Channel estimation for an OFDM communication system with inactive subbands

An apparatus in a wireless communication system for efficiently estimating a frequency response of a wireless channel in a wireless OFDM communication system in which only M subbands centered among N total subbands are used for data/pilot transmission with N−M subbands at either end comprising inactive subbands, comprising:

• a demodulator operative to provide received symbols;
• and
• a processor operative to obtain an initial frequency response estimate for subbands in a first set of uniformly spaced apart by N/P subbands based on channel gain estimates for a second set of subbands within the centered M subbands derived from the received symbols, where P is an integer greater than one and N is total subbands, wherein the first set includes at least one subband not included in the second set,
• derive a time-domain channel impulse response estimate for the wireless channel based on the initial frequency response estimate, and
• derive a final frequency response estimate for the wireless channel based on the channel impulse response estimate.

A method of efficiently estimating a frequency response of a wireless channel in a wireless OFDM communication system in which only M subbands centered among N total subbands are used for data/pilot transmission with N−M subbands at either end comprising inactive subbands, comprising:

• a) obtaining an initial frequency response estimate for subbands in a first set of uniformly spaced apart by N/P subbands based on channel gain estimates for a second set of subbands within the centered M subbands, where P is an integer greater than one and N is total subbands, and wherein the first set includes at least one subband not included in the second set;
• b) deriving a time-domain channel impulse response estimate for the wireless channel based on the initial frequency response estimate;
• c) filtering the channel impulse response estimate over a plurality of symbol periods;
• and
• d) deriving a final frequency response estimate for the wireless channel based on the filtered channel impulse response estimate.

A method of efficiently estimating a frequency response of a wireless channel in an orthogonal frequency division multiplexing (OFDM) communication system in which only M subbands centered among N total subbands are used for data/pilot transmission with N−M subbands at either end comprising inactive subbands, the method comprising:

• obtaining an initial frequency response estimate for subbands in a first set of uniformly spaced apart by N/P subbands based on channel gain estimates derived from pilot symbols received on a second set of subbands within the centered M subbands, where P is an integer greater than one and N is total subbands, and wherein the first set includes at least one subband not included in the second set;
• performing a P-point inverse fast Fourier transform (IFFT) on the initial frequency response estimate to obtain a time-domain channel impulse response estimate;
• zero padding the channel impulse response estimate to length N, where N is an integer greater than P and is a power of two;
• and
• performing an N-point fast Fourier transform (FFT) on the zero-padded channel impulse response estimate to obtain a final frequency response estimate for the wireless channel.

A processor readable memory for storing instructions operable to:

• efficiently derive an initial frequency response estimate of a wireless channel in a wireless OFDM communication system, in which only M subbands centered among N total subbands are used for data/pilot transmission with N−M subbands at either end comprising inactive subbands for a first set of uniformly spaced apart by N/P subbands in an orthogonal frequency division multiplexing (OFDM) communication system based on channel gain estimates for a second set of subbands within the centered M subbands, where P is an integer greater than one and N is total subbands, and wherein the first set includes at least one subband not included in the second set;
• perform a P-point inverse fast Fourier transform (IFFT) on the initial frequency response estimate to obtain a time-domain channel impulse response estimate;
• zero pad the channel impulse response estimate to length N, where N is an integer greater than P and is a power of two;
• and perform an N-point fast Fourier transform (FFT) on the zero-padded channel impulse response estimate to obtain a final frequency response estimate for a wireless channel in the system.

A non-transitory computer readable medium having computer executable instructions stored thereon, which when executed by a machine cause the machine to perform operations comprising:

• (a) obtaining an initial frequency response estimate for subbands in a first set of uniformly spaced apart by N/P subbands based on channel gain estimates for a second set of subbands within the centered M subbands, where P is an integer greater than one and N is total subbands, and wherein the first set includes at least one subband not included in the second set;
• (b) deriving a time-domain channel impulse response estimate for the wireless channel based on the initial frequency response estimate;
• and
• (c) deriving a final frequency response estimate for the wireless channel based on the channel impulse response estimate.