Tag Archives: licensed spectrum

Packet Loss and Broadband Performance

In a recent article in FierceWireless, Joe Madden wrote an article looking at the various wireless technologies he has used at his home in rural central California. Over time he subscribed to a fixed wireless network using WiFi spectrum, cellular LTE broadband, Starlink, and a fixed wireless provider using CBRS spectrum. A lot of rural folks can describe a similar path where they have tried all of the broadband technologies available to them.

Since Joe is a wireless expert who works at Mobile Experts, he was able to analyze his broadband performance in ways that are not easily understood by the average subscriber. Joe came to an interesting conclusion – the difference in performance between various broadband technologies has less to do with speed than with the consistency of the broadband signal.

The average speed tests on the various products varied from 10/2 Mbps on fixed wireless using WiFi, to 117/13 Mbps on Starlink. But what Joe found was that there was a huge difference in consistency as measured by packet loss. Fixed wireless on WiFi had packet loss of 8.5%, while the packet loss on fixed wireless using CBRS spectrum dropped to 0.1%. The difference is stark and is due to the interference that affects using unlicensed spectrum compared to a cleaner signal on licensed spectrum.

But just measuring packet loss is not enough to describe the difference in the performance of the various broadband connections. Joe looked at the number of lost packets that were delivered over 250 milliseconds. That will require some explanation. Packet loss in general describes the percentage of data packets that are not delivered on time. In an Internet transmission, some packets are always lost somewhere in the routing to customers – although most packets are lost due to the local technology at the user end.

When a packet doesn’t show up as expected, the Internet routing protocols ask for that packet to be sent again. If the second packet gets to the user quickly enough, it’s the same, from a user perspective, as if that packet was delivered on time. Joe says that re-sent packets that don’t arrive until after 250 milliseconds are worthless because by then, the signal has been delivered to the user. The easiest way to visualize this is to look at the performance of Zoom calls for folks using rural technologies. Packets that don’t make it on time result in a gap in the video signal that manifests as fuzziness and unclear resolution on the video picture.

Packet loss is the primary culprit for poor Zoom calls. Not receiving all of the video packets on time is why somebody on a Zoom call looks fuzzy or pixelated. If the packet loss is high enough, the user is booted from the Zoom call.

The difference in the percentage of packets that are delivered late between the different technologies is eye-opening. In the fixed wireless using WiFi spectrum an astounding 65% of re-sent packets took longer than 250 ms. Cellular LTE broadband was almost as bad at 57%. Starlink was better at 14%, while fixed wireless using CBRS was lowest at 5%.

Joe is careful to point out that these figures only represent his home and not the technologies as deployed everywhere. But with that said, there are easily explainable technology reasons for the different levels of packet delay. General interference plays havoc with broadband networks using unlicensed spectrum. Starlink has delay just from the extra time for broadband signals to go to and from the satellite and the ground in both directions. The low packet losses on a CBRS network might be due to having very few other neighbors using the new service.

Joe’s comparison doesn’t include other major broadband technologies. I’ve seen some cable networks with high packet loss due to years of accumulated repairs and unresolved issues in the network. The winner of the packet loss comparison is fiber, which typically has an incredibly low packet loss and also a quick recovery rate for lost packets.

The bottom line from the article is that speed isn’t everything. It’s just one of the characteristics that define a good broadband connection, but we’ve unfortunately locked onto speed as the only important characteristic.

Finally a Use for LMDS

Satellite_dish_(Television)Vivint provides a range of security and home monitoring products and has recently also become a wireless ISP in a few markets such as San Antonio, El Paso, and a few towns in northern Utah. What I found interesting is that they are using the LMDS spectrum.

LMDS stands for Local Multipoint Distribution Service and is a licensed spectrum operating between 27.5 GHz to 31.3 GHz, close to the range of various microwave frequencies. The LMDS spectrum was sold in a very robust A band that was an 1150 MHz swath of bandwidth and a B band of 150 MHz of bandwidth.

This was auctioned to the public in 1998. I know a number of companies that bought the spectrum then and I know a few who created business plans using LMDS that all failed. There were two problems with using LMDS. The first was the chicken and egg issue that all spectrum faces. A spectrum can’t really be used commercially until somebody develops cheap gear to use it and the vendors won’t develop cheap gear until they get a large buyer who will buy enough gear to finance the R&D. After the spectrum hit the market there were a few beta tests of equipment that didn’t work well, but no big user and the market died.

The other issue is the practical application of using the spectrum. In 1998 this was touted as being able to deliver a wireless DS3 which is about 45 Mbps. That was a lot of bandwidth in 1998, but over time that is no longer particularly great. And the spectrum has real-life limitations. On a point-to-point basis it can go, at best, about 5 miles and on a point-to-multipoint basis it can go, at best, about a mile and a half. The spectrum can achieve those distances in areas without a lot of humidity (which is why Vivint is deploying it in the dry southwest). It also is easily deflected by trees and buildings, another reason to go to west Texas and Utah.

So this spectrum has basically gone mostly unused for a decade and a half. A lot of license holders have a few point-to-point links working on it just to preserve their license, but I am sure there are license holder who just let it go. Vivint is buying rights to the spectrum in these markets from XO Communications and Straight Path Communications.

It looks like Vivint has found a strategy for monetizing the equipment. They obviously found radios that will work on the spectrum, which is not that unusual today now that we have software tunable radios that can work on a wide range of spectrums (something we didn’t have in 1998).

Vivint is also dealing with the distance and bandwidth limitations in a very creative way. They are selling in urban/suburban areas giving them a decent density within the range of a given transmitter. They are then using point-to-point radios to bring bandwidth to what they call hub homes. They are giving these homes free Internet connectivity for housing and powering their equipment. From each of these homes they will serve up to 24 other homes. That small number of subscribers is what allows them to offer the 100 Mbps bandwidth. If they serve more homes the effective bandwidth would quickly drop.

Vivint prices 100 Mbps bandwidth at $59.95 per month. For the wireless customers they are also offering VoIP plus cloud storage. Plus Vivint has a wide range of security and other products they can sell to a household. It’s not a standard bundle, but it’s a pretty good one.

This doesn’t look like a bad business plan. With the range of services they sell they are probably averaging more than $85 per customer per month on average, and maybe more. And they are gaining some economy of scale and report having over 15,000 customers.

This business plan certainly isn’t for everybody. It wouldn’t work well in places like humid Florida or Louisiana. It also wouldn’t work well in towns that are solid trees. This business plan takes a lot of discipline to be successful. Once they have established a hub home the business plan is only going to work if they can find other customers in the same local area, within 1.5 miles. I figure that they knock on doors to find customers around every hub home. The math would be terrible if they only got a few homes per hub.

They also have to find licensed LMDS spectrum holders and they obviously have in these markets. But that might not be possible in other markets. This business plan must be urban in order to have enough density, and this looks totally infeasible in rural areas.

I have to credit Vivint with finally finding a market use for this spectrum. In today’s marketplace it sounds like they have put together a very marketable suite of products including bandwidth at an affordable price. This is what competition looks like. While LMDS spectrum is only going to work this well in arid places, the idea of a non-traditional bundle is one that others ought to consider.