Design of PLL for Carrier Tracking in Uncertain OFDM Systems

Abstract In this paper we develop design procedures for carrier tracking loop for OFDM systems or other systems of blocked data. We show that in many cases tracking loop is better than AFC4-pilot to combat the phase noise problem. The derivation treats the general case of loop design in situations where phase error measurements are made infrequent enough to invalidate the traditional loop design methodology which is based on analog loop design. Our solution is general and includes arbitrary phase noise and additive noise spectrums, margins, uncertainty and loop delay. If the optimal loop does not meet the required margin constraints and uncertainties, we propose the use of the QFT synthesis procedure which we extend for this case. In addition, we give simple low order loop design procedure which may be sufficient in many cases. The case where pilot symbols are used is covered and we combine them for best performance. Finally, we show that a large improvement can be gained also in the phase change over the symbol.