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:
- Merged 6 - 5G channels of mid-band spectrum
- 2 channels of 2.5 GHz spectrum (n41)
- 2 channels of PCS spectrum (n25)
- 2 channel of AWS spectrum (n66)
- Total aggregated spectrum was 245 MHz
- Throughput (speed test) exceeded 3.6 Gbps
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.
In the charts below, we present the current carrier aggregation plans for AT&T, Verizon, USCellular, Dish, T-Mobile, and Sprint. Green indicates that particular frequency block is used one time in the aggregation scheme. Yellow indicates that particular frequency block is used twice in the aggregation scheme. For both the green and yellow highlights, only one carrier can be utilized in each frequency block. The blue highlights indicate that multiple carriers can be utilized in each frequency block (non contiguous).
AT&T
Verizon
T-Mobile
Sprint
Dish
US Cellular
As I was completing my research for an upcoming blog on LTE Carrier Aggregation, I found that my previous LTE Band Class reference sheet was missing some of the more recent Band Class updates, so I decided to share my new reference document with a few comments.
FDD Band Classes:
The first notable band class addition in Band 30. This band class creates a definition for FDD operation in the WCS (2.3GHz) band which was previously defined only for TDD operation.
From the Spectrum Grid view of the Spectrum Ownership and Analysis Tool, you can see that Band 30 does not include the 5MHz channels that AT&T purchased to essentially become guard bands for the Satellite Audio guys. This will provide AT&T with a 10x10 LTE channel on a market by market basis, as they resolve the remaining ownership issues in the WCS band.
The next two band classes are not new, but I previously skipped over these band classes because I didn't fully understand their frequency breaks.
Band 26Previously I thought this was a specific band for Sprint IDEN operation that is adjacent to the cellular band. This is the band where Sprint is placing their 2nd LTE channel (5 MHz) and a CDMA channel (1.23 MHz). Looking at the frequencies in detail, the band class covers the IDEN spectrum and the adjacent cellular spectrum.
This is similar to Sprint's Band 25 which includes all of the PCS band plus their G block spectrum (but not the H block).
So you would think that all of the North American carriers could standardize to Band 25 for PCS operation and Band 26 for Cellular. Using the latest iPhone 5s LTE band support,
you can see the Verizon, T-Mobile, and AT&T iPhone's support Band 2 and 25 for PCS, but only the cellular band (Band 5). Sprint iPhone 5s includes,
both Band 2 and 25 for PCS and Band 5 and 26 for cellular.
Band 10:
This is referenced as the AWS extended band and you can note from above that it is not currently applied to smartphones like the iPhone 5s. This band class seems to be a preparation for the future use of the AWS-2 and AWS-3 spectrum and the government shared use band that are both adjacent to the existing AWS spectrum band. Here is how the downlink looks in the Spectrum Ownership Analysis Tool:
Note that Band 10 does not cover the entire band contemplated for AWS-3, nor does it include Dish's Band 23. For the uplink:
This again depicts that Band 10 is not currently set to include the entire shared government opportunity.
TDD Band Classes:
Here is the reference sheet the TDD band classes.
On this reference sheet I hadn't looked closely at band classes 35, 36, and 37. I had always focused on the 2.3GHz and 2.5GHz as the only bands that were designated for TDD support in North America. These three band classes create 140MHz block of spectrum that could be for TDD deployment. Here is how these bands appear in the Spectrum Ownership Analysis Tool:
I'm not sure what the history is on these band classes, but they would support TDD operation in both the PCS uplink and downlink bands as well as in the 20 MHz between the bands. Since the PCS frequencies are highly deployed, I would consider it very unlikely to see TDD systems in this band in the near future, and I doubt that the PCS band is authorized for TDD operation. It will be interesting to see whether any of the wireless carriers begin to look this direction. With Sprint stepping out of the H block auction, they seem to be signalling that TDD operation is more important to them and the Band 37 block (including Sprint's G block) could be the reason why Dish is pushing forward in the H block auction. Please comment if you are aware why the 3GPP has included these 3 TDD band classes.
It is interesting to look at the details of Verizon's spectrum purchase from US Cellular in the St Louis market area (EA-96). Many industry sources talk about how purchase will provide 20MHz for Verizon's LTE. While this is true, it should not be confused with Verizon deploying a 20 x 20 channel. As can be seen from the Spectrum Grid view of AllNet Labs' Spectrum Ownership Analysis Tool, Verizon is purchasing the AWS B channel and previously owned the F channel. Although Verizon will own 20 MHz of spectrum, it is not contiguous and until they can deploy Release 12 software code into their network, they will have to operate this spectrum as two separate 10 MHz channels. Release 12 is likely a 2015 or maybe 2016 release since operators are either planning or deploying Release 10 currently.
The industry talks alot about Carrier Aggregation (CA) but there are several facts that are not well understood. First, Release 10 includes the functionality for carrier aggregation but the frequency band definitions for the US are not included until Release 11. Another point that needs to be understood is that the initial definitions require that aggregated carriers be in contiguous blocks in different spectrum bands (inter-band) or in separate blocks but in the same band (intra-band). For Release 11, only 2 carriers can be aggregated together. For Release 12, Verizon has sponsored a work group that will allow 3 carriers to be aggregated, 1 from the 700MHz band and 2 different carriers from the AWS band. Thus, Release 12 will be necessary for Verizon to aggregate their two AWS blocks of spectrum with their 700 MHz LTE.
The Spectrum Grid view is sorted by the EA geographical area which show that the AWS B and C licenses have not be dis-aggregated. The A channel licenses do show discontinuity since they were originally auctioned as CMA licenses. AT&T through their Leap purchase will strengthen their AWS ownership in this market.
To look at the competitive picture for spectrum in the St Louis market (EA-96) we can look at the
Company By Band worksheet from the AllNet Labs' Spectrum Ownership Analysis Tool. Looking first at Verizon, we can see the variety of spectrum depths across the EA that Verizon indicated in their FCC filing. Verizon will range from 62 MHz to 117 MHz depending on the county. The only county that Verizon controls 117 MHz is Montgomery County, MO which is 40 miles west of St. Louis.
Looking at the other carriers in this market we see that US Cellular will still control between 32 MHz and 69 MHz, while AT&T with their Leap purchase will control between 61 MHz and 105 MHz.
T-Mobile controls between 40 MHz and 60 MHz with two counties at 70 MHz and Sprint with their Clearwire purchase controls between 130 MHz and 242 MHz.
Recently I reviewed the 3GPP Standards site to check in on the status of LTE Carrier Aggregation. I found a gold mine of information.
First a few definitions: Carrier Aggregation allows a wireless carrier to band together different blocks of their spectrum to form a larger pipe for LTE. This can be accomplished in two ways: Inter-band and Intra-band.
Inter-band combines spectrum from two different bands. The spectrum in each band to be combined must be contiguous within that band. Intra-band combines spectrum from two non-contiguous areas of the same band.
Here is a link to an article from 3GPP that explains Carrier Aggregation.Below is a table summarizing the relevant 3GPP working group descriptions for Carrier Aggregation.
First of all, the current network release for all carriers is Release 9. T-Mobile, Sprint, and Clearwire have announced that they are deploying Release 9 equipment that is software up-gradable to Release 10 (LTE Advance). From the chart, it does not appear that there are any carrier configurations planned until Release 11. Release 10 appears to be a late 2013 commercial appearance and Release 11 will likely be very late 2014 or mid-2015. For Carrier Aggregation to work it must be enabled and configured at the cell site base station and a compatible handset must be available. The handsets will transmit and receive their LTE data on two different spectrum bands for the Inter-band solution. All handsets currently only operate in one mode, 700MHz, Cellular, PCS, AWS, or 2.5GHz.
Highlights by Carrier:
Canada: Rogers Wireless will have support for inter-band aggregation between their AWS spectrum and the paired blocks of 2.5GHz spectrum.
AT&T: Inter-band support in Release 11 for their Cellular and 700MHz spectrum, inter-band support to combine their AWS and Cellular spectrum, as well as configuration to support combining their PCS and 700MHz spectrum. All of the 700MHz band plans only include their 700B/C holdings. No 700MHz inter-operability.
USCellular: Inter-band support in Release 11 for Cellular and 700MHz (A/B/C). No support for PCS or AWS spectrum combinations
Clearwire: Intra-band support for the entire 2.5GHz band. China Mobile is also supporting this with an inter-band aggregation between 2.5GHz and their TDD 1.9GHz spectrum.
Sprint: Support in Release 12 for combining (intra-band)their holding across the PCS spectrum, including their G spectrum but not the un-auctioned H spectrum. No band support for their iDEN band or the 2.5GHz band.
T-Mobile: Support in Release 12 for intra-band in the AWS band and inter-band between AWS and PCS.
Verizon: Ericsson appears to be supporting Verizon's need to combine (inter-band) between AWS and 700MHz C. Not support for Verizon's Cellular or PCS holdings.
Dish: Release 12 support to combine their S band (AWS4) spectrum (inter-band) with the 700 MHz E holdings. This is the only aggregation scenerio for the US that combines FDD operation (AWS4) with TDD operation (700MHz E).
Posted during the 3GPP RAN Meeting on Dec 4-7, 2012 in Barcelona, Spain.
Customer Requirements for LTE Advanced Carrier Aggregation for Band 5 and Band 17. This appears to be supporting AT&T's need to aggregate carriers between their 700MHz (Band 17) and the Cellular band (Band 5). No mention of including the redefined WCS band. Could this be a sign that AT&T's growth plan for LTE will be to grow into the cellular spectrum first, and then to the WCS spectrum?
