Methods and systems for choosing cyclic delays in multiple antenna OFDM systems
AssigneeQUALCOMM Incorporated
InventorsPranav Dayal, Ayman Fawzy Naguib
Life of this patent
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Abstract
Certain embodiments of the present disclosure relate to a method to determine appropriate values of cyclic delays applied at a transmitter with multiple antennas in order to provide accurate estimation of channel gains in a multiple-input single-output (MISO) system or multiple-input multiple-output (MIMO) system.
Claims74
A method of transmitting pilots in a wireless communication system, comprising:
- generating a first pilot for a first transmit antenna based on a first cyclic delay;
- and
- generating a second pilot for a second transmit antenna based on a second cyclic delay larger than the first cyclic delay by at least a cyclic prefix length,
- wherein generating the first pilot and the second pilot comprises generating OFDM symbols that comprise pilot symbols mapped to subcarriers spaced apart by p, where p is a prime number that does not divide NFFT, and NFFT is an FFT size for the generated OFDM symbols.
A method of performing channel estimation in a wireless communication system, comprising:
- obtaining first input samples comprising first and second pilots, the first pilot being generated based on a first cyclic delay and sent from a first transmit antenna, the second pilot being generated based on a second cyclic delay and sent from a second transmit antenna, the second cyclic delay being larger than the first cyclic delay by at least a cyclic prefix length, and the first input samples being from a first receive antenna;
- and
- processing the first input samples based on pilot subcarriers spaced apart by p to obtain a first channel estimate for the first transmit antenna and a second channel estimate for the second transmit antenna, where p is a prime number that does not divide NFFT, and NFFT is an FFT size for an OFDM symbol.
An apparatus for transmitting pilots in a wireless communication system, comprising:
- logic for generating a first pilot for a first transmit antenna based on a first cyclic delay;
- and
- logic for generating a second pilot for a second transmit antenna based on a second cyclic delay larger than the first cyclic delay by at least a cyclic prefix length,
- wherein the logic for generating the first pilot and the logic for generating the second pilot comprise logic for generating OFDM symbols that comprise pilot symbols mapped to subcarriers spaced apart by p, where p is a prime number that does not divide NFFT, and NFFT is an FFT size for the generated OFDM symbols.
An apparatus for performing channel estimation in a wireless communication system, comprising:
- logic for obtaining first input samples comprising first and second pilots, the first pilot being generated based on a first cyclic delay and sent from a first transmit antenna, the second pilot being generated based on a second cyclic delay and sent from a second transmit antenna, the second cyclic delay being larger than the first cyclic delay by at least a cyclic prefix length, and the first input samples being from a first receive antenna;
- and
- logic for processing the first input samples based on pilot subcarriers spaced apart by p to obtain a first channel estimate for the first transmit antenna and a second channel estimate for the second transmit antenna, where p is a prime number that does not divide NFFT, and NFFT is an FFT size for an OFDM symbol.
An apparatus for transmitting pilots in a wireless communication system, comprising:
- means for generating a first pilot for a first transmit antenna based on a first cyclic delay;
- and
- means for generating a second pilot for a second transmit antenna based on a second cyclic delay larger than the first cyclic delay by at least a cyclic prefix length,
- wherein the means for generating the first pilot and the means for generating the second pilot comprise means for generating OFDM symbols that comprise pilot symbols mapped to subcarriers spaced apart by p, where p is a prime number that does not divide NFFT, and NFFT is an FFT size for the generated OFDM symbols.
An apparatus for performing channel estimation in a wireless communication system, comprising:
- means for obtaining first input samples comprising first and second pilots, the first pilot being generated based on a first cyclic delay and sent from a first transmit antenna, the second pilot being generated based on a second cyclic delay and sent from a second transmit antenna, the second cyclic delay being larger than the first cyclic delay by at least a cyclic prefix length, and the first input samples being from a first receive antenna;
- and
- means for processing the first input samples based on pilot subcarriers spaced apart by p to obtain a first channel estimate for the first transmit antenna and a second channel estimate for the second transmit antenna, where p is a prime number that does not divide NFFT, and NFFT is an FFT size for an OFDM symbol.
A computer-program product for transmitting pilots in a wireless communication system, comprising a non-transitory computer readable medium having instructions stored thereon, the instructions being executable by one or more processors and the instructions comprising:
- instructions for generating a first pilot for a first transmit antenna based on a first cyclic delay;
- and
- instructions for generating a second pilot for a second transmit antenna based on a second cyclic delay larger than the first cyclic delay by at least a cyclic prefix length,
- wherein the instructions for generating the first pilot and the instructions for generating the second pilot comprise instructions for generating OFDM symbols that comprise pilot symbols mapped to subcarriers spaced apart by p, where p is a prime number that does not divide NFFT, and NFFT is an FFT size for the generated OFDM symbols.
A computer-program product for performing channel estimation in a wireless communication system, comprising a non-transitory computer readable medium having instructions stored thereon, the instructions being executable by one or more processors and the instructions comprising:
- instructions for obtaining first input samples comprising first and second pilots, the first pilot being generated based on a first cyclic delay and sent from a first transmit antenna, the second pilot being generated based on a second cyclic delay and sent from a second transmit antenna, the second cyclic delay being larger than the first cyclic delay by at least a cyclic prefix length, and the first input samples being from a first receive antenna;
- and
- instructions for processing the first input samples based on pilot subcarriers spaced apart by p to obtain a first channel estimate for the first transmit antenna and a second channel estimate for the second transmit antenna, where p is a prime number that does not divide NFFT, and NFFT is an FFT size for an OFDM symbol.
Dependencies are inferred from the claim text.