This is purely my personal recoding of Carrier Aggregation just based on what I observe in the industry and personal communication with many developers from various area (UE maker, Equipment Vendor, Chipset Maker etc). If you want to trace more formal/official tracking, I would recommend to refer to http://www.3gpp.org/lte-advanced or each 3GPP 36.xxx document. I decided to post this section to give you some practical idea on how a new technology/feature is adopted and implemented in reality. You might have seen some cases where a new technology sounded like a science fiction and you thought it would never come true, but you see real implementation of the technology much sooner than you imagined. Also you might have seen
a lot of cases where everybody says it would come out 'TOMORROW', but in reality it would take several years (not 'tomorrow) before you see real implementation in the market.
- I start getting many questions from some UE makers asking about Carrier Aggregation development/testing and start posting this page on Apr 2012. (Of course, 3GPP specification on initial LTE-Advanced has been done at least an year ago).
- Early 2012, Qualcomm did a OTA demo for LTE-Advanced. (See MWC 2012 LTE Advanced HetNets Demo)
- In MWC 2013 (Feb 2013), some equipment vender and UE maker shows LTE-Advanced Demo with some prototype phone. This implies at least in a very limited rage, LTE-Advanced has been implemented in full protocol stack.
- As of now (July 2013), it seems that every chipset maker claims that they support Carrier Aggregation and almost every UE maker claim that they will release Carrier Aggregation UE soon (at least, as soon as Network Operator start deploying carrier aggregation capability). According to Reference ,
there should be a UE available in the market supporting Carrier Aggregation by now. According to Press Release from SK Telecom (http://www.sktelecom.com/), the network operator launched Carrier Aggregation Service as of Jun 26,2013. But I haven't seen yet any real phone with Carrier Aggregation.
- Around the end of Aug and early Sep in 2013, I start seeing some reports about user experience with LTE-A being serviced in Korea. Most of UE makers in Korea released UEs with LTE-A capability. However the initial reports were not so positive. They are saying "The performance (mainly throughput) is not as high as they expected" and in some cases "they see even poorer
performance than the single carrier". This implies that simply adding additional carrieron UE and eNB does not guarantee the expected performance expansion. They should do a lot of effors to optimize various factors to push up the performance as close as possible to the expected level
- Around the early Nov 2013, I personally created a full stack protocol test case which work with SamSung Galaxy IV being used in South Korea. It support Band 3-5 carrier combination and 10 Mhz System Bandwith on each carrier. For now, I just implemented basic feature of Carrier aggregation to achieve PHY layer max throughput and haven't implemented/tested the other details of LTE advanced
feature (e.g, PUCCH format 3, CSI, Handover etc).
- Feb 2014, World First 3CC Carrier Aggregation was demoed. (Huawei and LG Uplus Demo World’s First Three-Carrier Carrier Aggregation for 450 Mbps LTE-Advanced at Mobile World Congress 2014)
- Mar 2014, AT&T started servicing Carrier Aggregation in Chicago (AT&T lights up LTE Advanced carrier aggregation in Chicago, other markets). I think this is the first Carrier Aggregation Deployment in North America.
- Jul 2014, it is rumorred that some chipset makers and a test equipment vendor start testing 3CC Carrier Aggregation
- Jan 2015. SamSung announced the release of the first 3CC CA UE with 10+10+20 Mhz Triband
- Feb 2015. I got the chance to play with a pre-commericial UE that is supporting FDD 3CC CA. I got the max PHY/MAC throughput with bandwidth combination of 20+20+10. (The device supports band combination of CA_1A_5A_7A, so 20+20+10 is the maximum aggregated bandwidth)
- Mar 31, 2015. the network operator KT and mobile manufacturer SamSung did the demo for TDD 9 CC CA (Netmanias Interview with KT at MWC 2015: KT's demonstrations of LTE TDD (9-carrier CA, LTE-UL/DL CA and triple mode femto)
- Oct 2015, I personally had chance to try with 3CC MIMO(20+20+10) and achieve 360 Mbps throughput using the test setup shown here.
- Feb 2016, Qualcomm with Anritsu Protocol tester demoed 1Gbps throughput with 3 CA in 4x4 MIMO at MWC
- Apr 2016, Qualcomm announced solution supporting 1Gbps throughput with LTE Adv/LTE Adv Pro. See Delivering on the LTE Advanced promise.
- Aug 2016, I had the first hand experience of trying near 1Gbps UE (Cat 16) with 3CA (4x4,4x4,4x2) and confirmed around 970 Mbps throughput.
 World’s First Mobile Device with LTE Advanced Carrier Aggregation Powered by the Qualcomm® Snapdragon™ 800 Processor.
 LTE-A Carrier Aggregation Enhancements in Release 11