# Advances in Improving Energy Efficiency of Fiber-Wireless Access Networks: A Comprehensive Overview
## 3 Energy Efficiency Analyses of Radio-and-Fiber Networks
### Power-Saving Techniques in the Optical Domain of FiWi Networks
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Reference** & **PS Method** &
\begin{tabular}{c} **Summary of Contributions Related to the** \\ **Improvement of FiWi Network** \\ **Energy Efficiency** \\ \end{tabular} \\ \hline
[41] & \
\begin{tabular}{c} A ML method of identifying and \\ categorizing network traffic \\ \end{tabular} &
\begin{tabular}{c} A ML-based approach for optimizing power \\ saving in WLANs by classifying network \\ traffic based on contextual factors, and \\ adjusting the listen interval accordingly. \\ \end{tabular} \\ \hline
[42] & \begin{tabular}{c} Overview of PS methods \\ \end{tabular} & \begin{tabular}{c} Overview of the power supply system \\ parameters for powering the BS sites with \\ renewable energy sources. Approaches for \\ reducing telecom operator energy and CAPEX \\ based on different air-conditioning systems for \\ BS sites. \\ \end{tabular} \\ \hline Wireless power-saving techniques & [43] & \
\begin{tabular}{c} Overview of PS methods \\ \end{tabular} &
\begin{tabular}{c} Overview of the renewable energy sources for \\ powering base station sites. Comparison of the \\ EE among hybrid systems that use multiple \\ renewable energy sources and systems that \\ use a single renewable energy source. \\ \end{tabular} \\ \hline
[44] & \
\begin{tabular}{c} Save energy and maximize \\ connectivity (SEMC) algorithm \\ \end{tabular} &
\begin{tabular}{c} A generic algorithm for ad-hoc wireless \\ networks that conserves energy and maintains \\ good connectivity through adjusting \\ transmission range and choosing a \\ transmission time based on data rates, which \\ results in reduced transmission power and \\ energy savings. \\ \end{tabular} \\ \hline
[21] & \
\begin{tabular}{c} ONU sleep mode with PSM \\ \end{tabular} &
\begin{tabular}{c} A wireless-optical topology reconfiguration \\ scheme that enables integrated energy saving \\ through reconfiguration of the optical \\ topology using ONU sleep mode and the \\ wireless topology using radio \\ interface standby. \\ \end{tabular} \\ \hline
[46] & \
\begin{tabular}{c} ONU sleep mode with PSM and \\ adaptive PSM \\ \end{tabular} &
\begin{tabular}{c} A method for controlling the ONU sleep \\ period based on the energy control mechanism \\ of wireless stations. \\ \end{tabular} \\ \hline
[47] & \
\begin{tabular}{c} ONU sleep mode with \\ powering off radio interfaces \\ \end{tabular} &
\begin{tabular}{c} An ONU sleep algorithm for dynamic \\ scheduling of the power states of ONUs based \\ on their traffic profile radio loads. An \\ algorithm for dynamic radios running off in \\ order to reconfigure the wireless topology by \\ dynamically controlling the power states \\ of radios. \\ \end{tabular} \\ \hline
[6] & \
\begin{tabular}{c} ONU sleep mode with PSM \\ and DBA \\ \end{tabular} &
\begin{tabular}{c} Proposed adaptive frame aggregation \\ mechanism that optimizes energy \\ consumption by adjusting frame lengths based \\ on channel quality. Proposed the delay-aware \\ load transfer mechanism that maximizes ONU \\ sleep time and ensures reliable service \\ transmission by allocating traffic load based \\ on QoS requirements. \\ \end{tabular} \\ \hline
[48] & \
\begin{tabular}{c} ONU sleep mode with PSM \\ and DBA \\ \end{tabular} &
\begin{tabular}{c} A PS scheme that coordinates power-saving \\ modes for wireless stations, APs and ONUs, in \\ order to reduce energy consumption. \\ \end{tabular} \\ \hline
[20] & \
\begin{tabular}{c} TDMA mechanism \\ between ONU and wireless \\ station and between OLT and \\ ONU with DBA \\ \end{tabular} &
\begin{tabular}{c} A technique that aims to reduce delays and \\ improve EE by organizing the system into \\ clusters of ONUs and using an equal partition \\ approach. Using this approach the ONUs in \\ the back-end and the wireless stations in the \\ front-end are active only during certain \\ timeslots in the TDMA cycle. \\ \hline \hline \end{tabular}
\end{table}