# An Efficient Void Aware Framework for Enabling Internet of Underwater Things
## 1 Introduction  
Due to numerous implications in domains such as ecological, academic, industrial, and economic, the Internet of Underwater Things (IoUTs) has recently attracted the interest of many research and development activities in maritime industries [1, 2, 3, 4]. The performance of IoUTs is influenced by optical and signals, primarily radio signals, which involve huge antennas and a lot of transmission energy because they move at low frequencies and across long distances. Optical communications, on the other hand, require extreme precision in focusing small laser beams and are affected by scattering [5, 6, 7, 8]. Additionally, due to the obvious hard environment, sensors in the IoUTs have low energy and require frequentbattery replacement. As a result, the entire network lifetime must be increased. Consequently, acoustic signals can be employed as a communication channel with IoUTs because they can avoid these obstacles [9; 10]. However, because of the extreme characteristics of the underwater channel, the IoUTs face various obstacles when exploiting these acoustic signals, including a large propagation delay, high error rate, and limited bandwidth. [11; 12]. Additionally, due to the obvious hard environment, sensors in the IoUTs have low energy and require frequent battery replacement. As a result, the entire network lifetime must be increased [13; 14; 15]. One of the primary challenges in the IoUT environment that has a serious influence on packet delivery ratio and packet drop, especially in sparse networks, is communication void [1; 16; 17]. Communication void is defined as a problem that occurred if the data packet reaches some areas that did not have any available sensors to forward the data packet. These areas are composed of two types of areas: The void area is the area that did not have any sensors and the critical area is the area that contains the actual void node (i.e., the nodes that did not have any shallower neighbor), intuitive void node (i.e., the nodes that leads the data packet to reach actual void node), or both. Few protocols in UWSN, provide solutions on this topic [17; 18; 19; 20]. To cope with void sensors, current methods employ either geolocation data (location-based) or semi-location information (beacon-based) [13; 21]. However, using such methods increase the energy consumption which limits the applicability in the IoUT scenario. Therefore, the void detection technique must be designed to locate void sensors without the use of localization data and to prevent data packets from being sent to the void area during the data forwarding phase to maximize the packet delivery ratio including all network types, especially in wide networks. In related literature, SPRE-PBR [17] is one of our literature that proposed recently for green computing enabling energy-centric multi-layered concepts. It was recommended by authors to enhance SPRE-PBR to cope with communication void areas. On the other hand, vector-based void avoidance (VBVA) employs the 3D flooding method for identifying the void areas in the network [22]. Moreover, Void-Aware Pressure Routing (VAPR) [23] and the Inherently Void Avoidance Routing (IVAR) [24] uses semi-geo information provided by the sink to identify the void nodes and find the alternate route, which is not practically suitable in most underwater networking applications [7]. In this context, an efficient void aware (EVA) information dissemination routing framework is presented in this paper for enabling IoUT. The framework majorly focuses on identifying a void region in under information dissemination network scenario and subsequently intelligent data forwarding considering the layer-wise classification of the void network region. The major contributions of this paper can be summarized as follows:  
* Firstly, underwater network architecture is modeled considering potential void region identification in terms of actual void nodes, intuitive void nodes, and critical network area.