Multi-user MIMO transmissions in wireless communication systems

Abstract

An apparatus and method for providing control information in a Multi User-Multiple Input Multiple Output (MU-MIMO) wireless communication system is provided. The method includes receiving a plurality of Resource Elements (REs) including Downlink Control Information (DCI), determining, using the DCI, a set of REs to which a plurality of Downlink Reference Signals (DRSs) may be mapped, determining remaining REs as REs to which data is mapped, and demodulating the data using a precoding vector of a DRS corresponding to the MS.

What is claimed is: 
     
       1. A method for determining a power ratio of Resource Elements (REs) transmitted by a Mobile Station (MS), the method comprising:
 determining a type of multiplexing used for multiplexing the Dedicated Reference Signals (DRS) REs;   if the type of multiplexing is determined to be one of Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM), determining if the number of DRSs transmitted by the BS is known;   if the number of transmitted DRSs is known, setting the Physical Downlink Shared Channel (PDSCH) data to DRS power ratio to correspond to the number of transmitted DRSs; and   if the number of transmitted DRSs is not known, determining if the maximum number of DRSs that may be transmitted is known;   if the maximum number of DRSs that may be transmitted is known:   setting the power ratio to correspond to a maximum number of DRSs that may be transmitted; and   otherwise setting the power ratio to 0 dB.   
     
     
       2. The method of  claim 1 , wherein the setting of the power ratio to correspond to the number of transmitted DRSs comprises using the equation:
   γ[dB]=−10log 10 (N_DRS),
   where γ[dB] comprises the power ratio and N_DRS comprises the number of transmitted DRSs.   
     
     
       3. The method of  claim 1 , wherein the setting of the power ratio to correspond to the maximum number of DRSs that may be transmitted comprises using the equation:
   γ[dB]=−10 log 10 (M),
   where γ[dB] comprises the power ratio and M comprises the maximum number of DRSs that may be transmitted.   
     
     
       4. The method of  claim 1 , wherein, if the type of modulation is determined to be Code Division Multiplexing (CDM), setting the power ratio to 0 dB. 
     
     
       5. A method for determining a power ratio of Resource Elements (REs) transmitted by a Mobile Station (MS), the method comprising:
 determining a type of multiplexing used for multiplexing Dedicated Reference Signal (DRS) REs;   if the type of multiplexing is determined to be one of Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM), determining if the number of DRSs transmitted by a Base Station (BS) is known;   if the number of transmitted DRSs is known, setting Physical Downlink Shared Chanel (PDSCH) data to DRS power ratio to correspond to the number of transmitted DRSs;   if the number of transmitted DRSs is not known, determining if the maximum number of DRSs that may be transmitted is known;   if the type of multiplexing is determined to be a hybrid of CDM and one of FDM and TDM, determining if the number of DRSs transmitted by the BS is known; and   if the number of transmitted DRSs is known, setting the power ratio to correspond to the number of transmitted DRSs and a spreading length used for the CDM.   
     
     
       6. The method of  claim 5 , wherein, if the total number of DRS sets that are transmitted is known:
 setting the power ratio to correspond to the total number of DRS sets that are transmitted; and   otherwise setting the power ratio to 0 dB.   
     
     
       7. The method of  claim 6 , wherein the setting of the power ratio to correspond to the number of transmitted DRSs and a spreading length used for the CDM comprises using the equation:
   γ[dB]=−10 log 10 (N_DRS)+10 log 10 (N_SF),
   where γ[dB] comprises the power ratio, N_DRS comprises the number of transmitted DRSs, and N_SF comprises the spreading length used for the CDM.   
     
     
       8. The method of  claim 5 , wherein, if the type of multiplexing is determined to be a hybrid of CDM and one of FDM and TDM, determining if the number of CDMed DRS sets and the number of DRSs transmitted by the BS are known, and determining if the number of total transmission layers is an odd number and that is greater than 1; and
 if the number of total transmission layers is an odd number and the transmission layers are split into two CDMed DRS sets, applying different power ratios to the layers in the two CDMed DRS sets.   
     
     
       9. The method of  claim 8 , wherein, if it is determined that three transmission layers are split into two CDMed DRS sets, applying the power ratio to the set with 2 layers as:
   γ[dB]=−10 log 10 (N_DRS)+10 log 10 (N_SF),
   and applying the power ratio to the set with 1 layer as:
   γ[dB]=10 log 10 (N_SET).
 
   
     
     
       10. A method for determining a power ratio of Resource Elements (REs) transmitted by a Mobile Station (MS), the method comprising:
 determining a type of multiplexing used for multiplexing Dedicated Reference Signal (DRS) REs;   if the type of multiplexing is determined to be one of Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM), determining if the number of DRSs transmitted by a Base Station (BS) is known;   if the number of transmitted DRSs is known, setting Physical Downlink Shared Chanel (PDSCH) data to DRS power ratio to correspond to the number of transmitted DRSs;   if the number of transmitted DRSs is not known, determining if the maximum number of DRSs that may be transmitted is known;   if the type of multiplexing is determined to be a hybrid of CDM and one of FDM and TDM, determining if the number of CDMed DRS sets transmitted by the BS is known; and   if the number of CDMed DRS sets is known, setting the power ratio to correspond to the number of CDMed DRS sets.   
     
     
       11. The method of  claim 10 , wherein the setting of the power ratio to correspond to the total number of DRS sets that are transmitted comprises using the equation:
   γ[dB]=−10 log 10 (N_SET),
   where γ[dB] comprises the power ratio and N_SET comprises the total number of DRS sets that are transmitted.   
     
     
       12. A method for transmitting a signal in a communication system, the method comprising:
 determining a ratio of physical downlink shared channel (PDSCH) energy per resource element (EPRE) to mobile specific reference signal EPRE based on a number of layers;   transmitting downlink control information including Hybrid Automatic Repeat reQuest (HARQ) information, mobile specific reference signal information, modulation and coding scheme information per a transport block, and new data indicator information per the transport block; and   transmitting data on the PDSCH according to the determined ratio and based on the downlink control information.    
     
     
       13. The method of claim 12, wherein the number of layers is equal to a number of mobile specific reference signals.  
     
     
       14. The method of claim 12, wherein indices of mobile specific reference signals indicated by the mobile specific reference signal information are consecutive.  
     
     
       15. The method of claim 12, wherein an L th  layer is associated with an index of mobile specific reference signal, i_DRS+L−1.  
     
     
       16. The method of claim 12, wherein a mobile specific reference signal is defined by applying code division multiplexing and frequency division multiplexing.  
     
     
       17. The method of claim 12, wherein the data is mapped onto resource elements other than cell specific reference signal resource elements and mobile specific reference signal resource elements.  
     
     
       18. An apparatus for transmitting a signal in a communication system, the apparatus comprising:
 control circuitry configured to determine a ratio of physical downlink shared channel (PDSCH) energy per resource element (EPRE) to mobile specific reference signal EPRE based on a number of layers; and   a transmitter configured to transmit downlink control information including Hybrid Automatic Repeat reQuest (HARQ) information, mobile specific reference signal information, modulation and coding scheme information per a transport block, new data indicator information per the transport block, and to transmit data on the PDSCH according to the determined ratio and based on the downlink control information.    
     
     
       19. The apparatus of claim 18, wherein the number of layers is equal to a number of mobile specific reference signals.  
     
     
       20. The apparatus of claim 18, wherein indices of multiple mobile specific reference signals indicated by the mobile specific reference signal information are consecutive.  
     
     
       21. The apparatus of claim 18, wherein a L th  layer is associated with an index of mobile specific reference signal, i_DRS+L−1.  
     
     
       22. The apparatus of claim 18, wherein a mobile specific reference signal is defined by applying code division multiplexing and frequency division multiplexing.  
     
     
       23. The apparatus of claim 18, wherein the data is mapped onto resource elements other than cell specific reference signal resource elements and mobile specific reference signal resource elements.  
     
     
       24. A method for receiving a signal in a communication system, the method comprising:
 receiving downlink control information including Hybrid Automatic Repeat reQuest (HARQ) information, mobile specific reference signal information, modulation and coding scheme information per a transport block, new data indicator information per the transport block;   obtaining a ratio of physical downlink shared channel (PDSCH) energy per resource element (EPRE) to mobile specific reference signal EPRE based on a number of layers; and   receiving data that has been transmitted on the PDSCH according to the obtained ratio and based on the downlink control information.    
     
     
       25. The method of claim 24, wherein the number of layers is equal to a number of mobile specific reference signals.  
     
     
       26. The method of claim 24, wherein indices of mobile specific reference signals indicated by the mobile specific reference signal information are consecutive.  
     
     
       27. The method of claim 24, wherein an L th  layer is associated with an index of mobile specific reference signal, i_DRS+L−1.  
     
     
       28. The method of claim 24, wherein a mobile specific reference signal is defined by applying code division multiplexing and frequency division multiplexing.  
     
     
       29. The method of claim 24 wherein the data is mapped onto resource elements other than cell specific reference signal resource elements and mobile specific reference signal resource elements.  
     
     
       30. An apparatus for receiving a signal in a communication system, the apparatus comprising:
 a receiver configured to receive downlink control information including Hybrid Automatic Repeat reQuest (HARQ) information, mobile specific reference signal information, modulation and coding scheme information per a transport block, new data indicator information per the transport block; and   control circuitry configured to obtain a ratio of physical downlink shared channel (PDSCH) energy per resource element (EPRE) to mobile specific reference signals (RSs) based on a number of layers,   wherein the receiver is configured to receive data that has been transmitted on the PDSCH according to the obtained ratio and based on the downlink control information.    
     
     
       31. The apparatus of claim 30, wherein the number of layers is equal to a number of mobile specific reference signals.  
     
     
       32. The apparatus of claim 30, wherein indices of multiple mobile specific reference signals indicated by the mobile specific reference signal information are consecutive.  
     
     
       33. The apparatus of claim 30, wherein a L th  layer is associated with an index of mobile specific reference signal, i_DRS+L−1.  
     
     
       34. The apparatus of claim 30, wherein a mobile specific reference signal is defined by applying code division multiplexing and frequency division multiplexing.  
     
     
       35. The apparatus of claim 30, wherein the data is mapped onto resource elements other than cell specific reference signal resource elements and mobile specific reference signal resource elements.