Alamouti space time coded OFDM for underwater acoustic channels

Abstract

Abstract-Alamouti space-time coding is investigated in conjunction with OFDM modulation for high-rate underwater acoustic communications over time varying channels. The scheme's diversity gain is exploited using a low-complexity adaptive multichannel receiver. Performance is demonstrated using experimental data transmitted in a 10 kHz bandwidth over a 1 km shallow water channel south of the Martha's Vineyard island in New England. The two-transmitter Alamouti scheme shows the expected improvement over the same-rate single-transmitter scheme.

A simple design for joint channel estimation and data detection in an Alamouti OFDM system

“…The performance of the proposed detection algorithm, labeled Alamouti 2, is compared to the single-transmitter (SIMO) scheme using the same number of receive elements and the same transmission rate (15 kbps for = 512; 17 kbps for = 1024), as well as to that of Ref. [4], labeled Alamouti 1. Both the SIMO system and the system of Ref.…”

“…Both the SIMO system and the system of Ref. [4], rely on block-by-block adaptation and thus have better channel tracking capabilities than the pairby-pair adaptive algorithm. For this reason, the Alamouti 1 scheme outperforms the Alamouti 2 scheme.…”

“…Multi-carrier modulation and transmit diversity were considered in Ref. [4], which motivates the present work.…”

“…Such a receiver was discussed in Ref. [4]. Here, we proceed to develop a reduced-complexity receiver that exploits the Alamouti structure based on the assumption that…”

“…For underwater acoustic channels, Ref. [4] reports on an Alamouti STBC system and the application of a MIMO OFDM channel estimation algorithm enhanced by Doppler shift compensation [1]. In this framework, channel/phase estimation is ignorant of the Alamouti structure, i.e.…”