Performance Evaluation of MIMO OFDM Systems in On-Ship Below-Deck Environments

Below-deck compartments on naval vessels provide a challenging environment for wireless networks. The metallic walls of the compartments produce multiple reflections that can degrade signal integrity. Between compartments, the metal bulkheads impede the propagation of electromagnetic waves, limiting network connectivity. Orthogonal frequency-division multiplexing (OFDM) is proposed to mitigate the effects of intersymbol interference (ISI) caused by multiple reflections. Additionally, the use of multiple antennas for channel diversity has shown to improve communications reliability and capacity. Single and multiantenna OFDM physical layers were tested within several below-deck spaces aboard Thomas S. Gates (CG 51), a decommissioned Ticonderoga-class US Navy cruiser. Measurements were taken with four OFDM-based schemes typical of current-generation Wireless Local Area Network (WLAN) technologies. The performance of multiantenna signaling techniques, including 2 × 2 Alamouti space-time coding and 2 × 2 multiple-input-multiple-output spatial multiplexing (MIMO-SM), were compared to the performances of 1 × 2 maximal ratio combining (MRC) and a conventional single-input-single-output (SISO) system. Results indicate that the tested MIMO techniques can approximately double the channel capacity. Throughput as high as 36 Mb/s was achieved in conventional situations where SISO links only admitted rates of 18 Mb/s.