title: Receiver design for spread-spectrum communications with a small spread in underwater clustered multipath channels.
abstract: This paper studies a direct-sequence spread-spectrum communication system with a small spreading factor (e.g., a single digit) in underwater acoustic multipath channels. Exploiting the channel characteristics that the propagation paths can be grouped into distinct clusters, a receiver with a set of parallel branches is proposed, where per-survivor processing (PSP) is applied on each branch to deal with the signal from one cluster while explicitly treating the signals from other clusters as structured interference. As such, it overcomes a major limitation of an existing PSP based receiver [Zhou, Morozov, and Preisig, J. Acoust. Soc. Am. 133, 2746-2754 (2013)], avoiding exponential complexity increase when the spreading factor decreases. On the first branch, joint channel estimation and interference cancellation are performed based solely on the survivor paths. On the other branches, joint channel estimation and interference cancellation are carried out based on the survivor paths and the tentatively decoded data. The bit log-likelihood ratios from different branches are combined for channel decoding. Performance results based on simulations and collected data sets validate the superior performance of the proposed receiver over the conventional RAKE receiver, which is effective only when the spreading factor is large.
authors.affiliation: Key Laboratory of Underwater Acoustic Communication and Marine Information Technology (School of Information Science and Engineering, Xiamen University), Ministry of Education, Xiamen 361005, China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Kuai
authors.affiliation: Department of Electrical and Computer Engineering, University of Connecticut, 371 Fairfield Way U-4157, Storrs, Connecticut 06269, USA.
authors.forename: Shengli
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Department of Electrical and Computer Engineering, Michigan Technological University, 1400 Townsend Drive, Houghton, Michigan 49931, USA.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Key Laboratory of Underwater Acoustic Communication and Marine Information Technology (School of Information Science and Engineering, Xiamen University), Ministry of Education, Xiamen 361005, China.
authors.forename: En
authors.initials: E
authors.lastname: Cheng