LTE-Advanced aims to support peak data rates of 1 Gbps in the downlink and 500 Mbps in the uplink. In order to fulfil such requirements, a transmission bandwidth of up to 100 MHz is required; however, since the availability of such large portions of contiguous spectrum is rare in practice, LTE-Advanced uses carrier aggregation of multiple Component Carriers (CCs) to achieve high-bandwidth transmission. Release 8 LTE carriershave a maximum bandwidth of 20 MHz, so LTE-Advanced supports aggregation of up to five 20 MHz CCs.
A second motivation for carrier aggregation is to facilitate efficient use of fragmented
spectrum, irrespective of the peak data rate.
A third motivation for carrier aggregation is support of heterogeneous networks. A
heterogeneous network deployment typically consists of a layer of high-power macrocells A third motivation for carrier aggregation is support of heterogeneous networks. A heterogeneous network deployment typically consists of a layer with at least one carrier being used by both layers. In such a deployment, transmissions from one cell can interfere strongly
with the control channels of another, thus impeding scheduling and signalling. Rather than
simply using separate carriers for the two layers, which would result in inefficient spectrum
usage, carrier aggregation enables multiple carriers to be used for a given layer, while
interference can be avoided by means of cross-carrier scheduling. Cross-carrier scheduling
allows the Physical Downlink Control Channel (PDCCH) on the CC of one serving cell to
schedule transmission resources on a CC of another serving cell of high-power macrocells.
A second motivation for carrier aggregation is to facilitate efficient use of fragmented
spectrum, irrespective of the peak data rate.
A third motivation for carrier aggregation is support of heterogeneous networks. A
heterogeneous network deployment typically consists of a layer of high-power macrocells A third motivation for carrier aggregation is support of heterogeneous networks. A heterogeneous network deployment typically consists of a layer with at least one carrier being used by both layers. In such a deployment, transmissions from one cell can interfere strongly
with the control channels of another, thus impeding scheduling and signalling. Rather than
simply using separate carriers for the two layers, which would result in inefficient spectrum
usage, carrier aggregation enables multiple carriers to be used for a given layer, while
interference can be avoided by means of cross-carrier scheduling. Cross-carrier scheduling
allows the Physical Downlink Control Channel (PDCCH) on the CC of one serving cell to
schedule transmission resources on a CC of another serving cell of high-power macrocells.
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