Monday, June 13, 2016

AT&T Tests Fixed Wireless at 15 GHz and 28 GHz

It would not be unreasonable to argue that new millimeter spectrum, 5G mobile network platforms and advances in antenna technology and signal processing will make possible a new business case for fixed wireless as an alternative to other forms of Internet access.

AT&T, among others, is testing fixed wireless, using the 15 GHz and 28 GHZ bands. That is important since AT&T has promised the Federal Communications Commission it will add 13 million new high speed access connections using fixed wireless, over about the next four years.

Separately, Verizon also says it is looking at using fixed wireless.

Microsoft, Facebook and Google also are looking at the platform, Microsoft primarily backing TV White Spaces, while Facebook is testing new transmitting arrays and Google is testing use of millimeter waves

Google Executive Chairman Eric Schmidt has confirmed that Alphabet is looking seriously at adding fixed wireless to its arsenal of access platforms, and has been testing 3.5 GHz frequencies and platforms in its Kansas City market.

Facebook’s Project ARIES, presently in test mode, features a base station with 96 antennas, supporting 24 simultaneous streams. It is envisioned as a fixed wireless platform for Internet access.

Facebook so far has achieved 71 bps/Hz, and Facebook engineers are aiming for supplying 100 bps/Hz eventually.

By way of comparison, that would surpass the efficiency of Long Term Evolution and vastly outperform most other interfaces ever commercially deployed.

Frequencies in the millimeter band that once were commercially unusable for communications purposes will be usable to support 5G and other networks, in large part because of advances in network architecture (small cells) and the ability to use sophisticated signal processing and antennas to recover useful signals that would have been quite difficult in an analog environment.

The issue is where the business models will work, taking into account signal loss characteristics of millimeter waves. Of course, we have some commercial experience with use of point-to-point communications. Even earlier-generation radios for point-to-point links could achieve distances of 3 km to 5 km (roughly two to three miles), assuming line of sight is possible.

Keep in mind that the engineering of fixed network local loops in the United States has been to keep access cables at 18,000 feet or less (three miles). Though foliage, buildings and other obstructions, plus typical weather conditions, will impose greater constraints on any single transmitting site, 28 GHz signals reach about as far as the design length for fixed network access lines.

The issue with today’s MIMO (multiple-input and multiple-output) antenna technology is how much better performance generally can be expected, and what per-unit costs for MIMO antenna systems used for 5G and other networks will be, in volume production.



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