WO2017137802A1

WO2017137802A1 - Cell aggregation in wireless communication systems

Info

Publication number: WO2017137802A1
Application number: PCT/IB2016/050682
Authority: WO
Inventors: Xixian Chen; Xiaoming LAI; Weigang Li; Dongsheng Yu
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2016-02-09
Filing date: 2016-02-09
Publication date: 2017-08-17

Abstract

Techniques are disclosed to manage the component cell configuration of a mobile terminal in a wireless communication network, the component cell configuration comprising at least one downlink component cell and at least one uplink component cell. The techniques may comprise, at a radio network controller, monitoring at least one network performance metric and determining that the at least one network performance metric is not in compliance with at least one corresponding network performance threshold. The techniques may also comprise modifying the component cell configuration of the mobile terminal, in response to determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold, such as to bring the at least one network performance metric in compliance with the at least one corresponding network performance threshold, and configuring the mobile terminal with the modified component cell configuration.

Description

CELL AGGREGATION TN WTRELESS COMMTINTCATTON SYSTEMS TECHNICAL FIELD

[0001] The present description generally relates to cell aggregation in wireless communication systems, and more particularly relates to the management of cell aggregation in wireless communication systems.

BACKGROUND

[0002] Carrier Aggregation (CA) is a framework that has been defined in 3GPP Long Term Evolution, LTE, standards to improve the throughput available to mobile terminals (also referred to as user equipments (UEs)). In the CA framework, a mobile terminal is able to connect to and receive data from a plurality of cells. The cell through which the mobile terminal obtains non-access stratum (NAS) information, as well as security parameters is referred to as the primary cell or PCell. The PCell is also where the radio resource control (RRC) connection is maintained and the only cell toward which the mobile terminal can transmit information on the uplink control channel, i.e. Physical Uplink Control Channel or PUCCH. All the other cells from which the mobile terminal can receive data are called secondary cells or SCells. While the current CA framework does provide additional downlink throughput, some issues remain.

[0003] For instance, under the current CA framework, all uplink control message are to be transmitted to the PCell. For various reasons however, the PCell may not provide the best uplink channels among all the cells. For instance, the uplink channel of the PCell may experience congestion due to imbalanced loading or may experience channel quality issues.

[0004] Additionally, under the current CA framework, while the SCells may be added and removed as required, the PCell is changed only at handovers. However, when the PCell to which a mobile terminal is attached changes during handover procedures, all the SCells must first be deconfigured before the mobile terminal changes PCell. Only when the mobile terminal has been properly been handed over to the new PCell can the SCells be reconfigured. However, due to the deconfiguration and reconfiguration of the SCells, the entire handover procedure may take longer, which may result in longer traffic interruptions and increased risks of handover failure due, for instance, to radio link failure.

[0005] Hence, it would be desirable to provide techniques that could obviate or mitigate one or more of the above described problems. SUMMARY

[0006] The present description relates to techniques in a cell aggregation framework for managing a component cell configuration of a mobile terminal in a wireless communication network such as to keep one or more network performance metrics in compliance with one or more corresponding network performance thresholds. The component cell (CC) configuration of a mobile terminal comprises the set of aggregated cells from which the mobile terminal is configured to receive data and to which the mobile terminal is configured to transmit data. In accordance with the cell aggregation framework, the component cells of the CC configuration are all treated equally in that the mobile terminal can receive both control and user data on any of the downlink component cells and can transmit both control and user data on any of the uplink component cells. The management of the CC configuration of a mobile terminal generally comprises the addition, removal, and/or exchange of component cells over time such as to keep the one or more network performance metrics in compliance with their one or more corresponding network performance thresholds.

[0007] According to one aspect, some embodiments include a method of operating a radio network controller for managing a component cell (CC) configuration of a mobile terminal, the CC configuration comprising at least one downlink component cell and at least one uplink component cell. The at least one downlink component cell is the cell from which the mobile terminal is configured to receive data, including control and/or user data, while the at least one uplink component cell is the cell to which the mobile terminal is configured to transmit data, including control and/or user data. The at least one uplink component cell may be different from the at least one downlink component cell. The method generally comprises the radio network controller monitoring at least one network performance metric, and determining that the at least one network performance metric is not in compliance with at least one corresponding network performance threshold. The method also comprises, in response to determining that the at least one network performance metric is not in compliance with at least one corresponding network performance threshold, modifying the CC configuration of the mobile terminal such as to bring the at least one network performance metric in compliance with the at least one corresponding network performance threshold, and configuring the mobile terminal with the modified CC configuration.

[0008] In some embodiments, modifying the CC configuration of the mobile terminal may comprise adding at least one new component cell to the CC configuration, removing at least one existing component cell from the CC configuration, or both. In some embodiments, the added component cell may be a new downlink component cell or a new uplink component cell. Similarly, in some embodiments, the removed component cell may be an existing downlink component cell or an existing uplink component cell. In some embodiments, configuring the mobile terminal with the modified CC configuration may comprise transmitting a configuration message to the mobile terminal, the configuration message comprising an identification of the at least one added component cell, of the at least one remove component cell, or both.

[0009] In some embodiments, the at least one network performance metric may comprise a downlink channel quality of each of the downlink component cells of the CC configuration. In some embodiments, the at least one corresponding network performance threshold may comprise a first downlink channel quality threshold and/or a second downlink channel quality threshold. In some embodiments, determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold may comprise determining that the downlink channel quality of the downlink component cell with the highest downlink channel quality is below the first downlink channel quality threshold. In some embodiments, modifying the CC configuration of the mobile terminal may comprise adding a new downlink component cell to the CC configuration, the new downlink component cell having a downlink channel quality higher than the first downlink channel quality threshold. In some embodiments, determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold may comprises determining that the downlink channel quality of the downlink component cell with the lowest downlink channel quality is below the second downlink channel quality threshold. In some embodiments, modifying the CC configuration of the mobile terminal may comprise removing the downlink component cell with the lowest downlink channel quality from the CC configuration.

[0010] In some embodiments, the at least one network performance metric may comprise an uplink channel quality of each of the uplink component cells of the CC configuration. In some embodiments, the at least one corresponding network performance threshold may comprise a first uplink channel quality threshold and/or a second uplink channel quality threshold. In some embodiments, determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold may comprise determining that the uplink channel quality of the uplink component cell with the highest uplink channel quality is below the first uplink channel quality threshold. In some embodiments, modifying the CC configuration of the mobile terminal may comprise adding a new uplink component cell to the CC configuration, the new uplink CC having an uplink channel quality higher than the first uplink channel quality threshold. In some embodiments, determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold may comprise determining that the uplink channel quality of the uplink component cell with the lowest uplink channel quality is below the second uplink channel quality threshold. In some embodiments, modifying the CC configuration of the mobile terminal may comprise removing the uplink component cell with the lowest uplink channel quality from the CC configuration.

[0011] According to another aspect, some embodiments include a method of operating a radio network controller for managing a core network connection associated with a mobile terminal upon detecting a change in a component cell (CC) configuration of the mobile terminal, the CC configuration comprising at least one downlink component cell and at least one uplink component cell. The at least one downlink component cell is the cell from which the mobile terminal is configured to receive data, including control and/or user data, while the at least one uplink component cell is the cell to which the mobile terminal is configured to transmit data, including control and/or user data. The at least one uplink component cell may be different from the at least one downlink component cell. The method generally comprises the radio network controller determining that none of the component cells of the CC configuration of the mobile terminal are under its control, and, upon determining that none of the component cells of the CC configuration are under its control, initiating the transfer of the core network connection associated with the mobile terminal to another radio network controller controlling at least one component cell of the CC configuration.

[0012] In some embodiments, initiating the transfer of the core network connection may comprise transmitting a request message to a core network node to initiate the transfer of the core network connection toward the target radio network controller which controls at least one component cell of the CC configuration of the mobile terminal. In some embodiments, the request message may comprise an identification of the target radio network controller to which the core network connection should be transferred to.

[0013] In some embodiments, the method may further comprise receiving a confirmation that the core network connection associated with the mobile terminal has been properly transferred to the other radio network controller.

[0014] According to another aspect, some embodiments include a radio network controller configured to perform one or more radio network controller functionalities as described herein.

[0015] In some embodiments, the radio network controller may comprise one or more communication interfaces configured to communicate with one or more communication networks (e.g. radio access networks, core networks, etc.) and/or with one or more radio nodes (e.g. access points, radio base stations, remote radio heads, etc.), and processing circuitry operatively connected to the communication interface(s), the processing circuitry being configured to perform one or more radio network controller functionalities as described herein. In some embodiments, the processing circuitry may comprise one or more processor and one or more memory storing instructions which, upon being executed by the processor, cause the processor to perform one or more network controller functionalities as described herein.

[0016] In some embodiments, the radio network controller may comprise one or more functional modules configured to perform one or more radio network controller functionalities as described herein.

[0017] In the described cell aggregation framework, component cells can be added or removed as needed without relying on any particular cell for control signaling. Both uplink component cells and downlink component cells can be configured, i.e. added to the CC configuration, and deconfigured, i.e. removed from the CC configuration, independently as long as the one or more network performance metrics are in compliance with their corresponding network performance thresholds. [0018] Other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of exemplary embodiments in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS [0019] A more complete understanding of the embodiments described herein, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

[0020] Figure 1 illustrates an exemplary wireless communication network in accordance with some embodiments.

[0021] Figures 2A and 2B illustrate exemplary scenarios in accordance with some embodiments.

[0022] Figure 3 illustrates an exemplary flow chart of some of the operations of a radio network controller in accordance with some embodiments.

[0023] Figures 4 A and 4B illustrate exemplary flow charts of some of the operations of a radio network controller in accordance with some embodiments.

[0024] Figures 5A and 5B illustrate exemplary flow charts of some of the operations of a radio network controller in accordance with some embodiments.

[0025] Figure 6 illustrates an exemplary flow chart of some of the operations of a radio network controller in accordance with some embodiments.

[0026] Figure 7 illustrates another exemplary scenario in accordance with some embodiments.

[0027] Figure 8 illustrates an exemplary flow chart of some of the operations of a radio network controller in accordance with some embodiments.

[0028] Figure 9 illustrates a block diagram of a radio network controller in accordance with some embodiments.

[0029] Figure 10 illustrates another block diagram of a radio network controller in accordance with some embodiments. DETAILED DESCRIPTION

[0030] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the description and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the description.

[0031] In the following description, numerous specific details are set forth. However, it is understood that embodiments may be practiced without these specific details. In other instances, well-known circuits, structures, and techniques have not been shown in detail in order not to obscure the understanding of the description. Those of ordinary skill in the art, with the included description, will be able to implement appropriate functionality without undue experimentation.

[0032] References in the description to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0033] Some embodiments provide methods and systems to manage the component cell (CC) configuration of a mobile terminal in a cell aggregation framework in a wireless communication network such as to maintain one or more network performance metrics in compliance with one or more corresponding network performance thresholds.

[0034] Referring to Fig. 1, an example wireless communication network 10 in which some embodiments can be deployed is illustrated. The communication network 10 comprises a core network 20 which connects a radio access network (RAN) 30 to one or more external networks (e.g. the Internet). As illustrated in Fig. 1, the RAN 30 comprises a plurality of radio network controllers 40 (only two are shown) which are responsible to provide radio access, over a radio interface, to mobile terminals 60 (only one is shown) via one or more cells 50. Each cell 50 generally defines a geographical area being serviced by a radio base station (not shown). One or more of the radio base stations associated with a given radio network controller 40 may be remotely located with respect to the radio network controller 40, while one or more of the radio base stations associated with a given radio network controller 40 may be co-located with that radio network controller 40. The radio network controllers 40 are connected to the core network 20 via core network connections. Some of the radio network controllers 40 may also be connected to each other via radio access network connections. Though not shown, the radio network controllers 40 are also connected to radio base stations under their respective control.

[0035] It is to be noted that network 10 illustrated in Fig. 1 is generic in nature and that additional and/or different network elements and/or network connections could be present. In addition, according to the applicable communication standard used in the network 10, network elements and network connections could be referred to by other names. For instance, in a network 10 in which the applicable communication standard is 3 GPP LTE, the core network 20 would be referred to as the Evolved Packet Core (EPC) while the radio access network 30 would be referred to as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). Furthermore, the radio network controllers 40 would be referred to as evolved Node B (eNBs), the core network connections would be referred to as SI connections and the radio access network connections would be referred to as X2 connections.

[0036] Regardless of the applicable communication standard, the radio network controllers 40 are generally responsible for controlling the operations of the radio base stations under their control. For their part, radio base stations may include access points, base stations, remote radio heads and other radio equipment generally responsible for transmitting and receiving radio signals.

[0037] In Fig. 1, mobile terminal 60 is depicted as being in communication with three of the four cells under the control of radio network controller 40₁. More specifically, mobile terminal 60 is shown as being in communication with Cell 2 and Cell 3 on the downlink, and with Cell 1 and Cell 3 on the uplink. The set of aggregated cells from which mobile terminal 60 is configured to receive data, i.e. downlink component cells, and to which mobile terminal 60 is configured to transmit data, i.e. uplink component cells, defines the component cell (CC) configuration of the mobile terminal 60. The CC configuration identifies the component cells which have been aggregated for use by the mobile terminal 60. Notably, in the CC configuration of a mobile terminal 60, none of component cells, whether downlink component cells or uplink component cells have precedence over one another. In other words, each and every component cell of a CC configuration is considered equal independently of the radio network controller 40 which controls them. The CC configuration of the mobile terminal 60 is however dynamic and may be changed or otherwise modified as needed by the radio network controller 40 such as to maintain one or more network performance metrics in compliance with one or more corresponding network performance thresholds.

[0038] In that sense, Fig. 2 A illustrates scenarios in which the added or removed component cell, either a downlink component cell or an uplink component cell, is managed by the radio network controller 40 which also manages the other component cells with which the mobile terminal is already in communication. In such cases, upon determining that a component cell must be added, or removed, from the CC configuration of the mobile terminal 60, the radio network controller 40 informs the mobile terminal 60 of the modified CC configuration - via a configuration message, e.g. a radio resource control (RRC) configuration message. In some embodiments, this configuration message is transmitted to the mobile terminal 60 via one of the existing downlink component cells of the mobile terminal 60.

[0039] In some embodiments, the added or removed component cell, either a downlink component cell or an uplink component cell, may be managed by another radio network controller 40. In other words, in some embodiments, the component cell which is added, or removed, from the CC configuration of the mobile terminal 60 may be a cell under the control of another radio network controller 40. In such cases, the radio network controller 40 through which the mobile terminal 60 is connected to the core network 20, i.e. the primary radio network controller 40, informs both the mobile terminal 60 and the other radio network controller 40 of the modified CC configuration. Such a scenario is illustrated in Fig. 2B in which the added, or removed, component cell, i.e. Cell 4, is under the control of another radio network controller 40, radio network controller 40₂. In such scenarios, the radio network controller 40 through which the mobile terminal 60 is connected to the core network is responsible for the management of the CC configuration of the mobile terminal 60. [0040] Fig. 3 is a flow chart that illustrates the operations of a radio network controller 40 in accordance with some embodiments. As illustrated, the radio network controller 40 monitors at least one network performance metric (step SI 04). The network performance metric may be associated to, or relate with, the mobile terminal 60, may be associated to, or relate with, the radio network controller 40, or both. Examples of network performance metrics may comprise downlink data buffer, uplink data buffer, channel quality of the downlink component cells, channel quality of the uplink component cells, downlink component cells load, uplink component cells load, etc. Regardless, the radio network controller 40 then determines that the at least one network performance metric is not in compliance with at least one corresponding network performance threshold (step SI 06). For instance, the monitored network performance metric may exceed a network performance threshold or may be below a network performance threshold. Upon determining that the at least one network performance metric being monitored is not in compliance with at least one corresponding network performance threshold, the radio network controller 40 modifies the CC configuration of the mobile terminal 60 such as to bring the non-compliant network performance metric back in compliance with the corresponding network performance threshold (step SI 08). The radio network controller 40 then configures the mobile terminal 60 with the modified CC configuration (step SI 10). Depending on how the CC configuration is modified, the radio network controller 40 may configure the mobile terminal 60 with the modified CC configuration by configuring a new component cell or by deconfiguring an existing component cell via a configuration message. In some embodiments, the configuration message may be an RRC configuration message.

[0041] In some embodiments, if the radio network controller 40 is the radio network controller 40 via which the mobile terminal 60 has initially attached to the network 10, the radio network controller 40 may further establish the initial CC configuration of the mobile terminal 60 (step SI 02) prior to monitoring the at least one network performance metric. This initial CC configuration initially comprises one downlink component cell and one uplink component cell. Notably, the downlink component cell and the uplink component cell may be initially the same cell in that the mobile terminal receives data and transmits data from and to the same radio base station. However, as the radio network controller 40 starts monitoring the one or more network performance metrics, the radio network controller 40 may deconfigured the initially configured downlink component cell or uplink component cell and configured a better downlink component cell or uplink component cell instead.

[0042] In some cases, modifying the CC configuration of the mobile terminal 60 may comprise removing an existing component cell from the CC configuration while in other cases, modifying the CC configuration of the mobile terminal 60 may comprise adding a new component cell to the CC configuration in order to bring the non-compliant network performance metric back in compliance with the corresponding network performance threshold. Figs. 4A and 4B are flow charts that illustrate the operations of a radio network controller 40 in accordance with some embodiments when a component cell needs to be added to or removed from the CC configuration, i.e. when the radio network controller 40 modifies the CC configuration.

[0043] Starting with Fig. 4A, the radio network controller 40 determines that a new component cell needs to be added to the CC configuration of the mobile terminal 60 in order to bring back the non-compliant network performance metric in compliance with the corresponding network performance threshold (step SI 12). The radio network controller 40 then searches for candidate component cells that satisfy a predetermined channel quality threshold (step SI 14). Subsequently, the radio network controller 40 selects one of the candidate component cells that satisfy the predetermined channel quality threshold as the component cell to be added to the CC configuration (step SI 16), and adds the selected candidate component cell to the CC configuration, thereby generating the modified CC configuration (step SI 18). In some embodiments, the radio network controller 40 may select any one of the candidate component cells that satisfy the predetermined channel quality threshold (i.e. random selection) while in other embodiments, the radio network controller 40 may select one of the candidate component cells that satisfy the predetermined channel quality threshold based on one or more additional criteria (e.g. cell with the highest channel quality, cell with the lowest load, etc.).

[0044] Turning now to Fig. 4B, the radio network controller 40 determines that an existing component cell needs to be removed from the CC configuration of the mobile terminal 60 in order to bring back the non-compliant network performance metric in compliance with the corresponding network performance threshold (step S120). The radio network controller 40 then searches for the existing component cell that has the lowest channel quality among all the component cells of the CC configuration (step S122). Subsequently, the radio network controller 40 selects the existing component cell that has the lowest channel quality (step S124) and removes the selected existing component cell from the CC configuration, thereby generating the modified CC configuration (step S126).

[0045] Figs. 5A and 5B are flow charts that illustrate the operations of a radio network controller 40 in accordance with some embodiments. Fig. 5A depicts an embodiment in which a new downlink component cell is added to the CC configuration while Fig. 5B depicts an embodiment in which an existing downlink component cell is removed from the CC configuration.

[0046] In Fig. 5 A, the radio network controller 40 monitors a plurality of network performance metrics, including the downlink (DL) data buffer and the channel quality of each of the downlink component cells of the CC configuration of a given mobile terminal 60 (step S202). The radio network controller 40 then first verifies whether the downlink data buffer exceeds a first downlink data buffer threshold (step S204). If it is the case (YES), the radio network controller 40 determines at least one candidate downlink component cell for possible addition to the CC configuration (step S206). Understandably, if the downlink data buffer is filled beyond the first downlink data buffer threshold, adding a downlink component cell to the CC configuration would increase the throughput toward the mobile terminal 60, thereby allowing the downlink data buffer to fall back to a level below the first downlink data buffer threshold. Once a candidate downlink component cell is found, the radio network controller 40 determines whether the channel quality of the candidate downlink component cell exceeds a first downlink channel quality threshold (step S208). If it is the case (YES), the candidate downlink component cell is added to the CC configuration of the mobile terminal 60 (step S210). Otherwise (NO), the search continues for another candidate downlink component cell. Though not shown, the search for a candidate downlink component cell may stop after a predetermined number of failed attempts.

[0047] If the radio network controller 40 determines that the downlink data buffer does not exceed the first downlink data buffer threshold (NO at step S204), the radio network controller 40 then proceeds to verify whether the channel quality of the downlink component cell with the highest channel quality is below a second downlink channel quality threshold (step S212). If it is the case (YES), the radio network controller 40 determines at least one candidate downlink component cell for possible addition to the CC configuration (step S214). In this case, if the channel quality of the best downlink component cell is below a second downlink channel quality threshold (which may be different from the first downlink channel quality threshold), then it may be beneficial for the mobile terminal 60 to be configured with an additional downlink component cell with a higher downlink channel quality. In that respect, systematically adding new downlink component cells which channel quality is greater than the second downlink channel quality threshold to the CC configuration of a mobile terminal 60 may allow the mobile terminal 60 to avoid conventional cell handover procedures as the mobile terminal 60 would always be configured with at least one downlink component cell of high enough quality. In that sense, the second downlink channel quality threshold may be selected to avoid handover procedures. Once a candidate downlink component cell is found, the radio network controller 40 determines whether the channel quality of the candidate downlink component cell exceeds the second downlink channel quality threshold (step S216). If it is the case (YES), the candidate downlink component cell is added to the CC configuration of the mobile terminal 60 (step S218). Otherwise (NO), the search continues for another candidate downlink component cell. Again, though not shown, the search for a candidate downlink component cell may stop after a predetermined number of failed attempts.

[0048] If the radio network controller 40 determines that the channel quality of the downlink component cell with the highest channel quality is not below the second downlink channel quality threshold (NO at step S212), then the radio network controller 40 proceeds back to continue monitoring network performance metrics (step S202).

[0049] Turning now to Fig. 5B, the radio network controller 40 again monitors a plurality of network performance metrics, including the downlink (DL) data buffer and the channel quality of each of the downlink component cells of the CC configuration of a given mobile terminal 60 (step S202).

[0050] The radio network controller 40 then verifies whether the downlink data buffer is below a second downlink data buffer threshold (step S220). In some embodiments, the second downlink data buffer threshold is lower than the first downlink data buffer threshold. If it is the case (YES), the radio network controller 40 determines the downlink component cell of the CC configuration having the lowest, or worst, channel quality (step 222), and removes the worst downlink component cell from the CC configuration (step S224). Understandably, if the downlink data buffer is not very filled, maintaining too many downlink component cells for the mobile terminal 60 may waste valuable radio resources. In such cases, removing the downlink component cell, or cells, having the lowest channel quality would maintain the number of downlink component cells in the CC configuration to a level reasonable for the amount of downlink traffic.

[0051] If the radio network controller 40 determines that the downlink data buffer is not below the second downlink data buffer threshold (NO at step S220), then the radio network controller 40 determines whether the channel quality of the downlink component cell having the lowest, or worst, channel quality is below a third downlink channel quality threshold (step S226). In some embodiments, the third downlink channel quality threshold may be lower than the second downlink channel quality threshold. If it is the case (YES), the radio network controller 40 removes the worst downlink component cell from the CC configuration (step S228).

[0052] Otherwise, if the radio network controller 40 determines that the channel quality of the downlink component cell with the lowest channel quality is not below the third downlink channel quality threshold (NO at step S226), then the radio network controller 40 proceeds back to continue monitoring network performance metrics (step S202).

[0053] Though not shown for clarity, after the radio network controller 40 configures the mobile terminal 60 with a modified CC configuration, the radio network controller 40 may proceed back to monitoring the network performance metrics.

[0054] While Figs. 5A and 5B depict embodiments in which downlink component cells are added or removed, the same processes would likewise apply for uplink component cells. However, the various thresholds used for addition and removal of uplink component cells may differ from the various thresholds used for the addition and removal of downlink component cells. In that sense, due to the often different characteristics and requirements between the uplink channel and downlink channel, the radio network controller 40 generally manages the uplink component cells and downlink component cells separately (e.g. different metrics, different thresholds, etc.).

[0055] It will be appreciated that by being able to add new component cells and remove existing component cells in order to remain in compliance with certain thresholds, for instance, channel quality thresholds, the handover process may happen in a more seamless manner as higher quality component cells may be systematically added to the CC configuration of a given mobile terminal while lower quality component cells may be systematically removed. [0056] Though in the embodiments illustrated in Figs. 5A and 5B, the radio network controller 40 monitored only two network performance metrics, in other embodiments, the radio network controller 40 could monitor a plurality of network performance metrics, each of which being evaluated in sequence as depicted in Fig. 6.

[0057] As illustrated, the radio network controller 40 monitors a plurality of network performance metrics (e.g. N network performance metrics) (step S302). The radio network controller 40 then determines, or verifies, whether a first one of the network performance metrics is in compliance with its correspondence network performance threshold (step S304i). If the first one of the network performance metrics is not in compliance with its correspondence network performance threshold (NO), the radio network controller 40 proceeds to modify the CC configuration of the mobile terminal 60 such as to bring the first one of the network performance metrics back in compliance with its correspondence network performance threshold (step S306i) before configuring the mobile terminal 60 with the modified CC configuration (step S308i).

[0058] Otherwise, if the radio network controller 40 determines that the first one of the network performance metrics is in compliance with its correspondence network performance threshold (YES at step S304i), then radio network controller 40 proceeds to determine or verify whether a next one of the network performance metrics is in compliance with its corresponding network performance threshold (step S304_n). The same process is repeated, as needed, for each successive network performance metric until the last network performance metric is reached. Though not shown for clarity, after the radio network controller 40 configures the mobile terminal 60 with a modified CC configuration, the radio network controller 40 may proceed back to monitoring the network performance metrics.

[0059] In some embodiments, the sequential determination may be performed in accordance with a predetermined sequence while in other embodiments, the sequential determination may be performed in accordance with a priority of the network performance metrics.

[0060] As indicated above, the radio network controller 40 generally responsible for managing the CC configuration of a mobile terminal 60 is the radio network controller 40 through which the mobile terminal 60 communicates with the core network 20. Hence, in embodiments where the CC configuration of the mobile terminal 60 comprises component cells under the control of different radio network controllers 40, the radio network controller 40 managing the mobile terminal connection to the core network is referred to as the primary radio network controller 40 while the one or more other radio network controllers 40 are referred to as secondary radio network controllers 40. As the CC configuration of a mobile terminal 60 is modified over time, it may occur that a primary radio network controller 40 no longer controls any of the component cells comprised in the CC configuration of the mobile terminal 60. Such an exemplary scenario is depicted in Fig. 7 in which the primary radio network controller 40i, upon determining that one or more network performance metrics are no longer in compliance with their corresponding network performance thresholds, modifies the CC configuration of mobile terminal 60 by removing Cell 4 as a downlink component cell. After removing Cell 4 from the CC configuration of mobile terminal 60 however, primary radio network controller 40₁ no longer controls any of the component cells of the CC configuration of mobile terminal 60. In the illustrated scenario, all the component cells of the CC configuration of mobile terminal 60 are now under the control of secondary radio network controller 40₂.

[0061] Hence, in some embodiments, upon determining or otherwise detecting that none of the component cells of the CC configuration of a mobile terminal 60 are under its control, a primary radio network controller 40 may initiate a transfer, or handover, of the core network connection of the mobile terminal 60 toward a secondary radio network controller 40 which controls at least one component cell of the CC configuration of the mobile terminal 60. In some embodiments, if there are more than one secondary radio network controller 40 which controls at least one component cell of the CC configuration of the mobile terminal 60, the primary radio network controller 40 may initiate the transfer of the core network connection of the mobile terminal 60 toward any one of the secondary radio network controllers 40 that control at least one component cell of the CC configuration of the mobile terminal 60 (i.e. random selection) while in other embodiments, the radio network controller 40 may select one of the secondary radio network controllers 40 that control at least one component cell of the CC configuration of the mobile terminal 60 based on one or more additional criteria (e.g. the secondary radio network controller controlling the most component cells, the secondary radio network controller with the lowest load, etc.). Regardless, upon receiving the core network connection, the former secondary radio network controller 40 effectively becomes the new primary radio network controller 40 for the mobile terminal 60. [0062] With the above in mind, Fig. 8 illustrates the operations of a radio network controller 40 in accordance with some embodiments, wherein the radio network controller 40 determines that none of the component cells of the CC configuration of a mobile terminal 60 are under its control (step S130), and subsequently initiates the transfer, or handover, of the core network connection of the mobile terminal 60 toward a radio network controller 40 which controls at least one component cell of the CC configuration of the mobile terminal 60 (step SI 32). In some embodiments, transferring the core network connection by the primary radio network controller 40 may comprises transmitting a request message (e.g. a core network connection handover request message) to the core network 20, and more specifically to a control node within the core network 20, which may take over the core network connection handover procedure. In some embodiments, once the core network connection handover procedure is complete, the primary radio network controller 40 may receive a message from the core network 20, or from one of its nodes, to release resources associated with the mobile terminal 60. The process illustrated in Fig. 8 may be triggered every time the CC configuration of a mobile terminal 60 is modified.

[0063] In some embodiments, the radio network controller 40 may be operative or otherwise configured to monitor at least one network performance metric, determine that the at least one network performance metric is not in compliance with at least one corresponding network performance threshold, modify the CC configuration of a mobile terminal upon determining that the at least one network performance metric is not in compliance with at least one corresponding network performance threshold, and configure the mobile terminal 60 with the modified CC configuration.

[0064] Referring to Figs. 9 and 10, block diagrams of embodiments of radio network controller 40 that can be used in one or more of the non-limiting described embodiments are illustrated. In Fig. 9, the radio network controller 40 comprises processing circuitry 70, which may comprise one or more processors 72, hardware circuits (e.g. application- specific integrated circuit (ASIC), field-programmable gate array (FPGA), etc.), firmware, or a combination thereof. Processing circuitry 70, in some embodiments, operates in conjunction with memory 74 that stores instructions for execution by one or more processors 72 of the processing circuitry 70. Memory 74 may comprise one or more volatile and/or non-volatile memory devices. Program code for controlling the overall operations of the radio network controller 40 are, in some embodiments, stored in a non- volatile memory, such as a read-only memory or flash memory. Temporary data generated during operations may be stored in random access memory. The program code stored in memory, when executed by the processing circuitry 70, causes the processing circuitry 70 to perform one or more of the methods described above in relation to the radio network controller 40. The radio network controller 40 also comprises communication interface 76 for communicating with the radio base stations, with other radio network controllers 40, and with one or more nodes of a core network 20. The communication interface 76 may comprise one or more transmitter and one or more receiver. Additionally or alternatively, the communications interface 76 may comprise one or more transceiver combining both transmission and reception capabilities. The communication interface 76 may operate according to known communication standards (e.g. 3GPP standards, IEEE standards, IETF standards, etc.).

[0065] In Fig. 10, the radio network controller 40 is illustrated as comprising a plurality of functional modules which may, in some embodiments, be implemented as hardware, software, or combination thereof. Regardless, in Fig. 10, radio network controller 40 comprises a monitoring module 90 configured to monitor at least one network performance metric, and a determining module 92 configured to determine whether the at least one network performance metric is in compliance with at least one corresponding network performance threshold. The radio network controller 40 also comprises a modifying module 94 configured to modify the CC configuration of a mobile terminal 60 upon determining that the at least one network performance metric is not in compliance with at least one corresponding network performance threshold, and a configuring module 96 configured to configure the mobile terminal 60 with the modified CC configuration.

[0066] Those skilled in the art will appreciate that mobile terminal is a non-limiting expression comprising any device equipped with a wireless interface allowing for receiving and transmitting radio signals from and to a radio base station. Some non- limiting examples of a mobile terminal, in a general sense, are a user equipment (UE), a laptop, a wireless device, a machine-to-machine (M2M) device, a device capable of device-to-device (D2D) communication, etc.

[0067] Some embodiments may be represented as a software product stored in a machine-readable medium (also referred to as a computer-readable medium, a processor- readable medium, or a computer usable medium having a computer readable program code embodied therein). The machine-readable medium may be any suitable tangible medium including a magnetic, optical, or electrical storage medium including a diskette, compact disk read only memory (CD-ROM), digital versatile disc read only memory (DVD-ROM) memory device (volatile or non-volatile), or similar storage mechanism. The machine-readable medium may contain various sets of instructions, code sequences, configuration information, or other data, which, when executed, cause a processor to perform steps in a method according to some embodiments. Those of ordinary skill in the art will appreciate that other instructions and operations necessary to implement the described embodiments may also be stored on the machine-readable medium. Software running from the machine-readable medium may interface with circuitry to perform the described tasks.

[0068] The above-described embodiments are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the disclosure.

Claims

What is claimed is:

1) A method of operating a radio network controller for managing a component cell (CC) configuration of a mobile terminal, the CC configuration comprising at least one downlink component cell and at least one uplink component cell, the method comprising:

monitoring at least one network performance metric;

determining that the at least one network performance metric is not in compliance with at least one corresponding network performance threshold;

modifying the CC configuration of the mobile terminal, in response to determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold, such as to bring the at least one network performance metric in compliance with the at least one corresponding network performance threshold;

configuring the mobile terminal with the modified CC configuration.

2) A method as claimed in claim 1, wherein monitoring at least one network performance metric comprises monitoring a plurality of network performance metrics.

3) A method as claimed in claim 1 or 2, wherein modifying the CC configuration of the mobile terminal comprises adding at least one new component cell to the CC configuration.

4) A method as claimed in claim 3, wherein adding at least one new component cell to the CC configuration comprises adding at least one of a new downlink component cell and a new uplink component cell to the CC configuration.

5) A method as claimed in claim 3 or 4, wherein configuring the mobile terminal comprises transmitting a configuration message to the mobile terminal, the configuration message comprising an identification of the at least one added component cell. 6) A method as claimed in claim 1 or 2, wherein modifying the CC configuration of the mobile terminal comprises removing at least one existing component cell from the CC configuration.

7) A method as claimed in claim 6, wherein removing at least one existing component cell from the CC configuration comprises removing at least one of an existing downlink component cell and an existing uplink component cell from the CC configuration.

8) A method as claimed in claim 6 or 7, wherein configuring the mobile terminal comprises transmitting a configuration message to the mobile terminal, the configuration message comprising an identification of the at least one removed component cell.

9) A method as claimed in claim 1 or 2, wherein modifying the CC configuration of the mobile terminal comprises adding at least one new component cell to the CC configuration, and removing at least one existing component cell from the CC configuration.

10) A method as claimed in claim 9, wherein adding at least one new component cell to the CC configuration comprises adding at least one of a new downlink component cell and a new uplink component cell to the CC configuration, and wherein removing at least one existing component cell from the CC configuration comprises removing at least one of an existing downlink component cell and an existing uplink component cell from the CC configuration.

11) A method as claimed in claim 9 or 10, wherein configuring the mobile terminal comprises transmitting a configuration message to the mobile terminal, the configuration message comprising an identification of the at least one added component cell, and an identification of the at least one removed existing component cell.

12) A method as claimed in claim 1, wherein the at least one network performance metric comprises a downlink channel quality of each of the downlink component cells of the CC configuration, and wherein the at least one corresponding network performance threshold comprises a downlink channel quality threshold. 13) A method as claimed in claim 12, wherein determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold comprises determining that the downlink channel quality of the downlink component cell with the highest downlink channel quality is below the downlink channel quality threshold.

14) A method as claimed in claim 13, wherein modifying the CC configuration of the mobile terminal comprises adding a new downlink component cell to the CC configuration, the new downlink component cell having a downlink channel quality higher than the downlink channel quality threshold.

15) A method as claimed in claim 12, wherein determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold comprises determining that the downlink channel quality of the downlink component cell with the lowest downlink channel quality is below the downlink channel quality threshold.

16) A method as claimed in claim 15, wherein modifying the CC configuration of the mobile terminal comprises removing the downlink component cell with the lowest downlink channel quality from the CC configuration.

17) A method as claimed in claim 1, wherein the at least one network performance metric comprises an uplink channel quality of each of the uplink component cells of the CC configuration, and wherein the at least one corresponding network performance threshold comprises an uplink channel quality threshold.

18) A method as claimed in claim 17, wherein determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold comprises determining that the uplink channel quality of the uplink component cell with the highest uplink channel quality is below the uplink channel quality threshold.

19) A method as claimed in claim 18, wherein modifying the CC configuration of the mobile terminal comprises adding a new uplink component cell to the CC configuration, the new uplink component cell having an uplink channel quality higher than the uplink channel quality threshold. 20) A method as claimed in claim 17, wherein determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold comprises determining that the uplink channel quality of the uplink component cell with the lowest uplink channel quality is below the uplink channel quality threshold.

21) A method as claimed in claim 20, wherein modifying the CC configuration of the mobile terminal comprises removing the uplink component cell with the lowest uplink channel quality from the CC configuration.

22) A method as claimed in claim 1 or 2, wherein the at least one network performance metric is based, at least in part, on a channel quality of at least one of the component cells.

23) A method as claimed in claim 1 or 2, wherein the at least one network performance metric is based, at least in part, on an amount of data to be transmitted by the mobile terminal toward the radio network controller.

24) A method as claimed in claim 1 or 2, wherein the at least one network performance metric is based, at least in part, on an amount of data to be transmitted by the radio network controller toward the mobile terminal.

25) A radio network controller configured to manage a component cell (CC) configuration of a mobile terminal, the CC configuration comprising at least one downlink component cell and at least one uplink component cell, the radio network controller comprising:

processing circuitry configured to:

monitor at least one network performance metric; determine that the at least one network performance metric is not in compliance with at least one corresponding network performance threshold;

modify the CC configuration of the mobile terminal, in response to determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold, such as to bring the at least one network performance metric in compliance with the at least one corresponding network performance threshold; and

configure the mobile terminal with the modified CC configuration.

26) A radio network controller as claimed in claim 25, wherein the processing circuitry is further configured to monitor a plurality of network performance metrics.

27) A radio network controller as claimed in claim 25 or 26, wherein when modifying the CC configuration of the mobile terminal, the processing circuitry is further configured to add at least one new component cell to the CC configuration.

28) A radio network controller as claimed in claim 27, wherein when adding at least one new component cell to the CC configuration, the processing circuitry is further configured to add at least one of a new downlink component cell and a new uplink component cell to the CC configuration.

29) A radio network controller as claimed in claim 27 or 28, wherein when configuring the mobile terminal, the processing circuitry is further configured to transmit a configuration message to the mobile terminal, the configuration message comprising an identification of the at least one added component cell.

30) A radio network controller as claimed in claim 25 or 26, wherein when modifying the CC configuration of the mobile terminal, the processing circuitry is further configured to remove at least one existing component cell from the CC configuration.

31) A radio network controller as claimed in claim 30, wherein when removing at least one existing component cell from the CC configuration, the processing circuitry is further configured to remove at least one of an existing downlink component cell and an existing uplink component cell from the CC configuration.

32) A radio network controller as claimed in claim 30 or 31, wherein when configuring the mobile terminal, the processing circuitry is further configured to transmit a configuration message to the mobile terminal, the configuration message comprising an identification of the at least one removed component cell. 33) A radio network controller as claimed in claim 25 or 26, wherein when modifying the CC configuration of the mobile terminal, the processing circuitry is further configured to add at least one new component cell to the CC configuration, and remove at least one existing component cell from the CC configuration.

34) A radio network controller as claimed in claim 33, wherein when adding at least one new component cell to the CC configuration, the processing circuitry is further configured to add at least one of a new downlink component cell and a new uplink component cell to the CC configuration, and wherein when removing at least one existing component cell from the CC configuration, the processing circuitry is further configured to remove at least one of an existing downlink component cell and an existing uplink component cell from the CC configuration.

35) A radio network controller as claimed in claim 33 or 34, wherein when configuring the mobile terminal, the processing circuitry is further configured to transmit a configuration message to the mobile terminal, the configuration message comprising an identification of the at least one added component cell, and an identification of the at least one removed existing component cell.

36) A radio network controller as claimed in claim 25, wherein the at least one network performance metric comprises a downlink channel quality of each of the downlink component cells of the CC configuration, and wherein the at least one corresponding network performance threshold comprises a downlink channel quality threshold.

37) A radio network controller as claimed in claim 36, wherein when determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold, the processing circuitry is further configured to determine that the downlink channel quality of the downlink component cell with the highest downlink channel quality is below the downlink channel quality threshold.

38) A radio network controller as claimed in claim 37, wherein when modifying the CC configuration of the mobile terminal, the processing circuitry is further configured to add a new downlink component cell to the CC configuration, the new downlink component cell having a downlink channel quality higher than the downlink channel quality threshold.

39) A radio network controller as claimed in claim 36, wherein when determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold, the processing circuitry is further configured to determine that the downlink channel quality of the downlink component cell with the lowest downlink channel quality is below the downlink channel quality threshold.

40) A radio network controller as claimed in claim 39, wherein when modifying the CC configuration of the mobile terminal, the processing circuitry is further configured to remove the downlink component cell with the lowest downlink channel quality from the CC configuration.

41) A radio network controller as claimed in claim 25, wherein the at least one network performance metric comprises an uplink channel quality of each of the uplink component cells of the CC configuration, and wherein the at least one corresponding network performance threshold comprises an uplink channel quality threshold.

42) A radio network controller as claimed in claim 41, wherein when determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold, the processing circuitry is further configured to determine that the uplink channel quality of the uplink component cell with the highest uplink channel quality is below the uplink channel quality threshold.

43) A radio network controller as claimed in claim 42, wherein when modifying the CC configuration of the mobile terminal, the processing circuitry is further configured to add a new uplink component cell to the CC configuration, the new uplink component cell having an uplink channel quality higher than the uplink channel quality threshold.

44) A radio network controller as claimed in claim 41, wherein when determining that the at least one network performance metric is not in compliance with the at least one corresponding network performance threshold, the processing circuitry is further configured to determine that the uplink channel quality of the uplink component cell with the lowest uplink channel quality is below the uplink channel quality threshold.

45) A radio network controller as claimed in claim 44, wherein when modifying the CC configuration of the mobile terminal, the processing circuitry is further configured to remove the uplink component cell with the lowest uplink channel quality from the CC configuration.

46) A radio network controller as claimed in claim 25, wherein the at least one network performance metric is based, at least in part, on a channel quality of at least one of the component cells.

47) A radio network controller as claimed in claim 25, wherein the at least one network performance metric is based, at least in part, on an amount of data to be transmitted by the mobile terminal toward the radio network controller.

48) A radio network controller as claimed in claim 25, wherein the at least one network performance metric is based, at least in part, on an amount of data to be transmitted by the radio network controller toward the mobile terminal.

49) A method of operating a radio network controller for managing a core network connection associated with a mobile terminal, the method comprising:

detecting a change in a component cell (CC) configuration of the mobile terminal, the CC configuration comprising at least one downlink component cell and at least one uplink component cell;

determining that none of the component cells of the CC configuration of the mobile terminal are under the control of the radio network controller; and upon determining that none of the component cells of the CC configuration are under the control of the radio network controller, initiating a transfer of the core network connection associated with the mobile terminal to another radio network controller controlling at least one component cell of the CC configuration.

50) A method as claimed in claim 49, wherein initiating a transfer of the core network connection associated with the mobile terminal to another radio network controller comprises transmitting a request message to the core network to initiate the transfer of the core network connection toward another radio network controller.

51) A method as claimed in claim 50, wherein the request message comprises an identification of the another radio network controller.

52) A radio network controller configured to manage a core network connection associated with a mobile terminal, the radio network controller comprising:

processing circuitry configured to:

detect a change in a component cell (CC) configuration of the mobile terminal, the CC configuration comprising at least one downlink component cell and at least one uplink component cell;

determine that none of the component cells of the CC configuration of the mobile terminal are under the control of the radio network controller; and

upon determining that none of the component cells of the CC configuration are under the control of the radio network controller, initiate a transfer of the core network connection associated with the mobile terminal to another radio network controller controlling at least one component cell of the CC configuration.

53) A radio network controller as claimed in claim 52, wherein when initiating a transfer of the core network connection associated with the mobile terminal to another radio network controller, the processing circuit is further configured to transmit a request message to the core network to initiate the transfer of the core network connection toward another radio network controller.

54) A radio network controller as claimed in claim 53, wherein the request message comprises an identification of the another radio network controller.

55) A radio network controller configured to manage a component cell (CC) configuration of a mobile terminal, the CC configuration comprising at least one downlink component cell and at least one uplink component cell, the radio network controller comprising: a monitoring module configured to monitor at least one network performance metric;

a determining module configured to determine whether the at least one network performance metric is in compliance with at least one corresponding network performance threshold;

a modifying module configured to modify the CC configuration of the mobile terminal upon determining that the at least one network performance metric is not in compliance with at least one corresponding network performance threshold; and

a configuring module configured to configure the mobile terminal with the modified CC configuration.