Abstract:
The present invention relates to a method and arrangement in a telecommunication system, in particular to methods and arrangements for supporting maintenance activities of units in a telecommunication network.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method and arrangement in a telecommunication system, in particular to methods and arrangements for supporting maintenance activities of units in a telecommunication network. 
       BACKGROUND 
       [0002]    Telecommunication networks, e.g. as illustrated in  FIG. 1 , typically consist of a large number of network units responsible for providing communication services to and from user equipments connected to said network. The coverage area of the radio base stations thereby constitutes the geographical area that can be served by such a network, whereby the placement of radio base stations depends on many factors, e.g. the shape of geographical area, traffic density, etc. 
         [0003]    In order to guarantee a proper working of the network but also for improving service range and service quality in the network, it is necessary to perform, e.g. regularly or at suitable instances, various maintenance tasks in the network units. This implies inter alia software maintenance and upgrades but also error corrections or fine-tuning of parameters for improved network performance. It is thus necessary to take network units out of service during such maintenance which implies, in particular with regard to the radio base stations, that a certain geographical area will have no or reduced radio coverage during the maintenance time. This locally reduced network performance will also impact neighbouring radio base stations. 
         [0004]    It is perceived to be a problem that networks at regular times will have reduced coverage and experience increased radio traffic disturbances. 
         [0005]    Handling the impact of such problems needs either planning of the maintenance activities by the network operator or needs already be taken into consideration in advance when designing the network. For instance, the network operator can apply a randomised scheme or individually trigger according to a planned sequence radio base stations that are temporarily out of order for maintenance activity. However, these measures only can lead to a reduced impact of maintenance activities which is, e.g. in case of a randomised scheme, not entirely under the control of the network operator. 
         [0006]    Known solutions of network management services refer to distributed and policy-based procedures with self-configuration capabilities where the network entities in the system can be seen as a potential manager for a set of local (re-)configuration tasks. 
       SUMMARY 
       [0007]    It is an object of embodiments of the present invention to overcome the problems as described above. This is achieved by the teaching of claims  1  and  8 . Dependent claims describe further embodiments of the invention. 
         [0008]    Briefly, it is the basic concept of the present invention that all or parts of the network units, e.g. radio base stations, in a telecommunication network are ordered to perform a software maintenance activity; however, without prescribing a certain order for performing these activities. A network unit thus informs its neighbour network units that it intends to perform the maintenance activity where after the neighbour network units will postpone their maintenance activities until the radio base station is back in full operation. 
         [0009]    The present invention allows the advantage that only one network unit among several neighboured network units is out of order for maintenance activities whereby the surrounding network units can handle at least parts of the possible traffic for the maintenance network units which otherwise would be lost. 
         [0010]    The present invention also implies the advantage that network maintenance is considerably simplified for the network operator. 
         [0011]    Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates a part of a telecommunication network including a plurality of network units. 
           [0013]      FIGS. 2   a - 2   d  illustrate signalling diagrams of the embodiments of the present invention. 
           [0014]      FIG. 3  shows a flow chart of the method according to an embodiment of the present invention for a network unit that intends to perform maintenance activities. 
           [0015]      FIG. 4  shows a flow chart of the method according to an embodiment of the present invention for a network unit in its role as a neighbour network unit of a network unit that intends to perform maintenance activities. 
           [0016]      FIG. 5  illustrates an arrangement according to the present invention adapted to perform the embodiments of the method according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    In the description of the embodiments according to the present invention the following expressions are used: Telecommunication network  10 : The embodiments of the present invention are applicable to any kind of fixed network or radio access network, e.g. a UTRAN or evolved UTRAN. 
         [0018]    Network unit  11 , 12 : Denotes an arrangement of the telecommunication network that is responsible to support communication services in said network. This can be, e.g., a radio base station, a general packet radio service support node, a mobility management entity, a location register. 
         [0019]    Neighbour network unit  12   a , 12   b : Denotes a network unit as described above, which network unit can, at least partly, take over tasks over another network unit  12 . For instance, a neighbour radio base station  12   a  is another base station covering partly the same geographical area and can thus serve user equipments  13  in the overlapping area. 
         [0020]    Maintenance activities: Denotes, in general, service activities in a network unit  11 , 12  that will make it necessary to temporarily take the unit out of order from its normal services. The activities can relate to software upgrades, maintenance, or error corrections. 
         [0021]    The present invention addresses the situation that an operator of a telecommunication network  10  as described in  FIG. 1  needs to perform maintenance activities for one or more network units  11 , 12  which will make it necessary to take said units out of service for a certain time period. This is specified by defining all or a group of network units for said maintenance together with a time window, e.g. one week, within which the network units shall initiate this activity. In an embodiment of the present invention, the operator may also specify one or more network units that start the maintenance activity. All involved network units thus receive the same maintenance request from the operator, which is not individually adapted to the specific network units. 
         [0022]      FIGS. 2   a - 2   d  show signalling diagrams illustrating the present invention with radio base stations as an example of network units. The signalling may be sent over suitable interfaces in said telecommunication network. For instance, in an evolved UTRAN the interfaces S 1  or X 2  can be applied. In  FIG. 2   a , a radio base station RBS 1  that is going to perform software maintenance activities sends a maintenance indication message  21  to all its neighbour base stations RBS 2  . . . n. Embodiments of the present invention include, e.g., that the maintenance indication includes a time value [T 5 ] of the exact or estimated time during which the radio base station will be out of order due to maintenance. Alternatively, no explicit time value is indicated but instead a normal maintenance downtime period is commonly known by the radio base stations. 
         [0023]    The radio base station of each neighbour cell responds after reception of the maintenance indication message  21  with a maintenance acceptance message  22 . In embodiments of the present invention, the reception message can contain an indication that the neighbour base station is currently operable and will remain so during the maintenance period of RBS 1 . After having performed its maintenance activities  25 , RBS 1  sends a maintenance completed message  23  indicating that RBS 1  is fully operable again and, thus, that one of the neighbour base stations could start its maintenance procedures. Also the receipt of this message is confirmed by each of the neighbour radio base stations by a maintenance completed confirm message ( 24 ). 
         [0024]    The fact that network maintenance is handled in a decentralised way by the individual radio base stations implies that within a time period T R  several radio base stations can intend to start their maintenance activities. This is illustrated in  FIG. 2   b . A maintenance indication message  21 , e.g. sent by RBS 1 , can thus during this time period collide with corresponding maintenance indication messages  21   a  sent by neighbored radio base stations. The time period T R  is defined by the message roundtrip time (the accumulated time it takes for a message to be transmitted from a first unit to a second unit, back from said second unit to the first unit, and the processing time in said second unit). Therefore, the embodiments of the present invention can provide for mechanisms to resolve such collisions, e.g. as depicted in  FIG. 2   b . In case the radio base station RBS 1  receives a maintenance indication message  21   a  from one of the neighbour radio base station RBS 2  . . . n after having sent an own maintenance indication message  21  but before having received a maintenance acceptance message  22  from said neighbour base station, the radio base station RBS 1  aborts  26  its request for maintenance and starts a randomised timer with a value selected from an interval [T 2 ;T 3 ] where T 2  denotes a time at least equal to or larger than the message roundtrip time T R  between the neighbour base stations and where T 3  denotes a suitably selected time larger than T 2 . As apparent from  FIG. 2   b , also other neighbour radio base stations RBS 2  . . . n that were involved in the collision abort  26   a  their maintenance request and wait a randomised time as described above. After the randomly determined time has expired, each of the radio base stations involved in the collision can again try to send a maintenance indication message  21   b  (unless it did not already receive a maintenance indication message from another radio base station). 
         [0025]    Embodiments of the present invention also need to provide mechanisms to handle situations where one or more of the messages introduced in  FIG. 2   a  do not reach the recipient.  FIG. 2   c  depicts the case where no response message  22   a  or  24   c  has been received. This implies of course also the case where the message that should trigger such response message did not reach the unit to respond. 
         [0026]    In case no maintenance acceptance message  22   a  has been received in response to a maintenance indication message  21  (or in case the maintenance indication message  21  did not reach a neighbour radio base station), the requesting radio base station RBS 1  waits for a time T 4 , which has at least the length of the roundtrip time T R , before retransmitting  21   c  its maintenance indication message. This procedure can be repeated one or several times; however, if no maintenance accepted message  22  has finally been received within a time which has at least the length of the roundtrip time T R  plus the normal maintenance downtime period, the radio base station continues with its maintenance activities as if an accept message had been received. 
         [0027]    There will be a difference in time of arrival for the maintenance acceptance messages from different neighbour RBSs. This difference in time means that the maintenance activity in RBS 1  will start later than anticipated by the neighbour RBSs that sent their maintenance acceptance messages before. By resending the maintenance indication message to one or more of the neighbour RBSs answering first, the RBS 1  may prohibit that any RBS will assume that the maintenance is finished, timer T 5  has elapsed, and start their own maintenance activity before RBS 1  is back in operation. 
         [0028]    In case no response  24   c  has been received after having sent a maintenance completed message  23   c , the complete message  23   c  can be re-sent one or several times. 
         [0029]      FIG. 2   d  depicts the case where a radio base station RBS 1 , after having sent a maintenance acceptance message  22   d , does not receive any maintenance complete message  23   d  within a time interval T 5 , where T 5  denotes a time that is longer than any normal maintenance activity. Then the radio base station RBS 1  can after expiry of the time period T 5  initiate its own maintenance activities by sending a maintenance indication message  21   d.    
         [0030]      FIG. 3  shows a flow chart of the method according to an embodiment of the present invention for a network unit  12  that intends to perform maintenance activities. The network unit transmits  31   a  maintenance indication message  21  to its neighbour network units  12   a , 12   b . When maintenance acceptance messages have been received  32 Yes from said neighbour network units, the network unit  12  performs  33  its maintenance and transmits  34  a maintenance completed message  23  when finished. The network unit can await  35  maintenance completed confirm messages  24  from the neighbour network units  12   a , 12   b  and, if such messages are not received in time  35 Yes re-transmit  36  said maintenance completed messages. Where no maintenance acceptance messages have been received  32 No from at least one of the neighbour network units  12   a , 12   b  (e.g. because the indication or acceptance message got lost during transmission or one or more neighbour network units has transmitted a maintenance indication message before having received the maintenance indication message of the network unit), the maintenance process is aborted  37  and the network unit starts  38  a randomised timer and waits this time until re-transmitting a maintenance indication message. 
         [0031]      FIG. 4  shows a flow chart of the method according to an embodiment of the present invention for a network unit in its role as a neighbour network unit of a network unit that intends to perform maintenance activities. On reception  41 Yes of a maintenance indication message  21  the network unit shall transmit back  42  a maintenance acceptance message  22  and suppress own maintenance activities during the time specified for maintenance of the requesting network unit. On reception  43 Yes of a maintenance completed message  23  the network unit shall re-transmit  44  a maintenance completed confirm  24  message. 
         [0032]      FIG. 5  illustrates an arrangement  51  adapted to perform the embodiments of the method according to the present invention and supports maintenance activities of said network unit  12  which are controlled by a maintenance activity control unit  52 . 
         [0033]    The arrangement  51  includes a timer  55  adapted to measure a randomly selected time and electronic circuits whereof
       a first electronic circuitry  53  is adapted to provide  531   a  maintenance indication message  21  to be transmitted to neighboured network units after having received an indication  535  to start maintenance activity; to await  532  a maintenance acceptance message  22  from said neighboured network units; to indicate  534  to turn off service provision and perform said maintenance activities; and to provide  533  a maintenance completed message  23  after said maintenance activity when ready for operation;   a second electronic circuit  54  is adapted to provide  541   a  maintenance acceptance message  22  to a neighboured network unit  12   a , 12   b  in response to a received message  21  indicating a transit to a maintenance state; and to provide  542  a maintenance completed confirm message  24  to a neighboured network unit  12   a , 12   b  in response to a received message  23  indicating a transit from a maintenance state.   a third electronic circuitry  56  is adapted to provide  561  an indication to abort the maintenance process when no maintenance acceptance message is received from a neighbour unit  12   a , 12   b  in a direct response to a transmitted maintenance indication message  21 ; and to start  562  a randomised timer  55  and wait until said timer has expired before re-sending a maintenance indication message  21 .