Stanford Professor John Cioffi offers some thoughts. WI-Fi’s extraordinary progress needs smart policy to thrive. Wi-Fi physical-layer technology is improving remarkably. Peak speeds are a gigabit or more. Several chipmakers (Qualcomm, Broadcom, Quantenna, MediaTek, Marvell, and others) advertise 1.3 gigabit (peak-speed) .ac chips, while reports of tests cite raw peak speeds as high as 10 Gbps. While these heroic physical-layer speed demonstrations attract attention, the reality of the situation suggests smart policy will be necessary for even small fractions of these peak speeds to be enjoyed in use by consumers of internet data.
These high peak Wi-Fi speeds often use much of the existing unlicensed Wi-Fi 5 GHz spectrum to achieve the high advertised speeds (along with several spatial paths of that spectrum). However Wi-Fi uses a “collision protocol.” Collisions are attempts by more than one user/device/thing to use Wi-Fi on any of the access points at the same time. In this case, both “things” must wait a random period of time before attempting to transmit the same data again, leading to significant speed loss and delay in delivery of data. The more devices active, the more rapidly the performance decays. It is not unusual for the latest Wi-Fi systems advertised at Gbps speeds to actually provide only a few Mbps to devices in real use.
Wi-Fi speeds can be expected to drop very significantly in neighborhoods and buildings where several Wi-Fi access points are in use with typical numbers of Wi-Fi-capable devices connected.
In the future, the Internet of Things will increase the problem. Recent field tests of true throughputs in such crowded systems (using state of the art Wi-Fi access points and chips) often see speeds of just a few 10’s of Mbps or even less. Super crowded systems, such as the 50M “digital divided” users in the USA who go to public libraries for free internet connection will see speeds of less than 1 Mbps at times because of the heavy use during busy hours (4-8 pm at libraries). Schools can also see very low speeds from over-use, an issue to be addressed hopefully by recent E-rates allocations for public schools in the USA.
Some solutions for “enterprise environments” (big company sites, hospitals, bank and insurance company headquarters, etc) require all AP’s to be from the same manufacturer (see Cisco Meraki, Ruckus Wireless, and or Ericsson/Belair) and expensively require both manual tuning as well as automatic tuning specific by that manufacturer be used. These can lead to significant improvement if no other manufacturers’ systems are within “ear-shot.” However, Wi-Fi by its very nature is unregulated and recent FCC decisions (see Marriott case for instance) suggest that single-enterprise supply of Wi-Fi AP’s violates the law. Residential use in crowded apartment complex or even urban/suburban neighborhoods lead to overlap of dozens of access points’ transmissions, often with many different AP manufacturers’ products in use. Thus, the need for smart policy or use magnifies with increased Wi-Fi use.
Better physical-layer performance and these problems of contention/collision inspire new applications. ASSIA’s CloudCheck first measures and identifies Wi-Fi specific problems and issues specific to device, time, and location, while also evaluating whether the remainder of the internet connection has sufficient speed to sustain the Wi-Fi speed. Such tools empower the consumers themselves to help understand and improve their own connectivity as well as help regulators and ISPs know the true source of an internet bottleneck. Statistics generated can then help policy makers decide on spectra allocations. When Wi-Fi is not the bottleneck and fixed-line access (for instance DSL) is the bottleneck, Cloudcheck further uses the cloud, when systems are compatible, to bond (combine connections into appearance of single faster connection) fixed-line-WiFi connections to connection speeds of hundreds of megabits and more while avoiding the high cost of fiber to the home (or to the “wristwatch”). Using fixed line + WiFi means far more homes can receive ultra-broadband than would be possible given fiber’s high costs. For instance an apartment complex of 20 units all with 100 Mbps fiber/VDSL service has 2 Gbps of data rate that can be shared if Wi-Fi systems have some level of smart policy underlying their usage. Essentially, such policy would reverse the contention issues to an efficiency advantage.
Simultaneously with smart policy, today’s broadband home can be rapidly transformed. With 4x4 MIMO and beamforming, home gateways should be able to stream HD and UHD TV throughout most homes with minimal problems from collision/contention. However, letting the boxes run full speed selfishly wastes spectra and creates spatial wars among multiple access points. Access point manufacturers (boxes and chips) want to quote highest speed to potential buyers, but they really have no control over the contention issues so simply “blast away,” wasting spectra and power, and reducing real speeds to all. Further it helps no one for a Wi-Fi system to run at 1 Gbps when the fixed-line internet connection supporting it runs at 10 Mbps, or if the ISP network behind it supports only a few Mbps speed to the application being served to the consumer using the Wi-Fi device.
Gateways can also simultaneously connect literally dozens of devices, which is essential as we connect more things. Current IoT estimates show more than 10 connected devices per home in the developed world, and a rapid increase in smart-device use in the developing world. All phones as well as most audio players and TVs now have WiFi. Consumers can hear any music anywhere in the home without wires. This situation only compounds and makes more frequent the incidence of collisions and contention within the Wi-Fi spectra.
The rich ecosystem and near ubiquity of WiFi make it a primary tool for the exciting Internet of Things. Devices like Google’s Nest home thermostats, connected by WiFi, save money. WiFi connected medical equipment and smoke alarms can save lives. Industry economists calculate WiFi’s benefits as high as $200,000,000,000 each year. The recent U.S. auction reached $45B for relatively small amounts of licensed spectra.
With Wi-Fi’s great success to date come some great challenges for the future, perhaps with the greatest opportunity to much more cost effectively and spectrally efficiently address the exploding needs with unlicensed spectra. That’s why the Marconi Society will hold a Webinar on “Spectrum Choices” February 25 with Marconi Fellow hosting Marty Cooper and myself. Spectrum policy needs to ensure the airwaves are used efficiently. Doing this right will have enormous public benefit.