Abstract
3rd Generation Partnership Project (3GPP) has recently completed the specification of the Long Term Evolution (LTE) standard. Majority of the world's operators and vendors are already committed to LTE deployments and developments, making LTE the market leader in the upcoming evolution to 4G wireless communication systems. Multiple input multiple output (MIMO) technologies introduced in LTE such as spatial multiplexing, transmit diversity, and beamforming are key components for providing higher peak rate at a better system efficiency, which are essential for supporting future broadband data service over wireless links. Further extension of LTE MIMO technologies is being studied under the 3GPP study item to meet the requirement of IMT-Advanced set by International Telecommunication Union Radiocommunication Sector (ITU-R). In this paper, we introduce various MIMO technologies employed in LTE and provide a brief overview on the MIMO technologies currently discussed in the LTE-Advanced forum.
Highlights
As multimedia communications become increasingly popular, mobile communications are expected to reliably support high data rate transmissions
3rd Generation Partnership Project (3GPP) has recently specified an Orthogonal Frequency Division Multiplexing (OFDM) based technology, Evolved Universal Terrestrial Radio Access (E-UTRA), for support of wireless broadband data service up to 300 Mbps in the downlink and 75 Mbps in the uplink [9]. (E-UTRA is known as LTE in the wireless industry.) In Long Term Evolution (LTE), Multiple input multiple output (MIMO) technologies have been widely used to improve downlink peak rate, cell coverage, as well as average cell throughput
For LTE downlink, the transmit diversity schemes can be applied to all the physical channels such as Physical Downlink Shared Channel (PDSCH), Physical Broadcast Channel (PBCH), Physical Control Format Indicator Channel (PCFICH), Physical Downlink Control Channel (PDCCH), and Physical Hybrid ARQ Indicator Channel (PHICH) while the other MIMO schemes are only applicable to PDSCH
Summary
As multimedia communications become increasingly popular, mobile communications are expected to reliably support high data rate transmissions. (E-UTRA is known as LTE in the wireless industry.) In Long Term Evolution (LTE), MIMO technologies have been widely used to improve downlink peak rate, cell coverage, as well as average cell throughput. To achieve this diverse set of objectives, LTE adopted various MIMO technologies including transmit diversity, single user (SU)-MIMO, multiuser (MU)-MIMO, closedloop rank-1 precoding, and dedicated beamforming [10,11,12,13]. The SU-MIMO scheme is specified for the configuration with two or four transmit antennas in the downlink, which supports transmission of multiple spatial layers with up to four layers to a given User Equipment (UE). We introduce various MIMO technologies employed in LTE, and provide a brief overview on the MIMO technologies currently discussed in the LTEAdvanced forum
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