Methods and arrangements for csi reporting

Abstract

Some embodiments provide a method in a wireless device for reporting channel state information, CSI, for a CSI process. The CSI process corresponds to a reference signal resource and an interference measurement resource. According to the method, the wireless device obtains an adjustment value associated with the CSI process. The wireless device estimates an effective channel based on one or more reference signals received in the reference signal resource, and applies the adjustment value to the estimated effective channel, thereby obtaining an adjusted effective channel. Furthermore, the wireless device determines channel state information based on the adjusted effective channel, and on interference estimated based on the interference measurement resource. Finally, the channel state information is transmitted to a network node.

1 . A method in a wireless device for reporting channel state information, CSI, for a CSI process, the CSI process corresponding to a reference signal resource and an interference measurement resource, the method characterized in:
 obtaining an adjustment value associated with the CSI process;   estimating an effective channel based on one or more reference signals received in the reference signal resource;   applying the adjustment value to the estimated effective channel, obtaining an adjusted effective channel;   determining channel state information based on the adjusted effective channel, and on interference estimated based on the interference measurement resource; and   transmitting the channel state information to a network node.   
     
     
         2 . The method of  claim 1 , wherein the CSI process further corresponds to one or more interference emulation configurations, wherein each interference emulation configuration is associated with a reference signal received from an assumed interferer, the method further comprising:
 estimating, for each interference emulation configuration, an effective channel based on the associated reference signal;   emulating interference for each interference emulation configuration based on the estimated effective channel for that configuration; and   determining channel state information based also on the emulated interference.   
     
     
         3 . The method of  claim 2 , further comprising applying the adjustment value to the emulated interference for each interference emulation configuration. 
     
     
         4 . The method of  claim 2 , further comprising obtaining a second adjustment value for the interference emulation configurations, and applying the second adjustment value to the emulated interference for each configuration. 
     
     
         5 . The method of  claim 1 , wherein the CSI process corresponds to at least two reference signal resources, and wherein an adjustment value is associated with each one of the reference signal resources. 
     
     
         6 . The method of  claim 5 , further comprising:
 for each reference signal resource of the CSI process, estimating an effective channel based on one or more reference signals received in the reference signal resource, and applying the adjustment value associated with the reference signal resource to the estimated effective channel, obtaining an adjusted effective channel; and   determining channel state information based on the adjusted effective channels, and on estimated interference.   
     
     
         7 . The method of  claim 1 , wherein the adjustment value is a power measurement offset. 
     
     
         8 . The method of  claim 7 , wherein the method further comprises applying an additional non-CSI process-specific power offset to the estimated effective channel. 
     
     
         9 . The method of  claim 8 , wherein the reference signal is a channel state information reference signal, CSI-RS, and wherein the additional power offset is associated with the CSI-RS. 
     
     
         10 . The method of  claim 1 , wherein the adjustment value is a scaling factor. 
     
     
         11 . The method of  claim 1 , further comprising determining channel state information for at least one other CSI process based on the adjustment value. 
     
     
         12 . The method of  claim 1 , wherein the adjustment value is obtained from a network node. 
     
     
         13 . The method of  claim 1 , further comprising receiving an index from a network node, and obtaining the adjustment value by retrieving the adjustment value corresponding to the index from a predefined lookup table. 
     
     
         14 . The method of  claim 1 , wherein the channel state information comprises one or more of: a channel quality indicator, a precoding matrix indicator, a rank indication, and a precoding matrix type. 
     
     
         15 . The method of  claim 1  wherein the wireless device is configured with two CSI processes corresponding to the same reference signal resource, and associated with different adjustment values. 
     
     
         16 . The method of  claim 1 , wherein the reference signal resource comprises a set of resource elements in which one or more reference signals corresponding to a desired signal are received, and wherein the interference measurement resource comprises a set of resource elements in which one or more signals assumed to be interfering with the desired signal are received. 
     
     
         17 . The method of  claim 1 , wherein the reference signal resource is a CSI-RS resource. 
     
     
         18 . The method of  claim 1 , wherein the interference measurement resource is a cell-specific reference signal resource, and wherein interference is estimated by subtracting a decoded cell-specific reference signal from the signal received in the cell-specific reference signal resource. 
     
     
         19 . A method in a network node for receiving, from a wireless device, channel state information, CSI, for a CSI process, the CSI process corresponding to a reference signal resource and an interference measurement resource, the network node being comprised in a cluster for coordinated multipoint transmission, the method characterized in:
 transmitting, to the wireless device, an indication of an adjustment value associated with the CSI process;   receiving channel state information related to the CSI process from the wireless device.   
     
     
         20 . The method of  claim 19 , wherein the reference signal resource comprises a set of resource elements in which one or more reference signals corresponding to a signal intended for reception by the wireless device are transmitted, and wherein the interference measurement resource comprises a set of resource elements in which one or more signals assumed to be interfering with the desired signal are received.