# PDTR: Probabilistic and Deterministic Tree-based Routing for Wireless Sensor Networks
## 2 Related Work  
Routing protocols for WSNs are divided into three main categories: network organization-based routing protocols, where the protocols are classified as flat-based routing, hierarchical-based routing, and location-based routing (geo-centric); route discovery-based routing protocols, where the protocols are classified as reactive protocols, proactive protocols, and hybrid protocols; and operation-based routing protocols, where the protocols are classified as multi-path routing protocols, query-based routing protocols, negotiation-based routing protocols, QoS-based routing protocols, and coherent data processing routing protocols [20]. Designing a successful protocol for WSNs must achieve both energy efficiency and balance. A wide range of researchers have focused on energy efficiency, but few of them have focused on energy balancing (network lifetime). The authors in [21] proposed the Enhanced tree routing protocol (ETR), which improves the traditional Tree Routing protocol (TR), by the fact that ETR paths are built according to the parent-child links, and other one-hop neighbors links, to reach shorter paths. ETR simulation showed more energy efficiency, comparatively, than TR simulation; this is explained by the fact of using the address structure to select ETR paths. The article [14] proposed Distance-based Energy-Aware Routing (DEAR). From the simulation results, it is shown that DEAR reduces and balances the energy consumption in comparison to the previously proposed protocols. The achieved results are explained by the fact that DEAR takes into consideration, first, the distance distribution, and second, the residual energy. One year later, a proposed Energy-Balanced Routing Protocol (EBRP) was proposed in [22]. EBRP simulation results show better performance in term of energy balancing. This is explained by the fact that this proposed protocol takes into consideration the depth, the energy density, and the residual energy. Later, the authors in [23] introduced a probabilistic tree-based routing protocol (TBRR), that processes in two stages. The packets in TBRR protocol are rooted toward the sink under a highly reliable manner based on the node degree and link loss. From the simulation, the TBRR protocol improved the calculation of forwarding probability. Two years later, in [24], a designed Self-Organized Tree-Based Energy-Balance routing protocol (GSTEB) was presented. In the GSTEB protocol, the base station selects the root for nodes, and each node is aware of itself and its neighbors' information. The simulation results demonstrate a better performance in term of energy balancing. This can be explained by the fact that GSTEB is a dynamic protocol. In [25], the authors presented a quadrant-based routing protocol that divides the network area into four quadrants. The selection of the parent node is based on the distance, and residual energy simulation results prove better performance in terms of energy efficiency, with respect to load balancing. Recently, the authors in [26] developed an Energy Efficient Balanced Tree-Based Routing Protocol for Wireless Sensor Network (EEBTR) that structures a balanced-tree scheme by proceeding in two phases--the Up-Down Balancing phase (UDB) and Down-Up Balancing phase (DUB)--to balance between number of hops and energy loading in the network. The EEBTR results show better performance in terms of energy balancing and network lifetime. Finally, Routing protocols in WSNs are classified into two main approaches: the deterministic protocol approach, and probabilistic protocol approach [27]. The protocols cited above are deterministic protocol approaches. In the deterministic approach, the forwarder node for each node is already fixed, and the routing paths are predefined. This may cause quick energy depletion, which can result in the loss of some nodes and a loss of part of the network. In [28], the authors proposed a probabilistic scheme based on the node degree and link loss to increase the reliability of selective forwarding.