Blind Estimation of Maximum Delay Spread in OFDM Systems

We present a new method of estimating the maximum delay spread of a channel in an OFDM system. The method differs from other approaches because it uses all active OFDM subcarriers (pilot and data) and therefore avoids the aliasing problem arising from the exclusive usage of pilot subcarriers. The method considers the transmitted data as a random probe signal for obtaining characteristics of a channel. Although the data content is not known at the receiver, it turns out that useful second order statistics can be extracted, from which the maximum delay spread is estimated. The method is shown to be robust to noise and Doppler spread.