Multiple Frequency Offsets Estimation and Compensation for Cooperative Networks

For a cooperative wireless network using delay diversity, the equivalent channel seen at the receiver is multipath and time-varying, as each transmitter has a local oscillator with a random frequency offset. The authors propose to use orthogonal frequency division multiplexing (OFDM) modulation, in order to efficiently implement equalization in the frequency domain; inter-carrier interference arising from multiple frequency offsets is instead compensated by a linear equalizer. For the estimate of the time-varying channel parameters a new technique was proposed that reduces the number of parameters to be estimated and exploits the multiple frequency-offsets.