An optical line terminal, OLT, wherein the OLT is configured to communicate with a plurality of optical network units, ONU, the OLT comprising: a processor configured to perform the step of: determining a downstream bandwidth map transmission frequency, wherein the downstream bandwidth map transmission frequency is determined such that the downstream bandwidth map (700, 800) is transmitted once per a group of downstream frames; and iteratively perform the steps of: calculating a downstream bandwidth map (700, 800), wherein the downstream bandwidth map (700, 800) indicates scheduling of the OLT downstream transmission to at least one ONU in the plurality of ONUs, wherein the scheduling indicates an active period of time when the OLT is scheduled to transmit a data frame to the ONU; and generating a message comprising the downstream bandwidth map (700, 800); and a transmitter coupled to the processor and configured for sending the message to the ONU via a passive optical network, PON, wherein the message instructs the ONU to power off an ONU receive data processing unit outside the active period, wherein the message is transmitted according to the downstream bandwidth map transmission frequency; wherein, the processor is configured to repeat the step of determining a downstream bandwidth map transmission frequency to adapt to one or more changes in the passive optical network. a processor configured to perform the step of: determining a downstream bandwidth map transmission frequency, wherein the downstream bandwidth map transmission frequency is determined such that the downstream bandwidth map (700, 800) is transmitted once per a group of downstream frames; and iteratively perform the steps of: calculating a downstream bandwidth map (700, 800), wherein the downstream bandwidth map (700, 800) indicates scheduling of the OLT downstream transmission to at least one ONU in the plurality of ONUs, wherein the scheduling indicates an active period of time when the OLT is scheduled to transmit a data frame to the ONU; and generating a message comprising the downstream bandwidth map (700, 800); and determining a downstream bandwidth map transmission frequency, wherein the downstream bandwidth map transmission frequency is determined such that the downstream bandwidth map (700, 800) is transmitted once per a group of downstream frames; and iteratively perform the steps of: calculating a downstream bandwidth map (700, 800), wherein the downstream bandwidth map (700, 800) indicates scheduling of the OLT downstream transmission to at least one ONU in the plurality of ONUs, wherein the scheduling indicates an active period of time when the OLT is scheduled to transmit a data frame to the ONU; and generating a message comprising the downstream bandwidth map (700, 800); and calculating a downstream bandwidth map (700, 800), wherein the downstream bandwidth map (700, 800) indicates scheduling of the OLT downstream transmission to at least one ONU in the plurality of ONUs, wherein the scheduling indicates an active period of time when the OLT is scheduled to transmit a data frame to the ONU; and generating a message comprising the downstream bandwidth map (700, 800); and a transmitter coupled to the processor and configured for sending the message to the ONU via a passive optical network, PON, wherein the message instructs the ONU to power off an ONU receive data processing unit outside the active period, wherein the message is transmitted according to the downstream bandwidth map transmission frequency; wherein, the processor is configured to repeat the step of determining a downstream bandwidth map transmission frequency to adapt to one or more changes in the passive optical network.