# A Secure Communication in IoT Enabled Underwater and Wireless Sensor Network for Smart Cities
###### Abstract
High bit error rates and momentary losses of connectivity (shadow zones) could occur and the power of the the battery suffers shortage, especially batteries cannot be recharged frequently [9; 10; 11]. Different I-UWSN routing protocols are introduced to overcome these challenges by taking the advantages of underwater characteristics. Each schema has both achievements and deficiencies. Therefore, the design and implementation of routing protocol is an active research area of I-UWSN to favor the smart city idea. Thirdly, the routing protocol must ensure the reliability and effectiveness of data transmission from the source to the destination node. On behalf of reliability, the application goals can be reached or lead to the right directions or decisions. Therefore, reliable communication that is required for every application either exists in WSN or I-UWSN [12]. In both of the networks, it is a challenging task to make an application reliable. In I-UWSN, sensor nodes move from one to four meters per second because of water currents, i.e., water pressure, temperature, salinity, and water bodies movement. Because of these movements, the dynamic topology needs to overcome the causes that decrease the reliability of routing [6; 13]. In [14], two approaches are introduced that enhance the reliability of data Forward Error Correction (FEC) and re-transmission-based schema. In FEC, redundancy is added for transmission of data packets; whereas, for the re-transmission of data, sender request is served by Automatic Repeat Request (ARQ) and retransmitted the failed packet. Reliable link obtains network topology, which, in turn, determines the energy consumption, throughput and transmission delay of the network [15]. The stable connection consist of packet based (all generated packets are reliable), the second is event based (all created events for routing process is reliable), and the third is the summation of packet+ event (packets generated from a source node by maintaining a reliable link towards destination node) [14]. A reliable link must be considered as the selection of the path that has a higher probability of success ratio [16; 17]. As environmental monitoring systems and applications are becoming popular with time and are now in high demand for smart cities. In this paper, we have proposed state of the art protocol Time Based Reliable Link (TBRL), in which the distance-based reliability mechanism is used to reduce the effect of dynamic topology. The TBRL measures link quality for all existing routing paths from source to destination and selects one of the best paths for data transmission. By taking the benefits of limited resources, a flexible and robust mechanism for searching a path that is more reliable in terms of data, energy, delay, and throughput is considered in TBRL. The following are expected outcomes of the proposed TBRL:  
* Positioned aware routing without using Global Positioning System (GPS). * Node to node reliability assurance. * All possible paths are extracted from offshore to sink and less. effected path is taken for sending the data. * Expected delay and energy consumption of network are well known before the simulation s are conducted. * No complex routing table is maintained and no additional hardware resources are utilized for TBRL. * TBRL is applicable for smart environment like smart cities to provide a reliable path for communication between sensors and smart devices. * TBRL provides help to the machine learning approach for underwater object identification and classification. We have organized this paper, as follows: in the Section 2, related work is given; system model is presented in the Sections 3 and 4 explains the mathematical model; in the Section 5, simulation results are described. Finally, we concluded the paper in Section 6.