Technique for time alignment of uplink CDMA signals
First Claim
1. A method of using timing offsets in CDMA communications system reverse or uplinks between a number of subscriber stations and a base station, the method comprising:
- transmitting signals by the subscriber stations using default transmission timing offsets;
receiving said signals by the base station;
detecting various multipath components of said signals by said base station; and
when the base station determines that a subscriber station needs to change its transmission timing offsets, transmitting to said station a message identifying a new timing offset, based on the detected multipath components.
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Accused Products
Abstract
The present invention relates to communication systems and in particular relates to the time alignment of uplink CDMA signals. A simple approach for improving the performance of received CDMA signals is discussed. This consists of aligning the timings of users'"'"' signals such that the maximum output power from a single rake finger for each user occurs simultaneously. This allows the timing to be adjusted for each user'"'"'s signal independently of the others and has the effect of minimizing any interference between users. The invention provides a time alignment mechanism which employs a minimum of signalling.
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Citations
19 Claims
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1. A method of using timing offsets in CDMA communications system reverse or uplinks between a number of subscriber stations and a base station, the method comprising:
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transmitting signals by the subscriber stations using default transmission timing offsets;
receiving said signals by the base station;
detecting various multipath components of said signals by said base station; and
when the base station determines that a subscriber station needs to change its transmission timing offsets, transmitting to said station a message identifying a new timing offset, based on the detected multipath components. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A CDMA communications system comprising a number of subscriber stations and a base station, wherein;
- the subscriber stations are arranged to transmit signals using default transmission timing offsets;
the base station is arranged to receive said signals including detecting various multipath components of said signals; and
the base station is arranged to determine whether a subscriber station needs to change its transmission timing offset, and to transmit to said subscriber station a message identifying a new timing offset, based on the detected multipath components.
- the subscriber stations are arranged to transmit signals using default transmission timing offsets;
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13. A subscriber station for use in a CDMA communication system, the subscriber station arranged to transmit signals to a base station using a default transmission timing offset;
wherein said subscriber station is further arranged to receive a message from said base station to use a new timing offset, based on detected multipath components, and to a transmit said signal using said new timing offset, wherein said message is a command regularly transmitted by the base station advancing or retarding said timing offset by a predetermined amount. - View Dependent Claims (14)
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15. A base station for use in a CDMA communication system and arranged to receive signals from a number of subscriber stations using default transmission timing offsets;
- to detect various multipath components of said signals;
to determine whether a subscriber station needs to change its transmission timing offset, and to transmit to said subscriber station a message identifying a new timing offset, based on the detected multipath components. - View Dependent Claims (16, 17, 18, 19)
- to detect various multipath components of said signals;
Specification