Method and apparatus for measuring the transmission quality in cells of mobile radio networks

The present invention relates to a method and an arrangement for measuring the transmission quality in cells of mobile radio networks in order to enable the network operator to find places with bad transmission quality within the cells of the global system for mobile communication (GSM).

The structure and organization of a GSM network with the division into individual cells as the smallest geographical radio coverage area, which is served by a base service station (BTS), for example, from the book <img file="EP0946007A2_D0001.tif" />Mobile Communications and Intelligent Networks "by Jatzek Biala, Vieweg Verlag 1994, ISBN 3-528-05302-X, known in the cells and also when crossing the individual cells, it may due to the formation of the landscape and man-made environment again and again disturbances that cause dissatisfaction among the users of mobile telephony and are also undesirable on the part of the network operators.

In order to find these fault zones, either measurements are taken from the vehicle by means of mobile test systems or from the network. Both measuring methods have limitations. Thus, the main disadvantage of measuring vehicles is that a qualified person must drive the vehicles through the cells, measuring only one direction of transmission, namely towards the vehicle, is only possible, and the qualification of the cells is very time-consuming. The main disadvantage of a measurement from the grid is that no geographical position can be detected with the measurement, so that a detailed statement about the geographical location in the fault zone is not possible.

The present invention is therefore based on the object of proposing a method and an arrangement in which the use of highly qualified employees, who drive around in the cell to be measured, is not necessary and accurate information about the quality of transmission can be obtained within a cell.

This object is achieved by a method having the features of claim 1 and by an arrangement with the features of claim 7. Further advantageous embodiments of the method and the arrangement are to be taken from the respective related back claims.

According to the method, the cells to be measured are traversed using a mobile station (MS) and a GPS receiver and the geographical position and the time are recorded at specific times. The mobile station is a common receiving device, for example a mobile phone, which consists of the known functional groups mobile terminal, terminal adapter and terminal equipment. In addition, this apparatus has a receiving device capable of receiving the satellite-radiated geographical position as well as local time due to the so-called Global Positioning System (GPS). This mobile station may be located, for example, in the trunk of a vehicle, including a taxi or bus, and records at predetermined time intervals the GPS time and the geographical position that the vehicle currently has. In addition, at certain intervals, call setup signals are sent from any one terminal to the mobile station (MS) via a base transfer station (BTS) or vice versa, and the GPS position for each call setup signal is stored in the mobile station. The base transmission station is the base transmission station associated with the cell to be examined. After the connection has been established, it is automatically disconnected and restored after a predetermined time to minimize synchronization errors. At the same time, the signals which were sent via the BTS to the relevant MS at specific time intervals are recorded, at the same time the time stamp of the mobile radio analysis device used for this purpose being recorded. The data thus obtained are sorted together according to the time stamps, and thereafter the measurement results are output depending on the geographical position and the time. Thus, due to the presence of the exact geographical position, an analysis of the network by means of the mobile radio analysis device can be carried out with regard to the parameters customary for the qualitative assessment.

The sorting of the recorded data by timestamp is carried out in such a way that each signal recorded by the mobile radio analyzer is assigned the geographical position which comes closest to the position of the entire signal by comparing the time stamps of the mobile station and the mobile radio analyzer.

Due to the possibly different cycle times in the mobile station and the mobile radio analyzer, the internal clock time of the mobile station and the mobile radio analyzer is synchronized according to a preferred embodiment, taking into account the GPS clock time as the master time. The cycle times of the mobile radio analyzer are determined by the PCM cycle times of the measurement interface (Abis interface). The correction of the time stamps of the mobile station as well as the mobile radio analysis device takes place according to the condition <maths id="math0001" num=""><math display="inline"><mrow><msub><mrow><mtext>tx</mtext></mrow><mrow><mtext>corr</mtext></mrow></msub><msub><mrow><mtext> = tx + (t</mtext></mrow><mrow><mtext>GPS</mtext></mrow></msub><msub><mrow><mtext> - t</mtext></mrow><mrow><mtext>q</mtext></mrow></msub><mtext>) / n × x</mtext></mrow></math><img file="EP0946007A2_D0002.tif" /></maths>, t_GPS is the time within a GPS period, which can be assumed as one second, for example, since the GPS sends a signal every second. t_q is the period of time that the respective measuring unit whose time stamp is to be corrected measures while the GPS is going through exactly one second. tx is the timestamp to be corrected, d. H. the asynchronous message that is not received in the one-second grid of the GPS. This is corrected by setting time intervals within a GPS period, the time intervals x being chosen to be fairly close to the measured time stamp. x indicates the number of the interval in which the timestamp is to be corrected in relation to the interval. The correction is made according to the formula with the total number n of all intervals, the interval length, as already mentioned above, must be determined as needed (subdivision of the GPS period of one second in, for example, 1,000, 100 or only 10 intervals).

In addition to compensate for time delays, which may occur due to the transfer of the data from the BTS to the MS in terms of the timestamps According to a further preferred embodiment, prior to the sorting of the recorded data and after the synchronization to the GPS clock time, the time stamps of a same signal of the MS and the mobile radio analyzer are compared and, with a difference, the difference is added as transmission delay to the time stamps of the MS.

For the evaluation, the recorded data of the mobile station can be transmitted via the global system for mobile communication to the mobile radio analyzer. This saves time and effort compared to recording on a floppy disk from feeding into the mobile radio analysis device.

The arrangement comprises at least one mobile station having a GPS receiver for detecting the geographical position of the mobile station and the GPS time and a recording unit for storing the geographical position and the associated time at certain intervals and the time when receiving a call setup signal. The arrangement also comprises a mobile radio analysis device which can be switched by means of an interface (Abis interface) between one or more base transmission stations (BTS) and the associated base station controllers (BSC). The mobile radio analyzer (MA) also has a GPS receiver for recognizing the graphical position and the time, in particular for the GPS time as the master time for the synchronization of the internal MA time, which is based on the Abis time synchronize. In addition, the MA has a data recording unit for recording and storing the transmitted data and time stamps between at least one of the base transmission stations and one of the mobile stations, a data evaluation unit for mixing the recorded data of the mobile station with the recorded transmitted data, and a data unit for outputting the transmitted data depending on the geographical position in the mobile station and in time.

As a result of the method and the arrangement according to the invention, it is thus possible to obtain all measured values ​​for both directions (uplink, downlink) as well as better information about the supply of the cell. In addition, the geographical position of a problem can easily be determined or position-dependent statistics can be created using the known information that can be output via the mobile radio analysis device. The use of highly qualified employees in a mobile test station is no longer necessary.

The invention will be explained in more detail in conjunction with the accompanying drawings with reference to an embodiment. They show:<dl id="dl0001"><dt>FIG. 1</dt><dd>The arrangement with only one mobile station and the linkage of the mobile radio analyzer to the mobile network in a schematic block diagram representation and</dd><dt>FIG. 2</dt><dd>a block diagram illustrating the functional relationship of each arranged in the mobile radio analyzer and in the mobile station facilities.</dd></dl>

In Figures 1 and 2, the individual assignments and modes of action of the individual units are shown schematically and will be explained together below with reference to the figures.

To carry out the measurement within a cell, a vehicle is needed in which a mobile station, for example a mobile phone, is located. The mobile station requires, in addition to the usual equipment present in these devices, a GPS receiver capable of receiving the satellite-transmitted information regarding geographical position and time due to the GPS system. The mobile system can either be transported in test vehicles or by buses or taxis. In the mobile system, the GPS time and the geographical position are stored by means of a recording unit A. This can for example be done on a floppy disk or in a memory that can be retrieved over the mobile network again. The mobile station has the ability to send calls automatically, or it is called by means of a machine over the mobile network with the appropriate number. After the call has been established, the connection is terminated within a predetermined time. With each call setup signal and with each measurement report generated by the GPS system, the GPS position is stored.

When generating a measurement report, for example every 480 ms, the resolution depends on the speed of the vehicle in which the mobile station is located. The accuracy depends on the GPS receiver, which is assumed to be 5 m in this embodiment. This results in the following resolution:<tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="6" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="26.25mm" /><colspec colnum="2" colname="col2" colwidth="26.25mm" /><colspec colnum="3" colname="col3" colwidth="26.25mm" /><colspec colnum="4" colname="col4" colwidth="26.25mm" /><colspec colnum="5" colname="col5" colwidth="26.25mm" /><colspec colnum="6" colname="col6" colwidth="26.25mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Speed ​​in km</entry><entry namest="col2" nameend="col2" align="right">0</entry><entry namest="col3" nameend="col3" align="char" char=",">20</entry><entry namest="col4" nameend="col4" align="char" char=",">50</entry><entry namest="col5" nameend="col5" align="char" char=",">100</entry><entry namest="col6" nameend="col6" align="char" char=",">200</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Resolution in m</entry><entry namest="col2" nameend="col2" align="right">0</entry><entry namest="col3" nameend="col3" align="char" char=",">2.7</entry><entry namest="col4" nameend="col4" align="char" char=",">6.7</entry><entry namest="col5" nameend="col5" align="char" char=",">13.4</entry><entry namest="col6" nameend="col6" align="char" char=",">26.7</entry></row></tbody></tgroup></table></tables>

The associated mobile radio analyzer MA consists of a known mobile radio analyzer MA10 of the applicant with an additional GPS receiver which controls the absolute time. The absolute time is the timestamp with which the recording is started. During recording, all messages are time-stamped, which refers to the Pulse Code Modulation (PCM) connection. All messages are detected and stored in the data recording unit D. After the recording, the transmitted data is combined with the data of the mobile station sorted by time stamp. For this purpose, the data is either transmitted from the mobile station via the network or read in via a floppy disk and stored in the memory unit S.

In the mobile radio analyzer MA, a call recording is performed in which all the signal data including a defined telephone number or a set of telephone numbers are detected.

For the time synchronization due to the differences between the GPS time and the internal time of the mobile station and the Abis interface, in both the mobile station MS and the mobile radio analyzer MA, the recording unit A or the data recording unit D accesses the respective one GPS receiver and determines a corrected GPS time according to the formula <maths id="math0002" num=""><math display="inline"><mrow><msub><mrow><mtext>tx</mtext></mrow><mrow><mtext>corr</mtext></mrow></msub><msub><mrow><mtext> = tx + (t</mtext></mrow><mrow><mtext>GPS</mtext></mrow></msub><msub><mrow><mtext> - t</mtext></mrow><mrow><mtext>q</mtext></mrow></msub><mtext>) / n × x</mtext></mrow></math><img file="EP0946007A2_D0003.tif" /></maths>,

After the data supplied by the mobile station is stored in the mobile radio analyzer, the comparator V can compare the timestamps of a same signal of the mobile station and the mobile radio analyzer and, with a difference, add the difference as a transmission delay to the time stamp of the mobile station.

Assuming that such a later correction is not required, the mobile station and the mobile radio analyzer could create the following data tables: <tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="4" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row><entry namest="col1" nameend="col4" align="left">Mobile Station</entry></row><row><entry namest="col1" nameend="col1" align="left">event</entry><entry namest="col2" nameend="col2" align="center">time stamp</entry><entry namest="col3" nameend="col3" align="center">Pos. X</entry><entry namest="col4" nameend="col4" align="center">Pos. Y</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">GPS</entry><entry namest="col2" nameend="col2" align="center">12: 05: 49,367</entry><entry namest="col3" nameend="col3" align="center">48.49.12</entry><entry namest="col4" nameend="col4" align="center">9:00:34</entry></row><row><entry namest="col1" nameend="col1" align="left">GPS</entry><entry namest="col2" nameend="col2" align="center">12: 05: 59,367</entry><entry namest="col3" nameend="col3" align="center">48.49.23</entry><entry namest="col4" nameend="col4" align="center">9:00:25</entry></row><row><entry namest="col1" nameend="col1" align="left">call setup</entry><entry namest="col2" nameend="col2" align="center">12: 06: 02,317</entry><entry namest="col3" nameend="col3" align="center">48.49.23</entry><entry namest="col4" nameend="col4" align="center">9:00:25</entry></row><row><entry namest="col1" nameend="col1" align="left">GPS</entry><entry namest="col2" nameend="col2" align="center">12: 06: 09,367</entry><entry namest="col3" nameend="col3" align="center">48.49.56</entry><entry namest="col4" nameend="col4" align="center">9:00:38</entry></row><row><entry namest="col1" nameend="col1" align="left">:</entry><entry namest="col2" nameend="col2" align="center">:</entry><entry namest="col3" nameend="col3" align="center">:</entry><entry namest="col4" nameend="col4" align="center">:</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">GPS</entry><entry namest="col2" nameend="col2" align="center">12: 31: 39,367</entry><entry namest="col3" nameend="col3" align="center">49:00:63</entry><entry namest="col4" nameend="col4" align="center">9:00:41</entry></row></tbody></tgroup></table></tables><tables id="tabl0003" num="0003"><table frame="all"><tgroup cols="2" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><thead valign="top"><row><entry namest="col1" nameend="col2" align="left">Mobile analysis station</entry></row><row><entry namest="col1" nameend="col1" align="left">event</entry><entry namest="col2" nameend="col2" align="center">time stamp</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">MSG-1</entry><entry namest="col2" nameend="col2" align="center">12: 01: 41,951</entry></row><row><entry namest="col1" nameend="col1" align="left">MSG2</entry><entry namest="col2" nameend="col2" align="center">12: 05: 29,443</entry></row><row><entry namest="col1" nameend="col1" align="left">call setup</entry><entry namest="col2" nameend="col2" align="center">12: 06: 02,317</entry></row><row><entry namest="col1" nameend="col1" align="left">MSG3</entry><entry namest="col2" nameend="col2" align="center">12: 06: 03,725</entry></row><row><entry namest="col1" nameend="col1" align="left">:</entry><entry namest="col2" nameend="col2" align="center">:</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">MSGn</entry><entry namest="col2" nameend="col2" align="center">12: 15: 58,888</entry></row></tbody></tgroup></table></tables>

A standard GPS unit generates a new set of data every second. The table for the mobile system consists of rows in which the data is taken directly from the GPS system (marked with the event GPS). The other rows contain transmission events that are asynchronous to the GPS events. For the transmission events, the corresponding timestamps are taken from the mobile station's internal time and then, as mentioned above, synchronized by the GPS system. The corresponding geographic location for the corresponding transmission event is taken from the last GPS event. The call setup signal, which contains some other parameters and also the call number in addition to a SETUP signal, is selected for the respective mobile station in order to avoid incorrect connections for the entry in the above table.

The mobile station analysis table contains transmission information that is irregular and unpredictable compared to the regular GPS heartbeats. The time stamp is, as mentioned above, resynchronized by the GPS system.

In the evaluation device W, the end data are now mixed together according to the following table: <tables id="tabl0004" num="0004"><table frame="all"><tgroup cols="4" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="left">event</entry><entry namest="col2" nameend="col2" align="center">time stamp</entry><entry namest="col3" nameend="col3" align="center">Pos. X</entry><entry namest="col4" nameend="col4" align="center">Pos. Y</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">MSG-1</entry><entry namest="col2" nameend="col2" align="center">12: 01: 41,951</entry><entry namest="col3" nameend="col3" align="center">48.48.51</entry><entry namest="col4" nameend="col4" align="center">9:00:52</entry></row><row><entry namest="col1" nameend="col1" align="left">MSG2</entry><entry namest="col2" nameend="col2" align="center">12: 05: 29,443</entry><entry namest="col3" nameend="col3" align="center">48.49.12</entry><entry namest="col4" nameend="col4" align="center">9:00:34</entry></row><row><entry namest="col1" nameend="col1" align="left">call setup</entry><entry namest="col2" nameend="col2" align="center">12: 06: 02,317</entry><entry namest="col3" nameend="col3" align="center">48.49.23</entry><entry namest="col4" nameend="col4" align="center">9:00:25</entry></row><row><entry namest="col1" nameend="col1" align="left">MSG3</entry><entry namest="col2" nameend="col2" align="center">12: 06: 03,725</entry><entry namest="col3" nameend="col3" align="center">48.49.56</entry><entry namest="col4" nameend="col4" align="center">9:00:38</entry></row><row><entry namest="col1" nameend="col1" align="left">:</entry><entry namest="col2" nameend="col2" align="center">:</entry><entry namest="col3" nameend="col3" align="center">:</entry><entry namest="col4" nameend="col4" align="center">:</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">MSGn</entry><entry namest="col2" nameend="col2" align="center">12: 15: 58,888</entry><entry namest="col3" nameend="col3" align="center">49:00:63</entry><entry namest="col4" nameend="col4" align="center">9:00:41</entry></row></tbody></tgroup></table></tables>

The positions x and y are added to the table of the mobile radio analyzer by comparing the timestamps of the two tables and listing them in order. The MSG messages receive the position in which the timestamps of the two tables best correlate.

Following this, the above table can be output with a corresponding output device M, for example a screen or printer.

On the basis of these determined values, further applications can be developed, which are made available via the mobile radio analysis device MA. This generates, for example, various statistics concerning the cells and / or the calls from the position of the Abis interface.

Together with the geographical position much more complex results can be generated. These can be represented, for example, in ASCII tables for further processing or in x / y graphs. The measured points mark a geographical position in which a previously specified event occurred. For example, the quality of the transmission can be displayed separately according to uplink / downlink results. Other possibilities of the known evaluations taking into account the geographical position are:<ul id="ul0001" list-style="bullet" compact="compact"><li>Call Attempts / Call Achievements per Location</li><li>failed handover attempts / calls per location</li><li>abnormal call terminations / call transfer completions per location</li><li>Call transfer cases per location</li><li>Interference analysis</li><li>Island Analysis</li><li>Combination of the Abis interface Call recording with the geographical position</li><li>Correlation of call recording between the Abis interface and the mobile station.</li></ul>