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Carrier Aggregation for 5G

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- Overview

Carrier Aggregation (CA) is a technique used in LTE-Advanced to increase the peak data rate (i.e., maximum available speed) of a 4G LTE network. By aggregating multiple channels together a mobile network operator can increase the total available bandwidth of a single transmission, and thereby increase the bit rate and capacity of the network. Before LTE-A, a mobile network operator could only use additional LTE bands to increase capacity (i.e., total number of users), by distributing traffic across multiple bands. While this is an effective way to provide more airtime to any one particular user and thereby improving available data rates during busy periods, it does not increase the peak data rate. With radio spectrum a rare commodity, CA has also helped to utilise smaller spectrum allotments which only support smaller channel widths and where traditional LTE would lead to very low peak data rates.

The bands used by mobile carriers are numbered sequentially and represent “blocks” of a frequency range. LTE supports different channel bandwidths and as a result a different number of resource blocks can be supported. A band can be shared by several carriers, or it may be assigned exclusively to one cellular carrier. In addition, a frequency range may be comprised of multiple bands; for instance, 700 MHz includes LTE bands 12, 13, 17 (and more) used in the U.S. and Canada. 

To adequately meet customers’ different needs, cell phone carriers have several bands from high to low frequencies. For example, AT&T offers a range of frequencies from 2300 MHz, which is designed for densely populated urban areas; to 700 MHz, which performs better over long distances in rural areas. A variety of frequencies and bands are needed so each carrier can provide the best cellular coverage and capacity to all of their mobile subscribers.



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