Method and apparatus for channel smoothing and estimation in OFDM system

摘要

Methods and apparatus are provided for receiving packets on a channel of an Orthogonal Frequency Division Multiplexing (OFDM) system. A time shift value for a packet is estimated using a channel estimation and an FFT size. A synchronization position of the packet on a channel is adjusted using the estimated time shift value, and a filter is applied to the adjusted channel to generate a smoothed channel estimate. Alternatively, a channel with a corrected packet synchronization position is estimated, and a smoothed channel is estimated by applying a filter to the estimated channel. Packets are received on the channel, at a receiver of the OFDM receiving apparatus, in accordance with the estimated smoothed channel.

主权项

1. A method for receiving packets on a channel of an Orthogonal Frequency-Division Multiplexing (OFDM) system at an OFDM receiving apparatus, the method comprising the steps of:
estimating a time shift value for a packet using channel estimation and a Fast Fourier Transform (FFT) size; adjusting a synchronization position of the packet on a channel using the estimated time shift value to generate an adjusted channel; applying a filter across sub-carriers of the adjusted channel to generate a smoothed channel estimate; and receiving, at a receiver of the OFDM receiving apparatus, packets on the channel in accordance with the smoothed channel estimate, wherein the filter comprises a Finite Impulse Response (FIR) filter, wherein a length of the FIR filter is based on a Signal to Noise Ratio (SNR) estimate for the channel, and wherein a short-length FIR filter is applied when the SNR estimate is greater than or equal to 12 dB, a long-length FIR filter is applied when the SNR estimate is less than or equal to 3 dB, and a medium-length FIR filter is applied when the SNR estimate is greater than 3 dB and less than 12 dB.