Naohiko Iwakiri

Ultra-Wideband Time-of-Arrival and Angle-of- Arrival Estimation Using Transformation Between Frequency and Time Domain Signals

This paper presents an ultra wideband (UWB) channel sounding scheme with a technique for time of arrival (TOA) and angle of arrival (AOA) estimation using transformation between time and frequency domain signals. Since the measured UWB power spectrum can be transformed into a time domain signal, both frequency and time domain signals are available for the channel estimation. We propose the TOA estimation using a peak search over time domain signal, and the AOA estimation using MUSIC and AOA histograms. The AOA histogram is counted for AOA samples of discrete frequencies over the UWB bandwidth. Comparing both AOA histograms before and after TOA subtraction, we can determine pairing the elements of TOA vector and those of AOA vector. The anechoic chamber tests indicated that both TOAs and AOAs were precisely resolved for two-path model, even if either TOAs or AOAs were too close to resolve.

Ultra-Wideband Time-of-Arrival and Angle-of-Arrival Estimation Using a Signal Model Based on Measurements

This paper presents an ultra wideband (UWB) channel sounding scheme with a technique for estimating time of arrival (TOA) and angle of arrival (AOA) using measurement signals. Since the power spectrum over the UWB bandwidth can be measured in advance, we propose a signal model using the measurement power spectrum to design the proper UWB signals model. This signal model is more similar to measurement signals than the flat spectrum model which is an ideal model. If more than three waves impinge on a receiver, we must determine the proper grouping of the elements of TOA vector and AOA vector. It is difficult to determine the grouping using only measurement signals because of many degradation factors. We also propose pairing the elements of TOA vector and that of AOA vector using correlation method based on measurement signals and the proposed signal model. This technique is available for more than the case of three paths if pairing the estimated TOAs and AOAs of measurement signals is not accurately determined. We evaluated the proposed techniques for a vector network analyzer (VNA) with a three-dimensional virtual antenna array.

Joint TOA and AOA/AOD Spectrum for Ultra-Wideband Indoor Double-Directional Channel Estimation

This paper presents an ultra-wideband (UWB) double-directional channel sounding technique using transformation between time domain (TD) and frequency domain (FD) signals. We proposed the time-of-arrival (TOA), angle-of- arrival (AOA) estimation algorithm and angle-of-departure (AOD) with some modifications of our previous work. There were four main advantages of the proposed estimation technique as follows: implementation of the simple antenna array with fixed element spacing; the TOA estimation using a peak search over TD signals with high resolution; the angle estimation using the multiple signal classification (MUSIC) and angle histograms over FD signals; pairing the TOAs and the AOAs precisely. We develop the joint TOA and AOA/AOD spectrum for the double-directional channel. Although the level does not indicate true power but the weighted spectral peaks based on the TD signals and the weighted occurrence ratio of the MUSIC spectrum, the level distributions including dominant multipath components predicted by ray-tracing can be viewed as clusters for both line of sight (LOS) and non-LOS environments.

Joint TOA and AOA Estimation of UWB Signal Using Time Domain Smoothing

This paper presents an ultrawide-band (UWB) channel sounding scheme with a technique for estimating time of arrival (TOA) and angle of arrival (AOA) using an antenna array time domain smoothing. The smoothing averages over the time domain UWB signals of several immediate neighbor elements of the array, which is expected to be similar to the increasing number of snapshots as well as the mitigation of the TOA estimation error. After the TOA estimation using the time domain smoothing UWB signal, one time domain sample corresponding to the strongest TOA was eliminated. Then fast Fourier transform (FFT) was performed and AOA was estimated for every frequency point. These processes were iterated after selecting the next strongest TOA until all the available TOAs were eliminated. The result of anechoic chamber tests using two sources indicated that the resolution of TOA was more than 1 ns, that of AOA was more than 3deg for half wavelength element spacing.

Ultra-wideband spatio-temporal channel sounding with use of an OFDM signal in the presence of narrowband interference

An Ultra wideband (UWB) spatio-temporal channel sounder, employing an orthogonal frequency division multiplexing (OFDM) signal and a receiving virtual array antenna was prototyped and evaluated in a narrowband interference environment. Channel information of the OFDM signal was estimated from the measured data. Time of arrival (TOA) was calculated by correlating the received waveforms with a template. Angle of arrival (AOA) was derived by employing a multiple signal classification (MUSIC) algorithm and an angular histogram method proposed by the authors. The frequency spectrum and the AOA of the narrowband interference signal can be simultaneously estimated by means of the same methodology. Propagation experiments were carried out to validate the techniques in one- and two-path environments in a radio anechoic chamber. The bandwidths of the UWB OFDM and the narrowband signals were respectively 500 and 20 MHz. The TOA and the AOA of the wideband signal were estimated within reasonable bounds of error in the presence of narrowband interference, and the AOA and the occupied bandwidth of the narrowband signal were also satisfactorily estimated.