CN106656889A - Ultra wideband indoor positioning method based on frequency modulation continuous waves - Google Patents

Abstract

The invention provides an ultra wideband indoor positioning method based on frequency modulation continuous waves. The method consists of three modules: a label terminal is a to-be-positioned entity and sends the frequency modulation continuous waves to the outside; the system is provided with a plurality of base stations, each base station is provided with antennas in pairs, two antennas receives the frequency modulation continuous waves with different delays and extract arrival time difference (TDOA) information through mixing, filtering, sampling, DFT and other modules in sequence, and each base station sends the TDOA information to a server; and the server integrates the TDOA information sent by each base station and solves nonlinear least squares optimization to obtain the position information of a to-be-positioned label. The system supports simultaneous positioning of a plurality of labels, and imports the frequency modulation continuous waves into the indoor positioning technology for the first time so as to bear distance difference information on easily extracted frequency information. The positioning precision of the system reaches a centimeter level, and compared with the traditional indoor positioning technology, the positioning precision is greatly improved.

Description

A kind of UWB indoor localization method based on Continuous Wave with frequency modulation

Technical field

The present invention relates to indoor positioning technologies field, especially a kind of UWB indoor positioning system based on Continuous Wave with frequency modulation System and localization method.

Background technology

In recent years, with the development of wireless communication field, context-aware services progressively become a reality, and service object Positional information be one of most important ambient parameter.Traditional global positioning system (Globle Positioning System, GPS) and cellular network location technology, can provide for outdoor user and more accurately position and navigation Service.But It is, indoors in environment, due to the impact of the barriers such as furniture, personnel and wall, wireless signal energy attenuation is occurred, is passed Speed and direction change are broadcast, causes traditional outdoor wireless location technology indoors can the larger error of producing ratio in environment. Thus, indoor wireless location technology becomes study hotspot in recent years.Interior based on multiple technologies such as wifi, visible ray, bluetooths Alignment system is succeeded in developing in succession, is widely used in business, public service and military field.

Used as a kind of novel short-distance wireless communication technology, it transmits information, phase using ultra-narrow pulse to ultra broadband (UWB) Ying Di, which occupies very wide bandwidth.UWB has the advantages that two-forty, low cost, low-power consumption, is accurately positioned, can be used as accurate room The physical-layer techniques of interior positioning, have broad application prospects.

The difference of common location algorithm information according to needed for position fixing process can be divided into two big class：Based on range finding (range-based), find range unrelated (range-free).Unrelated algorithm of wherein finding range need not determine distance and angle information, The information such as the general character are realized according only to network.Main algorithm has：Centroid algorithm, APIT (approximate point-in- Triangulation teat) subtriangular interior method of testing, DV-Hop etc..Measurement point is needed based on the location algorithm of range finding To the distance or angle information of point, then using trilateration, triangulation or maximum likelihood estimate calculate node position Put.Main algorithm has：TOA(time of arrival)、TDOA(Time Difference Of Arrival)、AOA(Angle of Arrival)、RSSI(Received Signal Strength Indication)。

At present, the research with regard to UWB indoor location technology just launches in academia, is recent study focus, but fixed Position precision also improves a lot space.

The content of the invention

The technical problem to be solved is to provide a kind of UWB indoor positioning side with more high position precision Method.

To realize above-mentioned technique effect, the technical solution adopted in the present invention is：

A kind of UWB indoor localization method based on Continuous Wave with frequency modulation, the method are comprised the following steps：

(1) Indoor Positioning System Using Ultra Wideband Radio based on Continuous Wave with frequency modulation is built, the system includes：Server, N number of label letter Number receiving base station, trigger generates base station and at least one label；Each label signal receives base station and is equipped with M to day Line, the receiving terminal of each pair antenna is at a distance of L rice；

(2) each refresh cycle be evenly dividing as T time slot, each label takes a time slot, any two label respectively Shared time slot is different；

(3) trigger generates base station and receives base station to all of label and label signal when arriving each refresh cycle Send trigger；

(4) label is used as entity to be positioned, after trigger is received, locally starting timing, and oneself Continuous Wave with frequency modulation signal is sent to the base station in communication range when time slot arrives；

(5) label signal receives base station after trigger is received, and is locally starting timing, to determine oneself when each The label corresponding to Continuous Wave with frequency modulation signal that gap is received；

(6) for any one label j and label signal receive base station i, label signal receives base station i and is receiving label After the Continuous Wave with frequency modulation signal that j sends, the Continuous Wave with frequency modulation signal received to each pair antenna carries out being mixed successively, low pass filtered Ripple, digital sample and DFT transform are processed, calculate on each pair antenna from label j Continuous Wave with frequency modulation signal reaching time-difference Information；And the M reaching time-difference information that amounts to for calculating is uploaded to into server；

(7) server is connect according to the reaching time-difference information and N number of label signal that each label signal receives base station transmission The position of each antenna of base station is received, is built to calculate problem model of the label position as target problem, by Solve problems model, Obtain label position.

Specifically, the Continuous Wave with frequency modulation signal is：

In formula, f₀For the original frequency of Continuous Wave with frequency modulation signal, the frequency of Continuous Wave with frequency modulation signal is f (t)=f₀+kt；k For Continuous Wave with frequency modulation signal frequency change slope,Persistent period of the T for Continuous Wave with frequency modulation signal；Connect for frequency modulation Continuous ripple signal initial phase, the phase place of Continuous Wave with frequency modulation signal is

Further, in the step (6), label signal receives the Continuous Wave with frequency modulation letter sent according to label j by base station i The method for number calculating the corresponding reaching time-difference information of itself each pair antenna is：

(3-1) two antennas defined during label signal receives base station i m to antenna are respectively i_m1And i_m2, i ∈ [1, 2 ..., N], m ∈ [1,2 ..., M]；Label j and i_m1And i_m2The distance between receiving terminal be respectively d₁、d₂；Calculate i_m1And i_m2 The Continuous Wave with frequency modulation signal from label j for receiving is respectively：

In formula, t₁、t₂The Continuous Wave with frequency modulation signal that respectively label j sends reaches i_m1、i_m2The time of receiving terminal, C is the light velocity；

(3-2) label signal receives base station i to s₁(t) and s₂T () is mixed, obtain：

In formula, Δ t=t₁-t₂；

(3-3) low-pass filtering is carried out to the mixing results that step (2-2) is obtained, obtains filtered signal：

(3-4) with sample frequency f_NS ' (t) is sampled, the discrete-time signal after note sampling is s (n)；

(3-5) DFT process is carried out to s (n), is obtained：

In formula, NDFT is the points for carrying out DFT；

(3-6) frequency for calculating s ' (t) is：After obtaining f ', by f ' substitutionsObtain the Continuous Wave with frequency modulation signal arrival i that label j sends_m1、i_m2The time of advent Difference information.

Further, the construction method of the problem model in the step (7) is：

Build cost function：

In formula, (a, b) represents the position coordinateses of label j to be asked；Base station i the m couple is received for label signal An antenna i in antenna_m1Position coordinateses；Another during base station i m are received to antenna for label signal Antenna i_m2Position coordinateses；Δd_imAntenna i is reached for the Continuous Wave with frequency modulation signal that label j sends_m1And i_m2Range difference；

Cost function is converted to into problem model：

In formula, (a ', b ') is the position coordinateses of the label j that Solve problems model is obtained.

Further, in the step (7), the method for Solve problems model is that classical Levenberg-Marquardt is calculated Method.

Further, before the mixing operation described in execution step (3-2), it is signal s₂T it is L rice that () increases by a segment length Transmission range, will s₂T () is converted to：

Now, signal s₁(t)、s₂T the delay inequality between () isΔ d=is calculated according to Δ t L-(d₁-d₂)。

Beneficial effect：Compared with prior art, the present invention has the advantage that：

1st, by using Continuous Wave with frequency modulation, TDOA information has been carried in the frequency information of signal, it is easy to extract, has been simplified System complexity.

2nd, according to the method for proposing, TDOA information is carried in the frequency information of signal, with significant noise robustness, And then improve positioning precision.

3rd, system does not require that label is accurate synchronous with base station, which greatly simplifies the complexity of device.

4th, reduce complexity in base station end, and in general, can by position error control 5 centimetres with It is interior.

Description of the drawings

Fig. 1 is that tab end realizes block diagram；

Fig. 2 is that label signal reception base station end realizes block diagram；

Fig. 3 is the TDOA information schematic diagrams that label signal receives that base station end is obtained；

Fig. 4 is alignment system performance simulation figure；

Fig. 5 is system position error rectangular histogram.

Specific embodiment

The invention will be further described below in conjunction with the accompanying drawings.

Fig. 1 to 2 show tab end and label signal receives base station end and realizes block diagram；

This programme is made up of three modules：Tab end is entity to be positioned, is sent out Continuous Wave with frequency modulation；System is equipped with Several base stations, each base station are equipped with double antenna, according to the Continuous Wave with frequency modulation received on two antennas, base station acquire up to when Between poor (TDOA) information, and TDOA information is sent to server by each base station；Send the comprehensive whole base station of server TDOA information, by solving Nonlinear least squares optimization, obtains the positional information of label to be positioned.

1. tab end design

Label is distributed in system optional position, is entity to be positioned.The frequency of Continuous Wave with frequency modulation (Chirp signals) is f (t)=f₀+ kt, whereinK is the slope of chirp signal frequencies change, and T is chirp signal durations.Phase place is The integration of frequency, the then phase place of Chirp signalsThen chirp signal expressions are

In real system, need to use single-chip microcomputer to produce the triangular wave that symmetry is 100%, and it is (voltage-controlled to be input to VCO Agitator) middle generation chirp signals.

2. base station end design and location algorithm

Some base stations are dispersed with system, including N number of label signal receives base station and a trigger generates base station.Often Individual label signal receives base station and is equipped with M to twin aerial, and in each pair antenna, two antennas are separated by L rice.Label signal receives base station The chirp signals for receiving, sequentially pass through frequency mixer, low-pass filtering, digital sample, FFT module, and most extract at last TDOA information is sent to server end.

Specifically, two antennas defined during label signal receives base station i m to antenna are respectively i_m1And i_m2, i ∈ [1,2 ..., N], m ∈ [1,2 ..., M]；Label j and i_m1And i_m2The distance between receiving terminal be respectively d₁、d₂；Calculate i_m1With i_m2The Continuous Wave with frequency modulation signal from label j for receiving is respectively：

In formula, t₁、t₂The Continuous Wave with frequency modulation signal that respectively label j sends reaches i_m1、i_m2The time of receiving terminal, C is the light velocity.

Base station is to two-way chirp signal s₁(t) and s₂T () is mixed, as a result for：

Wherein Δ t=t₁-t₂。

By the signal after mixing by a low pass filter, signal is left

Next frequency analyses are carried out to s ' (t) in base station end, specifically, first s ' (t) is sampled, meter sampling Frequency is f_N.Discrete-time signal after note sampling is s (n), and DFT (discrete Fourier transform) is carried out to s (n)：

Wherein NDFT is the points for carrying out DFT.

Then the frequency of continuous time signal s ' (t) for f ' is：

Obtain f ' afterwards, substitute intoFormula, just can obtain label to two days The TDOA information of line.

It should be strongly noted that the Δ t that obtains of above-mentioned algorithm Δ d is permanent positive in other words, that is, any root day cannot be distinguished by Chirp signals on line are first reached.So the present invention give also a kind of improved method, i.e., to certain the root antenna in double antenna (in the present embodiment be referred to as reference antenna) increases the time delay of a period of time, and it is to be passed through mixing in the signal of reference antenna to implement Before device, (two antennas of base station end are separated by L rice, according to the difference on triangle both sides less than the to first pass through one section long wire for L rice The principle on three sides, the ultimate range that L rice is the system are poor).After this improvement, Δ d=L- (d₁-d₂) it is just have Negative point, this follow-up location algorithm provides more information.

3. server end design and location algorithm

In server end, be the equal of to solve an optimization problem by TDOA information acquisition label position coordinates.If system N number of base station is had,An antenna i during base station i m are received to antenna for label signal_m1Position coordinateses；Another antenna i during base station i m are received to antenna for label signal_m2Position coordinateses；Δd_imFor label j The Continuous Wave with frequency modulation signal for sending reaches antenna i_m1And i_m2Range difference；Then to the label, note cost function is：

So the two-dimensional coordinate of final positioning result, the i.e. label：

Solve this nonlinear least square problem, it is possible to use classical Levenberg-Marquardt algorithms. The algorithm seeks maximum (little) value using gradient, belongs to one kind of " climbing the mountain " method.It has the advantages that gradient method and Newton method simultaneously. When damping factor λ very little, step-length is equal to Newton method step-length, and when λ is very big, step-length is approximately equal to the step-length of gradient descent method.

4. the support multi-tag scheme of system

The alignment system of the present invention can support multi-tag.Scheme is that a refresh cycle is divided into multiple time slots, often Individual label regularly takes certain time slot.There is a special base station in system, specially when arriving each refresh cycle to institute Some labels and base station send trigger.Label after trigger is received, locally starting timing, so as to oneself when Chirp signals are sent when gap arrives；Base station is locally starting timing, to determine when certain equally after trigger is received Label corresponding to gap.So as to system realizes the support to multi-tag.

For example, if whole system require 0.1s refresh rate, then by 0.1s be divided into multiple a length of 250us when Gap, each label regularly take some time slot.Whole system can support most 400 labels.In the time slot of a 250us In, the protection interval of each 25us in two ends, middle 200us are the length of chirp signals.At the same time, individually have one in system Individual base station, referred to as trigger generate base station, and trigger generates base station and sends a trigger every 0.1s, indicates new One time location updating starts.All of label and base station can all receive this trigger, and each comfortable local timing.From And system realizes the support to multi-tag.Assume that whole system is in the region of 30m*30m, it is assumed that trigger have propagated 30m is received, and will also produce the delay of 10ns, and this is almost negligible compared to 25us.

Technical scheme content is further illustrated below by a specific embodiment.

If system coverage area is 15 meters * 15 meters, system is equipped with 6 base stations, and each base station is equipped with double antenna, two antennas 2 meters of interval, the reference antenna in two antennas has 2 meters of extra time delay.Alliance refresh rate be 0.1 second once, system Support 400 labels, the time slot that each label takes is 250us altogether, and respectively take out 25us in front and back as protection interval, i.e., each The chirp signals that label is sent every time continue 200us.Chirp signals upper side frequency is 1.06GHz, down-converts to 895MHz, i.e., Chirp signal slopesIf wireless channel is awgn channel, signal to noise ratio is 1dB.And base station end sampling frequency Rate is 2MHz, and FFT points are 2048 points.Simulation result is as shown in Fig. 3,4,5.

From simulation result as can be seen that most of tag location error is within 6 centimetres, average localization error is 4.64 centimetre.Compared to traditional indoor positioning technologies, this is a huge raising in positioning precision.

The above is only the preferred embodiment of the present invention, it should be pointed out that：For the ordinary skill people of the art For member, under the premise without departing from the principles of the invention, some improvements and modifications can also be made, these improvements and modifications also should It is considered as protection scope of the present invention.

Claims (6)

1. a kind of UWB indoor localization method based on Continuous Wave with frequency modulation, it is characterised in that include：

(1) Indoor Positioning System Using Ultra Wideband Radio based on Continuous Wave with frequency modulation is built, the system includes：Server, N number of label signal connect Receive base station, a trigger and generate base station and at least one label；Each label signal receives base station and is equipped with M to antenna, often To the receiving terminal of antenna at a distance of L rice；

(2) each refresh cycle be evenly dividing as T time slot, each label takes a time slot respectively, shared by any two label Time slot is different；

(3) trigger generates base station and receives base station transmission to all of label and label signal when arriving each refresh cycle Trigger；

(4) label is used as entity to be positioned, after trigger is received, locally starting timing, and in the time slot of oneself Continuous Wave with frequency modulation signal is sent to the base station in communication range during arrival；

(5) label signal receives base station after trigger is received, and is locally starting timing, oneself is being received in each time slot with determining The label corresponding to Continuous Wave with frequency modulation signal for arriving；

(6) for any one label j and label signal receive base station i, label signal receives base station i and is receiving label j After the Continuous Wave with frequency modulation signal for sending, the Continuous Wave with frequency modulation signal received to each pair antenna carries out being mixed successively, low-pass filtering, number Word sample and FFT process, calculate each pair antenna on from label j Continuous Wave with frequency modulation signal reaching time-difference information； And the M reaching time-difference information that amounts to for calculating is uploaded to into server；

(7) server receives reaching time-difference information and the N number of label signal reception base that base station sends according to each label signal The position of each antenna stood, builds to calculate problem model of the label position as target problem, by Solve problems model, obtains Label position.

2. a kind of UWB indoor localization method based on Continuous Wave with frequency modulation according to claim 1, it is characterised in that institute Stating Continuous Wave with frequency modulation signal is：

In formula, f₀For the original frequency of Continuous Wave with frequency modulation signal, the frequency of Continuous Wave with frequency modulation signal is f (t)=f₀+kt；K is tune The slope of frequency continuous wave signal frequency change,Persistent period of the T for Continuous Wave with frequency modulation signal；For Continuous Wave with frequency modulation Signal initial phase, the phase place of Continuous Wave with frequency modulation signal is

3. a kind of UWB indoor localization method based on Continuous Wave with frequency modulation according to claim 2, it is characterised in that institute In stating step (6), label signal receives Continuous Wave with frequency modulation signal of change itself each pair antenna pair sent according to label j by base station i The method of the reaching time-difference information answered is：

(3-1) two antennas defined during label signal receives base station i m to antenna are respectively i_m1And i_m2, i ∈ [1,2 ..., N], m ∈ [1,2 ..., M]；Label j and i_m1And i_m2The distance between receiving terminal be respectively d₁、d₂；Calculate i_m1And i_m2Receive The Continuous Wave with frequency modulation signal from label j be respectively：

In formula, t₁、t₂The Continuous Wave with frequency modulation signal that respectively label j sends reaches i_m1、i_m2The time of receiving terminal, C is the light velocity；

(3-2) label signal receives base station i to s₁(t) and s₂T () is mixed, obtain：

In formula, Δ t=t₁-t₂；

(3-3) low-pass filtering is carried out to the mixing results that step (2-2) is obtained, obtains filtered signal：

$s^{\′}\left(t\right)=\frac{1}{2}\cos [2\mathrm{\π}{f}_0\mathrm{\Δt}+\mathrm{k\π}({\mathrm{\Δt}}^2+2\mathrm{t\Δt})]$

(3-4) with sample frequency f_NS ' (t) is sampled, the discrete-time signal after note sampling is s (n)；

(3-5) DFT process is carried out to s (n), is obtained：

$S_{\mathrm{DFT}}\left(\mathrm{\τ}\right)=\mathrm{DFT}\left[s\left(n\right)\right]=\underset{n=0}{\overset{\mathrm{NDFT}-1}{\mathrm{\Σ}}}s\left(n\right)*e^{j2\mathrm{\π\τ}/N}$

In formula, NDFT is the points for carrying out DFT；

(3-6) frequency for calculating s ' (t) is：After obtaining f ', by f ' substitutionsObtain the Continuous Wave with frequency modulation signal arrival i that label j sends_m1、i_m2The time of advent Difference information.

4. a kind of UWB indoor localization method based on Continuous Wave with frequency modulation according to claim 3, it is characterised in that institute The construction method for stating the problem model in step (7) is：

Build cost function：

$f(a,b)=\underset{i=1}{\overset{N}{\mathrm{\Σ}}}\underset{m=1}{\overset{M}{\mathrm{\Σ}}}[\sqrt{{(a-x_{i_{m1}})}^2+{(b-y_{i_{m1}})}^2}-\sqrt{{(a-x_{i_{m2}})}^2+{(b-y_{m_1})}^2}-{\mathrm{\Δd}}_{\mathrm{im}}{]}^2$

In formula, (a, b) represents the position coordinateses of label j to be asked；Base station i m are received to antenna for label signal In an antenna i_m1Position coordinateses；Another antenna during base station i m are received to antenna for label signal i_m2Position coordinateses；Δd_imAntenna i is reached for the Continuous Wave with frequency modulation signal that label j sends_m1And i_m2Range difference；

Cost function is converted to into problem model：

$(a^{\′},b^{\′})=\arg \underset{a,b}{\min }f(a,b)$

In formula, (d ', b ') is the position coordinateses of the label j that Solve problems model is obtained.

5. a kind of UWB indoor localization method based on Continuous Wave with frequency modulation according to claim 4, it is characterised in that institute The method for stating Solve problems model in step (7) is classical Levenberg-Marquardt algorithms.

6. a kind of UWB indoor localization method based on Continuous Wave with frequency modulation according to claim 5, it is characterised in that Before mixing operation described in execution step (3-2), it is signal s₂T () increases transmission range of the segment length for L rice, will s₂(t) Be converted to：

Now, signal s₁(t)、s₂T the delay inequality between () isΔ d=L- (d are calculated according to Δ t₁- d₂)。