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

Chapter 2

Air Interface Concepts

This chapter covers the radio aspects of LTE, starting in Section 2.1 with an overview of the radio frequency (RF) specifications. Sections 2.2 and 2.3 describe the downlink and uplink modulation schemes in some detail and, finally, Section 2.4 examines the way in which LTE uses multi-antenna methods to improve performance.

2.1 Radio Frequency Aspects

The RF specifications for LTE are covered in two 3GPP technical specification documents: 36.101 [1] for the user equipment (UE) and 36.104 [2] for the base station (BS), which is known in LTE as the evolved node B (eNB) although the more generic term BS is more commonly used. One of the first things to note about LTE is the integration between the frequency division duplex (FDD) and time division duplex (TDD) radio access modes. In the previous Universal Mobile Telephone System (UMTS) specifications, which also supported FDD and TDD, the RF specifications for the UE FDD, UE TDD, base station FDD, and base station TDD modes were covered in separate documents. However, the early decision by 3GPP to fully integrate FDD and TDD modes for LTE has resulted in only one RF specification document each for the UE and the BS. With the higher level of integration between the two modes, the effort required to support them should be less than it was in the past.

The structure of 36.101 [1] for the UE follows the UMTS pattern of minimum requirements for the transmitter and receiver followed by performance requirements ...