Pilot transmission schemes for a multi-antenna system

An apparatus in a wireless multi-antenna communication system, comprising:

• a pilot processor operative to
• generate a first set of T scaled pilot symbols with a first vector of T coefficients, where T is an integer greater than one, and wherein the first set of scaled pilot symbols is suitable for use for channel estimation by receivers with a single antenna, and
• selectively generate at least T−1 additional sets of T scaled pilot symbols with at least T−1 additional vectors if at least one receiver with multiple antennas is to be supported by the system, each additional vector including T coefficients, wherein the first and at least T−1 additional vectors are different vectors in a matrix, and wherein the first and at least T−1 additional sets of scaled pilot symbols are suitable for use for channel estimation by the at least one receiver with multiple antennas;
• and
• a plurality of transmitter units operative to condition and transmit each set of T scaled pilot symbols via T transmit antennas, one scaled pilot symbol on each transmit antenna.

An apparatus in a wireless multi-antenna communication system, comprising:

• means for generating a first set of T scaled pilot symbols with a first vector of T coefficients, where T is an integer greater than one, and wherein the first set of scaled pilot symbols is suitable for use for channel estimation by receivers with a single antenna;
• means for selectively generating at least T−1 additional sets of T scaled pilot symbols with at least T−1 additional vectors if at least one receiver with multiple antennas is to be supported by the system, each additional vector including T coefficients, wherein the first and at least T−1 additional vectors are different vectors in a matrix, and wherein the first and at least T−1 additional sets of scaled pilot symbols are suitable for use for channel estimation by the at least one receiver with multiple antennas;
• and
• means for transmitting each set of T scaled pilot symbols via T transmit antennas, one scaled pilot symbol on each transmit antenna.

In a wireless multi-antenna communication system utilizing orthogonal frequency division multiplexing (OFDM), a method of performing channel estimation at a receiver, comprising:

• obtaining, via R receive antennas, R times M sets of P received pilot symbols for T times M sets of P scaled pilot symbols generated with T times M coefficients in a T by M matrix, where R, T and P are integers greater than one, M is an integer equal to or greater than T, M groups of R sets are formed for the R times M sets, and M groups of T sets are formed for the T times M sets, wherein one coefficient in the T by M matrix is used to generate each set of P scaled pilot symbols, and wherein each group of T sets of P scaled pilot symbols is transmitted from T transmit antennas on P subbands;
• deriving an initial frequency-domain frequency response estimate for each set of P received pilot symbols, wherein R times M initial frequency response estimates are derived for the R times M sets of P received pilot symbols;
• deriving an initial time-domain impulse response estimate for each initial frequency response estimate, wherein R times M initial impulse response estimates are derived for the R times M initial frequency response estimates;
• deriving R times T final time-domain impulse response estimates based on the R times M initial impulse response estimates and the T by M matrix;
• and
• deriving a final frequency-domain frequency response estimate for each final impulse response estimate, wherein R times T final frequency response estimates are derived for the R times T final impulse response estimates and represent an estimate of a multiple-input multiple-output (MIMO) channel between the T transmit antennas and the R receive antennas.

An apparatus in a wireless multi-antenna communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

• a plurality of receiver units operative to obtain, via R receive antennas, R times M sets of P received pilot symbols for T times M sets of P scaled pilot symbols generated with T times M coefficients in a T by M matrix, where R, T and P are integers greater than one, M is an integer equal to or greater than T, M groups of R sets are formed for the R times M sets, and M groups of T sets are formed for the T times M sets, wherein one coefficient in the T by M matrix is used to generate each set of P scaled pilot symbols, and wherein each group of T sets of P scaled pilot symbols is transmitted from T transmit antennas on P subbands;
• and
• a channel estimator operative to
• derive an initial frequency-domain frequency response estimate for each set of P received pilot symbols, wherein R times M initial frequency response estimates are derived for the R times M sets of P received pilot symbols,
• derive an initial time-domain impulse response estimate for each initial frequency response estimate, wherein R times M initial impulse response estimates are derived for the R times M initial frequency response estimates,
• derive R times T final time-domain impulse response estimates based on the R times M initial impulse response estimates and the T by M matrix, and
• derive a final frequency-domain frequency response estimate for each final impulse response estimate, wherein R times T final frequency response estimates are derived for the R times T final impulse response estimates and represent an estimate of a multiple-input multiple-output (MIMO) channel between the T transmit antennas and the R receive antennas.

An apparatus in a wireless multi-antenna communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

• means for obtaining, via R receive antennas, R times M sets of P received pilot symbols for T times M sets of P scaled pilot symbols generated with T times M coefficients in a T by M matrix, where R, T and P are integers greater than one, M is an integer equal to or greater than T, M groups of R sets are formed for the R times M sets, and M groups of T sets are formed for the T times M sets, wherein one coefficient in the T by M matrix is used to generate each set of P scaled pilot symbols, and wherein each group of T sets of P scaled pilot symbols is transmitted from T transmit antennas on P subbands;
• means for deriving an initial frequency-domain frequency response estimate for each set of P received pilot symbols, wherein R times M initial frequency response estimates are derived for the R times M sets of P received pilot symbols;
• means for deriving an initial time-domain impulse response estimate for each initial frequency response estimate, wherein R times M initial impulse response estimates are derived for the R times M initial frequency response estimates;
• means for deriving R times T final time-domain impulse response estimates based on the R times M initial impulse response estimates and the T by M matrix;
• and
• means for deriving a final frequency-domain frequency response estimate for each final impulse response estimate, wherein R times T final frequency response estimates are derived for the R times T final impulse response estimates and represent an estimate of a multiple-input multiple-output (MIMO) channel between the T transmit antennas and the R receive antennas.