Group MIMO

Abstract

This disclosure relates to performing grouped MIMO communications in a cellular communication system. A cellular base station may select a precoding matrix for transmitting a downlink signal to a wireless device via a MIMO channel. The selected precoding matrix may have unequal weights for different MIMO subchannels. The downlink signal may be precoded using the selected precoding matrix. The precoded downlink signal may be transmitted to the wireless device via the MIMO channel. The wireless device may receive and decode the downlink signal.

1 . A wireless device, comprising:
 a plurality of antennas;   a radio operably coupled to the plurality of antennas; and   a processor operably coupled to the radio, wherein the wireless device is configured to:
 transmit channel state information (CSI) to a cellular base station relating to a downlink multiple input multiple output (MIMO) channel, wherein the CSI provides information related to unequal weighting corresponding to different MIMO subchannels of the MIMO channel, and wherein each different MIMO subchannel corresponds to a different MIMO layer; and 
 decode a received downlink signal based on the CSI. 
   
     
     
         2 . The wireless device of  claim 1 , wherein the cellular base station includes multiple antennas, wherein the multiple antennas are associated with disjoint groups of antennas, and wherein the MIMO subchannels are associated with respective ones of the disjoint groups of antennas. 
     
     
         3 . The wireless device of  claim 1 , wherein the unequal weights relate to power levels for the different MIMO subchannels. 
     
     
         4 . The wireless device of  claim 1 , wherein the unequal weights relate to channel gains for the different MIMO subchannels. 
     
     
         5 . The wireless device of  claim 1 , wherein the received downlink signal is received on the different MIMO subchannels, wherein the different MIMO subchannels comprise a stronger group of MIMO subchannels and a weaker group of MIMO subchannels, wherein, in decoding the received downlink signal based on the CSI, the wireless device is configured to:
 decode the stronger group of MIMO subchannels;   null the stronger group of MIMO subchannels from the received downlink signal; and   decode the weaker group of MIMO subchannels with the stronger group of MIMO subchannels nulled.   
     
     
         6 . The wireless device of  claim 1 ,
 wherein said decoding the received downlink signal based on the CSI comprises selecting a precoding matrix for decoding the received downlink signal based on the information related to the unequal weighting corresponding to the different MIMO subchannels of the MIMO channel.   
     
     
         7 . The wireless device of  claim 6 ,
 wherein the precoding matrix has a block diagonal format.   
     
     
         8 . An apparatus, comprising:
 a processor configured to cause a user equipment (UE) to:
 transmit channel state information (CSI) to a cellular base station relating to a downlink multiple input multiple output (MIMO) channel, wherein the CSI provides information related to unequal weighting corresponding to different MIMO subchannels of the MIMO channel, and wherein each different MIMO subchannel corresponds to a different MIMO layer; and 
 decode a received downlink signal based on the CSI. 
   
     
     
         9 . The apparatus of  claim 8 , wherein the cellular base station includes multiple antennas, wherein the multiple antennas are associated with disjoint groups of antennas, and wherein the MIMO subchannels are associated with respective ones of the disjoint groups of antennas. 
     
     
         10 . The apparatus of  claim 8 , wherein the unequal weights relate to power levels for the different MIMO subchannels. 
     
     
         11 . The apparatus of  claim 8 , wherein the unequal weights relate to channel gains for the different MIMO subchannels. 
     
     
         12 . The apparatus of  claim 8 , wherein the received downlink signal is received on the different MIMO subchannels, wherein the different MIMO subchannels comprise a stronger group of MIMO subchannels and a weaker group of MIMO subchannels, wherein, in decoding the received downlink signal based on the CSI, the processor is configured to cause the UE to:
 decode the stronger group of MIMO subchannels;   null the stronger group of MIMO subchannels from the received downlink signal; and   decode the weaker group of MIMO subchannels with the stronger group of MIMO subchannels nulled.   
     
     
         13 . The apparatus of  claim 8 ,
 wherein said decoding the received downlink signal based on the CSI comprises selecting a precoding matrix for decoding the received downlink signal based on the information related to the unequal weighting corresponding to the different MIMO subchannels of the MIMO channel.   
     
     
         14 . The apparatus of  claim 13 ,
 wherein the precoding matrix has a block diagonal format.   
     
     
         15 . A method for operating a wireless device, the method comprising:
 transmitting channel state information (CSI) to a cellular base station relating to a downlink multiple input multiple output (MIMO) channel, wherein the CSI provides information related to unequal weighting corresponding to different MIMO subchannels of the MIMO channel, and wherein each different MIMO subchannel corresponds to a different MIMO layer; and   decoding a received downlink signal based on the CSI.   
     
     
         16 . The method of  claim 15 , wherein the cellular base station includes multiple antennas, wherein the multiple antennas are associated with disjoint groups of antennas, and wherein the MIMO subchannels are associated with respective ones of the disjoint groups of antennas. 
     
     
         17 . The method of  claim 15 , wherein the unequal weights relate to power levels for the different MIMO subchannels. 
     
     
         18 . The method of  claim 15 , wherein the unequal weights relate to channel gains for the different MIMO subchannels. 
     
     
         19 . The method of  claim 15 , wherein the received downlink signal is received on the different MIMO subchannels, wherein the different MIMO subchannels comprise a stronger group of MIMO subchannels and a weaker group of MIMO subchannels, wherein decoding the received downlink signal based on the CSI comprises:
 decoding the stronger group of MIMO subchannels;   nulling the stronger group of MIMO subchannels from the received downlink signal; and   decoding the weaker group of MIMO subchannels with the stronger group of MIMO subchannels nulled.   
     
     
         20 . The method of  claim 15 ,
 wherein said decoding the received downlink signal based on the CSI comprises selecting a precoding matrix for decoding the received downlink signal based on the information related to the unequal weighting corresponding to the different MIMO subchannels of the MIMO channel.