Channel Precoding in a Wireless Communication System

Abstract

A base station receives channel state information from a wireless device. The base station transmits to the wireless device one or more data packets on a data channel employing a first precoding matrix identifier. The base station transmits one or more control packets on a control channel to the wireless device employing a second precoding matrix.

1 . A method comprising:
 receiving, by a base station from a wireless device, channel state information;   transmitting, by the base station, to the wireless device, and in a transmission time interval, a data channel comprising one or more data packets, wherein the data channel is precoded employing a first precoding matrix that is based on the channel state information; and   transmitting, by the base station, to the wireless device, and in the transmission time interval, a control channel comprising one or more control packets that comprise scheduling information for the data channel, wherein the control channel is precoded employing a second precoding matrix, different from the first precoding matrix, that is based on the channel state information.   
     
     
         2 . The method of  claim 1 , wherein:
 the data channel is transmitted via a first plurality of orthogonal frequency division multiplexed (OFDM) subcarriers, and   the control channel is transmitted via a second plurality of OFDM subcarriers that is different from the first plurality of OFDM subcarriers.   
     
     
         3 . The method of  claim 1 , wherein the second precoding matrix uses a smaller number of multiple-input-multiple-output (MIMO) layers than the first precoding matrix. 
     
     
         4 . The method of  claim 1 , wherein the second precoding matrix comprises a column vector. 
     
     
         5 . The method of  claim 1 , wherein the second precoding matrix comprises a submatrix of the first precoding matrix. 
     
     
         6 . The method of  claim 1 , wherein the second precoding matrix is based on a linear transformation on a subset of rows and columns of the first precoding matrix. 
     
     
         7 . The method of  claim 1 , wherein the second precoding matrix comprises a smaller number of columns than the first precoding matrix. 
     
     
         8 . The method of  claim 1 , further comprising transmitting, by the base station to the wireless device, channel state information reference signals, wherein the received channel state information is based on the channel state information reference signals. 
     
     
         9 . The method of  claim 1 , wherein the received channel state information is based on:
 channel state information reference signals transmitted by the base station and associated with the data channel; and   channel state information reference signals transmitted by the base station and associated with the control channel.   
     
     
         10 . The method of  claim 1 , wherein receiving the channel state information comprises:
 receiving first channel state information associated with the data channel; and   receiving second channel state information associated with the control channel.   
     
     
         11 . A base station comprising:
 one or more processors; and   memory storing instructions that, when executed by the one or more processors, configure the base station to:
 receive, from a wireless device, channel state information; 
 transmit, to the wireless device and in a transmission time interval, a data channel comprising one or more data packets, wherein the data channel is precoded employing a first precoding matrix that is based on the channel state information; and 
 transmit, to the wireless device and in the transmission time interval, a control channel comprising one or more control packets that comprise scheduling information for the data channel, wherein the control channel is precoded employing a second precoding matrix, different from the first precoding matrix, that is based on the channel state information. 
   
     
     
         12 . The base station of  claim 11 , wherein:
 the data channel is transmitted via a first plurality of orthogonal frequency division multiplexed (OFDM) subcarriers, and   the control channel is transmitted via a second plurality of OFDM subcarriers that is different from the first plurality of OFDM subcarriers.   
     
     
         13 . The base station of  claim 11 , wherein the second precoding matrix uses a smaller number of multiple-input-multiple-output (MIMO) layers than the first precoding matrix. 
     
     
         14 . The base station of  claim 11 , wherein the second precoding matrix comprises a column vector. 
     
     
         15 . The base station of  claim 11 , wherein the second precoding matrix comprises a submatrix of the first precoding matrix. 
     
     
         16 . The base station of  claim 11 , wherein the second precoding matrix is based on a linear transformation on a subset of rows and columns of the first precoding matrix. 
     
     
         17 . The base station of  claim 11 , wherein the second precoding matrix comprises a smaller number of columns than the first precoding matrix. 
     
     
         18 . The base station of  claim 11 , wherein the instructions, when executed by the one or more processors, further configure the base station to transmit, to the wireless device, channel state information reference signals, wherein the received channel state information is based on the channel state information reference signals. 
     
     
         19 . The base station of  claim 11 , wherein the received channel state information is based on:
 channel state information reference signals transmitted by the base station and associated with the data channel; and   channel state information reference signals transmitted by the base station and associated with the control channel.   
     
     
         20 . The base station of  claim 11 , wherein the instructions, when executed by the one or more processors, configure the base station to receive the channel state information by:
 receiving first channel state information associated with the data channel; and   receiving second channel state information associated with the control channel.   
     
     
         21 . A system comprising:
 a base station and a wireless device,   wherein the base station is configured to:
 receive, from the wireless device, channel state information; 
 transmit, to the wireless device and in a transmission time interval, a data channel comprising one or more data packets, wherein the data channel is precoded employing a first precoding matrix that is based on the channel state information; and 
 transmit, to the wireless device and in the transmission time interval, a control channel comprising one or more control packets that comprise scheduling information for the data channel, wherein the control channel is precoded employing a second precoding matrix, different from the first precoding matrix, that is based on the channel state information, and 
   wherein the wireless device is configured to transmit the channel state information.   
     
     
         22 . The system of  claim 21 , wherein:
 the data channel is transmitted via a first plurality of orthogonal frequency division multiplexed (OFDM) subcarriers, and   the control channel is transmitted via a second plurality of OFDM subcarriers that is different from the first plurality of OFDM subcarriers.   
     
     
         23 . The system of  claim 21 , wherein the second precoding matrix uses a smaller number of multiple-input-multiple-output (MIMO) layers than the first precoding matrix. 
     
     
         24 . The system of  claim 21 , wherein the second precoding matrix comprises a column vector. 
     
     
         25 . The system of  claim 21 , wherein the second precoding matrix comprises a submatrix of the first precoding matrix. 
     
     
         26 . The system of  claim 21 , wherein the second precoding matrix is based on a linear transformation on a subset of rows and columns of the first precoding matrix. 
     
     
         27 . The system of  claim 21 , wherein the second precoding matrix comprises a smaller number of columns than the first precoding matrix. 
     
     
         28 . The system of  claim 21 , wherein the base station is further configured to transmit, to the wireless device, channel state information reference signals, wherein the received channel state information is based on the channel state information reference signals. 
     
     
         29 . The system of  claim 21 , wherein the received channel state information is based on:
 channel state information reference signals transmitted by the base station and associated with the data channel; and   channel state information reference signals transmitted by the base station and associated with the control channel.   
     
     
         30 . The system of  claim 21 , wherein the base station is configured to receive the channel state information by:
 receiving first channel state information associated with the data channel; and   receiving second channel state information associated with the control channel.