Methods and devices for cell discovery
This disclosure sets forth methods and devices for communication between mobile devices and base stations with active and dormant states. In an embodiment, a base station transmits system information during an active state of the base station with at least one system-information message. The at least one system-information message includes a SystemInformationBlockType1 (“SIB1”) message with a first update-indicator field. The base station selects an update value that indicates whether the system information has changed since a previous transmission of a previous SIB1 message. The base station transmits at least one dormant-state message during a dormant state of the base station with the selected update value in a second update-indicator field of the at least one dormant-state message.
1. A method in a base station for a long term evolution network, the method comprising:
transmitting, during an active state of the base station, system information with at least one system-information message, wherein the at least one system-information message comprises a SystemInformationBlockType1 (“SIB1”) message with a first update-indicator field;
selecting an update value that indicates whether the system information has changed since a previous transmission of a previous SIB1 message; and
transmitting, during a dormant state of the base station, at least one dormant-state message with the selected update value in a second update-indicator field of the at least one dormant-state message.
2. The method of claim 1 wherein selecting the update value comprises:
selecting a previous value of the first update-indicator field of the previous SIB1 message if the system information has not changed since the previous transmission; and
selecting a value different from the previous value if the system information has changed since the previous transmission.
3. The method of claim 2 further comprising returning to the active state of the base station to transmit updated system information if the system information has changed since the previous transmission.
4. The method of claim 1 :
wherein transmitting at least one system-information message comprises transmitting a plurality of system-information messages with a first periodicity; and
wherein transmitting at least one dormant-state message comprises transmitting a plurality of dormant-state messages with a second periodicity that is greater than the first periodicity.
5. The method of claim 1 wherein transmitting at least one dormant-state message comprises transmitting at least one dormant-state message in a dormant physical broadcast channel.
6. The method of claim 5 further comprising transmitting only the dormant physical broadcast channel and a cell-discovery signal associated with an identifier of the base station during the dormant state.
7. The method of claim 6 further comprising transmitting radio-resource information to be used for uplink communication with the base station during the dormant state that is distinct from radio-resource information to be used for uplink communication with the base station during the active state.
8. The method of claim 7 :
wherein the radio-resource information indicates radio resources to be used for a wake-up request for the base station;
the method further comprising scanning the indicated radio resources for the wake-up request.
9. The method of claim 8 :
wherein the radio-resource information indicates a wake-up preamble sequence to be used for the wake-up request; and
wherein scanning the indicated radio resources comprises scanning the indicated radio resources for the wake-up preamble sequence.
10. The method of claim 6 further comprising transmitting radio-resource information including dormant state paging occasions that are distinct from active state paging occasions.
11. The method of claim 10 further comprising paging a mobile device during the dormant state using the dormant state paging occasions.