Precoding Assisted Blind CFO Estimation in Cooperative SFBC-OFDM Channels with Transmitter/Receiver IQ Imbalances

In a distributed cooperative environment, synchronization is a major issue. Especially when OFDM is employed in the physical layer, frequency offset synchronization is of great significance. In addition, transmitter and receiver IQ imbalances are known to be important implementation issues in OFDM systems. In this paper, a novel precoding strategy is proposed that enables blind estimation of carrier frequency offsets (CFOs) of each transmitter (separately) in cooperative scenario when the SFBC OFDM is employed in the physical layer, even when the transmitter and receiver IQ imbalances are present, and the channel is frequency selective. This non-redundant precoding strategy involves multiplication of the symbols to be transmitted by a random phase precoding sequence, and results in no loss in rate or bandwidth. Computer simulations are presented to demonstrate the effectiveness of the algorithm.