Microwave Journal

Multi-gigabit Connectivity at 70, 80 and 90 GHz

July 6, 2005

In October 2003, the FCC announced that the frequency bands from 71 to 76 GHz, 81 to 86 GHz and 92 to 95 GHz were available for wireless applications. FCC chairman Michael Powell heralded the ruling as opening a “new frontier” in commercial services and products for the American people. The allocation provides the opportunity for a broad range of new products and services, including high speed, point-to-point wireless local area networks and broadband Internet access at gigabit data rates and beyond.

The significance of the 70, 80 and 90 GHz allocations cannot be overstated. Collectively referred to as E-band, these three allocations are the highest ever licensed by the FCC. Together, the nearly 13 GHz of allocated spectrum represents more than all previously existing commercial wireless spectrum combined. The FCC ruling also permits a novel licensing scheme, allowing cheap and fast allocations to prospective users. All this was achieved at unprecedented speed, from initial FCC petition to formal release of the rules in barely more than two years.

Historical Background

In September 2001, Loea Corp., a spin-off of military research contractor Trex Enterprises, submitted a formal petition to the FCC requesting that spectrum at 71 to 76 GHz and 81 to 86 GHz be opened up for commercial wireless communications. At that time, these frequency bands were reserved for government and military operations, as well as some satellite and radio astronomy applications. The filing quickly received strong support from the wireless and networking community. The Wireless Communications Association (WCA), who was pushing its own 60+ GHz spectrum development initiative, quickly threw its weight behind the petition, as did Cisco and a number of leaders in the wireless communications industry.

Collaboratively, a full proposal for band use and a novel-licensing scheme was developed and presented to the FCC. Based on this proposal, the FCC quickly drafted a set of technical rules for licensed operation in the 71 to 76 and 81 to 86 GHz bands, adding some spectrum between 92 and 95 GHz for unlicensed use. On October 16, 2003, barely two years after Loea’s original petition, the FCC wrote the new rules into law, opening up 12.9 GHz of new spectrum under Part 101 regulations.

Why 70, 80 and 90 GHz?

Of the three frequency bands opened up, the 70 and 80 GHz bands are widely viewed as of most interest. Designed to co-exist together, the 71 to 76 GHz and 81 to 86 GHz allocations allow 5 GHz of transmission bandwidth, enough to pass a gigabit of data even with a relatively simple AM modulation scheme. With a more spectrally efficient modulation scheme such as 4-level FSK, full duplex data rates of 10 Gbps (OC-192 or 10GigE) can be reached. With direct data conversion and low cost diplexers, relatively simple and thus cost efficient radio architectures can be realized.

The 92 to 95 GHz allocation on the other hand is far more difficult to work with. Segmented into unequal portions and separated by a narrow 100 MHz exclusion band at 94.0 to 94.1 GHz, the frequency allocation forces lower data throughputs and more complicated filtering schemes, both a deterrent to low cost commercial use.

Propagation characteristics at E-band allow for transmission in excess of a kilometer with carrier class performance (see Figure 1). At 70 and 80 GHz, the atmospheric attenuation is not too much worse than at the popular microwave bands of 18 to 38 GHz. Atmospheric absorption at E-band is much less than at 60 GHz, where oxygen absorption causes high link attenuation, and significantly better than at optical frequencies, where free-space optic systems can experience 200 dB/km attenuation in thick fog. A comparison of typical 70/80 GHz radio performance against main competing technologies is illustrated in Table 1.

Fig. 1 Link distance for 99.999 percent availability with historical regional weather variations (20 m W transmit power and 2 ft. antenna) (courtesy of Loea Corp.).

E-licensing

At E-band, the FCC allows a novel “E-licensing” system for link deployment. Under the traditional auction-based system, the highest bidder (typically a behemoth service provider or a highly debt-leveraged start-up) would be awarded a license to solely control a specific frequency band in a defined geographic area. At 70, 80 and 90 GHz, however, any applicant — large service providers such as Sprint or Verizon, end-users such as enterprises, government and military entities, or even individual hardware providers — simply completes an on-line link registration defining the end points of the requested links and pays a small fee. Once coordinated and approved, the successful applicant is permitted to operate along with any other coordinated and approved users in the same frequency and location. FCC chairman Michael Powell has hailed this new concept as revolutionary as increasing competition and reducing bureaucratic slowdown, and suggested a similar approach be adopted in all future rulemakings.

Still in its infancy, only a handful of license applications have been sought and granted, so it is too early to tell whether the new scheme has been successful. However, the promise of this new procedure is very compelling.

System Providers

The two leading proponents of the 70 and 80 GHz bands are Loea Corp. and Gigabeam Corp. Based in Hawaii, Loea led the push for the release of the E-band frequencies, and has a growing installed base of commercial products. Loea’s most public installation was back in 2003, when millions of Super Bowl XXXVII viewers watched live action shots transmitted through a Loea 70/80 GHz Virtual Fiber link. Traditional elevated shots from a blimp were not permitted due to security restrictions in the airspace above San Diego’s Qualcomm Stadium. Loea’s wireless Super Bowl link operated at full 720P HDTV output speed, equivalent to 1.485 Gbps, over a 0.5 mile distance.

A second company starting to receive a lot of focus is GigaBeam. Based in Virginia, GigaBeam has a rich wireless pedigree, with the founders being the driving force behind the original FCC approval. Lou Slaughter, CEO and co-founder, commented, “In less than a year since its founding, GigaBeam underwent an innovative Venture Public Offering taking the company public without requiring a round of venture capital funding.” GigaBeam recently received a purchase order to install 20 links across New York City. “The network includes links to Trump properties to provide the triple play of high speed voice, data and video to residents,” Slaughter added. As yet, no high data rate 94 GHz wireless products have hit the marketplace.

The Future?

In little more than three years, a whole new industry has been born. The prospects of 10 Gbps data rate, low cost wireless communication systems over distances of a mile or more, are now a reality. Systems will become cheap and quick to license and inexpensive to install and maintain. “70/80 GHz systems are now a serious alternative to fiber,” says Loea’s CEO, Dan Scharre. “With volume shipments and dropping price points, applications beyond LAN extensions will be realized, opening up such new applications as high definition video-on-demand and wide-area data storage.”

Despite this promise, there are still only a few players in this area. The market is restricted in that the rules apply only to the US. No similar bands are yet available internationally. Currently, the FCC rules are being rewritten to tweak some antenna size and output power restrictions that are holding back the realization of low cost architectures. Once this is complete, watch out for the exciting and rapid advance of this fascinating industry segment.

Jonathan Wells received his MBA degree from Massey University, New Zealand, where he specialized in strategic R&D management, and his PhD degree from Bath University, UK, for his work on 94 GHz systems. He is a wireless technology consultant based in San Jose, CA, specializing in strategic marketing and business development of advanced wireless products. He has held a number of business development, marketing and technology management roles, including director of RF engineering for Stratex Networks and director of wideband products for adaptive broadband. He is a senior member of the IEEE, a charter engineer in Europe and is active on the WCA 60+ GHz spectrum development committee. He can be reached at (925) 200 5124 or via e-mail at jonathan@jonathan-wells.com.