An Overview of Next-Generation Underwater Target Detection and Tracking: An Integrated Underwater Architecture <s> B. SOFTWARE-DEFINED UNDERWATER NETWORK (SDUN) <s> Abstract Underwater communication systems have drawn the attention of the research community in the last 15 years. This growing interest can largely be attributed to new civil and military applications enabled by large-scale networks of underwater devices (e.g., underwater static sensors, unmanned autonomous vehicles (AUVs), and autonomous robots), which can retrieve information from the aquatic and marine environment, perform in-network processing on the extracted data, and transmit the collected information to remote locations. Currently underwater communication systems are inherently hardware-based and rely on closed and inflexible architectural design. This imposes significant challenges into adopting new underwater communication and networking technologies, prevent the provision of truly-differentiated services to highly diverse underwater applications, and induce great barriers to integrate heterogeneous underwater devices. Software-defined networking (SDN), recognized as the next-generation networking paradigm, relies on the highly flexible, programmable, and virtualizable network architecture to dramatically improve network resource utilization, simplify network management, reduce operating cost, and promote innovation and evolution. In this paper, a software-defined architecture, namely SoftWater, is first introduced to facilitate the development of the next-generation underwater communication systems. More specifically, by exploiting the network function virtualization (NFV) and network virtualization concepts, SoftWater architecture can easily incorporate new underwater communication solutions, accordingly maximize the network capacity, can achieve the network robustness and energy efficiency, as well as can provide truly differentiated and scalable networking services. Consequently, the SoftWater architecture can simultaneously support a variety of different underwater applications, and can enable the interoperability of underwater devices from different manufacturers that operate on different underwater communication technologies based on acoustic, optical, or radio waves. Moreover, the essential network management tools of SoftWater are discussed, including reconfigurable multi-controller placement, hybrid in-band and out-of-band control traffic balancing, and utility-optimal network virtualization. Furthermore, the major benefits of SoftWater architecture are demonstrated by introducing software-defined underwater networking solutions, including the throughput-optimal underwater routing, SDN-enhanced fault recovery, and software-defined underwater mobility management. The research challenges to realize the SoftWater are also discussed in detail. <s> BIB001 </s> An Overview of Next-Generation Underwater Target Detection and Tracking: An Integrated Underwater Architecture <s> B. SOFTWARE-DEFINED UNDERWATER NETWORK (SDUN) <s> There is an emerging need for high-rate underwater acoustic (UW-A) communication platforms to enable a new generation of underwater monitoring applications including video streaming. At the same time, modern UW-A communication architectures need to be flexible to adapt and optimize their communication parameters in real time based on the environmental conditions. Existing UW-A modems are limited in terms of achievable data rates and ability to adapt the protocol stack in real time. To overcome this limitation, we present the design, implementation, and experimental evaluation of a new high-rate software-defined acoustic modem (SDAM) with real-time adaptation capabilities for UW-A communications. We introduce new physical-layer adaptation mechanisms that enable either joint adaptation of communication parameters such as modulation constellation and channel coding rate or seamless switching between different communication technologies such as orthogonal-frequency-division-multiplexing and direct-sequence-spread-spectrum. The performance of the proposed SDAM has been evaluated in both indoor (water tank) and outdoor (lake) environments. We demonstrated that the SDAM achieves 104 kbit/s with bit-error-rate (BER) of $2 \times 10^{-5}$ , 208 kbit/s with BER of 10−3, and 260 kbit/s with BER of 10−2 in real time over a 200 m horizontal link at a very-shallow lake environment. <s> BIB002 </s> An Overview of Next-Generation Underwater Target Detection and Tracking: An Integrated Underwater Architecture <s> B. SOFTWARE-DEFINED UNDERWATER NETWORK (SDUN) <s> Underwater acoustic sensor networks (UASNs) provide new opportunities for exploring oceans and consequently improving our understanding of the underwater world. UASNs usually rely on hardware infrastructure with poor flexibility and versatility. Compared with wireless sensor networks, UASNs are quite expensive to manufacture and deploy. Due to the unique data format, protocols, and service constraints of various applications, UASNs are typically deployed in a redundant manner, which not only leads to waste but also causes serious interference due to the presence of multiple signals in the same underwater region. Software-defined networking (SDN) provides an innovative means of improving the flexibility of underwater systems. In this paper, we present an SDN-based UASN framework, followed by the design of a clustering method in which learning automata and degree-constrained connected dominating sets are employed. We then propose a load balancing mechanism involving multiple controllers, based on the consistent hashing algorithm. Finally, we describe a simulation program (called UASNs hypervisor) that we developed and implemented to assess the network survival time, bit-error rate, and computational complexity. The experimental results show that the UASN was improved significantly. This work provides important theoretical and technical support for the implementation of SDN-based UASNs. <s> BIB003
Software-defined networking (SDN) has been announced as a flexible, efficient, and vendor independent technology. To engulf the constrained nature of underwater networks, the decoupling of control plane from the data plane enhances network compatibility with efficient utilization of resources and proper time management. SDN overcomes the hindrances of integration of various underwater devices to make safe and stable networking. SoftWater BIB001 is the first next-generation underwater communication system that integrates network function virtualization (NFV) to incorporate new underwater communication solutions. Due to this architecture, several underwater applications that operate on different communication technologies (acoustic, optical or radio waves) can be supported simultaneously. The physical-layer adaptation mechanisms are proposed in BIB002 to allow either seamless switching between different underwater technologies (such as orthogonal-frequency-divisionmultiplexing (OFDM) and direct-sequence-spread-spectrum (DSSS)) or joint adaptation of communication parameters (such as modulation constellation and channel coding rate). They present a new high-rate software-defined acoustic modem (SDAM) with real time adaptation capabilities and evaluate it in both indoor and outdoor environments. A multicontroller SDN-based UASN framework BIB003 is designed to present a load balancing mechanism with UASNs hypervisor. UASNs hypervisor is a simulation program that is developed and implemented to improve UASN performance.