A Zipper OFDM Multiple-Antenna Technique for Interleaved-FDD Cellular Communication Systems

This paper investigates the application of Zipper orthogonal frequency-division multiplexing (OFDM), which is a frequency-domain duplexing technique based on interleaving subcarriers, to multiple-antenna cellular communications. By studying the Cramer-Rao lower bound as well as the performance of a minimum-mean-square-error-based interpolator, we show that the interleaved subcarriers make it possible for the base station to obtain accurate instantaneous downlink channel state information (CSI) from uplink channel measurements. However, the interleaved uplink and downlink subcarriers could introduce interference leakage when the intersubcarrier orthogonality is destroyed in multiple-cell environments. We address this issue by analyzing the uplink-to-downlink power leakage and show that with proper system configuration, such interference only has a marginal effect in typical land mobile radio environments. Finally, by considering maximum ratio transmission as an example, we demonstrate the benefit of knowing instantaneous downlink CSI in multiple-antenna Zipper OFDM systems.