Secondary station and method of operating the station
View Patent ↗A secondary station has a receiver capable of resolving signals received ( 504,510 ) as a plurality of multipath signals from a plurality of base stations during a soft handover process. In order to decode and act upon the received signals in a very short period of time, an initial subset of received multipath signals is processed ( 506 ) to provide an estimate of the action needing to be taken by the station, which action is then implemented by the station ( 508 ). Later arriving signals are processed separately ( 512 ) and used to update the estimate, as a result of which the action already taken may be corrected ( 514 ). Such a secondary station is particularly suitable for decoding and acting upon power control commands included in received signals in a UMTS system, for which a very limited period of time is provided by the UMTS specification.
1. A secondary station for use in a radio communication system including at least two primary stations, the secondary station comprising:
means for engaging in a soft handover process, in which the secondary station communicates simultaneously with the at least two primary stations; and
receiver means for receiving transmitted signals from the at least two primary stations as a plurality of multipath signals, wherein means are provided for processing a first subset of the multipath signals based on a first predefined window of arrival times to provide an estimate of what action should be taken by the secondary station, and for processing a second subset of the multipath signals based on a second window of arrival times that is greater than the first predefined window of arrival times to update the estimate.
2. The secondary station as claimed in claim 1 , further comprising power control means for adjusting a power of uplink transmissions in response to power control commands received from the primary stations; the estimate including a next power change to be implemented by the secondary station.
3. The secondary station as claimed in claim 2 , wherein the receiver means includes signal resolution means for resolving the multipath signals, and further comprising means for determining whether each of the multipath signals is received before or after a predetermined time and for allocating to the signal resolution means a weaker signal arriving before the predetermined time in preference to a stronger signal arriving after the predetermined time.
4. A method of operating a secondary station, comprising:
engaging in a soft handover process, in which the secondary station communicates simultaneously with at least two primary stations;
receiving transmitted signals from the at least two primary stations as a plurality of multipath signals;
processing a first subset of the received multipath signals based on a first predefined window of arrival time to provide an initial estimate of what action should be taken by the secondary station; and
processing a second subset of the multipath signals based on a second window of arrival time that is greater than the first predefined window of arrival time to update the initial estimate.
5. The method as claimed in claim 4 , further comprising adjusting a power of uplink transmissions in response to power control commands received from the primary stations, the initial estimate including a next power change to be implemented by the secondary station.
6. The method as claimed in claim 5 , wherein the adjusting the power is according to the next power change, and further comprising subsequently correcting the power if the updated estimate differs from the initial estimate.
7. A transceiver comprising:
a signal generator, and
a plurality of RAKE fingers, each RAKE finger being configurable to provide an output signal corresponding to an identified path of a plurality of paths of a multi-path signal, and
a controller that is configured to control a transmit power of the transceiver based on the output signal from the plurality of RAKE fingers,
wherein the controller provides a first control of the transmit power based on output signals received from one or more of the RAKE fingers during a first predefined window of arrival time, and a subsequent control of the transmit power based on output signals received during a second window of arrival time that is greater than the first predefined window of arrival time.
8. The transceiver of claim 7 , wherein the controller is configured to allocate the identified path to each RAKE finger during the first window based on a time of arrival of signals from the plurality of paths.
9. The transceiver of claim 8 , wherein
the controller is configured to allocate the identified path to each RAKE finger during the second window based on a relative strength of signals from the plurality of paths.
10. The transceiver of claim 7 , wherein
the controller is configured to provide the first control based on a first occurring output signal from the plurality of RAKE fingers.
11. The transceiver of claim 7 , wherein
the controller is configured to provide the first control and subsequent control based on amplitudes of the output signals received during the first and second windows of arrival time, respectively.
12. The transceiver of claim 7 , wherein
the output signal from each of the one or more RAKE fingers is configured to indicate a request from a corresponding base station to increase or decrease the transmit power.
13. The transceiver of claim 12 , wherein
the controller is configured to determine whether to increase or decrease the transmit power via the first control based on a select one of the output signals received during the first time window, and whether to increase or decrease the transmit power via the subsequent control based on a plurality of the output signals received during the second time window.
14. The transceiver of claim 7 , wherein
the controller is configured to:
provide the first control based on a select one of the output signals received during the first time window, and
provide the subsequent control based on a plurality of the output signals received during the second time window.
15. The transceiver of claim 7 , wherein
each output signal corresponds to a signal transmitted from a corresponding base station of a plurality of base stations, and
the controller is configured to communicate a request to a select base station to adjust a transmit time from the select base station, to facilitate receipt of the signal transmitted from the select base station during the first predefined window of arrival time.
16. The transceiver of claim 15 , wherein
the controller is configured to select the select base station based on a strength of a received signal corresponding to the select base station.
17. The transceiver of claim 16 , wherein
the received signal is received after the first window of arrival time, and within the second window.