CDMA-based analog network coding through interference cancellation for underwater acoustic sensor networks

Abstract

The performance of multi-hop underwater acoustic network is known to be limited by the long propagation delays and by the limited bandwidth of the underwater acoustic (UW-A) channel. Recent work on analog network coding (ANC) has shown that significant throughput gains can be achieved in multi-hop wireless networks. However, implementing ANC for UW-A communications is very challenging as the UW-A channel is severely affected by multipath. In this paper, we propose CE-CDMA, a collision-enabling direct-sequence code-division multiple-access scheme for multi-hop underwater acoustic sensor networks (UW-ASNs). In CE-CDMA two nodes, separated by two hops, are assigned the same code-division channel (i.e., spreading code) to communicate concurrently. The transmission of packets by the two nodes will therefore collide at the intermediate (relay) node. However, we show that by exploiting a priori information, i.e., the interfered packet previously received from one of the nodes, and an adaptive RAKE receiver that jointly estimates the two multipath-affected channels, the relay node can cancel the interference before decoding the packet of interest. Experiments demonstrate that for a 1 − 2 dB tradeoff in signal-to-noise ratio (SNR) the proposed scheme can potentially improve the channel utilization of a unidirectional multi-hop linear network by up to 50 %. We also outline the basic functionalities of a MAC protocol (CE-MAC) designed to support the proposed scheme.

Modeling Underwater Acoustic Channels in Short-range Shallow Water Environments

“…Multipath propagation can severely deteriorate the acoustic signal, as it generates inter-symbol interference (ISI) [11,12]. The multipath geometry depends on the link configuration.…”

Designing the Undersea Internet of Things (IoT) and Machine-to-Machine (M2M) Communications Using UnderWater Acoustic MIMO Networks

“…Second, extending the applicability and practicability of SE/EE trade-off curves to real UWA/MIMO networks, throughput can be used instead of capacity. Since the future research will focus on real UWA networks, the influence of the adopted modulations and coding schemes on the throughput reduction should be investigated studying the respective SE/EE trade-off curves either in shape or in maxima [65], [66]. Anyway, the application of SE/EE trade-off curves in real single-and multi-port…”

A hybrid MAC protocol with channel-dependent optimized scheduling for clustered underwater acoustic sensor networks

“…After a successful reception of the data packets, cluster head CH broadcasts a cumulative acknowledgment (CA) packet to acknowledge the reception of data packets. We avoid the use of individual acknowledgement of each data packet to minimize the control overhead by acknowledging the member nodes within a cluster with a single CA packet, as discussed in [3]. The received data packets are then gathered at the CH.…”

“…A number of MAC protocols have been proposed that aim at combating multipath, long propagation delay, and overall energy consumption in UW-ASNs [1,2,3,4]. The energy of the underwater acoustic (UW-A) modem's battery is limited and replacing and/or recharging the battery is in many cases not practical.…”