Survey on Routing Protocols for Under Water Sensor Networks
---
paper_title: Silent Positioning in Underwater Acoustic Sensor Networks

paper_content:

In this paper, we present a silent positioning scheme termed UPS for underwater acoustic sensor networks. UPS relies on the time difference of arrivals locally measured at a sensor to detect range differences from the sensor to four anchor nodes. These range differences are averaged over multiple beacon intervals before they are combined to estimate the 3-D sensor location through trilateration. UPS requires no time synchronization and provides location privacy at underwater vehicles/sensors whose locations need to be determined. To study the performance of UPS, we model the underwater acoustic channel as a modified ultrawideband Saleh-Valenzuela model: The arrival of each path cluster and the paths within each cluster follow double Poisson distributions, and the multipath channel gain follows a Rician distribution. Based on this channel model, we perform both theoretical analysis and simulation study on the position error of UPS under acoustic fading channels. The obtained results indicate that UPS is an effective scheme for underwater vehicle/sensor self-positioning.
---
paper_title: DFR: Directional flooding-based routing protocol for underwater sensor networks

paper_content:

Unlike terrestrial sensor networks, underwater sensor networks (UWSNs) have different characteristics such as a long propagation delay, a narrow bandwidth and high packet loss. Hence, existing path setup-based routing protocols proposed for terrestrial sensor networks are not applicable in the underwater environment. For example, they take much time when establishing a path between source and destination nodes due to the long propagation delay. In addition, the path establishment requires much overhead of control messages. Moreover, the dynamic and high packet loss degrades reliability, which invokes more retransmissions. Even though exiting routing protocols such as VBF were proposed to improve the reliability, they did not take into account the link quality. That is, there is no guarantee that packets reach the sink safely especially when a link is error-prone. In this paper, we therefore propose a directional flooding-based routing protocol, called DFR. Basically, DFR relies on a packet flooding technique to increase the reliability. However, the number of nodes which flood a packet is controlled in order to prevent a packet from flooding over the whole network and the nodes to forward the packet are decided according to the link quality. In addition, DFR also addresses a well-known void problem by allowing at least one node to participate in forwarding a packet. Our simulation study using ns-2 proves that DFR is more suitable for UWSNs especially when links are prone to packet loss.
---
paper_title: Improving the Robustness of Location-Based Routing for Underwater Sensor Networks

paper_content:

This paper investigates a fundamental networking problem in underwater sensor networks: robust and energy-efficient routing. We present an adaptive location-based routing protocol, called hop-by-hop vector-based forwarding (HH-VBF). It uses the notion of a "routing vector" (a vector from the source to the sink) acting as the axis of the "routing pipe", similar to the vector based forward (VBF) routing in the work of P. Xie, J.-H. Cui and L. Lao (VBF: Vector-Based Forwarding Protocol for Underwater Sensor Networks. Technical report, UCONN CSE Technical Report: UbiNet-TR05-03 (BECAT/CSE-TR-05-6), Feb. 2005). Unlike the original VBF approach, however, HH-VBF suggests the use of a routing vector for each individual forwarder in the network, instead of a single network-wide source-to-sink routing vector. By the creation of the hop-by-hop vectors, HH-VBF can overcome two major problems in VBF: (1) too small data delivery ratio for sparse networks; (2) too sensitive to "routing pipe" radius threshold. We conduct simulations to evaluate HH-VBF, and the results show that HH-VBF yields much better performance than VBF in sparse networks. In addition, HH-VBF is less sensitive to the routing pipe radius threshold. Furthermore, we also analyze the behavior of HH-VBF and show that assuming proper redundancy and feedback techniques, HH-VBF can facilitate the avoidance of any "void" areas in the network.
---
paper_title: REBAR: A Reliable and Energy Balanced Routing Algorithm for UWSNs

paper_content:

In this paper, we propose a reliable and energy-efficient routing algorithm for underwater wireless sensor networks (UWSNs). We first use a sphere energy depletion model to analyze the energy consumption of nodes in UWSNs. We then extend the model by considering the node mobility in UWSNs. Our analysis is in accordance with the common view that although water flows might cause the underwater environment more dynamic, this instability can actually improve energy-efficiency. However, the nodes closer to the sink still tend to die early, causing network partition around the sink. Accordingly, we propose a Reliable and Energy BAlanced Routing algorithm (REBAR). We explore the tradeoff between packet delivery ratio and energy efficiency. We design an adaptive scheme for setting data propagation range in order to balance the energy consumption throughout the network. Multi-path routing is used to provide redundancy. We further extend REBAR to deal with possible routing voids in the network which could be common in UWSNs. Simulation results show that our protocol outperforms existing VBF-based approaches in terms of reliability and network lifetime.
---
paper_title: Sector-Based Routing with Destination Location Prediction for Underwater Mobile Networks

paper_content:

Unlike in terrestrial sensor networks where the locations of destination nodes are often assumed to be fixed and accurately known, such assumptions are usually not valid in underwater sensor networks where the destination nodes tend to be mobile inherently, either due to their self-propelling capability, or due to random motion caused by ocean currents. As a result, many existing location-based routing protocols do not work well in underwater environments. We propose a location-based routing protocol that is designed for mobile underwater acoustic sensor networks, called "Sector-based Routing with Destination Location Prediction (SBR-DLP)". While the SBR-DLP also assumes that a node knows its own location like many other location-based routing protocols, it predicts the location of the destination node, and therefore, relaxes the need for precise knowledge of the destination's location. Through simulations, the SBR-DLP is shown to enhance the packet delivery ratio significantly when all nodes are mobile.
---

Title: Survey on Routing Protocols for Under Water Sensor Networks

Section 1: Introduction
Description 1: Introduce underwater sensor networks (UWSNs), mention differences compared to terrestrial sensor networks, including energy consumption, node cost, deployment, power requirements, and mediums of communication. Discuss the challenges of routing in UWSNs and why specialized protocols are needed.

Section 2: Vector Based Forwarding (VBF)
Description 2: Describe the VBF protocol, which handles packet losses and node failures through redundant and interleaved paths, and emphasize its scalability and energy-saving characteristics.

Section 3: Hop by Hop Vector Based Forwarding (HH-VBF)
Description 3: Explain the HH-VBF protocol, focusing on its use of virtual pipes for per-hop forwarding, and the computations made by nodes to forward packets based on their location.

Section 4: Focused Beam Routing (FBR)
Description 4: Detail the FBR protocol, highlighting its prevention of unnecessary broadcast flooding, suitability for both static and mobile nodes, and location-awareness requirements for source and destination nodes.

Section 5: Reliable and Energy Balanced Routing Algorithm (REBAR)
Description 5: Cover the REBAR protocol, a location-based method that uses geographic information for data transfer, defines nodes by unique IDs, and utilizes specific assumptions about node locations and data transfer rates.

Section 6: Sector-based Routing with Destination Location Prediction (SBR-DLP)
Description 6: Describe the SBR-DLP protocol, which avoids data packet flooding by predicting and utilizing destination mobility information, and selecting the next hop using candidate nodes within a communication circle.

Section 7: Direction Flooding Based Routing (DFR)
Description 7: Discuss the DFR protocol, which enhances reliability through packet flooding, and requires nodes to know their location, one-hop neighbor locations, and the final destination.

Section 8: Location Aware Source Routing (LASR)
Description 8: Explain the LASR protocol, which uses link quality metrics and location awareness to handle high latency of acoustic channels, and includes all relevant network information in the protocol header.

Section 9: Conclusion
Description 9: Summarize the surveyed UWSN routing protocols and their comparative aspects, emphasizing energy efficiency and dynamic network handling abilities. Point out which protocols are best suited for specific applications based on the comparisons.