A time and frequency synchronization scheme for multiuser OFDM

We present a multiuser synchronization scheme for tracking the mobile's upl ink time and frequency offsets. It uses the redundancy introduced by the cy clic prefix and does not need additional pilots. We show performance result s of an orthogonal frequency division multiplexing (OFDM)-based radio inter face based on universal mobile telecommunication system (UMTS) parameters. For a UMTS-typical mobile channel environment, the performance of a coheren t system employing the scheme is virtually indistinguishable from the perfo rmance of a perfectly synchronized system, In a differentially modulated sy stem, synchronization errors decrease the system performance by about 0.7 d B compared to a perfectly synchronized system.