This paper presents an algorithm for joint estimation of carrier-frequency offset and timing offset for orthogonal frequency-division multiplexing (OFDM) systems in the tracking mode. The proposed weighted least-squares algorithm derives its estimates based on phase differences in the received pilot subcarrier signals between two symbols. Moreover, the optimal weights in two different channel conditions are derived. Both analysis and simulation show that the weighted least-squares algorithm can effectively and accurately estimate the carrier-frequency offset as well as the timing offset of OFDM signals in multipath fading channels.

Multicarrier systems have become popular for their spectral efficiency and robustness against frequency-selective fading. Multicarrier code-division multiple access (MC-CDMA) is a technique that combines the advantage of multicarrier modulation with that of code-division multiple access (CDMA) to offer reliable high-data-rate downlink cellular communication services. In this paper, we present the architecture of a downlink baseband transceiver using the MC-CDMA technology under the same bandwidth requirement and channel condition as the third-generation wideband CDMA system. In the transmitter, a scrambling code is applied in order to reduce the peak-to-average power ratio (PAPR) of the transmitter output. In the receiver, we use a joint weighted least-squares (WLS) synchronization error estimation algorithm and a novel channel estimator. Both algorithms greatly enhance the system error-rate performance, as indicated by functional simulation. Simulation results also verify maximum aggregate coded data rates of 5.4/10.8 Mbps from 32/64 users in mobile/stationary multipath fading channel with a 3/4 convolutional code, respectively

Absfracr-This paper presents an algorithm for joint ferences are then averaged among all pilot subcarriers or estimation of carrier frequency Offset and timing freover m w a l OFDM svmhok to =