LTE-U Versus Wi-Fi: An Electromagnetic Tug-of-War

James Casperite — Technician l, Atlantic City Convention Center

Since the days of our most ancient forebears, the conflict over control of resources and territory has been a constant companion of humankind. So too has this curse of strife followed us into the realm of digital technology and communications, exemplified in the modern battle to claim usage rights over choice communications-friendly sections of the electromagnetic spectrum. As wireless communications of all sorts become more ubiquitous and heavily data-laden, the right of way on the most useful spectra has become a war-worthy treasure. One of the more recent front lines in this conflict has been the offloading of cellular data into frequencies previously used by Wi-Fi, a proposal known as Long-Term Evolution in the Unlicensed Spectrum (LTE-U).

The name itself suggests part of the trickiness of the issue. The wireless frequencies under contention, those in the 5GHz band, are unlicensed by the Federal Communications Commission (FCC) and international regulatory bodies and have become crucial to modern Wi-Fi operation. This light regulatory touch has left 5GHz open to development by other technologies as well, and multiple wireless carriers have invested in expanding the cellular 4G LTE standard into this new territory.  Wi-Fi industry groups such as the Wireless Broadband Alliance and the Wi-Fi Alliance have protested this movement, citing concerns over transmission interference. Wireless trade groups like the Global System for Mobile Communications (GSM) Alliance and the 3rd Generation Partnership Project have fired back with assurances of careful spectrum stewardship and pointing out flaws in their opponents’ projected impact studies. It is definitely in the wireless industries’ best interests to discredit the studies; the results show that in shared test environments, Wi-Fi signals suffer much greater degradation than mobile wireless.

Despite the contentiousness of the issue, the prevailing trend seems to be cooperation rather than conquest. The FCC has remained largely hands-off on the issue of unlicensed spectrum provisioning, suggesting that operators and industry groups find workable solutions amongst themselves. In this spirit, many co-existence framework tests have been completed or are underway, with more planned for the near future. There are common proposals to implement the Listen-Before-Talk (LBT) protocol in this shared space, or an alternate method with similar results, Clear Channel Assessment, ensuring minimal signal collision. Implementation of these protocols is intrinsic in a related format being promoted by some industry groups, known as License Assisted Access. Other proposed mechanisms for LTE-U transmission control are Carrier-Sensing-Adaptive Transmission and Opportunistic Supplementary Downlink, both proposed as alternatives to LBT for mitigating the impact of wireless traffic on Wi-Fi signal fidelity.

Taking the issue one step further is the notion of integration. The main focus of Hotspot 2.0 technology has been Wi-Fi/mobile interoperability, and it is not unreasonable to suggest that both technologies continue to evolve along similar tracks, perhaps someday combining into a single service as the once-separate audio and video communications are well on their way to becoming. With Hotspot 2.0, cellular traffic has already been regularly offloaded to Wi-Fi transmission, and it is virtually assured that this practice will become more commonplace; thus it is in wireless carriers’ best interests to develop new technologies to facilitate integration. Though there is little or no concrete data on the upcoming 5G wireless communication standard, it is the stated intent of industry leaders to fully integrate Wi-Fi technology from the ground up, likely through continued advancement of Hotspot 2.0 and the widespread implementation of 802.11ax. Whichever method is chosen by the industry and the market it serves, it seems likely that the best method of resolving this conflict brought about by technological advancement will, itself, be technological advancement.