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LTE for UMTS: Evolution to LTE-Advanced, 2nd Edition by Antti Toskala, Harri Holma

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Chapter 5

Physical Layer

Antti Toskala, Timo Lunttila, Esa Tiirola, Kari Hooli, Mieszko Chmiel and Juha Korhonen

5.1 Introduction

This chapter describes the physical layer of LTE, based on the use of OFDMA and SC-FDMA principles as covered in Chapter 4. The LTE physical layer is characterized by the design principle of not reserving dedicated resources for a single user; resource usage is based solely on dynamically allocated shared resources. This is analogous to resource usage in the internet, which is packet based without user-specific resource allocation. The physical layer of a radio access system has a key role of defining the resulting capacity and ends up being a focal point when comparing different systems in terms of expected performance. However, a competitive system requires an efficient protocol layer to ensure good performance all the way to the application layer and to the end user. The flat architecture adopted, covered in Chapter 3, also enables the dynamic nature of the radio interface as all radio resource control is located close to the radio in the base-station site. The 3GPP term for the base station used in rest of this chapter will be ‘eNodeB’ (similar to the WCDMA BTS term, which is ‘Node B’, where ‘e’ stands for ‘evolved’). This chapter first covers the physical channel structures and then introduces the channel coding and physical layer procedures. The chapter concludes with a description of physical layer measurements and device capabilities as well ...

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