view on the need for a spectrum cap. The additional bands add 1,700 MHz of capacity bringing the total capacity to be licensed to 4,950 MHz.

  • The 24 GHz allocation adds 700 MHz (three 200 MHz channels and one 100 MHz channel). This is an important step for the US, as it is essentially the first 700 MHz of the international 26 GHz range. The EC identified 26 GHz as a pioneer band for 5G in late 2016 and thus is expected to play an important role in 5G. A number of vendors have been promoting the idea that a common band plan from 24 up to about 30 GHz would create value and equipment economies (i.e. tuneable across the 26 GHz band including the N.Am. 24 and 28 GHz ranges).
  • The 47.2-48.2 GHz band adds a full 1 GHz of capacity (5 blocks of 200 MHz). Absent incumbents, this band should represent a near-term opportunity for significant capacity.

The FCC Adapting to the Changing Landscape – but are all Hz created equal?

In adding 1,700 MHz to its total, the FCC reasoned that it could drop any pre-auction screen of 1,250 MHz, which would have essentially capped licensees at that level including existing holdings and auction winnings. Instead the FCC will apply a secondary market screen of 1,850 MHz.

This means bidders will not be constrained in auction bidding, but may only be subject to scrutiny post-auction depending on the evolution of the competitive landscape.

Consistent with its earlier ruling, the FCC plans to run the auction with no in-band limits either. This means, for example, that one licensee could buy all of the available capacity in any one of the bands – e.g. all 700 MHz of the 24 GHz range. The FCC’s rationale for this is based on the idea that “any technical differences between these three bands is not sufficient to significantly affect how these spectrum bands might be used”.

Technically, in terms of how the frequencies are used, that may be true. However, the degree to which bands can actually be used in practice is highly dependent on the availability of equipment. And even if there is equipment for all of the bands, there are also significant differences in deployment characteristics. For example, many more transmission sites would be required at 47 GHz compared to 24 GHz, making the 47 GHz frequencies relatively less valuable.

Looking to the Future: mmWave

The story of mmWave is only beginning to unfold. With the promise of significant capacity for 5G, mmWave is a global focus for licensing and technology development. The inter-working of mmWave frequencies with other bands and in handsets is a key consideration for the 5G New Radio specifications finalized on December 21, 2017. In Canada, ISED – the spectrum regulator – has been paralleling US activities.

LYA has extensive background with mmWave frequencies, in the context of development of overall spectrum strategy and business plans, as well as supporting bidders in spectrum license auctions.