Medium access control for underwater acoustic sensor networks with MIMO links

The requirements of multimedia underwater monitoring applica-tions with heterogeneous traffic demands in terms of bandwidth and end-to-end reliability are considered in this article. To address these requirements, a new medium access control protocol named UMIMO-MAC is proposed. UMIMO-MAC is designed to i) adap-tively leverage the tradeoff between multiplexing and diversity gain according to channel conditions and application requirements, ii) select suitable transmit power to reduce energy consumption, and iii) efficiently exploit the UW channel, minimizing the impact of the long propagation delay on the channel utilization efficiency. To achieve the objectives above, UMIMO-MAC is based on a two-way handshake protocol. Multiple access by simultaneous and co-located transmissions is achieved by using different pseudo or-thogonal spreading codes. Extensive simulation results show that UMIMO-MAC increases network throughput, decreases channel access delay, and decrease energy consumption compared with ex-isting Aloha-like MAC protocols for UW-ASNs

Cellular Underwater Wireless Optical CDMA Network: Potentials and Challenges

Underwater wireless optical communications is an emerging solution to the expanding demand for broadband links in oceans and seas. In this paper, a cellular underwater wireless optical code division multiple-access (UW-OCDMA) network is proposed to provide broadband links for commercial and military applications. The optical orthogonal codes (OOC) are employed as signature codes of underwater mobile users. Fundamental key aspects of the network such as its backhaul architecture, its potential applications and its design challenges are presented. In particular, the proposed network is used as infrastructure of centralized, decentralized and relay-assisted underwater sensor networks for high-speed real-time monitoring. Furthermore, a promising underwater localization and positioning scheme based on this cellular network is presented. Finally, probable design challenges such as cell edge coverage, blockage avoidance, power control and increasing the network capacity are addressed.Comment: 11 pages, 10 figure

Routing Protocols for Underwater Acoustic Sensor Networks: A Survey from an Application Perspective

Underwater acoustic communications are different from terrestrial radio communications; acoustic channel is asymmetric and has large and variable end‐to‐end propagation delays, distance‐dependent limited bandwidth, high bit error rates, and multi‐path fading. Besides, nodes’ mobility and limited battery power also cause problems for networking protocol design. Among them, routing in underwater acoustic networks is a challenging task, and many protocols have been proposed. In this chapter, we first classify the routing protocols according to application scenarios, which are classified according to the number of sinks that an underwater acoustic sensor network (UASN) may use, namely single‐sink, multi‐sink, and no‐sink. We review some typical routing strategies proposed for these application scenarios, such as cross‐layer and reinforcement learning as well as opportunistic routing. Finally, some remaining key issues are highlighted

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

This review paper tries to assess the spectral-efficient (SE) and energy-efficient (EE) performance of underwater acoustic multiple-input multiple-output (UWA/MIMO) networks. Since UWA/MIMO networks define the cutting-edge communications platform of the future’s undersea IoT and M2M networks, the factors that influence their SE and EE performance are thoroughly examined in this paper.The contribution of this paper is three-fold. First, the performance of UWA/MIMO networks is studied with regard to appropriate transmission, SE and EE metrics. The SE and EE performance of these networks drastically depends on the used frequency band, the transmitted power, the MIMO scheme properties, the power consumption profile of the deployed UWA system equipment and the topological characteristics of MIMO configurations. In order to achieve the transition from traditional UWA single-input single-output (UWA/SISO) networks to UWA/MIMO networks, a new singular value decomposition MIMO (SVD/MIMO) module, which also permits the theoretical computation of the aforementioned transmission, SE and EE metrics in UWA networks, is first presented. Second, based on the aforementioned transmission, SE and EE metrics, a SE/EE trade-off relation is proposed in order to investigate the combined SE and EE performance of UWA/MIMO networks. On the basis of this SE/EE trade-off relation, it is first revealed that today’s UWA system equipment cannot support the further IoT broadband exploitation with satisfactory EE performance. Third, the concepts of multi-hop UWA communications and standard UWA topologies are outlined and promoted so that further SE and EE improvement can concurrently occur. These concepts are quantitatively validated by the SE and EE metrics as well as the SE/EE trade-off curves.Based on the findings of this paper, suitable transmitted power levels and better design of UWA/MIMO configurations are promoted so that: (i) SE and EE requirements can be satisfied at will; and (ii) EE-oriented high-bitrate M2M communications network design can be established.Citation: Lazaropoulos, A. G. (2016). "Designing the Undersea Internet of Things (IoT) and Machine-to-Machine (M2M) Communications Using UnderWater Acoustic MIMO Networks." Trends in Renewable Energy, 2(1), 13-50. DOI: 10.17737/tre.2016.2.1.001

Reconfigurable Intelligent Surfaces in Challenging Environments: Underwater, Underground, Industrial and Disaster

Reconfigurable intelligent surfaces (RISs) have been introduced to improve the signal propagation characteristics by focusing the signal power in the preferred direction, thus making the communication environment "smart". The typical use cases and applications for the "smart" environment include beyond 5G communication networks, smart cities, etc. The main advantage of employing RISs in such networks is a more efficient exploitation of spatial degrees of freedom. This advantage manifests in better interference mitigation as well as increased spectral and energy efficiency due to passive beam steering. Challenging environments comprise a range of scenarios, which share the fact that it is extremely difficult to establish a communication link using conventional technology due to many impairments typically associated with the propagation medium and increased signal scattering. Although the challenges for the design of communication networks, and specifically the Internet of Things (IoT), in such environments are known, there is no common enabler or solution for all these applications. Interestingly, the use of RISs in such scenarios can become such an enabler and a game changer technology. Surprisingly, the benefits of RIS for wireless networking in underwater and underground medium as well as in industrial and disaster environments have not been addressed yet. In this paper, we aim at filling this gap by discussing potential use cases, deployment strategies and design aspects for RIS devices in underwater IoT, underground IoT as well as Industry 4.0 and emergency networks. In addition, novel research challenges to be addressed in this context are described.Comment: 16 pages, 13 figures, submitted for publication in IEEE journa