The looming spectrum crunch (and one possible solution)


By: SGN Staff

Editor's note: Getting more spectrum is one of the two biggest issues facing utilities, Connie Durcsak, CEO of the Utilities Telecom Council (UTC), said recently. (Enhancing cybersecurity is the other.) Durcsak rightly pointed out that distribution automation applications require a lot of redundancy and have low tolerance for latency. Substantially more bandwidth is required because "it’s about transporting a vast amount of data needed to manage this complicated environment and we have gone from one-way communications to multi-way,” she said.


UTC is pursuing one partial solution - namely, getting utilities included in plans for the nationwide public safety network, a broadband network that will operate in the 700 MHz band. But when a small company wrote me with another solution, I asked CEO Brian Andrew to contribute the short article below.


Brian had previously submitted a piece asking whether free spectrum can deliver the "ultimate" network. He is not without bias, since his company is one of the few that can perform the trick described below - namely, aggregating several small channels to create the equivalent of one big one.  Whether or not you agree with this particular solution, I wanted to be sure you were alerted to the problem. Take a look, and use the Talk Back form to comment on its potential. - Jesse Berst


By Brian Andrew


Every utility I speak with is concerned about spectrum availability and achieving higher bandwidth throughputs. Today, many utilities are experiencing interference with their unlicensed installations and/or are researching or investing in their own spectrum to add to their capacity.


The issue presented with purchasing licensed spectrum in the 200 or 900 MHz frequency range (besides cost) is that they are typically small chunks from 25-50 kHz and are rarely, if ever, contiguous. 


The aggregation solution

25 kHz will give you about 20 Kbps throughput and 50 kHz top ends around 40 Kbps.  Multiple networks of 10-40 Kbps throughput may not meet the need.  For higher bandwidth throughput the only solution is to aggregate (bring together) those non-contiguous narrow band channels. 


Aggregation works great whether you have purchased spectrum that is noncontiguous or are thinking of utilizing FCC Part 90 secondary licenses.


For those of you not up-to-speed on Part 90 secondary licensees; you get protection from any secondary license holders that are licensed after you. First in gets priority. So the message here is "GET IN EARLY”.


Spectrum on a secondary basis

If you investigate, I expect you will find there is plenty of available spectrum in the 217-220 MHz range to use on a secondary basis. This can be beneficial if you have not purchased any spectrum or you have "some” spectrum but not enough. If you don’t have enough you can supplement your purchased, licensed channels with secondary use licenses.


For instance our Parseous "Aggi” radio (Aggi as in aggregating) in the 217-220 MHz frequency range, aggregates up to 40 non-contiguous channels (6.25 kHz wide) to dynamically deliver up to 200 Kbps throughput in an on-demand basis. There are 240 12.5 kHz channels in the 217-220 MHz frequency range for the radio to select from.  If you own spectrum, you can set your channels as priority channels to be used by the radio and increase bandwidth throughput capacity by adding in channels on a secondary basis.


To operate under the secondary licensing rules, the radio must dynamically stop using that frequency and automatically switch channels if another licensed user with priority is sensed, if necessary to avoid interference and eliminate any service interruption.


Consider channel aggregation to increase throughput. In addition, consider radio management of time, space, frequency and power to improve reuse and eliminate interference in a high-density network.  A frequency-hopping technique is a good choice to minimize the amount of time that any frequency is utilized. Radios should also dynamically regulate their transmit power so they utilize the minimum amount of power needed to establish solid communications.


Brian Andrew is the CEO of Parseous Systems, whose radio systems are deployed for power utilities, water municipalities, farming, security and government and military installations.

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