LTE by the 3GPP in LTE were originally

 LTE Overview LTE comprises the Evolved UMTS Terrestrial Radio Access (E-UTRA) air interface, which is a technology designed to combine high-data-rate, low-latency and packetoptimized radio access. In order to meet these requirements, important changes were required at the physical layer, for example, new modulation and coding schemes are used and the Transmission Time Interval (TTI) was reduced. In fact, many of the features included by the 3GPP in LTE were originally considered for “4th generation” cellular systems 19.  The media access scheme for LTE is Orthogonal Frequency Division Multiple Access (OFDMA) for downlink and Single Carrier FDMA (SC FDMA) for uplink with two possible modes of transmission: FDD and TDD. The motivation behind the election of SC-FDMA for the uplink is its low Peak-to-Average Power Ratio (PAPR) that reduces the quality requirement for mobile terminal amplifiers and, therefore, the mobile terminal’s cost. Additionally, advanced MIMO spatial multiplexing techniques, including (2 or 4) x (2 or 4) schemes for downlink and uplink, as well as multi-user MIMO are also supported. The resource allocation in the frequency domain takes place with a resolution of 180 kHz resource blocks both in uplink and downlink. The uplink user specific allocation is continuous to enable single carrier transmission while the downlink can use resource blocks freely from different parts of the spectrum. The LTE solution enables spectrum flexibility where the transmission bandwidth can be selected between 1.4 MHz and 20 MHz depending on the available spectrum. The 20 MHz bandwidth can provide up to 150 Mbps downlink user data rate with 2 × 2 MIMO, and 300 Mbps with 4 × 4 MIMO. The uplink peak data rate is 75 Mbps 20. LTE, DSRC and WiMAX all employ OFDMA and current best practices in multiple areas of their designs, including forward error correction, MIMO processing, and adaptive MAC operation. One reason for investigating use of LTE is its heritage in the cellular radio community, which has been successfully supporting ever-increasing data rates in highly mobile environments for over a decade. In contrast, the DSRC standard has evolved from the wireless LAN community, which has not previously supported mobile data. Clearly, both standards will likely improve over time. B


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