# Comparative Study of Energy Efficient Routing Techniques in Wireless Sensor Networks
## 3 The Proposed Taxonomy
### Network Topology (Structure)
#### 3.6.4 Mobility-Based Protocols  
After their deployment, sensor nodes are able to change their position in some cases due to the influences of several factors such as mobile platform, environmental conditions (wind, water... ), and physical security or by the personal intervention [81] in addition to the sinks that can be mobile for needs of coverage or connection. Hence, we can a mobile sensor nodes or mobile sinks. Mobility results in frequent changes in network structure, which in turn introduces several problems such as route changes, packet delivery delay, isolated areas, etc. The mobility-based protocols, either for mobile sensor nodes or mobile  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Protocol** & **Heterogeneity Level** & **Network Lifetime** \\ \hline
**DDEEC** & 2 & Medium \\ \hline
**TSEP** & 3 & Medium \\ \hline
**EDDEEC** & 3 & High \\ \hline
**BEENISH** & 4 & High \\ \hline \hline \end{tabular}
\end{table}
Table 6: Comparison of heterogeneity-based routing protocols for WSNs.  
sinks, are designed to adapt to this mobility, overcome these problems and enhance the network lifespan.  
Mobile Sinks-Based Routing Protocols  
Those routing protocols are used in some WSNs where sink nodes are mobile. Among these protocols, we find:  
* **Meeting Position Aware Routing (MPAR) protocol**  
MPAR is designed as a query-based routing protocol for WSNs using mobile sinks [82]. In fact, sinks send out a query message containing geographic information and some other parameters used by source nodes to calculate the estimate propagation time (EPT) used by the relay nodes to calculate the estimated meeting position (EMP) to predict the position of the mobile sink to send queried data to the predicted position. Simulations results show that MPAR is very effective in energy and delivery latency.  
Mobile Sensor Nodes-Based Routing Protocols  
This category of protocols is designed for WSNs in which sensor nodes support mobility. Among these protocols, we find:  
* **Mobility-based clustering protocol (MBC)**  
MBC is designed as a proactive hierarchical routing protocol supporting mobile sensor nodes in WSNs [83]. It is inspired by the LEACH-M protocol and cluster-based routing protocol (CBR) [84]. Indeed, it selects the CHs according to the mobility and the residual energy. This protocol ensures reliable paths to allow mobile nodes to join the appropriate CH without packet loss. In [85], the authors show that MBC increases PDR and reduces energy consumptions in WSNs.
* **Energy-Efficient and Fault-Tolerant Routing Protocol for Mobile Sensor Network (FTCP-MWSN)**  
FTCP-MWSN is designed as hierarchical routing protocols for mobile nodes in WSNs [86]. To conserve energy, sensors send small-sized packets to the CH, which sends the ID of nodes to the BS in order to achieve reliability and provide fault tolerance. Simulations have proven the energy efficiency of FTCP-MWSN that can detect the failure of sensor nodes, but it presents some end-to-end delay.  
Table 7 establishes a comparison between mobile-sensor-node-based routing protocols [87].