WO2009025501A2

WO2009025501A2 - Positioning method using digital audio broadcasting and transmitter for the same

Info

Publication number: WO2009025501A2
Application number: PCT/KR2008/004856
Authority: WO
Inventors: Sun Kyu Park; Huen Tae Ha; Dennis Workman
Original assignee: Wavedigm Co., Ltd.; Trimble Navigation Ltd.
Priority date: 2007-08-20
Filing date: 2008-08-20
Publication date: 2009-02-26
Also published as: WO2009025501A3; WO2009025501A9

Abstract

A positioning method includes: generating a plurality of digital audio broadcasting (DAB) signals in a plurality of transmitters, each of the plurality of DAB signals including a series of transmission frames and each transmission frame including a synchronization channel (SC), a fast information channel (FIC) and a main service channel (MSC); transmitting the plurality of DAB signals such that the SC has a first power and each of the FIC and the MSC has a second power lower than the first power; measuring receiving times of the plurality of DAB signals in a mobile terminal; and determining a location of the mobile terminal using the receiving times.

Description

POSITIONING METHOD USING DIGITAL AUDIO BROADCASTING AND TRANSMITTER FOR THE SAME

Technical Field

[1] The present invention relates to a positioning method, and more particularly, to an indoor positioning method using a digital audio broadcasting and a system for the positioning method.

[2]

Background Art

[3] Recently, a network infrastructure has been widely provided according to development in information and communication technology. In addition, as a high digital device is generally utilized in daily life, a ubiquitous generation has come on the basis of the high digital device. To satisfy various requests of customers in the ubiquitous generation, research and development on recognition and positioning of an object have been suggested.

[4] Although a positioning system according to the related art has been developed for an outdoor circumstance using a global positioning system (GPS) signal, a positioning system utilized in an indoor circumstance becomes the subject of recent research and development because user services of a ubiquitous system are provided in an indoor circumstance that is a main living space. An indoor positioning system is applied to various fields. For example, one in an emergency may be rescued by informing a rescue center of his location through an indoor positioning system. In a field such as a distribution and a circulation, various services and an added value may be created by tracing and analyzing a user's purchase process through an indoor positioning system. In addition, an indoor positioning system may be applied to looking for a path or a friend.

[5] When a location of an object is recognized in a positioning system, a high technology such as an accurate recognition is required on the basis of cost. However, dynamic movements and static obstacles influence location recognition, thereby causing accuracy errors in recognition and data losses. Accordingly, it is the subject of a positioning system to recognize and trace an object accurately.

[6] A triangulation method, a scene analysis method and a proximity method are the three principal techniques for positioning. A positioning system may employ them individually or in combination. Among the three principal techniques, a triangulation method, where a location, i.e., a coordinate of an object is obtained by measuring and analyzing distance between the object and each transmitter, has been widely used. [7] FIG. 1 is a view showing a positioning method for an object using a triangulation method according to the related art. In FIG. 1, when an object O is disposed at a location among first, second and third servers Sl, S2 and S3, elapsed times for transmitting a signal from each server Sl, S2 and S3 to the object O are measured and distances between each server Sl, S2 and S3 and the object O are calculated. Since it can be assumed that the signal is transmitted with a velocity of light, a first distance dl between the first server Sl and the object O is obtained by measuring the first elapsed time for transmitting a first signal from the first server S 1 to the object O and multiplying the first elapsed time by the velocity of light. Similarly, a second distance d2 between the second server S2 and the object O and a third distance d3 between the third server S3 and the object O are obtained by measuring the second and third elapsed time. As a result, a first circle that has a location of the first server Sl as a center and the first distance dl as a radius, a second circle that has a location of the second server S2 as a center and the second distance d2 as a radius and a third circle that has a location of the third server S3 and the third distance d3 as a radius are described, and the intersection of the first, second and third circles is obtained as the location of the object O.

[8]

Disclosure of Invention

Technical Problem

[9] Among various positioning systems, a GPS has been widely used. In the GPS, a spatial location of an object is obtained by measuring elapsed times for transmitting a signal from each satellite, whose exact location is known by a traced orbit, to the object. However, although the GPS has a wide positioning range, an apparatus for the GPS is too expensive and a positioning accuracy is reduced in an indoor circumstance or a downtown because of errors due to reflection, diffraction and scattering of the satellite signal. To solve the above problems in the positioning accuracy, a GPS repeater may be formed at a roof of a building for re-transmitting the satellite signal. However, an installation cost for the GPS further increases by the repeater. Accordingly, the GPS is used for an outdoor circumstance such as a car navigation system rather than for an indoor circumstance.

[10] Moreover, an active bat system and an active badge system have been suggested as an indoor positioning system. However, the active bat system requires a high foundation technology for efficiency and accuracy, thereby increasing cost. In the active badge system, an infrared signal of an active badge is received through a network sensor and a location of the active badge is calculated. However, light interferes in transmission of the infrared signal and the infrared signal is hard to penetrate a tiny obstacle. Further, since a relatively large number of readers and gateways are required, there exists a limitation in applying the active badge system to a large space such as a large factory and an amusement park. Technical Solution

[11] Accordingly, the present invention is directed to a positioning method using a digital audio broadcasting and a transmitter for the positioning method that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.

[12] An object of the present invention is to provide a positioning method where a signal loss due to interferences is minimized and a system for the positioning method.

[13] Another object of the present invention is to provide a positioning method where a transmission power and a number of transmitters are minimized by using signals in a synchronization channel of a transmission frame of a digital audio broadcasting (DAB) signal or a terrestrial digital multimedia broadcasting (TDMB) signal for recognizing location information of the transmitters, and a system for the positioning method.

[14] Another object of the present invention is to provide a positioning method where a pseudo random noise (PRN) code is added to a digital audio broadcasting signal (DAB) signal or a terrestrial digital multimedia broadcasting (TDMB) signal for recognizing location information of the transmitters, and a system for the positioning method

[15] A positioning method includes: generating a plurality of digital audio broadcasting

(DAB) signals in a plurality of transmitters, each of the plurality of DAB signals including a series of transmission frames and each transmission frame including a synchronization channel (SC), a fast information channel (FIC) and a main service channel (MSC); transmitting the plurality of DAB signals such that the SC has a first power and each of the FIC and the MSC has a second power lower than the first power; measuring receiving times of the plurality of DAB signals in a mobile terminal; and determining a location of the mobile terminal using the receiving times.

[16] In another aspect, a positioning method includes: generating a plurality of digital audio broadcasting (DAB) signals in a plurality of transmitters, each of the plurality of DAB signals including a series of transmission frames and each transmission frame including a synchronization channel (SC), a fast information channel (FIC) and a main service channel (MSC); adding a pseudo random noise (PRN) code to at least one of the SC, the FIC and the MSC; transmitting the plurality of DAB signals such that each of the SC, the FIC and the MSC has a first power and the PRN code has a second power; measuring receiving times of the plurality of DAB signals in a mobile terminal; and determining a location of the mobile terminal using the receiving times. [17] In another aspect, a transmitter for a positioning method includes: a transmission frame multiplexing unit receiving a data for a fast information channel (FIC) and a data for a main service channel (MSC); an FIC/MSC symbol generating unit generating a first symbol corresponding to the data for the FIC and the data for the MSC; a synchronization channel (SC) symbol generating unit generating a second symbol corresponding to a data for an SC; a first gain block amplifying a power of the second symbol by a first gain; an orthogonal frequency division multiplex (OFDM) signal generating unit generating an OFDM signal using the first symbol and the second symbol amplified by the first gain; and a transmitter identification information (TII) signal generating unit generating a TII signal and synthesizing the TII signal and the OFDM signal to output a digital audio broadcasting (DAB) signal.

[18] In another aspect, a transmitter for a positioning method includes: a transmission frame multiplexing unit receiving a data for a fast information channel (FIC) and a data for a main service channel (MSC); an FIC/MSC symbol generating unit generating a first symbol corresponding to the data for the FIC and the data for the MSC; a synchronization channel (SC) symbol generating unit generating a second symbol corresponding to a data for an SC; an orthogonal frequency division multiplex (OFDM) signal generating unit generating an OFDM signal using the first symbol and the second symbol; a transmitter identification information (TII) signal generating unit generating a TII signal and synthesizing the TII signal and the OFDM signal to output a digital audio broadcasting (DAB) signal; a pseudo random noise (PRN) code generating unit generating a PRN code; and a gain block amplifying a power of the PRN code by a gain and adding the PRN code to the DAB signal such that the PRN code overlaps the DAB signal.

[19] In another aspect, a positioning method includes: generating a plurality of digital audio broadcasting (DAB) signals in a plurality of transmitters, each of the plurality of DAB signals including a series of transmission frames; adding a pseudo random noise (PRN) code to at least one of the series of transmission frames sequentially with respect to the plurality of DAB signal; transmitting the plurality of DAB signals including the PRN code to a mobile terminal; and calculating distances from the mobile terminal to the plurality of transmitters using the PRN code.

[20] In a positioning method includes: generating a plurality of digital audio broadcasting

(DAB) signals in a plurality of transmitters, each of the plurality of DAB signals including a transmission frame; adding a pseudo random noise (PRN) code to the transmission frame; transmitting the plurality of DAB signals including the PRN code to a mobile terminal; transmitting a global positioning system (GPS) signal to the mobile terminal; and calculating distances from the mobile terminal to the plurality of transmitters alternately using the PRN code and the GPS signal. Advantageous Effects

[21] A positioning method of the present invention determines the location of an object using a DAB signal or a T-DMB signal without an additional cost for installation. In addition, since a DAB signal or a T-DMB signal is transmitted such that channels of a transmission frame of the DAB signal or the T-DMB signal have different powers, an increase of transmitters and an additional cost for the increase are minimized. Furthermore, since location information and time offsets of adjacent transmitters are transmitted with a DAB signal or a T-DMB signal, an autonomous positioning at a mobile terminal is obtained. Moreover, a positioning method of the present invention accurately determines the location of an object using a PRN code added to a DAB signal or a T-DMB signal without an additional cost for installation.

[22]

Brief Description of the Drawings

[23] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention.

[24] FIG. 1 is a view showing a positioning method for an object using a triangulation method according to the related art

[25] FIG. 2 is a view showing a positioning method according to an embodiment of the present invention;

[26] FIG. 3 is a transmitter for a positioning system according to a first embodiment of the present invention;

[27] FIG. 4 is a view showing a transmission frame of a DAB signal for a positioning method according to a first embodiment of the present invention;

[28] FIG. 5 is a view showing a transmission power of a DAB signal for a positioning method according to a first embodiment of the present invention;

[29] FIG. 6 is a view showing a cell coverage of DAB signals for a positioning method according to a first embodiment of the present invention;

[30] FIG. 7 is a transmitter for a positioning system according to a second embodiment of the present invention;

[31] FIG. 8 is a view showing a transmission power of a DAB signal for a positioning method according to a second embodiment of the present invention;

[32] FIG. 9 is a view showing a cell coverage of DAB signals for a positioning method according to a third embodiment of the present invention;

[33] FIG. 10 is a view showing a transmission power of a DAB signal for a positioning method according to a third embodiment of the present invention;

[34] FIG. 11 is a view showing a transmission frame of a DAB signal for a positioning method according to a fourth embodiment of the present invention;

[35] FIG. 12 is a view showing a transmitter for a positioning system according to a fourth embodiment of the present invention;

[36] FIG. 13 is a view showing a cell coverage of DAB signals for a positioning method according to a fifth embodiment of the present invention;

[37] FIG. 14 is a view showing transmission frames of DAB signals for a positioning method according to a fifth embodiment of the present invention;

[38] FIG. 15 is a view showing a mobile terminal for a positioning method according to a fifth embodiment of the present invention; and

[39] FIG. 16 is a view showing an AGC loop of a mobile terminal for a positioning method according to a sixth embodiment of the present invention.

[40]

Mode for the Invention

[41] Reference will now be made in detail to embodiments which are illustrated in the accompanying drawings. Wherever possible, similar reference numbers will be used to refer to the same or similar parts.

[42] In an indoor positioning method according to an embodiment of the present invention, a location, i.e., a spatial coordinate of an object is obtained by a trian- gulation method using a digital audio broadcasting (DAB) signal or a terrestrial digital multimedia broadcasting (TDMB) signal. Since the TDMB system has the same physical layer as the DAB system, exemplary embodiments using the DAB signal will be illustrated hereinafter. Further, it is apparent that the present invention can be applied to the TDMB signal.

[43] FIG. 2 is a view showing a positioning method according to an embodiment of the present invention.

[44] In FIG. 2, a location of a mobile terminal M is traced using a DAB signal. When the mobile terminal M is disposed at a location among first, second and third transmitters Tl, T2 and T3 of a DAB system, each of the first, second and third transmitters Tl, T2 and T3 transmits a DAB signal to the mobile terminal M. The mobile terminal M records a receiving time information of the DAB signals from the first, second and third transmitters Tl, T2 and T3 and transmits the receiving time information to a location calculating server (not shown) using another communication means such as a cellular phone. Since the location calculating server already has a sending time information of the DAB signals at the first, second and third transmitters Tl, T2 and T3 and an exact location information of the first, second and third transmitters Tl, T2 and T3, the location calculating server calculates a first distance Dl between the first transmitter Tl and the mobile terminal M, a second distance D2 between the second transmitter T2 and the mobile terminal M and a third distance D3 between the third transmitter T3 and the mobile terminal M using the transmitted receiving time information and the sending time information, and obtains the location of the mobile terminal M through a triangulation method on the basis of the exact location information. Next, the location calculating server may transmit the location of the mobile terminal M through another communication means to the mobile terminal M or to a service server.

[45] For example, since first, second and third DAB signals TSl, TS2 and TS3 from the first, second and third transmitters Tl, T2 and T3, respectively, are assumed to be transmitted to the mobile terminal M with a velocity of light, the location calculating server may obtain the first, second and third distance Dl, D2 and D3 by multiplying first, second and third elapsed times, respectively, by the velocity of light. In addition, the first, second and third distance Dl, D2 and D3 may be calculated on the basis of a time offset defined by a time for transmitting each DAB signal is transmitted from a terminal of each transmitter Tl, T2 and T3 to an antenna of each transmitter Tl, T2 and T3. For example, each of the first, second and third elapsed times for the triangulation method may be calculated by subtracting the time offset and the sending time from the receiving time for each of the first, second and third DAB signals.

[46] When the first, second and third transmitters Tl, T2 and T3 are synchronized with each other, a time monitoring station for determining an absolute time is not required. Further, when the first, second and third transmitters Tl, T2 and T3 are not synchronized with each other, the positioning system has the exact sending time information and the exact receiving time information using an additional time monitoring station. For example, the time monitoring system in the positioning system may measure and transmit the exact receiving times for each of the first, second and third DAB signals to the location calculating server. The location calculating server having the sending time information and the exact location information calculate calculates the time offset of each of the first, second and third transmitters Tl, T2 and T3, and may use the time offset for the positioning method or transmit the time offset to the mobile terminal M through another communication means for another usage.

[47] Moreover, since each of the first, second and third DAB signals includes a transmitter identification information for each of the first, second and third transmitters Tl, T2 and T3, the mobile terminal M discriminates the first, second and third DAB signals using their transmitter identification information. The mobile terminal M transmits the transmitter identification information with the receiving time information to the location calculating server.

[48] Since the location calculation server has the sending time information of the DAB signals and the exact location information of the transmitters, the location calculating server calculates the location of the mobile terminal M through the triangulation method using the receiving time information, the sending time information and the exact location information. In addition, the location calculating server may transmit the location of the mobile terminal M to the mobile terminal M so that a user can recognize his location or may transmit the location of the mobile terminal M to a corresponding service server.

[49] Specifically, when each of the first, second and third DAB signals includes the location information of adjacent transmitters, the mobile terminal M recognizes the location thereof without the location calculating server. For example, the mobile terminal M may calculate the location thereof through a triangulation method using the first, second and third distances Dl, D2 and D3 and the location information of the first, second and third transmitters Tl, T2 and T3. As a result, the mobile terminal M has a function of an autonomous positioning. The mobile terminal M calculates the elapsed times of the DAB signals using the time offsets of the DAB signals, the sending time information and the receiving time information, and the distances from the transmitters using the elapsed times. The sending time information may be added to the DAB signal and may be transmitted from the transmitters to the mobile terminal M. Further, the mobile terminal M obtains the location thereof through the triangulation method using the distances and the location information of the transmitters.

[50] Further, the exact location of the mobile terminal M is obtained by sensing a first received DAB signal among the DAB signals from the transmitters even when the mobile terminal M is disposed in an indoor circumstance. When the mobile terminal M is in a building, the DAB signal may be transmitted to the mobile terminal M through three paths: a direct penetration though the building; a reflection on objects outside the building; and a diffraction at the building. Since the DAB signal transmitted through the reflection or the diffraction generally arrives at the mobile terminal M later than the DAB signal transmitted through the penetration, the mobile terminal M repeatedly receives the same DAB signal at different timings. The repeated reception of the DAB signal causes inaccuracy in measurement of the receiving time. In the positioning method according to an embodiment of the present invention, since only the first received DAB signal among the DAB signals through penetration, reflection and diffraction is used for calculation of the distances between the transmitters and the mobile terminal M, the location of the mobile terminal M is obtained without interference due to the DAB signals through the other paths.

[51] FIG. 3 is a transmitter for a positioning system according to a first embodiment of the present invention.

[52] In FIG. 3, the transmitter 100 includes a transmission frame multiplexing unit 110, a fast information channel/main service channel (FIC/MSC) symbol generating unit 120, an orthogonal frequency division multiplex (OFDM) signal generating unit 130, a synchronization channel (SC) symbol generating unit 140, a transmitter identification information (TII) signal generating unit 150 and a first gain block 160.

[53] The transmission frame multiplexing unit 110 receives a data for an FIC and a data for an MSC from exterior and transmits the data for an FIC and the data for an MSC to the FIC/MSC symbol generating unit 120. The FIC/MSC symbol generating unit 120 generates an FIC/MSC symbol corresponding to the data for the FIC and the MSC, and transmits the FIC/MSC symbol to the OFDM signal generating unit 130. The SC symbol generating unit 140 generates an SC symbol corresponding to a data for the SC. The power of the SC symbol is amplified by a first gain Gl through the first gain block 160 and the amplified SC symbol is transmitted to the OFDM signal generating unit 130.

[54] The OFDM signal generating unit 130 generates an OFDM signal using the FIC/

MSC symbol and the SC symbol. The TII signal generating unit 150 generates a TII signal including information for identification of the transmitter and synthesizes the TII signal and the OFDM signal such that the TII signal is inserted into a null symbol of the SC in the transmission frame of the OFDM signal, thereby outputting a DAB signal.

[55] Accordingly, since the FIC/MSC symbol and the SC symbol are independently generated and supplied to the OFDM signal generating unit 130, the powers of the FIC/MSC symbol and the SC symbol are independently adjusted. In addition, the first gain block 160 may adjust the power of the SC symbol separately from the power of the FIC/MSC symbol so that the SC symbol can have a different power from the FIC/ MSC symbol. As a result, the SC of the OFDM signal may have a cell boundary greater than the FIC/MSC of the OFDM signal and a wider cell coverage may be obtained with a smaller number of transmitters in the positioning system.

[56] For the purpose of utilizing the DAB system for the positioning method, a power of the DAB signal may be increased or a number of the transmitters may be increased. However, the increase of the power of the FIC/MSC symbol having a DAB data for the positioning method is a waste of signal, and the increase of the number of the transmitters is investment duplication in the DAB system. The positioning system according to an embodiment of the present invention uses the SC symbol in the transmission frame of the DAB signal for calculating the location, and the FIC/MSC symbol having a data of DAB system remains without increase in power. Since the SC symbol having a short duration is transmitted with a higher power and the FIC/MSC symbol is transmitted without increase in power, a power amplifier in the transmitter of the DAB system is used for the positioning system without replacement, and an additional cost for the power amplifier is not required. Further, since the SC symbol does not use a forward error correction method that is used for the FIC/MSC symbol, the SC symbol has a higher signal to noise (S/N) ratio than the FIC/MSC symbol.

[57] The relation between the channel and the power of the OFDM signal will be illustrated hereinafter. FIG. 4 is a view showing a transmission frame of a DAB signal for a positioning method according to a first embodiment of the present invention, and FIG. 5 is a view showing a transmission power of a DAB signal for a positioning method according to a first embodiment of the present invention.

[58] In FIGs. 4 and 5, the transmission frame of the DAB signal includes an SC, an FIC and an MSC, and has a duration of about 96msec. The SC includes a null symbol and a phase reference symbol. The phase reference symbol is a reference of an initial phase for the FIC and the MSC, and the null symbol and the phase reference symbol are used for synchronization. The FIC and the MSC include 3 symbols and 72 symbols, respectively, and various information is added to the FIC and the MSC. The null symbol and the phase reference symbol of the SC have a first section tl and a second section t2, respectively, as a duration and the FIC/MSC has a third section t3 as a duration.

[59] A transmitter identification information (TII) is selectively added to the null symbol of the SC. Accordingly, the mobile terminal M (of FIG. 2) discriminates the first, second and third transmitters Tl, T2 and T3 (of FIG. 2) using the TII of the DAB signals and transmits the receiving time information and the TII to the location calculating server. The location calculating server calculates the first, second and third distances Dl, D2 and D3 (of FIG. 2) using the receiving time information and the sending time information, and obtains the location of the mobile terminal M through a triangulation method using the location information regarding the first, second and third transmitters Tl, T2 and T3 and the first, second and third distances Dl, D2 and D3. The location calculating server may transmit the location of the mobile terminal M to the mobile terminal M or the service server.

[60] Therefore, the location of the mobile terminal M is determined using the SC in the transmission frame of the DAB signal. Further, the SC is transmitted with a higher transmission power than the FIC/MSC to obtain a more exact location and a wider cell coverage. For example, the DAB signal may be transmitted with a first power Pl during the first and second sections tl and t2 corresponding to the SC and with a second power P2 lower than the first power Pl during the third section t3 corresponding to the FIC/MSC. Referring again to FIG. 3, after the FIC/MSC symbol and the SC symbol are generated in the FIC/MSC symbol generating unit 120 and the SC symbol generating unit 140, respectively, with the second power P2, the second power P2 of the SC symbol is amplified by the first gain Gl of the first gain block 160 to become the first power Pl. (Pl = P2 X G1) Since the first gain Gl is greater than 1, the cell coverage of the SC is greater than the cell coverage of the FIC/MSC. Accordingly, the number of the transmitters of the DAB system utilized for the positioning method is reduced and the cost for modifying the transmitter, i.e., the cost for the first gain block 160 is minimized.

[61] The cell coverage of the DAB signal will be illustrated hereinafter. FIG. 6 is a view showing a cell coverage of DAB signals for a positioning method according to a first embodiment of the present invention.

[62] In FIG. 6, each of first, second and third transmitters Tl, T2 and T3 transmitting a

DAB signal has a respective cell coverage. Since the DAB signal corresponding to the SC has a first power Pl greater than a second power P2 of the DAB signal corresponding to the FIC/MSC, a cell coverage of the DAB signal corresponding to the SC is greater than a cell coverage of the DAB signal corresponding to the FIC/MSC. For example, the DAB signal corresponding to the SC may have a first cell boundary CBl of a first radius Rl and the DAB signal corresponding to the FIC/MSC may have a second cell boundary CB2 of a second radius R2 smaller than the first radius Rl. Since the positioning method according to the first embodiment of the present invention obtains the location of the mobile terminal M using the DAB signal corresponding to the SC, the whole area of the positioning system is covered with the first cell boundaries CB 1 of the first, second and third transmitters Tl, T2 and T3. As a result, increase in the number of the transmitters is prevented and cost for the transmitters is minimized.

[63] The transmitters have different TII in the null symbol of the SC from each other.

Since the transmitters have the same phase reference symbol of the SC as each other, the phase reference symbol is regarded as a known pattern. As a result, the required signal to noise (SfN) ratio for the phase reference symbol is lower than the required S/ N ratio for the null symbol. Accordingly, the phase reference symbol may have the same cell coverage as the null symbol even when the phase reference symbol is transmitted with a lower power than the null symbol. Here, the power amplifier in the transmitter may be used without modification.

[64] FIG. 7 is a transmitter for a positioning system according to a second embodiment of the present invention.

[65] In FIG. 7, the transmitter 200 includes a transmission frame multiplexing unit 210, a fast information channel/main service channel (FIC/MSC) symbol generating unit 220, an orthogonal frequency division multiplex (OFDM) signal generating unit 230, a synchronization channel (SC) symbol generating unit 240, a transmitter identification information (TII) signal generating unit 250, a first gain block 260 and a second gain block 270.

[66] The transmission frame multiplexing unit 210 transmits a data for an FIC and a data for an MSC from exterior to the FIC/MSC symbol generating unit 220. The FIC/MSC symbol generating unit 220 generates an FIC/MSC symbol corresponding to the data for the FIC and the MSC, and transmits the FIC/MSC symbol to the OFDM signal generating unit 230. The SC symbol generating unit 240 generates an SC symbol. The power of the SC symbol is amplified by a first gain Gl through the first gain block 260 and the amplified SC symbol is transmitted to the OFDM signal generating unit 230.

[67] The OFDM signal generating unit 230 generates an OFDM signal using the FIC/

MSC symbol and the SC symbol. The TII signal generating unit 250 generates a TII signal including information for identification of the transmitter and synthesizes the TII signal and the OFDM signal such that the TII signal is inserted into a null symbol of the SC in the transmission frame of the OFDM signal, thereby outputting a DAB signal. Here, the power of the SC symbol corresponding to the TII signal is amplified by a second gain G2 through the second gain block 270.

[68] Accordingly, since the FIC/MSC symbol and the SC symbol are independently generated and supplied to the OFDM signal generating unit 230, the powers of the FIC/MSC symbol and the SC symbol are independently adjusted. For example, the first gain block 260 may adjust the power of the SC symbol separately from the power of the FIC/MSC symbol so that the SC symbol can have a different power from the FIC/MSC symbol. In addition, the powers of the null symbol and the phase reference symbol of the SC are independently adjusted. For example, the second gain block 270 may adjust the power of the null symbol separately from the power of the phase reference symbol so that the null symbol can have a different power from the phase reference symbol. As a result, the SC of the OFDM signal may have a cell boundary greater than the FIC/MSC of the OFDM signal and a wider cell coverage may be obtained with a smaller number of transmitters in the positioning system. Further, since the power of the phase reference symbol is smaller than the power of the null symbol, the power consumption of the positioning system is reduced.

[69] FIG. 8 is a view showing a transmission power of a DAB signal for a positioning method according to a second embodiment of the present invention. Since the DAB signal of the second embodiment has the same transmission frame as the DAB signal of the first embodiment in FIG. 4, the transmission frame of the DAB signal will be illustrated with reference to FIG. 4.

[70] In FIGs. 4 and 8, the transmission frame of the DAB signal includes an SC, an FIC and an MSC, and the SC includes a null symbol and a phase reference symbol. The null symbol and the phase reference symbol of the SC have a first section tl and a second section t2, respectively, as a duration and the FIC/MSC has a third section t3 as a duration.

[71] The location of a mobile terminal M is determined using the SC in the transmission frame of the DAB signal. Further, the SC is transmitted with a higher transmission power than the FIC/MSC to obtain a more exact location and a wider cell coverage. Specifically, since the phase reference symbol of the SC is a known pattern, the phase reference symbol is transmitted with a lower transmission power than the null symbol. For example, the DAB signal may be transmitted with a first power Pl during the first section tl corresponding to the null symbol of the SC and may be transmitted with a second power P2 lower than the first power Pl during the third section t2 corresponding to the FIC/MSC. In addition, the DAB signal may be transmitted with a third power P3 lower than the first power Pl and higher than the second power P2 during the third section t3 corresponding to the phase reference symbol of the SC. Accordingly, the power consumption of the positioning system of the second embodiment is further reduced.

[72] Referring again to FIG. 7, after the FIC/MSC symbol and the SC symbol are generated in the FIC/MSC symbol generating unit 220 and the SC symbol generating unit 240, respectively, with the second power P2, the second power P2 of the SC symbol is amplified by the first gain Gl of the first gain block 260 to become the third power P3. (P3 = P2 X Gl) Since the first gain Gl is greater than 1, the cell coverage of the SC is greater than the cell coverage of the FIC/MSC. Accordingly, the number of the transmitters of the DAB system utilized for the positioning method is reduced and the cost for modifying the transmitter, i.e., the cost for the first gain block 260 is minimized.

[73] Here, the first gain Gl is an optimized value based on the fact that phase reference symbol is a known pattern. Accordingly, the first gain Gl of the second embodiment may be smaller than the first gain of the first embodiment, and the cell coverage that is the same as the cell coverage of the first embodiment may be obtained with a reduced transmission power (Pl -> P3). As a result, a power amplifier in the transmitter of the DAB system is used for the positioning system without replacement, and the power consumption is further improved.

[74] The third power P3 of the SC symbol is amplified by the second gain G2 of the second gain block 270 to become the second power P2. (Pl = P3 X G2 = P2 X Gl X G2) The second gain G2 is greater than 1, and the multiplication of the first and second gains Gl and G2 of the second embodiment may be the same as the first gain Gl of the first embodiment.

[75] In the positioning method of the first and second embodiment, although the TII is added to the null symbol of the SC, the exact location information of the transmitters is stored at the location calculating server. Accordingly, the mobile terminal M transmits the receiving time information of the DAB signal and the TII of the transmitter to the location calculating server so as to calculate the location thereof, and the mobile terminal M does not obtain the location thereof. In a positioning method according to a third embodiment of the present invention, the TII of a given transmitter is added to the SC of the DAB signal from the given transmitter, and the location information of the given transmitter and adjacent transmitters is added to the FIC/MSC of the DAB signal from the given transmitter. In addition, the TII of the adjacent transmitters is added to the FIC/MSC of the DAB signal of the given transmitter. Accordingly, the mobile terminal M may have an autonomous positioning function such that the mobile terminal M calculate the location thereof using the location information of the given transmitter and the adjacent transmitters and distances from the adjacent transmitters. Furthermore, since the mobile terminal M already has the TII of the adjacent transmitters in the FIC/MSC of the DAB signal, the TII of the given transmitter in the SC of the DAB signal becomes a known pattern and the S/N ratio of the null symbol is improved. As a result, the transmission power of the null symbol of the SC is reduced without reduction in a cell coverage and power consumption is further improved.

[76] FIG. 9 is a view showing a cell coverage of DAB signals for a positioning method according to a third embodiment of the present invention.

[77] In FIG. 6, each of first, second and third transmitters Tl, T2 and T3 transmitting first, second and third DAB signals, respectively, has a respective cell coverage. Since each DAB signal corresponding to the SC has a first power Pl greater than a second power P2 of each DAB signal corresponding to the FIC/MSC, the cell coverage of each DAB signal corresponding to the SC is greater than the cell coverage of each DAB signal corresponding to the FIC/MSC. For example, each DAB signal corresponding to the SC may have a first cell boundary CBl of a first radius Rl and each DAB signal corresponding to the FIC/MSC may have a second cell boundary CB2 of a second radius R2 smaller than the first radius Rl.

[78] When a mobile terminal M is disposed inside the first and second cell boundaries

CBl and CB2 of the first transmitter Tl and outside the second cell boundary CB2 of each of the second and third transmitters T2 and T3, the mobile terminal M receives the first DAB signal corresponding to the SC and the FIC/MSC and the second and third DAB signals corresponding to the SC. Further, the mobile terminal M does not receive the second and third DAB signals corresponding to the FIC/MSC. However, since the location information of the first transmitter Tl and the location information and the TII of the second and third transmitters T2 and T3 are added to the FIC/MSC of the first DAB signal from the first transmitter Tl, the mobile terminal M obtains the location information and TII of the first, second and third transmitters Tl, T2 and T3. Since the whole area of the positioning system is covered with the second cell boundaries CB2 of the first, second and third transmitters Tl, T2 and T3, the same result is obtained wherever the mobile terminal M is disposed.

[79] Accordingly, the mobile terminal M have a function of an autonomous positioning such that the mobile terminal M recognizes the location thereof through a triangulation method using the distances from the first, second and third transmitters Tl, T2 and T3 calculated by using the SC of the first, second and third DAB signals and the location information of the first, second and third transmitters Tl, T2 and T3 obtained from the FIC/MSC of the first DAB signal. In addition, since the TII of the second and third transmitters T2 and T3 is obtained from the FIC/MSC of the first DAB signal, the TII in the null symbol of the SC of the second and third DAB signals becomes a known pattern. As a result, the required S/N ratio for the null symbol of the SC of the second and third DAB signals is improved and the transmission power of the null symbol of the SC of the second and third DAB signals is reduced without reduction in a cell coverage.

[80] FIG. 10 is a view showing a transmission power of a DAB signal for a positioning method according to a third embodiment of the present invention. Since the DAB signal of the third embodiment has the same transmission frame as the DAB signal of the first and second embodiments, the transmission frame of the DAB signal will be illustrated with reference to FIG. 4.

[81] In FIGs. 4 and 10, the transmission frame of the DAB signal includes an SC, an FIC and an MSC, and the SC includes a null symbol and a phase reference symbol. The null symbol and the phase reference symbol of the SC have a first section tl and a second section t2, respectively, as a duration and the FIC/MSC has a third section t3 as a duration.

[82] The location of a mobile terminal M is determined using the SC in the transmission frame of the DAB signal. Further, the SC is transmitted with a higher transmission power than the FIC/MSC to obtain a more exact location and a wider cell coverage. Specifically, since the null symbol as well as the phase reference symbol of the SC is a known pattern, the null symbol and the phase reference symbol of the third embodiment is transmitted with a lower transmission power as compared with the second embodiment. For example, the DAB signal may be transmitted with a second power P2 during the third section t3 corresponding to the FIC/MSC and may be transmitted with a third power P3 higher than the second power P2 during the second section t2 corresponding to the phase reference symbol of the SC. In addition, the DAB signal may be transmitted with a fourth power P4 higher than the second power P2 during the first section tl corresponding to the null symbol of the SC. For example, while the DAB signal corresponding to the null symbol of the SC is transmitted with the first power Pl (of FIG. 8) in the second embodiment, the DAB signal corresponding to the null symbol of the SC is transmitted with the fourth power P4 lower than the first power Pl in the third embodiment. Accordingly, the power consumption of the positioning system of the third embodiment is further reduced. Although the fourth power P4 for the null symbol is higher than the third power P3 for the phase reference symbol in FIG. 10, the fourth power P4 for the null symbol may be equal to or lower than the third power P3 for the phase reference symbol in another embodiment.

[83] Since the transmitter of the third embodiment has the same structure as the transmitter of the second embodiment, the operation of the transmitter for a positioning method according to the third embodiment of the present invention may be illustrated with reference to FIG. 7. After the FIC/MSC symbol and the SC symbol are generated in the FIC/MSC symbol generating unit 220 and the SC symbol generating unit 240, respectively, with the second power P2, the second power P2 of the SC symbol is amplified by the first gain Gl of the first gain block 260 to become the third power P3. (P3 = P2 X Gl) Since the first gain Gl is greater than 1, the cell coverage of the SC is greater than the cell coverage of the FIC/MSC. Accordingly, the number of the transmitters of the DAB system utilized for the positioning method is reduced and the cost for modifying the transmitter, i.e., the cost for the first gain block 260 is minimized.

[84] Here, the first gain Gl is an optimized value based on the fact that phase reference symbol is a known pattern. Accordingly, the first gain Gl of the third embodiment may be smaller than the first gain of the first embodiment, and the cell coverage that is the same as the cell coverage of the first embodiment may be obtained with a reduced transmission power (Pl -> P3). As a result, a power amplifier in the transmitter of the DAB system is used for the positioning system without replacement, and the power consumption is further improved.

[85] The third power P3 for the SC symbol is amplified by the second gain G2 of the second gain block 270 to become the fourth power P4 for the null symbol. (P4 = P3 X G2 = P2 X Gl X G2) The second gain G2 may be determined to have a range where the fourth power P4 is equal to or greater than the second power P2, i.e., the multiplication of the first and second gains Gl and G2 is equal to or greater than 1 (Gl X G2 = 1). Since the cell coverage that is the same as the cell coverage of the second embodiment is obtained with a reduced transmission power (Pl -> P4), a power amplifier in the transmitter of the DAB system is used for the positioning system without replacement and the power consumption is further improved.

[86] In another embodiment of the present invention, a pseudo random noise (PRN) code added to the SC of the DAB signal may be used for calculating the distances from the transmitters. FIG. 11 is a view showing a transmission frame of a DAB signal for a positioning method according to a fourth embodiment of the present invention.

[87] In FIG. 11 , a TII and a PRN code are added to a null symbol of an SC of a DAB signal. Since the TII has a very low bit density according to the purpose of discriminating the transmitters, the TII includes several pulses that look like delta functions when viewed by a spectrum analyzer. Accordingly, the PRN code is discriminated from the TII when the transmission power is properly adjusted and replacement of a power amplifier in the transmitter of the DAB system is not required. For example, the DAB signal may have a bandwidth of about 1.536 MHz and the PRN code of about 1.536 MHz may have a spreading gain of about 61.86 dB. Accordingly, an energy density (per frequency) of the PRN code is sufficiently low and the TII in the null symbol of the SC of the DAB is not lost by the PRN code. In addition, since the TII has the very low density, a noise floor due to carriers for the TII does not interfere with a correlation of the PRN code when de-spreading. Although not shown in FIG. 11, the PRN code may be added to an FIC/MSC of the DAB signal to be used for calculating distances from the transmitters.

[88] FIG. 12 is a view showing a transmitter for a positioning system according to a fourth embodiment of the present invention.

[89] In FIG. 12, the transmitter 300 includes a transmission frame multiplexing unit 310, a fast information channel/main service channel (FIC/MSC) symbol generating unit 320, an orthogonal frequency division multiplex (OFDM) signal generating unit 330, a synchronization channel (SC) symbol generating unit 340, a transmitter identification information (TII) signal generating unit 350, a PRN code generating unit 380 and a third gain block 390.

[90] The transmission frame multiplexing unit 310 transmits a data for an FIC and a data for an MSC from exterior to the FIC/MSC symbol generating unit 320. The FIC/MSC symbol generating unit 320 generates an FIC/MSC symbol corresponding to the data for the FIC and the MSC, and transmits the FIC/MSC symbol to the OFDM signal generating unit 330. The SC symbol generating unit 340 generates an SC symbol and transmits the SC symbol to the OFDM signal generating unit 330. The OFDM signal generating unit 330 generates an OFDM signal using the FIC/MSC symbol and the SC symbol. The TII signal generating unit 350 generates a TII signal including information for identification of the transmitter and synthesizes the TII signal and the OFDM signal such that the TII signal is inserted into a null symbol of the SC in the transmission frame of the OFDM signal, thereby outputting a DAB signal.

[91] The PRN code generating unit 380 generates a PRN code and the power of the PRN code is amplified by a third gain through the third gain block 390. The amplified PRN code is added to the null symbol of the SC such that the PRN code overlaps the TIL The third gain may be determined according to simulation and experiment within a limitation that an efficiency of the DAB system is not degraded. For example, the PRN code may have a power lower than the SC, the FIC and the MIC.

[92] The positioning method using the PRN code according to the fourth embodiment may be applied to the positioning method using the SC of the increased power according to the first to third embodiments, where the transmitter includes the first, second and third gain blocks.

[93] The PRN code may have two types: a first type where the transmitters use PRN codes different from each other; and a second type where the transmitters use the same PRN code with a different phase offset. The first type PRN code, which is used in a GPS system, may include golden PRN codes where all the PRN codes of the transmitters have orthogonality. When the first type PRN code is applied to the positioning method according to the third embodiment, the PRN codes of the adjacent transmitters may be added to the FIC/MSC of the DAB signal for a prompt positioning. The second type PRN code, which is used in a code division multiple access (CDMA) system, may have orthogonality due to the different phase offset and a PRN phase distance is required. When the second type PRN code is applied to the positioning method according to the third embodiment, information on a PRN phase distance from the absolute time of the adjacent transmitters may be added to the FIC/ MSC of the DAB signal for a prompt positioning.

[94] When the mobile terminal is disposed close to a given transmitter, following problems may occur. For example, when the mobile terminal is near to the first transmitter and is far from the second and third transmitters, the first PRN code from the first transmitter may have a higher power than the second and third PRN codes from the second and third transmitters. If the first, second and third PRN codes have a perfect orthogonality, recognition of the first, second and third PRN codes is not interfered by the difference in power. However, since the first, second and third PRN codes do not have the perfect orthogonality in a real situation, the first PRN code having a higher power functions as a noise in recognition of the second and third PRN codes having a smaller power. Accordingly, when the mobile terminal is near to the first transmitter, it is hard to recognize the second and third PRN codes from the second and third transmitters due to the first PRN code from the first transmitter.

[95] In addition, the mobile terminal includes a plurality of radio frequency (RF) devices such as an amplifier for wireless communication. When an input signal has a relatively high power, the RF device may have a non-linear characteristic, which causes an abnormal output, due to saturation of signal. For example, when the mobile terminal is near to the first transmitter and is far from the second and third transmitters, the first PRN code having a higher power may render the corresponding RF device of the mobile terminal saturated and the saturated RF device may have an abnormal output in response to the second and third PRN codes having a smaller power.

[96] Furthermore, the mobile terminal includes an automatic gain control (AGC) loop so that a uniform signal can be inputted to an analog to digital converter (ADC) regardless of size of an input signal. For example, when a signal is transmitted to the mobile terminal, the AGC loop may reduce a gain for the signal having a relatively high power and may increase the gain for the signal having a relatively low power. Accordingly, when the mobile terminal is near to the first transmitter and is far from the second and third transmitters, the AGC loop of the mobile terminal reduces the gain for the first PRN code having a higher power and the corresponding noise figure increases. As a result, it becomes harder to recognize the second and third PRN codes from the second and third transmitters due to the first PRN code from the first transmitter.

[97] Moreover, the mobile terminal includes the ADC for converting an analog signal to a digital signal. When the input signals of the ADC have different powers, the input signals have difference in resolution and the difference in resolution causes errors in outputs of the ADC. Accordingly, when the mobile terminal is near to the first transmitter and is far from the second and third transmitters, the first PRN code having a higher power is inputted to the ADC of the mobile terminal together with the second and third PRN codes having a lower power, and the ADC may have erroneous outputs. As a result, the erroneous outputs may function as obstacles in recognition of the second and third PRN codes from the second and third transmitters.

[98] To solve the above problems, in a positioning method according to a fifth embodiment of the present invention, the PRN code is not added to the DAB signal of each transmission frame. Instead, the PRN code is added to the DAB signal of the corresponding transmission frames and is not added to the DAB signal of the other transmission frames. In addition, the PRN code is sequentially added to the DAB signals according to elapse of transmission frames.

[99] FIG. 13 is a view showing a cell coverage of DAB signals for a positioning method according to a fifth embodiment of the present invention, and FIG. 14 is a view showing transmission frames of DAB signals for a positioning method according to a fifth embodiment of the present invention.

[100] In FIGs. 13 and 14, first, second and the third DAB signals DAB 1, DAB2 and DAB 3 are transmitted from first, second and third transmitters Tl, T2 and T3, respectively, to a mobile terminal M. Each of the first, second and third DAB signals DAB 1, DAB2 and DAB3 includes a series of transmission frames, e.g., first, second and third transmission frames of about 96msec. First, second and third PRN codes PRNl, PRN2 and PRN3 that are different from and orthogonal to one another are added to a null symbol in an SC of the transmission frames of the first, second and third DAB signals DABl, DAB2 and DAB 3, respectively. Here, the first, second and third PRN codes PRNl, PRN2 and PRN3 are added to the null symbols of the first transmission frame of the first DAB signal DABl, the second transmission frame of the second DAB signal DAB2 and the third transmission frame of the third DAB signal DAB3, respectively. In addition, the second and third transmission frames of the first DAB signal DAB 1, the third and first transmission frames of the second DAB signal DAB2, and the first and second transmission frames of the third DAB signal DAB 3 do not include any PRN code. Accordingly, the first, second and third transmitters Tl, T2 and T3 does not transmit the first, second and third PRN codes PRNl, PRN2 and PRN3 at the same time but sequentially transmit the first, second and third PRN codes PRNl, PRN2 and PRN3 during predetermined time periods corresponding to the null symbol. As a result, the problems caused by simultaneous transmission of the plurality of PRN codes are prevented.

[101] For example, the first transmitter Tl may transmit the first PRN code PRNl during a first time period TPl of about 1.297msec corresponding to the null symbol of the SC of the first frame, the second transmitter T2 may transmit the second PRN code PRN2 during a second time period TP2 of about 1.297msec corresponding to the null symbol of the SC of the second frame, and the third transmitter T3 may transmit the third PRN code during a third PRN3 of about 1.297msec corresponding to the null symbol of the SC of the third frame. Accordingly, the first, second and third PRN codes PRNl, PRN2 and PRN3 are not transmitted at the same time but are sequentially transmitted during different time periods.

[102] In other words, the first PRN code PRNl is transmitted during the first time period TPl corresponding to the null symbol of the SC in the first frame of the first DAB signal DABl, the second PRN code PRN2 is transmitted during the second time period TP2 corresponding to the null symbol of the SC in the second frame of the second DAB signal DAB2, and the third PRN code PRN3 is transmitted during the third time period TP3 corresponding to the null symbol of the SC in the third frame of the third DAB signal DAB3. Therefore, the PRN code is added to the null symbol of the SC in one of the corresponding transmission frames of the first, second and third DAB signals DABl, DAB2 and DAB3.

[103] Although the number of the transmitters is 3 in the fifth embodiment of FIGs. 13 and 14, the number of the transmitters may be varied in another embodiment, where the plurality of PRN codes may be sequentially transmitted during different time periods and the problems caused by simultaneous transmission of the plurality of PRN codes are prevented.

[104] In another embodiment, at least one of the plurality of DAB signals may not include the PRN codes, and the PRN codes may be added to the others of the plurality of DAB signals. For example, first and second PRN codes may be added to first and second DAB signals, respectively, in a first transmission frame, second and third PRN codes may be added to second and third DAB signals, respectively, in a second transmission frame, and third and first PRN codes may be added to third and first DAB signals, respectively, in a third transmission frame. Accordingly, the first and second PRN codes are transmitted during a first time period of the first transmission frame, the second and third PRN codes are transmitted during a second time period of the second transmission frame, and the third and first PRN codes are transmitted during a third time period of the third transmission frame. The third, first and second PRN code are not transmitted in the first, second and third transmission frames, respectively. In the positioning system according to this embodiment, when the mobile terminal is near to one transmitter and far from the other transmitters, there exists at least one transmission frame where the PRN code is not added to the DAB signal from the one transmitter. For example, when the mobile terminal is near to the first transmitter and far from the second and third transmitters, the first DAB signal does not include the first PRN code in the second transmission frame. Since the second and third PRN codes of the second and third DAB signals have a lower power, the mobile terminal recognizes the second and third PRN codes without interference by the first PRN code having a higher power in the second transmission frame.

[105] As referring again to FIGs. 13 and 14, the location of the mobile terminal may be calculated by using the exact location information of the transmitters and the distances from the transmitters. The distance from the each transmitter is calculated by multiplying the elapsed time by the light velocity, and the elapsed time is obtained from the sending time of the PRN code at each transmitter, the receiving time of the PRN code at the mobile terminal and the offset time of the mobile terminal. Since the offset time of the mobile terminal have a time-dependency, the different offset times are used for calculating the distance when the PRN codes are sequentially transmitted in the series of transmission frames. The different offset times will be illustrated hereinafter.

[106] For example, the first PRN code PRNl is sent from the first transmitter Tl at a first sending time t_τl, the second PRN code PRN2 is sent from the second transmitter T2 at a second sending time t_τ2, and the third PRN code PRN3 is sent from the third transmitter T3 at a third sending time t_τ3. In addition, the mobile terminal M receives the first, second and third PRN codes PRNl, PRN2 and PRN3 at first, second and third receiving times t_M1, t_M2 and t_M3, respectively. The first, second and third PRN codes PRNl, PRN2 and PRN3 are transmitted to the mobile terminal during first, second and third elapsed times tl, t2 and t3, respectively. When the mobile terminal M has first, second and third offset times t_offsetl, t_offset2 and t_offset3, in the first, second and third transmission frames, respectively, each of the first, second and third offset times t_offsetl, t_Offset2 and toffseo may be expressed by sum of an average offset time (AOT) and each of first, second and third drift times W₁, Wa and Wt3 (Wseti = AOT + Wti, t_off_set2 = AOT + Wt2, toffceo = AOT + Wo)- Further, the sending times, the receiving times, the elapsed times and the drift times may satisfy the following equations.

[107] t_Mi = t_Ti + tl + AOT + Wti equation (1) [108] t_M2 = t_τ2 + t2 + AOT + t_dπft2 equation (2)

[109] t_M3 = tχ₃ + t3 + AOT + t_dπft3 equation (3)

[110] The first, second and third sending times t_τl, t_τ2 and t_τ3 are obtained by measurement of clocks in the first, second and third transmitters Tl, T2 and T3, respectively, and the first, second and third receiving times t_M1, t_M2 and t_M3 are obtained by measurement of a clock in the mobile terminal M. Since the average offset time AOT of the mobile terminal is a constant value independent of transmission frames, the average offset time AOT is obtained by measurement. When the first, second and third drift times t d_πfti, t_drift2 and t_dπft3 are a constant value independent of transmission frames or a slow varying function of time, the first, second and third drift times t_dπftl, t_dnft2 and t_dπft3 are obtained by measurement. Accordingly, the first, second and third elapsed times tl, t2 and t3 are obtained from the equations (1), (2) and (3), and the first, second and third distances from the first, second and third transmitters Tl, T2 and T3 to the mobile terminal M are calculated by multiplying the first, second and third elapsed times tl, t2 and t3 by light velocity. Finally, the mobile terminal M calculates the location thereof through a triangulation method using the first, second and third distances and the location information of the first, second and third transmitters Tl, T2 and T3.

[I l l] If the constant term, i.e., the average offset time AOT is deleted from the equations (1), (2) and (3), the first, second and third elapsed times tl, t2 and t3 may be obtained easily. By subtracting the equation (1) from the equation (2), subtracting the equation (2) from the equation (3), and subtracting the equation (3) from the equation (1), the following equations are obtained.

[112] t_M21 = t_M2 - t_M1 = (t_T2 - t_τl) + (t2 - tl) + (W₂ - Wi) equation (4)

[113] t_M32 = t_M3 - t_M3 = (t_τ3 - t_τ2) + (t3 - 12) + (Wt3 - Wm) equation (5)

[114] t_M13 = t_M1 - t_M3 = (tχi - t_τ3) + (tl - 13) + (Wi - Wa₃) equation (6)

[115] , where first, second and third receiving time differences t_M21, t_M32 and t_M13 are obtained by measuring the first, second and third receiving times t_M1, t_M2 and t_M3 in the mobile terminal M.

[116] Since the first, second and third transmitters Tl, T2 and T3 are synchronized with an absolute time such as a GPS time, the difference between sending times is equal to the difference between transmission frames, i.e., about 96msec. Accordingly, the differences between the second and first sending times t_τ2 and t_τl, between the third and second sending times t_τ3 and t_τ2, and between the first and third sending times t_τl and t τ₃ become a constant of about 96msec. (t_τ2 - t_Ti = t_τ3 - t_τ2 = t_Ti - t_τ3 = 96msec)

[117] In addition, if the first, second and third drift times Wti, Wm and t_dnft3 are equal to one another without time-dependency, the drift time differences become zero and the equations (4), (5) and (6) may be expressed as follows.

[118] t_M2i = 96msec + (t2 - tl) equation (7) [119] t_M32 = 96msec + (t3 - 12) equation (8)

[120] t_M13 = 96msec + (tl - 13) equation (9)

[121] Accordingly, the first, second and third elapsed times tl, t2 and t3 of the first, second and third PRN codes PRNl, PRN2 and PRN3 are obtained by solving the simultaneous equations (7), (8) and (9).

[122] In a real circumstance, however, the first, second and third drift times t_dπftl, t_dnft2 and t d_πft3 corresponding to the first, second and third time periods TPl, TP2 and TP3 depend on time, and the last term of each of the equations (4), (5) and (6) is not deleted. Since the drift time difference of the first, second and third drift times t_dπftl, t_dnft2 and t_dnft3 in a real circumstance has a random Gaussian distribution, a cumulative average before measurement is obtained and used for the drift time of the equations (4), (5) and (6). For example, the DAB signal corresponding to 10 transmission frames, i.e., 10 time periods is transmitted for 1 second before starting the positioning method, and there exist 10 drift time differences in the 10 corresponding time periods. Accordingly, a cumulative average of drift time difference is obtained by averaging the 10 drift time differences. The cumulative average of drift time difference is used for the equations (4), (5) and (6), and the first, second and third elapsed times tl, t2 and t3 of the first, second and third PRN codes PRNl, PRN2 and PRN3 are obtained by solving the simultaneous equations (4), (5) and (6).

[123] Consequently, the mobile terminal M calculates the first, second and third distances from the first, second and third transmitters Tl, T2 and T3 by multiplying the first, second and third elapsed times tl, t2 and t3 by light velocity, and obtains the location thereof through a triangulation method using the first, second and third distances and the location information of the first, second and third transmitters Tl, T2 and T3.

[124] FIG. 15 is a view showing a mobile terminal for a positioning method according to a fifth embodiment of the present invention.

[125] In FIG. 15, a mobile terminal M includes an antenna 410, a first amplifier 420, a broadcasting signal processing unit 430 and a location calculating unit 440. The broadcasting signal processing unit 430 analyzes a DAB signal transmitted to the mobile terminal M and provides a broadcasting to a user, the location calculating unit 440 analyzes a PRN code transmitted to the mobile terminal M and provides a location information of the mobile terminal M to the user. The broadcasting signal processing unit 430 includes a first local oscillator 431, a second amplifier 432, a first analog to digital converter (ADC) 433, an orthogonal frequency division multiplex (OFDM) demodulator 434 and a DAB signal processor 435. In addition, the location calculating unit 440 includes a second local oscillator 441, a third amplifier 442, a second ADC 443, a PRN demodulator 44 and a PRN code processor 445.

[126] The first amplifier 420 may include a low noise amplifier (LNA) and amplify a transmitted signal with noise eliminated. The second and third amplifiers 432 and 442 may include a variable gain amplifier (VGA) and amplify input signals with a variable gain such that output signals inputted to the first and second ADCs 433 and 443 have a constant power or a constant voltage. The first and second local oscillators 431 and 441 may include a voltage controlled oscillator (VOC) or a voltage controlled temperature-compensated crystal oscillator (VCTCXO) and generate a internal reference frequency mixed to a frequency of an input signal.

[127] Each of the broadcasting processing unit 430 and the location calculating unit 440 operates with an automatic gain control (AGC) loop, an automatic frequency control (AFC) loop and a time tracking loop.

[128] The AGC loop is used for outputting a signal having a uniform optimum power (or voltage) to the first and second ADCs 433 and 443. For example, when the DAB signal and the PRN code that are inputted to the broadcasting signal processing unit 430 and the location calculating unit 440, respectively, have a lower power, the AGC loop may multiply the DAB signal and the PRN code by a greater gain and output the multiplied DAB signal and the multiplied PRN code to the first and second ADCs 433 and 443. In addition, when the DAB signal and the PRN code have a higher power, the AGC loop may multiply the DAB signal and the PRN code by a smaller gain and output the multiplied DAB signal and the multiplied PRN code to the first and second ADCs 433 and 443. Accordingly, the AGC loop automatically adjusts the gain to output a signal having a uniform optimum power (or voltage) to the first and second ADCs 433 and 443 regardless of the power of the inputted signal.

[129] The AFC loop is used for complementing the accuracy of the first and second local oscillators 431 and 441 in the mobile terminal M. When the mobile terminal M receives the DAB signal and the PRN code in motion, the frequencies of the DAB signal and the PRN code may be changed due to Doppler Effect and the accuracy of the first and second local oscillators 431 and 441 in the mobile terminal M is degraded. The AFC loop adjusts the frequency of the mobile terminal M to correspond to the changed frequency of the DAB signal and the PRN code, thereby complementing the accuracy of the first and second local oscillators 431 and 441.

[130] Further, the time tracking loop is used for synchronizing the DAB signal and the

PRN code continuously. For example, although the frequency accuracy is obtained in a CDMA system using a single PRN code, the signal can not be demodulated when the time synchronization is not obtained. In addition, the time synchronization is degraded according to elapse of time even after the time synchronization has obtained. Accordingly, the time tracking loop continuously synchronizes the DAB signal and the PRN code so that the obstacle in demodulation due to the inaccuracy of the time synchronization can be prevented. [131] In the positioning method according to the fifth embodiment of the present invention, since the PRN code is added to the null symbol of about 1.297msec of the SC in the transmission frame of about 96msec of the DAB signal, the AGC loop, the AFC loop and the time tracking loop operate for only about 1.297msec of about 96msec on the PRN code. As a result, the AGC loop, the AFC loop and the time tracking loop may operate incompletely. Further, since the first, second and third DAB signals from the first, second and third transmitters Tl, T2 and T3 are measured every transmission frame, errors in measurement of the PRN code are caused by the incomplete operation of the AGC loop, the AFC loop and the time tracking loop.

[132] A positioning method where the incomplete operation of the AGC loop is improved is suggested in a sixth embodiment of the present invention, and a positioning method where the incomplete operation of the AFC loop and the time tracking loop is improved is suggested in seventh, eighth and ninth embodiments of the present invention.

[133] FIG. 16 is a view showing an AGC loop of a mobile terminal for a positioning method according to a sixth embodiment of the present invention. FIG. 16 shows a location calculating unit of a mobile terminal according to the sixth embodiment, and a broadcasting signal processing unit of the mobile terminal according to the sixth embodiment may be the same as that according to the fifth embodiment in FIG. 15.

[134] In FIG. 16, a location calculating unit of a mobile terminal includes a gain block 456 providing a gain block value and a jump block 452 for normal operation of an AGC loop when the mobile terminal is near to a given transmitter. For example, when the mobile terminal is near to the first transmitter and far from the second and third transmitters, the first DAB signal and the first PRN code are transmitted with a higher power, and the second and third DAB signals and the second and third PRN codes are transmitted with a lower power. When the location calculating unit of the mobile terminal processes the first PRN code during the first transmission frame, the AGC loop adjusts the gain to be a smaller value such that the power of the first PRN code is multiplied by a smaller gain and the first PRN code having an optimum power (or voltage) by the smaller gain is inputted to the second ADC. In the second transmission frame, since the second PRN code has the lower power, the AGC loop adjusts the gain to be a greater value such that the power of the first PRN code is multiplied by a greater gain and the second PRN code having an optimum power (or voltage) by the greater gain is inputted to the second ADC. Accordingly, the gain is abruptly changed between the first and second transmission frames. In addition, since the AGC loop of the location calculating unit adjusts the gain only for about 1.297msec in the transmission frame of about 96msec, the gain is not sufficiently adjusted in the second transmission frame and the AGC loop abnormally operates. [135] The jump block 452 promptly provides the jump value for determining the gain for the optimum power by predicting the second PRN code from the remote transmitter on the basis of the first PRN code from the adjacent transmitter. Accordingly, the gain block 456 provides the gain block value to change a converted value S outputted from the second ADC 443 to a target value A, and the jump block 452 provides a jump value to jump the gain to a proximity value by predicting the power of inputted PRN code.

[136] Referring again to FIGs. 15 and 16, when the mobile terminal is near to the first transmitter and far from the second and third transmitters, operation of the AGC loop in the first and second transmission frames will be illustrated hereinafter.

[137] In a loop of the first transmission frame, the first PRN code having a higher power is inputted to the third amplifier 442 and the amplified first PRN code is converted to have a digital type by the second ADC 443. The converted first PRN code has the converted value S. The target value A is subtracted from the converted value S, and the difference (S - A) between the converted value S and the target value A is multiplied by the gain block value provided by the gain block 456. The jump value provided by the jump block 452 is added to the multiplication result of the gain block value and the difference (S - A), and the summation result of the jump value and the multiplication result is inputted to the third amplifier 442. The third amplifier 442 amplifies the next input signal using the summation result as a new gain. The gain for the optimum power of the amplified first PRN code in the first transmission frame is determined by repeating the above-mentioned loop. Since the power of the first PRN code is not changed during the first transmission frame, the jump value provided by the jump block 452 has a relatively small value and the converted value S is gradually changed to the target value A by the AGC loop. The gain block value provided by the gain block 456 is a constant for determining a loop time of the AGC loop.

[138] Next, in a loop of the second transmission frame, the second PRN signal having a lower power is inputted to the third amplifier 442 and the amplified second PRN code is converted to have a digital type by the second ADC 443. The converted second PRN code has the converted value S. The target value A is subtracted from the converted value S, and the difference (S - A) between the converted value S and the target value A is multiplied by the gain block value provided by the gain block 456. The jump block 452 predicts the power of the second PRN code from the power of the first PRN code to determine the corresponding jump value. The jump value provided by the jump block 452 is added to the multiplication result of the gain block value and the difference (S - A), and the summation result of the jump value and the multiplication result is inputted to the third amplifier 442. The third amplifier 442 amplifies the next input signal using the summation result as a new gain. [139] Since the power of the second PRN code is lower than the power of the first PRN code, the initial jump value of the first loop of the second transmission frame has a relatively great value. In addition, since the gain used by the third amplifier 442 for amplifying the second PRN code already has a relatively great value after the first loop, the jump value becomes small. Here, since the third amplifier 442 has a relatively short response time and the second ADC 443 has a relatively wide dynamic range of receivable range of power, the third amplifier 442 and the second ADC 443 of the AGC loop operate normally even when the gain is changed from the smaller value determined through the process for the first PRN code to the greater value determined through the process for the second PRN.

[140] A method of determining the jump value in the second and third transmission frames will be illustrated hereinafter. When the first, second and third PRN codes have first, second and third powers P_PRNi, P_PRN2 and P_PRN3, respectively, a relation of a virtual total power P and the first, second and third powers P_PRNi, P_PRN2 and P_PRN3 may be expressed as follows.

[141] P_PRN2 = P - PpRNi equation (10)

[142] P_PRN3 = P - PpRNi equation (11)

[143] The virtual total power P is determined by an electromagnetic wave environment of the mobile terminal and the transmitters, and can be obtained by measurement in a real system.

[144] According to the equations (10) and (11), when the mobile terminal M is near to the first transmitter, the AGC loop of the mobile terminal may predict the power of the second and third PRN codes from the power of the first PRN code, and may obtain a gain for the second and third PRN codes. In addition, the AGC loop of the mobile terminal determines the difference between the gain of the first transmission frame and the predicted gain of the second transmission frame as the jump value. As a result, the initial gain of the second transmission frame promptly obtained in the AGC loop of the mobile terminal and the AGC loop of the mobile terminal normally operates.

[145] Since a mobile terminal for a positioning method according to one of seventh, eighth and ninth embodiments has similar structure as the mobile terminal according to the fifth embodiment, the seventh, eighth and ninth embodiments will be illustrated with reference to FIG. 15.

[146] The mobile terminal for a positioning method according to a seventh embodiment of the present invention includes a broadcasting signal processing unit and a location calculating unit. The AFC loop and the time tracking loop of the location calculating unit use parameters of the AFC loop and the time tracking loop determined by the OFDM demodulator of the broadcasting signal processing unit. Each of the broadcasting signal processing unit and the location calculating unit of the mobile terminal includes the AFC loop and the time tracking unit. The AFC loop and the time tracking loop of the broadcasting signal processing unit operate on the DAB signal for about 94.703msec corresponding to the transmission frame except the null symbol of the SC, while the AFC loop and the time tracking loop of the location calculating unit operate on the PRN code for about 1.297msec corresponding to the null symbol of the SC. Accordingly, the AFC loop and the time tracking loop of the broadcasting signal processing unit operate more stably than the AFC loop and the time tracking loop of the location calculating unit. In the mobile terminal of the seventh embodiment, since the parameters of he AFC loop and the time tracking loop of the broadcasting signal processing unit are used for the AFC loop and the time tracking loop of the location calculating unit, the AFC loop and the time tracking loop of the location calculating unit are promptly stabilized.

[147] In a positioning method according to an eighth embodiment of the present invention, a mobile terminal is integrated in a cellular phone. The cellular phone includes an AFC loop and a time tracking loop for a wireless communication. Accordingly, when the mobile terminal having a broadcasting function for a DAB signal and a positioning function for a PRN code is integrated in the cellular phone, stable parameters of the AFC loop and the time tracking loop of the cellular phone are used for the AFC loop and the time tracking loop of the location calculating unit, and the AFC loop and the time tracking loop of the location calculating unit are promptly stabilized.

[148] The mobile terminal for a positioning method according to a ninth embodiment of the present invention includes a broadcasting signal processing unit, a location calculating unit including an ADC, and a memory unit. Signal parameters for PRN code such as a frequency and a phase may be measured in the ADC at a predetermined time and may be stored in the memory unit such as a read only memory (RAM). The parameters may be processed through a Fast Fourier Transform (FFT) afterward.

[149] In the AFC loop and the time tracking loop, after the input signal is stabilized in time domain, information on frequency and time is obtained in realtime. In the mobile terminal of the ninth embodiment, information on frequency and time of the converted signal from the ADC is obtained by analyzing the input signal in frequency domain through post-processing. Since the frequency domain and the time domain are equivalently interpreted through the FFT, the frequency domain is substantially the same as the time domain. In addition, since parameters for the frequency domain are obtained by measurement in the time domain, the stabilization time for a loop is not required in the frequency domain. Accordingly, the receiving time of the corresponding PRN code at the mobile terminal is determined by analyzing the frequency or the phase of the converted PRN code in the ADC using information on converting time, and the location of the mobile terminal is obtained through a triangulation method using the distances between the mobile terminal and the transmitters.

[150] While the problems caused by the mobile terminal near to one transmitter and far from the other transmitters are solved by sequentially adding the PRN codes to the DAB signals in the positioning method according to the fifth to ninth embodiments of the present invention, the problems caused by the mobile terminal near to one transmitter and far from the other transmitters are solved by using a GPS signal received from a satellite in a positioning method according to a tenth embodiment of the present invention. In addition, the mobile terminal of the tenth embodiment includes a broadcasting signal processing unit, a location calculating unit and a GPS receiving unit. Since the PRN code is added to the DAB signal every transmission frame, the location of the mobile terminal is determined by using the PRN code when the mobile terminal is not near to a specific transmitter. Further, the location of the mobile terminal is determined by using the GPS signal of the satellite when the mobile terminal is near to a specific transmitter. Accordingly, obstacles due to difference in power of PRN code are overcome and the location of the mobile terminal is always obtained.

[151] It will be apparent to those skilled in the art that various modifications and variations can be made in a positioning method using a digital audio broadcasting and a transmitter for the positioning method of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

[152]

Claims

[1] A positioning method comprising: generating a plurality of digital audio broadcasting (DAB) signals in a plurality of transmitters, each of the plurality of DAB signals including a series of transmission frames and each transmission frame including a synchronization channel (SC), a fast information channel (FIC) and a main service channel

(MSC); transmitting the plurality of DAB signals such that the SC has a first power and each of the FIC and the MSC has a second power lower than the first power; measuring receiving times of the plurality of DAB signals in a mobile terminal; and determining a location of the mobile terminal using the receiving times.

[2] The positioning method according to claim 1, wherein determining the location of the mobile terminal comprises: calculating distances from the mobile terminal to the plurality of transmitters using the receiving times and sending times of the plurality of DAB signals at the plurality of transmitters; and calculating the location of the mobile terminal using the distances and a location information of the plurality of transmitters.

[3] The positioning method according to claim 2, further comprising: transmitting the sending times from the plurality of transmitters to a location calculating server; and transmitting the receiving times from the mobile terminal to the location calculating server, wherein the location calculating server calculates the distances from the mobile terminal to the plurality of transmitters and calculates the location of the mobile terminal through a triangulation method.

[4] The positioning method according to claim 1, wherein the plurality of transmitters include first, second and third transmitters, and the location of the mobile terminal is determined through a triangulation method using locations of the first, second and third transmitters and distances from the first, second and third transmitters to the mobile terminal.

[5] The positioning method according to claim 1, wherein the SC includes a null symbol where a transmitter identification information (TII) of the plurality of transmitters is selectively added and a phase reference symbol which is a reference of an initial phase for the FIC and the MSC, and the plurality of DAB signals has the same phase reference symbol as one another.

[6] The positioning method according to claim 4, wherein the TII and null symbol has the first power and the phase reference symbol has a third power lower than the first power and higher than the second power.

[7] The positioning method according to claim 4, wherein the FIC and the MSC of the DAB signal from one of the plurality of transmitters include the location information and the TII of the others of the plurality of transmitters.

[8] The positioning method according to claim 6, wherein the phase reference symbol has a third power lower than the first power and higher than the second power, and the null symbol has a fourth power lower than the first power and higher than the second power.

[9] A positioning method comprising: generating a plurality of digital audio broadcasting (DAB) signals in a plurality of transmitters, each of the plurality of DAB signals including a series of transmission frames and each transmission frame including a synchronization channel (SC), a fast information channel (FIC) and a main service channel

(MSC); adding a pseudo random noise (PRN) code to at least one of the SC, the FIC and the MSC; transmitting the plurality of DAB signals such that each of the SC, the FIC and the MSC has a first power and the PRN code has a second power; measuring receiving times of the plurality of DAB signals in a mobile terminal; and determining a location of the mobile terminal using the receiving times.

[10] The positioning method according to claim 9, wherein the PRN codes used in the plurality of transmitters includes a first type where the PRN codes are different from one another and a second type where the PRN codes are a same as one another with different phase offsets.

[11] A transmitter for a positioning method, comprising: a transmission frame multiplexing unit receiving a data for a fast information channel (FIC) and a data for a main service channel (MSC); an FIC/MSC symbol generating unit generating a first symbol corresponding to the data for the FIC and the data for the MSC; a synchronization channel (SC) symbol generating unit generating a second symbol corresponding to a data for an SC; a first gain block amplifying a power of the second symbol by a first gain; an orthogonal frequency division multiplex (OFDM) signal generating unit generating an OFDM signal using the first symbol and the second symbol amplified by the first gain; and a transmitter identification information (TII) signal generating unit generating a TII signal and synthesizing the TII signal and the OFDM signal to output a digital audio broadcasting (DAB) signal.

[12] The transmitter according to claim 11, further comprising a second gain block amplifying a power of the TII signal by a second gain.

[13] A transmitter for a positioning method, comprising: a transmission frame multiplexing unit receiving a data for a fast information channel (FIC) and a data for a main service channel (MSC); an FIC/MSC symbol generating unit generating a first symbol corresponding to the data for the FIC and the data for the MSC; a synchronization channel (SC) symbol generating unit generating a second symbol corresponding to a data for an SC; an orthogonal frequency division multiplex (OFDM) signal generating unit generating an OFDM signal using the first symbol and the second symbol; a transmitter identification information (TII) signal generating unit generating a

TII signal and synthesizing the TII signal and the OFDM signal to output a digital audio broadcasting (DAB) signal; a pseudo random noise (PRN) code generating unit generating a PRN code; and a gain block amplifying a power of the PRN code by a gain and adding the PRN code to the DAB signal such that the PRN code overlaps the DAB signal.

[14] A positioning method comprising: generating a plurality of digital audio broadcasting (DAB) signals in a plurality of transmitters, each of the plurality of DAB signals including a series of transmission frames; adding a pseudo random noise (PRN) code to at least one of the series of transmission frames sequentially with respect to the plurality of DAB signal; transmitting the plurality of DAB signals including the PRN code to a mobile terminal; and calculating distances from the mobile terminal to the plurality of transmitters using the PRN code.

[15] The positioning method according to claim 14, wherein the plurality of transmitters include first, second and third transmitters, and the plurality of DAB signals include first, second and third DAB signals, wherein the series of transmission frames include first, second and third transmission frames, and the first, second and third transmission frames of the first, second and third DAB signals correspond to one another, wherein the PRN code includes first, second and third PRN codes that are different from and orthogonal to one another, and wherein the first PRN code is added to the first transmission frame of the first DAB signal, the second PRN code is added to the second transmission frame of the second DAB signal, and the third PRN code is added to the third transmission frame of the third DAB signal.

[16] The positioning method according to claim 15, wherein each of the first, second and third transmission frames includes a synchronization channel (SC), a fast information channel (FIC) and a main service channel (MSC), and the first, second and third PRN codes are added to the SCs of the first, second and third transmission frames, respectively.

[17] The positioning method according to claim 13, wherein calculating the distances comprises calculating an elapsed time using sending times when the PRN code is sent from the plurality of transmitters, receiving times when the mobile terminal receives the PRN code, an average offset time of the mobile terminal, and a drift time of the mobile terminal.

[18] The positioning method according to claim 17, wherein drift time includes a cumulative average before measurement.

[19] The positioning method according to claim 14, further comprising determining a location of the mobile terminal using the distances and a location information of the plurality of transmitters.

[20] The positioning method according to claim 149, wherein the mobile terminal includes a broadcasting signal processing unit processing the plurality of DAB signals and a location calculating unit processing the PRN code.

[21] The positioning method according to claim 20, wherein the location calculating unit processes the PRN code through an automatic gain control (AGC) loop, and wherein the AGC loop comprises: determining a first gain corresponding to a first power of the PRN code; calculating a second power for the next PRN code from the first power; determining a jump value such that the first gain approaches to a second gain corresponding to the second power by the jump value; and adding the first gain and the jump value to use as the second gain.

[22] The positioning method according to claim 21, wherein the second power is calculated by subtracting the first power from a virtual total power that is determined by an electromagnetic wave environment of the mobile terminal and the plurality of transmitters.

[23] The positioning method according to claim 20, wherein the broadcasting signal processing unit and the location calculating unit process the plurality of DAB signals and the PRN code, respectively, through an automatic frequency control (AFC) loop and a time tracking loop, and wherein the AFC loop and the time tracking loop of the location calculating unit operate using parameters of the AFC loop and the time tracking unit of the broadcasting signal processing unit.

[24] The positioning method according to claim 20, wherein the mobile terminal is integrated in a cellular phone, wherein the location calculating unit processes the PRN code through an automatic frequency control (AFC) loop and a time tracking loop, and wherein the AFC loop and the time tracking loop of the location calculating unit operate using parameters of an AFC loop and a time tracking unit of the cellular phone.

[25] The positioning method according to claim 14, wherein the mobile terminal includes a broadcasting signal processing unit processing the plurality of DAB signals, a location calculating unit processing the PRN code, and a memory unit storing a data of one of the broadcasting signal processing unit and the location calculating unit, and the positioning method further comprising: measuring first signal parameters of the PRN code in a time domain and storing the first signal parameters in the memory unit; converting the first signal parameters through Fast Fourier Transform (FFT) to second signal parameters in a frequency domain; and determining a receiving time when the mobile terminal receives the PRN code using the second parameters.

[26] A positioning method comprising: generating a plurality of digital audio broadcasting (DAB) signals in a plurality of transmitters, each of the plurality of DAB signals including a transmission frame; adding a pseudo random noise (PRN) code to the transmission frame; transmitting the plurality of DAB signals including the PRN code to a mobile terminal; transmitting a global positioning system (GPS) signal to the mobile terminal; and calculating distances from the mobile terminal to the plurality of transmitters alternately using the PRN code and the GPS signal.