Receiver, receiver for positioning system using the same, and positioning method

• US 7,912,481 B2
• Filed: 06/25/2007
• Issued: 03/22/2011
• Est. Priority Date: 09/27/2006
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Mizugaki, Kenichi, Fujiwara, Ryosuke, Miyazaki, Masayuki
• Primary Examiner(s): Appiah; Charles N
• Assistant Examiner(s): STEPHEN, EMEM O
• Application Number:
  US11/767,560
• Publication Number:
  US 20080075151A1
• Time in Patent Office: 1,366 Days
• Field of Search: 455/456.1, 455/456.5, 455/404.2, 455/414.2, 342450-465, 340988-996
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

An invention for estimating the first path of an arrival signal by a method and device with a simple structure and lower power consumption. In this method, the nominal pulse repetition frequency or its integer multiple are A/D converted at a frequency less than the multiplicative inverse of the pulse width, the AD conversion timing is offset by time resolution Δt and the receive signal measured, data stored in a RAM, and the first path output time is estimated based on sequentially rearranging of the stored waveform data.

Claims

1. A receiver comprising:

a waveform measuring unit to perform multiple analog-to-digital conversions on the received signal while shifting the timing at each Δ

t a frequency identical to the nominal pulse repetition frequency of a transmit signal made up of intermittent pulse signals subjected to direct spreading or an integer multiple of the same frequency, and at a frequency lower than the multiplicative inverse of the pulse width, and store the observation data from the receive signal in a storage area; and

a first path estimator unit to estimate the arrival time of the first path arriving earliest time-wise in the receive signal, based on the stored observation data from the receive signal,

wherein the observation data in the waveform measuring unit is waveform data includes;

peak values for matched filter outputs obtained at each measurement timing by applying matched filter processing containing tap coefficients matching the spreading code applied to the data after analog-to-digital conversion of the transmit signal; and

the output time of those peak values,

wherein the first path estimator unit includes an output time estimator unit, a threshold comparator unit, and a minimum detector unit,

wherein the output time estimator unit to calculate the output time differential between the demodulated path and the arrival time data T(N) for the multiple waveform data M(1−

K), and waveform data for the peak values of the output time P(1−

K),

wherein the threshold comparator unit compares the waveform data M(1−

K) with the specified threshold TH, and outputs the arrival time T(N) when M(N)>

TH is satisfied, and

wherein the minimum detector unit estimates the minimum value for the arrival time data T(N) as the first path.

2. The receiver according to claim 1, wherein the measurement data in the waveform measuring unit includes:

multiple higher-ranked waveform data containing peak values for matched filter outputs obtained at each measurement timing by applying matched filter processing containing tap coefficients matching the spreading code applied to the data after analog-to-digital conversion of the transmit signals; and

the output time of those waveform data values.

3. The receiver according to claim 1,

wherein the first path estimator unit decides that the observation data with the earliest arrival time exceeding a preset threshold is the first path signal.

4. The receiver according to claim 1,

wherein the first path estimator unit finds the time differential between the respective demodulated path and the output time of each peak value in the stored waveform data, and finds the arrival time matching the respective waveform data from that time differential.

5. The receiver according to claim 4,

wherein the receive signal contains a synchronization tracker unit for tracking the clock of the receiver, and

wherein the first path estimator unit estimates the frequency deviation between the receiver and the transmitter serving as the transmission source of the transmission signal from the synchronization tracker unit, and uses those frequency deviation results to correct the calculated arrival time.

6. The receiver according to claim 1,

wherein the first path estimator unit includes a threshold calculator unit, and

wherein this threshold calculator unit finds the threshold value TH from the waveform data string P(1−

K) stored in the storage area.

7. The receiver according to claim 6,

wherein the threshold calculator unit finds the threshold value TH from the following formula TH=maximum value for M(1−

K)/A (where A is here an appropriate constant).

8. The receiver according to claim 1,

wherein the output time calculator unit includes a time measurement unit, an output time differential calculator unit, and a time phase converter unit,

wherein the time measurement unit measures the time that the receive synchronization signal is inputted,

wherein the output time differential calculator unit calculates the differential in respective arrival times T(1−

K) for the data M(1−

K), and the receive synchronization signal utilizing the measurement result from the input time and the time data string P(1−

k), and

wherein the time phase converter unit converts the time differential T(1−

K) into a spread pulse string for the arrival time data T(N).

9. The receiver according to claim 8,

wherein the time phase converter unit converts the time differential T(1−

K) into a spreading pulse string phase T(N) based on the following formula;

Mod(T(1−

K), TcxNs) with the pulse interval set as Tc, and the spreading code length set as Ns where the mod(a,b) is defined as a remainder in case that a is divided by b.

10. The receiver according to claim 1,

wherein the transmit/receive signal is UWB-IR, and

wherein the timing Δ

t that sequentially at which the receive signal analog-to-digital conversion is sequentially shifted, is a smaller value than the pulse width WTP of the UWB-IR.

11. The receiver according to claim 1, further comprising a demodulating-synchronization tracking unit for performing demodulation and synchronization processing and also generating a receive synchronizing signal.

12. A positioning system receiver comprising:

a terminal for transmitting a positioning signal;

a reference station for sending a reference signal;

a plurality of base stations for receiving the positioning signal and the reference signal; and

a positioning server for calculating the position of the terminal and a network connecting the base station with the positioning server,

wherein each base station comprises;

a waveform observation unit to perform multiple analog-to-digital conversions on the received signal while shifting the timing at each Δ

t a frequency identical to the nominal pulse repetition frequency of a transmit signal made up of intermittent pulse signals subjected to direct spreading, or an integer multiple of the same frequency, and at a frequency lower than the multiplicative inverse of the pulse width, and storing the peak value at each timing as receive signal observation data in a storage area;

a first path estimator unit for estimating the arrival time of the first path arriving earliest time-wise in the receive signal, based on the stored multiple arrival time observation data;

a time differential measurement unit for measuring the receive time differential between the reference signal and the positioning signal by using the clock signal, based on the first path arrival time of each receive signal; and

a transmit unit for transmitting the time information containing the differentials in receive times to the positioning server,

wherein the positioning server comprises a position calculator unit to calculate the position of the terminal based on the time transmitted from each base station, and

wherein the observation data in the waveform measurement unit includes;

waveform data that are peak values for matched filter outputs obtained at each measurement timing by applying matched filter processing containing tap coefficients matching the spreading code applied to the data after analog-to-digital conversion to the transmit signal; and

the output times for those peak values, and

wherein the arrival time of the first path arriving earliest time-wise in the receive signal is estimated by rearranging the arrival times of peak value output times in the waveform data, based on the arrival time data, and

wherein the first path estimator unit includes an output time estimator unit, a threshold comparator unit, and a minimum detector unit,

wherein the output time estimator unit to calculate the output time differential between the demodulated path and the arrival time data T(N) for the multiple waveform data M(1−

K), and waveform data for the peak values of the output time P(1−

K),

wherein the threshold comparator unit compares the waveform data M(1−

K) with the specified threshold TH, and outputs the arrival time T(N) when M(N)>

TH is satisfied, and

wherein the minimum detector unit estimates the minimum value for the arrival time data T(N) as the first path.

13. The positioning system receiver according to claim 12,

wherein the first path estimator in each base station decides that the observation data with the earliest arrival time exceeding a preset threshold is the first path signal.

14. The positioning system receiver according to claim 12,

wherein the first path estimator unit in each base station, finds the time differential between the respective demodulated path and the output time of each peak value in the stored waveform data, and finds the arrival time matching the respective waveform data, from that time differential.

15. The positioning system receiver according to claim 12,

wherein each base station contains a synchronization tracker unit for tracking the clock of the receiver in the receive signal, and

wherein the first path estimator unit estimates the frequency deviation between the receiver and the transmitter serving as the transmission source of the transmission signal from the synchronization tracker unit, and uses those frequency deviation results to correct the calculated arrival time.

16. A positioning method for a terminal in a wireless device including a terminal for transmitting a positioning signal, a reference station for sending a reference signal and, multiple base stations for receiving the positioning signal and the reference signal and, a positioning server for calculating the position of the terminal and a network connecting the positioning server with the base station, the positioning method comprising the steps of:

in each base station,

performing multiple analog-to-digital conversions on the received signal while shifting the timing at each Δ

t a frequency identical to the nominal pulse repetition frequency of a transmit signal made up of intermittent pulse signals subjected to direct spreading, or an integer multiple of the same frequency, and at a frequency lower than the multiplicative inverse of the pulse width, and storing the peak value at each timing as receive signal observation data in a storage area;

estimating the arrival time of the first path arriving earliest time-wise in the receive signal based on the stored multiple arrival time observation data;

measuring the receive time differential between the reference signal and the positioning signal by using the clock signal based on the first path arrival time of each receive signal; and

transmitting the time information containing the differential in receive times to the positioning server, and

in the positioning server,

calculating the position of the terminal based on the time transmitted from each base station,

wherein a transmit packet for packet communication comprises a preamble section, SFD section, and data section, the SFD section being a pattern with an established information format, and

wherein the positioning method further comprising the steps of

storing the AD converted waveform data (M, P) is stored in a RAM;

measuring the time from the time that waveform observation ends to the time the SFD unit is detected to set measured value as Ts;

estimating the frequency differentials from the data being demodulated after SFD detection to find the estimation value δ

;

calculating the time T(N)=Ts+Te (P(N)) from each waveform observation time to the SFD detection time;

calculating the phase differential PH(N) in the spreading pulse string from each waveform observation time until the SFD detection time; and

estimating the minimum N among N that satisfy M(N)>

TH as the first path.