3.1 Physical Layer Overview

The long term evolution (LTE) physical layer is targeted to provide improved radio interface capabilities between the base station ^[1] and user equipment (UE) compared to previous cellular technologies like the universal mobile telecommunications system (UMTS) or high-speed downlink packet access (HSDPA).

According to the initial requirements defined by the 3rd Generation Partnership Project (3GPP; 3GPP 25.913), the LTE physical layer should support peak data rates of more than 100 Mb/s over the downlink and 50 Mb/s over the uplink. A flexible transmission bandwidth ranging from 1.25 to 20 MHz will provide support for users with different capabilities. These requirements will be fulfilled by employing new technologies for cellular environments, such as orthogonal frequency division multiplexing (OFDM) or multiantenna schemes (3GPP 36.201).

Additionally, channel variations in the time/frequency domain are exploited through link adaptation and frequency-domain scheduling, giving a substantial increase in spectral efficiency. In order to support transmission in paired and unpaired spectra, the LTE air interface supports both frequency division duplex (FDD) and time division duplex (TDD) modes.

This chapter presents a detailed description of the LTE radio-interface physical layer. For that purpose, this section provides an introduction to the physical layer, focusing on the physical resource structure and the set of procedures defined within this layer. Link adaptation techniques, including adaptive modulation, channel coding, and channel aware scheduling, are described in Section 3.2. The topic of multiple antenna...