Receiving a pilot design and channel estimation

Abstract

A receiver in an OFDM based communication system is adapted to perform channel estimation using a received reference signal transmitted from at least one antenna The reference signal is substantially located into at least two OFDM symbols of a transmission time interval comprising of more than two OFDM symbols. A power level of said reference signal is divided into said non-consecutive OFDM symbols in said transmission time interval and adapted to use the reference signal located in a first OFDM symbol in succeeding transmission time intervals in addition to the reference symbols in a current transmission time interval and a preceding transmission time interval.

What is claimed is: 
     
       1. A receiver in an orthogonal frequency division multiplexing OFDM based communication system including: a processor adapted to perform channel estimation using a received reference signal transmitted from at least one antenna, said reference signal being substantially located into at least two non-consecutive OFDM symbols of a transmission time interval comprising of more than two OFDM symbols and a power level of said reference signal is divided into said non-consecutive OFDM symbols in said transmission time interval and adapted to use the reference signal located in a first OFDM symbol in succeeding transmission time intervals in addition to the reference symbols in a current transmission time interval and a preceding transmission time intervals. 
     
     
       2. An apparatus for an orthogonal frequency division multiplexing (OFDM) based communication system, said apparatus:
 adapted to perform channel estimation using a received reference signal transmitted from a plurality of transmitting antennas, said reference signal being substantially located into two non-consecutive OFDM symbols of a current transmission time interval for each transmit antenna, said transmission time interval comprising of more than two OFDM symbols and a power level of said reference signal is divided into said non-consecutive OFDM symbols in said transmission time interval, wherein a first portion of a plurality of pilot symbols of at least one OFDM symbol is near a beginning of the transmission time interval and a second portion of said plurality of pilot symbols of at least one other OFDM symbol is near a middle of said transmission time interval, wherein a power level of said plurality of pilot symbols has been divided into said two OFDM symbols in said transmission time interval, said apparatus comprising: a receiver adapted to using the first of the two OFDM symbols carrying reference signals in a succeeding transmission time interval in addition to the reference signals in a current transmission time interval and a preceding transmission time interval. 
 
     
     
       3. The apparatus of  claim 2 , wherein said input signal and plurality of data symbols are comprised of sub-sets, each sub-set intended for a unique receiver. 
     
     
       4. An apparatus using comprising: a processor using information for channel estimation in an orthogonal frequency division multiplexing OFDM system, said information in the form of a pilot structure with a transmission time interval of seven OFDM symbols, said pilot structure comprising a plurality of pilot signals from at least two transmitting antennas, the pilot structure from one transmitting antenna located in a first OFDM symbol and fifth OFDM symbol of said transmission time interval, said apparatus comprising: at least two transmit antennas and wherein said plurality of pilot signals from any antenna are located in said first OFDM symbol and said fifth OFDM symbol or a second OFDM symbol and a sixth OFDM symbol of said transmission time interval. 
     
     
       5. A method for receiving a pilot structure in an orthogonal frequency division multiplexing (OFDM) communication system having a transmitter having a plurality of antennas, said method comprising:
 receiving a frame composed with a time domain and a frequency domain, wherein said frame has a transmission time interval in the time domain and occupies a bandwidth in said frequency domain, said transmission time interval comprising of more than two orthogonal frequency division multiplexing symbols, wherein said transmission time interval comprises of seven orthogonal frequency division multiplexing symbols; and 
 receiving a pilot signal, having pilot power level, from a said plurality of transmitting antenna antennas into two orthogonal frequency division multiplexing symbols of said frame, wherein a plurality of pilot signals from all transmitting antennas have a plurality of same locations in said time domain and wherein at least one pilot signal from at least one transmitting antenna a first antenna of said plurality of transmitting antennas has been located in a first OFDM symbol and a fifth OFDM symbol of said transmission time interval and said power level of said pilot signal has been divided into said a first OFDM symbol and a fifth OFDM symbol in said transmission time interval, wherein said transmitter has at least two antennas and a pilot signal from a second antenna of said plurality of transmitting antennas has been located in said first and fifth orthogonal frequency division multiplexing symbols of said frame such that said pilot power of said pilot signal from said second antenna is in said first and said fifth orthogonal frequency division multiplexing symbols of said transmission time interval. 
 
     
     
       6. A method for receiving a pilot structure in an orthogonal frequency division multiplexing (OFDM) communication system having a transmitter having at least two antennas, said method comprising:
 receiving a frame composed with a time domain and a frequency domain, wherein said frame has a transmission time interval in the time domain and occupies a bandwidth in said frequency domain, said transmission time interval comprising of more than two orthogonal frequency division multiplexing symbols, wherein said transmission time interval comprises of seven orthogonal frequency division multiplexing symbols; and 
 receiving a pilot signal, having a pilot power level, from a plurality of transmitting antenna into two orthogonal frequency division multiplexing symbols of said frame, wherein a plurality of pilot signals from all transmitting antennas have a plurality of same locations in said time domain and wherein at least one pilot signal from at least one transmitting antenna has been located in a first OFDM symbol and a fifth OFDM symbol of said transmission time interval and said power level of said pilot signal has been divided into said a first OFDM symbol and a fifth OFDM symbol in said transmission time interval, wherein a pilot signal from a second antenna has been located in a second and sixth orthogonal frequency division multiplexing symbols of said frame such that said pilot power of said pilot signal from said second antenna is in said second and said sixth orthogonal frequency division multiplexing symbols of the transmission time interval. 
 
     
     
       7. A method for receiving a pilot structure in an orthogonal frequency division multiplexing (OFDM) communication system having a transmitter having at least four antennas, said method comprising:
 receiving a frame composed with a time domain and a frequency domain, wherein said frame has a transmission time interval in the time domain and occupies a bandwidth in said frequency domain, said transmission time interval comprising of more than two orthogonal frequency division multiplexing symbols, wherein said transmission time interval comprises of seven orthogonal frequency division multiplexing symbols; and 
 receiving a pilot signal, having pilot power level, from a plurality of transmitting antenna into two orthogonal frequency division multiplexing symbols of said frame, wherein a plurality of pilot signals from all transmitting antennas have a plurality of same locations in said time domain, wherein a pilot signal from a third antenna has been located in a second and sixth orthogonal frequency division multiplexing symbols of said frame such that the pilot power of the pilot signal from said third antenna is in a second orthogonal frequency division multiplexing symbol and a sixth orthogonal frequency division multiplexing symbols of the transmission time interval; and further wherein said pilot signal from a fourth antenna has been located in a first orthogonal frequency division multiplexing symbol and a fifth orthogonal frequency division multiplexing symbols of said frame such that the pilot power of the pilot signal from the fourth antenna is in the first and fifth orthogonal frequency division multiplexing symbols of the transmission time interval. 
 
     
     
       8. A method for receiving a pilot structure in an orthogonal frequency division multiplexing (OFDM) communication system having a transmitter having at least four antennas, said method comprising:
 receiving a frame composed with a time domain and a frequency domain, wherein said frame has a transmission time interval in the time domain and occupies a bandwidth in said frequency domain, said transmission time interval comprising of more than two orthogonal frequency division multiplexing symbols, wherein said transmission time interval comprises of seven orthogonal frequency division multiplexing symbols; and 
 receiving a pilot signal, having pilot power level, from a plurality of transmitting antenna into two orthogonal frequency division multiplexing symbols of said frame, wherein a plurality of pilot signals from all transmitting antennas have a plurality of same locations in said time domain, wherein a pilot signal from a third antenna has been located in a first orthogonal frequency division multiplexing symbol and a fifth orthogonal frequency division multiplexing symbol of said frame such that the pilot power of the pilot signal from said third antenna is in said first and fifth orthogonal frequency division multiplexing symbols of the transmission time interval; and a pilot signal from a fourth antenna is located in a second orthogonal frequency division multiplexing symbol and a sixth orthogonal frequency division multiplexing symbols of said frame such that said pilot power of said pilot signal from said fourth antenna is in said second and sixth orthogonal frequency division multiplexing symbols of said transmission time interval. 
 
     
     
       9. A method for receiving a pilot structure in an orthogonal frequency division multiplexing (OFDM) communication system having a transmitter having at least four antennas, said method comprising:
 receiving a frame composed with a time domain and a frequency domain, wherein said frame has a transmission time interval in the time domain and occupies a bandwidth in said frequency domain, said transmission time interval comprising of more than two orthogonal frequency division multiplexing symbols, wherein said transmission time interval comprises of seven orthogonal frequency division multiplexing symbols; and 
 receiving a pilot signal, having pilot power level, from a plurality of transmitting antenna into two orthogonal frequency division multiplexing symbols of said frame, wherein a plurality of pilot signals from all transmitting antennas have a plurality of same locations in said time domain and wherein at least one pilot signal from at least one antenna has been located in a first OFDM symbol and a fifth OFDM symbol of said transmission time interval and said power level of said pilot signal has been divided into a first OFDM symbol and a fifth OFDM symbol in said transmission time interval, wherein a frequency location of a pilot signal from a third antenna is the same as the frequency location of a pilot signal from a first antenna and a frequency location of a pilot signal from a fourth antenna is the same as a frequency location of the pilot from a second antenna. 
 
     
     
       10. A method for receiving a pilot structure in an orthogonal frequency division multiplexing (OFDM) communication system having a transmitter having a plurality of antennas, the method comprising:
 receiving a frame composed with a time domain and a frequency domain, wherein the frame has a transmission time interval in the time domain and occupies a bandwidth in the frequency domain, wherein the transmission time interval comprises seven OFDM symbols; and   receiving a reference signal, from said plurality of transmitting antennas wherein the reference signal includes first antenna reference symbols from at least a first antenna of said plurality of transmitting antennas, the first antenna reference symbol located in a first OFDM symbol being at a first frequency, and the first antenna reference symbol located in a fifth OFDM symbol of the transmission time interval being at a second frequency;   wherein the reference signal includes second antenna reference symbols from a second antenna of said plurality of transmitting antennas, the second antenna reference symbol located in the first OFDM symbol being at the second frequency, and the second antenna reference symbol located in the fifth OFDM symbol of the transmission time interval being at the first frequency; and   using at least one of the received symbols to perform a channel estimate.   
     
     
       11. The method of claim 10, wherein the transmission time interval has a 0.5 millisecond duration. 
     
     
       12. The method of claim 10, further comprising providing Channel Quality Indication (CQI) feedback. 
     
     
       13. The method of claim 10, wherein each symbol of the reference signal at the first frequency also occurs at a third frequency and each symbol of the reference signal at the second frequency also occurs at a fourth frequency. 
     
     
       14. The method of claim 13, further comprising providing Channel Quality Indication (CQI) feedback. 
     
     
       15. The method of claim 10, wherein the reference signal further includes a third antenna reference symbol from a third antenna, the third antenna reference symbol located in a second OFDM symbol of the transmission time interval and being at the first frequency; and the reference signal further includes a fourth antenna reference symbol from a fourth antenna, the fourth antenna reference symbol located in a second OFDM symbol of the transmission time interval and being at the second frequency. 
     
     
       16. The method of claim 15, further comprising providing Channel Quality Indication (CQI) feedback. 
     
     
       17. The method of claim 15, wherein each symbol of the reference signal at the first frequency also occurs at a third frequency and each symbol of the reference signal at the second frequency also occurs at a fourth frequency. 
     
     
       18. The method of claim 17, further comprising providing Channel Quality Indication (CQI) feedback.