Chapter 18
Uplink Transmission Procedures
18.1 Introduction
In this chapter two procedures are explained which are fundamental to the efficient operation of the LTE uplink: Timing control is essential for the orthogonal uplink intra-cell multiple access scheme, while power control is important for maintaining Quality-of-Service (QoS), ensuring acceptable User Equipment (UE) battery life and controlling inter-cell interference.
18.2 Uplink Timing Control
18.2.1 Overview
As explained in Chapters 14 and 16, a key feature of the uplink transmission scheme in LTE is that it is designed for orthogonal multiple access in time and frequency between the different UEs. This is fundamentally different from WCDMA, in which the uplink transmissions are non-orthogonal; in WCDMA, from the point of view of the multiple access, there is therefore no need to arrange for the uplink signals from different UEs to be received with any particular timing at the NodeB. The dominant consideration for the uplink transmission timing in WCDMA is the operation of the power control loop, which was designed (in most cases) for a loop delay of just one timeslot (0.666 ms). This is achieved by setting the uplink transmission timing as close as possible to a fixed offset relative to the received downlink timing, without taking into account any propagation delays. Propagation delays in uplink and downlink are absorbed at the NodeB, by means of reducing the time spent measuring the Signal-to-Interference ...
