Time and frequency synchronisation in tdma‐ofdm based high speed wireless local area networks

Abstract

Downlink synchronisation emr estimarors suited for OFDM-TDMA wireless LAN are presented. The focus is on the timing error estimator, which is of the Early-Late type and has a low complexity, making it attractive for high speed systems. It also allows a large sharing o f the computational burden with the fnquency ermr estimator. The estimator is presented and analysed. Simulations art performed to asses the pexfonnance of the synchronisation system over indoor channels.

Pilot-assisted maximum-likelihood frequency-offset estimation for OFDM systems

“…Padding more zeros in the sequence results in higher resolution at the expense of inducing higher computation complexity. As the spectrum is a real smooth function of , taking a derivative of with respect to and setting , we obtain (14) where is a polynomial of order . As mentioned before, in a noiseless environment, , the Fourier transform of , is a scaled version of the function , and all roots of are on the unit circle.…”

“…We notice that the solutions of ( 14) are the nonzero roots of the polynomial (17) On the other hand, (14) implies that the roots of satisfy the equation , where is the imaginary part of . This observation indicates that the nonzero roots of (the root of is undesired) are a subset of the roots of .…”