A practical equalizer for cooperative delay diversity with multiple carrier frequency Offsets

Cooperative transmission in wireless networks provides diversity gain in multipath fading environments. Among all the proposed cooperative transmission schemes, delay diversity has the advantage of needing less coordination and higher spectrum efficiency. However, in a distributed network, the asynchrony comes from both carrier frequency and symbol timing between the cooperating relays. In this paper, a minimum mean square error fractionally spaced decision feedback equalizer (MMSE-FS-DFE) is developed to extract the diversity with large multiple carrier frequency offsets, its performance approaches the case without multiple carrier frequency offsets. The front end design for the receiver in this scenario is discussed, and a practical frame structure is designed for carrier frequency offsets and channel estimation. A subblock-wise decision-directed adaptive least squares (LS) estimation method is developed to solve the problem caused by error in frequency offset estimation. The purpose of this paper is to provide a practical design for cooperative transmission (CT) with the delay diversity scheme.