Method and apparatus for positioning

CROSS-REFERENCE TO RELATED APPLICATION

0001This application claims priority to and the benefit of Korean Patent Application No. 10-2009-0093228 and 10-2010-0095194 filed in the Korean Intellectual Property Office on Sep. 30, 2009 and Sep. 30, 2010, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

0002(a) Field of the Invention

0003The present invention relates to a method and apparatus for positioning. More particularly, the present invention relates to a method and apparatus for wirelessly positioning a terminal on the basis of the types of propagation delay.

0004(b) Description of the Related Art

0005Wireless positioning is a technology of positioning a terminal, using a wireless communication system, and this field has been recently increased with the increase of demands for location based service (LBS). Particularly, the wireless positioning technology is increasingly under the spotlight, in accordance with the increase in demand for a technology that can provide users with appropriate service by determining the user's situation and position.

0006Global positioning system (GPS) that is a representative wireless positioning technology provides positioning results with high accuracy, but has a problem in that a terminal in a room cannot receive a GPS signal and only a terminal equipped with a GPS receiver can receive a GPS signal.

0007Accordingly, as another wireless positioning technology, an received signal strength indicator (RSSI) method and a time difference of arrival (TDOA) method have been considered. The RSSI method is a method of acquiring positional information, using the intensity of a received signal. According to the RSSI method, the positional information can be easily acquired because the structure is simple, but errors are generated due to path loss.

0008The TDOA method is a method of acquiring positional information, using a difference in the arrival time of signals. According to the TDOA, time synchronization is not needed between a receiver and a transmitter, but time synchronization is required between the transmitters.

0009The above-mentioned wireless positioning technology, for example, all of the GPS, RSSI method and TDOA method cannot provide accurate positioning results under a non-line of sight (NLOS) environment or an environment having a bad channel condition. Accordingly, a method that provides an accurate positioning result by reflecting the propagation environment of signals is required.

SUMMARY OF THE INVENTION

0010The present invention has been made in an effort to provide a method and apparatus for wireless positioning having advantages of considering the types of propagation delay.

0011An exemplary embodiment of the present invention provides a method for wireless positioning, which includes: receiving signals from a plurality of transmitters; determining propagation delay tabs of the plurality of transmitters, from the signals received from the plurality of transmitters, respectively; setting the order of the plurality of transmitters in accordance with the propagation delay tabs; measuring distances between a receiver and the transmitter, respectively; and estimating the position of the receiver, by using the order and the measured distance.

0012Another exemplary embodiment of the present invention provides a method for wireless positioning, which includes: receiving signals from a plurality of transmitters; determining propagation delay tabs of the plurality of transmitters, from the signals received from the plurality of transmitters; setting a reference transmitter in the plurality of transmitters on the basis of the plurality of propagation delay tabs; estimating the position of a receiver by using the distance between a receiver and the reference transmitter; and correcting the position of the receiver by using the distance between the receiver and the other transmitters, except for the reference transmitter, in the plurality of transmitters.

0013Yet another exemplary embodiment of the present invention provides an apparatus for wireless positioning that includes: a signal receiving unit that receives signals from a plurality of transmitters; a propagation environment determining unit that determines propagation delay tabs of the plurality of transmitters, from the signal received from the plurality of transmitters; a transmitter order setting unit that sets the order of the plurality of transmitters in accordance with the propagation delay tabs; a distance measuring unit that measures the distance between the receiver and each of the transmitters; and a position estimating unit that estimates the position of the receiver by using the order and the measured distances.

BRIEF DESCRIPTION OF THE DRAWINGS

0014<figref idrefs="DRAWINGS">FIG. 1A</figref> to <figref idrefs="DRAWINGS">FIG. 1D</figref> are diagrams showing a type of propagation delay tab.

0015<figref idrefs="DRAWINGS">FIG. 2</figref> is an apparatus for wireless positioning according to an exemplary embodiment of the present invention.

0016<figref idrefs="DRAWINGS">FIG. 3</figref> is a method of wireless positioning according to an exemplary embodiment of the present invention. The apparatus for wireless positioning may be a part of a receiver.

0017<figref idrefs="DRAWINGS">FIG. 4</figref> to <figref idrefs="DRAWINGS">FIG. 6</figref> are diagrams exemplifying a method of estimating the position of a receiver by an apparatus for wireless positioning according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

0018In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

0019In the specification, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

0020In the specification, a terminal may designate a mobile station (MS), mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), a user equipment (UE), and an access terminal (AT), etc. and may include the entire or partial functions of the terminal, the mobile station, the mobile terminal, the subscriber station, the portable subscriber station, the user equipment, the access terminal, etc.

0021In the specification, a base station (BS) may designate a radio access station (RAS), a node B, an evolved node B (eNodeB), a base transceiver station (BTS), and a mobile multihop relay (MMR)-BS, etc. and may include the entire or partial functions of the base station, the radio access station, the node B, the enodeB, the base transceiver station, and the MMR-BS, etc.

0022Hereinafter, method and apparatus for wireless positioning according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawing.

0023<figref idrefs="DRAWINGS">FIG. 1A</figref> to <figref idrefs="DRAWINGS">FIG. 1D</figref> are diagrams showing a type of propagation delay tab.

0024A propagation delay tab means that a signal transmitted from a transmitter under a multipath environment is a delay spread shape. When a geographical obstacle exists between a transmitter and a receiver, a multipath is formed by reflection or diffraction of a signal due to the obstacle. Therefore, one signal transmitted from the transmitter is delay-spread through the multipath.

0025Referring to <figref idrefs="DRAWINGS">FIG. 1A</figref>, the signal intensity of a propagation delay tab <b>10</b> which earliest arrives at the receiver is largest. When an geographical obstacle does not exist between the transmitter and the receiver, a signal transmitted from the transmitter can arrive at the receiver, with high signal intensity within a short time. Accordingly, the type of <figref idrefs="DRAWINGS">FIG. 1A</figref> may be a type of propagation delay under an line of sight (LOS) environment.

0026Referring to <figref idrefs="DRAWINGS">FIG. 1B</figref>, the signal intensity of a propagation delay tab <b>21</b> which arrives second at the receiver is the largest, and the signal intensity of a propagation delay tabs <b>20</b> that arrives first is smaller than the signal intensity of a propagation delay tab <b>21</b>.

0027Referring to <figref idrefs="DRAWINGS">FIG. 10</figref>, the signal intensity of a propagation delay tab <b>31</b> which arrives third at the receiver is the largest, and the signal intensity of a propagation delay tabs <b>30</b> that arrives first is smaller than the signal intensity of a propagation delay tab <b>31</b>.

0028Referring to <figref idrefs="DRAWINGS">FIG. 1D</figref>, the signal intensity of a propagation delay tab <b>41</b> which arrives latest at the receiver is the largest, and the signal intensity of a propagation delay tabs <b>40</b> that arrives first is smaller than the signal intensity of a propagation delay tab <b>41</b>.

0029As the types of propagation delay tab become similar to the types of <figref idrefs="DRAWINGS">FIG. 1A</figref>, the environment between the transmitter and the receiver is close to the LOS environment. Further, as the type of propagation delay tabs becomes similar to the types of <figref idrefs="DRAWINGS">FIG. 1D</figref>, the environment between the transmitter and the receiver is close to the non-line of sight environment.

0030<figref idrefs="DRAWINGS">FIG. 2</figref> is a diagram showing an apparatus for wireless positioning according to an exemplary embodiment of the present invention and <figref idrefs="DRAWINGS">FIG. 3</figref> is a diagram showing a method for wireless positioning according to an exemplary embodiment of the present invention. The apparatus for wireless positioning may be a part of a receiver. Assume that the apparatus for wireless positioning knows the position of a peripheral transmitter.

0031Referring to <figref idrefs="DRAWINGS">FIG. 2</figref>, an apparatus <b>200</b> for wireless positioning includes a signal receiving unit <b>210</b>, a propagation environment determining unit <b>220</b>, a transmitter order setting unit <b>230</b>, a distance measuring unit <b>240</b>, and a position estimating unit <b>250</b>.

0032Referring to <figref idrefs="DRAWINGS">FIG. 2</figref> and <figref idrefs="DRAWINGS">FIG. 3</figref>, the signal receiving unit <b>210</b> receives signals transmitted from a plurality of transmitters (S<b>300</b>). The signals transmitted from the transmitter, for example, may be reference signals for positioning. Hereinafter, it is exemplified that the signal receiving unit <b>210</b> receives reference signals for positioning from the plurality of transmitters, respectively.

0033The propagation environment determining unit <b>220</b> determines propagation delay tabs for the signals transmitted from the plurality of transmitters (S<b>310</b>). In other words, the propagation environment determining unit <b>220</b> determines the arrival time of a propagation delay tab having the largest signal intensity in the propagation delay tabs of each of the transmitters. Meanwhile, the propagation environment determining unit <b>220</b> can determine the propagation environment on the basis of the propagation delay tabs. For example, when the types of propagation delay tabs for signals transmitted from the transmitters are similar to <figref idrefs="DRAWINGS">FIG. 1A</figref>, that is, it is determined that the propagation environment between the transmitters and corresponding receivers is the LOS environment, as the signal intensity of the propagation delay tabs arriving first is the largest. As another example, when the type of propagation delay tabs for the signals transmitted from the transmitter are similar to <figref idrefs="DRAWINGS">FIG. 1B</figref> to <figref idrefs="DRAWINGS">FIG. 1D</figref>, that is, it is determined that the propagation environment between the transmitters and corresponding receivers is close to the NLOS environment, as the propagation delay tab having the largest signal intensity arrives late.

0034The transmitter order setting unit <b>230</b> sets the order of the transmitters, using the results determined by the propagation environment determining unit <b>220</b> (S<b>320</b>). For example, the order may be set as a prior order, as the propagation environment is close to the LOS environment, and the order is set as a latter order, as the propagation environment may be close to the NLOS environment.

0035The distance measuring unit <b>240</b> measures the distances between the transmitters and the receivers (S<b>330</b>). In this case, the distance measuring unit can measures the distance between the transmitter and the receiver, respectively, using the arrival time of the propagation delay tab arriving first in the propagation delay tabs of the transmitters.

0036The position estimating unit <b>250</b> estimates the positions of the receiver, using the order set by the transmitter order setting unit <b>230</b> and the distances measured by the distance measuring unit <b>240</b> (S<b>340</b>). For example, it is possible to estimate the position of the receiver on the basis of the distance between the prior order transmitter and the receiver and to correct the position of the receiver by using the distance between the latter order transmitter and the receiver.

0037Hereinafter, a detailed method of estimating the position of a receiver by the apparatus for wireless positioning will be described.

0038<figref idrefs="DRAWINGS">FIG. 4</figref> to <figref idrefs="DRAWINGS">FIG. 6</figref> are diagrams exemplifying a method of estimating the position of a receiver by an apparatus for wireless positioning according to an exemplary embodiment of the present invention.

0039Referring to <figref idrefs="DRAWINGS">FIG. 4</figref> to <figref idrefs="DRAWINGS">FIG. 6</figref>, a receiver <b>400</b> that is an object of wireless positioning receives reference signals for positioning from a plurality of transmitters around the receiver, for example, three transmitters <b>500</b>, <b>600</b>, and <b>700</b>. The receiver <b>400</b> analyzes the propagation delay tabs for the reference signals received from the transmitters <b>500</b>, <b>600</b>, and <b>700</b>, respectively. Assume that the receiver <b>400</b> knows the positions of the transmitters <b>500</b>, <b>600</b>, and <b>700</b>, the arrival time of the propagation delay having the largest signal intensity is the shortest in the transmitter <b>500</b>, and the arrival time of the propagation delay tabs having the largest signal intensity longest from the transmitter <b>600</b> to the transmitter <b>700</b>. Accordingly, assume that the propagation environment between the receiver <b>400</b> and the transmitter <b>500</b> is close to the LOS environment, and the propagation environments are closer to the NLOS environment from the transmitter to the transmitter <b>700</b>.

0040Referring to <figref idrefs="DRAWINGS">FIG. 4</figref>, the transmitter <b>500</b> having the propagation environment closest to the LOS is a reference transmitter. The receiver <b>400</b> measures the distance between the reference transmitter <b>500</b> and the receiver <b>400</b>, using the arrival time and light speed of the propagation delay tab arriving first in the propagation delay tabs of the reference transmitter <b>500</b>. The receiver <b>400</b> determines that the receiver <b>400</b> is positioned on a circle spaced apart as much as the calculated distance from the reference transmitter <b>500</b> because the propagation environment determined by the propagation delay tab is LOS.

0041Referring to <figref idrefs="DRAWINGS">FIG. 5</figref>, the receiver <b>400</b> measures the distance between the transmitter <b>600</b> having the propagation environment that is close to the LOS environment, next to the reference transmitter <b>500</b>, and the receiver <b>400</b> and forms a circle Y having a center at the transmitter <b>600</b>. The distance between the transmitter <b>600</b> and the receiver <b>400</b> can be measured by using the arrival time and light speed of the propagation delay tab arriving the first in the propagation delay tabs of the transmitter <b>600</b>.

0042Accordingly, the receiver <b>400</b> can determine that the receiver <b>400</b> is positioned at an intersection C or an intersection E of the circle Y having a center at the transmitter <b>600</b> and the circle X having a center at the transmitter <b>500</b>.

0043Referring to <figref idrefs="DRAWINGS">FIG. 6</figref>, the receiver <b>400</b> corrects the intersection C calculated through the process descried with reference to <figref idrefs="DRAWINGS">FIG. 4</figref> and <figref idrefs="DRAWINGS">FIG. 5</figref> in the direction of the transmitter <b>700</b>. In this case, a start point for a position correction is the intersection C by a circle Z having a center at the transmitter <b>700</b>. In other words, the receiver <b>400</b> can perform the correction that the receiver <b>400</b> is positioned at any point D on the straight line connecting the intersection C with the transmitter <b>700</b>. For example, the receiver <b>400</b> calculates the distance between the transmitter <b>700</b> having the propagation environments close to the NLOS environment and the receiver <b>400</b>, and set a circle Z having a center at the transmitter. Further, the position of the receiver <b>400</b> can be corrected to the intersection of the straight line connecting the intersection C with the position of the transmitter <b>700</b> and a circle Z having a center at the transmitter <b>700</b>. The correction method is not limited thereto. The distance may be corrected by various methods based on the circle Z. For example, if a radius of the circle Z is large, the distance may be corrected from the intersection E.

0044In the above, for better comprehension and ease of description, although it is assumed that the receiver receives reference signals for positioning from three transmitters, the scope of the present invention is not limited thereto. The receiver may receive reference signals for positioning from three or more transmitters, and may perform positioning on the basis of the received reference signals according to the propagation environment priority of LOS.

0045As described above, when the wireless positioning is performed on the basis of types of the propagation delay tabs, an error of wireless positioning generated when the propagation environments are close to the NLOS environment can be reduced.

0046According to the exemplary embodiments of the present invention, method and apparatus for wireless positioning, considering the types of propagation delay are provided. Accordingly, it is possible to reduce errors in positioning, according to the propagation environment between transmitters and a receiver.

0047The above-mentioned exemplary embodiments of the present invention are not embodied only by an apparatus and method. Alternatively, the above-mentioned exemplary embodiments may be embodied by a program performing functions, which correspond to the configuration of the exemplary embodiments of the present invention, or a recording medium on which the program is recorded.

0048While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.