ABSTRACT
A significant number of codes are used for the implementation of CDMA, UMTS and LTE networks and for various purposes including multiple access (identification of users signals, base stations and nodes), for synchronisation, combating noise, interference and security. This chapter is a short summary of how the codes are generated and used in modern cellular communication systems. Perhaps one of the most widely used code in 3G and 4G networks belong to the family of maximum length sequences, the so-called m-sequences. The m-sequences behave as pseudo-noise sequences and exhibit random noise like behaviour. The chapter discusses first binary block codes and then progress to discussing binary and ternary Golay codes. All uplink physical channels on an activated uplink frequency are scrambled with a complex-valued scrambling code. Apart from the long scrambling sequence, short scrambling codes are also used for uplink scrambling.
