# Cross-Layer Energy Optimization for IoT Environments: Technical Advances and Opportunities
## 4 Energy Efficient Techniques in the IoT
### Energy Efficient Techniques at Network/Communication Layer
#### 4.3.2 Energy Efficient Routing Techniques
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c} \hline \hline
**Protocols** & **Characteristics** & **Issues** & **Contributions** & **Techniques** & **Simulators** & **Metrics** & **Limitations** & **Classifications** & **Classifications** \\ \hline \multirow{3}{*}{EEPR} & Network partitioning and & Evenly consumption of & Energy consumption in & Energy consumption of & Energy efficient & NS-2 on Linux & -EK & Delay is not considered. \\  & Efforts consumption in & distributed network & enhanced network lifetime & probabilistic routing & & fodora 13 & -4Q & -Roting success \\  & & & & & & & -NL & route setup delay is high \\ \hline \multirow{3}{*}{REL} & Restriction of sensor & Every distribution of & & & & & & & -EE & & \\  & nodes in terms of energy, & network resources, & & & & & & & & -4Q & Not managed \\  & processing and memory. & & & & & & & & & -NL & radio/transmissions to \\  & & & & & & & & & -PDR & improve energy saving \\ \hline \multirow{3}{*}{EECR} & Energy consumption & Enhanced lifetime and less & & & & & & & & & & & & \\  & challenge in asynchronous & & energy consumption & & & & & & & & & & & \\  & communication & & & & & & & & & & & & \\ \cline{1-1}  & & & & & & & & & & & & & & \\ \hline \multirow{3}{*}{ER-RPL} & Energy efficiency, & Energy efficient, reliable & & & & & & & & & & & & \\  & zeone problem & & & & & & & & & & & & & \\ \cline{1-1}  & & & & & & & & & & & & & & \\ \cline{1-1}  & & & & & & & & & & & & & & \\ \hline \multirow{3}{*}{ERGID} & Assurance of real & & Reliable data transmission & & & & & & & & & & & \\  & time emergency & & and energy efficient & & & & & & & & & & & \\ \cline{1-1}  & response ability & & & & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Summary of energy efficient routing techniques. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline
**Protocols** & **Characteristics** & **Issues** & **Contributions** & **Techniques** & **Simulators** & **Metrics** & **Limitations** & **Classifications** & **Classifications** \\ \hline \multirow{3}{*}{EEPR} & Network partitioning and & Evenly consumption of & Energy efficient & NS-2 on Linux & -EK & Delay is not considered. \\  & Energy consumption in & energy consumption in & enhanced network lifetime & probabilistic routing & & & & & & & & \\  & & & & & & & & & & & & \\  & & & & & & & & & & & & \\ \hline \multirow{3}{*}{REL} & Restriction of sensor & Every distribution of & & & & & & & & & & & \\  & nodes in terms of energy, & network resources, & & & & & & & & & & \\  & processing and memory. & enhanced lifetime and QoS & & Routing protocol & & & & & & & & \\  & & & & based on energy and & & & & & & & & \\  & processing and memory. & enhanced lifetime and QoS & & & & & & & & & \\  & & & & & & & & & & & \\  & & & & & & & & & & & \\ \hline \multirow{3}{*}{EECR} & Energy consumption & Enhanced lifetime and less & & & & & & & & & & & & \\  & challenge in asynchronous & & energy consumption & & & & & & & & & & \\  & communication & & & & & & & & & & & \\ \hline \multirow{3}{*}{ER-RPL} & Energy efficiency, & Energy efficient, reliable & & & & & & & & & & & & \\  & zeone problem & & & and robust solution. & & & & & & & & & \\ \cline{1-1}  & & & & & & & & & & & & & \\ \cline{1-1}  & & & & & & & & & & & & & \\ \hline \multirow{3}{*}{ERGID} & Assurance of real & & Reliable data transmission & & & & & & & & & & & \\  & time emergency & & and energy efficient & & & & & & & & & & & \\ \cline{1-1}  & response ability & & & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Comparative assessment of energy efficient routing techniques.