Chapter 21
Radio Frequency Aspects
21.1 Introduction
Radio Frequency (RF) signal processing constitutes the final interface between the baseband techniques described in earlier chapters and the transmission medium – the air. The RF processing presents its own unique challenges for practical transceiver design, arising in particular from the fact that the air interface is a shared resource between multiple RF carriers, each with their own assigned portion of spectrum. The RF transmitter must be designed in such a way as not only to generate a clean signal within the assigned spectrum portion, but also to keep Inter-Carrier Interference (ICI) within acceptable levels. The receiver likewise must reliably demodulate the wanted signal, in order to avoid requiring excessive energy to be transmitted, whilst also rejecting interference from neighbouring carriers. Performance requirements for these RF aspects aim to ensure that equipment authorized to operate on an LTE carrier meets certain minimum standards.
In general, the performance requirements for LTE transceivers are intended not to be significantly more complex than for UMTS1 in terms of implementation and testing. Consequently, many of the RF requirements for LTE are derived from those already defined for UMTS.
There are, however, a number of key differences between LTE and UMTS which affect the RF complexity and performance.
One such difference is the ...
