Bit Error Rate Calculation for OFDM with Synchronization Errors in Time and Frequency Selec.pdfVIP

Bit Error Rate Calculation for OFDM with Synchronization Errors in Time and Frequency Selective Fading Channels Marco Krondorf and Gerhard Fettweis Vodafone Chair Mobile Communications Systems, Technische Universita?t Dresden, D-01062 Dresden, Germany {krondorf,fettweis}@ifn.et.tu-dresden.de, http://www.ifn.et.tu-dresden.de/MNS Abstract— In this paper we present an analytical approach to evaluate the bit error rate (BER) of OFDM systems subject to carrier frequency offset (CFO) and channel estimation error in Rayleigh flat fading as well as in time and frequency selective fading channels. Based on correct modeling of the correlation between channel estimates and received signals with carrier frequency offset, the bit error rate can be numerically evaluated by averaging bit error rates on different subcarriers using an analytical expression of double integrals. The results illustrate that the analysis can approximate the simulative performance very accurately if the power delay profile of fading channels and carrier frequency offset are known. I. INTRODUCTION Orthogonal Frequency Division Multiplexing (OFDM) is a widely applied technique for wireless communications, which enables simple one-tap equalization by cyclic prefix inserta- tion. Conversely, the sensitivity of OFDM systems to carrier frequency offset (CFO) is higher than that of single-carrier systems. In present OFDM standards, such as IEEE802.11a/g or DVB-T, preamble (or pilots) are used to estimate and compensate the carrier frequency offset (CFO) and channel impulse response but after the CFO estimation and compen- sation, the residual carrier frequency offset still destroys the orthogonality of the received OFDM signals and the channel estimates, which worsen further the bit error rate of OFDM systems during the equalization process. In the literature, the effects of carrier frequency offset on symbol error rate are mostly investigated under the assumption of perfect channel knowledge. The papers [6] an