Antenna adaptation to manage the active set to manipulate soft hand-off regions
View Patent ↗A method of managing the number of base station engaged in soft hand-off in a mobile communication system. The method involves manipulating a subscriber based directional antenna so as to control the number of base transceiver stations, pilot channels, beacon signals or other signals detected to be used in soft hand-off processing. The adaptive antennas are modified to manage the number of active set members, such as by manipulating direction, beamwidth, or other antenna parameters.
1. A method for managing an active set of radio channels used in soft hand-off processing, the method carried out in a remote unit having an adaptive antenna, the method comprising the steps of:
determining an initial list of members for the active set by detecting an existence of at least two pilot channel signals in a vicinity of the remote unit;
making a change in an operating state of the adaptive antenna; and
requalifying the active set with the changed adaptive antenna operating state.
2. A method as in claim 1 wherein the adaptive antenna is a directional antenna array.
3. A method as in claim 2 wherein the adaptive antenna is a phased array.
4. A method as in claim 3 wherein the adaptive antenna uses multiple receivers and signal combiners.
5. A method as in claim 1 additionally comprising the steps of:
determining a reliability parameter for selecting members of the active set;
designating a selected one of the reliability parameters as sufficient to maintain a reliable connection; and
upon determining that more than one active set member is a reliable connection, changing operational state of the adaptive antenna to reduce a number of radio channel signals received.
6. A method as in claim 5 wherein the measure of reliability is selected from a group consisting of received signal strength indication, correlated power, and measurements of signal to noise ratio.
7. A method as in claim 1 additionally comprising the step of, when a number of members of the active set is less than a desired number:
adjusting the antenna state to capture additional radio signals to be possible members of the active set; and
requalifying the active set members.
8. A method as in claim 1 additionally comprising the step of, if a member of the active set is not reliable:
selecting a new setting for the adaptive antenna; and
requalifying active set members.
9. A method as in claim 1 additionally comprising the step of, when members of the active set are deemed unreliable:
steering the antenna such that additional radio signals are detected.
10. A method as in claim 1 additionally comprising the step of:
if candidate pilot channel signals are determined unreliable but of sufficient quality, periodically selecting a new antenna operating state such that criteria for receiving at least one radio signal is not satisfied.