Implementation of Coordinated MIMO-OFDM with Independent Local Oscillators

The performance of a coordinated multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system is limited by the presence of the local oscillator frequency mismatch, where each transmitter and receiver is driven by an independent local oscillator. This paper proposes a simple pilot assisted estimation of symbol-by-symbol carrier offset for every pair of the transmitter and the receiver to enable spatial multiplexing in a coordinated MIMO-OFDM system. The proposed method takes advantage of the characteristics of OFDM and the relative local oscillator stability assisted by the global positioning system receiver. The proposed method was implemented on an actual hardware platform demonstrating spectral efficiency improvement of four times using four transmitters and four receivers in 800MHz band.