Channel estimation for OFDM communication systems
First Claim
1. A method for estimating a frequency response of a wireless channel, comprisingobtaining an initial estimate of the frequency response of the wireless channel for a first group of subbands;
- and deriving an enhanced estimate of the frequency response of the wireless channel for a second group of subbands based on the initial frequency response estimate, wherein the enhanced frequency response estimate is derived based on an estimate of an impulse response of the wireless channel that is implicitly or explicitly derived based on the initial frequency response estimate.
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Abstract
Techniques to estimate the frequency response of a wireless channel in an OFDM system. In one method, an initial estimate of the frequency response of the wireless channel is obtained for a first group of subbands based on a pilot transmission received via the subbands in the first group. An estimate of the impulse response of the wireless channel is then derived based on the initial frequency response estimate. An enhanced estimate of the frequency response of the wireless channel is then derived for a second group of subbands based on the impulse response estimate. The first and second groups may each include all or only a subset of the usable subbands. Subband multiplexing may be used to allow simultaneous pilot transmissions by multiple terminals on their associated groups of subbands.
171 Citations
27 Claims
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1. A method for estimating a frequency response of a wireless channel, comprising
obtaining an initial estimate of the frequency response of the wireless channel for a first group of subbands; - and
deriving an enhanced estimate of the frequency response of the wireless channel for a second group of subbands based on the initial frequency response estimate, wherein the enhanced frequency response estimate is derived based on an estimate of an impulse response of the wireless channel that is implicitly or explicitly derived based on the initial frequency response estimate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for estimating a frequency response of a wireless channel in an orthogonal frequency division multiplexing (OFDM) communication system, comprising
obtaining an initial estimate of the frequency response of the wireless channel for a first group of subbands based on a pilot transmission received via the subbands in the first group, wherein the first group of subbands is a subset of all subbands usable for data transmission; - and
deriving an enhanced estimate of the frequency response of the wireless channel for the usable subbands based on the initial frequency response estimate, wherein the enhanced frequency response estimate is derived based on an estimate of an impulse response of the wireless channel that is implicitly or explicitly derived based on the initial frequency response estimate, and wherein the enhanced frequency response estimate is further derived based on a first discrete Fourier transform (DFT) matrix for the subbands in the first group and a second DFT matrix for the usable subbands.
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19. A method for estimating a frequency response of a wireless channel for each of a plurality of terminals in a wireless communication system, comprising
obtaining an initial estimate of the frequency response of the wireless channel for each of the plurality of terminals, wherein each of the plurality of terminal is associated with a respective one of a plurality of disjoint groups of subbands, and wherein the initial frequency response estimate for each terminal is obtained for the associated group of subbands based on a pilot transmission received via the subbands in the associated group; - and
deriving an enhanced estimate of the frequency response of the wireless channel for each of the plurality of terminals based on the initial frequency response estimate for the terminal, wherein the enhanced frequency response estimate for each terminal covers a particular set of subbands and is derived based on an estimate of an impulse response of the wireless channel for the terminal that is implicitly or explicitly derived based on the initial frequency response estimate for the terminal. - View Dependent Claims (20)
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21. An apparatus operable to estimate a frequency response of a wireless channel, comprising
means for obtaining an initial estimate of the frequency response of the wireless channel for a first group of subbands; - and
means for deriving an enhanced estimate of the frequency response of the wireless channel for a second group of subbands based on the impulse response estimate, wherein the enhanced frequency response estimate is derived based on an estimate of an impulse response of the wireless channel that is implicitly or explicitly derived based on the initial frequency response estimate. - View Dependent Claims (22, 23)
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24. An access point in a wireless communication system, comprising:
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a demodulator operative to receive pilot transmission from one or more terminals, wherein a plurality of disjoint groups of subbands are formed from a plurality of usable subbands, and wherein each of the one or more terminals transmits a pilot on a specific group of subbands that is selected from the plurality of disjoint groups of subbands and assigned to the terminal; and
a controller operative to obtain an initial estimate of a frequency response of an uplink channel for each of the one or more terminals, wherein the initial frequency response estimate for each terminal covers the group of subbands assigned to the terminal and is obtained based on the pilot transmission received from the terminal, and derive an enhanced estimate of the frequency response of the uplink channel for each of the one or more terminals based on the initial frequency response estimate for the terminal, wherein the enhanced frequency response estimate for each terminal is derived based on an estimate of an impulse response of the wireless channel for the terminal that is implicitly or explicitly derived based on the initial frequency response estimate for the terminal. - View Dependent Claims (25)
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26. A terminal in a wireless communication system, comprising:
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a demodulator operative to receive a pilot transmission on a first group of subbands; and
a controller operative to obtain an initial estimate of a frequency response of a downlink channel for the first group of subbands based on the pilot transmission received via the subbands in the first group, and derive an enhanced estimate of the frequency response of the downlink channel for a second group of subbands based on the initial frequency response estimate, wherein the enhanced frequency response estimate is derived based on an estimate of an impulse response of the wireless channel that is implicitly or explicitly derived based on the initial frequency response estimate. - View Dependent Claims (27)
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Specification