Traffic location in mobile cellular telecommunications systems
Contents
1. 0 e Current Channel last measurement of best server 0 Patent Application Publication Aug 23 2001 Sheet 9 of 13 US 2001 0016490 A1 Algorithm 3 tor each neighbour cell 3 1 fori 1to6 3 4 Go to next Yes neighbour cell No Test Transmitter values jare taken from Test Transmitter dialog box NCC BCC and BCCR index if used Test Transmitter NCC BCCH and BCCH index Yes 3 5 Test Transmitter found TRUE Threshold level value _ Jinput from Test Transmitter dialog box No 3 6 Is neighbour cell i RXLEV 110 correction factor gt threshold level No Yes US 2001 0016490 A1 Patent Application Publication Aug 23 2001 Sheet 10 of 13 qns AJTXY 1189 Dues lt 104924 u00981102 AJIXH SN 1199 1noqyfau Si ore lind A31Xu 1199 Huas lt 10398 V0 91100 A31Xu ON 189 Inoqybiau sj ele SIA HUIJUMOP X1Q SI 275 6t ISTVI 8jqeuea xny 1343S 159Q Jap IWSUBI 159 pjousaJu uo jueujainseaui ISE jguueu zuana 1ejunoo plousaJu BAOYE SJUAWAINSEIW A31Xu JO Ou jueuraJou 9t 0 J8AJ9S 1599 JO JUQUISINSPALU ISP QUUEYS JUNI 0 PlOysasy uo jyreugJnseauu ISP jouueu JUNI Lt US 2001 0016490 A1 Patent Application Publication Aug 23 2001 Sheet 11 of 13 0 101195 Saq Jo USUJSITiSESUI 158 00045 juana 0 PIOYSasy uo JUSWSINSPAU JSP Jauugyo PUNI GLE U9y2. Call time in Test Transmitter RXLEV measurements are the best server 0118 The HSD algorithm is depicted the flow chart of FIGS 3 to 7 There are two parts of the algorithm The first part is the main frame of the software which is the user interface including user input calculation and results dis play while the second part is the details of the calculation procedures For the main frame of the algorithm in order to start the Hot Spot calculation users have to execute the file HotSpot exe Then the main window of the software will be displayed This is the point where the main frame of the algorithm starts The program needs two inputs for the calculation the A file and the data entered from the user Each calculation process will only calculate the result for one test transmitter measurement This part of the algorithm is labeled from 0 1 to 0 10 in the flow chart of FIG 3 as follows 0119 Step 0 1 The main dialogue box of Hot Spot is displayed as the user runs the HotSpot exe file 0120 Step 0 2 The program waits for the user to input data The user follows the instructions provided in the user manual and inputs the data required for the cal culation for example the name of the A measure ment file the threshold level the power correction factor and the start time and finish time 0121 Step 0 3 Once the user has filled in the required information the calculation can be started The pro gram lo
3. active cell in the network the traffic can be measured using OMC operation amp maintenance centers counters 0024 2 The mobile BTS is an active cell but the Directed Retry feature is activated for it From the US 2001 0016490 A1 OMC a report is retrieved to review the total number of MS being diverted to other cells for further call estab lishment 0025 3 The mobile BTS is a passive cell i e broad casts in one frequency but it is barred so that it cannot accept calls The BTS is set as neighboring cell of the surrounding cells so that mobiles measure its signal to do that mobile stations need to decode the FCCH and SCH frequency correction and synchronization chan nels so a dummy transmitter is not possible that is then reported to the BSC base station controller Analysis of measurements allows discrimination of traffic that is generated in the foot print of the BTS 0026 Thus in accordance with the invention for solu tions 1 and 2 the test transmitter constitutes the serving cell for mobile stations and said associated cells constitute the neighboring cells of the serving cells For solution 3 how ever said associated cells constitute the cell serving the mobile stations and neighbouring cells of the serving cell 0027 The first solution is quite complex because base station parameters such as handover thresholds and neighbor lists have to be configured not only for the micro base station but
4. for analyzing said second set of test results to compare those first response signals which are greater than a predetermined threshold value with the second response signals to determine the value of the first response signals in relation to the second response signals 20 Apparatus according to claim 19 wherein the com paring means comprises means for determining which of those first response signals greater than a predetermined threshold value are also greater than the corresponding second response signals 21 Apparatus according to claim 20 wherein the com paring means includes means for adding a correction factor to said first response signals to account for the test trans mitter means transmitting at a different power level to said base stations 22 Apparatus according to claim 21 including means for locating a predetermined number having the largest values of the first and second response signals and determining whether a said first response signal is present in said predetermined number 23 Apparatus according to claim 22 including means for obtaining a time of transmission value by multiplying the number of those first response signals greater than a prede termined threshold value by a time constant representing the interval between said first response signals for a single mobile station and or including means for obtaining a further time of transmission value by multiplying the num ber of those first response signal
5. for the surrounding ones and they might require new tuning every time the mobile station is moved With the first and second solutions there is the added complexity of needing a way to connect the base station to its BSC probably via microwave links This might be completely impossible in some situations and is in general impractical 0028 Therefore the third solution is preferred In addi tion to the passive mobile BTS for measurement recording an Apis protocol analyzer is preferably used This is a standard diagnostic and analysis device for connecting in the Ay interface between the BTS and BSC Alternatively any suitable analysis equipment may be employed 0029 This third solution is very well suited to identify the best possible location for micro or pico cells in the case of hot spot relief especially if the area under consideration has been limited using preliminary manual techniques Fur ther it permits the invention to be implemented with a minimum of additional equipment requiring merely a test transmitter a protocol analyzer and software for analyzing the results provided by the protocol analyzer 0030 As preferred said method for analyzing test results comprises analyzing a first set of test results to determine those first response signals which are greater than a prede termined threshold value and analyzing a second set of test results to compare those first response signals which are greater than a pred
6. is equal to 255 same as if the current measurement no equal to 0 step 2 5 is taken If it is not then step 2 4 is executed 0171 Step 2 4 Update Channel data B that is set both Current Channel last measurement on threshold and last measurement of best server to O This step simply assumes the test transmitter does not exist 0172 Step 2 5 It checks the time gap between the current and the previous measurement time If it is greater than 700 ms step 2 6 is executed Otherwise step 2 7 is taken 0173 Step 2 6 The same as step 2 4 0174 Step 2 7 The same as step 2 2 0175 Referring to FIG 6 this part of the algorithm analyses the data of Valid measurement The main function of this sub procedure is to search for the test transmitter in the neighbor cell list then compare the MS RXLEV mea surement from the test transmitter with the threshold level usually set as the minimum acceptable level for satisfactory reception by MS in the vicinity If it is above the threshold level compare it with the RXLEV level of other neighbor cells and the serving cell which is done in the sub procedure of FIG 7 Since the test transmitter transmits at a lower power level than a BTS 0 5 Watt as compared with 30 Watts a power correction factor is added to the RXLEV measurement on the test transmitter before any comparison take place The user sets both threshold level and the correction factor 0176 Step 3 1 The be
7. station controller for recording the response signals 6 A method according to claim 5 wherein said analyzer means provides a file of the response signals for further analysis for each site of the test transmitter means 7 A method according to claim 6 wherein said step of analyzing comprises analyzing said received first response signals to determine those first response signals which are greater than a predetermined threshold value and comparing those first response signals which are greater than a predetermined threshold value with the second response signals to determine the value of the first response signals in relation to the second response signals 8 A method for assessing traffic density in a mobile cellular telecommunications system by analyzing test results obtained from a test procedure involving a test transmitter making test transmissions and mobile stations within its vicinity making first response signals to said test transmissions and second response signals to corresponding transmissions made by the base stations of associated cells received versions of the first response signals constituting a first set of test results and received versions of the second response signals constituting a second set of test results US 2001 0016490 A1 said method for analyzing test results comprising analyz ing said first set of test results to determine those first response signals which are greater than a predeter mined
8. threshold value and analyzing said second set of test results to compare those first response signals which are greater than a predetermined threshold value with the second response signals to determine the value of the first response signals in relation to the second response signals 9 A method according to claim 8 wherein the threshold value comprises the minimum acceptable received signal strength value for MS in said vicinity 10 A method according to claim 9 wherein said com paring step involves determining which of those first response signals greater than a predetermined threshold value are also greater than the corresponding second response signals 11 A method according to claim 10 wherein said com paring step involves adding a correction factor to said first response signals to account for the test transmitter means transmitting at a different power level to said base stations 12 A method according to claim 11 including in an initial step locating a predetermined number having the largest values of the first and second response signals and determining whether a said first response signal is present in said predetermined number 13 A method according to claim 12 wherein a time of transmission value is obtained by multiplying the number of those first response signals greater than a predetermined threshold value by a time constant representing the interval between said first response signals for a single mobile
9. 8 Otherwise goes to step 4 5 0200 Step 4 5 It compares the RXLEV of the test transmitter with the RXLEV of the neighbor cell j If the test transmitter has a higher RXLEV goes to step 4 5 Otherwise goes to step 4 6 0201 Step 4 6 Increment j Examine the next neighbor cell 0202 Step 4 7 If the test transmitter has a lower RXLEV set the Test Transmitter best server to FALSE 0203 Step 4 8 The exit of the for loop 0204 Step 4 9 It tests the Test transmitter best server If it is TRUE it means the test transmitter is the best server out of the serving cell and other neighbor cell Goes to step 4 10 However if it is FALSE the test transmitter is not the best server and goes to step 4 11 0205 Step 4 10 Increment no of best server mea surement counter and set current channel last mea surement of best server equal to 1 0206 Step 4 11 Set the current channel last measure ment of best server equal to 0 It is because the test transmitter in the measurement is not the best server 0207 The END PROCEDURE is the final step of the calculation part The output of this procedure is the results that the user will be shown The HSD software calculation algorithm produces four result values 0208 The percentage of measurement reports within the analysis time window for which the test transmitter received signal level plus user entered power correc tion factor is abo
10. L AS Tv4 punoj Jayiwisued 3591 J B16 muoo g 9134 dool 9 0 7110 XI LEE P0109 9L SYA JNYI JenJas 1599 Jayiusuelj 159 LLE 3815 19185 1590 19 lWSUBI 1591 PLE SIA JS 1Y4 19A18S 1599 88A jS 1V4 18A18S 1590 19 ILUSUBI 1s9 ZLE Jayiwsuel 159 GLE ON ON eee ewe eee Patent Application Publication Aug 23 2001 Sheet 12 of 13 US 2001 0016490 A1 FIG 7 Algorithm 4 4 1 Is Test Transmitter best server TRUE No Y 4 2 Current Channel E last measurement of best server 0 boolean FALSE value 4 3 for j 1 to 6 j i 4 6 increment j 4 5 Is neighbour cell 1 RXLEV correction factor gt neighbour cell j RXLEV 4 7 Test Transmitter best server FALSE 4 8 Exit for j 1 to 6 loop Patent Application Publication Aug 23 2001 Sheet 13 of 13 US 2001 0016490 A1 4 9 Is Test Transmitter best server TRUE 4 11 Current Channel last measurement of best server 0 boolean FALSE value YES 4 10 Increment no of best server measurements counter Current Channel last measurement of best server 1 boolean TRUE value of Test Transmitter RXLEV measurements above threshold 100 no of RXLEV measurements above threshold total no of measurements Call time in Test Transmitter RXLEV above threshold no of RXLEV measurements above threshold
11. Protocol Analyzer screen and a visual check made that the test transmitter is being satisfactorily received Once A Protocol Analyzer Files have been recorded for one test site the test transmitter is moved to the next site SZ and another A Protocol Analyzer file recorded for the same period of time For each of the test sites in the coverage area the data is recorded during the periods of greatest traffic load Although a data recording time of around half an hour is usual the time needed is dependent on the test site and type of hot spot area for example train bus station or air sea port etc 0050 The test transmitter 8 the source for the dummy BTS transmissions to simulate different possible BTS loca tions has the following specification 0051 Integral antenna with external antenna connec tor 45 550 0052 0053 Optional external DC PSU 0054 Transmit power 0 1 0 5 W 2 5 dB Internal battery with run time gt 1 Hr 0055 Operating frequency three different units for either 0056 935 960 MHz or 0057 1805 1880 MHz or 0058 1930 1990 MHz 0059 Transmits GSM channels 0060 Frequency Correction Channel FCC 0061 Synchronization Channel SCH 0062 Broadcast Control Channel BCCH 0063 Configuration 0064 Although the test transmitter configuration will to some extent be dependent on the settings and channel assignment used in the existing mobile network the basic tes
12. Test Transmitter measure ments above thresholdx0 48 Seconds 0113 2 of measurement report for which the test transmitter signal level was above the user defined threshold as amended by the power correction factor and is received as Best Server 0114 Best Server is taken to mean Test Transmitter received at a higher level than the current server and all the neighbor cells 0115 Time 2 Total no of Test Transmitter measure ments as Best Server above thresholdx0 48 Seconds US 2001 0016490 A1 0116 TNM Total Number of Valid Measurements e results are explained in the following table 0117 Th 1 plained in the following tabl Parameter Definition Percentage of Test Transmitter RXLEV measurements above hreshold Call time in Test Transmitter RXLEV measurements above hreshold The percentage of measurement that test ransmitter has RXLEV above hreshold The call time that test transmitter has RXLEV above threshold It is obtained by multiplying 0 48 seconds by the number of test transmitter RXLEV measurements that are above threshold The percentage of measurement that test ransmitter has the highest RXLEV among the serving cell and all other neighbour cell The call time that test transmitter is the best server It is obtained by multiplying 0 48 seconds by the number of test ransmitter measurements in which it is he best server Percentage of Test Transmitter RXLEV measurements are the best server
13. and then compared with the signal strength reported by the BTS of the serving cell to determine which is greater A correction value is added to account for the smaller power of the test transmitter relative to the BTS If greater than the serving BTS the first response signal is compared with the signal strengths reported by neighboring cells to determine whether the first response signal has the greatest value and can therefore be classified as best server BRIEF DESCRIPTION OF THE DRAWINGS 0040 A preferred embodiment of the invention will now be described with reference to the accompanying drawings wherein 0041 FIG 1 is a schematic plan illustrating the method of the invention 0042 FIG 2 is a view of an interface of the analysis software of the present invention and US 2001 0016490 A1 0043 FIGS 3 to 7 are flow charts illustrating the analysis method of the present invention DESCRIPTION OF THE PREFERRED EMBODIMENT 0044 Referring to FIG 1 of the drawings a GSM mobile telecommunications system comprises an array of cells including a cell 2 served by a Base Transceiver Station BTS 4 with neighboring cells N1 N6 served by respective BTS4N1 6 Mobile stations MS 6 are indicated by star shapes As shown the mobiles are concentrated in a region overlapping cells 2 and N2 A mobile test transmitter 8 simulating the transmissions of a GSM BTS is moved to a number of positions S1 Sj within cells 2 an
14. as United States 200100164904 a2 Patent Application Publication co Pub No US 2001 0016490 A1 Martin Leon et al 43 Pub Date Aug 23 2001 54 TRAFFIC LOCATION IN MOBILE CELLULAR TELECOMMUNICATIONS SYSTEMS 76 Inventors Silvia Martin Leon Swindon GB Mustafa Ahmed Woking GB Timothy David Hurley Swindon GB Correspondence Address Docket Administrator Room 3C 512 Lucent Technologies inc 600 Mountain Avenue P O Box 636 Murray Hill NJ 07974 0636 US 21 Appl No 09 737 689 22 Filed Dec 15 2000 30 Foreign Application Priority Data Dec 21 1999 EP 99310353 0 Publication Classification ETT Int CLA a utat tus H04Q 7 20 BANG US El ss 455 424 455 453 455 67 1 455 423 57 ABSTRACT In order to automate the process of locating hot spots in an exisiting mobile cellular telecommunications system with a view to installing new BTS a method for assessing traffic density comprises providing a test transmitter and moving it to one or more selected sites within existing cells of the sys tem the transmitter transmitting test signals to mobile stations within its vicinity the mobile sta tions within the vicinity transmitting first signal strength response signals to said test signals and said mobile stations transmitting second signal strength response signals to corresponding test signals from base stations of associated cells and analyzing received first and
15. at is received in the test area from the existing cells in the vicinity Identifying the test area 0078 Using coverage prediction software and field strength measurement results if available to estimate the field strength that is received in the test area from the test transmitter and raise it to such a level that it is the strongest signal in the test area 0079 Cell Access Barring 0080 The test transmitter is set as Barred to prevent mobiles from attempting to use the cell and thereby delay their access to the existing network 0081 Broadcast Control Channel BCCH 0082 The System Information SI is transmitted on the BCCH 0083 If the BCCH is switched Off then only the FCH and SCH are transmitted 0084 Provided that the Cell Barring is set On then the BCCH can be set On for the purpose of the HSD test 0085 BCCH Allocation BA List 0086 The BA list is used to broadcast a list of the neighbor cells to the mobiles in the vicinity 0087 This facility is not used for the HSD test and the BA List can be set Off 0088 0089 It is necessary for the HSD software 16 to identify the received signal level measurement report from the test transmitter when it appears in the measurement reports of the neighbor cells received by the mobiles in the vicinity of the test site Identification of Test Transmitter 0090 The HSD software supports two means
16. d N2 where localized areas of high traffic density hot spots are thought to exist but their precise location is unknown Although the test transmitter sends GSM compatible broadcast signals it is barred from receiving calls Trans mitter 8 has a low power in relation to BTS 4 etc and has a range indicated by circle V extending about 1 km in its vicinity The MS 6 in its vicinity report the signal level that they receive from the test transmitter together with mea surements from neighboring cells to their serving cell 0045 The received signal strength of the test transmitter as reported by MS in the vicinity and sent to their serving BTS are then forwarded via 2 Mb s circuits 10 of the Apis interface to the Base Station Controller BSC site 12 These measurement reports are intercepted on the 2 Mb s circuits and recorded by an A protocol analyzer 14 this is a standard commercially available item from a variety of suppliers 0046 The intercepted measurement reports are analyzed by HSD Hot Spot Detector software 16 and the position of the test transmitter which if it were to be replaced by a BTS would serve the most traffic can be calculated 0047 Prior to commencing the measurement report analysis an initial test procedure is carried out to manually identify likely areas of localized traffic congestion where it may be feasible to deploy an additional cell This activity is based on a combination of the
17. e analysis software 16 and the user The Test Transmitter dialog box comprises the following sections 0101 Analysis Parameters User enters parameters that are used in the calculation 0102 Measurement Time User enters start and fin ish date of the test as well as the start and finish time of the measurement The start and finish time is used as a filter for the timestamp entries in the source Abis log file 0103 Antenna Antenna specific data is entered 0104 Lat Long Location The user enters the lati tude and longitude location of test transmitter 0105 Process Log File Button Upon selection the source Abis Log File is processed 0106 Default Values Button Upon selection all dia log fields are populated with default values 0107 View Result Button Upon selection the user is returned to the main interface window and can view the result of the current analysis 0108 View Source Log File Button Upon selection the source file is opened and printed in the dialog window 0109 The Analysis Results Window is where all the calculation results are presented to the user This comprises the following 0110 Output test file name The path and directory of the output test transmitter output file 0111 1 of measurement report for which the test transmitter signal level was above the user defined threshold as amended by the power correction factor 0112 Time 1 Total no of
18. el time of last measurement and number of last easurement is set to measurement time and measurement number respectively Aug 23 2001 0166 Step 1 19 Measurement Result event not found means there are no more measurements There fore go to the END PROCEDURE 0167 Referring to FIG 5 this algorithm is used to process the data if the measurement is Not Valid In most cases the reading of the previous measurement is used when a Not Valid measurement is found However if the not valid measurement has measurement number of O and the mea surement time between the pervious and the current mea surement is more than 700 ms then it will assume the test transmitter does not exist 0168 Step 2 1 It checks the measurement number if the measurement number is larger than O then step 2 2 is executed If it is equal to O then it goes to step 2 3 0169 Step 2 2 Update Channel data A that is set the no of RXLEV measurement above threshold equal to the sum of no of RXLEV measurement above thresh old and current channel last measurement on thresh old Also set no of RXLEV measurement of best server equal to the sum of no of RXLEV measure ment of best server and current channel last measure ment of best server This step is virtually the same as repeating the reading of last measurement 0170 Step 2 3 It checks the measurement no of the last measurement If it
19. ending order of the percentage of Test Transmitter RXLEV measurement above threshold or the percentage of Test Transmitter RXLEV measurement that it is the best server 0129 Step 0 11 Again the program waits for the user s instruction if the user wants to exit the application step 0 10 is executed Otherwise the algorithm goes back to step 0 2 0130 Step 0 12 Exit the application and close the window 0131 For the second part of the algorithm this part of the algorithm is constructed for the calculation process The data used in the calculation are extracted from the selected Apis measurement file and the user entered data FIG 4 is the main body of the calculation algorithm while FIGS 5 6 and 7 are the sub procedures of the calculation algorithm 0132 Referring to FIG 4 0133 Step 1 1 Initialize all counters to 0 The counters are Total no of measurements no of RXLEV mea surement above threshold and no of RXLEV mea surement of best server 0134 Step 1 2 Initialize list of logical channel ele ments to 0 Each channel consists of five main ele ments channel description time of last measurement number of last measurement last measurement on threshold and last measurement of best server 0135 The channel description includes 0136 A link value from 1 to 4 0137 A time slot value from 00 to 31 each time slot represents data from one BTS 0138 A sub channel val
20. ensity within the vicinity of the transmitter means 0011 In a second aspect the present invention provides apparatus for assessing traffic density in a mobile cellular telecommunications system comprising Aug 23 2001 0012 a test transmitter means movable to one or more selected sites within existing telecommunica tions cells and arranged to transmit test signals to mobile stations within its vicinity which mobile stations are arranged to transmit first response sig nals to said test signals 0013 and means for analyzing received first response signals in addition to received second response signals to corresponding test signals from base stations of associated cells for assessing traffic density within the vicinity of the transmitter means 0014 The present invention is particularly preferred for use with the GSM system but other systems may be employed for example UMTS AMPS TACS NMT etc In the specification below where acronyms are used without an explanation they have the meaning assigned to them by the relevant ETSI standards for the GSM system 0015 In accordance with the invention a transmitter of low power is used so that only mobile stations MS in the vicinity of the transmitter detect the signal The nature of the test signal will naturally depend on the type of mobile system in which the invention is used since the test signals must be compatible with those received by existing base transceiv
21. er means and moving it to one or more selected sites within existing cells of the system the test transmitter means at the or each site transmitting test signals to mobile stations within its vicinity the mobile stations within the vicinity transmitting first response signals to said test signals and said mobile stations transmitting second response signals to corre sponding test signals from base stations of associated cells and analyzing received first and second response signals for assessing traffic density within the vicinity of the transmitter means 2 A method according to claim 1 wherein said test transmitter means is arranged to provide a base station of a serving cell for mobile stations in its vicinity and said associated cells constitute neighboring cells to the serving cell 3 A method according to claim 1 wherein said test transmitter means cannot receive transmissions from mobile stations and the associated cells constitute a serving cell serving the mobile stations within said vicinity and neigh boring cells to said serving cell and wherein the test transmitter means is set as a neighboring cell 4 A method according to claim 1 wherein the response signals consitute reports of received signal strength of the respective test transmitter means base station 5 A method according to claim 4 including providing analyzer means located in the interface between the base stations of associated cells and a base
22. er stations BTS As preferred the test signal is such that the mobile stations make signal strength reports constituting said first response signals at regular intervals of the type used for handover operations between cells How ever the response signals may comprise other parameters as for example the signal delay between signals transmitted from a BTS and received by a mobile station 0016 The present invention may be used for different purposes 0017 hot spot detection in order to identify the best location for micro cells typically 100 m 200 m radius or pico cells typically 50 m radius 0018 Global traffic map generation in order to predict congestion problems and plan cost effective capacity enhancements 0019 Interference area location as part of the network optimisation process 0020 Global interference map generation which could then be used in automatic frequency planning tools 0021 In a preferred form of the present invention a mobile base transceiver station BTS is used to assess the traffic in its small coverage area The mobile BTS is located in the area under study with a small coverage area low transmit power For accuracy the coverage area is checked via drive test or field strength prediction tools to determine the likely size of cell Then the traffic generated in that area is measured 0022 There are three ways of measuring the traffic 0023 1 If the mobile BTS is an
23. etermined threshold value with the second response signals to determine the value of the first response signals in relation to the second response signals 0031 In a third aspect the present invention provides a method for assessing traffic density in a mobile cellular telecommunications system by analyzing test results obtained from a test procedure involving a test transmitter making test transmissions and mobile stations within its vicinity making first response signals to said test transmis sions and second response signals to corresponding trans missions made by the base stations of associated cells 0032 received versions of the first response signals constituting a first set of test results and received Aug 23 2001 versions of the second response signals constituting a second set of test results 0033 said method for analyzing test results com prising analyzing said first set of test results to determine those first response signals which are greater than a predetermined threshold value 0034 and analyzing said second set of test results to compare those first response signals which are greater than a predetermined threshold value with the second response signals to determine the value of the first response signals in relation to the second response signals 0035 In a fourth aspect the invention provides appara tus for assessing traffic density in a mobile cellular tele communications system by analyzin
24. following techniques loca tion of existing BTSs that become congested during busy hours visual inspection of maps showing areas of increased usage e g shopping centers comparison of above maps with coverage predictions from existing BTS sites etc 0048 Once an initial attempt has been made to identify hot spot locations a number of possible test positions are identified Several test positions S1 Sj are selected within each of the broad hot spot areas manually identified above One at a time at each of the test sites test transmitter 8 is installed The preferred test transmitter 8 is small light weight battery powered and can use an integral antenna it is normally easy to use at the majority of test sites At sites that require an output power no more than 0 5 W the test transmitter can be mounted on a lightweight tripod and the internal antenna and battery used If greater output power is required an external power amplifier can be used together with an external antenna system At sites where greater antenna heights are required either a transportable mast or rooftop location can be used 0049 In order to record measurement results the test transmitter 8 is positioned at the first test site S1 and switched on The A Protocol Analyzer 14 is set recording data for a period that is typically of the order of half an hour As the data is recorded the measurement results are dis Aug 23 2001 played on the A
25. g test results obtained from a test procedure involving a test transmitter making test transmissions and mobile stations within its vicinity making first response signals to said test transmissions and second response signals to corresponding transmissions made by the base stations of associated cells 0036 received versions of the first response signals constituting a first set of test results and received versions of the second response signals constituting a second set of test results 0037 said apparatus comprising means for analyz ing said first set of test results to determine those first response signals which are greater than a predeter mined threshold value and 0038 means for analyzing said second set of test results to compare those first response signals which are greater than a predetermined threshold value with the second response signals to determine the value of the first response signals in relation to the second response signals 0039 In a preferred embodiment received versions of the first and second response signals are forwarded from base stations to a BSC and an A protocol analyzer analyses the response signals to determine for each MS making responses whether a first response signal is present in a predetermined number say 6 of the response signals having the largest values If present the first response signal is compared with a threshold value usually the minimum acceptable field strength value
26. ginning of a for loop It is the loop used to check if the test transmitter is in the top six of the neighbor cell list of the MS i e the six neighbor cells with the highest RXLEV 0177 Step 3 2 When i56 it means that the test trans mitter is not in the top six of the neighbor cell list Therefore go to step 3 17 the exit stage of the loop 0178 Step 3 3 The NCC and BCC the BSIC and the BCCH index if used of the neighbor cells are US 2001 0016490 A1 checked If they are the same as the test transmitter this means the test transmitter is found and step 3 5 will be taken If they are not the same test transmitter is not found and step 3 4 will be taken 0179 Step 3 4 Since neighbor cell i is not the test transmitter check the next neighbor cell on the list Hence increase the i counter by 1 0180 Step 3 5 Since the test transmitter is found set the variable Test Transmitter found to TRUE 0181 Step 3 6 It compares the RXLEV level of the neighbor cell i test transmitter with the threshold level It notes that the correction factor is added onto the RXLEV value before it is compared with the threshold value If the RXLEV value is higher than the threshold goes to step 3 8 If it is lower goes to step 3 7 0182 Step 3 7 Set both Current Channel last mea surement on threshold and last measurement of the best server to 0 This is because the measured test transmitter RXLEV leve
27. ia seconds 96 of Test Transmitter RXLEV measurements are the best server 100 no of RXLEV measurements of best server total no of measurements Call time in Test Transmitter are the best server no of RXLEV measurements of the best server 0 48 seconds FIG contd US 2001 0016490 A1 TRAFFIC LOCATION IN MOBILE CELLULAR TELECOMMUNICATIONS SYSTEMS CROSS REFERENCE TO RELATED APPLICATION 0001 This application claims priority of European Patent Application No 99310353 0 which was filed on Dec 21 1999 0002 The present invention relates to the location of traffic in particular regions of increased traffic density in mobile cellular telecommunications systems 0003 When a new network operator is licensed and the network designed the radio base stations are usually planned on the basis of providing maximum coverage with relatively low traffic capacity In this way the new service is made available to the maximum number of possible con sumers as rapidly as possible while minimizing the initial capital outlay The radio network planning at this stage is satisfactorily performed with a combination of manual field strength surveys from test transmitters and automatic cov erage prediction and frequency assignment software 0004 Once the new network s subscriber base grows it becomes necessary to add traffic capacity often in the form of additional base station sites It is at this stage that it i
28. l is lower than the threshold and hence it could not be the best server 0183 Step 3 8 The measured test transmitter RXLEV is higher than the threshold level so increase the no of RXLEV measurement above threshold counter by one For the same reason set the current channel last measurement on the threshold to 1 The test transmitter best server is set to FALSE 0184 Step 3 9 Before comparing the measured RXLEV of the test transmitter with the RXLEV of the serving cell the status of the DTX downlink has to be known If it is ON the measured RXLEV of the test transmitter is compared with the serving cell RXLEV sub value that is done in step 3 10 If DTX is OFF then the measured RXLEV of the test transmitter is com pared with the serving cell RXLEV full value that is done in step 3 13 0185 Step 3 10 If the DTX downlink is ON the serving cell RXLEV sub is used in the comparison between the RXLEV of the test transmitter and of the serving cell If the RXLEV of the test transmitter is higher step 3 11 is the next step or else step 3 12 is the next step 0186 Step 3 11 If the test transmitter has a higher RXLEV set Test Transmitter best server to TRUE 0187 Step 3 12 If the test transmitter has a lower RXLEV set Test Transmitter best server to FALSE 0188 Step 3 13 If the DTX downlink is OFF so the serving cell RXLEV full is used in the comparison between the RXLEV of the test transmitte
29. o 1 10 Increment total no of measurements counter Yes measurement already exist 1 12 Found Channel Current Channel No 1 13 Create new Channel in list New Channel Current Channel FIG 4 conta US 2001 0016490 A1 Patent Application Publication Aug 23 2001 Sheet 7 of 13 l SIQV ul play PIILA 81 i PW OJy Jequinu juawelnseau XIUeureseeui ISB jo 19QUINU jeuueuo juan aun juawainsgaw JAUBWSINSBOW jse jo eum Jeuueu juaun 8rL 0109 ZEL Josle4 puno Japiwusuei 1591 j GEL PIIeA ueuaJnseaui s PIL 2 0100 911 NA PS AG CELL EE ea MP Patent Application Publication Aug 23 2001 Sheet 8 of 13 US 2001 0016490 A1 Algorithm 2 FIG 5 number gt 0 Is Current Channel no of last measurement Yes 2 2 Update Channel data A 2 4 Update Channel data B Current Channel time of last measurement gt 700 mSec 2 6 Update Channel data B 2 7 Update Channel data A Finish Channel data A No of RXLEV measurements above threshold no of RXLEV measurements above threshold current channel last measurement on threshold No of RXLEV measurements of best server no of RXLEV measurements of best server current channel last measurement of best server Channel data B e Current Channel last measurement on threshold
30. of test transmitter identification 0091 Using a unique Network Color Code NCC element of the BSIC number assigned to the test transmitter and entering it in the HSD software New Test Transmitter dialogue box 0092 Entering the test transmitter BCCH FREQ N CELL i value associated with the ARFCN that is used by the test transmitter in the HSD software New Test Transmitter dialogue box 0093 BSC 12 Software 0094 The BSC software has to be configured such that the existing BTS in the test area broadcast the identification information relating to the test transmitter to mobiles in the area Aug 23 2001 0095 For mobiles in the vicinity of the test transmitter to include signal level measurements for the test transmitter in their measurement reports to their serving cell it is neces sary for the test transmitter to be included as a neighbor cell in the BA list transmitted by the serving cell 0096 This is achieved by making the following changes 0097 Create a new dummy BTS to represent the test transmitter together with its associated Handover Con trol Object and Power Control Object 0098 Modify the neighbor cell lists broadcast by the existing BTSs in the test area to include the dummy BTS as a valid neighbor cell 0099 HSD Software 16 0100 Referring to FIG 2 this shows one the new test transmitter dialog interface window of various windows comprising the interface between th
31. oks at the command that the user gave If the user wants to start the calculation the algorithm goes to step 0 4 otherwise to step 0 9 0122 Step 0 4 The data entered from the user is checked If the entered data is out of range or is missing the algorithm goes to step 0 5 otherwise to step 0 6 0123 Step 0 5 Displays the error message 0124 Step 0 6 The program carries out the calculation using the selected measurement file and the information entered by the user The detail of this procedure is shown in second part The result are available for the next step 0125 Step 0 7 The result of the calculation the percentage of Test Transmitter RXLEV measurement Aug 23 2001 above threshold the percentage of Test Transmitter RXLEV measurement that it is the best server and the call time for each case is saved in an output file The output file also includes the user entered data and the extracted data from the input file 0126 Step 0 8 If the user has to processed more than one Abis file the results of these files are compared automatically Therefore if the result is the first set of output the algorithm goes back to step 0 2 otherwise to step 0 7 0127 Step 0 9 The result of current set of measure ment is compared with the pervious output data 0128 Step 0 10 The results of different test transmitter measurements are displayed in order according to user s choice This could be in ascending or desc
32. on Publication Aug 23 2001 Sheet 3 of 13 FIG 3 0 1 Open program main display window 0 2 Wait for the user to select data txt file to start the calculation 0 4 Is the data entered from user valid 0 5 Display error message Yes 0 6 Goto 1 0 7 Save the results in the output file US 2001 0016490 A1 No Patent Application Publication Aug 23 2001 Sheet 4 of 13 0 8 Is it the first set of results 0 9 Compare the current results with other sets of results 0 10 Display the results in order according to the user s choice 0 11 Is the user wanted to exit Yes 0 12 Close the window FIG 3 conta US 2001 0016490 A1 Patent Application Publication Aug 23 2001 Sheet 5 of 13 US 2001 0016490 A1 FIG 4 Algorithm 1 1 1 Initialise Counters to 0 1 2 Initialise list of logical channel elements to 0 1 3 Read and store the user s input data 1 4 Read Abis txt file 1 5 Search Abis file for event which has Measurement Result 1 6 Is event found No Yes 1 19 Measurement Result event not found Go to END PROCEDURE 1 7 Extract and Store data from Abis file measurement Yes Patent Application Publication Aug 23 2001 Sheet 6 of 13 US 2001 0016490 A1 1 8 Is time before start time Yes No 1 9 Is time after finish time Yes N
33. ording to claim 16 including analyzer means for locating in the interface between the base stations of associated cells and a base station controller for recording the response signals Aug 23 2001 18 Apparatus according to claim 17 wherein said means for analyzing comprises means for analyzing said first received response signals to determine those first response signals which are greater than a predetermined threshold value and means for comparing those first response signals which are greater than a predetermined threshold value with the second response signals to determine the value of the first response signals in relation to the second response signals 19 Apparatus for assessing traffic density in a mobile cellular telecommunications system by analyzing test results obtained from a test procedure involving a test transmitter making test transmissions and mobile stations within its vicinity making first response signals to said test transmissions and second response signals to corresponding transmissions made by the base stations of associated cells received versions of the first response signals constituting a first set of test results and received versions of the second response signals constituting a second set of test results said apparatus comprising means for analyzing said first set of test results to determine those first response signals which are greater than a predetermined thresh old value and means
34. r and of the serving cell If the RXLEV of the test transmitter is higher step 3 14 is the next step or else step 3 15 is the next step 0189 Step 3 14 Same as step 3 11 0190 Step 3 15 Same as step 3 12 0191 Step 3 16 Go to 4 The sub procedure 4 is run to verify the test transmitter is the best server among other neighbor cells Aug 23 2001 0192 Step 3 17 The exit of the for loop 0193 Step 3 18 It examines the status of the variable Test Transmitter found if it is FALSE i e no test transmitter is found step 3 19 is the next step If not the algorithm will go to the finish step of the sub procedure 0194 Step 3 19 Same as step 3 7 0195 Referring to FIG 7 the aim of this sub procedure is to examine the measured RXLEV of the test transmitter with other neighbor cells measured RXLEV Again the correction factor is added on the RXLEV of test transmitter before carrying out any comparison 0196 Step 4 1 It makes sure that the Test Transmitter best server is equal to TRUE If it is true then goes to step 4 3 or else goes to step 4 2 0197 Step 4 2 If the test transmitter is not the best server sets the last measurement of best server to O 0198 Step 4 3 The beginning of the for loop It is used to examine the RXLEV of the test transmitter with the rest of neighbor cells in the list 0199 Step 4 4 If j is larger than 6 exits the loop by going to step 4
35. s necessary to identify areas of traffic congestion and target the provision of new base station sites in these areas Thus the location of regions of increased traffic density or hot spots is an important problem particularly for the siting of base transceiver stations BTS to accommodate the traffic Many such hot spots can be identified by careful analysis of geographical morphological data and good knowledge of the area However there remains a great interest in the automation of such process 0005 It is an object of the present invention to provide a method and means for automatically assessing the traffic density in geographical regions in a mobile cellular tele communications system 0006 In a first aspect the present invention provides a method for assessing traffic density in a mobile cellular telecommunications system the method comprising 0007 providing a test transmitter means and mov ing it to one or more selected sites within existing cells of the system 0008 the transmitter means at the or each site transmitting test signals to mobile stations within its vicinity 0009 the mobile stations within the vicinity trans mitting first response signals to said test signals and said mobile stations transmitting second response signals to corresponding test signals from base sta tions of associated cells 0010 and analyzing received first and second response signals for assessing traffic d
36. s greater than the corre sponding second response signals by a time constant repre senting the interval between said first response signals for a single mobile station
37. second response sig nals for assessing traffic density within the vicinity of the transmitter comprising analyzing the received first signal strength response signals to determine those first response signals which are greater than a predetermined threshold value and comparing those first response signals which are greater than a pre determined threshold value with the second signal strength response signals to determine the value of the first response signals in relation to the second response signals Patent Application Publication Aug 23 2001 Sheet 1 of 13 US 2001 0016490 A1 US 2001 0016490 A1 Patent Application Publication Aug 23 2001 Sheet 2 of 13 unsay Mel t senjeA ngad isay man L_Junwiy __ oesw O 206 O u 7 i4 aw ysiuis _Juoserera 29gw 988 UN JH Owl uelis 94 601 5589014 al oes um Lsa ui Tov rubieH LJ Js Jew somo al euo MAIL L Joss Jun Je LL Je a Joaeausius aj Jams SISA BUY U0REJ07 buoqje euuajuy eun juewainseay uonoejes uodn sp a1y IJE ui 18114 eui tual pe uogosuog omoa peyeindog senpeA Nead pueweinsee 7 wae re e1 prouseuyy uognoejes uodn wep aua pessaooJg 9 14 9OINOS L Kouenba14 HIDE JO NOJHY C H NeoN bes 4908 CI JOU JIN L L oss uonoejeg uo Si9 9weJeg sis jeuy pelealO SPI IV 819H POMBIA SI9INOS doen sJeeuifu3 C 19qUINN G i Japiusue Se nom LT lanas owe usual elty Bo siqy 191 1USURI ISO M N c Ul Patent Applicati
38. station and or wherein a further time of transmission value is obtained by multiplying the number of those first response signals greater than the corresponding second response signals by a time constant representing the interval between said first response signals for a single mobile station 14 Apparatus for assessing traffic density in a mobile cellular telecommunications system comprising a test transmitter means movable to one or more selected sites within existing telecommunications cells and arranged to transmit test signals to mobile stations within its vicinity which mobile stations are arranged to transmit first response signals to said test signals and means for analyzing received first response signals in addition to received second response signals to corre sponding test signals from base stations of associated cells for assessing traffic density within the vicinity of the transmitter means 15 Apparatus according to claim 14 wherein said test transmitter means is such that it cannot receive transmis sions from mobile stations and the associated cells consti tute a serving cell serving the mobile stations within said vicinity and neighboring cells to said serving cell wherein the test transmitter means is set as a neighboring cell 16 Apparatus according to claim 15 wherein the response signals consitute reports of received signal strength of the respective test transmitter means base station 17 Apparatus acc
39. t transmitter set up is given below 0065 Frequency Correction Channel FCCH 0066 The Absolute Radio Frequency Channel Number ARFCN is set to a channel that the existing network operator is licensed to use and is not simultaneously in use in the vicinity of the test site 0067 Synchronization Channel SCH 0068 The SCH carries the Base Station Identity Code BSIC 0069 It comprises two octal digits First the Network Color Code NCC which is set to that of the existing network Second the Base station Color Code BCC which can be set to a number that identifies it from the surrounding base stations in the test area 0070 Broadcast Control Channel BCCH 0071 The BCCH carries the Global Cell Identity GCI number that is comprises two elements Cell Identity CT Location Area Identity LAT that is itself formed from three numbers Mobile Country Code MCC Mobile Network Color Code MNCC and Location Area Code LAC US 2001 0016490 A1 0072 Transmit Power 0073 The test transmitter output power is set accord ing to the coverage range that is required and the type of external power amplifier that may be used 0074 The output power takes a value within the range 20 to 27 dBm 2 5 dB 0075 The required transmit power can be estimated by 0076 0077 Using coverage prediction software and field strength measurement results if available to estimate the field strength th
40. time is after the finish time that specified by the user then go back to step 1 19 otherwise go to step 1 10 0157 Step 1 10 Step 1 8 and 1 9 ensured that the measurement is within the time period that is specified by the user Therefore increment total no of measure ments counter 0158 Step 1 11 Check the U channel type of the channel description of the current measurement with the previous channel If they are the same this means that channel of measurement is already existing and go to step 1 12 Otherwise go to 1 13 0159 Step 1 12 Store the found channel information in the current channel 0160 Step 1 13 Create a new channel and store the information of the new channel in the current channel The new channel has the same channel description as the measurement channel Other channel parameters including time of last measurement number of last measurement last measurement on threshold and last measurement of best server are set to 0 0161 Step 1 14 Check the validation status of the measurement If the measurement is valid step 1 15 will be taken otherwise step 1 16 is the next step 0162 Step 1 15 The variable Test Transmitter is set to FALSE 0163 Step 1 16 Goto 2 the sub procedure 2 is executed in the case that the measurement is Not Valid 0164 Step 1 17 Goto 3 the sub procedure 3 is executed in the case that the measurement is Valid 0165 Step 1 18 The current chann
41. ue from 0 to 3 0139 U time slot value from 1 to 7 U is the air interface 0140 U channel type Bm ACCH or SACCH 8 or SACCH 4 0141 U sub channel if channel type is Bm ACCH and the number does not appear it should set to 0 otherwise value from O to 7 0142 Step 1 3 Read the data entered from the user and store them in program variable 0143 Step 1 4 Read A txt file which is selected by the user US 2001 0016490 A1 0144 Step 1 5 Search A file for the event Mea surement Result The phrase Measurement Result indicates the beginning of a new measurement i e search for a new measurement 0145 Step 1 6 If event found then go to step 1 7 else got to step 1 19 0146 Step 1 7 Read and extract data from A file measurement 0147 The extracted data consist of 0148 The measurement time 0149 The channel description 0150 The measurement number 0151 The DTX downlink status DTX represents voice operated switch control for the MS 0152 The measurement valid 0153 The serving cell RXLEV full and sub 0154 The top six neighbor cells information in terms of signal strength measurements For each neighbor cell the value of RXLEV BCCH NCC and BCC are recorded 0155 Step 1 8 If the measurement time is before the start time that specified by the user then go back to step 1 5 otherwise go to step 1 9 0156 Step 1 9 If the measurement
42. ve the user entered signal level threshold 0209 The time in seconds within the analysis time window for which the test transmitter received signal level plus user entered power correction factor is above the user entered signal level threshold US 2001 0016490 A1 0210 Each measurement report accounts for approxi mately 0 48 s 0211 The percentage of measurement reports within the analysis time window for which the test transmitter received signal level plus user entered power correc tion factor is 0212 Above the user entered signal level threshold and 0213 Is the best server i e is received at a higher level than either the serving or neighbor cells 0214 The time in seconds within the analysis time window for which the test transmitter received signal level plus user entered power correction factor is 0215 Above the user entered signal level threshold and 0216 Is the best server i e is received at a higher level than either the serving or neighbor cells 0217 The following points should be considered when the HSD results are analyzed 0218 The Call Seconds values can only be used for comparison purposes if either 0219 The A Protocol Analyzer log files were recorded over the same length of time and the whole file is analyzed or 0220 The HSD analysis time window is set to extract the same length of time from each A Protocol Ana lyzer log file pro
43. vided that each log file is longer than the period used for the time window 0221 The Call Seconds value can be used to gain a good indication of the volume of traffic that could be served from each test site 0222 The Percentage value can be used to check how well the test site compares with the current serving site 0223 The Best Server values can be used as an indication as to the extent to which traffic would be switched to the test site however it should be borne in mind that 0224 The test transmitter EIRP and Power Correction Factor must be set such that the test site is representa tive of an actual BTS installed at the site 0225 The power threshold level is set at the required received power level for the service area 0226 If the test transmitter antenna position is not the same as that of the intended BTS installation the coverage will differ to some extent even though the power correction factor may be applied 0227 Modifications may be made to the preferred embodiment as follows 0228 Support the use of multiple test transmitters 0229 Dual band operation with two transmitters at one location 0230 Multiple transmitters at different locations Aug 23 2001 0231 Analyze the effect of selecting multiple new BTS sites 1 A method for assessing traffic density in a mobile cellular telecommunications system the method compris ing providing a test transmitt
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