The electromagnetic spectrum is the highway over which wireless operates, with multiple lanes capable of carrying traffic at different speeds. Higher frequencies – and thus shorter wavelengths – are able to move more information per unit of time.
Millimeter or extremely high frequency (EHF) waves, occupy the relatively unused portion of the electromagnetic spectrum between 30 GHz and 300 GHz, which offers greater throughput and thus higher overall capacity than the increasingly crowded WiFi bands under 6 GHz.
Historically, millimeter-wave technology has been expensive and difficult to deploy, which has limited it to niche applications like radio astronomy, microwave remote sensing and terrestrial fixed communications.
More recently, however, interest has increased significantly as those two obstacles have been largely overcome. Millimeter wave has evolved into a cost-effective option for meeting the ongoing network capacity challenge faced by enterprises. We expect prices to continue to decline and price/performance to continue to improve, making millimeter-wave solutions a first option for organizations everywhere.
A wide range of outdoor and indoor applications are poised to benefit from this set of technologies.
The traditional fixed point-to-point (P2P) and point to multi-point (P2MP) microwave communications are all right at home in millimeter-wave solutions. Millimeter-wave products offer little additional complexity over microwave-based solutions, and licensing, where required, is almost always handled by the equipment vendor or dealer involved in the sale and installation. Parabolic antennas used in millimeter-wave applications can already be seen in campus and metro-area building-to-building bridges, backhaul and interconnect, links to ISPs, and in ad-hoc applications like telemetry and surveillance.
Wireless PAN and LAN
The IEEE wireless personal area network standard 802.15.3c, the 802.11ad Wi-Fi standard and upcoming 802.11ay standard all specify the 60 GHz band. Given the limited object penetration, range and directionality of millimeter-wave signals, applications here are usually restricted to in-room and open-office settings where line-of-sight can be assured. We expect that general access applications using 802.11ad will become common; chipsets are now making their way to market.
We also expect an increasing variety of outdoor and campus solutions based on these technologies. Many existing microwave and millimeter-wave solutions will evolve over time to inexpensive P2P, P2MP and mesh solutions based on .11ad components, opening the door to even wider deployment opportunities.
Similarly, we expect millimeter-wave components to find their way into a variety of IoT solutions, given that so many of these will be clustered and thus amenable to short-range and mesh approaches.
Despite the potential for multi-gigabit throughput, 802.11ad has seen essentially no real-world uptake to this point. This is due largely to the success of 802.11ac in addressing pent-up and growing demand for WLAN capacity, but also suspicion regarding the behavior and utility of the 60-GHz bands – wariness that is eerily similar to that expressed regarding the 5-GHz bands when 802.11a was initially introduced in 1999.
Given time for users to travel up the experience curve and the attraction of low prices and excellent price/performance, this situation is likely to improve over the next few years.
As 5G is intended in large measure as a replacement for all other wireless WANs and even, where economically feasible, wired broadband services, significant new backhaul capacity will be required. Since 5G will often apply the “small cells” model of denser base-station deployments, millimeter-wave backhaul makes sense even with its inherent range limitations, and even in the unlicensed bands, thanks to narrow beams, directional antennas and the applicability of mesh techniques enabling rapid, cost-effective deployment of backhaul capacity.
More controversial is the application of millimeter waves for 5G mobile subscriber access. Some experiments have indicated that this should be a valuable option in locales with densely packed base stations and appropriate beamsteering capabilities. It’s not clear, however, if the industry will adopt millimeter-wave mobile access on a large scale, and appropriately equipped subscriber devices would be required and, obviously, are not currently on the market.
Millimeter-wave radar is already in use in some automotive applications, and mobile connectivity at these frequencies might be useful in inter-vehicle links for network-based vehicles of the future.