T-Mobile's 6 Carrier Aggregation and Throughput Tue, Jan 09, 2024

On January 4th, Fierce Wireless posted a story on T-Mobile's six component carrier aggregation test with Ericsson and Qualcomm.  6 Carrier Aggregation, also known as 6CA, is a cutting-edge technology that allows mobile carriers to combine multiple frequency bands to increase network speed and capacity. By aggregating six carriers, T-Mobile can deliver faster download and upload speeds, reduced latency, and improved overall network performance.

What was interesting in the article from a spectrum expert standpoint are the details they included and the details that were left out.  Let's first look at the details that were included:

I am going to use our current Mobile Carrier - Spectrum Ownership Analysis Tool to determine the markets where T-Mobile has two blocks of PCS spectrum, two blocks of AWS spectrum and two blocks of 2.5GHz spectrum. 

Using the NR Channel Analysis Module, the specific 3GPP channels that are available for T-Mobile's spectrum in a particular county are displayed by NR band.  In the image below, we have filtered to display counties where T-Mobile holds two blocks of n25 spectrum and two blocks of n66 spectrum.

Channel Analysis - FDD Downlink:

This filter also included 2.5 GHz spectrum.  I wanted to find counties with both a 100 MHz channel and a 90 MHz channel to get the maximum throughput.

Channel Analysis - TDD:

I'm not quite sure how they arrived at 245 MHz for the combined spectrum.  If I only look at the FDD Downlink and the TDD spectrum, I can get 245 MHz with the configuration below..  This configuration is available to T-Mobile in 69 counties.

Channel Size (MHz)	NR Band
100	n41
90	n41
20	n25
10	n25
20	n66
5	n66
245	Total

 

To get the estimated composite channel throughput values, we have modeled 4x4 MIMO antennas with 256QAM modulation in our Throughput Analysis Tool, which is part of the Channel Analysis Module

Throughput Analysis - FDD Downlink:

Throughput Analysis - TDD Downlink Timeslots:

 

Throughput Summary:

Channel Size (MHz)	NR Band	Throughput (Gbps)
100	n41	1.736
90	n41	1.558
20	n25	437
10	n25	411
20	n66	556
5	n66	206
245	Total	4.904

 

Although I ended up with a higher throughput than was achieved in the test call, my throughput values are theoretical and would be reduced by real world conditions such as distance to the cell site and the achievable modulation. 

What is wrong with Spectrum Pricing? Tue, Dec 04, 2012

Clearly the wireless industry has locked in spectrum pricing with the MHz-POP pricing model, but is this the right way to look at it as we move into a 4G World where data throughput and capacity are key?  For those that aren't familiar, the typical value of spectrum is determined by the $/MHzPOP which is the dollars spent for the spectrum divided by the total amount of spectrum times population that spectrum covers.  This model falls short now as carriers are interested in acquiring larger contiguous blocks of spectrum enabling higher users speeds and more capacity.

To use a real estate analogue, a large plot of land is much for flexible for multiple uses, than two plots, even if they are in the same neighborhood.  In real estate, the developer that is able to consolidate several tracks of land into a larger development is rewarded as he sells the larger development.

In the wireless industry, we continue to price based upon the $/MHz POP basis, even as carriers such as T-Mobile and Clearwire have combined adjacent channels to create larger bands of spectrum to utilize in larger LTE channels.  T-Mobile has worked this year with Verizon, SpectrumCo, and MetroPCS which will allow it to assimilate a 2X20MHz LTE channel on a national basis.  Clearwire has leased and purchased operators in the BRS and EBS spectrum bands providing it with an average of 160MHz of spectrum in the top markets.  Since Clearwire's spectrum has many geographical boundaries, it is difficult to say how many 20MHz channels they could support across each of their markets, but they have been successful consolidating small bands of spectrum into larger more flexible spectrum bands.

How does a larger band of spectrum affect the wireless carriers?  In the US, carriers have deployed FDD-LTE in 1.25MHz channels, 5MHz channels, and 10MHz channels.  As you increase the channel size throughput performance improves because a lower percentage of the data packets are dedicated to overhead activities   Qualcomm has provided achievable LTE Peak Data Rates for different channel bandwidths based upon whether the antennas are 2x2 or 4x4 MIMO.

Link to Qualcomm Document



As you can see in the 4x4 MIMO downlink case, the throughput is 12Mbps greater in the 20MHz channel than the composite of 4-5MHz channels.

So if a  20MHz channel is 4% more efficient than 4 - 5MHz channels should the MHz POPs pricing adjust accordingly?

By the way.. I am going to look for more source data on the capacity improvements for wider channels, a 4% improvement would seem to be relatively negligible.  I recall hearing 30% improvements in capacity when a channel size is doubled, but I haven't been able to re-source that data for this blog.   More to come.