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.
As has now become the case for millimeter wave transmission systems, which once were commercially limited in an analog environment, cheap and fast signal processing now allows commercial use of frequencies that would have been of little practical use in the past.
Some even speculate that Google Fiber might be able to expand nationwide using fixed wireless, and not relying solely on fiber to the home.
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.
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.
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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