Wireless channel measurement noise removing method
Methods and apparatuses for noise removal are provided. A noise removal method may determine multiple channel impulse responses (CIRs) and multiple power delay profiles (PDPs) corresponding to the CIRs collected at multiple spatial-separated positions. Initially, the noise removal method may apply a dynamic noise threshold based on a false-alarm probability to generate an initial denoised signal. Thereafter, the noise removal method may apply a delay window to the initial denoised signal to generate an intermediate denoised signal. Finally, the noise removal method may perform a persistence check on the intermediate denoised signal to generate the final denoised signals, assuming a multiple component present in multiple CIRs when the transmitter or receiver moves in a small distance which is not true for the random noise. The false alarm probability, the delay window, and/or the persistence check may be dynamically optimized for a specific environment.
1 . An apparatus, comprising:
a memory;
a transceiver comprising:
at least one antenna configured to:
receive a signal at a plurality of positions; and
a processor, wherein the transceiver and the processor are configured to:
determine a plurality of channel impulse responses (CIRs) for the received signal at the plurality of positions,
determine a plurality of power delay profiles (PDPs) for the plurality of CIRs,
apply a dynamic noise threshold to the plurality of PDPs to generate a first set of denoised PDPs,
identify a first set of multi-path components (MPCs) in the first set of denoised PDPs,
apply at least one delay gate around one or more MPCs of the first set of MPCs to generate a second set of denoised PDPs,
identify one or more persistent MPCs from the second set of denoised PDPs, and
filter the second set of denoised PDPs based on the one or more persistent MPCs to generate at least one denoised signal.
2 . The apparatus of claim 1 , wherein the processor is further configured to:
determine a false alarm probability associated with the received signal at the plurality of positions, and
determine the dynamic noise threshold based on the false alarm probability.
3 . The apparatus of claim 2 , wherein applying the dynamic noise threshold comprises:
determining a plurality of power levels of a plurality of CIR samples in each PDP of the plurality of PDPs,
comparing the plurality of power levels with the dynamic noise threshold, and
removing one or more CIR samples of the plurality of CIR samples having one or more power levels lesser than the dynamic noise threshold.
4 . The apparatus of claim 3 , wherein the false alarm probability is a predetermined percentile within a noise distribution of the plurality of CIR samples.
5 . The apparatus of claim 1 , wherein applying the at least one delay gate comprises:
identifying a strongest MPC in each PDP of the first set of denoised PDPs,
centering, around the strongest MPC, a delay bin comprising a first delay gate before the strongest MPC and a second delay gate after the strongest MPC, and
removing one or more CIR samples from the first set of denoised PDPs falling outside the delay bin.
6 . The apparatus of claim 5 , wherein identifying the one or more persistent MPCs comprises:
determining that the one or more persistent MPCs are observed in a predetermined number of PDPs associated with a predetermined number of contiguous positions of the plurality of positions.
7 . The apparatus of claim 5 , wherein identifying the one or more persistent MPCs comprises:
determining that the one or more persistent MPCs are observed at a predetermined number of contiguous delay bins associated with a predetermined number of contiguous positions.
8 . The apparatus of claim 1 , wherein the apparatus is a channel sounding apparatus.
9 . The apparatus of claim 1 , wherein the at least one antenna is an antenna rotated through the plurality of positions along at least one of: a circumference of a circle, a line, or a curve.
10 . The apparatus of claim 1 , wherein the at least one antenna is at least one of: an antenna array or a virtual circular array.
11 . A method, comprising:
receiving a signal by at least one antenna at a plurality of positions;
determining a plurality of channel impulse responses (CIRs) for the received signal at the plurality of positions;
determining a plurality of power delay profiles (PDPs) for the plurality of CIRs;
applying a dynamic noise threshold to the plurality of PDPs for generating a first set of denoised PDPs;
identifying a first set of multi-path components (MPCs) in the first set of denoised PDPs;
applying at least one delay gate around one or more MPCs of the first set of MPCs to generate a second set of denoised PDPs;
identifying one or more persistent MPCs from the second set of denoised PDPs; and
filtering the second set of denoised PDPs based on the one or more persistent MPCs for generating at least one denoised signal.
12 . The method of claim 11 , the method further comprising:
determining a false alarm probability associated with the received signal at the plurality of positions; and
determining the dynamic noise threshold based on the false alarm probability.
13 . The method of claim 12 , wherein applying the dynamic noise threshold comprises:
determining a plurality of power levels of a plurality of CIR samples in each PDP of the plurality of PDPs;
comparing the plurality of power levels with the dynamic noise threshold; and
removing one or more CIR samples of the plurality of CIR samples having one or more power levels lesser than the dynamic noise threshold.
14 . The method of claim 13 , wherein the false alarm probability is a predetermined percentile within a noise distribution of the plurality of CIR samples.
15 . The method of claim 11 , wherein applying the at least one delay gate comprises:
identifying a strongest MPC in each PDP of the first set of denoised PDPs;
centering, around the strongest MPC, a delay bin comprising a first delay gate before the strongest MPC and a second delay gate after the strongest MPC; and
removing one or more CIR samples from the first set of denoised PDPs falling outside the delay bin.
16 . The method of claim 15 , wherein identifying the one or more persistent MPCs comprises:
determining that the one or more persistent MPCs are observed in a predetermined number of PDPs associated with a predetermined number of contiguous positions of the plurality of positions.
17 . The method of claim 15 , wherein identifying the one or more persistent MPCs comprises:
determining that the one or more persistent MPCs are observed at a predetermined number of contiguous delay bins associated with a predetermined number of contiguous positions.
18 . The method of claim 11 , wherein the method is performed by a channel sounding apparatus.
19 . The method of claim 11 , wherein the at least one antenna is an antenna rotated through the plurality of positions along at least one of: a circumference of a circle, a line, or a curve.
20 . The method of claim 11 , wherein the at least one antenna is at least one of: an antenna array or a virtual circular array.