Patent Description:
The present disclosure is described within the context of Long Term Evolution (LTE), i.e. Evolved Universal Terrestrial Radio Access Network (UMTS) Mobile Telecommunications System (E-UTRAN). It should be understood that the problems and solutions described herein are equally applicable to wireless access networks and user equipments (UEs) implementing other access technologies and standards. LTE is used as an example technology where the embodiments are suitable, and using LTE in the description therefore is particularly useful for understanding the problem and solutions solving the problem.

For ease of understanding, LTE Mobility is described in the following.

Radio Resource Control (RRC) (Third Generation Partnership Project (3GPP) Technical Specification (TS) <NUM>, e.g. V10. <NUM> (<NUM>-<NUM>)) is the main signaling protocol for configuring, re-configuring and general connection handling in the LTE radio access network (E-UTRAN). RRC controls many functions such as connection setup, mobility, measurements, radio link failure and connection recovery. These functions are of relevance for the present disclosure, and are therefore described in some further detail below.

A UE in LTE can be in two RRC states: RRC_CONNECTED and RRC_IDLE. In RRC_CONNECTED state, mobility is network-controlled based on e.g. measurements provided by the UE. the network decides when and to which cell an UE should be handed over, based on e.g. measurements provided by the UE. The network, i.e. the LTE radio base station (called evolved Node Base station (eNodeB or eNB), respectively, in E-UTRAN) configures various measurement events, thresholds etc. based on which the UE then sends reports to the network, such that the network can make a wise decision to hand over the UE to a stronger cell as the UE moves away from the present cell.

<FIG> illustrates a LTE RRC handover procedure according to <NPL>), Fig. <NUM>. <NUM>-<NUM>. <FIG> illustrates a LTE RRC handover procedure. In a mobile network <NUM>, a UE <NUM> is connected to a source eNodeB <NUM> of a LTE radio access network, which is controlled by a Mobility Management Entity (MME) <NUM> of a packet switched domain of a core network. A target eNodeB <NUM> is controlled by the MME <NUM>. The user equipment <NUM> is exchanging data with a serving gateway <NUM> of the core network. During a handover, the user equipment <NUM> is handed over from the source eNodeB <NUM> to the target eNodeB <NUM> of the radio access network. Corresponding user data signaling is indicated by dashed arrows. L3 control signaling is indicated by dotted dashed arrows, and L1/L2 control signaling is indicated by solid arrows. The source eNodeB <NUM> sends in a first step <NUM> management control information to the user equipment <NUM>, which in turn sends corresponding measurement reports in a step <NUM> to the source eNodeB <NUM>. Thereupon, the source eNodeB <NUM> performs in a step <NUM> a handover decision, and sends a handover request in a step <NUM> to the target eNodeB <NUM>. After performing admission control in a step <NUM>, the target eNodeB <NUM> sends a handover request acknowledgement in a step <NUM> to the source eNodeB <NUM>, which initiates a RRC connection reconfiguration in a step <NUM> towards the UE <NUM>.

<FIG> illustrates a simplified picture of the parts of the LTE Handover (HO) procedure relevant for the disclosure. It should be noted that the HO command is in fact prepared in the Target eNB, but the message transmitted via the Source eNB. the UE sees that the message comes from the Source eNB. A mobile network <NUM> comprises a source eNodeB <NUM> and a target eNodeB <NUM>. A UE <NUM> is connected to the source eNodeB <NUM>. Subsequent to a step <NUM>, in which a measurement configuration is sent from the source eNodeB <NUM> to the user equipment <NUM>, the user equipment <NUM> performs in a step <NUM> an A3 event in which a signal strength or signal quality of the target eNodeB <NUM> may be detected to be better compared to a signal strength or signal quality of the source eNodeB <NUM>, respectively, and accordingly reports in a step <NUM> a measurement report to the source eNodeB <NUM>. After a corresponding handover decision in a step <NUM>, the source eNodeB <NUM> sends a handover request in a step <NUM> to the target eNodeB <NUM>, which in turn sends a handover acknowledgement in a step <NUM> to the source eNodeB <NUM>. The source eNodeB <NUM> then sends in a step <NUM> a handover command to the user equipment <NUM>, which performs in a step <NUM> a random access procedure in which dedicated preambles are submitted to the target eNodeB <NUM>. Further arrows <NUM>-<NUM> relate to a completion of the handover procedure. In the step <NUM> an uplink (UL) grant and a Tracking Area (TA) may be sent from the target eNodeB <NUM> to the UE <NUM>. In the step <NUM> a HO confirm may be sent from the UE <NUM> to the target eNodeB <NUM>. In the step <NUM> a Release context may be sent from the target eNodeB <NUM> to the source eNodeB <NUM>. The steps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> correspond to the steps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> in <FIG>.

In RRC_IDLE, mobility is handled by UE-based cell-selection, where a nomadic UE <NUM>, <NUM> selects the "best" cell to camp on, based e.g. on various specified criteria and parameters that are broadcasted in the cells. For example, various cells or frequency layers could be prioritized over other, such that the UE <NUM>, <NUM> tries to camp on a particular cell as long as the measured quality of a beacon or pilot in that cell is a threshold better than some other beacon or pilot received from other cells.

The present disclosure is primarily focusing on problems associated with network-controlled mobility as described above, i.e. for an LTE UE in RRC_CONNECTED state. The problems associated with failing handovers are therefore described in further detail below.

In a regular situation, and when a RRC_CONNECTED UE <NUM>, <NUM> is moving out from the coverage of a first cell (also called source cell), it should be handed over to a neighboring cell (also called target cell or second cell) before loosing the connection to the first cell. it is desirable that the connection is maintained without no or minimal disruption throughout the handover, such that the end-user is unaware of the ongoing handover. In order to succeed with this, it is necessary that.

In addition, and in order for the handover to be successful, the UE <NUM>, <NUM> must finally succeed in establishing a connection to the target cell, which in LTE requires a successful random access request in the target cell, and a subsequent HO complete message. It is noted that specifications may differ somewhat in the naming of messages. This does not limit the applicability of the present disclosure. For example, the handover command labeled as HO Command in the step <NUM> of <FIG> corresponds to the RRC Configuration Reconfiguration of the step <NUM> of <FIG>, and the handover confirm message of the step <NUM> of <FIG> corresponds to the RRC Configuration Reconfiguration Complete of the step <NUM> of <FIG>.

Thus, it is clear that in order to succeed all this, it is necessary that the sequence of events leading to a successful handover is started sufficiently early, so that the radio link to the first cell (over which this signaling takes place) does not deteriorate too much before completion of the signaling. If such deterioration happens before the handover signaling is completed in the source cell (i.e. first cell), then the handover is likely to fail. Such handover failures (HOFs) are clearly not desirable. The current RRC specification therefore provides various triggers, timers, and thresholds in order to adequately configure measurements, such that the need for handovers can be detected reliably, and sufficiently early.

In <FIG>, the exemplified measurement report is triggered by a so called A3 event in the step <NUM> which, in short, corresponds to the scenario in which a neighbor cell is found to be an offset better than the current serving cell. It should be noted that there are multiple events that can trigger a report.

It may occur that a UE102, <NUM> looses coverage to the cell that the UE <NUM>, <NUM> is currently connected to. This could occur in a situation when a UE <NUM>, <NUM> enters a fading dip, or that a handover was needed as described above, but the handover failed for one or another reason. This is particularly true if the "handover region" is very short. By constantly monitoring the radio link quality, e.g. on the physical layer as described in <NPL>), <NPL>), and <NPL>), the UE <NUM>, <NUM> itself is able to declare a radio link failure and autonomously start a RRC re-establishment procedure. If the re-establishment is successful, which depends, among other things, if the selected cell and the eNB <NUM>, <NUM>, <NUM>, <NUM> controlling that cell was prepared to maintain the connection to the UE <NUM>, <NUM>, then the connection between the UE <NUM>, <NUM> and the eNB <NUM>, <NUM>, <NUM>, <NUM> can resume. A failure of a re-establishment means that the UE <NUM>, <NUM> goes to RRC_ IDLE and the connection is released. To continue a communication, a brand new RRC connection has then to be requested and established.

In the following, the features dual connectivity and RRC diversity are described.

Dual connectivity is a feature defined from the UE perspective wherein the UE may simultaneously receive and transmit to at least two different network points. The at least two network points may be connected to one another via a backhaul link such that a UE may be enabled to communicate with one of the network points via the other network point. Dual connectivity is one of the features that are being standardized within the umbrella work of small cell enhancements within 3GPP Release <NUM> (Rel-<NUM>).

Dual connectivity is defined for the case when the aggregated network points operate on the same or separate frequency. Each network point that the UE is aggregating may define a stand-alone cell or it may not define a stand-alone cell. In this respect, the term "stand-alone cell" may particularly denote that each network point, hence each cell, may represent a separate cell from a perspective of a UE. In contrast, network points not defining a stand-alone cell may be regarded from a perspective of a UE as one same cell. It is further foreseen that from the UE perspective the UE may apply some form of Time Division Multiplex (TDM) scheme between the different network points that the UE is aggregating. This implies that the communication on the physical layer to and from the different aggregated network points may not be truly simultaneous.

Dual connectivity as a feature bears many similarities with carrier aggregation and coordinated multi-point (CoMP). The main differentiating factor is that dual connectivity is designed considering a relaxed backhaul and less stringent requirements on synchronization requirements between the network points. This is in contrast to carrier aggregation and CoMP, wherein tight synchronization and a low-delay backhaul are assumed between connected network points.

Examples of features that dual connectivity will allow in the network are:.

<FIG> illustrates the feature of dual connectivity of a UE <NUM> to an anchor 304a and a booster 304b.

A UE <NUM> in dual connectivity maintains simultaneous connections 334a, 334b to anchor and booster nodes 304a, 304b. As the name implies, the anchor node 304a terminates the control plane connection towards the UE <NUM> and is thus the controlling node of the UE <NUM>. The UE <NUM> also reads system information from the anchor 304a. In <FIG>, the system information and a spatial availability thereof are indicated by a dashed circle. In addition to the anchor 304a, the UE <NUM> may be connected to one or several booster nodes 304b for added user plane support. In this respect, the term "booster" may denote that a performance of a UE in terms of its data peak rate may be improved, since user plane data may be additionally transmitted via the booster. To this end, a transmission frequency employed by the anchor may be different from a transmission frequency employed by the booster.

The anchor and booster roles are defined from a UE <NUM> point of view. This means that a node that acts as an anchor 304a to one UE <NUM> may act as booster 304b to another UE <NUM>. Similarly, though the UE <NUM> reads the system information from the anchor node 304a, a node acting as a booster 304b to one UE <NUM>, may or may not distribute system information to another UE <NUM>.

<FIG> illustrates a control and user plane termination in an anchor node and a booster node. This protocol architecture may represent an exemplary protocol termination compliant with dual connectivity and RRC diversity. The protocol architecture shown in <FIG> is proposed as a way forward for realizing dual connectivity in LTE Rel-<NUM> in deployments with relaxed backhaul requirements. In the user plane <NUM> a distributed Packet Data Convergence Protocol (PDCP)/Radio Link Control (RLC) approach is taken where the booster and anchor terminate the user planes <NUM> of their respective bearers, with a possibility to realize user plane aggregation via Multipath Transmission Control Protocol (MPTCP) which may offer a split of traffic to several connections. In the control plane <NUM>, the RRC and Packet Data Convergence Protocol (PDCP) are centralized at the anchor, with a possibility to route RRC messages via the anchor, the booster, or even simultaneously at both links. For ease of completeness, "NAS" may represent a Non Access Stratum protocol layer, "RLC" may represent a Radio Resource Control protocol layer, "MAC" may represent Medium Access Control protocol layer, and "PHYS" may represent a Physical layer.

In a further exemplary protocol termination enabling dual connectivity and RRC diversity, RRC is terminated in the anchor node, and PDCP is available both for the anchor node and the booster node.

However, problems described in the following might occur.

A problem may relate to handover failures and radio link failures for scenarios in which a UE is connected to one network point, hence one cell. In the following, handover and radio link failure robustness is described.

The recent and rapid uptake of Mobile Broadband has led to a need for increasing the capacity of cellular networks. One solution to achieve such a capacity increase is to use denser networks consisting of several "layers" of cells with different "sizes": Macro cells ensure large coverage with cells encompassing large areas, while micro-, pico- and even femto-cells are deployed in hot-spot areas where there is a large demand for capacity. Those cells typically provide connectivity in a much smaller area, but by adding additional cells (and radio base-stations controlling those cells), capacity is increased as the new cells off-load the macro cells.

<FIG> illustrates a UE <NUM> moving out from a pico cell area of a pico cell <NUM> into macro cell area of a macro cell <NUM>. A movement direction of the user equipment <NUM> is indicated by an arrow <NUM>. This figure may illustrate a typical scenario for a handover of a UE <NUM>.

The different "layers" of cells can be deployed on the same carrier (i.e. in a reuse-<NUM> fashion in which all neighboring cells may use the same frequency), the small-cells could be deployed on a different carrier, and the different cells on the various layers could even be deployed using different technologies (e.g. <NUM>/High Speed Packet Access (HSPA) on the macro- and microlayer, and LTE on the pico-layer as one non-exclusive example). In this respect, the term "layer" may particularly denote a higher abstraction level of a cell with respect to a transmission frequency or carrier employed in the cell.

There is currently a large interest for investigating the potential of such Heterogeneous Networks, and operators are interested in such deployments. However, it has also been found that such Heterogeneous Networks may result in an increased rate of handover failures, as briefly discussed above. One reason is that the handover region in Heterogeneous Networks may be very short, meaning that the handover might fail since the UE lost coverage to the source cell before the handover to a target cell could be completed. For example, when a UE leaves a pico-cell, it may happen that the coverage border of the pico is so sharp, that the UE fails to receive any handover command towards a macro before loosing coverage to the pico, see <FIG>.

<FIG> illustrates a handover region of a pico/macro cell change versus a macro/macro cell change. A network comprises a pico cell <NUM>, a marco cell 640a, and a further macro cell 640b. An abscissa <NUM> of the diagram may represent a Reference Signal Received Power (RSRP), and an ordinate <NUM> of the diagram may represent a distance. A curve <NUM> may represent the RSRP perceived by a UE from the macro cell 640a, a curve <NUM> may correspond to the RSRP perceived by a UE from the pico cell <NUM>, and a curve <NUM> may represent the RSRP perceived by the UE from the another macro cell 640b. A handover region <NUM> from the macro cell 640a to the pico cell <NUM> and vice versa is small compared to a handover region <NUM> between the macro cells 640a, 640b.

Similar problems could occur when a UE connected to a macro cell suddenly enters a pico cell on the same carrier: It could now happen that the control channels of the pico cell interferes with the signals that the UE needs to receive from the macro cell in order to complete the handover, and the handover thus fails.

In order to investigate the consequences of increased handover failures and solutions to mitigate those, 3GPP is currently working on evaluations and technical solutions for amendments, as described in TR <NUM>, e.g. V11. <NUM> (<NUM>-<NUM>).

In the following, key performance indication (KPI) degradation and a need for drive testing is described. In this respect, the term "key performance indication" may particularly denote information collected by a network, which information may relate to a performance characteristic of the network such that a corresponding managing network operator may accordingly adapt the network. For example, a KPI may relate to handover failures and may indicate information such as how often a handover may occur, in which area the handover may occur, a reason for the occurrence of the handover etc. The term "drive testing" may particularly denote a procedure in which dedicated testing device, e.g. a user equipment, may move through the network, e.g. may drive around", and may test network characteristics related to e.g. connectivity. In one option, an entity, e.g. a software may be installed spatially fixed in the network and may collect corresponding information from user equipments in the network.

Today it is very difficult to determine if a KPI problem experienced at a certain location in a radio network is due to that a Cell does not receive UE transmission or if it is the UE that does not receive the cell transmission or both. The current typical way of trouble shooting is to make drive testing and collect both Cell traces with time stamped events/transmissions and UE trace with events/transmissions is collected from the UE's used for drive testing. Here, the term "trace" may refer to a collection of logged information.

In 3GPP efforts have been made to support that UE collect some information when experiencing problems with the connection or problems in getting access to the system and then when connectivity is established to the network (NW) at a later time when a connection is established the NW can ask the UE to transmit the collected information. The collected information has time stamp information based on an UE internal clock and also location information.

Drive testing and using specific UE's for drive testing may not always be able to discover intermittent faults or drive into locations where the problem actually occurs. If it is a UE vendor specific problem the UE used for drive testing may not have the same kind of fault as some of the UE's used by subscribers in the network. On top of that regular drive testing is typically very expensive. There is a large cost for collecting the data and also a cost when data is analyzed. The data analysis can be costly and difficult due to that drive testers need to collect all data on rather detailed level and hope that the intermittent fault appears and are captured in the data collected during drive testing amongst the large amount of data collected.

Assuming a system where a UE can be simultaneously connected to several cells, it is currently unclear how the UE shall evaluate radio link failures and how the system shall react upon these radio link failures or other connectivity issues of some of the maintained connections.

Moreover, KPI evaluation by the radio network for UEs experiencing radio link problems in certain locations at a certain time is problematic due to the degraded connectivity to the UE in these situations. With the current system, the evaluation cannot be done immediately after the fault and is usually based on reports or (costly) drive tests. An immediate adaption of the system possibly improving the KPIs is thus not possible.

<CIT> describes a system and a method for implementing call handover (HO). A user equipment (UE) may be configured to communicate with a wireless communication network. The UE is configured to transmit a measurement report to at least one of a serving cell and at least one cell of a coordinated multi-point (CoMP) cell set. The UE is configured to listen for an HO command from a serving cell. The HO command identifies a target cell. The UE is configured to detect a radio link failure between the UE and the serving cell, listen for an HO command from a first cell in the CoMP cell set for a first time duration, and, when an HO command is received from the first cell in the CoMP cell set within the first time duration, perform handover to the target cell identified in the HO command.

It is an object of the present invention to provide measures with which a network adaption of a mobile network in a case a degradation of a quality of a connection of at two connections between an access node of the mobile network and the terminal may be enabled in an improved way. It is a further object of the present invention to provide corresponding methods, a terminal, nodes and a mobile network.

The objects above are solved by methods, a terminal, nodes, a mobile network, according to the independent claims.

The foregoing and other objects, features and advantages will become more apparent in the following detailed description of the present disclosure as illustrated in the accompanying drawings.

According to the exemplary aspects, in a data transmission for a terminal, data may be transmitted from a first access node to the terminal via a first connection and data duplicates may be sent from a second access node to the terminal via a second connection. Here, the term "data transmission" may relate to transmitting signaling data and/or payload data in an uplink direction from the terminal to the mobile network and/or in a downlink direction from the mobile network to the terminal. In order to enable the terminal to receive duplicate data from the first access node and the second access node, the first access node may have duplicated the respective data and may have sent the data duplicates to the second access node via a backhaul connection between the first access node and second access node. The first connection and the second connection may be independent from one another, and may comprise respective radio bearers to be established related to the data transmission.

In such a communication scenario, the first access node may control the data transmission for the terminal and the second access node may assist in the data transmission for the terminal. In this respect, the term "the first access node controlling a data transmission of the terminal" may particularly denote to a control, by the first access node, of resource allocation for uplink and/or downlink data transmission for the terminal and/or a connectivity state of the terminal. Hence, the first access node can be also referred to as an anchor node for the data transmission of the terminal, for example, always being employed for the data transmission for the terminal. Such a communication scenario may be accomplished in LTE by terminating a protocol related to the allocation of resources via the air interface between the terminal and the first access node, particularly a RRC protocol, in the first access node. Alternatively, a PDCP protocol may be terminated in the first access node. In particular, the term "the second access node assisting in the data transmission for the terminal" may particularly denote that the second access node may be free of a capability of controlling the data transmission to the terminal, but may relay the uplink and/or downlink data transmission between the access node and the terminal. In particular, the second access node can be referred to as a booster node for the data transmission of the terminal, for example, being employed for the data transmission for the terminal as relay node. Hence, as explained above, information sent between the first access node and the terminal may be duplicatedly sent between the first access node and the terminal via the second access node.

In this communication scenario, at least one of the first and second connections may comprise a degraded quality. In order to accomplish a suitable mobile network adaption in case of such a quality degradation, a quality of the first connection and/or the second connection may be determined, respective quality degradation information indicating that a quality of the first connection and/or the second connection may be degraded may be acquired based on the step of determining, and, based on the step of acquiring, the mobile network may be adapted. In this respect, the term "acquiring information" may relate to an entity obtaining information by means of internally determining information and/or obtaining information by means of receiving information over the mobile network.

Accordingly, connectivity degradation of a connectivity between the terminal and the first access node and/or the second access node may be handled in an efficient, easy and fast way. An overall system performance may be therefore improved.

With reference to embodiments explained in this disclosure, the first access node may be referred in described embodiments as "Source eNB" and the first connection may refer to an "anchor" connection 332a in <FIG>. The second access node may be referenced in the described embodiments as "Assisting eNB", and the second connection may refer to the "booster" connection 332b in <FIG>. It is noted that the target eNB <NUM>, <NUM> described in connection with <FIG> and <FIG> may also represent an access node adapted to control the data transmission for the terminal depending on being a transmission controlling access node or not.

Next, embodiments related to the method according to first exemplary aspect will be described. These embodiments also apply to the methods according to second, third and fourth exemplary aspects, the terminal according to the fifth exemplary aspect, the first access node according to sixth exemplary aspect, the second access node according to the seventh exemplary aspect, the mobile network according to the eighth exemplary aspect, the computer program according to the ninth exemplary aspect and the computer program product according to the tenth exemplary aspect.

The step of adapting the mobile network may comprise adapting at least one connection between the terminal and the mobile network based on the step of determining. In particular, the terminal may be part of the mobile network.

With respect to the step of adapting, in one variant of the method, the step of determining may result in the first connection comprising a degraded quality, and the step of adapting may comprise maintaining the connection not comprising the degraded quality. In this case, the connection not comprising the degraded quality may be the second connection.

Alternatively or additionally, the step of determining may result in the first connection comprising a degraded quality, and the step of adapting may comprise handing, by the first access node, the terminal over from the first access node to the second access node and disconnecting the first connection. For example, the first access node may initiate the handover of the terminal by sending a handover request to the second access node. The second access node may then forward or relay the handover request to the terminal. The first access node may stop controlling the data transmission of the terminal. In LTE the latter performed step may relate to stop RRC diversity. In this respect, RRC diversity employed in the first access node may relate to a sending of data directly to the terminal and to a sending of duplicates of the data, which may be sent by the first access node to the terminal, to the second access node for relaying them by the second access node to the terminal. The data may comprise control signaling. Accordingly, stopping RRC diversity may refer to not duplicating the sent data anymore, thus maintaining only the direct connection to the terminal to keep legacy functionality. This legacy connection may be handed over to the second access node. Or in other words, particularly with respect to LTE, the latter may relate to stopping RRC signal duplication and forwarding to the second access node. In the above case the first access node may control the disconnection of the terminal, for example by sending a RRC reconfiguration request message to the terminal via the second access node. In the above case, the step of adapting may further comprise transferring, by the first access node, control capabilities for controlling the data transmission of the terminal from the first access node to the second access node. For example, a signaling bearer between the first access node and the terminal may be transferred to the second access node, which bearer may transport a control signaling. In particular, the latter mentioned embodiments may be described later with reference to steps <NUM>, <NUM>, <NUM> and a resulting step or state <NUM> of <FIG>.

In another further variant of the method, the step of determining may result in the second connection comprising a degraded quality, and the step of adapting comprise requesting, by the first access node, to disconnect the second connection, and stopping to employ the second access node for the data transmission for the terminal. In particular, the step of stopping to employ the second access node for the data transmission may comprise stopping to duplicate the data sent from the first access node to the terminal and stopping to send the duplicated data to the second access node. In particular, this step may be embodied as stopping RRC diversity, relating to not duplicating the data or messages anymore which may be to be sent to the second access node. A message related to the disconnect request may be embodied as a Stop RRC relaying message explained with reference to <FIG>. Thus only a direct connection from the first access node to the UE may be maintained, the latter referring to as legacy functionality of the first access node of the mobile network. This embodiment may be described later with reference to <FIG>.

With regard to the step of acquiring, in a first variant of the method, the step of determining may result in one connection of the first connection and the second connection comprising a degraded quality, and the step of acquiring may comprise sending, by the terminal, the quality degradation information to the access node of the first access node and the second access node whose connection to the terminal might not comprise the degraded quality. In this case the quality degradation information may be sent via the connection not comprising the degraded quality. For example, the quality degradation information may be sent to the first access node, if the second connection may have failed, as will be explained with reference to <FIG>. The quality degradation information may be sent to the second access node, if the first connection may have failed, and may be relayed or forwarded by the second access node to the first access node, as may be explained with reference to <FIG>.

In another variant, the step of determining may result in one connection of the first connection and the second connection comprising a degraded quality, and the step of acquiring may comprise sending, by the terminal, the quality degradation information to the access node of the first access node and the second access node whose connection to the terminal may comprise the degraded quality. In this case the quality degradation information may be sent via the connection comprising the degraded quality and/or may be sent via a further connection between the terminal and the access node. This further connection may be different from the first and second connection. This measure may beneficially enable that the terminal may inform the access node whose connection with the terminal has been identified to be degraded in a transmission direction from the access node to the terminal without a necessity of involving the other access node. The access node may than initiate an adaption of the mobile network without unnecessary delay. It may be assumed for this measure that the connection in a transmission direction from the terminal to the access node may comprise a sufficient high quality for successfully transmitting the quality degradation information.

The connection comprising the degraded quality may have failed. In this case the quality degradation information may comprise or may be embodied as a failure notification indication, particularly a RLF warning indication. The failure notification indication may represent an individual indication, particularly included in a conventional message or in a new type message, or may be a specific type of message.

The quality degradation information may comprise or may be embodied as at least one information of the following kind of information. Information according to a first option may comprise or may be embodied as cell identification indication indicative of an identification of an area, particularly a cell, being served by the access node associated with the failed connection, particularly an PCell Identification (ID), a cell global ID, a physical cell ID, or a carrier frequency of the cell. Information according to a second option may comprise or may be embodied as information about measurement results obtained for the area served by the access node associated with the failed connection and obtained for a previous time period. Information according to a third option may comprise or may be embodied as information about a measurement result obtained for an area, particularly a cell, served by the access node associated with the not failed connection and obtained for a previous time period. Information according to fourth option may comprise or may be embodied as information about a measurement result obtained for at least one further area, particularly a further cell, served by a further access node distinct from the first access node and second access node and obtained for a previous time period, particularly an identifier for the measurement. Information according to a fifth option may comprise or may be embodied as a connection indication indicative of the failed connection. Information according to a sixth option may comprise or may be embodied as a timer of the failure of the failed connection. Information according to a seventh option may comprise or may be embodied as a failure reason.

In such a case the failure reason may comprise at least one of the following kind of failure reasons. In a first option, the failure reason may comprise an expiration of a timer with the timer being started after a predetermined number of counter fulfillments of a condition and the timer being stopped after a predetermined number of counter fulfillments of another condition. For example the latter may correspond to an "out of sync" failure in LTE which may refer to a RLF timer expiry. Another failure reason may comprise a maximum of scheduling requests having been sent over the respective connection particularly without receiving a response. For example the latter may correspond in LTE to a maximum number of scheduling requests having been reached. A further failure reason may comprise a maximum of retransmission of data having been sent by the terminal over the respective connection. For example the latter may correspond in LTE to a maximum number of RLC retransmissions having been reached. In case of RLC retransmissions, the UE may retransmit data, if no reply may be received until a maximum number of retransmissions may be reached. A further failure reason may comprise a maximum of unsuccessful random access attempts having been sent by the terminal over the respective connection without receiving a data transmission over the respective connection. For example the latter may correspond in LTE to a Random Access Channel (RACH) failure.

The at least one information mentioned above may be sent together with the failure notification indication in one message or may be sent subsequent to the sent failure notification indication for the step of acquiring.

Respecting the step of determining, in a first variant of the method, the step of determining may be performed by the terminal and may comprise evaluating the quality of the first connection and evaluating the quality of the second connection. In this case the step of evaluating of the quality of the first connection and the step of evaluating the quality of the second connection may be performed independently of one another. Additionally or alternatively, the respective step of evaluating comprises evaluating a synchronization of the terminal with the respective access node with respect to the data transmission over the respective connection. In particular, a degradation of the quality of the respective connection may be determined, if the terminal may be not suitably synchronized for the data transmission over the respective connection. In particular, the determined degradation of the quality of the connection may correspond to a connection failure.

In a further variant of the method, the step of determining may comprise, particularly for each of the first and second connections, using a timer in the terminal and a counter in the terminal. The counter may be associated with a fulfillment of a condition, and a degradation of the quality of the respective connection may be determined, if the timer may expire with the timer being started after a predetermined number of the counter fulfillments of the condition, and the timer being stopped after a predetermined number of counter fulfillments of another condition. In particular, the timer may correspond to the T310 timer and the counter may correspond to the constant N310. In particular, the same or different type of timers and/or counters can be employed for the first and second connections.

In a further variant, the step of determining comprises, particularly for each of the first and second connections, using a timer in the terminal and counters in the terminal, each of the counters being associated with a fulfillment of a condition, wherein a degradation of the quality of the respective connection may be determined, if the timer may expire, the timer being started after a predetermined number of the counter fulfillments of the condition, and the timer being stopped after a predetermined number of another counter fulfillments of another condition. In particular, the timer may correspond to the T310 timer and the counters may correspond to the counters or constants N310, N311. In particular, the same or different type of timers and/or counters can be employed for the first and second connections.

With respect to the above described embodiments, the timer T310 and the counter N310, <NUM> may represent a legacy timer and a legacy counter, respectively. The counter N310 may count condition fulfilments, in order to start the timer T310. Such condition fulfillment may relate to a condition whether a Signal to Interference and Noise Ratio (SINR) perceived by the terminal may be below a threshold. The counter N311 may count condition fulfilments, in order to stop the timer T310. Such condition fulfillment may relate to a condition whether the SINR perceived by the terminal may be above a further threshold. Hence, the timer T310 may be started after the counter N310 may have counted a predetermined number of condition fulfillments of the condition associated with the counter N310, and the timer T310 may stop after a predetermined number of condition fulfillments of the condition associated with the counter N311 have been counted. A degraded quality is detected, if the timer T310 may expire and the predetermined number of condition fulfillments of the condition associated with the counter N311 might have not been counted.

The respective step of evaluating described above may comprise evaluating whether a maximum of scheduling requests may have been sent over the respective connection. Additionally or alternatively, the respective step of evaluating may comprise evaluating whether a maximum of retransmission of data may have been sent by the terminal over the respective connection. Additionally or alternatively, the respective step of evaluating may comprise evaluating whether a maximum of unsuccessful random access attempts may have been sent by the terminal over the respective connection without receiving a data transmission over the respective connection.

The connection comprising the degraded quality might have not failed.

In such a case the step of determining may result in the first connection comprising the degraded quality and the second connection not comprising a degraded quality, and the step of adapting may comprise switching a functionality of the first access node and the second access node with respect to controlling the data transmission for the terminal. Hence, the first access node may turn into a transmission assisting access node and the second access node may turn into a transmission controlling access node.

In this case the quality degradation information may comprise or may be embodied as a channel quality indication, particularly a Chanel Quality Indication report.

The step of acquiring may comprise sending by one access node of the first access node and the second access node to the other access of the first access node and the second access node the quality degradation information. For example, the step of determining may be performed by the second access node which may monitor a parameter associated with the channel quality information and/or may determine a value of the parameter.

With regard to the step of adapting, in another variant of the method, the step of determining may also result in the first connection and the second connection may have failed, and the step of adapting may comprise establishing a further connection between the terminal and a further access node of the mobile network. In accordance with this embodiment, the step of acquiring may be performed by the terminal, and/or the step of establishing may be initiated by the terminal. The further access node may be distinct from the first access node and the second access node or may be one of the first and second access nodes. Hence, the first connection and/or the second connection may be re-established.

Particularly in the later mentioned case in which the step of determining may result in the first connection and the second connection having failed, the step of acquiring may comprise sending, by the terminal, one or more connection failure reports, particularly radio link failure reports, to the further access node of the mobile network. The one or more connection failure reports may comprise information about the first and/or second connection or about all connections of the terminal. The information may relate to the connection failure of the particular connection or connections. For example, one connection failure report may be sent from the terminal in which the information about the first and/or second connection may be included. Alternatively, at least two connection failure reports may be sent by the terminal, in which information about the connection failure of specific connections may be included. The connection failure report may be sent after the terminal having successfully established a connection to the further access node.

With respect to the step of acquiring, in another variant of the method, the method may further comprise determining at least one key performance indication for the mobile network, and the step of adapting may comprise adapting at least one system setting of the mobile network based on the at least one key performance indication. The step of adapting of the system settings may be alternatively or additionally based on quality degradation information obtained, particularly sent in a RLF indication or RLF reports. An objective of this adaption may be the improvement of one of the key performance indicators in the network. In this respect, the system setting may relate to a characteristic of the first and/or second access node or may relate to a characteristic of a further access node of the mobile network. The above described embodiments for adapting the mobile network may describe an immediate or ad hoc adaption of the mobile network, and this embodiment related to the adaption of the system setting may describe an overall adaption of the mobile network on an intermediate or long term time scale.

Particularly in relation to the later mentioned network adaption, the step of determining may be performed by the terminal and the step of acquiring may be performed by the terminal and an access node of the first access node and the second access node. The method may comprise, acquiring, by the access node, further quality degradation information indicating a quality of the connection between the terminal and the access node being degraded. The step of adapting may be performed based on the acquired quality degradation information and the determined further quality degradation information. The further quality degradation information may relate to whether a maximum number of resynchronization attempts performed by the access node may have been reached, whether a maximum number of scheduling requests sent by the access node may have been reached and/or whether a maximum of number of RLC retransmissions may have been reached by the access node. In order to correctly combine the quality degradation information and the further quality degradation information, each of the latter two information may be associated with a corresponding time stamp.

In such an embodiment, the terminal may determines and send a RLF warning or a CQI report to the access node. The access node may also determine internal connection quality and then may decide which network adaption to perform with respect to quality of a downlink and/or uplink direction of the connection being degraded. This adaption may relate to a long term adaption described above.

With respect to the method according to the second exemplary aspect, quality degradation information embodied as a RLF indication may be embodied as or transmitted in a RRC message. Since RRC may be terminated in the first access node, i.e. RRC messages from the terminal to the second access node may always terminate in the first access node. Quality degradation information embodied as a CQI report and being sent to the second access node may not be automatically forwarded to the first access node, but as explained above the second access node may be enabled to perform such a step. The first access node may be therefore enabled to perform the step of adapting based on the acquired quality degradation information.

With respect to the method according to the third exemplary aspect, the second access node may, in one option described later with reference to <FIG>, adapt the mobile network by stopping RRC relaying. In a further option described later with reference to <FIG>, the second access node may acquire a RLF indication, and may adapt the mobile network by upgrading to the first access node, and may optionally forward the RLF indication to the first access node. In a third option described later in connection with the CQI report, the second access node may receive a CQI report and may adapt the mobile network, and may optionally forward the CQI report to first access node.

In the following with reference to <FIG>, further embodiments will be described in more detail within the context of LTE. It is noted that the terms "terminal" and "user equipment" may be used in an interchangeable way throughout this application. One or more embodiments are based on the assumption that the UE can communicate independently via two maintained connections. To provide radio link failure (RLF) diversity as well, the UE shall trigger the standardized RLF procedure only if both links are out-of-sync. In this respect, the term "out-of sync" may particularly denote that an user equipment may have lost synchronization to an access node in that the user equipment may not be able to decode synchronization information in terms of e.g. reference signals properly. If only one of the maintained connections fails, however, a different UE behavior must be enforced. With the embodiments the UE is able to inform the involved eNBs with the help of a new RRC RLF warning message about the RLF of one of the links, and the eNBs are able to quickly react upon this information by stopping the RRC diversity connection and/or handing over the UE completely to one of the involved eNBs. The eNB may also decide to move potential bearers mapped over the failed link to another link.

<FIG> illustrates steps of a method according to an embodiment. A related communication scenario comprises an user equipment UE, a first access node called a serving base station, and a second access node called an assisting base station. According to a first step <NUM>, the user equipment is connected to the serving base station. This base station may request control signaling relaying assistance from an assisting base station for the UE. In a further step <NUM>, the UE is configured to transmit and receive control signaling both via the serving base station and the assisting base station with the assisting base station relaying the control signaling from and to the serving base station, respectively. Further, the UE may monitor the radio links of all maintained connections separately. In a further step <NUM>, if the UE registers or detects a radio link failure for one of the links, the UE may stop transmission on that link and may transmit a radio link failure warning indication via a second maintained link, possibly relayed by the assisting base station, to the serving base station. In a step <NUM> performed according to a first option of the method, if the failed link may be towards the assisting base station, the serving base station may issue the UE to reconfigure to be solely connected to the serving base station, and may issue the assisting base station to stop assistance. Alternatively, in a step <NUM> performed according to a second option of the method, if the failed link is towards the serving base station, the serving base station may stop transmission and may handover the UE to the assisting base station which may become the serving base station for the UE itself.

Moreover, with the information obtained from the RLF-warning of one link and the information of another maintained connection E-UTRAN is quickly able to combine these information, learn about UE RLF failure reasons, their statistics and can apply necessary adaptations.

Embodiments are based on the assumption that the UE can communicate independently via two maintained connections. To provide radio link failure (RLF) diversity as well, the UE shall trigger the standardized RLF procedure only if both links are out-of-sync. If only one of the maintained connections fails, however, a different UE behavior must be enforced as explained in the following.

In the following, procedures according to embodiments are described in more detail.

In <FIG> and <FIG> the signaling involved in the setup of the RRC connection as well as the reaction upon RLF of one of the links is described. In <FIG>, a mobile network <NUM> comprises an user equipment <NUM>, a source eNodeB <NUM>, and an assisting eNodeB <NUM>. In <FIG>, a mobile network <NUM> comprises an user equipment <NUM>, a source eNodeB <NUM>, and an assisting eNodeB <NUM>. Steps in <FIG>, <FIG> are labelled by integer numbers. RRC anchor functionality of the source and target eNodeBs <NUM>, <NUM>, <NUM> is indicated by a bold solid line and is referenced by a reference numeral <NUM>, <NUM>. RRC relay capability of the assisting eNodeB <NUM>, <NUM> is indicated in <FIG>, <FIG> by a bold dashed line and is referenced by a reference numeral <NUM>, <NUM>.

According to <FIG>, <FIG>, in a step <NUM>, a measurement configuration is sent from the source eNodeB <NUM>, <NUM> to the user equipment <NUM>, <NUM>. In a step <NUM>, an early measurement report is sent from the UE <NUM>, <NUM> to the source eNodeB <NUM>, <NUM>. The early measurement report may be issued in response to a A3 event explained with reference to <FIG>. In a subsequent step <NUM>, an RRC assistance request is sent from the source eNodeB <NUM>, <NUM> to the assisting eNodeB <NUM>, <NUM>. In a next step <NUM>, an RRC assistance response including RRC reconfiguration information is sent from the assisting eNodeB <NUM>, <NUM> to the source eNodeB <NUM>, <NUM>. In a next step <NUM>, the RRC-reconfiguration information is sent from the assisting eNodeB <NUM>, <NUM> to the source eNodeB <NUM>, <NUM>. A RRC-reconfiguration is sent from the source eNodeB <NUM>, <NUM> to the UE <NUM>, <NUM> in a step <NUM>. In a step <NUM>, <NUM>, the source eNodeB <NUM>, <NUM> starts RRC diversity. In a step <NUM>, <NUM>, the assisting eNodeB <NUM>, <NUM> starts RRC relaying. In a next step <NUM>, the UE <NUM>, <NUM> sends a synchronization and RACH procedure request towards the assisting eNodeB <NUM>, which accordingly sends a response to the UE <NUM>, <NUM>.

Hence, the UE <NUM>, <NUM> is first configured with a measurement configuration (<NUM>) issuing an early measurement report (<NUM>). This measurement may relate to a source cell, assisting cell or different cells. Upon reception of this measurement report in the source eNB <NUM>, <NUM> it will (if required) request an RRC diversity peering (<NUM>) with the assisting eNB <NUM>, <NUM>, which acknowledges this request (<NUM>) and includes the RRC-reconfiguration for the UE <NUM>, <NUM> to setup RRC diversity transmission and reception, which the source eNB <NUM>, <NUM> will forward to the UE <NUM>, <NUM> (<NUM>). At this point the source eNB <NUM>, <NUM> will go into RRC diversity state where RRC messages are transmitted and received to the UE <NUM>, <NUM> directly and additionally send to/received from the assisting eNB <NUM>, <NUM> for relaying to/from the UE <NUM>, <NUM>. The UE <NUM>, <NUM> will start a RACH procedure towards the assisting eNB <NUM>, <NUM> to become synchronized to it (<NUM>).

In <FIG> the reaction procedure for RLF to the assisting cell is described, while in <FIG> the procedure for RLF to the source cell is described.

In the following, a reaction to the assisting eNB <NUM> out-of-sync is described. As illustrated in <FIG>, a RLF between the UE <NUM> and the assisting eNodeB <NUM> occurs in a step <NUM>. In a step <NUM>, the UE <NUM> stops transmitting to the assisting eNodeB <NUM>. In a step <NUM>, the UE <NUM> sends a RLF warning to the source eNodeB <NUM>, which in turn stops in a step <NUM> RRC relaying to the assisting eNodeB <NUM>. In steps <NUM>, <NUM>, the source eNodeB <NUM> stops RRC diversity and the assisting eNodeB <NUM> stops RRC relaying, respectively. In steps <NUM> and <NUM>, the source eNodeB <NUM> sends a RRC reconfiguration request to the UE <NUM> and the UE <NUM> sends a RRC reconfiguration command to the source eNodeB <NUM>, respectively. The UE <NUM> is connected to the source eNodeB <NUM> in a communication up to the step <NUM>. In a communication between the UE receiving a response to the synchronization and the RACH procedure in the step <NUM>, and the occurrence of the step <NUM>, dual connectivity for the UE <NUM> is performed, wherein the source eNodeB <NUM> may represent the RRC anchor node. From the step <NUM> onwards, the UE <NUM> is connected to the source eNodeB <NUM>, but not to the assisting eNodeB <NUM>. Afterwards, the source eNB <NUM> may send a path switch request to a core network node,.

Hence, after the UE <NUM> has measured a Layer-<NUM> RLF (i.e. timer T310 expired) towards the assisting cell (<FIG>), it will stop the transmission on this link and trigger the transmission of the (<NUM>) RLF warning message, as further described below, towards the source eNB <NUM>. The source eNB <NUM> will send an indication to the assisting eNB <NUM> to stop the RRC relaying functionality (<NUM>) for the UE <NUM>, since it is aware of the UE <NUM> having triggered RLF to the assisting eNB <NUM>. This way the assisting eNB <NUM> is informed about the radio link failure to the UE <NUM> immediately, which would not have been possible with the currently standardized solution, where this state could only be estimated based on timers etc. At this point RRC diversity should be deactivated in both source eNB <NUM> and assisting eNB <NUM>. Only the connection between source eNB <NUM> and UE <NUM> should be maintained, thus the UE <NUM> is configured to stop RRC diversity, but maintain the connection to the UE <NUM>. The source eNB <NUM> uses the RRC reconfiguration procedure (<NUM>, <NUM>) to reconfigure the UE <NUM> to leave RRC diversity mode and be solely connected to the source cell.

Provided the system is capable of dual connectivity for the UE <NUM>, also potential bearers terminated at the assisting eNB <NUM> would be reconfigured to terminate at the source eNB <NUM>. For this, the source eNB <NUM> also sends a path switch command towards the core network so that the packets are routed to the source eNB <NUM>.

Accordingly, <FIG> illustrates a Radio link failure (RLF) warning for the assisting eNB <NUM> out-of-sync.

In the following, a reaction to a source eNB <NUM> out-of-sync is described. In a step <NUM>, a RLF between the UE <NUM> and the source eNodeB <NUM> has occurred. In a step <NUM>, the UE <NUM> stops transmission to the source eNodeB <NUM>. Thereupon in a step <NUM>, a RLF warning is sent from the UE <NUM> to the source eNodeB <NUM> via the assisting eNodeB <NUM>. In a step <NUM>, the source eNodeB <NUM> sends a handover request to the assisting eNodeB <NUM>. In a step <NUM>, the assisting eNodeB <NUM> sends a handover acknowledgement to the source eNodeB <NUM>. In a step <NUM>, the source eNodeB <NUM> sends a RRC reconfiguration request via the assisting eNodeB <NUM> to the user equipment UE <NUM>. In a step <NUM>, the source eNodeB <NUM> stops RRC diversity and the assisting eNodeB <NUM> upgrades to the RRC anchor in a step <NUM> for the UE <NUM>. In a step <NUM>, the source eNodeB <NUM> sends a sequence number status transfer to the assisting eNodeB <NUM>, and the UE <NUM> sends in a step <NUM> a RRC reconfiguration command to the assisting eNodeB <NUM>. In a step <NUM>, the assisting eNodeB <NUM> sends a UE context release message to the source eNodeB <NUM>. In a communication up to the receipt of the synchronization and RACH procedure related message received by the UE <NUM>, the UE <NUM> is connected to the source eNodeB <NUM>. In a time interval between the UE <NUM> receiving the message in the step <NUM> and the message transfer in the step <NUM> taking place, dual connectivity for the UE <NUM> is performed in which the source eNodeB <NUM> is the RRC anchor node. From the step <NUM> onwards, the UE <NUM> is connected to the assistant eNodeB <NUM>.

Hence, in <FIG> RLF on the link to the source eNB <NUM> occurs and is registered within the UE <NUM>. It will stop its transmission on this link and transmit an RLF warning indication towards the assisting eNB <NUM> (<NUM>) which will (since it is in RRC relaying mode) further forward this indication towards the source eNB <NUM>. The source eNB <NUM> will than handover the UE <NUM> completely to the assisting eNB <NUM> since it can be sure the connection source <NUM>-UE 902is lost. Therefore, it will send the handover request indication (<NUM>) to the assisting eNB <NUM>, which is acknowledged (<NUM>) by the assisting eNB <NUM>. The acknowledgment also includes the handover command for the UE <NUM>, which the source eNB <NUM> is supposed to send to the UE <NUM>. The source eNB <NUM> will send the handover command (RRC reconfiguration (<NUM>)) via the RRC relay, i.e. the assisting eNB <NUM>, to the UE <NUM>. Therefore, it is important that the assisting eNB <NUM> still remains in RRC relaying mode, even though it received and acknowledges the complete handover of the UE <NUM> already. After relaying the handover command to the UE <NUM>, the assisting eNB <NUM> can upgrade itself to be the RRC anchor for the UE <NUM>. The source eNB <NUM> can stop RRC diversity. Both nodes <NUM>, <NUM> will now follow the standardized HO procedure, i.e. source eNB <NUM> will send sequence number status transfer (<NUM>) to the assisting eNB <NUM> and forward buffered packets. The UE <NUM> will confirm the RRC reconfiguration to be solely connected to the assisting (now anchor) eNB <NUM> (<NUM>), and eventually the assisting eNB <NUM> will send the UE context release indication to the source eNB <NUM> (<NUM>).

In another embodiment, the assisting eNB <NUM> being in RRC relaying mode for the UE <NUM>, will transmit the handover command to the UE <NUM> (<NUM>) itself in case the source requests a complete handover. In this variant, the handover request acknowledge message does not need to include the handover command for the UE <NUM>, since the source eNB <NUM> is not supposed to transmit it anyway. However, the source eNB <NUM> needs to be informed that the UE <NUM> is handed over to the assisting eNB <NUM> and that SN status transfer and buffered data transfer needs to be initiated.

In another embodiment, the assisting eNB <NUM> could also inspect the RLF warning it forwards and directly send handover acknowledgment to the source eNB <NUM>, as well as handover command to the UE <NUM> itself.

Accordingly, <FIG> illustrates a radio link failure (RLF) warning for the source eNB out-of-sync.

In the following, radio link failure related actions according to embodiments are described.

It is assumed that the current RLF procedure is only triggered if the conditions for RLF on all links are fulfilled simultaneously. Therefore, RRC needs to evaluate physical layer problems of all links separately.

The timers and constants for the UE <NUM>, <NUM> to evaluate physical layer problems shall be configurable on a per link basis, thus multiple instances of the IE rlf-TimersAndConstants (or at least a subset of the corresponding timers/constants, e.g. T310, N310, N311) shall exist and be configurable in the UE <NUM>, <NUM>. In another embodiment, the same values are applied to the each of the links, but evaluation is still done independently.

In the following a RLF-TimersAndConstants information element per maintained connection is illustrated. In this information element, the above mentioned timers and constants may be included. <IMG>
<IMG>.

To detect a physical layer problem in RRC_CONNECTED, the UE <NUM>, <NUM> evaluates separately per connected cell i if N310i consecutive "out-of-sync" indications are received from lower layers while neither in T300 i, T301 i, T304 i, T311 i and then starts timer T310 i. Upon receiving N311 i consecutive "in-sync" indications from lower layers while T310 i is running, the UE shall stop timer T310 i. The separate evaluation on a per link basis shall also apply if further advanced techniques of "out-of-sync"/"in-sync" evaluations are applied,. e.g. additionally evaluating whether a measurement report was sent.

In the following a RLF-warning procedure according to embodiments is described.

Upon T310 expiry of a certain cell, or maximum number of scheduling requests is reached, or RLC maximum number of retransmissions reached indication for this cell, the UE <NUM>, <NUM> shall trigger the new RLF-warning procedure as defined in the following.

The UE <NUM>, <NUM> shall trigger the following modified actions and prepare the RLF-warning indication to be sent directly via a second maintained connection. Additionally the legacy RLF-Report is prepared in a modified way.

The following two pseudo code examples may describe the method embodiments of <FIG>, <FIG> with respect to a RLF procedure according to TS <NUM> V11. <NUM> (<NUM>-<NUM>), section <NUM>. <NUM> "Detection of RLF". For ease of clarity, not changed pseudo code portions may have been omitted. In particular, deviations from this standard can be deduced by means of comparison with the pseudo code examples and are presented in bold for ease of visibility. The first pseudo code example may relate to a method embodiment in which the terminal <NUM>, <NUM> may stop transmitting and receiving via the degraded or failed connection, hence may stop communicating both in an uplink direction and a downlink direction. The second pseudo code example may relate to method embodiment in which the terminal may continue transmitting in an uplink direction via the degraded or failed connection to the respective access node <NUM>, <NUM>, <NUM>, <NUM> but may not receive any information via the degraded or failed connection towards the respective access node <NUM>, <NUM>, <NUM>, <NUM>.

With alternative <NUM> the terminal <NUM>, <NUM> does not stop transmission/reception on the link for which T310 has expired. Expiry of T310 only means that the downlink channel has problem due to poor channel quality but this does not mean that there are any problems in uplink. The uplink transmissions may therefore successfully reach the base station <NUM>, <NUM>, <NUM>, <NUM>. This is expected to be beneficial especially in case the acknowledgements for the terminals uplink transmissions can be transmitted from the network to the terminal <NUM>, <NUM> on an alternative link, for example a link for which RLF has not been detected.

If the terminal <NUM>, <NUM> continues to transmit and receive (attempt to receive) on the link for which T310 has expired then it is possible that if the link later becomes better after RLF has been detected the terminal <NUM>, <NUM> can resume use of that link.

For example, the terminal <NUM>, <NUM> may detect a RLF on a connection to one access node <NUM>, <NUM>, <NUM>, <NUM> of the source access node <NUM>, <NUM> and the assisting access node <NUM>, <NUM>, the terminal <NUM>, <NUM> may send, in a first option, the RLF indication to the respective other access node <NUM>, <NUM>, <NUM>, <NUM> which may forward the RLF indication to the access node <NUM>, <NUM>, <NUM>, <NUM> associated with the detected RLF. The terminal <NUM>, <NUM> may stop transmission and/or reception to the access node <NUM>, <NUM>, <NUM>, <NUM> associated with the detected RLF or may continue transmission and/or reception to the access node <NUM>, <NUM>, <NUM>, <NUM> associated with the detected RLF. In a second option, the terminal <NUM>, <NUM> may send the RLF indication to the access node <NUM>, <NUM>, <NUM>, <NUM> associated with the detected RLF. The terminal <NUM>, <NUM> might not stop transmission and/or reception to this access node <NUM>, <NUM>, <NUM>, <NUM> in this case. The access node <NUM>, <NUM>, <NUM>, <NUM> may in turn forward the RLF warning to the other access node <NUM>, <NUM>, <NUM>, <NUM> not being associated with the detected RLF.

In the following a selection of links to transmit the RLF-warning according to embodiments is described.

The terminal <NUM>, <NUM> may select a set of configured links on which it sends the RLF-warning on. For example, it may send the RLF-warning to all cells or a subset of all configured links such as only on the source link.

If the terminal <NUM>, <NUM> knows that it has one or more alternative links to the node <NUM>, <NUM>, <NUM>, <NUM> offering the link for which T310 has expired, for example if there are two links from a node to a terminal <NUM>, <NUM> and T310 expires only for one of these links then it would be beneficial to transmit the RLF-warning on one or more alternative links.

The terminal <NUM>, <NUM> may even send the RLF-warning on the link for which the T310 has expired. The benefit of sending the RLF-warning on the link for which T310 has expired is that the concerned node <NUM>, <NUM>, <NUM>, <NUM> may need to be informed about the expiration of T310. The expiration of T310 indicates that the downlink quality is poor however the uplink may still have sufficiently good quality allowing the RLF-warning to reach the concerned node <NUM>, <NUM>, <NUM>, <NUM>.

In the following, RLF-warning contents according to embodiments are described.

In the following, modified RLF-reporting according to embodiments is described. This kind of RLF reporting may be regarded to be modified with respect to legacy RLF reporting according to <NPL>) which may be directed to RFL reporting for a single connection between a terminal <NUM>, <NUM> and an access node <NUM>, <NUM>, <NUM>, <NUM>.

In the original RLF reporting, the UE <NUM>, <NUM> stores RLF related information for the (single) link where the failure occurred and sends the report to E-UTRAN upon request. The report is overridden when another RLF occurs. In RRC diversity, the UE <NUM>, <NUM> shall trigger the original RLF procedure as well as the original RLF report only if all links fail. So, this reporting can be modified to convey information about multiple links.

In one embodiment, the single modified RLF report can include information about multiple or all links.

In another embodiment, multiple RLF reports, so one per link can be created and requested independently or collectively by E-UTRA.

In the following, Channel Quality Indicator (CQI) monitoring in network is described. A CQI information or report may represent an alternative embodiment for the quality degradation information with respect to RFL warning indications described above.

As an alternative to using RLF-warnings in the network to trigger RRC-reconfigurations for the UE <NUM>, <NUM> as explained above, CQI reports received for each link in the respective network node <NUM>, <NUM>, <NUM>, <NUM> can be forwarded to another node <NUM>, <NUM>, <NUM>, <NUM>, which is also currently connected to the UE <NUM>, <NUM>. For example, in the case in which the source eNodeB <NUM>, <NUM> may be associated with a connection quality degradation, the CQI received by the source eNodeB <NUM>, <NUM> may be transmitted to the assisting eNodeB <NUM>, <NUM>. In the case in which the assisting eNodeB <NUM>, <NUM> may be associated with a connection quality degradation, the CQI report received by the assisting eNodeB <NUM>, <NUM> may be sent to the source eNodeB <NUM>, <NUM>. In one embodiment the network will monitor the received CQI reports received from the terminal <NUM>, <NUM> regarding the terminal's different connections. If the reported CQI indicates a channel quality for one connection below a certain threshold the network will consider that connection unfit for use by the terminal <NUM>, <NUM>.

In case the network considers the quality of a connection is not good enough and unfit for use by the terminal <NUM>, <NUM> it may take actions such as the following. Note that different behavior may be applied depending on which type of connection is concerned:.

In the following, RLF-warnings for UL/DL trouble shooting in E-UTRAN according to embodiments are described.

Whenever an RLF warning occurs for one link of the connection (triggered e.g. by out-of-sync, maximum number of scheduling requests reached or maximum number of RLC retransmission reached) the receiving eNB <NUM>, <NUM>, <NUM>, <NUM> can utilize the information about failure reason and UE measurements etc. as given in the warning message by combining it with its own information about the working link, e.g. about current events and transmissions done to UE. So, with the RLF warning procedure, E-UTRAN is able to combine UE and eNB information to determine if the problem was related to that eNB <NUM>, <NUM>, <NUM>, <NUM> did not receive the UE <NUM>, <NUM> on the link where problems was indicated or vice versa or both.

Also the eNB <NUM>, <NUM>, <NUM>, <NUM> may experience similar faults as the UE <NUM>, <NUM> e.g. maximum number of resynch attempts reached, maximum number of scheduling requests reached or maximum number of RLC retransmission reached and then eNB <NUM>, <NUM>, <NUM>, <NUM> could ask the UE <NUM>, <NUM> to provide historic data about UE events and transmissions done. This functionality can be established with another request/response message exchange triggered by the eNB <NUM>, <NUM>, <NUM>, <NUM> and transmitted via one of the maintained connections.

With the combined information E-UTRAN is able to quickly react upon these connectivity problems and adapt its system settings to improve the performance for the UE <NUM>, <NUM> and the overall system, e.g. certain key performance indicators.

Further embodiments are as follows:
In an embodiment, instead of triggering the RLF warning transmission depending on the existing T310 timer for this respective link, a new timer per link is used, which is started simultaneously with the T310 timer, but has a different expiry time. This way, RLF warning indication transmission can be triggered independently of the existing RLF evaluation per link, thus the RLF warning can be transmitted e.g. earlier than RLF on that link is triggered. Also, second N310 and N311 constants per link can be used for this evaluation.

In the following advantages of one or more embodiments are described.

With the provided solution unnecessary transmissions between a UE <NUM>, <NUM> and an eNB <NUM>, <NUM>, <NUM>, <NUM> are avoided in RRC diversity mode. In this way interference and battery consumption are decreased. With the discussed procedures the UE <NUM>, <NUM> is able to maintain an RRC connection when experiencing RLF on one link in a diversity transmission mode. A fast fallback (or fast fall-forward) to one of the maintained connections if one of the connections fails is ensured.

Moreover, this solution will allow an operator to understand the root cause for intermittent performance degradations in a radio network and especially understand if it is a network problem or a UE problem or both. The method will also work in rather poor conditions since only one out of several connections to the network need to work.

With this solution the system is able to very quickly adapt to UE connectivity problems and adapt the system to improve the system's performance.

Referring to <FIG>, a terminal <NUM> for adapting a mobile network is described. For example, the terminal <NUM> may correspond to the terminal <NUM> or <NUM>. The terminal <NUM> is connected to a first access node of the mobile network via a first connection and to a second access node via a second connection. The first access node controls a data transmission for the terminal <NUM> and wherein the second access node assists in the data transmission for the terminal <NUM>. The terminal <NUM> may comprise one or more interfaces <NUM> to the first and second access nodes. The one or more interfaces <NUM> may be coupled each to a processor <NUM> of the terminal <NUM>, which processor <NUM> has access to a memory <NUM> of the terminal <NUM>.

The terminal <NUM> comprises a determination unit <NUM> adapted to determining whether a quality of at least one of the first connection and the second connection is degraded, and an acquiring unit <NUM> adapted to acquire quality degradation information about the degradation of the quality of at least one of the first connection and the second connection based on the determination for adapting the mobile network based on the acquired quality degradation information. In a further implementation, the terminal <NUM> may comprise a determination unit <NUM> adapted to determining whether a quality of at least one of the first connection and the second connection may be degraded, and an acquiring unit <NUM> adapted to acquire quality degradation information about the degradation of the quality of at least one of the first connection and the second connection based on the determination particularly for adapting the mobile network.

In the above two described implementations, the determination unit <NUM> may be part of the processor <NUM>. Further, the acquiring unit <NUM> may be part of the one or more interfaces <NUM>. The one or more interfaces <NUM> may further comprise a reception unit <NUM> and a sending unit <NUM> for implementing receiving and sending capabilities of the one or more interfaces <NUM>, respectively. The sending unit <NUM> may implement above described functionalities related to sending the quality degradation information.

The terminal <NUM> is adapted to perform a method according to embodiments described above and comprises respective functionality based units imbedded in respective physical units <NUM>, <NUM>, <NUM> illustrated in <FIG>.

Referring to <FIG>, an access node <NUM> for adapting a mobile network is illustrated. For example, the access node <NUM> may correspond to the first access node <NUM>, <NUM>. A terminal is connected to the access node <NUM> of the mobile network via a connection and to another access node via another second connection. The access node <NUM> controls a data transmission for the terminal and the another access node assists in the data transmission for the terminal. The access node <NUM> may comprise one or more interfaces <NUM> to the terminal and the another access node. The one or more interfaces <NUM> may be coupled each to a processor <NUM> of the access node <NUM>, which processor <NUM> has access to a memory <NUM> of the access node <NUM>.

The access node <NUM> comprises an acquiring unit <NUM> adapted to acquire quality degradation information about a degradation of a quality of at least one of the first connection and the second connection based on a determination whether the quality of at least one of the first connection and the second connection is degraded, and an adapting unit <NUM> adapted to adapt the mobile network based on the acquired quality degradation information. In a further implementation, the access node <NUM> may comprise an acquiring unit <NUM> adapted to acquire quality degradation information about a degradation of a quality of at least one of the first connection and the second connection. For example, the quality degradation information may be based on a determination whether the quality of at least one of the first connection and the second connection may be degraded. In this further implementation, the access node <NUM> may comprise an adapting unit <NUM> adapted to adapt the mobile network based on the acquired quality degradation information. In both implementations, the access node <NUM> may further comprise a determination unit adapted to determine whether the quality of at least one of the connection and the another connection may be degraded.

In the above two implementations, the acquiring unit <NUM> and the adapting unit <NUM> may be part of the one or more interfaces <NUM>. The one or more interfaces <NUM> may further comprise a reception unit <NUM> and a sending unit <NUM> for implementing receiving and sending capabilities of the one or more interfaces <NUM>, respectively. The determination unit may be part of the processor <NUM>.

The access node <NUM> is adapted to perform a method according to embodiments described above and comprises respective functionality based units imbedded in respective physical units <NUM>, <NUM>, <NUM> illustrated in <FIG>.

Referring to <FIG>, an access node <NUM> for adapting a mobile network is illustrated. For example, the access node <NUM> may correspond to the access node <NUM>, <NUM>. A terminal is connected to the access node <NUM> of the mobile network via a connection and to another access node via another connection. The another access node controls a data transmission for the terminal and the access node <NUM> assists in the data transmission for the terminal. The access node <NUM> may comprise one or more interfaces <NUM> to the terminal and the another access node. The one or more interfaces <NUM> may be coupled each to a processor <NUM> of the access node <NUM>, which processor <NUM> has access to a memory <NUM> of the access node <NUM>.

The access node <NUM> comprises an adapting unit <NUM> adapted to adapt the mobile network based on acquired quality degradation information about a degradation of a quality of at least one of the connection and the another connection, the acquiring of the quality degradation information being based on a determination whether a quality of at least one of the connection and the another connection is degraded. In a further implementation, the access node <NUM> may comprise an adapting unit <NUM> adapted to adapt the mobile network based on a quality of at least one of the connection and the another connection being degraded. In this implementation, the adapting unit <NUM> unit may be adapted to perform the adaption based on acquired quality degradation information about a degradation of a quality of at least one of the connection and the another connection. The acquiring of the quality degradation information may be based on a determination whether a quality of at least one of the connection and the another connection is degraded.

In both latter implementations, the access node <NUM> may comprise an acquiring unit <NUM> adapted to acquire the quality degradation information. In both latter described implementations, the access node <NUM> may also comprise a determination unit <NUM> adapted to determine whether the quality of at least one of the connection and the another connection may be degraded.

The adapting unit <NUM> may be part of the one or more interfaces <NUM>, and the acquiring unit <NUM> may be also part of the one or more interfaces <NUM>. The one or more interfaces <NUM> may further comprise a reception unit <NUM> and a sending unit <NUM> for implementing receiving and sending capabilities of the one or more interfaces <NUM>, respectively. The determination unit <NUM> may be part of the processor <NUM>.

It is noted that the described functionality based units <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM> for implementing the above described functionalities of the respective entity <NUM>, <NUM>, <NUM> may be also realized in software and/or in hardware and software. To this end, suitable configured computer program code may be stored for implementing the above-described functionalities of the respective entity <NUM>, <NUM><NUM> in the memory <NUM>, <NUM>, <NUM> of the respective above described entity <NUM>, <NUM>, <NUM>. The memory <NUM>, <NUM>, <NUM> and the computer program code may form a computer program product. The computer program code may be also stored on a different memory loadable into the memory <NUM>, <NUM>, <NUM> of the respective entity <NUM>, <NUM>, <NUM>. The computer program code may be also provided in a downloadable form, forming a further computer program product.

It is noted that an association between the physical units <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM> of the terminal <NUM> and access nodes <NUM>, <NUM> illustrated in <FIG>, respectively, and the functionality based units <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM> of the terminal <NUM> and access nodes <NUM>, <NUM> illustrated these Figures, respectively, may differ from the described embodiments. For example, the acquiring unit <NUM> of the terminal <NUM> illustrated in <FIG> may be part of the interface <NUM>, the processor <NUM>, and the memory <NUM> of the terminal <NUM>.

It is noted that the embodiments are applicable to LTE and radio access networks of GSM and UMTS.

Claim 1:
A method in a first access node (<NUM>, <NUM>) for communicating in a mobile network (<NUM>), wherein the first access node (<NUM>, <NUM>) is connected via a first connection to a user equipment (<NUM>, <NUM>) and controls a data transmission for the user equipment (<NUM>, <NUM>), wherein the data transmission is assisted by a second access node (<NUM>, <NUM>) which is connected to the user equipment (<NUM>, <NUM>) via a second connection, the method comprising:
- receiving (<NUM>), from the user equipment (<NUM>, <NUM>), in a Radio Resource Control message a radio link failure warning indication indicative of a radio link failure of the second connection and a failure reason related to an expiration of a timer with the timer being started after a predetermined number of counter fulfillments of a condition and the timer being stopped after a predetermined number of counter fulfillments of another condition, and
- adapting (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) the mobile network (<NUM>) based on the received failure notification indication.