## 2 Related Work  
Quite a few number of related works have been conducted with adaptive and fault tolerant routing algorithms for wireless sensor networks [12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 50, 51, 52, 53]. For instance, [PERSON] _et al._[40, 52] proposed a self-selective fault tolerant routing protocol for a wireless _ad hoc_ network. The protocol employs a combined radio broadcast and autonomous programming technique to implement routing with reduced overhead. The routing protocol routes the packets via a near optimal path between nodes at runtime. Simulation results showed high routing performance under heavy network traffic, as well as network node and link failures. The authors in [24, 53] presented a novel protocol for self-healing in sensor network routing. The approach employs broadcast transmission and prioritized slotted back-off delay for sensor nodes to use their hop distance from the destination in order to determine how to transmit packets. By doing so, this ensures a dynamic traversal of minimum routes without nodes that specifies those neighboring nodes that transmit network packets. However, when faulty routes are encountered, the scheme locally and dynamically re-routes packets in order to survive the shortest routes despite spontaneous network topology changes. Other approaches that avoid neighbor state maintenance and allow destination nodes to contend with transmitting network packets are given in [26, 27]. These two protocols are similar to SHR [24, 53] and SSR [51, 52], which use local information instead of global network state information. Unfortunately, none of the two proposed approaches provide route repair mechanisms. GRAB [26] employs a very complex fault tolerant mechanism by allowing the flow of redundant network packets to take multiple paths to destinations. [PERSON] _et al._[28] employed a location coordinate system to allow only destination nodes within a given region to communicate with each other. [PERSON] and [PERSON] [29] used a concept similar to [28], and incorporated a back-off delay mechanism. Such mechanism makes use of a dual-radio concept with a busy tone signaling to enforce the channel to be clear before transmitting data in order to minimize the probability of network packet collisions. Another approach is given by [PERSON] _et al._[30], who employed an eligibility region given as a 60% fan shape that extends from a source towards a destination. Upon this, if a source node does not \"hear\" a response from any of its neighbors, it moves the eligibility region and looks for other neighbors. All these approaches use packet forwarding techniques, _i.e._, back-off delay and RTC/CTS schemes that result in packets that forward overhead. Other methods for direct routing are given in DSR [54], AODV [55], and DSDV [31]. The work presented by [PERSON] and [PERSON] [55] is regarded as the most popular directed routing protocol. Such protocol uses the route request and a reply mechanism in order to set up network paths between sources and destinations. This process yields a routing table by each node that contains a path from the sources to destinations. [PERSON] _et al._[54] employ a technique where the source node should contain the complete route information in the packet header. This also means that multiple routes are stored at the source node in order to avoid node failure. The limitation of the DSR protocol is its increases in the amount of memory use of the source node because of intermediate node storage and routing overhead. AODV [55] employed the use of a hello message in order to detect and fix broken network links. This results in an increase in network latency, particularly when dynamically looking for new routes. [PERSON] and [PERSON] [51] presented a cognitive and quality of service approach to routing in wireless sensor networks. They used the concept of smart packets for network path discovery coupled with reinforcement learning and neural networks.