Physical Layer Considerations for Cognitive Radio: Synchronization Point of View

In this paper, we briefly describe four modulation schemes (Orthogonal Frequency Division Multiplexing (OFDM), DFT-spread OFDM, Constant Envelope OFDM (CEOFDM)and Filter Bank Multicarrier (FBMC)) for Cognitive Radios (CR) in white space. In the first part, we give a short overview of the main signal processing blocks and signal properties. Then, we compare them by means of sensitivity to various synchronization errors such as timing error, frequency mismatch, phase noise and IQ-imbalance. These errors can be caused by either non-ideal analog components, movement of the transceiver or imperfect synchronization. Each synchronization error is examined separately; the performance is verified by means of bit error rates. Each modulation has a different sensitivity for a given type of synchronization error, which has to be taken into account when choosing the most suitable modulation scheme for a given application.