LTE and the Evolution to 4G Wireless: Design and Measurement Challenges, 2nd Edition

Chapter 3

Physical Layer

3.1 Introduction to the Physical Layer

This chapter describes the LTE (E-UTRA) physical layer design. A general description of the LTE physical layer can be found in 36.201 [1] with the detailed design found in the 36.2XX technical specifications as follows:

36.211 Physical channels and modulation [2]

36.212 Multiplexing and channel coding [3]

36.213 Physical layer procedures [4]

36.214 Physical layer measurements [5].

Due to the complexity and scope of the physical layer no book of this length can begin to serve as a comprehensive reference. The goal here is to provide an introduction to the subject that will facilitate further study of the specifications themselves.

The physical layer covers the downlink transmission from the evolved node B (eNB) base transceiver station to the user equipment (UE), and the uplink transmission from the UE to eNB. As discussed in the previous chapter, 3GPP has selected a new OFDMA modulation scheme for the physical layer. This is one of the key differences between LTE and existing 3G systems such as UMTS and cdma2000, which are based on CDMA.

3.2 Physical Channels and Modulation

3.2.1 General Description of the Radio Interface

The physical layer supports two multiple access schemes: OFDMA on the downlink and SC-FDMA on the uplink. In addition, both paired and unpaired spectra are supported by using frequency division duplexing (FDD) and time division duplexing (TDD), respectively.

The LTE air interface needs to be described ...