AT&T is set to substantially complete LTE rollout by summer 2014, but today the carrier has added a milestone to LTE development. AT&T has become the first carrier to launch a LTE-Advanced network. At least, it's introduced elements that are used to identify LTE-Advanced. AT&T's LTE-Advanced network uses carrier aggregation to deliver downlink speeds up to (around) 100Mbps. AT&T's push for LTE-A development has been to allow them a more efficient utilization of the spectrum.
LTE-Advanced is a standard that was proposed as a 4G technology to the ITU in 2009. It was approved in March 2011. LTE-Advanced is was standardized as a major improvement to LTE technology. It is meant to correct and improve upon the short-falls of LTE (which is considered pre-4G technology.)
What is Carrier Aggregation?
Carrier Aggregation is the use of multiple spectrum allocations (whether contigious or not), to deliver faster speeds. It is one of the specifications to quality LTE-Advanced. With LTE, only one frequency is used to deliver data, at a time.
What devices are LTE-Advanced compatible?
Currently AT&T's Unite Hotspot is the only device to have access to this LTE-Advanced Network, however future handsets will also feature carrier aggregation support. The Galaxy S 5, and the Asus Padphone X will be some of the first handsets compatible with the LTE-A network.
What cities is LTE-Advanced currently available?
Their LTE-Advanced network has reportedly been lit up in cities across the nation, but only Chicago is confirmed.
What speeds can I expect with LTE-Advanced?
For now, you'll be able to expect similar speeds to speeds currently available, with a small speed boost. AT&T is deploying LTE-Advanced to help keep up with the rising use of LTE devices on it's network, and will focus on capacity before speed.
Is there anything else?
After carrier aggregation, AT&T will look to deploy LTE Advanced elements like heterogeneous networks (HetNets) and enhanced interference cancellation, further complying with LTE-Advanced set standards.