A base station, comprising: a processor configured to: determine a length and schedule of a silent period for each channel of a plurality of aggregated channels based on system and device information, wherein a first silent period for a first channel of the plurality of aggregated channels is not scheduled to occur when a second silent period for a current primary channel of the plurality of aggregated channels is scheduled to occur, and select the first channel of the plurality of aggregated channels as a new primary channel of the plurality of aggregated channels during a time period that comprises the second silent period of the current primary channel, wherein each of the remaining channels of the plurality of aggregated channels performs its respective silent period during the time period; and a transmitter configured to: transmit the schedule of the silent period for each channel of the plurality of aggregated channels to at least one wireless transmit/receive unit WTRU, and characterised by being configured to send a primary channel switch indication indicating a primary channel switch based on the selecting. a processor configured to: determine a length and schedule of a silent period for each channel of a plurality of aggregated channels based on system and device information, wherein a first silent period for a first channel of the plurality of aggregated channels is not scheduled to occur when a second silent period for a current primary channel of the plurality of aggregated channels is scheduled to occur, and select the first channel of the plurality of aggregated channels as a new primary channel of the plurality of aggregated channels during a time period that comprises the second silent period of the current primary channel, wherein each of the remaining channels of the plurality of aggregated channels performs its respective silent period during the time period; and determine a length and schedule of a silent period for each channel of a plurality of aggregated channels based on system and device information, wherein a first silent period for a first channel of the plurality of aggregated channels is not scheduled to occur when a second silent period for a current primary channel of the plurality of aggregated channels is scheduled to occur, and select the first channel of the plurality of aggregated channels as a new primary channel of the plurality of aggregated channels during a time period that comprises the second silent period of the current primary channel, wherein each of the remaining channels of the plurality of aggregated channels performs its respective silent period during the time period; and a transmitter configured to: transmit the schedule of the silent period for each channel of the plurality of aggregated channels to at least one wireless transmit/receive unit WTRU, and characterised by being configured to send a primary channel switch indication indicating a primary channel switch based on the selecting. transmit the schedule of the silent period for each channel of the plurality of aggregated channels to at least one wireless transmit/receive unit WTRU, and characterised by being configured to send a primary channel switch indication indicating a primary channel switch based on the selecting.