Pilot Symbol Patterns for Transmission through a Plurality of Antennas

Abstract

A method and apparatus for improving channel estimation within an OFDM communication system. Channel estimation in OFDM is usually performed with the aid of pilot symbols. The pilot symbols are typically spaced in time and frequency. The set of frequencies and times at which pilot symbols are inserted is referred to as a pilot pattern. In some cases, the pilot pattern is a diagonal-shaped lattice, either regular or irregular. The method first interpolates in the direction of larger coherence (time or frequency). Using these measurements, the density of pilot symbols in the direction of faster change will be increased thereby improving channel estimation without increasing overhead. As such, the results of the first interpolating step can then be used to assist the interpolation in the dimension of smaller coherence (time or frequency).

What is claimed is: 
     
         1 . A base station comprising:
 a plurality of transmit antennas;   digital circuitry, wherein the digital circuitry is configured to:
 transmit, via the plurality of transmit antennas, a data traffic transmission on a downlink time frequency resource to a user equipment device, wherein the time frequency resource includes a plurality of orthogonal frequency division multiplexing (OFDM) symbol durations in time and a plurality of subcarriers in frequency; 
 transmit, via the plurality of transmit antennas, a first set of time division multiplexed (TDM) pilots in an initial OFDM symbol of the time frequency resource; and 
 transmit, via the plurality of transmit antennas, a second set of TDM pilots in a second OFDM symbol of the time frequency resource, wherein the second OFDM symbol is 7 OFDM symbols after the initial OFDM symbol. 
   
     
     
         2 . The base station of  claim 1 ,
 wherein the initial OFDM symbol and the second OFDM symbol are not utilized to transmit data traffic.   
     
     
         3 . The base station of  claim 1 ,
 wherein the digital circuitry is further configured to interleave TDM pilots from different antennas on each of the initial OFDM symbol and the second OFDM symbol.   
     
     
         4 . The base station of  claim 1 ,
 wherein the initial OFDM symbol of the time frequency resource is a first symbol of a slot.   
     
     
         5 . The base station of  claim 1 ,
 wherein the first set of TDM pilots and the second set of TDM pilots are used in a beamforming zone.   
     
     
         6 . The base station of  claim 1 , wherein each intervening subcarrier between the initial OFDM symbol and the second OFDM symbol carries one or both of control information and data information. 
     
     
         7 . A base station comprising:
 a plurality of transmit antennas;   digital circuitry, wherein the digital circuitry is configured to:
 transmit, via the plurality of transmit antennas, a data traffic transmission on a downlink time frequency resource to a user equipment device, wherein time frequency resource includes a plurality of orthogonal frequency division multiplexing (OFDM) symbol durations in time and a plurality of subcarriers in frequency; 
 transmit, via the plurality of transmit antennas, a first set of time division multiplexed (TDM) pilots in an initial OFDM symbol of the time frequency resource, wherein the first set of TDM pilots are used for demodulation of the data traffic, and wherein no pilots in the time frequency resource other than the first set of TDM pilots are used for demodulation of the data traffic. 
   
     
     
         8 . The base station of  claim 7 ,
 wherein the initial OFDM symbol is not utilized to transmit data traffic.   
     
     
         9 . The base station of  claim 7 ,
 wherein the digital circuitry is further configured to interleave TDM pilots from different antennas on the initial OFDM symbol.   
     
     
         10 . The base station of  claim 7 ,
 wherein the initial OFDM symbol of the time frequency resource is a first symbol of a slot.   
     
     
         11 . The base station of  claim 7 ,
 wherein the first set of TDM pilots is used in a beamforming zone.   
     
     
         12 . A user equipment device (UE) comprising:
 one or more receive antennas; and   a processor, wherein the processor is configured to receive transmissions via the one or more receive antennas, wherein the UE is configured to:
 receive, via the one or more of receive antennas, a data traffic transmission on a downlink time frequency resource to a user equipment device, wherein the time frequency resource includes a plurality of orthogonal frequency division multiplexing (OFDM) symbol durations in time and a plurality of subcarriers in frequency; 
 receive, via the one or more of receive antennas, a first set of time division multiplexed (TDM) pilots in an initial OFDM symbol of the time frequency resource; and 
 receive, via the one or more receive antennas, a second set of TDM pilots in a second OFDM symbol of the time frequency resource, wherein the second OFDM symbol is 7 OFDM symbols after the initial OFDM symbol. 
   
     
     
         13 . The UE of  claim 12 ,
 wherein the initial OFDM symbol and the second OFDM symbol are not utilized to receive data traffic.   
     
     
         14 . The UE of  claim 12 ,
 wherein the initial OFDM symbol of the time frequency resource is a first symbol of a slot.   
     
     
         15 . The UE of  claim 12 ,
 wherein the first set of TDM pilots and the second set of TDM pilots are used in a beamforming zone.   
     
     
         16 . The UE of  claim 12 , wherein each intervening subcarrier between the initial OFDM symbol and the second OFDM symbol carries one or both of control information and data information. 
     
     
         17 . The UE of  claim 12 , wherein the UE is further configured to:
 measure attenuation of the first and second sets of time division multiplexed (TDM) pilots and estimate the attenuations of data symbols in between the first and second sets of time division multiplexed (TDM) pilots.