Patent Application
20110032152
This application claims the benefit of Taiwan application Serial No. 98126835, filed Aug. 10, 2009, the subject matter of which is incorporated herein by reference.
1. Field of the Disclosure
The disclosure relates in general to a method and apparatus for positioning a mobile device, and more particularly to a seamless and mixed method and apparatus for positioning a mobile device.
2. Description of the Related Art
Global Positioning System (GPS) is a system which locates the longitude and latitude coordinate information of an object globe-wide by using the satellite. The GPS is cheap and easy to access, and has better positioning efficiency in outdoor open field. However, the GPS still has some disadvantages like expensive hardware cost and time delay in first time positioning. Besides, due to existing restrictions, the GPS normally has poor or interrupted reception at high building, tunnel or indoor space. Thus, how to precisely position the user's position in an indoor environment has become an issue attracting wide discussion and study. Wherein, the method for positioning a user in an indoor environment by using the radio frequency (RF) signal is provided.
Examples of the positioning methods using the radio frequency signal such as the wireless network triangulation method and the wireless network pattern matching method normally are involved with the characteristic values or parameters such as time of arrival (TOA), angle of arrival (AOA) or the intensity of radio frequency signal. Wherein, the wireless network triangulation positioning method locates the user's position according to the distance between the user and many access points (AP) through mathematical or physical principles.
Besides, the wireless network pattern matching method locates the user's position through the comparison of characteristic values between the user's location and many access points. However, as the signal intensity decay mode is not easy to construct and the signal intensity is unstable, positioning drift may easily occur to the above positioning methods using the radio frequency signal, and such occurrence would generate illogical user moving paths. Besides, the above methods cannot effectively position 3D movements in a multi-story building.
The disclosure is directed to a method and apparatus for positioning a mobile device. The positioning method performs positioning by sensing the moving track or behavior mode of a mobile device and using the radio frequency signal, and possesses both positioning accuracy and positioning efficiency when the positioning method is applied in a large-scaled environment.
According to an aspect of the present disclosure, a method for positioning a mobile device is provided. The method includes the following steps. Based on a prior location point of the mobile device, many sample particles are generated according to a prior probability distribution associated with the prior location point. A current moving track or a current behavior mode of the mobile device is obtained, and the sample particles are moved according to at least one of the current moving track and the current behavior mode. A current supposed status is obtained based on a radio frequency signal. A current probability distribution of the sample particles corresponding to the radio frequency signal or the current supposed status is generated to obtain corresponding weights of the moved sample particles. A current location point of the mobile device is obtained according to the weights and distribution of the sample particles.
According to another aspect of the present disclosure, a mobile device positioning apparatus is provided. The apparatus includes a receiver, a sensing feedback unit and a processor. The receiver is for receiving a radio frequency signal. The sensing feedback unit is for obtaining a current moving track or a current behavior mode of the mobile device. The processor is coupled to the receiver and the sensing feedback unit. Wherein, the processor generates a plurality of sample particles based on a prior location point of the mobile device according to a prior probability distribution associated with the prior location point, moves the sample particles according to at least one of the current moving track and the current behavior mode, obtains a current supposed status based on the radio frequency signal, generates a current probability distribution of the sample particles corresponding to the radio frequency signal or the current supposed status to obtain corresponding weights of the moved sample particles, and obtains a current location point of the mobile device according to the weights and distribution of the sample particles.
The disclosure will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.
The disclosure provides a method and apparatus for positioning a mobile device. The positioning method performs positioning by sensing the moving track or the behavior mode of a mobile device and using the radio frequency signal, hence decreasing positioning drift, increasing positioning accuracy, and boosting positioning efficiency when the positioning method is applied in a large-scaled environment.
The mobile device positioning apparatus of the disclosure can function independently or function in coorporated with various mobile devices, such as a mobile phone, a personal digital assistant or a navigation device. The mobile device positioning apparatus being incorporated with a mobile device is exemplified below. Referring to
The mobile device positioning apparatus 120 includes a receiver 122, a sensing feedback unit 124, a map information unit 126 and a processor 128. The receiver 122 is for receiving a radio frequency signal, such as a global positioning system (GPS) signal, a WiFi signal, a Zigbee message, a GSM signal, a Bluetooth signal or other radio frequency signals, and no particular restriction is applied here. The sensing feedback unit 124 is for obtaining a current moving track or a current behavior mode of the mobile device 100. The map information unit 126 is for storing and providing map information, and no particular restriction is applied here. The map information can also be transmitted to the receiver 122 from an external server, and then the receiver 122 further provides the map information to the processor 128 so as to save cost for the map information unit 126. That is, the map information unit 126 substantially is an option element. The processor 128 is coupled to the receiver 122, the sensing feedback unit 124 and the map information unit 126.
Based on a prior location point of the mobile device 100, the processor 128 generates many sample particles according to a prior probability distribution associated with the prior location point. The processor 128 further moves the sample particles according to at least one of the current moving track and the current behavior mode. That is, the processor 128 may move the sample particles according to one or both of the current moving track and the current behavior mode. Then, based on the radio frequency signal, the processor 128 obtains a current supposed status, generates a current probability distribution of the sample particles corresponding to the radio frequency signal or the current supposed status to obtain corresponding weights of the moved sample particles. Afterwards, the processor 128 obtains a current location point of the mobile device 100 according to the weights and distribution of the sample particles.
Referring to
Next, the method proceeds to the sampling stage S300, the sample particles are randomly moved. Then, the method proceeds to the prediction stage S400, based on the radio frequency signal received by the receiver 122, the processor 128 obtains an initial supposed status, which can be obtained by many positioning methods using the radio frequency signal (such as the wireless network triangulation method or the wireless network pattern matching method). The processor 128 generates an initial probability distribution of the sample particles corresponding to the radio frequency signal or the initial status to obtain corresponding weights of the moved sample particles, and obtains a first location point of the mobile device according to the weights and distribution of the sample particles. The first positioning procedure terminates here. Wherein, the processor 128 generates the probability distribution corresponding to the radio frequency signal by comparing the radio frequency signal with multiple characteristic values stored in an internal or an external database.
For the mobile device 100, the location point obtained in the t-th positioning procedure is a prior location point of the (t+1)-th positioning procedure, wherein t is a positive integer. Referring to
Referring to
Corresponding to stage 602 and step S302, each sample particle in the sample space 610 can move the current moving track {right arrow over (u)} and becomes scattered to obtain a sample space 612. Each sample particle in the sample space 610 can also perform a conic random divergent projection according to each sample particle in the sample space 610 and becomes scattered to obtain the sample space 612. That is, no particular restriction is applied to the implementations of moving sample particles according to the current moving track {right arrow over (u)}. The sample particles can be scattered around the actual position Lt+1 of the moved mobile device 100 through the current moving track {right arrow over (u)} and will not be scattered in a mess, therefore the overall positioning accuracy is increased.
Afterwards, in step S304, the processor 128 determines whether to adopt the map information mode. If yes, the method proceeds to step S306, otherwise, the method proceeds to step S308. If the map information mode is adopted, then the processor 128 determines whether the moving paths of the sample particles are logical or not according to the received map information after the sample particles are moved according to the current moving track {right arrow over (u)}. If the moving paths of the sample particles are illogical, then the processor 128 removes the sample particles corresponding to illogical paths. As indicated in the stage 604 of
The practice of moving the sample particles by the processor 128 according to the association between the current moving track {right arrow over (u)} and the map information is applicable to position a user who is moving in a 3D space of a multi-story building. That is, the current moving track {right arrow over (u)} can be a moving track of the mobile device 100 on a 2D plane or in a 3D space. For example, in cooperation with the map information, the processor 128 can activate the setting of the floor at a staircase or an elevator, and obtains the moving track through the sensing feedback apparatus 124 according to the change in the g value sensed by the g sensor. Thus, the sample particles can be scattered towards different floors, and the problem of positioning a user who is moving in a 3D space of a multi-story building is thus resolved.
In the stage 606 of
Then, the method proceeds to prediction stage S400, based on the radio frequency signal received by the receiver 122, the processor 128 obtains a current supposed status, which can be obtained by many positioning methods using the radio frequency signal (such as the triangulation method using the GPS signal or the pattern matching method using the WiFi signal). The processor 128 generates a current probability distribution of the sample particles corresponding to the radio frequency signal or the current supposed status to obtain corresponding weights of the moved sample particles, wherein the corresponding weight of each sample particle can be the probability of the current probability distribution or a new weight obtained by adjusting the prior weight according to the probability of the current probability distribution. The current probability distribution is such as Gaussian distribution. The higher the weight, the higher the probability of the mobile device 100 locating on the position corresponding to the sample particle. To the contrary, the lower the weight, the lower the probability of the mobile device 100 locating on the position corresponding to the sample particle. Thus, the processor 128 obtains a current location point Et+1 of the mobile device 100 according to the weights and distribution of the sample particles. Wherein, the processor 128 can select the sample particle with highest weight as the current location point Et+1, or select the central position of the sample particles with first K highest weights as the current location point Et+1, but it is not limited thereto. Thus, the overall positioning accuracy is increased. The (t+1)-th positioning procedure terminates here. A cycle of steps S300˜S500 is repeated in each time of positioning procedure.
The method and apparatus for positioning a mobile device disclosed in above embodiments of the disclosure have many advantages exemplified below:
According to the method and apparatus for positioning a mobile device disclosed in the disclosure, the particle filter algorithm succeeds many positioning methods using the radio frequency signal, and the positioning range of the mobile device is narrowed by the moving track and the behavior mode of the mobile device obtained according to the map information and in cooperation with the sensing feedback element, so as to decrease the drift and inaccuracy problem of the intensity of the radio frequency signal, increase the overall positioning accuracy, raise the positioning efficiency when the positioning method is applied in a large-scaled environment, and resolve the problem of positioning a user who is moving in a 3D space of a multi-story building.
While the disclosure has been described by way of example and in terms of a preferred embodiment, it is to be understood that the disclosure is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.
| Number | Date | Country | Kind |
|---|---|---|---|
| 98126835 | Aug 2009 | TW | national |
