Patent ID: 7352691
Filing Date: 2008-04-01
Classification: H04L

Abstract:
1. An orthogonal frequency division multiplexing (OFDM) communications system, comprising: an OFDM transmitter operative to transmit at least one data packet, the data packet comprising a predetermined data pattern within a preamble field, the OFDM transmitter being further operative to convert the data packet to a plurality of data packet sub-signals, each sub-signal corresponding to a respective sub-carrier frequency, to map the sub-signals to corresponding phases, to convert the sub-signals from the frequency domain to the time domain, and to convert the sub-signals from digital to analog form for subsequent transmission at the respective sub-carrier frequencies; and an OFDM receiver operative to receive the transmitted data packet sub-signals, to convert the received sub-signals from analog to digital form, to convert the received sub-signals from the time domain to the frequency domain, and to detect a phase of the pre-coded preamble data pattern within each received sub-signal, wherein the OFDM transmitter includes a preamble pre-coder operative to calculate first and second cumulative phases of sub-carriers corresponding to the predetermined preamble data pattern, and wherein the OFDM receiver includes a preamble detector operative to calculate first and second differences between adjacent ones of the second cumulative sub-carrier phases, thereby making the detection of the phase of the pre-coded preamble data pattern insensitive to phase offset misalignment between the transmitted and received data packet sub-signals.