 Building on our understanding that LTE advanced radio incorporates some very interesting and innovative improvements which increase the data rate that meets the IMT ITUR recommendations for the data rates that go up to 100 megabits or even 1 gigabits per second over radio in mobile environment. Carrier aggregation is the most important and the strongest feature that tries to implement the high data rate through cherry picking the desired frequency components which are offering the least interference at a particular moment. So we'll start with the background definition of carrier aggregation. We'd look at the concepts and we'll have an example. So carrier aggregation actually is meant to provide higher data rates by using, reusing, adopting, and adapting the frequencies which provide the least interference and maximum data rates. Carrier aggregation is based on the concept of spectrum allocation that is we can choose the frequencies in a given range of frequencies in a spectrum either in a frequency division duplex manner that is we can pair or we can bundle the bands together or we can take a certain band and we can take multiple time slots within that band that is time division duplex. Our scope essentially here is frequency division duplex. So the carrier aggregation actually means group or aggregate multiple carrier components and take raw bit streams from each frequency band. Consequently at the data link layer and subsequently at the network layer we are going to have the resultant accumulated bandwidth which is coming from individual frequency bands at the physical layer. Correspondingly we can get bandwidths up to 20 megahertz that is the maximum specification defined by the EU trend in LTEA starting from 1.4 megahertz down up right up to 20 megahertz. LTEA also prescribes that no more than five bands can be allocated it means with five bands theoretically speaking occupying a total of 20 megahertz bandwidth we can actually have up to 100 megahertz bandwidth available. Now depending upon the encoding scheme the corresponding scheme such as any smart keying like GMSK, QPSK, QOM emery techniques we can think about achieving a very very high data rate. Now this is a consolidated carrier aggregation diagram it's not actually the minimum side it only shows the maximum frequencies that can be incorporated each having up to 20 megahertz carrier bandwidth. Resultantly 100 megahertz can be allocated to a certain connection. Let's look at an example. This example is meant to highlight that we can choose from available spectrums depending upon our requirements at will it means there is no compulsion to choose from within a band or having only adjacent frequency components. As an example let's say that in 800 megahertz spectrum we take two components each having bandwidth of 20 megahertz in the 900 megahertz spectrum that is the initial GSM 900 megahertz band we have 10 megahertz spectrum that is 5 megahertz each and then in the 2.1 gigahertz spectrum we take another 10 megahertz that is two 10 megahertz bands for two five megahertz bands then we have the resultant of up to 60 megahertz it means what we have done here is we have taken four basically components two from the 800 megahertz band one from 900 megahertz and another one from 10 megahertz so using these four components we have achieved up to 60 megahertz we could go up to 100 megahertz but this is just an example that shows that we are not limited to choosing a certain number in a certain band as such. So this leads to certain spectrum allocation guidelines that is we can choose within one band the carriers or the carrier components which are adjacent to each other we could choose non-adjacent components within the same band or we could choose non-adjacent components in non-adjacent bands at will that is the third option so you see how much flexibility LTEA Eutran provides to us