## 2 Related Works  
### Redundancy-Based Techniques  
[PERSON] et al. [10] proposed a reliable information forwarding using multiple paths (ReInForM) protocol to deliver packets at a desired reliability at a proportionate communication cost. ReInForM provides the desired reliability in packet delivery in the presence of any channel errors by sending multiple copies of a single packet along multiple paths. Based on the local knowledge of some network conditions, the source decides to send multiple copies of packets through multiple paths. Each packet header contains information about network conditions from the previous step; this information is used in forwarding decisions. As a packet travels toward the sink, these fields are updated at each node to account for local deviations. ReInForm uses the dynamic packet state (DPS) approach [11] to carry state information in the packet header, enabling the network to serve the packet in a desired manner, even though the forwarding nodes do not maintain any packet state. The DPS mechanism is useful in sensor networks because it does not require any caching or state maintenance at intermediate nodes, which would be required in any acknowledgment based scheme. It adapts to any channel errors and topological deviations using only local knowledge, while maintaining the desired level of reliability at global scale. [PERSON] et al. [12] proposed a packet delivery mechanism called multi-path and multi-SPEED routing protocol (MMSPEED) for a probabilistic quality of service (QoS) guarantee in WSNs. The proposed routing protocol is designed with two important goals: (1) a localized packet routing decision without a global network state update or a priori path setup, and (2) providing differentiated QoS options in the domains of timeliness and reliability. Multiple QoS levels are provided in the timeliness domain by guaranteeing multiple packet delivery speed options. In the reliability domain, various reliability requirements are supported by probabilistic multipath forwarding. These mechanisms for QoS provisioning are realized in a localized way without global network information by employing localized geographic packet forwarding augmented with dynamic compensation, which compensates for local decision inaccuracies as a packet travels towards its destination. This way, MMSPEED can guarantee end-to-end requirements in a localized way, which is desirable for scalability and adaptability to large scale dynamic sensor networks. [PERSON] [13] proposed a fault-tolerant and energy efficient multipath routing (FEEM) scheme aided with channel coding and an interleaving scheme for WSNs. FEEM is a cross-layer approach for WSNs. The author also presented an energy and mobility-aware geographical multipath-routing scheme for multipath selection. The mobility, remaining energy, and distance to the target node of candidate sensor nodes in the local communication range were used for next hop relay node election, and a fuzzy logic approach was used for decision-making. Simulation results showed that the FEEM could tolerate some link failures, which makes WNSs survivable and resilient. [PERSON] et al. [14] presented a coverage-connectivity based fault tolerance procedure to ensure fault tolerance in WSNs while guaranteeing both coverage and connectivity in the networks and to reduce the packet loss rate in the network. In the first step of neighbor discovery, sensor nodes periodically send \"Hello\" messages. The next step is the verification of coverage and connectivity functions. In this step, before deciding to trigger or not to trigger the recovery procedure, the \"up to fail\" node will determine if its coverage and connectivity functions would be altered after its defection. After triggering the fault recovery procedure by the \"up to fail\" node, the step of the neighboring set and the redundant subset computation is performed to determine which nodes among the node's neighbors are eligible to replace it.