# A Review of Machine Learning-Based Routing Protocols for Wireless Sensor Network Lifetime +
## 2 The Characteristics of WSNs  
_Computing abilities_: Due to its small size, high price, and high battery consumption, the sensor has very limited computational capabilities. In terms of battery energy, sensor nodes frequently become invalid and out of control due to battery fatigue. So, the conservation protocols and algorithms need to be thought about ahead of time.  
_Communication capabilities_: Due of their restricted communication capabilities and range, WSN communication devices have limited utility. The typical communication range is less than a meter, and environmental factors can have an impact on the sensor.  
_Dynamic Power Management (DPM)_: Energy consumption at the sensor node can be managed and preserved with DPM. Batteries power the sensor nodes, and how much juice they need varies with the task at hand (data collection, processing, or transmission). Because it is difficult to charge or replace the batteries, the sensor network cannot be used for a longer period of time.  
_Multi-hop communications_: transmissions in a WSN occur over multiple hops in a radio frequency chain, allowing for intercommunication between nodes.  
_Application relevance_: Data aggregation from WSNs is used to analyze traffic patterns and other factors. The sensor network deviates from the standard network in that it does not rely on a central server to collect data but rather on the apps running on it and the final working environment. The physical signals and routing protocols used by the various sensor network applications are not shared.  
_Reliability_: the packet dimension, node frequency, protocol architecture, hop-by-hop connectivity, endways communication, buffer size, packet loss ratio, packet distribution proportion, bandwidth, and loss retrieval are just some of the aspects that affect WSN consistency [2].  
_Reliability semantics_: Complete packet delivery is what packet reliability ensures. To fully define the reliability semantics, it is necessary to consider not only event reliability but also end-to-end consistency, upstream consistency, and downstream reliability.  
_General problems in WSNs_: In terms of node placement, initial and foremost is the difficulty of getting the nodes set up, which is complicated by factors like cost and locational restrictions [3].  
_Energy consumption without accuracy_: establishing a connection between nodes and base stations (BSs) requires a certain number of nodes, the consumption of which might influence the network's lifespan.  
_Coverage_: the sensor's narrow field of view means it can only monitor a subset of the network's physical space.  
_Node dynamics_: Nodes in networks are presumed stable. In other circumstances, however, it becomes critical to fortify the adaptability of base stations or CHSs. Since node membership tends to be fluid and the cluster is subject to change over time, studying node dynamics presents a formidable challenge.  
Overlay clusterAs was previously noted, the network administrator or the sensors themselves can decide on the CH. A person who is currently part of one cluster is likely to switch over to another CH if they make their decision at a later date. To address design concerns, it cuts across functional silos. In order to avoid inequity, starvation, or stagnation because of resource rivalry, it is crucial to put in place the mechanisms that will allow for the detection of overlapping groups and the coordination between them.  
Load balancingIn sensor networks, this is a serious issue because CHs are typically created after the initial deployment of sensors. The head will overload the specific CH responsible for failure if the delivery of member sensor nodes is not balanced over all available CHs. So, it is important to form groups of similar size in such circumstances to ensure a level playing field.