by Andrew J. Shepherd

Sprint 4G Rollout Updates

Wednesday, August 5, 2015 - 1:28 PM MDT

Columbus. But not 1492. Just 8640. And 26640, too.

This discovery did not require an Italian navigator sailing under the Spanish flag, nor the Niña, the Pinta, and the Santa Maria. Instead, the explorers were an intrepid S4GRU Columbus membership group (sorry, restricted to S4GRU sponsors), some handsets, some screenshots, and some speed tests.

Those last two numbers 8640 and 26640 are the paired EARFCNs 8640/26640 of a band 25 additional carrier found this week in the Columbus, OH BTA. Seemingly, not such a big deal. S4GRU and its members have been finding band 25 additional carriers with different EARFCNs in multiple markets for months now. We even have two tracking threads for additional LTE carriers -- one for all three bands, one for band 25.

However, this band 25 additional carrier discovery represents truly a New World for Sprint. It is 10 MHz FDD. Now, that alone is a big deal. But it is actually just the second finding of a 10 MHz FDD carrier that we have had in the past four days. The Champaign-Urbana, IL BTA came first. We hope to follow up with an article on that later.

More importantly, though, the Columbus 10 MHz FDD carrier is a complete refarming of the PCS G block. The standard 5 MHz FDD carrier at EARFCNs 8665/26665 that is omnipresent across the Sprint LTE network is gone -- it is gone forever where this new carrier has appeared in the Columbus BTA.

To dive right in, let us take a look at two screenshots from the Columbus area...

The engineering screenshot shows the new EARFCN pair of 8640/26640. That in and of itself is not evidence of 10 MHz FDD. But you have to understand that those EARFCNs put the center frequencies of the LTE carrier at 1990 MHz (downlink) and 1910 MHz (uplink), which is precisely the dividing line between the PCS C5 block and the PCS G block. Even as Sprint controls both blocks, there is no reason to make that move -- unless to expand LTE carrier bandwidth across both blocks. We will take a deeper look at this with Sprint spectrum holdings in a moment.

Moreover, look at the speed test. With 2x2 downlink MIMO, a 5 MHz FDD carrier maxes out at 37 Mbps. This speed test -- and others gathered by the Columbus network trackers -- greatly exceeds that number. Add up the evidence. It is clearly a 10 MHz FDD carrier.

Back to the spectrum issue, we should have an extensive look at the Sprint spectrum provenance in the Columbus market. Yes, it will be extensive, but I think that you will enjoy the history lesson. The reason is that Columbus holdings are somewhat unique, so this 10 MHz FDD fervor should not be extended elsewhere -- for now.

The PCS D 10 MHz (5 MHz FDD) block and PCS E 10 MHz (5 MHz FDD) block were Sprint's original FCC auction winnings back in 1997. The PCS G 10 MHz (5 MHz FDD) block was awarded to Nextel as compensatory spectrum for its SMR 800 MHz rebanding. Of course, Sprint acquired that nationwide set of licenses in the merger. The PCS C4 10 MHz (5 MHz FDD) block is the most recent acquisition, as low budget wireless operator Revol went kaput and sold off its spectrum.

The PCS C5 10 MHz (5 MHz FDD) block is worth a separate discussion -- because it has an interesting history on several fronts. It was FCC auctioned three times. The first winner was NextWave, which later filed for bankruptcy protection. So, the FCC canceled licenses and auctioned again. Meanwhile, the growth of the wireless industry had caused NextWave's licenses to increase in value, leading to a Supreme Court ruling that the FCC was outside its bounds to confiscate the licenses from the bankrupt NextWave. Thus, that re auction was invalidated. Finally, NextWave reached a financial settlement with the FCC to return some of its licenses, which were "re re auctioned" in 2005. And Wirefree Partners, a DE (Designated Entity) working with Sprint, won the PCS C5 block in Columbus.

That brings us to the second interesting point of spectrum provenance. And this part will certainly veer into editorial content. In FCC auctions, a DE is a small business or minority/woman controlled business that qualifies for bidding discounts. Additionally, the PCS C and F blocks typically were reserved or positioned for DEs. The idea was to increase diversity in the wireless industry. The predecessors of both T-Mobile and AT&T -- through the notorious likes of Cook Inlet PCS, Salmon PCS, et al. -- garnered many of their PCS licenses by way of DEs. Just this year, though, the FCC officially shot down Dish for its use of several DE bidders in the recent AWS-3 auction. No discount for Dish!

VZW and Sprint rarely used such underhanded tactics, but this is one such case for Sprint. Wirefree Partners was a Sprint collaborator, qualified as a DE, won the Columbus license at auction, then later sold the license in full to Sprint.

For a complete Sprint PCS 1900 MHz band plan in Columbus, see the following graphic:

From a historical perspective, what we can see is that Sprint held three non contiguous blocks: PCS D, E, and C5. The additional guard bands due to lack of contiguity of those three blocks were not a great situation, but the total amount of spectrum was more than good enough for CDMA2000. However, when LTE entered the mix, things got truly interesting. That is when the PCS G and C4 blocks entered the stage.

Next, let us look at deployment within Sprint's PCS spectrum holdings in Columbus. Think of the two graphs as before and after. The first, before, and the second, after Columbus 10 MHz FDD discovery:

In the second graph, see how the PCS G block 5 MHz FDD carrier that Sprint users across the country are familiar with has been refarmed, then a new 10 MHz FDD carrier put in its place that spans both the PCS C5 and G blocks.

An almost prophetic piece to all of this comes from the early history of S4GRU. In an article that we published over three years ago, S4GRU identified Columbus as a market that could run a 10 MHz FDD carrier through a combination of the PCS C5 block + PCS G block. Some spectrum holdings have changed that we could not have predicted at that time -- notably, the USCC and Revol spectrum acquisitions. But, remarkably, that possibility of a 10 MHz FDD carrier in Columbus has come to fruition. Read the article if you have not (yes, I wrote it), but you can view the table from it below:

With the elimination of the band 25 carrier at EARFCNs 8665/26665, some may be worried that early single band Sprint LTE handsets will be forced back to EV-DO in the Columbus area. That is a legitimate concern, as many of those single band handsets were originally authorized with the FCC for only 5 MHz FDD, thus cannot use 10 MHz FDD. In refarming all of band 4 W-CDMA to LTE across multiple markets, for a similar example, T-Mobile certainly required affected users to upgrade to new devices or be hung out to dry on GSM.

To provide just one key Sprint illustration, here is S4GRU's FCC OET article on the Samsung Galaxy S4. Note the 5 MHz FDD limitation. But here is the kicker. Most/all of those early single band handsets with LTE bandwidth limitations have had Class II Permissive Change filings at the FCC in the intervening years. Above is the linked filing for the Galaxy S4. Below is a pertinent screenshot from said filing. Note the "additional bandwidths" language.

Even without the Class II filings, though, the expansion to 10 MHz FDD in Columbus should pose no harm to single band handsets. Long before this 10 MHz FDD carrier came to light, S4GRU members found evidence of an additional 5 MHz FDD band 25 carrier located at EARFCNs 8565/26565. See the engineering screenshot below:

In a nutshell, the 5 MHz FDD carrier in the PCS G block has been replaced by an equivalent 5 MHz FDD carrier in the PCS C4 block -- as depicted in the deployment graph and screenshot above.

Now, keep in mind, band 41 remains the high capacity priority for Sprint. This 10 MHz FDD refarming is not yet everywhere even in Columbus -- it has been popping up on various sites, spreading from the outside into the city. And while many other Sprint markets will have an additional 5 MHz FDD carrier in band 25, few will see 10 MHz FDD anytime soon. So, Columbus may serve as something of a testbed. But S4GRU has some educated insight as to where this might be headed next.

As mentioned earlier, downstate Illinois around Champaign-Urbana also has unique spectrum holdings and got the 10 MHz FDD treatment a few days ago. Chicago has a similarly unique yet different spectrum set. But as S4GRU published in another article in 2012, it has a contiguous, green field USCC block of spectrum that now seems to be begging for 10 MHz FDD.

A band 25 additional carrier already resides in that USCC PCS B block disaggregation -- but it is presently 5 MHz FDD. And an additional EV-DO carrier has been added at the bottom of the block. Still, there may be enough spectrum left to expand that 5 MHz FDD to 10 MHz FDD very soon.

The Windy City, are you ready for it? We shall see if S4GRU's short term prediction proves as accurate as its spectrum analysis did three years ago.

To be continued...

Sources: FCC, S4GRU members and staff