Abstract:
Telecommunication system in which local terminals may be called from one or more central stations by way of transmission paths selected by selection device on the probability of success. Selection takes place with the help of selection tables on the basis of exchanged signalling messages obtained from, or by way of, a switching system (3); other selection tables are also possible, e.g., on the basis of geographic or cartographic information. To the transmission paths there are assigned scores on the basis of the points in time of successful and unsuccessful calls, and of numbers of successful calls. During a session, a call is first made by way of the transmission path having the highest score (S(ok), S(nok) or S(rc)) in one of the selection tables (OK, NOK and RC, respectively). In the event of failure, the call is repeated by way of a preferred transmission path (PP), once again in sequence of the scores from one of the selection tables. If these calls are unsuccessful as well, the other transmission paths are tested, once again in sequence of the scores (S(ok), S(nok) or S(rc)) from one of the selection tables (OK, NOK and RC, respectively). Transmission paths for which it is a short while ago (e.g., less than 5 minutes) that an unsuccessful call took place, are not used. All this is useful, inter alia, for Inmarsat, GSM, UMTS and UPT.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a telecommunication system in which local users are capable of being called from one or more central stations by way of transmission paths selected by selection means. 
     An example of such telecommunication system is a cellular system, such as the GSM system or the future Universal Mobile Telecommunication System (UMTS). The transmission paths comprise base stations which each take care of one local region. 
     Another example is the current Inmarsat system, in which there are included, in the transmission paths, satellites which each serve one region of the earth&#39;s surface. 
     In this type of system, there is a specific uncertainty as to the location where the users are, and therefore also as to the transmission path which must be chosen to be capable of reaching a user. 
     In the GSM system, there are routed calls by way of the transmission path which runs by way of the local base station where the user was most recently registered. To minimise the uncertainty regarding the user location, it is necessary that the user call regularly by having his mobile terminal regularly transmit a code. In the event of &#34;pocket telephones&#34;, the transmission of such code requires a relatively great deal of battery power, as a result of which the battery must be recharged regularly. 
     In the Inmarsat system, so far calls are routed to the (four) regions on the basis of the region indicated by the calling party. If a call is unsuccessful, the call is repeated in one, two or three other regions. In practice, all of this turns out to lead to many calls being unsuccessful. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to improve the routing of calls by, on the basis of the system signalling, which may be derived from the system, prior to a call to a local user calculating a selection order, according to the probabilities per transmission path that the call is answered by the local user. Thereafter, the local user is called, by way of transmission paths, in descending probability order, until the call is answered. 
     The invention is suitable for use in transmission systems having mobile terminals, such as Inmarsat, GSM and UMTS, but also for systems, such as the UPT system, in which a user, sequentially or simultaneously, at various terminals, mobile or non-mobile, may choose domicile by having himself registered from there at the system server. In the event of such a system, where the user terminal is logically mobile, the same problem applies regarding the uncertainty of the user location as in systems where terminals are physically mobile. 
     In accordance with the invention, it is calculated by way of which transmission path the local user may best be called, with the highest probability of success. If a call by the local user is not answered, another transmission path having a lower probability of success is chosen. 
     The selection order is preferably calculated by means of one or more selection tables which each comprise a designation of the reply probabilities per transmission path. Said selection tables are the result of registrations, in the central stations, of code signals transmitted to, or received from, the local users. The use of various selection tables is based on the insight that the best reply probability is the resultant of an order of various factors which may be derived (inter alia) from the signalling of the transmission system. 
     A first selection table is formed, e.g., using the recentness of the points in time, registered in the central stations, of code signals which were received from the local user by way of the various transmission paths. From the user, there is received a (signalling) code signal when the user has himself registered in the system, or in response to a call to said user. In either case, the more recent the received code signal, the greater the possibility that the user (still) is in the region which is served by the same transmission path. It is therefore logical, in the event of a new call to the user, to first use the transmission path by way of which a code signal was most recently received from the user. 
     If, after receipt of a code signal from the user, there is made a call which is not answered, however, it is logical to assume that the user is no longer in the region which is served by the transmission path. The observation that the user does not answer a call by way of a certain transmission path, minimises the probability that a new call by way of that same transmission path will be answered. Said probability, however, grows again as time elapses: if the failure of the call occurred a considerable time ago, a new call again has a fair chance of being answered. In order therefore to be capable of correcting, by negative observations, the positive observations regarding the accessibility of the user, which are ranked in the first selection table, there may be formed a second selection table using the recentness of the points in time registered in the central stations of code signals which were sent to the local user by way of the various transmission paths, but which, as shown by the absence of the receipt, within a certain period of time, of a code signal in response thereto, were not answered by the local user. 
     The first selection table and the second selection table may be used as each other&#39;s opposites: a positive observation erases the effect of an earlier negative observation, while a negative observation annuls the effect of an earlier positive observation. In addition, the effect of each observation decreases as time elapses; in other words, a recent observation prevails over a less recent observation. Combination of both selection tables amplifies the surmise of the region or location where the user is and, by selecting said region or location, increases the probability of a reply. 
     Still further observations, ranked and laid down in further selection tables, may improve the selection process. 
     Thus, a third selection table may be formed using the numbers, registered in the central stations, of code signals per transmission path originating from the local user. In this connection, therefore, as a selection criterion there is used the number of times that the user logged on to the system by way of the various transmission paths, either of his own accord or as a result of a call from the system. It is logical to assume that, definitely if further designations are lacking, the probability of a reply to a new call is greatest in a region from which the user has been the most active so far. Incidentally, in this connection, too, it is desirable to assign a greater weight to more recent registrations than to registrations carried out longer ago. 
     Yet another, fourth selection table may be formed by a table in which for each region the adjacent regions are designated. The logic in the use of said table, as in selecting regions having a good reply probability, is the assumption that a user --  if a call is still unsuccessful in one region where the user, as is shown by recent observation, recently was --  will then be in an adjacent region. Particularly for large regions, such as in the event of Inmarsat, this is a sound assumption. An extension --  which is particularly useful for systems having small regions --  is to construct a probable path followed by the user through the regions using consecutive observations, it being possible to obtain the region in which the user will probably be, by extrapolation. During said extrapolation, cartographic data may also be used: there may be taken account of, e.g., the course of roads and the like. In general, therefore, after a call by way of the path having the highest probability score still was unsuccessful, a next call is preferably made by way of a path which, based on logical considerations regarding user movements, has the greatest probability of success. Below, in this connection there will be referred to &#34;preferred transmission paths&#34;, with each transmission path having one or more preferred transmission paths. 
     The various selection tables, which all offer a certain designation with respect to the probability of success, may be combined with one another in various ways and in various orders. During a session, a call is first made by way of the transmission path having the highest score in the first, second or third selection table. In the event of failure, the call may be repeated by way of a preferred transmission path as laid down in the fourth selection table, in sequence of the scores from the first, second or third selection table. Should said calls be unsuccessful as well, the remaining transmission paths are tested, again in sequence of the scores from one of the selection tables. Transmission paths for which it is a short while ago (e.g., less than 5 minutes) that an unsuccessful call took place, are not used. In the next paragraph, several options are discussed. 
     REFERENCES 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Below, the invention will be explained in greater detail by reference to FIG. 1, in which the link is shown between a fixed terminal and a mobile terminal, partly by way of the fixed network, partly by way of a satellite link. Furthermore, the construction of the selection order of calls will be discussed by reference to a number of selection tables. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a terminal 1, connected to a telecommunication network 2. By way of an intelligent switching system 3, a call may be made to a mobile user terminal 6 by way of earth stations 4 (one of which is shown in the drawing) and a system of (in the event of Inmarsat four) satellites 5. In the switching system 3, there is chosen, using various data collected there, the transmission path (earth station-satellite) whose probability that the call is answered by the local user 6, is greatest. By way of the switching system 3, the signalling messages (code signals) exchanged between the user terminal 6 and the earth station 4 (by way of the satellites 5) are continuously tapped, and stored in a data base 7. The switching system 3 is capable of receiving and registering and storing the code signals exchanged by all earth stations 6. 
     In the data base of the switching system 3, per terminal 6, for each transmission path separately there is stored: 
     OK: the point in time on which a code signal was received from the mobile user terminal 6 for the last time, whether or not in response to a call from the earth station 4; 
     NOK: the point in time on which, as shown by the failure of a code signal forthcoming from the user terminal 6 in response to a call from the earth station 4, an unsuccessful call was made to the terminal 6 for the last time; 
     RC: the total number of times that, over a certain period of time, a code signal was received from the terminal. To said value, there may be applied &#34;exponential smoothing&#34;, as a result of which the effect of older annotations is reduced, to the benefit of more recent registrations. This may be achieved by periodically dividing the RC value by a constant value &gt;1. 
     Prior to a new call, said variables are used for calculating a region order relating to the probability of success of said new call. In said calculation, there are also involved the regions which physically adjoin the region in which a successful call took place most recently. 
     Below, there follow three examples of a calculation of the transmission-path order for four transmission regions. Subsequently, a fourth example will present an identical calculation for a greater number of transmission paths. The meaning of the abbreviations used is: 
     
         ______________________________________PN =   path number; an * denotes the path having the highest CS(ok)  score;OK =   the most recent point in time, counted from t = 0, on which  a code signal was received from the user terminal 6;S(ok) =  score based on OK times;NOK =  the point in time on which a call to the terminal was  unsuccessful;S(nok) =  score based on NOK times;CS(ok) =  score based on OK times, however corrected using the NOK  times;PP(##) =  preferred paths, associated with the path having the highest  RS(ok) score;RC =   total responses received per path of the terminal;S(rc) =  score based on RC values;CPO =  calculated path order.______________________________________ 
    
     The steps followed are: 
     1. Rank the paths using the OK times; the more recent the OK times, the higher the score (S(ok)). 
     2. Investigate for all paths whether the NOK time is shorter than the OK time; in that case the score becomes 0 (CS(ok)). 
     3. Rank the paths using the NOK times; the longer the NOK times, the higher the score (S(nok)). 
     4. If after step 2 all scores are equal to 0, the scores (CS(ok)) are made equal to the scores from step 3; otherwise, the score remains as it was determined in steps 1 and 2. 
     5. Determine the preferred paths (PP(##)) of the path having the highest score. 
     6. Rank the preferred paths using the numbers of responses received (S(rc)). 
     7. The calculated path order (CPO) is: the path having the highest score determined in steps 1, 2 and 4, and then the preferred paths, ranked as in step 6. 
     After the examples below, a similar, yet improved method will be presented. 
     EXAMPLE 
     
         ______________________________________   OK     NOKPN      in s.  in s.    RC  S(ok)  S(nok)                                    CS(ok)______________________________________0       -446   -276     2   2      0     0*1      -111   -822     81  3      2     32       -481   -809     34  1      1     13       -853   -829     24  0      3     0______________________________________PP(1)   RC     S(rc)______________________________________3       24     02       34     1______________________________________ CPO: 1-2-3 
    
     The operation is as follows: 
     From the data base of the switching system 3 there are derived, per terminal 6, for the transmission paths 0 . . . 3, the points in time on which a code signal was received from the user terminal 6 for the last time, either because the terminal 6 was registered by way of said path, or as a reaction to a call by way of that path. The shorter the time elapsed since the terminal emitted a code signal, the greater the probability that the terminal will be accessible by way of the same channel; therefore, the shorter the OK time, the higher the accessibility score shown under S(ok). 
     From the data base of the switching system 3, there are also derived, per terminal 6, for the transmission paths 0 . . . 3, the points in time on which an unanswered call was made to the user terminal 6 for the last time. The shorter the time elapsed since the terminal evidently was not accessible, the greater the probability that the terminal will not be accessible either by way of the same channel; therefore, the shorter the NOK time, the lower the accessibility score, shown under S(nok). 
     If for a certain path at a certain moment (OK time) there proved to be contact with the terminal, but thereafter the terminal proved to be no longer accessible (NOK time), the effect of the OK time is annulled by the (more recent) NOK time. The OK scores are thus corrected: the scores S(ok) of the paths for which the absolute value of the NOK time is less than that of the OK time, are set to 0. In the above example, such is the case for path 0, there having been contact with the terminal 446 seconds ago, resulting in an OK score of 2 with respect to the other paths. Since, however, 276 seconds ago, due to an unsuccessful call to the terminal by way of said path 0, the terminal proved no longer accessible by way of path 0, the OK score is returned to 0 (see under CS(ok)). It may occur that in this manner all OK scores must be corrected to 0, as is the case in example 3 below. In this case, the score is determined using the NOK times; after all, the OK times no longer offer any basis for calculating the greatest accessibility probability. 
     When the terminal 6 is called, the path having the greatest (corrected) score CS(ok) --  path 1 in example 1 --  has the greatest probability of success. In the event, however, that the call still were to be unsuccessful, the call is repeatedly emitted by way of a path which has a special relation to path 1. Thus, it is logical to assume that the terminal, after an unsuccessful call by way of the most probable path 1, or by way of the path which ends in an adjacent region, will be accessible. In example 1, said preferred paths PP(1) of path 1 are the paths 3 and 2. 
     The order in which said alternative paths 3 and 2 will be used is calculated using the total numbers of (successful) links which in the past have taken place between the switching system 3 and the terminal by way of said paths 3 and 2. Having said this, such order may also be derived from one of the other tables, e.g., the OK table. In the column RC there is shown, for all paths, the total number of links. From this, there prove to have been 24 links by way of path 3, and 34 links by way of path 2. It is logical to assume that the probability of connection by way of path 2 is greater than by way of path 3; path 2 therefore scores higher than path 3. 
     The calling sequence (CPO) therefore becomes: path 1 --  path 2 --  path 3. 
     EXAMPLE 
     
         ______________________________________   OK     NOKPN      in s.  in s.    RC  S(ok)  S(nok)                                    CS(ok)______________________________________0       -600   -667     57  0      2     01       -322   -227     37  3      1     02       -591   -202     1   1      0     0*3      -445   -922     42  2      3     2______________________________________PP(3)   RC     S(rc)______________________________________1       37     12       1      0______________________________________ CPO: 3-1-2 
    
     Example 2 shows the result of the calculation method according to the invention for other input variables (OK, NOK, PP(##) and RC). In this example, the highest OK score --  for path 1 --  is annulled by an NOK time ( --  227) which is more recent than the OK time ( --  322). As a result, to path 3 there is assigned the highest probability of success for a call to the terminal. The preferred paths of path 3 are the paths 1 and 2, of which path 1 in total has the most switching system/terminal links to its credit (37). The call order therefore becomes path 3 --  path 1 --  path 2. 
     EXAMPLE 
     
         ______________________________________   OK     NOKPN      in s.  in s.    RC  S(ok)  S(nok)                                    CS(ok)______________________________________0       -852   -305     64  1      2     2*1      -910   -894     18  0      3     32       -481   -293     57  3      1     13       -574   -261     51  2      0     0______________________________________PP(1)   RC     S(rc)______________________________________2       57     00       64     1______________________________________ CPO: 1-0-2 
    
     In example 3, the phenomenon occurs that for all four paths the NOK times are more recent than the OK times, as a result of which a score based on the OK times is not possible. In this case, therefore, use is made of the NOK times for determining the path having the greatest chance of success. Based on the NOK times, path 1 receives the highest score (see under S(nok)). Thereafter, the operation again takes place in the same manner: of path 1, the preferred paths are determined (2 and 0) of which the score is then determined on the basis of the RC values. The result is the path order 1-0-2. 
     Finally, shown below is example 4, generated in the same manner as the previous examples, applied however to a transmission system in which basically links by way of 25 different paths may be set up with the same terminal 6. In this example, it has been taken into account that each path has four preferred paths. 
     
         ______________________________________   OK     NOKPN      in s.  in s.    RC  S(ok)  S(nok)                                    CS(ok)______________________________________ 0      -486   -268     75  13     6     0 1      -809   -711     4   4      17    0 2      -861   -528     9   2      13    0 3      -116   -772     37  23     20    23 4      -981   -514     71  1      12    0 5      -378   -584     87  16     15    16*6      -8     -296     75  25     8     25 7      -691   -916     24  9      24    9 8      -447   -923     84  14     25    14 9      -221   -335     45  19     9     1910      -409   -627     35  15     16    1511      -592   -35      70  11     1     012      -128   -269     96  22     7     2213      -524   -912     90  12     23    1214      -723   -50      84  7      2     015      -729   -897     97  6      22    616      -218   -462     18  20     10    2017      -47    -529     46  24     14    2418      -808   -488     81  5      11    019      -841   -787     35  3      21    020      -368   -57      40  17     3     021      -633   -165     94  10     5     022      -227   -749     14  18     19    1823      -996   -3       28  0      0     024      -178   -747     13  21     18    2125      -698   -64      44  8      4     0______________________________________PP(6)   RC     S(rc)______________________________________ 2      9      1 1      4      0 3      37     2 5      87     3______________________________________ CPO: 6-5-3-2-1 
    
     Below, there is given a modified method of calculating the path order. The steps thereof are: 
     1. Rank the paths using the OK times; the more recent the OK times, the higher the score (S(ok)). 
     2. Of the path having the highest score, determine the preferred paths (PP(##)). 
     3. Rank the preferred paths using the numbers of responses per path (S(rc)). 
     Remark: The preferred paths might be ranked once again using the OK times, or possibly using preferences designated by the calling subscriber (this remark also applies to the previous method). 
     4. Rank the remaining, non-preferred paths using the response numbers (or OK times). 
     5. Determine whether there are recent NOK times (in the examples below less than 300 s.). 
     6. The path order then becomes: the path, selected under 1, having the highest OK score; then ranked preferred paths; and finally the non-preferred paths, it being understood that paths having recent NOK times are ruled out. Should all transmission paths be ruled out as a result, the entire procedure is repeated from step 1. 
     Processing the first example using these steps leads to the following result. 
     EXAMPLE 
     
         ______________________________________     OK     NOKPN        in s.  in s.        RC  S(ok)______________________________________0         -446   -276         2   21         -111   -822         81  32         -481   -809         34  13         -853   -829         24  0PP(1)     RC     S(rc)______________________________________3         24     02         34     1______________________________________ CPO: 1-2-3 
    
     The operation is as follows. 
     From the steps 1, 2 and 3, there results an order corresponding to the one from example 1: 1-2-3. A step omitted in the previous examples is step 4, in which the remaining paths are ranked as well. The path order then becomes 1-2-3-0. According to step 5, however, path 0 is ruled out again on account of a recent NOK time &lt;300 s. 
     Processing the second example in conformity with the second method takes place as follows: 
     EXAMPLE 
     
         ______________________________________     OK     NOKPN        in s.  in s.        RC  S(ok)______________________________________0         -600   -667         57  0*1        -322   -227         37  32         -591   -202         1   13         -445   -922         42  2______________________________________PP(1)     RC     S(rc)______________________________________3         24     02         34     1______________________________________ CPO: 3- 
    
     From the steps 1, 2 and 3 there follows an order 1-2-3. By means of step 4 path 0 is added. The path order then becomes 1-2-3-0. According to step 5, however, the paths 1 and 2 are ruled out again, on account of a recent NOK time &lt;300 s., so that the order becomes 3-0. 
     Below, there finally follows yet another example, in which a system having transmission paths 0 . . . 25 calculates the path order according to the second method. 
     EXAMPLE 
     
         ______________________________________   OK         NOKPN      in s.      in s.  RC      S(ok)                                  S(rc)______________________________________ 0      -232       -167   52      16   12 1      -18        -937   4       24   0 2      -447       -52    57      9    14 3      -20        -205   11      23   2 4      -71        -154   76      21   20 5      -49        -365   95      22   24 6      -97        -801   16      20   5 7      -180       -6     65      18   15 8      -326       -906   53      14   13 9      -738       -963   80      6    2210      -817       -605   42      4    911      -378       -81    70      13   1712      -590       -147   13      7    313      -414       -238   96      10   2514      -582       -38    28      8    715      -392       -602   29      12   816      -846       -428   7       3    117      -924       -152   23      1    6*18     -8         -753   44      25   1019      -762       -443   14      5    0420      -968       -628   76      0    2121      -129       -619   70      19   1822      -852       -982   70      2    1923      -296       -683   68      15   1624      -219       -454   46      17   1125      -408       -8     89      11   23______________________________________PP(18)  RC         S(rc)______________________________________11      70         125      89         214      28         013      96         3______________________________________ CPO&#39;: 18 13 25 11 14 5 9 20 4 22 21 23 7 2 8 0 24 10 15 14 17 6 19 12 3 1 1 CPO&#34;: 18 x x x x 5 9 20 x 22 21 23 x x 8 0 24 10 15 14 x 6 19 x x 16 1 CPO: 18 5 9 20 22 21 23 8 0 24 10 15 14 6 19 16 1 
    
     First, the calculated order (CPO&#39;) is shown without taking the NOK times into account; subsequently (CPO&#34;), the paths whose NOK times are &lt;300 s. are ruled out from selection (&#34;x&#34;); and finally the resulting order is presented (CPO). 
     The various examples for this application were generated with the help of a GWBASIC program whose source code is shown in Table 
     
                                           TABLE__________________________________________________________________________100 REM SAVE&#34;PN.BS&#34;, A110 CLS : KEY OFF120 OK = 1: NOK = 0: MAX.PATH = 50130 DIM TIME(1, MAX.PATH), SCORE(1, MAX.PATH), CORRECTED.SCORE(2,MAX.PATH), PREFERRED.PATH(MAX.PATH, MAX.PATH),RECEIVED.CODES(MAX.PATH), RANKED.SCORE(1, MAX.PATH),PREFERRED.PATH$(MAX.PATH, MAX.PATH), MARK$(MAX.PATH),PREF.SCORE(MAX.PATH), PREF.PATH$(MAX.PATH), NOPRINT(MAX.PATH)140 `---INPUT NUMBER OF PATHS---------------------------150 OPEN &#34;PN.OP&#34;FOR OUTPUT AS #1: LOCATE 1, 1: PRINT #1, STRING$(70, &#34;&#34;):LAST.PATH(0) =LAST.PATH: LOCATE 1, 1: INPUT &#34;Paths 0 . . . &#34;, LAST.PATH$: LAST.PATH =VAL(LAST.PATH$)160 IF LAST.PATH$ = &#34;&#34;THEN LAST.PATH = LAST.PATH(0)170 PREF.PATH = INT(LAST.PATH / 2): IF PREF.PATH &gt; 3 THEN PREF.PATH = 3180 IF LAST.PATH$ = &#34;0&#34;THEN CLOSE: CLS : END190 `---RESET VARIABLES------------------------------200RANKED.SCORE =0;CORRECTED.SCORES = 0: RANKED.SCORE.MAX = 0210 FOR PATH = 0 TO LAST.PATH220 RANKED.SCORE(OK, PATH) = 0230 PREF.SCORE(PATH) = 0240 NEXT PATH250 `---GENERATE INPUT DATA--------------------------------260 RANDOMIZE TIMER270 FOR PATH = 0 TO LAST.PATH280 TIME(OK, PATH) = -INT(RND * 1000) + 1290 TIME(NOK, PATH) = -INT(RND * 1000) + 1300 NEXT PATH310 IF LAST.PATH$ = &#34;&#34;GOTO 460320 FOR PATH = 0 TO LAST.PATH330 RECEIVED.CODES(PATH) = INT(RND * 100) + 1340 NEXT PATH350 IF LAST.PATH$ = &#34;&#34;GOTO 460360 FOR PATH = 0 TO LAST.PATH370 FOR X = 0 TO PREF.PATH380 PREFERRED.PATH(PATH, X) = INT(RND * (LAST.PATH + 1))390 FOR Y = 0 TO PREF.PATH400 IF (X &lt;&gt; Y) AND (PREFERRED.PATH(PATH, X) = PREFERRED.PATH(PATH, Y))GOTO 380410 IF PREFERRED.PATH(PATH, X) = PATH GOTO 380420 NEXT Y430 PREFERRED.PATH$(PATH, X) = MID$(STR$(PREFERRED.PATH(PATH, X)), 2):IF(LAST.PATH &gt;= 10) AND (PREFERRED.PATH(PATH, X) &lt; 10) THENPREFERRED.PATH$(PATH, X) = &#34;&#34;+ PREFERRED.PATH$(PATH, X)440 NEXT X450 NEXT PATH460 `---CALCULATE OK-SCORE USING POSITIVE RESPONSE DATA----------470 FORPATH = 0 TO LAST.PATH480 SCORE(OK, PATH) = 0490 FOR X = 0 TO LAST.PATH500 IF TIME(OK, PATH) &gt; TIME(OK, (PATH + X) MOD (LAST.PATH + 1)) THENSCORE(OK, PATH) = SCORE(OK, PATH) + 1510 NEXT X520 NEXT PATH530 `GOTO 640540 `---CALCULATE NOK-SCORE USING NEGATIVE RESPONSE DATA----------550 FOR PATH = 0 TO LAST.PATH560 SCORE(NOK, PATH) = 0570 FOR X = 0 TO LAST.PATH580 IF TIME(NOK, PATH) &lt; TIME(NOK, (PATH + X) MOD (LAST.PATH + 1)) THENSCORE(NOK, PATH) = SCORE(NOK, PATH) + 1590 NEXT X600 NEXT PATH610 `---CORRECT OK-SCORE USING NEGATIVE RESPONSE DATA-----------620 FORPATH = 0 TO LAST.PATH630 `IF TIME(OK, PATH) &lt; TIME(NOK, PATH) THEN CORRECTED.SCORE(OK, PATH)0: ELSE CORRECTED.SCORE(OK, PATH) = SCORE(OK, PATH)640 NEXT PATH650 `---RE-RANK CORRECTED SCORE AND CALCULATE HIGHEST SCORE-------660 FOR PATH = 0 TO LAST.PATH670 `MARK$(PATH) = &#34;&#34;680 FOR X = 0 TO LAST.PATH690 CORRECTED.SCORE(OK, PATH) = SCORE(OK, PATH)700 IF CORRECTED.SCORE(OK, PATH) &gt; CORRECTED.SCORE(OK, (PATH + X) MOD(LAST.PATH + 1)) THEN RANKED.SCORE(OK, PATH) = RANKED.SCORE(OK, PATH) +710 IF CORRECTED.SCORE(OK, PATH) = 0 THEN RANKED.SCORE(OK, PATH) =RANKED.SCORE: RANKED.SCORE = RANKED.SCORE + 1: GOTO 730720 NEXT X730 CORRECTED.SCORES = CORRECTED.SCORES + CORRECTED.SCORE(OK, PATH)740 IF RANKED.SCORE(OK, PATH) &gt; RANKED.SCORE.MAX THEN RANKED.SCORE.MAX= RANKED.SCORE(OK, PATH)750 NEXT PATH760 FOR PATH = 0 TO LAST.PATH770 IF CORRECTED.SCORES = 0 THEN CORRECTED.SCORE(OK, PATH) = SCORE(NOK,PATH): RANKED.SCORE(OK, PATH) = SCORE(NOK, PATH)780 `IF RANKED.SCORE(OK, PATH) = LAST.PATH THEN SELECTED.PATH = PATH790 IF RANKED.SCORE(OK, PATH) = RANKED.SCORE.MAX THEN SELECTED.PATH =PATH800 NEXT PATH810 `---RANK FOR NUMBER OF RECEIVED RESPONSES OF PREFERRED PATH OFSELECTED PATH820 FOR PATH = 0 TO PREF.PATH830 PREF.SCORE(PATH) = 0840 FOR X = 0 TO PREF.PATH850 IF RECEIVED.CODES(PREFERRED.PATH(SELECTED.PATH, PATH)) &gt;RECEIVED.CODES(PREFERRED.PATH(SELECTED.PATH, X)) THEN PREF.SCORE(PATH) =PREF.SCORE(PATH) + 1860 NEXT X870 PREF.PATH$(PREF.SCORE(PATH)) = PREFERRED.PATH$(SELECTED.PATH, PATH)880 NEXT PATH890 `---DISPLAY RESULTS-------------------------------900 CLS910 PRINT #1, &#34;&#34;: PRINT #1, USING &#34; PN  OK S(ok) NOK S(nok) CS(ok)PP(##) RC &#34;; SELECTED.PATH920 FOR PATH = 0 TO LAST.PATH930 IF PREFERRED.PATH$(SELECTED.PATH, PATH) = &#34;&#34; THENPREFERRED.PATH$(SELECTED.PATH, PATH) = STRING $((LOG(LAST.PATH) / LOG(10) +.5), &#34;&#34;940 IF PREFERRED.PATH$(SELECTED.PATH, PATH) = &#34;&#34; THENPREFERRED.PATH $(SELECTED.PATH, PATH) = STRING $((LOG(LAST.PATH) /LOG(10) +950 IF PATH = SELECTED.PATH THEN MARK$(PATH) = &#34;*&#34;: ELSE MARK$(PATH) = &#34;960 PRINT #1, USING &#34;&amp;##  +###s. ## +###s. ##  ##  &amp;  ###&#34;;MARK$(PATH); PATH; TIME(OK, PATH); SCORE(OK, PATH); TIME(NOK, PATH);SCORE(NOK, PATH); CORRECTED.SCORE(OK, PATH);PREFERRED.PATH$(SELECTED.PATH, PATH); RECEIVED.CODES(PATH)970 NEXT PATH980 PRINT #1, &#34;&#34;: PRINT #1, USING &#34;PP(##) RC  S(rc)&#34;; SELECTED.PATH990 FOR PATH = 0 TO PREF.PATH1000 PRINT #1, USING &#34; &amp;  ##  ##&#34;; PREFERRED.PATH$(SELECTED.PATH,PATH); RECEIVED.CODES(PREFERRED.PATH(SELECTED.PATH, PATH));PREF.SCORE(PATH)1010 NEXT PATH1020 PRINT #1, : PRINT #1, USING &#34;CPO(1): ##&#34;; SELECTED.PATH;1030 FOR PATH = PREF.PATH TO 0 STEP -11040 PRINT #1, ; VAL(PREF.PATH$(PATH));1050 NEXT PATH1060 FOR X = LAST.PATH TO 0 STEP -11070 FORPATH = 0 TO LAST.PATH1080 IF PATH = SELECTED.PATH THEN NOPRINT(PATH) = 11090 FOR Y = PREF.PATH TO 0 STEP -11100 IF VAL(PREF.PATH$(Y)) = PATH THEN NOPRINT(PATH) = 11110 NEXT Y1120 IF (SCORE(OK, PATH) = X) AND (NOPRINT(PATH) = O) THEN PRINT #1,;PATH;1130 NEXT PATH1140 NEXT X1150 PRINT #1,1160 IF TIME(NOK, SELECTED.PATH) &gt;-300 THEN PRINT #1, &#34;CPO(2): x &#34;; :ELSEPRINT #1, &#34;CPO(2): &#34;; STR$(SELECTED.PATH); &#34;&#34;;1170 FOR PATH = PREF.PATH TO 0 STEP -11180 IF TIME(NOK, VAL(PREF.PATH$(PATH))) &gt;-300 THEN PRINT #1, &#34;x &#34;; :ELSEPRINT #1, ; PREF.PATH$(PATH); &#34;&#34;;1190 NEXT PATH1200 FOR X = LAST.PATH TO 0 STEP -11210 FOR PATH = 0 TO LAST.PATH1220 IF PATH = SELECTED.PATH THEN NOPRINT(PATH) = 11230 FOR Y = PREF.PATH TO 0 STEP -11240 IF VAL(PREF.PATH$(Y)) = PATH THEN NOPRINT(PATH) = 11250 NEXT Y1260 IF (TIME(NOK, PATH) &gt; -300) AND (SCORE(OK, PATH) = X) AND(NOPRINT(PATH) = 0) THEN PRINT #1, &#34;x&#34;; : ELSE IF (SCORE(OK, PATH) = X)AND(NOPRINT(PATH) = 0) THEN PRINT #1, ; STR$(PATH);1270 NEXT PATH1280 NEXT X1290 PRINT #1,1300 PRINT #1, &#34;CPO(3): &#34;; : IF TIME(NOK, SELECTED.PATH) &lt; -300 THENPRINT #1,STR$(SELECTED.PATH); &#34;&#34;;131 FORPATH = PREF.PATH TO 0 STEP -11320 IF TIME(NOK, VAL(PREF.PATH$(PATH))) &lt; -300 THEN PRINT #1,;PREF.PATH$(PATH); &#34;&#34;;1330 NEXT PATH1340 FOR X = LAST.PATH TO 0 STEP -11350 FOR PATH = 0 TO LAST.PATH1360 IF PATH = SELECTED.PATH THEN NOPRINT(PATH) = 11370 FOR Y = PREF.PATH TO 0 STEP -11380 IF VAL(PREF.PATH$(Y)) = PATH THEN NOPRINT(PATH) = 11390 NEXT Y1400 IF (TIME(NOK, PATH) &lt; -300) AND (SCORE(OK, PATH) = X) AND(NOPRINT(PATH) = 0) THEN PRINT #1, ; STR$(PATH);1410 NEXT PATH1420 NEXT X1430 CLOSE__________________________________________________________________________