Closed-Loop MIMO Systems and Methods

Abstract

Methods, devices and systems are provided for transmitting and receiving MIMO signals. In one embodiment, transmitting of the MIMO signals involves pre-coding each of at least two data symbols using a respective pre-coding codeword to preclude a corresponding plurality of pre-coded data symbols. A respective signal is transmitted from each of a plurality of antennas, the respective signal including one of the pre-coded signals and at least one pilot for use in channel estimation. The signals collectively further include at least one beacon pilot vector consisting of a respective beacon pilot per antenna, the beacon pilot vector containing contents known to a receiver for use by the receiver in determining the codeword used to pre-code the at least one data signal.

1 - 29 . (canceled) 
     
     
         30 . A base station, comprising:
 a baseband processor configured to pre-code each of at least two data symbols using a respective pre-coding codeword to produce a corresponding plurality of pre-coded data symbols; and   a plurality of antennas, each configured to transmit a respective signal, each respective signal comprising one of the pre-coded data symbols and at least one pilot symbol;
 wherein each transmitted signal is an Orthogonal Frequency Division Multiplexing (OFDM) signal, and wherein for each antenna the respective signal comprises a null in each sub-carrier and time location used to transmit the at least one pilot symbol in the respective signal of each other antenna. 
   
     
     
         31 . The base station of  claim 30 , further comprising:
 transmit circuitry configured to modulate each of the plurality of pre-coded data symbols to generate each of the respective signals.   
     
     
         32 . The base station of  claim 30 , wherein the signals collectively further comprising at least one beacon pilot vector including a respective beacon pilot per antenna, the beacon pilot vector containing contents known to a receiver for use by the receiver in determining the codeword used to pre-code the at least one data signal. 
     
     
         33 . The base station of  claim 32 , wherein the beacon pilot vector is transmitted without pre-coding. 
     
     
         34 . The base station of  claim 32 , wherein the beacon pilot vector is transmitted with pre-coding. 
     
     
         35 . The base station of  claim 30 , wherein the baseband processor is configured to receive an indication of a channel quality indicator of a connection with a receiver of the signals and select the respective pre-coding codeword based on the channel quality indicator. 
     
     
         36 . The base station of  claim 30 , wherein the baseband processor is configured to receive feedback indicating which pre-coding codeword to use. 
     
     
         37 . The base station of  claim 30 , wherein the baseband processor is implemented as one of a digital signal processor or an application specific integrated circuit. 
     
     
         38 . A mobile terminal, comprising:
 a first receive antenna configured to receive a first Orthogonal Frequency Division Multiplexing (OFDM) signal including (i) data symbols pre-coded with a codeword and (ii) pilot symbols;   a second receive antenna configured to receive a second OFDM signal, wherein the second OFDM signal comprises a null in a sub-carrier and a time location used to transmit the pilot symbols in the first OFDM signal; and   a baseband processor configured to process the pilot symbols to determine which codeword was used to pre-code the data symbols.   
     
     
         39 . The mobile terminal of  claim 38 , wherein the pilot symbols are included in a beacon pilot vector. 
     
     
         40 . The mobile terminal of  claim 38 , wherein the first and second OFDM signals are Multiple Input Multiple Output (MIMO) signals. 
     
     
         41 . The mobile terminal of  claim 38 , further comprising:
 receive circuitry interposed between the first and second receive antennas and the baseband processor, the receive circuitry configured to demodulate the first and second OFDM signals prior to the baseband processor processing the first and second OFDM signals.   
     
     
         42 . The mobile terminal of  claim 38 , wherein the baseband processor is configured to determine if the determined codeword was a codeword expected to be used. 
     
     
         43 . The mobile terminal of  claim 38 , further comprising:
 transmit circuitry, wherein the transmit circuitry and at least one of the first and second receive antennas are configured to transmit a signal to a device that transmitted the first and second OFDM signals, wherein the signal is used by the device to select the codeword.   
     
     
         44 . The mobile terminal of  claim 38 , wherein the baseband processor is configured to perform channel estimation using the pilot symbols to produce channel estimates. 
     
     
         45 . A method, comprising:
 at an integrated circuit:
 pre-coding each of at least two data symbols using a respective pre-coding codeword to produce a corresponding plurality of pre-coded data symbols; and 
 generating transmission signals, each transmission signal comprising one of the pre-coded data symbols and at least one pilot symbol, the generating further comprising:
 inserting a null in each sub-carrier and time location in each transmission signal that corresponds to a sub-carrier and time location of the at least one pilot symbol in each of the other transmission signals. 
 
   
     
     
         46 . The method of  claim 45 , further comprising:
 at the integrated circuit:
 pre-coding at least one beacon pilot vector, wherein the transmission signals collectively further comprise the at least one beacon pilot vector including a respective beacon pilot per antenna on which the respective transmission signal is to be transmitted, the beacon pilot vector containing contents known to a receiver for use by the receiver in determining the codeword used to pre-code the at least one data signal. 
   
     
     
         47 . The method of  claim 45 , further comprising:
 at the integrated circuit:
 receiving an indication of a channel quality indicator of a connection with a receiver of the transmission signals; and 
 selecting the respective pre-coding codeword based on the channel quality indicator. 
   
     
     
         48 . The method of  claim 45 , wherein each transmission signal is an Orthogonal Frequency Division Multiplexing (OFDM) signal. 
     
     
         49 . The method of  claim 45 , wherein the method is performed for each of a plurality of frequency division duplex (FDD) or time division duplex (TDD) Multiple Input Multiple Output (MIMO) radio resources.