Secondary station and method of operating the station
View Patent ↗A secondary station has a receiver capable of resolving signals received as a plurality of multipath signals from a plurality of base stations during a soft handover process. This capability may, for example, be provided by a Rake receiver. In order to decode and act upon the received signals in a very short period of time, signals ( 402 g, 402 h ) arriving after a predetermined time are not processed by the receiver which is able instead to process weaker signals ( 402 d, 402 e ) which arrived before the time (t 1 ). 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. In this application the predetermined time (t 1 ) is the time after which signals are received too late for use in determining the next power control change.
1. A secondary station for use in a radio communication system comprising a plurality of primary stations, the secondary station having means for engaging in a soft handover process, in which the secondary station communicates simultaneously with at least two primary stations, and receiver means including means for signal resolution which resolves transmitted signals from the at least two primary stations received as a plurality of multipath signals, wherein means are provided for determining whether to allocate each multipath signal to the signal resolution means based on whether its time of arrival occurs within a window of arrival.
2. A secondary station as claimed in claim 1 , characterised in that the signal resolution means comprises a Rake receiver having a plurality of fingers.
3. A secondary station as claimed in claim 1 , characterised in that power control means are provided for adjusting the power of uplink transmissions in response to power control commands received from the primary stations and in that the signal resolution means are operable to resolve power control commands received via a plurality of multipath signals.
4. A secondary station as claimed in claim 3 , characterised in that the power control means adjusts transmission power at predetermined times and in that late signals, having a time of arrival which is less than a predetermined interval before the next time for adjustment of transmission power, are not allocated to the signal resolution means.
5. A secondary station as claimed in claim 4 , characterised in that at least some of the late signals are used in the determination of a subsequent power control adjustment.
6. 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, and processing the received multipath signals by a signal resolver to resolve the transmitted signals, the method further comprising determining whether to process each multipath signal based on whether its time of arrival occurs within a window of arrival.
7. A method as claimed in claim 6 , characterised by the signal resolver being a Rake receiver having a plurality of fingers.
8. A method as claimed in claim 6 , characterised by adjusting the power of uplink transmissions in response to power control commands received from the primary stations and by resolving power control commands received via a plurality of multipath signals.
9. A method as claimed in claim 8 , characterised by adjusting transmission power at predetermined times and by late signals, having a time of arrival which is less than a predetermined interval before the next time for adjustment of transmission power, not being processed by the signal resolver.
10. A method as claimed in claim 9 , characterised by at least some of the late signals being used in the determination of a subsequent power control adjustment.