determine an indication of an occupancy level for the second time period and for the shared channel wherein the indication of an occupancy level is determined based on the occupancy states for the shared channel for each of the first time periods.
19. A mobile communications system according to.claim 18, wherein the first mobile communications device is configured to generate a measurement report based on the indication of an occupancy level for the shared channel and to transmit the measurement report to the base station.
20. A mobile communications system according to claim 19, wherein the first mobile communications device is configured to
detect that the shared channel is congested when an occupancy level for the shared channel is estimated to be above a congestion threshold; and
to, upon detecting that the shared channel is congested, generate and transmit the measurement report.
21. A mobile communications system according to claim 19, wherein the mobile communications
system is configured to
upon receipt of the measurement report, determine for at least one of the base station whether to
activate or deactivate the shared channel for communicating with mobile communications devices based
on the indication of an occupancy level for the shared channel. [
22. A mobile communications system according to claim 19, wherein the first mobile communications device is configured to transmit the measurement report at one or more of the following times: periodically, upon receipt of a measurement request, at a randomly selected time, or when one or more predetermined events occur.
23. A mobile communications system according to claim 18, wherein the first mobile communications device is configured to determine the indication of an occupancy level at one or more of the following times: periodically, upon receipt of a measurement request, at a randomly selected time, or when one or more predetermined events occur.
24. A mobile communications system according to claim 22, wherein a predetermined event comprises one of: a mobile communications device being powered up, a mobile communication device experiencing congestion on a frequency channel, a user request, a mobile communications network request, the expiry of a timer and a mobile communication device having a low utilisation level.
25. A mobile communications system according to claim 18, wherein the first mobile communications device being configured to measure a channel utilisation comprises the first mobile communications device being configured to
determine whether the base station is transmitting signals on the shared channel,
when it is determined that the base station is transmitting signals on the shared channel,
measure the channel utilisation based on an interference measurement indicating an interference level
identified for the signals transmitted on the shared channel by the mobile communications system; and
when it is determined that the base station is not transmitting signals on the shared channel,
measure the channel utilisation based on a measurement indicating a power received via the shared
channel.

26. A mobile communications system according to claim 18, wherein the first mobile communications
device comprises a first transceiver operable to receive signals on the shared channel from the base
station using a first technology and a second transceiver operable to receive signals on the shared
channel using a second technology, the second technology being different from the first technology,
wherein the first mobile communications device is configured to measure the channel utilisation based on a first channel utilisation derived from signals received by the first transceiver and on a second channel utilisation derived from signais received by the second transceiver.
27. Circuitry for a mobile communications device for use in a mobile communications system, the !
system comprising a base station arranged to communicate with mobile communications devices via a
wireless interface provided by a first frequency channel allocated to mobile networks communications for
the mobile communications system and by a shared frequency channel which can be shared by the mobile communications system and by other wireless communications systems, wherein the circuitry comprises a controller element and a transceiver element configured to operate together to:
measure, for each of a plurality of first time periods within a second time period, a channel utilisation on the shared channel based on signals received by the transceiver unit;
determine channel occupancy states for the shared channel for each of the first time periods [
based on the measured channel utilisation; and
determine an indication of an occupancy level for the shared channel for the second time period, j;
wherein the indication of an occupancy level is determined based on the occupancy states for the shared channel for each of the first time periods.