CTH15-4: Multiple Frequency Offset Compensation in Cooperative Wireless Systems

Multipath fading can be effectively combatted in wireless networks of single-antenna nodes by employing cooperative transmission techniques. In a wide variety of these cooperative techniques, multiple nodes encode a common data stream and then simultaneously put a signal onto the physical channel to exploit spatial diversity in the channel. For such a cooperative system, often it is difficult or undesirable from a complexity perspective to accurately lock the multiple transmitting nodes to a common oscillator, and thus the problem arises of multiple mismatches between the local oscillators of the transmit nodes and that of the receiver. Previously, such a situation has only been addressed through standard channel estimation; however, such techniques are not effective except for very small oscillator offsets. Here, a novel minimum mean square error (MMSE) decision feedback equalizer (DFE) that explicitly accounts for the frequency offsets is proposed for the receiver, and its performance is compared to standard approaches.