Method of using time domain subspace signals and spatial domain subspace signals for location approximation through orthogonal frequency-division multiplexing
A method for location approximation through time-domain subspace signals and spatial domain subspace signals is provided with an orthogonal frequency-division multiplexing (OFDM)-based wireless device that includes a wireless terminal, a multiple-input and multiple-output (MIMO) antenna, a spatial subspace processor, and a temporal subspace processor. An uplink signal is transmitted from the wireless terminal towards a plurality of targets positioned within an operational range of the MIMO antenna. A plurality of reflected signals generated from the plurality of targets and is received through the MIMO antenna. The plurality of reflected signals is processed at the spatial subspace processor to determine a direction of arrival (DOA) for each of plurality of reflected signals. Each of the plurality of reflected signals is processed by the temporal subspace processor to determine a time delay. The time delay and the DOA are utilized to derive a location approximation for the plurality of targets.
1. A method of using time domain subspace signals and spatial domain subspace signals for location approximation through an orthogonal frequency-division multiplexing (OFDM)-based wireless device comprises the steps of:
(A) providing an orthogonal frequency-division multiplexing (OFDM)-based wireless device, wherein the OFDM-based wireless device comprises a wireless terminal, a multiple-input and multiple-output (MIMO) antenna, a spatial subspace processor, and a temporal subspace processor;
(B) transmitting a pilot uplink signal through the wireless terminal to a plurality of targets, wherein the plurality of targets is positioned within an operational range of the MIMO antenna;
(C) receiving an ambient signal through the MIMO antenna, wherein the ambient signal comprises a plurality of overlapping echo signals, wherein the plurality of overlapping echo signals is generated from each of the plurality of targets;
(D) deriving a direction of arrival (DOA) for each of the plurality of overlapping signals with the OFDM-based wireless device by processing the plurality of overlapping echo signals through the spatial subspace processor;
(E) calculating a time delay between the pilot uplink signal and each of the plurality of overlapping echo signals with the OFDM-based wireless device by processing the plurality of overlapping echo signals through the temporal subspace processor; and
(F) deriving a location approximation for the plurality of targets with the OFDM-based wireless device from the time delay for each of the plurality of overlapping echo signals and the DOA for each of the plurality of overlapping echo signals.
2. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 1 further comprises the steps of:
providing the spatial subspace processor with a multiple signal classification (MUSIC) algorithm; and
deriving the DOA for each of the plurality of overlapping echo signals by executing the MUSIC algorithm with the spatial subspace processor.
3. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 2 further comprises the steps of:
representing the plurality of overlapping echo signals as a representative eigenvector through the MUSIC algorithm;
estimating a maximum eigenvector through the MUSIC algorithm, wherein the maximum eigenvector is estimated from the representative algorithm; and
deriving the DOA for each of the plurality of overlapping echo signals by searching a corresponding subspace spanned by the maximum eigenvector.
4. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 1 further comprises the steps of:
providing the temporal subspace processor with a MUSIC algorithm; and
in step (E), calculating the time delay between the pilot uplink signal and each of the plurality of overlapping echo signals with the OFDM-based wireless device further by executing the MUSIC algorithm through the temporal subspace processor.
5. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 4 further comprises the steps of:
representing the plurality of overlapping echo signals as a representative eigenvector through the MUSIC algorithm;
estimating a minimum eigenvector through the MUSIC algorithm, wherein the minimum eigenvector is estimated from the representative eigenvector; and
calculating the time delay between the pilot uplink signal and each of the plurality of echo signals by searching a corresponding subspace derived from the minimum eigenvector.
6. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 5 , wherein the minimum eigenvector is orthogonal to a signature vector of each of the plurality of overlapping echo signals.
7. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 4 further comprises the steps of:
representing each of the plurality of overlapping echo signals as a representative eigenvector through the MUSIC algorithm;
deriving a likelihood ratio for a set of selected eigenvalues from the representative eigenvector with the MUSIC algorithm; and
assessing a quantity for the plurality of targets by performing a sequence of hypothesis tests for the set of selected eigenvalues with the MUSIC algorithm, wherein the sequence of hypothesis tests is performed by comparing the likelihood ratio for each of the set of selected eigenvalues.
8. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 1 further comprises the steps of:
providing the OFDM-based wireless device with a channel encoding module and a channel decoding module;
encoding the pilot uplink signal through the channel encoding module, wherein the pilot uplink signal is encoded before transmitting the pilot uplink signal from the wireless terminal; and
decoding each of the plurality of overlapping echo signals through the channel decoding module, wherein the plurality of overlapping echo signals is decoded after being received at the wireless terminal.
9. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 8 , wherein the pilot uplink signal is encoded through the channel encoding module as a direct-sequence spread spectrum (DSSS).
10. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 8 , wherein the pilot uplink signal is encoded as a pseudo-noise (PN) sequence.
11. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 1 further comprises the steps of:
providing the ambient signal with a downlink signal, wherein the downlink signal is transmitted from at least one base station that is communicably coupled with the OFDM-based wireless device;
providing the OFDM-based wireless device with a match-filtering unit;
transferring the ambient signal through the match-filtering unit; and
filtering out the downlink signal through the match-filtering unit and isolating the plurality of overlapping echo signals.
12. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 1 further comprises the steps of:
providing the OFDM-based wireless device with a radar processor;
transmitting the DOA for each of the plurality of overlapping echo signals from the spatial subspace processor to the radar processor;
transmitting the time delay for each of the plurality of overlapping echo signals from the temporal subspace processor to the radar processor; and
deriving the location approximation as an output of the radar processor.
13. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 1 further comprises the steps of:
wherein the MIMO antenna is an antenna array;
providing each antenna of the antenna array with at least one tapped delay line;
deriving the DOA for each of the plurality of overlapping echo signals by transmitting the plurality of overlapping echo signals through the spatial subspace processor;
transmitting a summation output from the spatial subspace processor to the temporal subspace processor, wherein the summation output is derived from each antenna of the antenna array; and
calculating the time delay between the pilot uplink signal and each of the plurality of overlapping echo signals with the temporal subspace processor.
14. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 1 , wherein a corresponding speed for each of the plurality of targets is derived from the location approximation.
15. The method of using time domain subspace signals and spatial domain subspace signals for location approximation through OFDM-based wireless device as claimed in claim 1 , wherein the pilot uplink signal comprises a plurality of subcarriers.