Training sequence vs. cyclic prefix a new look on single carrier communication

Frequency domain equalization has gained a lot of attention in the last decade, mainly pushed by the OFDM (Orthogonal Frequency Division Multiplexing) communication scheme. It has been adopted, in various flavours, for, among others, Wireless Lans and xDSL. The technique is indeed leading to low complexity implementation, at the cost of a Cyclic Prefix, used to avoid Inter Block Interference (IBI). The idea has been adapted to single carrier communication, almost “as is”, yielding the same computational advantages and avoiding the high crest factor of OFDM. We will name this scheme CP-SC (Cyclic Prefix Single Carrier). We take a new look at this single carrier scheme, and, with a slight modification, show that the cyclic prefix can be implemented as a training sequence, and hence play two important roles : avoid IBI and help in synchronisation and channel estimation. The latter topic is of utter importance in fast fading situations (e.g. mobile). This new Training Aided Frequency Domain Equalized Single Carrier (we will name it TASC) scheme offers these advantages at the expense of only a small fraction of a dB (in terms of Eb No). All these arguments make TASC an interesting candidate in situations where multipath and fast fading are present, while in other situations it has hardly no drawback compared to CP-SC.