Frequency offset tracking for MIMO OFDM systems using pilots

This paper presents an analysis of frequency offset estimation in MIMO OFDM systems. Tracking of frequency offsets is often aided by pilots transmitted in the data payload of a packet. The extension to multiple antenna OFDM systems means that spatial beamforming will occur when transmitting pilots from all antennas simultaneously, which can reduce the robustness of frequency offset estimation. We present a thorough analysis of the spatial beamforming problem and show how the spatial correlation of the MIMO channel impacts the performance. Simulation results are presented for measured channels recorded in an office environment, which agree well with the theoretical results.