Chasing Wi-Fi Speed, Coverage, and Compatibility

The GSM association reports that 4.7 billion subscribers used mobile wireless during 2015 and 1 billion used the high speed 4G mobile wireless technology. Video is soaking up whatever spectrum capacity operators make available, and the demand for bandwidth will continue growing. With 5G technology still under development and years away from widespread deployment, mobile operators are working hard to squeeze capacity out of the spectrum they have. Some aspects of 5G wireless network buildout require large investments and operators are reluctant to make those without business justification.

Wi-Fi is an important part of the communications mix today and will continue to be under 5G. It links laptops, tablets, and miscellaneous devices to the Internet and to each other within unlicensed spectrum. Wi-Fi handles the back and forth communications over relatively short distances. Today’s Wi-Fi can become congested, and without a daisy chain of base-stations, it covers only a limited geographic area, e.g. a retail store.

Another important technology is Long Term Evolution (LTE). In the US, this is the dominant protocol used by smart phones for connections back to the cell tower. Mobile wireless cells typically have a cell radius of 2 kilometers (km) (dense urban) to 14 km (rural). LTE needs spectrum that propagates at least as far as cellular radiuses (generally in the 2 GHz to 3 GHz range). Clearly Wi-Fi and LTE are not direct substitutes since they have different characteristics and serve different purposes.

Today’s unlicensed spectrum for Wi-Fi will not keep pace with consumer needs.  Steady increases in demand for spectrum are due to our appetite for video and the steady rise in connections among sensors, processors, and actuator devices that we call the Internet of Things.  Both unlicensed and licensed swaths of spectrum in the 3.5 GHz and 5 GHz bands (and lower bands for LTE) are necessary to make 5G a reality.

Today’s Wi-Fi standards are 802.11/a/b/g/n. In a tentative step toward 5G technologies, the next standard for Wi-Fi will be 802.11ad. Routers based in the 802.11ad standard are expected to be available in late 2016. If they operate in the 3.5 GHz and 5 GHz bands, they will support 5 gigabits per second transmission speed (like fiber optic) but their reach is limited to the same room as the router. An 802.11ax standard will be available in 2 years. It will operate at somewhat slower speeds but with a reach that covers shopping malls and multi-unit housing.

To reduce the chance of two Wi-Fi devices beginning transmission at the same instant, the Wi-Fi standards use a scheduling protocol of “listen before talk” (LBT) and they further reduce the risk of clashing by assigning random “backoff” intervals before communicating. The technique is very successful.

The mobile wireless standards of 3G LTE, 4G LTE and soon 5G LTE use a manager that schedules when each device can talk. A concerted effort is underway to make the LTE’s scheduling compatible with Wi-Fi’s LBT protocol. When that is accomplished, LTE and Wi-Fi will be able to co-exist in the same spectrum, expanding the spectrum in which mobile wireless can operate, and probably speeding communications between Wi-Fi coverage areas.

An LTE version called LTE-U is already compatible but it does not honor the LBT principle. An LTE version called LTE-Licensed Assisted Access (LTE-LAA) is under development, and it uses LBT. Another hybrid called MultiFire is under development by a team from Qualcomm, Intel, Nokia and others. For existing government systems, cellular systems, and unlicensed systems to co-exist at 3.5 GHz, a complex, database-driven Spectrum Access System (SAS) will arbitrate access. There is widespread interest in expanding access to the usable Wi-Fi spectrum, but mobile operators are wary of being forced to make the large investments under regulations that preclude a chance to compete on equal footing with others who ride their networks.

Today, the smart phone traffic that telecom operators carry comes largely from TIP’s non-telecom members; 15% from Facebook and 20% from YouTube. At the same time, those “non-telecom” businesses compete directly against telecom operators for text messaging and phone call revenues without any of the regulatory burdens imposed on the telecom operators. The operators do not want that inequity continued into the 5G era.

Facebook, Intel Deutsche Telecom, Nokia, and others formed the “Telecom Infra Project” (TIP) to make it easier and less costly to connect people in places that don’t have cellular service, from urban basements to rural villages. They are producing design recommendations for 5G networks. Some of their aims are related to less well developed parts of the globe, but there is much to be done here in the US.

Potential new mobile wireless competitors are lining up to acquire spectrum.  Charter, Comcast, Dish, Columbia Capital and a host of discount-eligible entities will participate on the upcoming 600MHz auction. Auctions of higher frequency blocks of spectrum will draw even more candidates for bidding.   Aside from those well-heeled large entities, regulators give discounts off amounts bid by smaller entities, notionally to get small players into mobile wireless.

Fueled by market demand, mobile wireless and Wi-Fi technical developments will continue to be sources of innovation and potential growth for the US economy. Along the way we can expect displays of fierce competition as industries and countries contend for their place in 5G.

FacebooktwitterredditlinkedinFacebooktwitterredditlinkedin