Patent Publication Number: US-7904098-B2

Title: Method of assigning transmission channels in a telecommunications network and user station

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 10/705,523 filed on Nov. 10, 2003 now U.S. Pat. No. 7,551,932, which is a continuation of U.S. patent application Ser. No. 10/377,443 filed Feb. 28, 2003 now abandoned and U.S. patent application Ser. No. 10/148,854 filed Jun. 3, 2002 now abandoned, which is a National Phase of Application No. PCT/DE00/03912 filed on Nov. 9, 2000, which claims priority to prior German Patent Application No. 199 57 740.4 filed on Dec. 1, 1999 and German Patent Application No. 100 08 838.4 filed on Feb. 25, 2000, all of which are hereby incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method of assigning transmission channels in a telecommunications network and to a user station. 
     BACKGROUND INFORMATION 
     A method and a device for operation in an indoor CDMR telecommunications system are referred to in European Published Patent Application No. 0 865 172, in which two or more wireless communications systems are operated superimposed. One of the two systems is an indoor system and the other is an outdoor system. The indoor system monitors the operation of the outdoor system and detects which part of the available radio resources are sometimes not used or are interference-free in the outdoor system. The indoor system dynamically selects an unused outdoor channel for indoor operation. The indoor radio traffic is divided into TDD time slots, which include the time slots for monitoring the existing radio connections on other outdoor channels, so that rapid changes are possible in accordance with changing traffic and changing interference conditions. A threshold value comparison is performed during the selection of the channels. 
     In mobile radio systems of the third generation, for example in accordance with the GSM standard (Global System for Mobile Communications) or the UMTS standard (Universal Mobile Telecommunication System) or the like, two concepts (or modes) may be provided for transmitting signals via an air interface between a base station and a mobile station, depending on the transmission resource used. If various frequency bands are provided as a transmission resource, an FDD mode (Frequency Division Duplex) may be used, in which two different frequency bands are used to transmit the signals from the mobile station to the base station in the uplink transmission direction and from the base station to the mobile station in the downlink transmission direction. If time slots are used as a transmission resource, the TDD mode (Time Division Duplex) may be used, in which different time slots are used for the uplink transmission direction and the downlink transmission direction, while using the same frequency band. Further channel separation is possible for both modes in this case. 
     However, in uncoordinated operation the base stations may not be linked via a higher-order system, so that coordinated code assignment may not be possible. Such operation may be advisable, for example, for the home sector with cordless telephones, in which, under certain circumstances, many individual base stations may be operated independently from one another. In this case, the code assignment may not be coordinated. Therefore, only one base station may be active per transmission resource, for example, per time slot or per frequency band, but even using multiple different codes for this purpose. This transmission resource may be occupied for a neighboring base station, since the station may not know the codes used. A power measurement may permit the neighboring base station to detect whether a transmission resource is occupied. If so, the neighboring base station may substitute other transmission resources, for example, other time slots or frequency bands. 
     SUMMARY OF THE INVENTION 
     It is believed that an exemplary method according to the present invention for assigning transmission channels in a telecommunications network and an exemplary user station according to the present invention may have the advantage in that, in uncoordinated operation of base stations, at least one of the transmission channels is assigned for transmitting signals between one of the base stations and one of the mobile stations as a function of a channel measurement. To perform the channel measurement, the transmission power on all possible transmission channels is measured, if the previously measured transmission power on the transmission channel is minimal. In this manner, the existing transmission channels may be optimally distributed on connections set up or to be set up for transmitting signals between the base stations and the mobile stations, so that the capacity of the telecommunications network, and therefore the number of connections to be set up simultaneously, may be increased, or at least maximized. The same transmission channel may even be used simultaneously by various base stations if, for example, due to a limited range, the various base stations influence one another insignificantly or not at all. 
     It may be advantageous that codes are provided, through which at least one transmission resource, for example, a time slot or a frequency band, is spread using multiple transmission channels for transmitting signals between the base stations and the mobile station, and that the channel measurement includes a code measurement, in which a received signal for each transmission resource is despread using each allowed code to measure the transmission power of each of the transmission channels. In this manner, a transmission resource, for example, a time slot or a frequency band, may be used jointly and simultaneously by different base stations and/or by multiple transmission channels. Through the division of the transmission resources, the capacity of the telecommunications network, and therefore the number of connections capable of being set up simultaneously, may be increased. 
     It is believed to be advantageous in that the channel measurement for the assignment of at least one of the transmission channels between one of the base stations and one of the mobile stations is performed while a connection is being established. In this manner, the capacity of the telecommunications network is used at the earliest possible time for every connection to be set up. 
     It is also believed to be advantageous that the channel measurement for the assignment of at least one of the transmission channels is performed during an existing connection between one of the base stations and one of the mobile stations, that the connection quality of the existing connection is measured in parallel, and, if the connection quality falls below a preselected value, that a channel change is performed and at least one new transmission channel is assigned as a function of the channel measurement of the existing connection. In this manner, dynamic channel assignment may be implemented for one or more existing connections, so that the transmission channels previously assigned to an existing connection have the highest possible connection quality. 
     In addition, it is believed to be advantageous that, for at least one of the base stations, specific information is transmitted via a broadcast channel to all mobile stations in the reception range of the at least one base station, and that the broadcast channel is changed if the interference detected thereon exceeds a preselected value. In this manner, the broadcast channel may be dynamically assigned to at least one of the base stations, the broadcast channel previously used receiving as little interference as possible. 
     It is believed that a further advantage is that at least one of the transmission channels is reserved for use as a broadcast channel. In this manner, the expense and time required for the mobile stations to find the broadcast channel is reduced, since the stations may find the broadcast channel from an already selected or preselected set of transmission channels. 
     It is also believed to be advantageous in that, if the transmission capacity of the established transmission channels is insufficient, at least one transmission channel scrambled using a new scrambling code is assigned for transmitting signals between one of the base stations and one of the mobile stations as a function of a channel measurement, in which the transmission power on all possible transmission channels is measured after scrambling, using a scrambling code, if the transmission power measured on the scrambled transmission channel is minimal. In this manner, it may be avoided that a base station in uncoordinated operation cannot find a free transmission channel because, for example, one or more other base stations already occupy all of the transmission channels. Rather, the number of transmission channels and therefore the data rate may be further increased by using scrambling codes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an exemplary user station according to the present invention. 
         FIG. 2  is a code-time slot diagram. 
         FIG. 3  is a diagram showing an exemplary first arrangement of base and mobile stations in a mobile radio network according to the present invention. 
         FIG. 4  is a diagram showing an exemplary second arrangement of base and mobile stations in a mobile radio network according to the present invention. 
         FIG. 5  shows a schematic block diagram (flowchart) of an exemplary method according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 ,  15  identifies a user station of a telecommunications network  5 . Telecommunications network  5  may be implemented, for example, as a landline network or as a mobile radio network. If telecommunications network  5  is a mobile radio network, user station  15  may include a base station  11 ,  12  or a mobile station  21 ,  22 , as shown, for example, in  FIG. 3 . For the description to follow, it is presumed, for exemplary purposes only, that telecommunications network  5  is a mobile radio network and that user station  15  is a base station  11 ,  12  or a mobile station  21 ,  22 . Mobile radio system  5  and user station  15  may be implemented, for example, according to the GSM standard (Global System for Mobile Communication), the UMTS standard (Universal Mobile Telecommunication System) or the like. 
     User station  15  illustrated in  FIG. 1  includes a receiver  25 , to which a receiving aerial  60  is connected. As shown in  FIG. 1 , user station  15  also includes a transmitter  35 , to which a transmitting aerial  70  is connected. Receiving aerial  60  and transmitting aerial  70  may also be combined into a combined transmitting/receiving aerial by using a multiplexer, for example. Receiver  25  is connected on the output side to an input of code measurement arrangement  30  for code measurement and is also connected to an input of a despreading device  45 . Codes of a first code memory  51  are also supplied to code measurement arrangement  30  for code measurement. In addition, at least one code of a second code memory  52  is supplied to despreading device  45 . Code measurement arrangement  30  for code measurement is connected on the output side to an input of channel measurement arrangement  10  for channel measurement. Despreading device  45  is connected on the output side to an input of a connection quality arrangement  40  for measuring the connection quality. An output of connection quality arrangement  40  is also supplied to channel measurement arrangement  10 . Channel measurement arrangement  10  is connected on the output side to an input of a channel assignment arrangement  20  for channel assignment, the output of which is supplied to transmitter  35 . 
     In the following description, for exemplary purposes only, both first base station  11  and second base station  12  in mobile radio network  5  as shown in  FIG. 3  are constructed similarly to the user station  15  shown in  FIG. 1 , and both first mobile station  21  and second mobile station  22  are constructed similarly to user station  15  shown in  FIG. 1 . As shown in  FIG. 3 , first base station  11  covers a first radio cell  61 , in which the first base station  11  may communicate with mobile stations using radio signals. Second base station  12  covers a second radio cell  62 , in which the second base station  11  may communicate with mobile stations using its radio signals. First mobile station  21  is positioned in first radio cell  61 , while second mobile station  22  is positioned in second radio cell  62 . A first connection  41  is to be established between first base station  11  and first mobile station  21 , while a second connection  42  is to be established between second base station  12  and second mobile station  22 . 
     Two different concepts (or modes) may be provided for first connection  41  and for second connection  42 : FDD mode (Frequency Division Duplex), in which two different frequency bands are used as a transmission resource for the uplink transmission direction from respective mobile stations  21 ,  22  to assigned base stations  11 ,  12 ; and TDD mode (Time Division Duplex), in which different time slots in the same frequency band are used as a transmission resource for the uplink transmission direction and the downlink transmission direction. In both modes, the respective transmission resources may be spread into multiple transmission channels by using codes C based, for example, on a CDMA method (Code Division Multiple Access) for further channel separation. In this case, one frequency band or one time slot may each be spread into multiple transmission channels by using different codes. One such transmission resource, for example, one time slot or one frequency band, may be used simultaneously by various connections and/or by the same connection in the uplink or in the downlink transmission direction by using different codes, so that the capacity of mobile radio network  5  and/or the number of connections which may be set up in mobile radio network  5  may be increased by increasing the number of usable transmission channels. If, for example, the transmission resources are implemented as time slot ZS, spreading into multiple transmission channels by using different codes C is illustrated in  FIG. 2 . In this case, fifteen time slots are provided per transmission frame on the abscissa numbered from 0 to 14 in  FIG. 2 . Four different codes C from 1 to 4 are plotted on the ordinate, so that each time slot ZS is spread into four different transmission channels, which differ from one another due to different coding, using the same spread factor  4 . The transmission channels created in this manner are illustrated as raster elements in the code-time slot diagram shown in  FIG. 2  and are indicated, as a whole, using reference number  1 . 
     For example, time slots for transmitting signals in mobile radio network  5  may be used as a transmission resource. In this case, base stations  11 ,  12  are operated uncoordinatedly and are not connected via a higher order system, so that coordinated code assignment may not be possible. Such uncoordinated operation may be used for the home sector when using mobile stations  21 ,  22  implemented as cordless telephones, since many individual base stations may be, under certain circumstances, operated independently from one another and therefore uncoordinatedly. For a cordless telephony application, telecommunications network  5 , base stations  11 ,  12 , and mobile stations  21 ,  22  may be implemented, for example, in accordance with the DECT standard (Digital European Cordless Telecommunications). In such uncoordinated operation, coordinated code assignment for the individual connections to be set up between base stations  11 ,  12  and mobile stations  21 ,  22  may no longer be possible. 
     Below, first connection  41  to be set up between first base station  11  and first mobile station  21  is described for exemplary purposes only. While the connection is being established, code measurement arrangement  30  checks, either in first base station  11  or in first mobile station  21 , which codes C in which time slots ZS are already occupied by other connections. For this purpose, the signal for each of fifteen time slots ZS received in first base station  11  and/or first mobile station  21  should be despread using each permitted code C stored in first code memory  51 , corresponding to CDMA demodulation. Through despreading in code measurement arrangement  30 , all transmission channels  1 , each of which are implemented as a code/time slot combination, are extracted from the received signal. As shown in  FIG. 2 , sixty transmission channels result from the multiplication of fifteen time slots ZS by four codes C. Extracted transmission channels  1  are then supplied to channel measurement arrangement  10 , which measures the transmission power on all extracted transmission channels  1 . First connection  41  to be set up is then assigned to at least one of transmission channels  1  by channel assignment arrangement  20 . In this case, the transmission channel with a minimal previously measured transmission power is assigned to first connection  41 . For a full duplex connection to be set up between first base station  11  and first mobile station  21 , the exemplary method according to the present invention is to be performed both for the uplink transmission direction from first mobile station  21  to first base station  11  and for the downlink transmission direction from first base station  11  to first mobile station  21 , so that at least one transmission channel may be used for first connection  41  in each of the two transmission directions.  FIG. 3  illustrates the downlink transmission direction with arrows for both first connection  41  and for second connection  42 . In this case, the channel measurement for assigning at least one of transmission channels  1  may be performed in the uplink transmission direction by first base station  11  and the channel measurement for assigning at least one of transmission channels  1  may be performed in the downlink transmission direction by first mobile station  21 . The assignment of the at least one of transmission channels  1  selected through the channel measurement in the uplink transmission direction may then be performed by first base station  11 . The assignment is performed by its channel assignment arrangement  20 , which, via transmitter  35  of first base station  11 , transmits a corresponding signal to first mobile station  21  in regard to the at least one assigned transmission channel. In a corresponding manner, the assignment of at least one of transmission channels  1  in the downlink transmission direction may be performed by first mobile station  21 , the channel assignment arrangement  20  of which transmits a signal to first base station  11  via corresponding transmitter  35  so that first base station  11  may know the at least one transmission channel selected for the downlink transmission direction. 
     According to this exemplary embodiment of the present invention, a first transmission channel  31 , which represents a combination of the third time slot and the second code shown in the code/time slot diagram of  FIG. 2 , is assigned for the downlink transmission direction of first connection  41 . 
     Before establishing first connection  41 , first base station  11  initially selects one of transmission channels  1  and uses it as a broadcast channel. According to this exemplary embodiment of the present invention, base station  1  first selects a combination of first time slot and third code, as shown in the code/time slot diagram of  FIG. 2 , as broadcast channel  50 . The specific information for first base station  11  is transmitted via broadcast channel  50  to all mobile stations located in first radio cell  61 . This specific information may contain, for example, the codes used by first base station  11 , an identification of first base station  11 , synchronization information, information about transmission channels and/or code/time slot combinations already used, information about paging messages that exist for one or more of the mobile stations located in first radio cell  61 , etc. First mobile station  21  located in first radio cell  61  may therefore recognize first base station  11  assigned to it by synchronization on broadcast channel  50  and analysis of the information transmitted via this broadcast channel  50 . 
     Each of transmission channels  1  may be used as broadcast channel  50 . To avoid interference of the broadcast channels of different base stations  11 ,  12 , the broadcast channel may be changed if needed, for example, if interference from other broadcast channels or transmission channels detected on the broadcast channel exceeds a preselected value. To reduce the outlay of first mobile station  21  and to find broadcast channel  50 , either a special code C may be reserved and/or preselected for any desired time slot ZS or a specific time slot ZS may be reserved and/or preselected for any desired code C for the broadcast channel of first base station  11 , or a prereserved selection of any desired specified transmission channels and/or code/time slot combinations may be used as a broadcast channel  50 . 
     During existing first connection  41 , the transmission power is cyclically remeasured on all possible transmission channels  1 , so that a picture of free and occupied and/or of malfunctioning and functioning transmission channels is continuously available. In parallel, the connection quality of existing first connection  41  is measured by connection quality arrangement  40  in first base station  11  and/or in first mobile station  21 , for example, on the basis of the transmission error rate. If the connection quality falls below a preselected value, a channel change to another transmission channel and/or another code/time slot combination may be performed. For this purpose, the transmission powers of the transmission channels and/or code/time slot combinations previously not used for first connection  41  should be continuously monitored. For the channel change, first base station  11  measures the connection quality of first connection  41  in the uplink transmission direction and first mobile station  21  measures the corresponding connection quality of first connection  41  in the downlink transmission direction. If the connection quality falls below a preselected threshold, the channel changes in the uplink and downlink transmission directions occur independently from one another. For this purpose, the establishment of the connection may be accomplished in three manners. In the first manner, the channel change is performed solely by base station  11 , since it already knows all of the transmission channels it uses. For this purpose, first mobile station  21  transmits, via its transmitter  35 , the measurement results of the connection quality or the request for a channel change due to such measurement results for the downlink transmission direction to first base station  11 . In the second manner, mobile station  21  first initiates the channel change in the downlink transmission direction and first base station  11  initiates the channel change in the uplink transmission direction. The third manner is oriented to the DECT standard, in which the channel change is initiated by first mobile station  21  both in the uplink and in the downlink transmission directions, and first base station  11  merely signals to first mobile station  21  that a channel change is necessary in the uplink transmission direction. Regardless of whether the connection quality is measured in first base station  11  or in first mobile station  21 , this measurement is performed in that the transmission channels to be evaluated for first connection  41  are extracted from the signal received via corresponding receiver  25  by respective despreading device  45  with the aid of the code(s) assigned to first connection  41 , which is/are stored in second code memory  52 , and supplied to connection quality arrangement  40 . In connection quality arrangement  40 , the connection quality of the transmission channels for first connection  41  may then be, for example, measured on the basis of the transmission error rate. In parallel, code measurement arrangement  30  extracts all transmission channels  1  from the signal received via receiver  25  with the aid of the codes stored in first code memory  51  and supplies these transmission channels to the channel measurement in first channel measurement arrangement  10 , which measures the transmission power on extracted transmission channels  1 . Channel measurement arrangement  10  checks, with reference to the value of the connection quality of the respective transmission channel of first connection  41  determined by connection quality arrangement  40 , whether this value falls below a preselected value for the connection quality. If so, channel measurement arrangement  10  selects the transmission channel that has the minimum transmission power and causes channel assignment arrangement  20  to subsequently use this transmission channel for first connection  41  instead of the corresponding transmission channel measured by connection quality arrangement  40 , which has too low a connection quality. 
       FIG. 3  illustrates first base station  11  and second base station  12  operated independently from one another. One mobile station  21 ,  22  is registered in each of two base stations  11 ,  12 . First mobile station  21  is initially located at a first position A within first radio cell  61 , illustrated in  FIG. 3 , and has a first transmission/reception range  71 . Second mobile station  22  is located at a third position C in second radio cell  62  and includes a second transmission/reception range  72 . First mobile station  21  may transmit and receive radio signals within first transmission/reception range  71 . Signals transmitted outside the first transmission/reception range  71  may no longer be received by first mobile station  21 . In addition, signals transmitted by first mobile station  21  outside first transmission/reception range  71  may no longer be received in second base station  12  and in second mobile station  22 . The same is true for second transmission/reception range  72  of second mobile station  22 . In this case, the same transmission channels and/or code/time slot combinations are simultaneously used in the uplink and in the downlink transmission directions for both first connection  41  and second connection  42 . As shown in  FIGS. 2 and 3 , first transmission channel  31  is used for the downlink transmission direction for both first connection  41  and second connection  42 . If a channel change occurs, it applies for both the uplink and the downlink transmission directions, both being independent from one another. Both mobile stations  21 ,  22  are sufficiently distant from one another so that their transmission/reception ranges  71 ,  72  do not overlap and do not mutually interfere in their transmission channels. The instantaneous transmission quality is measured for both connections  41 ,  42  in the manner described above, both in the uplink and in the downlink transmission directions, for example, by analyzing the transmission or bit error rates. Both mobile stations  21 ,  22  cyclically establish the transmission power of all possible transmission channels  1  and/or code/time slot combinations, by despreading all transmission channels  1  and/or code/time slot combinations in the way described above via code measurement arrangement  30  and establishing the transmission power on transmission channels  1  extracted in this way via channel measurement arrangement  10  and storing this transmission power in tabular form in a memory (not shown in  FIG. 1 ). Smaller values of the transmission power measured signal little or no interference in this case. If first mobile station  21  now moves from first position A into second position B and therefore, as shown in  FIG. 3 , into second radio cell  62  and/or into second transmission/reception range  72  of second mobile station  22 , the mutual interference of the transmission channels used increases and the connection quality is therefore reduced. If it falls below the preselected value for the connection quality, then a channel change is initiated in the way described above for at least one of the two connections  41 ,  42  and this connection is assigned at least one new transmission channel in the uplink and/or in the downlink transmission direction. 
     In a modification of the exemplary embodiment described with reference to  FIG. 2 , despreading individual time slots ZS by more or less than four codes C may also be provided. 
     According to this exemplary embodiment of the present invention, however, all fifteen time slots ZS per transmission frame are spread using four codes C, so that a total of 60 transmission channels results. Both first base station  11  and second base station  12  may thus access 60 such transmission channels if there is no interference, so that a total of 60 connections may theoretically be established simultaneously within the geographical range defined by first radio cell  61  and by second radio cell  62 , if the reservation of transmission channels for setting up a broadcast channel for each of the two base stations  11 ,  12  is not considered. 
     Another exemplary embodiment according to the present invention is described with reference to  FIG. 4 . In this case,  310  identifies a radio coverage area, for example, a shared radio cell, in which a third base station  110  and a fourth base station  210  are operated independently and uncoordinatedly from one another. In this exemplary embodiment, TDD operation using a CDMA method is described for exemplary purposes. Telecommunications network  5  may be implemented as a mobile radio network or as a cordless telephone network. 
     Third base station  110  and fourth base station  210  are locally positioned directly adjacent to one another and only separated from one another by a wall  320 , which does not, however, represent an obstruction for the radio frequencies used for transmission, but rather indicates that both base stations  110 ,  210  are, for example, positioned in neighboring office rooms. Third base station  110  supplies a third mobile station  120  via a third connection  140  and a fourth mobile station  130  via a fourth connection  150 . Third connection  140  and fourth connection  150  may represent radio connections in the TDD mode. In an exemplary scenario, third connection  140  and fourth connection  150  together may require a data rate so high that all of the transmission channels of the TDD mode available are used. Fourth base station  210  then wishes to establish a fifth connection  240  to a fifth mobile station  220  in the TDD mode using the CDMA method. For this purpose, as in the exemplary embodiment described with reference to  FIG. 3 , all transmission channels available in radio coverage area  310 , i.e., code/time slot combinations, are checked as to whether they are already occupied or have interference, which causes them to fall below the preselected value for connection quality. If so, the corresponding transmission channel is unusable. If not, it is usable. Fourth base station  210  recognizes whether all transmission channels in radio coverage area  310  are unusable and/or whether the number of the usable transmission channels still available for fifth connection  240  is smaller than the number of transmission channels necessary for fifth connection  240 . 
     To permit fifth connection  240  to be established without producing unacceptable interference for already existing third connection  140  and already existing fourth connection  150 , fourth base station  210  changes a scrambling code used jointly with third base station  110 . 
     One single scrambling code is used within a radio cell. All signals transmitted in the radio cell are scrambled using this scrambling code. To prevent signals of different neighboring radio cells from mutually interfering with one another, for example, if CDMA is used, the signals are scrambled using different scrambling codes, i.e., neighboring radio cells use different scrambling codes. The various scrambling codes are selected so that they have the smallest possible cross correlation with one another for any desired mutual time shifts. The spreading of the signals within a radio cell is then performed using orthogonal codes, which are mutually uncorrelated due to the synchronous transmission. 
     In another scenario, this concept is abandoned in the case of insufficient transmission capacity, in that in radio coverage area  310 , which is to represent a shared radio cell, a scrambling code is introduced for fourth base station  210  which is different from the scrambling code of third base station  110 . 
     Subsequently, the search for and possible assignment of sufficient interference-free transmission channels for fifth connection  240  to be established are repeated in the way described above with reference to  FIGS. 1 to 3 , but using the new scrambling code. 
     This procedure is repeated until a sufficient number of sufficiently interference-free transmission channels have been found and assigned to fifth connection  240 . 
     If enough sufficiently interference-free transmission channels are not found, a further scrambling code may be checked in the way described above and used if necessary. This procedure may be repeated until an “unused” scrambling code having enough sufficiently interference-free transmission channels is found. 
     On the basis of the scenario described above, a sixth connection  250  may be established in the TDD mode using the CDMA method from fourth base station  210  to a sixth mobile station  230 , as described with reference to  FIG. 4 . In another exemplary scenario, fifth connection  240  requires a data rate so high that insufficient transmission channels are available for sixth connection  250 , even with scrambling using the new scrambling code because, for example, all transmission channels having the new scrambling code are used by fifth connection  240 . The new scrambling code is referred to below as the first new scrambling code. 
     For sixth connection  250 , fourth base station  210  may now introduce a second new scrambling code, which differs from the first new scrambling code and the original scrambling code used, for example, by fourth base station  210 , all scrambling codes used having the characteristic of low mutual cross correlation for any desired mutual time shift. 
     The search for and possible assignment of sufficient interference-free transmission channels for sixth connection  240  to be established are then performed again in the way described above with respect to  FIGS. 1 to 3 , but using the second new scrambling code. 
     This procedure is also repeated until a sufficient number of sufficiently interference-free transmission channels is found and assigned to sixth connection  240 . 
     If enough sufficiently interference-free transmission channels are not found, a further scrambling code may be checked and used in the way described above. This procedure may be repeated until an “unused” scrambling code having enough sufficiently interference-free transmission channels is found. 
     For a connection to be established between one of base stations  110 ,  210  and one of mobile stations  120 ,  130 ,  220 ,  230 , various scrambling codes may be used if the data rate necessary for this connection and the available sufficiently interference-free transmission channels require it. 
     Therefore, if the connection quality of all or many transmission channels is, for example, worsening due to interference from the uncoordinated operation described above, the influence of interference may be reduced by substituting other scrambling codes. 
     In this case, the use of different scrambling codes may lead to the transmission capacity of locally delimited telecommunications network  5  in uncoordinated operation being many times greater than that in coordinated operation. 
     The search for previously unused scrambling codes may either be performed according to a fixed sequence or by random selection of a scrambling code. 
     Third base station  110 , fourth base station  210 , third mobile station  120 , fourth mobile station  130 , fifth mobile station  220 , and sixth mobile station  230  are each to have the construction and the mode of operation described for user station  15  shown in  FIG. 1 . Simultaneously, channel measurement arrangement  10  may produce the new scrambling code(s) and perform appropriate scrambling of the transmission channels to be measured. 
     The measurement and assignment of transmission channels scrambled, and therefore also the change of the scrambling code, may be performed both in base stations  11 ,  12 ,  110 ,  210 , for example, for the uplink transmission direction, and in mobile stations  21 ,  22 ,  120 ,  130 ,  220 ,  230 , for example, for the downlink transmission direction. 
     The search for new scrambling codes may be performed permanently or as needed.