# Energy Efficient Routing in Wireless Sensor Networks: A Comprehensive Survey
## 3 Network Structure
### Hierarchical
#### 3.2.1 Hierarchy Based
& \\  & It offers increased & & & & & The route with & \\ I-LEACH & network stability and & & & & aggregation & & minimum & \\
[53] & reduced energy & & & & & energy cost is & \\  & consumption. & & & & & used. & \\  & & & & & & & \\  & & & & & & & \\  & & & & & & & \\  & & & & & & & \\  & & & & & & & \\ TLHCLP & It prolongs network & & & & & & forward them to \\
[55] & lifetime. & & & the BS. & & & cluster heads & \\  & & & & & & until the BS is & \\  & & & & & & reached. & \\ LEACH-DS-ACOR & provides improved & & It does not support & & & & route using \\
[56] & network lifetime. & & & mobility. & & & ACO. & \\  & & & & & & & \\  & & & & & & & \\ PEGASIS & It performs less & & & & & & \\  & broadcasts using data & & & single leader & & & \\  & aggregation. & & & mechanism can cause & & & route selection & \\  & & & & congestion. & & & \\ Hierarchical & Delays, collisions, and & & & & & & \\ PEGASIS & signal interference are & & & & & & \\  & [58] & reduced. & & & & & \\  & & & & & & & \\ MH-PEGASIS & consumption of & & & & & & \\  & distant cluster heads & & & & & \\  & is reduced. & & & & & \\  & & & & & & & \\ Enhanced & & & & & & heads route data & \\ PEGASIS & Redundant data are & & It faces delay from & & & to the lower & \\
[60] & decreased. & & distant nodes. & & & level until the BS & \\  & & & & Cluster formation & & & \\  & It has better & & causes overhead. & & & \\ TEEN [61] & performance and less & & Only reactive & & & & \\  & broadcasts. & & communication is & & & \\  & & & & & & \\  & & & & & & \\ APTEEN & It saves more energy & & & It has more & & \\
[62] & than TEEN. & & complexity and delay & & Low & Static BS & \\  & & & & than TEEN. & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\ VGA [63] & It provides energy & & & & & & \\ efficiency and & & & problem of optimal & & & \\  & & & & & & \\  & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Protocol** & **Advantages** & **Disadvantages** & **Scalability** & **Mobility** & **Routing** & **Robustness** \\ \hline \multirow{4}{*}{TTDD [64]} & It can be used for multiple mobile sinks in an area with static node. & A virtual grid structure is built by each source node. & Low & None & It uses greedy route selection. & Good \\  & It avoids cluster head overload and has uniform cluster head placement. & It faces decreased performance gain for small field area. & Limited & None & The best route is selected. & Limited \\ \multirow{4}{*}{ECHERP [66]} & It has high energy efficiency and very good scalability. & The metrics related to QoS and time constraints are not considered. & Good & \multirow{4}{*}{Supported} & Cluster heads route data to the BS either directly or via higher level & & & \\  & It analyzes energy & It may perform below optimal performance. & Good & None & The data from multiple sources are sent to the BS via multi-hop routing. & Limited \\ \multirow{4}{*}{HPAR [68]} & It supports scalability and considers both transmission power and minimum battery power. & It causes increased overhead. & Low & None & \multirow{4}{*}{None} & \multirow{4}{*}{Good} \\  & It analyzes energy and minimum battery power. & It analyzes energy and optimizes both outcomes. & Good & None & The best route is selected. & Limited \\ \multirow{4}{*}{Sleep/Wake Scheduling Protocol [69]} & It is saving energy scheduling with sleep mode and has congestion awareness. & Overhead is caused. & Good & \multirow{4}{*}{None} & The BS chooses & & \\  & Only the BS constructs the grid. & At high speeds, more energy is consumed. & Good & Limited & & & \\ \multirow{4}{*}{GBDD [70]} & Continuous data delivery from source to the BS is attained. & In case the number of cluster nodes exceeds a specific amount, network lifetime. & Limited & Static BS & \multirow{4}{*}{Good} \\  & It attains security and & It faces packet latency. & Good & Static BS & The best route is selected. & Good \\ \multirow{4}{*}{NHRPA [72]} & It analyzes energy consumption.