There's no such thing as a free lunch...

By Dudy Cohen

“There is no such thing as a free lunch.” True, but what about paying way less for the exact same lunch? Let’s talk about spectrum costs.

You can save $4M a year! And you do not have to give up anything in return.

Spectrum costs is a big issue at the dawn of any new mobile generation and 5G is no exception. In the last couple of months, AT&T & T-Mobile USA committed to spend $1.8B on 24GHz spectrum. Likewise, Canadian operators spent $3.5B on 600MHz spectrum, while German operators spent $7.3B on 2GHz and 3.6GHz 5G spectrum.

So, you ask, where are the savings?

Interestingly enough, some of the proposed spectrum for 5G radio access is currently used for wireless backhaul applications.

This spectrum is typically block-allocated – a license to use a channel is acquired on a national or regional basis, and not on a link-by-link basis. So, the actual cost per link is dependent on the number of links you are able to utilize using a specific channel.

And here comes the savings! What if you could use the same frequency channel for more links in your network? In such a case, you could reduce the number of channels used (and payed for) in your network, and enjoy one of two benefits:

  1. Save the annual fee on the channels you no longer need. This fee could be as high as $1M per channel per annum.

  2. Reallocate this spectrum for 5G RAN use – that is, if the regulator allows that. In this case you can save on acquiring such spectrum in the ongoing spectrum auctions.

In order to understand how we can make this happen, we need to first understand the concept of frequency reuse. Using a frequency channel, say F1, in two adjacent links may cause interference and service degradation (or even link failure) for those links. To avoid that, we typically use the F1-F1 spectrum configuration in link coupling, in which the angular separation is equal to or greater than 90O. This rule-of-thumb applies to common Class 3 antennas. In cases in which the angular separation is lower than 90O, we will typically use two channels: F1-F2.

The number of channels required in the network, therefore, is derived from the network architecture and planning – the denser the network, the higher the number of required channels and the higher the spectrum fee.

There is a way, though, to use an F1-F1 configuration in links that are lower than 90O. In fact, this way allows you to reuse frequency with links that bear as little as 15O separation! Based on Ceragon’s multicore technology, this unique capability is called “Advanced Frequency Reuse.”

Based on tight integration between the two links, Advanced Frequency Reuse eliminates interference caused by the adjacent link to the level of maintaining the highest modulation and capacity in links that are 15O apart. Such adjacent links otherwise are destined to suffer severe fading and failures.

Implementing Advanced Frequency Reuse in your network allows you to reduce the number of used channels. Field implementations teach us that typical savings are around 40%.

So if you are using 10 channels in your network and paying $1M per annum for each, you may save $4M a year.

Enjoy your significantly less expensive lunch!

To learn more, read our Technical Brief

Advanced Frequency Reuse