Interesting news coming out of the US – The FCC is announcing new rules for high frequency (over 24 GHz) wireless broadband operations and opening almost 11 GHz of high-frequency spectrum for mobile and fixed use wireless broadband.
Specifically, some of this is being made available in the licensed bands: 28 GHz (27.5-28.35 GHz), 37 GHz (37-38.6 GHz), and 39 GHz (38.6-40 GHz) bands, but of particular relevance is a new unlicensed band at 64- 71 GHz – which effectively extends the unlicensed 60GHz band (which 802.11ad broadband, aka WiGig, uses).
The release also states towards the end that: “The FNPRM seeks to apply the flexible use service and technical rules adopted today to another 18 GHz of spectrum encompassing 8 additional high-frequency bands, and seeks comment on a variety of other issues, including refinements to the performance requirements and mobile spectrum holdings policies, and the sharing framework adopted for the 37-37.6 GHz band.”
This move makes the US the first country to have these bands available. It will be interesting to see who follows suit, especially given that the 60GHz band varies from country to country. The US gives 7 GHz between 57 and 64 GHz, China just 5 GHz, and the EU has 9 GHz of bandwidth.
But adding this new unlicensed spectrum also opens an engineering challenge – one that was also seen and solved for WiGig, and will need to be adapted / evolved if the industry is to manage and transmit data at these frequencies.
If we look at just the 60GHz band, WiGig requires a complex digital sample rate of ~2x bandwidth or 3.52 GHz, an order of magnitude higher than current wireless standards. The key challenge is finding an efficient parallel architecture that can cope with it.
As we move into ever higher frequencies, the DSP processing required will be even more intense. Many SDR wireless platforms provide provision for a wide spectrum of baseband standards to recoup the cost of the technology development. However, this strategy cannot be applied here due to the substantial DSP processing implicit in the high sample rates and hence any inefficiencies will be multiplied, assuming it can even scale to that performance. Moreover, with recent extensions of the 802.11ad standard to include 64QAM and the move to add yet more complex features for the 802.11ay 10Gbps+ standard we expect that numerous further PHY enhancements will be required to keep with WiGig and ultimately 5G radio interfaces which will emerge to exploit this extended millimetre wave band.
This means companies like Broadcom, Intel and Qualcomm, who have already developed 60GHz technology and the ability to cope with the digital sample rates, will have an advantage and IP developers, like ourselves, will become an essential part of helping those without their R&D budgets to keep up.
In the release, the FCC says “these rules set a strong foundation for the rapid advancement to next-generation 5G networks and technologies in the United States”, with the high-frequency spectrum supporting “innovative new uses enabled by fiber-fast wireless speeds and extremely low latency.”
One of the key elements that this gives is clarity for innovators like ourselves and this can only be a good thing.