by Tim Yu

Sprint 4G Rollout Updates

Friday, April 8, 2016 - 3:40 PM MDT

Over the past week, S4GRU members in multiple Sprint markets have discovered new EARFCNs and corresponding GCI endings that identify new Band 41 LTE carriers.

The EARFCN is the center frequency of an LTE carrier that, along with the carrier bandwidth, identifies the carrier placement and occupied spectrum.

As Sprint is doing intraband contiguous/adjacent carrier aggregation -- 20 MHz TDD Band 41 carriers are lined up right next to one another with no gaps -- Band 41 EARFCNs are highly predictable in a given market by knowing the location of at least one carrier.

Say the ever popular EARFCN 40978 is the first carrier.

You add 198 (19.8 MHz) to it to get EARFCN 41176, which is the second Band 41 carrier.

Thus, it stands to reason if you add 198 to that EARFCN, you will get the third Band 41 carrier so 41176 + 198 = 41374, the EARFCN for the third Band 41 carrier.

Or, in some other markets, 41078 is the first Band 41 carrier. In this case, it goes like this: 41078 + 198 = 41276 + 198 = 41474

Alternatively, say a market has EARFCNs 40056 and 40254. Adding 198 would bring us to EARFCN 40452, but that is not possible due to the BRS/EBS 2500-2600 MHz band plan -- there are spectrum gaps around 2570 MHz and 2610 MHz that Sprint cannot utilize. See the band plan:

Thus, in the case of EARFCNs 40056 and 40254, not addition, but use subtraction: 40056 - 198 = 39858, which would be the third Band 41 carrier.

The GCI is the unique cell sector identifier of a LTE carrier.

Generally speaking, Sprint's GCI patterns are standardized market by market and network wide, making for an easy method to identify each LTE carrier within a given band. In the case of Band 41, GCIs ending in 00/01/02 (Samsung) or x1/x2/x3 (ALU/NSN) indicate a connection to the original and first Band 41 carrier. GCIs ending in 03/04/05 (STA) or x9/xA/xB (ALU/NSN) denote the second Band 41 carrier.

It stands to reason that -- if this second carrier pattern were to continue to the third Band 41 carrier in Samsung markets -- we would expect to see GCIs possibly ending in 06/07/08. Long story short, this theory is supported by evidence. See below SignalCheck Pro logs and numerous in app screenshots:

This log is from my Nexus 5x. I traveled for a hour around Sacramento, searching for the third Band 41 carrier. Note the GCI endings for the Sprint Band 41 entries:

The following is from site member bmoses in Des Moines. Note the 07 GCI ending and EARFCN:

Below is from a S4GRU member in the Colorado market:

One more from the Cincinnati, Ohio Market:

The following is from yours truly in Sacramento:

And these below are from Fremont, CA, near San Jose:

See those EARFCNs and GCI endings? Look at the calculations from the top of this PSA. Everything is as we would have predicted for a third carrier.

With the end of the WiMAX injunction and the decomissioning of the last active Clearwire WiMAX markets that held up huge swaths of leased EBS and licensed BRS spectrum, Sprint finally has the capability to show off its deep spectrum pockets in numerous markets. This has been long awaited and should definitely give a huge boost to Sprint data speeds in numerous markets where spectrum for additional Band 41 carriers now is available. Of course, there still is the issue of actually connecting to and using this third Band 41 carrier.

From firsthand reports and personal use, this third Band 41 carrier is not currently carrier aggregation enabled. Thus, 2x/3x CA devices may not connect to it to use data right now. By default, these devices will have CA enabled, causing them to utilize only the first and second carriers that they can aggregate. For the time being, in order to reliably connect to this third carrier, a non CA triband device or a 2x/3x CA setting disabled triband device may be required. Regardless, this appears to be just a minor issue from the initial rollouts that should be resolved soon.

Source: S4GRU member reports