Maxlinear, Inc.

Roger Cheng

Rama Akella

Ramakrishna Akella

A method and an apparatus are provided in an OFDM receiver for detecting and compensating for long echo. The method comprises a first pilot tone interpolation mechanism and a first window placement to filter a received OFDM symbol, a long echo channel detection coupled with a second pilot tone interpolation mechanism, a pre-echo and post-echo detection wherein the pre-echo condition is associated with a second new window placement, and both pre-echo and post-echo conditions place two time windows around a first peak channel response and a second peak channel response for channel estimation. The long echo is estimated by obtaining power spectra of a subset of subcarriers in one OFDM symbol, performing an inverse Fourier transform on the power spectra and determining the long echo by measuring the time between two peaks in the power profile.

Long echo detection and channel estimation for OFDM systems

A method for performing channel estimation of an OFDM channel includes, in part, interpolating pilots for sub-channels positioned within a first range of an OFDM symbol, and estimating frequency response of sub-channels positioned within a second range of the OFDM symbol. The first range is defined by subchannels positioned substantially away from channel edges and the second range is defined by subchannels positioned substantially near channel edges. The method optionally includes transforming the pilots from frequency domain into the time-domain, time-domain windowing to obtain a channel impulse response having a multitude of discrete values, estimating the discrete values within the channel impulse response; and transforming the channel impulse response to the frequency domain.

Edge MMSE filters

An efficient channel estimation system and method provides good performance under high Doppler conditions and is suitable for OFDM systems such as DVB-T. A number of different pilot interpolations techniques enable the estimation of channel for the OFDM systems. For 2and 4modes, the channel is estimated using the preceding symbol, the present symbol, and two succeeding symbols. For an 8mode, only one future symbol is used to estimate the channel.

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Hong Kong, China

Roger Cheng