Method and apparatus for closed loop transmit diversity transmission initial access

Abstract

Uplink precoding in closed loop transmit diversity (CLTD). The methods and apparatus relate to precoder operations during an initial stage using default precoder tap weights, and a second stage wherein precoder weights obtained from a precoder control indicator channel information are used, provided the signal quality of the precoder control indicator channel is sufficiently reliable. The methods and apparatus also relate to procedures for responding to detection of an unreliable pre-coding control information (PCI) carried in a downlink feedback signal.

What is claimed is: 
     
         1 . A method of operating a Wireless Transmit Receive Unit (WTRU) in a transmit diversity mode, the method comprising:
 upon entering a transmit diversity mode, transmitting a signal having at least first and second streams using default precoder weights;   receiving precoder control information on a precoder control information channel;   determining a quality of the precoder control information;   responsive to determining that the quality of the precoder control information is above a threshold, transmitting the dual-stream signal using second precoder weights determined based on the precoder control information.   
     
     
         2 . The method of  claim 1  wherein the default precoder weights are weights that are not based on current channel conditions for the transmitted first and second streams. 
     
     
         3 . The method of  claim 1  wherein the determining the second precoder weights comprises selecting the second precoder weights from a precoder codebook based on the precoder control information, the precoder codebook comprising a plurality of sets of precoder weights. 
     
     
         4 . The method of  claim 1  wherein the default precoder weights comprise one of the plurality of sets of precoder weights comprising the precoder codebook. 
     
     
         5 . The method of  claim 1  further comprising receiving a parameter indicating resource information of the precoder control information channel. 
     
     
         6 . The method of  claim 5  wherein the resource information is a channelization code and a slot format. 
     
     
         7 . The method of  claim 1  wherein the dual-stream signal includes a control channel in a first stream and a pilot signal channel in a second stream. 
     
     
         8 . The method of  claim 1  wherein the dual-stream signal includes a control channel and a data channel in a first stream and a pilot signal channel in a second stream. 
     
     
         9 . The method of  claim 8  wherein the default precoder weights and the second precoder weights each comprise a first weight and a second weight that are applied to the first stream and a third weight and a fourth weight that are applied to the second stream. 
     
     
         10 . The method of  claim 1  wherein the determining the quality indicator of the precoder control information channel comprises determining a signal-to-noise ratio on the precoder control information channel. 
     
     
         11 . The method of  claim 1  wherein the determining the quality indicator of the precoder control information channel comprises determining a received signal strength on the precoder control information channel. 
     
     
         12 . The method of  claim 1  wherein the WTRU is in a Cell_FACH (Forward Access Channel) mode upon the initialization of the transmit diversity. 
     
     
         13 . The method of  claim 1  wherein the WTRU is in a Cell_DCH (Dedicated Control Channel) mode upon the initialization of the transmit diversity. 
     
     
         14 . A wireless transmit-receive unit (WTRU) comprising:
 a receiver configured to receive precoder control information on a precoder control information channel;   a transmitter configured to transmit a dual-stream signal using precoder weights;   a precoder feedback processor configured to:   upon initialization of a transmit diversity mode, configure the transmitter to transmit the dual-stream signal using a first set of precoder weights, wherein the first set of precoder weights are default precoder weights;   determine the precoder control information received on the precoder control information channel,   determine a quality of the precoder control information; and,   when the quality of the precoder control information is above a threshold, configure the transmitter to transmit the dual-stream signal using a second set of precoder weights, the second set of precoder weights being based on the precoder control information.   
     
     
         15 . The WTRU of  claim 14  wherein the default precoder weights are weights that are not based on current channel conditions for the transmitted first and second streams. 
     
     
         16 . The WTRU of  claim 14  wherein the precoder feedback processor is configured to determine the second precoder weights by selecting the second precoder weights from a precoder codebook based on the precoder control information, the precoder codebook comprising a plurality of sets of precoder weights. 
     
     
         17 . The WTRU of  claim 14  wherein the default precoder weights comprise one of the plurality of sets of precoder weights comprising the precoder codebook. 
     
     
         18 . The WTRU of  claim 14  wherein the receiver is configured to receive a parameter indicating resource information of the precoder control information channel. 
     
     
         19 . The WTRU of  claim 18  wherein the resource information is a channelization code and a slot format. 
     
     
         20 . The WTRU of  claim 14  wherein the transmitter is configured to transmit the dual-stream signal including a control channel in a first stream and a pilot signal channel in a second stream. 
     
     
         21 . The WTRU of  claim 14  wherein the transmitter is configured to transmit the dual-stream signal including a control channel and a data channel in a first stream and a pilot signal channel in a second stream. 
     
     
         22 . The WTRU of  claim 21  wherein the default precoder weights and the second precoder weights each comprise a first weight and a second weight that are applied to the first stream and a third weight and a fourth weight that are applied to the second stream. 
     
     
         23 . The WTRU of  claim 14  wherein the precoder feedback processor is configured to determine the quality indicator of the precoder control information channel by determining a signal-to-noise ratio on the precoder control information channel. 
     
     
         24 . The WTRU of  claim 14  wherein the precoder feedback processor is configured to determine the quality indicator of the precoder control information channel by determining a received signal strength on the precoder control information channel. 
     
     
         25 . The WTRU of  claim 14  wherein the WTRU is in a Cell_FACH (Forward Access Channel) mode at the initialization of the transmit diversity. 
     
     
         26 . The WTRU of  claim 14  wherein the WTRU is in a Cell_DCH (Dedicated Control Channel) mode at the initialization of the transmit diversity.