Interference Analysis in Time and Frequency Asynchronous Network MIMO OFDM Systems

It is well known that symbol timing offsets larger than the cyclic prefix as well as carrier frequency offsets between transmitter and receiver stations destroy the orthogonality among OFDM subcarriers and induce additional interference. In conjunction with MIMO transmission on frequency selective fading channels where different users interfere with each other, these effects strongly degrades the signal detection performance. In this paper we consider fully asynchronous spatially multiplexed transmission with different symbol timing and carrier frequency offsets on each transmitter-receiver link which appear in distributed MIMO systems with multiple users and base stations. We derive a factorized system model for signal transmission in frequency domain where the different effects of inter-carrier, inter-symbol and inter-block interference are separated and analyzed in terms of signal-to-interference-noise-ratio degradation. Finally, we evaluate the interference levels at a receiver station for different link-level as well as system-level simulation setups.