Abstract:
The invention relates to a method of setting a plurality of wireless telecommunication parameters in a wireless telecommunication network ( 400 ). wherein the method comprises the following steps: setting ( 106 ) a first parameter of the plurality of wireless telecommunication parameters in a first cell by a network entity ( 104 ); running ( 110; 206 ) an algorithm for optimizing at least one second parameter of the plurality of wireless telecommunication parameters in the first and/or at least one second cell dependent on the first parameter.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to the field of wireless telecommunication, more specifically to self-organizing networks in wireless telecommunication. 
       BACKGROUND AND RELATED ART 
       [0002]    In self-organizing networks parameters of the wireless telecommunication may be adapted by base stations, cells and/or central entities of the wireless telecommunication network. No human interaction is necessary for the wireless telecommunication in the wireless telecommunication network. 
         [0003]    EP 2 166 796 A1 discloses a method for adjusting a parameter value for controlling a handover of a user equipment between a first and a second base station of a telecommunication network. The method comprises providing policy information about a desired nominal operational condition of the network by an operator to the first and the second base station, determining a first and second optimized parameter value for carrying out the handover based on the provided policy information, transmitting an information message between the first and the second base station, wherein the information message is indicative for an intended change of the first and/or the second optimized parameter value, and adjusting the first optimized parameter value by means of the first base station and/or the second optimized parameter value by means of the second base station in a coordinated manner based on the transmitted information message. It is further described a base station and a computer program for carrying out and controlling, respectively, the described method. 
         [0004]    US 2004/0266442 A1 discloses a method for determining relevant key performance indicators for a specific entity within the network as well as first parameters, which influence the key performance indicators. A number of entities similar to said specific entity is selected, wherein relevant key performance indicators are associated to every entity. The key performance indicators as well as the selected number of entities are used as elements in a first cost function, i.e. said first cost function is calculated on the basis of the KPI and the number of entities. Said first cost function is calculated in order to evaluate the network performance. Accordingly, since said first parameters directly relate to the key performance indicators, the network performance will depend on the values of said first parameters. Thereafter the values of said first parameters are adjusted, so that a second set of values of said first parameters are obtained. The key performance indicators are determined again but this time on the basis of the second values of said first parameters and said first cost function is recalculated on the basis of these key performance indicators. The result of said first cost function calculated on the basis of said first values of said first parameters is compared to the result of said first cost function recalculated on the basis of said second values of said first parameters. This comparison is carried out to determine whether the network performance has improved. When the network performance has improved due to the adjusting of said first parameters, said second values of said first parameters are adopted as permanent parameters. 
       SUMMARY OF THE INVENTION 
       [0005]    It is the object of the present invention to provide an improved method of setting a plurality of wireless telecommunication parameters in a wireless telecommunication network, an improved base station apparatus, an improved computer readable storage medium, and an improved wireless telecommunication system. This object is achieved by the method, the base station apparatus, the computer readable storage medium, and the wireless telecommunication system according to the independent claims. Embodiments of the invention are given in the dependent claims. 
         [0006]    The invention provides a method of setting a plurality of wireless telecommunication parameters in a wireless telecommunication network. The method comprises a first step of setting a first parameter of the plurality of wireless telecommunication parameters in a first cell by a network entity. The network entity may for example be an operation and maintenance centre of the wireless telecommunication network or a base station or any other entity of the wireless telecommunication infrastructure. The first parameter may be set manually or automatically. This setting step may for example be performed by a network operator. The network operator may want to set the first parameter independently of a self-organizing structure of the wireless telecommunication network, because the corresponding parameter found by the self-organizing network may not be the optimal parameter and/or the network operator may want to test if another parameter would improve wireless telecommunication in the wireless telecommunication network. 
         [0007]    Then, an algorithm is run for optimizing at least one second parameter of the plurality of wireless telecommunication parameters in the first and/or at least one second cell dependent on the first parameter. In other words, the first parameter is used as the basis for a self-organizing algorithm of the network for optimizing at least one second parameter. It is to be noted that the at least one second parameter may be a parameter in the same cell as the first parameter or a parameter in a cell different from the first cell. 
         [0008]    This method allows network operators to manually change a parameter in the wireless telecommunication network. This may be advantageous when network errors should occur and the self-organizing network should not able to solve the problems related to these errors. A human being may be able to solve such problems by setting a parameter to a certain value not found by the self-organizing network. After the first parameter has been set the network optimizes other parameters again by performing a self-organizing algorithm. Thus, the network operator may intervene in case that he wants to configure particular parameters and/or in the case of network problems and afterwards the network organizes itself again. 
         [0009]    According to embodiments of the invention the first parameter is a fixed parameter. This means, that the first parameter cannot be changed by an algorithm of the self-organizing network after having been set by the network entity. In other words, the first parameter is not changeable by the algorithm for optimizing the at least one second parameter. 
         [0010]    According to embodiments of the invention the first parameter is only fixed for a first time period. This means that the first parameter is not fixed after the first time period anymore and may be changed by an algorithm for optimizing parameters in the wireless telecommunication network. This is advantageous because after some time network conditions may have changed and a change of the first parameter by an algorithm of the self-organizing network may be advantageous instead of leaving the first parameter fixed. 
         [0011]    According to embodiments of the invention the network entity may be caused to set the first parameter by a higher priorized SON algorithm. In other words, a higher priorized SON algorithm may set the first parameter, which then can not be changed by a lower priorized SON algorithm. The herein described algorithm for optimizing the at least one second parameter is for example such a lower priorized SON algorithm. According to embodiments of the invention the first parameter is set by the network entity to a fixed value with a trigger condition. When this trigger condition is fulfilled, the state of the first parameter is changed from “fixed” to “non-fixed”. A non-fixed parameter may be changed by any SON algorithm. In other words, the state of the first parameter may be changed when the network entity is informed about a fulfilled trigger condition. In other words, the first parameter is only fixed until the network entity resets the first parameter. 
         [0012]    This is advantageous because the first parameter has been set for some reason and the SON does not know about this reason. Thus, it is advantageous that only that network entity, which has set the first parameter as a fixed parameter, is able to change the parameter state. The network entity knows why the first parameter has been set and the network entity also knows when it could be advantageous to change the first parameter again. 
         [0013]    According to embodiments of the invention the setting of the first parameter overrules any other setting having been set for the first parameter previously. In other words, the first parameter may be set manually or automatically without any restriction and/or without regard to other settings having been set before manually or automatically by the self-organizing network. 
         [0014]    According to embodiments of the invention the first cell transmits a first signal to the at least one second cell. The first signal is indicative of the first parameter. Thus, the at least one second cell knows about the first parameter and may run the algorithm for optimizing at least one second parameter. Even if the algorithm is run in the at least one second cell, the algorithm is adapted to change parameters of the first cell except for the first parameter. Additionally, the first signal may be indicative of the first parameter being fixed. In this case, the at least one second cell knows that the first parameter cannot be changed by the algorithm for optimizing at least one second parameter. This is also taken into account for optimizing the at least one second parameter. Further, the first signal may also be indicative of the first time period. Thus, the second cell knows when the first parameter may be changed again by an algorithm of the self-organizing network. 
         [0015]    According to embodiments of the invention the algorithm for optimizing the at least one second parameter in the first and/or the at least one second cell is performed in the first cell. This is advantageous because no first signal has to be transmitted to the at least one second cell. The first cell knows about the first parameter and that the first parameter is fixed and takes this into account for the algorithm for optimizing the at least one second parameter. It is to be noted that the algorithm may optimize parameters in the first and/or the at least one second cell. The location where the algorithm is performed does not limit the parameters taken into account for the algorithm. A further benefit of running the algorithm directly in the first cell is that the algorithm may then optimize a local area of several surrounded cells. The surrounded cells are all cells which are potentially directly impacted by the fixed first parameter. Thus, a parameter optimization procedure in the first cell may already achieve to successfully adapt parameters of several affected surrounding cells. 
         [0016]    According to embodiments of the invention the at least one second cell transmits a second signal to the first cell. The second signal is indicative of changing the first parameter. Before the second signal is transmitted to the first cell, the second cell has determined by running the algorithm for optimizing at least one second parameter that the first parameter shall be changed. The second cell only performs this step, when it is unknown to the second cell that the first parameter is a fixed parameter. This may be the case for example because the first cell has not transmitted the first signal to the second cell or the second cell did not receive the first signal from the first cell. The first cell transmits a third signal in response to the second signal to the at least one second cell. The third signal is indicative of not changing the first parameter. The second cell stores information about the first parameter being fixed and reruns the algorithm dependent on the first parameter. In other words, the first cell tells the second cell that the first parameter is fixed and the second cell has to rerun the algorithm taking into account the first parameter as being fixed. The result of the rerun algorithm may be different for a plurality of parameters because usually parameters of neighboring base stations depend on each other. 
         [0017]    According to embodiments of the invention the first cell does not change the first parameter after having received the second signal. The second cell stores information about the first parameter being fixed and reruns the algorithm dependent on the first parameter. In this embodiment the first cell does not react to the second signal from the second cell. The second cell notices that the first cell does not change the first parameter because no message is received from the first cell that the first parameter is changed. The first and the second cell may also exchange information about their parameters regularly. When such a regular parameter update is received from the first cell by the second cell, the second cell knows that the first cell did not change the first parameter. The reactions of the second cell to the first cell not changing the first parameter is in both cases—with or without the third signal—similar. The second cell learns that the first parameter is a fixed parameter and reruns the algorithm taking into account the fact that the first parameter is fixed. 
         [0018]    In other words, the first cell does not notify the second cell of the fixed first parameter or the second cell has—for any reason—not received the information, that the first parameter in the first cell is fixed. But the fact that the first parameter is fixed will later be concluded or assumed by the second cell. After an indicated change of the first parameter by the second cell, the first cell does not indicate to the second cell that the first parameter is changed. Thus, because no such indication is received by the second cell, the second cell knows that the first cell did not change the first parameter. Then, the second cell stores information about the first parameter being fixed. Consequently, the fact that the first parameter is fixed is noticed by the second cell, although no notification is received from the first cell by the second cell. 
         [0019]    This can also be described as follows; 
         [0020]    The second cell does not know that the first cell cannot change its first parameter. Then the second cell sends a message to the first cell that the first cell shall change its first parameter. But then the first cell does not carry out that actions which were expected by the second cell, i.e. the first cell does not change the first parameter as requested. This non-expected behaviour of the first cell could for example be noticed by the second cell when the second cell does not receive from the first cell the parameter change confirmation message of if such a confirmation message is part of the implemented protocol but has been lost or in case the confirmation message is not implemented due to missing functionality implemented in the first cell; and/or the second cell obtains the information about the setting of the first parameter in the first cell within the next parameter information message. Based on such observations, the second cell then detects that the requested parameter change has not been carried out. Then the second cell assumes, that the first cell cannot change its first parameter, and considers this situation for future parameter optimization actions. There is the possibility that the second cell will re-evaluate or re-check this taken assumption after a certain amount of time. 
         [0021]    Alternatively, the first and the second cell exchange information about their parameters regularly. In this case, the second cell notices that the first cell did not change the first parameter when such a regular information is received. 
         [0022]    According to embodiments of the invention the second cell resends the second signal after a second time period. It is to be noted that the second time period is a 2 nd  time period in the sense of ordinal numbers. This is advantageous for testing if the first parameter is still fixed or if it has changed its state to a non-fixed parameter. Alternatively or additionally, the first cell informs the second cell when the first parameter has changed its state to a non-fixed parameter. 
         [0023]    According to embodiments of the invention the first parameter and/or the at least one second parameter is a range of physical resource blocks or a range of frequencies not being used for wireless telecommunication in the first cell or being used with a restricted transmission power, an antenna tilt of base stations of the first and/or the at least one second cell, or a parameter for a handover procedure of a wireless terminal between the first and the at least one second cell such as a time to trigger, a cell individual offset, or a transmission power antenna or a base station. 
         [0024]    Embodiments of the invention may be applied to any parameter in wireless telecommunication networks. 
         [0025]    According to embodiments of the invention the first parameter is used as the starting point for the algorithm. The algorithm optimizes also the first parameter. In other words, the first parameter is set by the network entity as a suggestion or a parameter range for the first parameter. The algorithm then starts optimizing the self-organizing network from this first parameter and may also determine another value differing from the first parameter set by the network entity for the first parameter. 
         [0026]    In another aspect the invention relates to a base station apparatus in a wireless telecommunication network. The base station apparatus comprises means for running an algorithm for optimizing at least one parameter of a plurality of wireless telecommunication parameters dependent on a first parameter. The first parameter has been set by a network entity. 
         [0027]    In another aspect the invention relates to a computer readable storage medium containing instructions that when executed by a base station apparatus according to embodiments of the invention cause the base station apparatus to perform a method of setting a plurality of wireless telecommunication parameters in a wireless telecommunication network. The method comprises running an algorithm for optimizing at least one parameter of a plurality of wireless telecommunication parameters dependent on a first parameter. The first parameter has been set by a network entity. 
         [0028]    In yet another aspect the invention relates to a wireless telecommunication system comprising at least two base stations according to embodiments of the invention and one network entity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    In the following preferred embodiments of the invention will be described, by way of example only, and with reference to the drawings in which: 
           [0030]      FIG. 1  is a schematic view of a wireless telecommunication network, where a first parameter is set as a fixed parameter by a network entity; 
           [0031]      FIG. 2  is a schematic view of a wireless telecommunication network, wherein a first base station tries to modify a first fixed parameter; 
           [0032]      FIG. 3  is a schematic view of a wireless telecommunication network, wherein a second base station tries to change a first fixed parameter of a first base station and the first base station does not change the parameter and does not transmit an error message to the second base station; and 
           [0033]      FIG. 4  is a block diagram of a wireless telecommunication system comprising two base stations and one network entity. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Like numbered elements in these Figs. are either identical elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later Figs. if the function is identical. 
         [0035]      FIG. 1  is a schematic view of a wireless telecommunication system with a first base station  100  serving a first cell and a second base station  102  serving a second cell. A network entity  104 , e.g. an operation and maintenance center, is also comprised by the wireless telecommunication network. The first base station  100  and the second base station  102  communicate with wireless terminals of the wireless telecommunication system and have several parameters being adjustable for this communication. Such parameters may for example by a range of physical resource blocks or a range of frequencies not being used for wireless telecommunication in the respective cell. This is advantageous because a neighboring cell may use these resource blocks or ranges of frequencies for wireless telecommunication in its border region. Other parameters being adjustable may for example be the antenna tilt of the base station, a parameter for a handover procedure of a wireless terminal such as a time to trigger, or a cell individual offset, or a transmission power of the antenna of the base station. 
         [0036]    in general the wireless telecommunication system is a self-organizing network (SON), which means that parameters of the first base station  100  and the second base station  102  are adjusted by the network itself with the following exception. The network entity  104  sets a first parameter of the first base station  100  by transmitting a first message  106  from the network entity  104  to the first base station  100 . This is contrary to common SON procedures. The first base station  100  then changes in step  108  the corresponding parameter to the value indicated in the first message  106 . For example, the first message  106  is indicative of not using a first range of frequencies for wireless telecommunication in the first cell and the first base station has stored that a second range of frequencies is not used for wireless telecommunication in the first cell. Then, the first base station changes this parameter from not using the second range of frequencies for wireless telecommunication in the first cell to not using the first range of frequencies not used for wireless telecommunication in the first cell. 
         [0037]    Then, in step  110  the first base station runs a local area optimization algorithm. This algorithm optimizes the parameters of the first base station and of at least one further base station, e.g. the second base station  102 . If the algorithm determines that the optimum parameters are already used by the first and the second base station, no further optimization is performed. The algorithm is run, just that the first parameter is fixed and is not changed by the algorithm. The algorithm also considering the fixed parameter and optimizes other parameters around this fixed one. The algorithm has the possibility to modify all parameters except the fixed one. The local area optimization algorithm  110  takes this into account for optimizing the other parameters. For example the local area optimization  110  accordingly to a certain SON scheme would determine that it would be better to change the first parameter to another value and also to change a second parameter in the second base station to another value. In this case, the base station  100  knows that the first parameter cannot be changed and this could also lead to the fact that the second parameter in the second base station  102  should be optimized to a different value or should not be changed. 
         [0038]    If the local area optimization algorithm  110  determines to change a second parameter of the second base station  102 , a second message  112  is transmitted from the first base station  100  to the second base station  102 . Additionally the first base station  100  transmits a third message  114  to the second base station  102 . The third message is indicative of the first parameter of the first base station  100  being fixed. The third message may also be referred to as the first signal. Thus, the second cell also knows that the first parameter in the first cell is fixed and cannot be changed. The value of the first parameter is also transmitted via the third message  114 . The knowledge about the first parameter and the value of the first parameter in the second base station  102  may be used for an optional additional optimization algorithm in the second base station  102 . 
         [0039]    In step  116  the second base station  102  changes the second parameter to the value indicated in the second message  112 . This step is performed analogously to step  108  in the first base station  100 . Additionally, the second base station  102  may run another optimization algorithm for optimizing further parameters in the second cell and/or a neighboring cell of the second cell. 
         [0040]      FIG. 2  is a schematic view of another embodiment of a method according to the invention. Shown again is a wireless telecommunication network with a first base station  100 , a second base station  102  and a network entity  104  in a schematic view. The wireless telecommunication system of  FIG. 2  is similar to the system of  FIG. 1 . Usually parameters in the wireless telecommunication system are set by an SOM scheme and an external intervention, e.g. by a human, is possible by setting a first fixed parameter via network entity  104 . The first fixed parameter is transmitted in a first message  106  to the first base station  100  as already explained in  FIG. 1 . The first base station  100  then changes the first parameter to the newly received value in step  108  or—if that value was previously already configured—then this value is kept but it is marked to be fixed and non-changeable. At this point the second base station does not know, that the first base station has this parameter fixed. Then the second base station  102  sends a parameter change command  200  to the first base station  100 . The parameter change command  200  is indicative of changing the first parameter in the first base station  100 . The parameter change command  200  may be sent for example by the second base station  102  to the first base station  100  after an optimization algorithm performed in the second base station  102 . The parameter change command  200  may also be referred to as the second signal. 
         [0041]    In step  202  the first base station  100  decides not to accept the parameter change command  200  because the first parameter is stored as being fixed in the first base station  100 . In other words the parameter change command is refused by the first base station  100 . The first base station  100  then transmits a fourth message to the second base station  102 . The fourth message  204  is indicative of the refusal of the change command. The fourth message may also be indicative of the value of the fixed first parameter. The fourth message  204  may also be referred to as the third signal. Thus, the second base station  102  knows after having received the fourth message  204  that the first parameter is fixed in the first base station  100  and the value of this fixed parameter. As explained in  FIG. 1  this knowledge may be used in further optimization algorithms performed in the second base station  102 . 
         [0042]    In step  206  the second base station  102  stores information about the value of the first parameter in the first base station  100  and the fact that it is a fixed parameter. Then, the second base station  102  analyzes the situation without the parameter change and possibly restarts a new optimization algorithm taking into account the value of the first parameter and the fact that this parameter is not changeable. 
         [0043]      FIG. 3  is a schematic view of a wireless telecommunication network similar to the wireless telecommunication network of  FIG. 2 . The operation and maintenance center  104  sets a first parameter of the first base station  100  by transmitting first message  106 . the first parameter is then changed in step  108  and after changing the first parameter the first base station  100  receives a parameter change command  200  from the second base station  102 . 
         [0044]    Then, in step  202  the first base station  100  refuses to change the first parameter because it is a fixed parameter. It is to be noted that the first base station  100  does not transmit the refusal to the second base station  102 . The first base station  100  simply ignores the parameter change command in step  202 . 
         [0045]    After some time the second base station  102  detects in step  300  that the first base station  100  did not change the first parameter. This may for example be detected because the first base station  100  informs the second base station  102  regularly about its parameters or because the second base station  102  did not receive information about the parameter change in the first base station  100  as it would have been the case if the first base station  100  would have changed the first parameter. Then, in step  302  the second base station assumes that the first parameter is fixed in the first base station  100  and stores this information. This assumption will be rechecked again after a certain time period. After this time period the second base station  102  considers that the parameter may no longer be fixed and keeps this parameter flexible again within subsequent optimization procedures. This then may lead again to that the second base station sends again a parameter change command  200  to the first base station  100 . 
         [0046]    Then, the second base station  102  reruns a local area optimization  206  taking into account the value of the first parameter of the first base station  100  and the fact that the first parameter of the first base station  100  is fixed. This step is performed analogously to step  206  in  FIG. 2 . 
         [0047]      FIG. 4  is a block diagram of a wireless telecommunication network  400  comprising a first base station  100 , a second base station  102 , a wireless terminal  402 , and a network entity  104 . The wireless terminal  402  may for example by a mobile phone, a mobile computer or a PDA. The first base station  100  and the second base station  102  both have each a first interface  404  for communicating with the other base stations, a processor  406 , a data storage  408 , and a second interface  410  for communicating with the network entity  104 . The processor  406  is adapted to execute a program  412 . The program  412  is stored in the respective data storage  408 . The network entity  104  comprises a third interface for communicating with the first base station  100  and the second base station  102 . The first base station  100  and the second base station  102  communicate with the wireless terminal  402  via a respective antenna  416 . 
         [0048]    In operation, the first and the second base stations are adapted to adjust their wireless telecommunication parameters on their own in a self-organizing manner. This self-organizing network algorithm is performed by executing program  412  in data storage  408  by processor  406 . The network entity  104  communicates with the first base station  100  and the second base station  102  via interfaces  410  and  414 . The network entity is adapted for sending a first message to the first base station  100 , the first message being indicative of setting a first parameter to a fixed value. Then, this parameter is stored as being fixed in data storage  408 . Further optimization algorithms according to self-organizing network schemes may be performed by processor  406  in base station  100  and/or by processor  406  in base station  102 . If a parameter shall be changed according to an optimization algorithm the respective base station transmits a signal via interfaces  404 . All parameters may be changed, which are not denoted as being fixed. When a fixed parameter from the first base station  100  shall be changed it is not changed and optionally an error message is transmitted from base station  100  to base station  102  via interfaces  404 . After a certain time period the fixed parameter is not fixed anymore. In this case the information about the first parameter being fixed is deleted from data storage  408  in first base station  100 . 
       LIST OF REFERENCE NUMERALS 
       [0049]      
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 100 
                 First base station 
               
               
                 102 
                 Second base station 
               
               
                 104 
                 network entity 
               
               
                 106 
                 First message 
               
               
                 108 
                 Change parameter 
               
               
                 110 
                 Local area optimization 
               
               
                 112 
                 Second message 
               
               
                 114 
                 Third message 
               
               
                 116 
                 Change parameter 
               
               
                 200 
                 Parameter change command 
               
               
                 202 
                 Parameter change refusal 
               
               
                 204 
                 Fourth message 
               
               
                 206 
                 Local area optimization 
               
               
                 300 
                 Detection of refusal 
               
               
                 302 
                 Assumption 
               
               
                 400 
                 wireless telecommunication network 
               
               
                 402 
                 Wireless terminal 
               
               
                 404 
                 First interface 
               
               
                 406 
                 Processor 
               
               
                 408 
                 Data storage 
               
               
                 410 
                 Second interface 
               
               
                 412 
                 Program 
               
               
                 414 
                 Third interface 
               
               
                 416 
                 Antenna