Podcast: Cameron Kilton from Alpha and I talk about LTE

Cameron Kilton from Alpha Wireless and i sit down at the 2019 Indiana ISP meeting and talk about LTE and Wireless operators.  Pardon the rough beginning. the room we were in had a flickering light that took me by surprise near the beginning and messed with my rhythm.

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Alpha Wireless

The addition of RF elements horns to a PTP550 link

Originally posted at:

In a previous series of articles we talked about a new Cambium 550 link and the noise challenges we had.  You can start your reading in Part one and Part two.

Due to the frequency challenges, we decided to upgrade the dishes to RF Elements Ultra Horns.

If you recall our spectrum looked like this before.

After the horns. While not a night and day difference you will notice several improvements across the band.  Less red and yellow on the scan and sharper drop-offs. We saw the most improvement in the 5160 area and the 5720 ranges.  And this is with the horns pointed right at the source of most of the 5GHZ noise.   Not much you can do if you are pointed right at the noise.

What did this mean for the link? It meant we were able to find a 200 meg increase because we were able to obtain better modulation on the link.

So while we were not able to filter out all of the noise we wanted, we were able to increase our MCS rates on a very noisy link to increase bandwidth and increase the reliability of the link.  Before the horns, the MCS rates would be in a constant state of flux dealing with noise.

The Changing RF landscape for WISPs

Recently, there have been some discussions on Facebook about waining support for 2.4GHZ .  KP Performance recently published a Future of 5GHZ and beyond blog post. So why all this focus on 5GHZ and why are people forgetting about 2.4?

To answer this question, we need to update our thinking on the trends in networks, not just wireless networks.  Customers are demanding more and more speed. Network backbones and delivery nodes have to be updated to keep up with this demand. For anything but 802.11 wifi,2.4GHZ can’t keep up with the bandwidth needs.

One of the significant limitations of many 2.4 radios is they use frequency-hopping spread spectrum (FHSS) and/or direct-sequence spread spectrum (DSSS) modulation. Due to 2.4GHZ being older, the chipsets have evolved around these modulation methods because of age.  When you compare 2.4GHZ to 5GHZ radios running OFDM, you start to see a significant difference.  In a nutshell, OFDM allows for higher throughput. If you want to read all about the differences in the protocols here ya go: http://www.answers.com/Q/Difference_between_ofdm_dsss_fhss

Secondly, is the amount of spectrum available.  More spectrum means more channels to use, which translates into a high chance of mitigating interference. This interference can be self-induced or from external sources. To use an analogy, the more rooms a building has, the more simultaneous conversations can happen without noise in 2.4GHZ we only have 3 non-overlapping channels at 20mhz. Remember the part about more and more customers wanting more bandwidth? In the wireless world, one of the ways to increase capacity on your APs is to increase the channel width. Once you increase 2.4 to 30 or 40 MHz, you do not have much room to deal with noise because your available channels have shrunk.

One of the biggest arguments in support of using 2.4GHZ for a WISP environment is the physics.  Lower frequencies penetrate trees and foliage better. As with anything, there is a tradeoff.  As the signal is absorbed, so is the available “air time” for transmission of data.  As the signal travels through stuff, the radios on both sides have to reduce their modulation rates to deal with the loss of signal.  Lower modulation rates mean lower throughput for customers.  This might be fine for customers who have no other choice.  This thinking is not a long term play.

With LTE especially, traditional thinking is being uprooted.  Multiple streams to the customer as well as various paths for the signal due to antenna stacking are allowing radios to penetrate this same foliage just as well as a 2.4 signal, but delivering more bandwidth. These systems are becoming more and more carrier class.  As the internet evolves and becomes more and more critical, ISPs are having to step up their services.  The FCC  says the definition of broadband is at least 25 meg download. A 2.4 radio just can’t keep up in a WISP environment.  I am seeing 10 meg becoming the minimum customers want. Can you get by with smaller packages? Yes, but how long can you maintain that as the customer demand grows?

So what is the answer? Cell sizes are shrinking.  This is helping 2.4 hold on.  The less expensive radios can be deployed to less dense areas and still provide decent speeds to customers.  This same trend allows 5GHZ cells to be deployed as well. With less things to go through, 5GHZ can perform in modern networks at higher modulation rates.  Antenna manufacturers are also spending R&D to get the most out of their 5GHZ antennas. More money in the pipeline means stronger products. My clients are typically deploying 3.65 and 5GHZ on their towers.  LTE is changing RF WISP design and taking the place of 2.4 and 900.