MXPA01009314A - Method for communicating information - Google Patents

Abstract

The invention relates to communication of information in fixed-length messages in mobile communication systems, particularly in association with positioning methods. In a method according to the invention information is transferred in a fixed-length message such that the payload portion of the message includes content information to define the contents of the payload portion of the message, and in accordance with the content information the payload portion of the message includes information elements defined by the content information.

Description

METHOD TO COMMUNICATE INFORMATION TECHNICAL FIELD OF THE INVENTION The invention relates to the communication of information in mobile communication systems using fixed length messages, particularly in association with positioning methods. In particular, the invention relates to a method according to the preamble of claim 1.

BACKGROUND OF THE INVENTION The positioning information of a mobile station can be used for many purposes: - Call pricing can be based on the position of a mobile station, so calls made from the home area, for example, can be cheaper; - when an emergency call is established from a mobile station, it is possible to determine the position of the mobile station (this feature will be required by the authorities in some countries); REF: 132588 the user of a mobile station may need information about its location for example when traveling, the authorities can use the positioning information to locate a stolen mobile station or to find out the whereabouts of a lost person, for example. Since the determination of the position involves the communication of data in the system, it is necessary that the operator be able to load the localization service according to the use. In addition, the positioning has to be reliable so that the location information can not be falsified by the user, for example, in order to be granted a discount for the home area during the time it is elsewhere. of the home area. In addition, the data may be confidential as it is not necessarily in the interest of the operator to disclose the information related to the system to a third party. The Global Positioning System (GPS) based on the use of signals received from satellites is widely used for positioning purposes. This solution would require a GPS receiver to be added to the mobile stations, which would result in considerable additional costs. Therefore, to locate a mobile station in a proposed positioning system for all mobile telephones it is preferable to use the signals of the cellular system transferred between the mobile station and the base stations, although some models of mobile stations may also include a receiver of the GPS. From the publication [1] WO 92/05672 a method is known wherein the distance of a mobile station from a base station is determined based on the propagation time of a signal transferred between the mobile station and the base station. By measuring the propagation time of the signal sent by the mobile station in the base station, a distance calculation for the interval between the mobile station and the base station is obtained. Due to a certain accuracy in the measurement associated with the distance measurement, the calculated location of the mobile station is a ring-shaped area, the width of which depends on the accuracy of the propagation time measurement. A corresponding propagation time measurement can also be made for a signal between the mobile station and other base stations. The result is then a ring-shaped location area for each base station involved in the measurement. In this way, the mobile station can be located at the intersection of the areas of the location, the dimensions of the intersection correspond to the accuracy of the measurement. In the method described above, the determination of the position is carried out substantially by the system, and no special functions are necessary in the mobile stations to perform the measurement. A disadvantage of the method based on the measured propagation time of a signal between the mobile station and the base stations is that the propagation time can not be easily measured with such precision that the accuracy of the location information of the mobile station is adequate. for all the applications mentioned above. further, the mobile station has to establish an uplink connection with each base station for which the propagation time must be measured. If the positioning information has to be continuously updated, the data traffic associated with the positioning places a considerable load on the connection capacity of the mobile communication system. In addition, the high volume of data traffic makes the measurement slow. Another problem with the method is that errors in the accuracy of the absolute timing of the mobile station result in errors in the result of the obtained positioning.

A method is also known based on the time difference of the received signals, where the measurement can be made by the mobile station or by the system. Suppose that a mobile station receives signals from a plurality of base stations. A calculation for the position of the mobile station is determined by means of the observed time difference (OTD) between the signals received from the base stations, so that it is possible to calculate by means of the time difference between the signals received from two base stations the difference dl-d2 between the distance di between the mobile station and a first base station and the distance d2 between the mobile station and a second base station. Then those potential location points of the mobile station in which the value of the difference in distance is equal to dl-d2 constitute a curve in the form of a hyperbola, which thus represents the potential location points of the mobile station . Since the result of the measurement involves a certain margin of error, the location area of the mobile station is actually a band between two hyperbolas, the width of the band depends on the margin of error of the measurement result. When the signals are received from at least three base stations, the result consists of a plurality of location areas and the mobile station is located at the intersection of those areas. The determination of a restricted location area requires the measurement of the time difference for the signals received from at least three base stations unless other methods such as measuring the propagation time in addition to measuring the time difference are used. . If other additional methods are used, it is possible to use the time difference measured for the signals received from only two base stations. This determination of the location of a mobile station can be made either by the mobile station or by the system. From the patent document [2] Fl 101445 a solution is known in which a mobile station measures the time differences of signals received from the base stations and sends the data of the measured time differences to the mobile communication system. A mobile location center in the mobile communication system uses the data of the time differences measured, the coordinates of the position of the base station and the data of the relative time difference (RTD) of the base station to calculate the location of the mobile station. In the solutions described in documents [1] and [2], the location of a mobile station is calculated by a cellular network. From document [3] EP 398773 a solution is known in which a mobile station receives information from a mobile communication system about the relative time differences and the coordinates of the position of base stations located in the area around the station mobile. Then, the mobile station measures the time differences of the signals received from the base stations and determines the position of the mobile station based on the time differences measured and the relative time differences and the position coordinates of the base stations, using an algorithm for determining the position stored in the mobile station. In this way, the time difference between the signals received by a mobile station of two base stations is called an observed time difference (OTD). The measurement of the observed time difference is used to synchronize the mobile station with the clock of the new servant base station in connection with an automatic control, thus the method for measuring the DTO is known in the prior art. The OTD is measured in two steps because a mobile station can not receive signals from two base stations simultaneously. First, the mobile station measures a first time difference between the clock of the mobile station and the clock of the signal received from a first base station. So, the mobile station measures a second time difference between the mobile station and a second base station. The observed time difference OTD is obtained by calculating the difference of the first and second time differences. In mobile communication systems, such as for example GSM and UMTS, the lengths of the control messages sent to the mobile stations are fixed and the channels through which the control messages are sent have limited capabilities. When new services are implemented, such as for example the positioning services described above, there is often a need to transmit more information than can be included in the message reserved for that particular purpose. For example, the SMS-CB message (Short Message Service Cell Broadcast) can be used to transmit positioning data, but this message is preferably short, only 88 bytes of which a payload portion of 82 octets can be used to transfer positioning data. As mentioned above, the positioning methods involve a lot of communication between a mobile station and the network. For example, the location data of the base station is typically indicated using the WGS-84 coordinates, since a message can not include the location data for many base stations. One solution would be to send more messages and because of that transmit more information, but this would waste the limited resources of the control channel in question. The transmission interval of the SMS-CB messages, for example, is two seconds, so that the limited communication capacity results in considerable delays if more than one message is needed to transmit a data set. In this way, a better solution for this problem is necessary.

BRIEF DESCRIPTION OF THE INVENTION An object of the invention is to provide a message transfer method that makes possible the transfer of a maximum amount of information in a fixed length message. Another object of the invention is to achieve a transfer method for the positioning data using fixed length broadcast messages and enabling a flexible and optimizable transfer of the positioning data. The objects of the invention are achieved by establishing a method for transferring data in a fixed-length message, the method comprising the steps of: - including in the payload portion of the message the content information to define the contents of the portion of the message's payload, and - include in the payload portion of the message, in accordance with the description of the content information, the information elements defined by the content information. The method according to the invention is characterized in that it is expressed in the characterization part of the independent claim directed to the method. The sub-claims describe other advantageous embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is described below, in greater detail, with reference to preferred embodiments presented by way of example and to Figure 1, which illustrates the structure of the payload portion of a message according to a modality Preferred of the invention, and Figure 2, which illustrates a method according to an advantageous embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES OF THE INVENTION A fixed length message that is sent according to the invention is achieved such that a required number of information elements (IE) can be included in it according to the needs, so that , in order to include the necessary information elements in the fixed-length message, the number of bits used to represent the information elements in question depends on the quantity and length of the information elements that are included in the message. Such information elements that can be represented by a variant number of bits are referred to herein as variable length information elements. The number of bits used to represent variable length information elements can be reduced by compromising the precision of the value represented by them. The message also includes information about which information elements are included in the message as well as the number of bits used to represent each variable length information element. This * header information "is subsequently referred to as content information Advantageously, the content information may also include information about the resolution used to represent each variable length information element.This can be done by indicating the degree of the value of the information element corresponding to a bit or by indicating the value range of the information element corresponding to the binary value range used Advantageously, the message may also include fixed length information elements in addition to the length information elements The content information can be included in the payload portion of the message, which contains the data of the information elements, or in the header portion of the message.In this application, the information element of the term refers to to an individual piece of information, such as a value of l parameter or similar.

The solution according to the invention finds particular utility in the communication of information necessary for the positioning of mobile stations since in the positioning methods described above the mobile station needs a relatively large amount of data about the base stations. Using the solution according to the invention it is possible to communicate a large amount of positioning data in a single SMS-CB message (Short Message Service Cell Broadcast).

Next, an exemplary embodiment of the invention will be described in which the positioning data is communicated to the mobile stations in an SMS-CB message for the purpose of positioning mobile stations. The size of the SMS-CB message is 88 octets, 82 octets of which can be used for the message's payload. Figure 1 shows the structure of the payload of the SMS-CB message according to this exemplary embodiment. The payload portion first has a segment 100 that indicates the content information, followed by the proper information elements 110, 120, 130, 140. In this embodiment, the content information 100 of the message is indicated by means of the first 9 bits of the payload as follows: Bi thio Definition 1, 2 and 3 define the neighboring base stations indicated 4, 5 and 6 the accuracy of the data in relation to the neighboring base stations 7 and the precision of the values of the RTD the order of the value of the RTD Let's look more closely at the definitions of these bits in this exemplary mode. Neighboring base stations, the data of which are included in the messages, are indicated using the first three bits as follows: bit 1 bit 2 bit 3 definition data from neighboring base stations include data from all neighboring base stations in the list of neighboring base stations the data of the neighboring base stations include the data of each second neighboring base station in the list of neighboring base stations, specifically those whose operating number in the list is even the data of the neighboring base stations include the data of each second neighboring base station in the list of neighboring base stations, specifically those whose operating number in the list is odd, the data of the neighboring base stations include the data of each third neighboring base station in the list of neighboring base stations , starting from the first base station in the list the data of the stations neighbor bases include the data of each neighboring third base station in the list of neighboring base stations, starting from the second base station in the list the data of neighboring base stations include the data of each third neighboring base station in the list of base stations neighboring, starting from the third base station in the list the data of the neighboring base stations comprise a sequence of bits indicating the base stations, the data of which are included in the message reserved for the last use In the above table, the bit pattern? 110 'indicates that neighboring base stations are indicated using a sequence of bits. In this case, the bit sequence is located at the beginning of the portion containing the data of the neighboring base stations in the message. The bit sequence comprises as many bits as in the list of neighboring base stations supplied to the mobile stations, and each of the bits represents a base station located at the corresponding location in the list of neighboring base stations. If a bit in the bit sequence is 0, the message does not include the data of this particular base station, and if a bit in the bit sequence is 1, the message includes the data of that particular base station. The bits 4, 5 and 6 in the content information indicate by means of a range of value of the position data the accuracy of the data of the position of the neighboring base station as follows: bi thio 4 bi thio 5 bi thio 6 in; value range 0 0 0 5 1km 0 0 1 10 km 0 1 0 15 km 0 1 1 20 km 1 0 0 25 km 1 0 1 30 km 1 1 0 35 km 1 1 1 40 km The range of value along with the The number of bits used to indicate the position information indicates the resolution of the position data. For example, if the bit pattern of bits 4, 5 and 6 is 011 'and the position information is indicated using 15 bits, the degree of value of the position information is 20 km / 215 meters, or 0.6 meters, approximately. Bits 7 and 8 indicate the accuracy of the RTD values as follows: bit 7 bit 8 precision of the RTD values 0 0 1/16 bit 0 1 1/32 bit 1 0 1/64 bit 1 1 1/128 bit Bit 9 indicates the value range of the RTD. If bit 9 is 0, the value range of the RTD is a period of time corresponding to a time segment, and if bit 9 is 1, the value range of the RTD is a period of time corresponding to 8 time segments. The bits 7, 8 and 9 also indicate the number of bits used to represent a value of the individual RTD. For example, if the RTD values cover an interval of 1 time segment, it takes 12 bits to represent the values of the RTD with the precision of 1/16 bit. In this way, the representation of a value of the RTD requires and the message in question uses a number of bits according to the table below: Bi-precision segments necessary for time represent a value of the RTD 1 1/16 bit 12 1 1/32 bit 13 1 1/62 bit 14 1 1/128 bit 15 1/16 bit 15 1/32 bit 16 1 / 64 bit 17 1/128 bit 18 If the bit pattern of bits 1, 2 and 3 in the content information is? 110 ', the payload portion comprises a sequence of bits 110 which defines in the manner described above the base stations, the position data. of which are given in this message. The next segment 120 indicates the RTD values of the neighboring base stations included in this message using a number of bits indicated by the bits 7, 8 and 9 in the content information 100. The payload portion of the following message comprises the information of the location of the servant base station 130 according to the value range indicated by bits 4, 5 and 6 in the content information 100. At this end of the payload portion indicates the location information 140 of the neighboring base stations included in this message according to the value range indicated by the bits 4, 5 and 6 in the content information 100. The location information of the base stations 130, 140 can be advantageously indicated in a way such that the location of the servant base station is given in absolute coordinates according to a predetermined coordinate system, such as the GS-84, and the data of ub The location of the neighboring base stations is indicated in relation to the servant base station. In other words, the locations of the neighboring base stations are indicated in this case as distances based on longitude and latitude of the next base station. In this way, the locations of the neighboring base stations can be indicated very precisely with a small number of bits. Further, in a preferred embodiment of the invention the number of bits used to indicate the location of a given neighboring base station can be included in the content information 100. In another preferred embodiment of the invention, the space left by other information elements in the payload it is used to indicate the locations of the neighboring base stations, so that the number of bits left to indicate a coordinate of a neighboring base station can be calculated by dividing the number of bits used to indicate the locations of the stations neighboring base first by the number of neighboring base stations and then by two. In a preferred embodiment of the invention, the neighboring base stations are divided into two or more groups, and the number of bits used to indicate the position of a given base station is determined based on the group. For example, the locations of the neighboring base stations most convenient for positioning may be indicated as a greater number of bits and a higher precision than those of other neighboring base stations. In this way, the number of bits used to indicate the data of neighboring base stations may be different for different neighboring base stations. The content information 100 may also include other information different from the information according to the example described above. This information could be for example: information on whether the base stations are synchronized or not, - information on whether the location data of the base station is encrypted or not, or for example, - information on whether the key of the cryptography used to encrypt the location data of the base station has been changed after sending the message previous. Cryptography can be used to implement location services exposed to charges, so a payment is required for the cryptography key necessary to describe the encrypted data. The message may include other information different from the information according to the example described above. For example, the message may include certain information elements of fixed length the order of which in the message with respect to other information elements and the length of which are constant so that they do not need to be entered in the information portion of the content 100 described above. If a base station is divided into sectors, each sector is mentioned according to the prior art in the list of neighboring base stations in the same way as the own base stations. In fact, an SMS-CB message or other corresponding message can be used advantageously to indicate which channels mentioned in the list of neighboring base stations correspond to the sectors of a given base station. This group of channels can be assigned common position data since the respective transmitters are physically located in the same place. In addition, the message may advantageously include information on whether the sectors in question are mutually synchronized in time. The message may also include variable data different from those described in the previous examples. In other preferred embodiments of the invention, the content information portion 100 includes a bit indicating whether a multi-frame deviation value has been assigned in conjunction with the values of the RTD. In addition, the message may also define the time slice scheme used by neighboring cells or cells, i.e. whether a particular neighbor cell uses a time slice of 156.24 bits or a sort of time slots of the 156/157 type. This can be indicated by using a sequence of bits in which the value of bits 0 indicates that the neighbor cell uses a time segment of 156.25 bits and the value of bits 1 indicates that the neighboring cell in question uses a sorting of time segments of type 156/157. In addition, the message may also include information associated with the channels divided into sectors of the neighboring cells or cells. Consider immediately the contents of SMS-CB messages according to two slightly different exemplary cases. In the first example there are 15 neighboring base stations so that the locations of the neighboring base stations can be indicated very accurately. In the second example, a message defines the locations of 22 neighboring base stations so that only relatively few bits are left to indicate the locations of the base stations, so the indication of the locations is not as accurate as the first example. In the first example, the structure of the payload portion of the SMS-CB message is as follows: information element bit information of the content 14 definition of the time-slice diagram 16 bit sequence of the neighboring base stations 0 definition of the channels divided into sectors 16 identifications of the base stations of the channels divided into sectors information of the synchronism of the stations base divided into sectors 2 diversion values of multiple frames 66 values of the RTD 154 location data of the servant cells 49 location data of the neighboring base stations 321 total 656 In this example, the message communicates the data for 15 base stations. In this example, other data leaves 321 bits for the location data of the neighboring base stations. In this example, the value range of the location of the neighboring base stations is defined as 15 km in the content information portion. Since the number of bits used to represent the location data of the neighboring base stations can not be evenly divided among the base stations, the data of certain base stations are given with a precision of one bit greater than the others. The location data of certain neighboring base stations are represented by 15 bits, so that the accuracy will be 0.46 meters per bit, approximately, and the location data of other neighboring base stations are represented by 14 bits, which results in a precision of 0.94 meters per bit, approximately. A total of 656 bits in the payload portion of the SMS-CB, or 82 octets, are used to represent the various pieces of information. In the second example, the structure of the payload portion of the SMS-CB message is as follows: information element bit information of the content 14 definition of the outline of time segments 23 bit sequence of the neighboring base stations 0 definition of the channels divided into sectors 23 identifications of the base stations of the channels divided into sectors 45 information of the synchronism of the Base stations divided into sectors Multi-frame deviation values 90 RTD values 210 Serial location data 49 Location data from neighboring base stations 194 Total 656 In this example, the message communicates data for 22 base stations. In this example, other data leaves only 194 bits for the location data of neighboring base stations because the amount of information that is communicated increases as the number of base stations increases. In this case, the number of bits used to indicate the locations of the neighboring base stations has been considerably reduced in order to facilitate the communication of all the necessary information. In this example, the location value range of the neighboring base stations is defined as 15 km in the content information portion. To use all the bits, the location data of certain neighboring base stations are indicated in this example using 7 bits, to achieve an accuracy of approximately 118 meters per bit in this way, and the location data of other neighboring base stations are indicated using 6 bits, achieving an accuracy of approximately 238 meters per bit. In this case, a total of 656 bits, or 82 octets, is also used in the payload portion of the SMS-CB to represent the various information elements. In accordance with a further aspect of the invention, there is provided a method in a mobile communication system for transferring information in a fixed-length message from a base station to at least one mobile station. Figure 2 illustrates this method according to an advantageous embodiment of the invention. According to the modality, the content information is transferred 200 in the payload portion of the message to define the contents of the payload portion of the message, and - the information elements defined by the content information are transferred 210 in the payload portion of the message according to the content information. In a further advantageous embodiment of the invention, the information elements of predetermined length are transferred 220 in the payload portion of the message in addition to the information elements defined by the content information. The advantages of the invention are numerous. Location services of mobile communication systems may have varying accuracy requirements according to the application or location. Since the positioning data message is specific to the base station, the method according to the invention can be used to freely select the accuracy of the representation of the location data of the base station for each area of the base station. In addition, the method according to the invention can be used, if desired, to describe location data of only certain base stations, such as base stations particularly advantageous from a positioning standpoint, and to exclude data from the base stations located disadvantageously from the positioning point of view, so that the mobile stations located in a particular area have at their disposal the best possible selection of base stations for positioning in that area. The exclusion of data from base stations located disadvantageously has the additional advantage that the data of the optimal base stations can be represented by a larger number of bits, that is with better precision, which improves the positioning pressure. The method according to the invention facilitates the flexible adjustment of the positioning parameters in a manner required by the characteristics of each particular position. The invention was described above with reference to its preferred embodiments, but it is obvious that the invention can be modified in many ways according to the inventive idea defined by the claims appended hereto. For example, the invention can be used in many different mobile communication systems such as for example UMTS (Universl Mobile Telecommunication System) or other mobile communication systems commonly referred to as the third generation.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (7)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A method in a mobile communication system for transferring information in a fixed-length message from a base station to at least one mobile station, characterized because: - the content information is transferred in the payload portion of the message to define the contents of the payload portion of the message, and - the information elements defined by the content information are transferred in the payload portion of the message according to the content information.
2. 2. A method according to claim 1, characterized in that the information elements comprise at least information elements that contain position data.
3. 3. A method according to claim 2, characterized in that the information elements define the location of at least one neighboring base station relative to the base station.
4. 4. A method according to claim 1, characterized in that the content information defines a value range for the data to be transferred corresponding to the binary value range of the at least one information element.
5. 5. A method according to claim 1, characterized in that the content information defines the magnitude of the degree of the value of the data to be transferred that corresponds to the smallest bit value degree of the at least one information element.
6. 6. A method according to claim 1, characterized in that the information elements of predetermined length are transferred in the payload portion of the message in addition to the information elements defined in the content information.
7. 7. A method according to claim 1, characterized in that the fixed-length message is an SMS-CB message.