Scattered pilot pattern and channel estimation method for MIMO-OFDM systems
View Patent ↗Methods and apparatus are provided for inserting data symbols and pilot symbols in an OFDM (orthogonal frequency division multiplexing) transmission resource utilizing frequency hopping patterns for the data symbols and/or the pilot symbols. Data symbols and pilot symbols are allocated for down link (base station to mobile station) and up link (mobile station to bases station) transmission resources in a two-dimensional time-frequency pattern. For each antenna of a MIMO-OFDM (multiple input multiple output OFDM) communication system, pilot symbols are inserted in a scattered pattern in time-frequency and data symbols are inserted in an identical frequency-hopping pattern in time-frequency as that of other antennas.
1. A method, comprising:
for a first transmitting antenna, sparsely distributing pilot symbols in a respective first pattern in time-frequency into an Orthogonal Frequency Division Multiplexing (OFDM) frame, each pilot symbol location of the first pattern in time-frequency corresponding to a null symbol location in time-frequency for a second transmitting antenna;
for a third transmitting antenna, sparsely distributing pilot symbols in a respective second pattern in time-frequency into the OFDM frame, each pilot symbol location of the second pattern in time-frequency corresponding to a null symbol location in time-frequency for a fourth transmitting antenna, wherein a pilot density for the first pattern is higher than a pilot density for the second pattern; and
transmitting the sparsely distributed pilot symbols.
2. The method of claim 1 , wherein the OFDM frame includes a preamble.
3. The method of claim 1 , wherein the OFDM frames includes a time domain and a frequency domain.
4. The method of claim 1 , wherein at least one pattern is offset from a pilot pattern of an adjacent base station.
5. The method of claim 1 , further comprising transmitting the pilot symbols at a higher power level than data symbols.
6. An Orthogonal Frequency Division Multiplexing (OFDM) base station of a wireless network, comprising:
at least two transmitting antennas;
one or more processors configured to:
for a first transmitting antenna, sparsely distribute pilot symbols in a respective first pattern in time-frequency into an Orthogonal Frequency Division Multiplexing (OFDM) frame, each pilot symbol location of the first pattern in time-frequency corresponding to a null symbol location in time-frequency for a second transmitting antenna
for a third transmitting antenna, sparsely distribute pilot symbols in a respective second pattern in time-frequency into the OFDM frame, each pilot symbol location of the second pattern in time-frequency corresponding to a null symbol location in time-frequency for a fourth transmitting antenna, wherein a pilot density for the first pattern is higher than a pilot density for the second pattern; and
a transmitter configured to transmit the sparsely distributed pilot symbols.
7. The OFDM base station of claim 6 , wherein the OFDM frame includes a preamble.
8. The OFDM base station of claim 6 , wherein the OFDM frames includes a time domain and a frequency domain.
9. The OFDM base station of claim 6 , wherein at least one pattern is offset from a pilot pattern of an adjacent base station.
10. The OFDM base station of claim 6 , further configured to transmit the pilot symbols at a higher power level than data symbols.
11. A non-transitory computer readable medium storing instructions to cause a processor to perform operations comprising:
for a first transmitting antenna, sparsely distributing pilot symbols in a respective first pattern in time-frequency into an Orthogonal Frequency Division Multiplexing (OFDM) frame, each pilot symbol location of the first pattern in time-frequency corresponding to a null symbol location in time-frequency for a second transmitting antenna;
for a third transmitting antenna, sparsely distributing pilot symbols in a respective second pattern in time-frequency into the OFDM frame, each pilot symbol location of the second pattern in time-frequency corresponding to a null symbol location in time-frequency for a fourth transmitting antenna, wherein a pilot density for the first pattern is higher than a pilot density for the second pattern; and
transmitting the sparsely distributed pilot symbols.
12. The non-transitory computer readable medium of claim 11 , wherein the OFDM frame includes a preamble.
13. The non-transitory computer readable medium of claim 11 , wherein the OFDM frames includes a time domain and a frequency domain.
14. The non-transitory computer readable medium of claim 11 , wherein at least one pattern is offset from a pilot pattern of an adjacent base station.
15. The non-transitory computer readable medium of claim 11 , further comprising transmitting the pilot symbols at a higher power level than data symbols.