Method and system of time-of-arrival estimation for ultra wideband multi-band orthogonal frequency division multiplexing signals
A time-of-arrival (TOA) estimation method for multi-band orthogonal frequency division multiplexing (MB-OFDM) signals uses a simple equally-spaced channel model to recover the impulse response of the wireless channel, and locates the delay of the first channel path by minimizing the energy leakage from the first channel path. The TOA is estimated based on the delay. Such a method does not require channel information for TOA estimation at the receiver and does not require modification of the receiver structure. The method also avoids a sub-optimal solution known to occur in maximum likelihood (ML) estimation.
1. A method for estimating the time-of-arrival (TOA) of a received signal transmitted over a channel according to a multi-band orthogonal frequency division multiplexing scheme, comprising:
recovering an impulse response for the channel using a least-square method with regard to a measurement of the received signal; and
reconstructing the impulse response using taps spaced apart by a tap interval, wherein each tap has a unique tap index and is delayed by a fixed tap delay value, wherein the reconstruction includes:
a) with the fixed tap delay value equaling zero, determining a tap index approximating, a time for a first arriving path of the recovered signal; and
b) refining the approximation by varying the fixed tap delay value between zero and the tap interval to find a determined delay value that substantially minimizes the energy leakage of the first arriving path of the recovered channel, wherein the time-of-arrival (TOA) equals a delay for the determined tap index with the fixed tap delay value equaling the determined delay value, and wherein finding the determined delay value comprises calculating an energy ratio.
2. A method as in claim 1 , wherein reconstructing the impulse response comprises using a uniformly spaced discrete time model.
3. A method as in claim 2 , wherein the model comprises a predetermined number of multipaths.
4. A method as in claim 1 , wherein the energy ratio comprises a ratio between a given tap in the recovered channel impulse response and an average energy of the channel response before the given tap.
5. A method as in claim 4 , wherein the given tap corresponds to the first arriving path.
6. A method as in claim 1 , wherein the determined delay corresponds to an estimation of first TOA.
7. A method as in claim 6 , wherein the measured received signals are pilot signals.
8. A method as in claim 7 , wherein the pilot signals are transmitted over multiple frequency bands according to a frequency hopping algorithm.
9. A method as in claim 6 , wherein recovering the impulse response for the channel operates in a frequency domain impulse response.