Method and Arrangement for Connection Re-Establishment in a Telecommunication System

Abstract

The invention relates to a method in a user equipment and a user equipment (700) for controlling connection re-establishment between said user equipment and a network. The method comprises the steps of receiving (501) a configuration message from the network defining at least one condition; upon detection of connectivity problems (503) towards the first cell, evaluating said at least one condition (504); if said at least one condition is fulfilled for a neighboring cell (B), applying at least one special criterion for initiating connection re-establishment to said neighboring cell (505), said at least one special criterion being different from at least one criterion that is applied if said at least one condition is not fulfilled. The invention furthermore relates to a method and an arrangement in a network node (800) for controlling connection re-establishment between the network and a user equipment (700).

Claims

1-41. (canceled)

42. A method in a user equipment (UE) for connection re-establishment with a network, the UE being served in a first cell, the method comprising: receiving a configuration message from the network, the configuration message including one or more conditions for applying a fast re-establishment procedure, wherein the one or more conditions are based on a quality of a received signal from a neighboring cell; and upon detection of connectivity problems towards the first cell, applying the fast re-establishment procedure or a normal re-establishment procedure with respect to the neighboring cell depending on whether at least one condition of the one or more conditions are fulfilled for the neighboring cell, wherein the fast re-establishment procedure and the normal re-establishment procedure are each associated with one or more of a timer value and a counter value for performing re-establishment and one or more of the timer value and the counter value for the fast re-establishment procedure is less than the respective timer value and counter value associated with the normal re-establishment procedure.

43. The method according to claim 42, wherein at least one condition of the one or more conditions is that the received signal from the neighboring cell indicates the UE is within coverage of the neighboring cell.

44. The method according to claim 42, wherein at least one condition of the one or more conditions is that a measurement of the received signal from the neighboring cell is above a threshold value.

45. The method according to claim 42, wherein at least one condition of the one or more conditions is that the received signal from the neighboring cell triggers a measurement event or measurement report for the neighboring cell.

46. The method according to claim 42, comprising receiving a message from the network comprising an indication of at least one cell for which the one or more conditions apply.

47. A method in a network node for connection re-establishment between a user equipment (UE) and a network, the UE being served in a first cell, the method comprising: sending a configuration message to the UE, the configuration message including one or more conditions for applying a fast re-establishment procedure, wherein the one or more conditions are based on a quality of a received signal from a neighboring cell; and configuring the UE to apply the fast re-establishment procedure or a normal re-establishment procedure with respect to the neighboring cell depending on whether at least one condition of the one or more conditions are fulfilled for the neighboring cell, wherein the fast re-establishment procedure and the normal re-establishment procedure are each associated with one or more of a timer value and a counter value for performing re-establishment and one or more of the timer value and the counter value for the fast re-establishment procedure is less than the respective timer value and counter value associated with the normal re-establishment procedure.

48. The method according to claim 47, wherein at least one condition of the one or more conditions is that the received signal from the neighboring cell indicates the UE is within coverage of the neighboring cell.

49. The method according to claim 47, wherein at least one condition of the one or more conditions is that a measurement of the received signal from the neighboring cell is above a threshold value.

50. The method according to claim 47, wherein at least one condition of the one or more conditions is that the received signal from the neighboring cell triggers a measurement event or measurement report for the neighboring cell.

51. The method according to claim 47, comprising transmitting a message to the UE comprising an indication of at least one cell for which the one or more conditions apply.

52. The method according to claim 51, wherein the indication of the at least one cell for which the one or more conditions apply is based on prior connectivity problems with the at least one cell.

53. The method according to claim 52, further comprising transmitting an indication to the at least one cell to prepare for a connection re-establishment from the UE.

54. A user equipment (UE) capable of connection re-establishment with a network, the UE being served in a first cell, the UE comprising processing circuitry operable to: receive a configuration message from the network, the configuration message including one or more conditions for applying a fast re-establishment procedure, wherein the one or more conditions are based on a quality of a received signal from a neighboring cell; and upon detection of connectivity problems towards the first cell, applying the fast re-establishment procedure or a normal re-establishment procedure with respect to the neighboring cell depending on whether at least one condition of the one or more conditions are fulfilled for the neighboring cell, wherein the fast re-establishment procedure and the normal re-establishment procedure are each associated with one or more of a timer value and a counter value for performing re-establishment and one or more of the timer value and the counter value for the fast re-establishment procedure is less than the respective timer value and counter value associated with the normal re-establishment procedure.

55. The user equipment according to claim 54, wherein at least one condition of the one or more conditions is that the received signal from the neighboring cell indicates the UE is within coverage of the neighboring cell.

56. The user equipment according to claim 54, wherein at least one condition of the one or more conditions is that a measurement of the received signal from the neighboring cell is above a threshold value.

57. The user equipment according to claim 54, wherein at least one condition of the one or more conditions is that the received signal from the neighboring cell triggers a measurement event or measurement report for the neighboring cell.

58. The user equipment according to claim 54, the processing circuitry further operable to receive a message from the network comprising an indication of at least one cell for which the one or more conditions apply.

59. A network node capable of connection re-establishment between a user equipment (UE) and a network, the UE being served in a first cell, the network node comprising processing circuitry operable to: send a configuration message to the UE, the configuration message including one or more conditions for applying a fast re-establishment procedure, wherein the one or more conditions are based on a quality of a received signal from a neighboring cell; and configure the UE to apply the fast re-establishment procedure or a normal re-establishment procedure with respect to the neighboring cell depending on whether at least one condition of the one or more conditions are fulfilled for the neighboring cell, wherein the fast re-establishment procedure and the normal re-establishment procedure are each associated with one or more of a timer value and a counter value for performing re-establishment and one or more of the timer value and the counter value for the fast re-establishment procedure is less than the respective timer value and counter value associated with the normal re-establishment procedure.

60. The network node according to claim 59, wherein at least one condition of the one or more conditions is that the received signal from the neighboring cell indicates the UE is within coverage of the neighboring cell.

61. The network node according to claim 59, wherein at least one condition of the one or more conditions is that a measurement of the received signal from the neighboring cell is above a threshold value.

62. The network node according to claim 59, wherein at least one condition of the one or more conditions is that the received signal from the neighboring cell triggers a measurement event or measurement report for the neighboring cell.

63. The network node according to claim 59, the processing circuitry further operable to transmit a message to the UE comprising an indication of at least one cell for which the one or more conditions apply.

64. The network node according to claim 63, wherein the indication of the at least one cell for which the one or more conditions apply is based on prior connectivity problems with the at least one cell.

65. The network node according to claim 64, the processing circuitry further operable to transmit an indication to the at least one cell to prepare for a connection re-establishment from the UE.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The foregoing and other objects, features and advantages of the invention will be apparent from the following detailed description of preferred embodiments as illustrated in the drawings.

[0056] FIG. 1 shows a simplified signaling diagram illustrating the LTE handover procedure;

[0057] FIG. 2 shows how Radio Link Failure, RLF is declared in LTE;

[0058] FIG. 3 shows how RLF is monitored in LTE:

[0059] FIG. 4 illustrates the concept of handover regions of pico/macro vs macro/macro cell change;

[0060] FIG. 5 shows a flowchart of a method embodiments according to embodiments performed in a user equipment;

[0061] FIG. 6 shows a flowchart of a method embodiments performed in a network node;

[0062] FIG. 7 shows schematically a user equipment according to embodiments;

[0063] FIG. 8 shows schematically an arrangement in a network node according to embodiments; and

[0064] FIG. 9 shows a user equipment moving from the coverage of a pico-cell into the coverage of a macro cell.

DETAILED DESCRIPTION

[0065] In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, interfaces, techniques, etc. in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary details.

[0066] Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification are not necessarily all referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0067] The present invention is described within the context of E-UTRAN, also referred to as LTE. It should be understood that the problems and solutions described herein are equally applicable to wireless access networks and user equipments, user equipment's implementing other access technologies and standards. LTE is used as an example technology where the invention is suitable, and using LTE in the description therefore is particularly useful for understanding the problem and solutions solving the problem.

[0068] Various alternative embodiments for implementing the invention will be described in the following using non-exclusive examples.

[0069] Consider a user equipment in connected mode implementing network controlled mobility and connected to a first cell, e.g. a pico-cell. With the notation “connected to a cell”, it should be noted that this implies that the user equipment is configured to send and/or receive data in at least this cell. Sometimes, this cell is also called “serving cell”, or “primary cell”, PCell. The cell is typically controlled by one network node such as a radio base station, which means that “connected to a cell” is in this respect equivalent to the user equipment being “connected to a first radio base station”, that is, the radio base station that is in control is of the aforementioned cell. Sometimes, this radio base station is called Serving eNB or serving radio base station.

[0070] In the example, the pico-cell is “surrounded” by a macro-cell that provides coverage in a much larger area, see FIG. 9. When the user equipment is moving out from the coverage of the small pico cell it is quickly loosing coverage of the pico cell that it is currently connected to, see FIG. 4. In such situation, there would be a rather high likelihood that the user equipment will loose connectivity to the pico-cell before a handover is completed, which means that the user equipment will experience a radio-link failure resulting in an undesired interruption in connectivity, as previously described.

[0071] The same problem could also occur if a user equipment moves from a macro cell to another cell, e.g. a pico-cell, where there is a very short handover region. The problem would be further exaggerated if the user equipment moves with a high speed.

[0072] Embodiments of the invention provide a possibility to bypass the ordinary, or “normal”, evaluation of radio link failure for performing connection re-establishment in a particular neighboring cell provided at least one certain condition is fulfilled for said cell.

[0073] FIG. 5 schematically illustrates method steps performed by a user equipment, UE, according to embodiments of the invention, said user equipment being served in a first cell, which in this example is the pico cell. In step 501, the user equipment receives a configuration message from the network defining at least one condition to be evaluated by the user equipment upon detection of connectivity problems towards the first cell. Said configuration message may be received on a broadcast channel or via dedicated signaling.

[0074] Said condition may be related to determining if the user equipment is within the coverage of any neighboring cell. The evaluation of whether the user equipment is within the coverage of a neighboring cell may be based on whether a received signal from a neighboring cell is stronger than a particular value e.g. a threshold value. Various quality parameters for defining the “strength” of such a received signal can be implemented, for example received signal power measurements and pathloss-related and interference related measurement criteria. This includes for example Reference symbol received power (RSRP) and Reference symbol received quality (RSRQ).

[0075] The network may configure the user equipment with a threshold or thresholds that defines whether the user equipment should consider itself within the coverage region of an indicated cell. The network may also configure the user equipment with a quality parameter to be used by the user equipment when evaluating whether the user equipment is within the coverage region of an indicated cell. If for example the RSRQ of an indicated cell in the example outlined above is greater than x dB, where x represents a configured threshold value, then the user equipment consider itself within the coverage region of that cell.

[0076] If the user equipment identifies that said at least one condition is fulfilled for multiple neighboring cells, e.g. that it is within coverage of multiple cells, there may be additional criteria for prioritizing the selection among those. For example, the user equipment may select the best one, where “best” is defined in terms of the measured criterion above, e.g. such that the cell with the strongest signal or best signal quality is selected. Alternatively, there could be additional priority criteria defined, such as a relative priority among cells comprised in a neighboring cell list, or offsets defining e.g. that cell A, or cells on frequency layer F_A should be selected if the cell or cells are x dB better in terms of the measured criterion when compared to another cell B or cells on another frequency layer F_B.

[0077] As the user equipment moves out from the coverage region of the first cell, which is the pico-cell in this example, it will detect physical layer problems or other problems related to the connectivity towards the first cell, i.e. the pico-cell, see step 503. The detection of physical layer problems may comprise receiving an out-of-sync indication from the physical layer or reading Reference Signal Received Power, RSRP, or Reference Signal Received Quality, RSRQ, below a certain absolute level towards the first cell. The network may configure the user equipment with a threshold or thresholds for RSRP or RSRQ that defines whether the user equipment should consider the connection to the source cell to be problematic. According to another alternative, detection of connectivity problems towards the first cell comprises the step of starting a timer when a measurement event related to a handover is triggered, and if no handover has been executed before the timer expires, connectivity problems are detected.

[0078] In step 504, the user equipment evaluates whether said at least one condition is fulfilled. Said condition may as already mentioned be related to determining whether the user equipment is within the coverage of a neighboring cell. The evaluation is done by checking if certain one or more conditions related to a neighboring cell are fulfilled as will be further described below. In such case, the user equipment will implement a fast connection re-establishment to such cell by applying the special criteria or criterion for initiating connection re-establishment in said cell, see step 505.

[0079] In a particular embodiment a condition is fulfilled when a received signal from said neighboring cell is stronger than a threshold value.

[0080] According to an alternative embodiment, a condition is fulfilled if a measurement event, e.g. A3, is triggered for said neighboring cell. Alternatively, a condition is fulfilled for a neighboring cell if a measurement report is transmitted to the network indicating that a measurement event is triggered for a neighboring cell. According to yet another alternative, a condition is fulfilled for a neighboring cell if an acknowledgment of a successfully transmitted measurement report indicating that a measurement event is triggered for a neighboring cell is received from the network.

[0081] A benefit of embodiments where the condition is tied to a measurement event that is already defined for the user equipment is that no new measurement of a target cell needs to be defined.

[0082] A benefit of the two latter embodiments, i.e. where a condition is fulfilled when a report is transmitted and an acknowledgment of the same is received respectively, is that they allow the network to be aware of the user equipments intentions to move to the neighboring cell which in this case is the target cell, and can initiate needed preparations, such as target cell preparation. It should be noted that the A3 event is merely an example and that other measurement events may be applied in the context of different embodiments.

[0083] If said at least one condition is fulfilled for a neighboring cell, then at least one special criterion for initiating connection re-establishment to said neighboring cell is applied, according to step 505. Said special criterion is different from at least one criterion for initiating connection re-establishment that would be applied if said at least one condition had not been fulfilled.

[0084] If said at least one condition is not fulfilled for a neighboring cell, the user equipment shall apply the normal criterion or criteria for initiating connection re-establishment, see step 505, and possibly do a normal re-establishment procedure based on e.g. regular cell selection procedures.

[0085] In an optional step 507, the user equipment receives, from the network, an indication of at least one cell for which said at least one special criterion should apply, provided that the at least one condition is fulfilled. Said indication may in some embodiments be comprised in the configuration message received in step 501.

[0086] The indication of at least one cell provided to the user equipment in step 501 or 507 may be in different forms. According to a specific embodiment, said indication comprises an indication of all neighboring cells of the first cell. In this case, there is no need to specifically indicating, or pinpointing, particular cells, but there is merely an indication sent from the network to one or more user equipment stating that the user equipment shall apply the special criterion or criteria allowing the fast re-establishment solution whenever said at least one specific condition for fast re-establishment procedure is fulfilled.

[0087] According to another specific embodiment, said indication comprises an indication of a particular frequency layer such that all neighboring cells on said frequency layer are indicated. This means that in case the at least one condition is fulfilled, the user equipment should apply the fast connection re-establishment solution towards cells on a particular frequency layer provided that said at least one condition is fulfilled, but not on another frequency layer. Also in such cases, there may be no need to indicate particular cells on the layer, since all neighbor cells on the particular frequency layer are indicated with a single indication.

[0088] According to yet another specific embodiment, said indication comprises a list of indicated cells, towards which the user equipment shall perform a fast re-establishment of the connection in case the at least one condition is fulfilled. In case the indication is provided in the form of a list of cells, the cells in the list would be indentified by a cell identification, typically by their physical cell identity, PCI, but other indexes or identification methods for identifying the cells in the list may also apply. Such list may also comprise an indication of which frequency layer a cell indicated by said identification is to be found on.

[0089] The indication provided in step 507 may be provided to the user equipment on a broadcast channel, BCCH in LTE terminology, or it may be provided by dedicated signaling, where a message is sent to a particular user equipment or group of user equipments, but not to all user equipments in that cell. Broadcast signaling typically implies that the message or messages are sent to some or all user equipments within the coverage of a cell. The messages are then often repeated periodically, so that user equipments entering the cell can receive the message or messages at the next opportunity. Dedicated signaling from the network typically implies that the message is directed to one particular receiver or group of receivers, by specifically addressing this user equipment or group of user equipments in the transmission of the message. Thus, the message may be sent only once followed by an acknowledgment from the receiving user equipment.

[0090] The application of criterion or criteria to be fulfilled for initiating connection re-establishment may in some embodiments include the use of counters and or timers to evaluate when the user equipment shall initiate connection re-establishment in an indicated cell. The counters and/or timers may be the same as those used in “normal” recovery procedures. For example, the network configures the user equipment with a counter value N310 equal to 10 and a timer expiration value T310 equal to 500 milliseconds. A “normal” connection re-establishment is then initiated after 10 consecutive “out-of-synch” indications followed by the starting and expiry of a timer T310, i.e. followed by a 0.5 second waiting time. Only then, the user equipment selects a cell towards which the user equipment performs a re-establishment request.

[0091] According to a particular embodiment, re-establishment is initiated to a neighboring cell immediately when said at least one condition is fulfilled for that cell. This means that the re-establishment is initiated as soon as said at least one condition is fulfilled, i.e. no additional criteria for initiating connection re-establishment is applied. Such embodiment will be explained using the following non-limiting example:

[0092] A user equipment is configured by the network to initiate connection re-establishment towards a certain neighboring cell upon detection of connectivity problem towards its serving cell in case an A3 event has been triggered for said neighboring cell. Let us assume that the connectivity problem is detected by reception of an out-of-synch indication from the physical layer. According to this particular embodiment, the user equipment will then stop the counter N310 counting out-of synch indications from the physical layer or timer T310 controlling radio link failure and immediately initiate connection re-establishment towards the neighboring cell for which the A3 event has been triggered, i.e. towards the target cell.

[0093] In an alternative example embodiment, said at least one special criterion include expiration of a timer at a certain expiration value, said expiration value being different from an expiration value of said timer that is applied for “normal” connection re-establishment, i.e. if said at least one condition had not been fulfilled, and/or reaching a threshold value of a counter, said threshold being different from a threshold value for said counter that is applied if said at least one condition had not been fulfilled, i.e. for normal connection re-establishment. Thus, the user equipment may implement and use different values of timers and/or counters to evaluate when the user equipment shall initiate a connection re-establishment when said at least one condition has been fulfilled.

[0094] Thus, according to embodiments of the present invention, the user equipment may perform an RRC connection re-establishment to a neighboring cell prior to finalizing the counting and expiry of the timer, e.g. T310, according to a “normal” connection re-establishment procedure, provided that the at least one condition is fulfilled.

[0095] For example, the counter threshold value may as a special criterion be set to 3, such that the special criterion implies that the user equipment may initiate a re-establishment towards a neighboring cell for which said at least one condition is fulfilled after 3 “out-of-synch” indications. Alternatively, or in addition, the timer expiration value may as another special criterion be set to 100 milliseconds, such that the user equipment may initiate the re-establishment towards a neighboring cell for which said at least one condition is fulfilled after 100 milliseconds from starting T310.

[0096] In another alternative embodiment, said at least one special criterion involves the use of at least one different counter and/or timer in addition to at least one counter and/or timer used for “normal” initiation of connection re-establishment, said different counter and/or timer govern when the user equipment is allowed to initiate re-establishment of the connection to a cell for which the condition is fulfilled. For example, initiation of re-establishment in a cell for which the condition is fulfilled could be associated with a counter value “3” of a counter N410, and a timer-value “100 ms” of a timer “T410”. The naming of the timers and counters should be seen as examples only and do not imply any limitations to the applicability of embodiments of the invention. The same counter “N410” and timer “T410” could be used for governing the recovery to all neighboring cells. There could also be separate values for the counter and timer of each neighboring cell or group of neighboring cells.

[0097] Numerous variations and combinations are possible. Values of counters and timers for evaluating when the user equipment should attempt to re-establish the connection to a neighboring cell, both for the cases when the at least one condition is fulfilled or not fulfilled, could in some embodiments be configurable by the network, see optional steps 502 in FIGS. 5 and 603 in FIG. 6.

[0098] Embodiments of the present invention also includes the network aspects for configuring the user equipment with at least one condition to evaluate in order to determine if a user equipment shall implement a fast connection re-establishment procedure towards a particular neighboring cell. On the network side, the rationale of providing such at least one condition to be evaluated upon detection of connectivity problems towards the first, i.e. serving cell to a user equipment or group of user equipments is that handover is particularly challenging in some deployments. Thus, it often happens that one has to resort to connection recovery as initiated by the user equipment in particular regions. Therefore, there is an incentive to speed up this recovery at places where such problems are likely.

[0099] FIG. 6 schematically illustrates method steps performed by a network node according to embodiments of the invention. In step 602, the network node sends a configuration message to one or more user equipments being served in a first cell that is controlled by said network node, the message defining at least one condition. Examples of such condition have been described in the foregoing in relation to the description of the method performed by the user equipment. In step 605, one or more user equipment is configured by the network node to evaluate said at least one condition upon detection of connectivity problems towards the first cell. In step 606, said one or more user equipment is configured by the network node to apply at least one special criterion for initiating connection re-establishment to a neighboring cell if said at least one condition is fulfilled for said neighboring cell, said special criterion being different from at least one criterion that would be applied if said at least one condition had not been fulfilled.

[0100] In an optional step 607, the network node sends an indication of at least one cell for which said at least one special criterion for initiating connection re-establishment apply if said at least one condition is fulfilled. The indication of at least one cell can be in different forms as described in the foregoing in relation to the description of the method performed by the user equipment.

[0101] In an optional step 600, the network node receives information from one or more neighboring network nodes about previous re-establishment requests in order to establish which cells that should be indicated to the one or more user equipment in step 607. Thus, the network uses statistics from e.g. previous handover failures in order to establish which neighbor cells that should be indicated. For example, if there is information in an eNB that handovers from its cell A to cell B often fails, the network may add cell B as an indicated cell towards which user equipments should implement fast connection re-establishment by application of said at least one special criterion. The information of e.g. failed handovers may for example be received from neighboring network nodes over an X2, S1 or O&M interface.

[0102] A network node may thus be arranged to collect information about connectivity problems such as handovers that have failed, in order to provide such information to other eNBs in control of neighboring cells. For example, a network node B in control of cell B finds that user equipments often arrives in this cell after a failed handover from cell A, see FIG. 9. The network node B in control of cell B may receive this information in a RLF-report message, see 3GPP TS 36.331 and the information element may be failedPCellId. The network node B collects this information, and sends it directly, or via some aggregating node, e.g. an O&M node, to the network node A in control of cell A, whereby that network node can add cell B as an indicated cell towards which user equipments shall implement fast recovery.

[0103] In optional step 601, the network node establishes which cells that should be indicated to the user equipment that is sent in step 607. This can be done by utilizing information or statistics of previous connectivity problems, either received from neighboring network nodes as described in the foregoing or available in itself.

[0104] In step 604, which is an optional step relating to a particular embodiment, the network prepares neighboring cells that has been indicated to the one or more user equipments in step 607 by sending a message to at least one second network node that is in control of such indicated cell, e.g. a radio base station or eNodeB in LTE terminology, such that the second network node is prepared to receive connection re-establishment requests from particular user equipments currently connected to the first cell. The preparation may include sending a handover request from the first network node to the second network node. If both cells are controlled by the same network node, no message needs to be sent, but the network node may itself be prepared for a connection re-establishment from UE1 in an indicated cell.

[0105] Alternatively, if no preparation message is sent, a second network node in control of an indicated cell will not receive any information related to any user equipment that might request connection re-establishment in said indicated cell. Therefore, said second network node is not in possession of any user equipment context related to such user equipment. The second network node in control of an indicated cell may then fetch the context of such user equipment from the network node in control of the first cell. Such fetching implies that the second network node, upon detection of a re-establishment request from a user equipment, requests information related to the user equipment from the first network node. The fetching is successful if the second network node receives necessary information related to the user equipment to accept the re-establishment request. When the fetching is successful, the second network node may accept the re-establishment from the user equipment.

[0106] A user equipment 700, UE, according to embodiments of the invention is schematically illustrated in FIG. 7. The user equipment comprises a receiver 702 and a transmitter 703. Said receiver is configured to receive a configuration message from the network defining at least one condition. Examples of such condition have been described in the foregoing in relation to the description of the method performed by the user equipment. Said message can be received either on a broadcast channel or via dedicated signaling.

[0107] The user equipment 700 furthermore comprises a processor 701 comprising processing circuitry configured to evaluate if said at least one condition is fulfilled upon detection of connectivity problems towards the first cell, and circuitry configured to apply said at least one special criteria for initiating connection re-establishment to said neighboring cell if said at least one condition is fulfilled for a neighboring cell, said at least one special criterion being different from at least one criterion that would be applied if said at least one condition had not been fulfilled.

[0108] In some embodiments, the user equipment 700 furthermore comprises a timer 704 and/or a counter 706. In one specific embodiment, said at least one special criterion include expiration of the timer 704 at a certain expiration value, said expiration value being different from an expiration value of said timer 704 that is applied if said at least one condition had not been fulfilled and/or reaching a threshold value of the counter 706, said threshold being different from a threshold value for the counter 706 that is applied if said at least one condition had not been fulfilled. In one particular embodiment, the timer 704 may be the timer T310, and the counter 706 may be the counter N310.

[0109] In yet further embodiments, the user equipment 700 comprises another, different counter 707 and/or timer 705 for initiating connection re-establishment to a neighboring cell in addition to a counter 706 and/or timer 704 used for initiating re-establishment to a cell if said at least one condition had not been fulfilled.

[0110] An arrangement in a network node 800 is schematically illustrated in FIG. 8. The network node is adapted to be comprised in a network and is furthermore adapted for controlling connection re-establishment between the network and a user equipment, UE, said network serving the user equipment in a first cell comprised in the network.

[0111] The arrangement comprises a receiver 802 and a transmitter 803. The transmitter 803 is configured to send a configuration message to one or more user equipments defining at least one condition. Examples of such condition have been described in relation to the description of the method embodiments performed by the user equipment. Said message can be transmitted either on a broadcast channel or via dedicated signaling.

[0112] The arrangement in the network node 800 furthermore comprises a processor (801) comprising processing circuitry arranged to configure said one or more user equipment to evaluate said at least one condition upon detection of connectivity problems towards the first cell. The processing circuitry is furthermore arranged to configure the one or more user equipment to apply at least one special criterion for initiating connection re-establishment to said neighboring cell if said at least one condition is fulfilled for a neighboring cell, said special criterion being different from at least one criterion that would be applied if said at least one condition had not been fulfilled.

[0113] In some embodiments, the transmitter 803 is configured to send an indication of at least one cell for which said at least one special criterion for initiating connection re-establishment apply if said at least one condition is fulfilled. The indication of at least one cell can be in different forms as described in the foregoing in relation to the description of the method performed by the user equipment.

[0114] In some embodiments, the receiver 802 is configured to receive information from one or more neighboring network nodes about previous re-establishment requests in order to establish which at least one cell that should be indicated to the one or more user equipment.

[0115] In some embodiments, the processor (801) comprises circuitry configured to utilize information of previous connectivity problems to establish which cells that should be indicated to the one or more user equipment. Said processing circuitry may also be configured to use information or statistics received by receiver (802) from neighboring network nodes about re-establishment requests, to establish which cells that should be indicated to the one or more user equipment.

[0116] In some embodiments, the transmitter (803) may be configured to send a preparation message to at least one neighboring network node controlling at least one cell indicated to said one or more user equipments, for preparing such network node to receive a connection re-establishment request from said one or more user equipments.

[0117] The method steps performed by the user equipment (700) and the arrangement in the network node (800) are performed by functional elements of the processing circuitry in their respective processors 701 and 801. In some embodiments these functions are carried out by appropriately programmed microprocessors or microcontrollers, alone or in conjunction with other digital hardware, which may include digital signal processors (DSPs), special-purpose digital logic, and the like. Either or both of the microprocessors and digital hardware may be configured to execute program code stored in memory. Again, because the various details and engineering tradeoffs associated with the design of baseband processing circuitry for mobile devices and wireless base stations are well known and are unnecessary to a full understanding of the invention, additional details are not shown here

[0118] Program code stored in the memory circuit may comprise one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc., and includes program instructions for executing one or more telecommunications and/or data communications protocols, as well as instructions for carrying out one or more of the techniques described herein, in several embodiments. Of course, it will be appreciated that not all of the steps of these techniques are necessarily performed in a single microprocessor or even in a single module.

[0119] The present invention may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the invention. The present embodiments are to be considered in all respects as illustrative and not restrictive.