WO2018232724A1

WO2018232724A1 - Controlling dual connectivity

Info

Publication number: WO2018232724A1
Application number: PCT/CN2017/089714
Authority: WO
Inventors: Jing He; Esa Mikael Malkamaki; Benoist Pierre Sebire
Original assignee: Nokia Technologies Oy; Nokia Technologies (Beijing) Co., Ltd.
Priority date: 2017-06-23
Filing date: 2017-06-23
Publication date: 2018-12-27

Abstract

Methods and apparatuses for controlling communications in a system where dual connectivity commands can be received from more than one medium access control entity are disclosed. A communication device operated in a dual connectivity state for a radio bearer receives a dual connectivity state change command from a medium access control (MAC) entity where after the communication device determines, based on a predefined rule, whether to change the dual connectivity state of the communication device based on the received dual connectivity state change command. The communication device is then operated according to the determining.

Description

CONTROLLING DUAL CONNECTIVITY

This disclosure relates to control of dual connectivity in a communication system， and more particularly activation and deactivation of dual connectivity in a communication device operated in a wireless communication system.

A communication system can be seen as a facility that enables communication between two or more devices such as user terminals， machine-like terminals， base stations and/or other nodes by providing carriers between the communication devices. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication may comprise， for example， communication of data for carrying communications such as voice， electronic mail (email) ， text message， multimedia and/or content data and so on. Non-limiting examples of services provided include two-way or multi-way calls， data communication or multimedia services and access to a data network system， such as the Internet.

In a wireless system at least a part of communications between at least two stations occurs over wireless interfaces. Examples of wireless systems include public land mobile networks (PLMN) ， satellite based communication systems and different wireless local networks， for example wireless local area networks (WLAN) . A local area wireless networking technology allowing devices to connect to a data network is known by the tradename WiFi (or Wi-Fi) . WiFi is often used synonymously with WLAN. The wireless systems can be divided into cells， and are therefore often referred to as cellular systems.

A user can access a communication system by means of an appropriate communication device or terminal. A communication device of a user is often referred to as user equipment (UE) . A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications， for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station， for example a base station of a cell， and transmit and/or receive communications on the carrier.

A communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. An example of standardized communication system architectures is the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The LTE is being standardized by the 3rd Generation Partnership Project (3GPP) . The LTE employs the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access. Further development of LTE are sometimes referred to as LTE Advanced (LTE-A) . The current 3GPP standardization effort is directed to what is termed as the 5^th Generation (5G) system.

A study item of this project is known as the New Radio Access Technology (NR) . One goal of NR is to support the very high bit rates required for 5G. As a part of the solution dual connectivity (DC) has been proposed. Dual connectivity is a mode of operation where a communication device in a radio resource control (RRC) connected mode is configured for dual connectivity over two communication paths， or legs， with a Master Cell Group (MCG) and a Secondary Cell Group (SCG) ， respectively. However， there are still unresolved issues in dual connectivity， in particular in view of control of use thereof.

It is noted that the above discussed issues are not limited to any particular communication environment， but may occur in any appropriate communication system.

Embodiments of the invention aim to address one or several of the above issues.

In accordance with an embodiment there is provided a method for controlling communications in a system where dual connectivity commands can be received from more than one medium access control entity， the method comprising receiving， by a communication device operated in a dual connectivity state for a radio bearer， a dual connectivity state change command from a medium access control (MAC) entity， determining by the communication device based on a predefined rule whether to change the dual connectivity state of the communication device based on the received dual connectivity state change command， and operating the communication device according to the determining.

According to another aspect there is provided an apparatus for a communication device， the apparatus comprising at least one processor， and at least one memory including computer program code， wherein the at least one memory and the computer program code are configured， with the at least one processor， to receive a dual connectivity state change command from a medium access control (MAC) entity， determine based on a predefined rule whether to change the dual connectivity state based on the received dual connectivity state change command， and operate the communication device according to the determining.

According to a yet further aspect there is provided an apparatus for a network node， the apparatus comprising at least one processor， and at least one memory including computer program code， wherein the at least one memory and the computer program code are configured， with the at least one processor， to determine a rule to be used by a communication device for handling dual connectivity state change commands by medium access control (MAC) entities， communicate a control message to at least one mobile communication device according to claim 28 for configuring the communication device accordingly.

According to a more specific aspect， the communication device can be configured to activate and/or deactivate dual connectivity for the radio bearer according to the determining based on the rule.

The determining may comprise determining a need of a change of the dual connectivity state based on a received dual connectivity state change command for the bearer in a period. The communication device can be configured to operate according to the received dual connectivity state change command and to ignore at least one further dual connectivity state change command for the bearer in the period.

The dual connectivity can be in deactivated state at the communication device at the time of reception of a dual connectivity state activate command. In response to the command， and based on a relevant rule， the dual connectivity state can be activated for the period. At least one further dual connectivity state activate command can be ignored for the period. According to a possibility the dual connectivity state is deactivated only in response to a dual connectivity state deactivate command from the same medium access control entity from which the dual connectivity state activate command was received. According to another possibility the dual connectivity state activated for the period can be deactivated in response to a dual connectivity state deactivate command from any medium access control entity.

Reception of at least two similar dual connectivity state change commands from different medium access control entities may be required by a rule before change of the dual connectivity state is allowed as requested. Activation of the dual connectivity state may be allowed only after reception of a second dual connectivity activate command from a second medium access control entity. In such case deactivation of dual connectivity state may be nevertheless allowed in response to reception of a dual connectivity deactivate command from one of the medium access control entities. The MAC entity may need to be a predefined entity， for example the one sending the first activate command， the master node， or the secondary node.

A timer may be triggered in response to receiving a dual connectivity state change command. The communication device is configured to wait until the expiry of the timer before acting on the command unless a further dual connectivity state change command is received from a different medium access control entity. The timer may be triggered by a dual connectivity state activate command. The dual connectivity state may be activated before expiry of the timer in response to receiving a further dual connectivity state activate command.

A communication device can be configured to operate based on a rule according to which the device reacts only to a first dual connectivity state change command from a medium access control entity and ignores consequent commands with same content during a period. A timer can be triggered in response to the first dual connectivity state change command. Any dual connectivity state change commands from said medium access control entity can be ignored until expiry of the timer.

Application of predefined rules by the communication device can be controlled based on a control message from an access network. The control message may be communicated based on radio resource control signalling. Configuration of the communication device between different rules may be switched based on the control message.

The dual connectivity can be based on packet data convergence protocol duplication.

The dual connectivity may be provided for the uplink.

A device and/or a communication system comprising an apparatus configured to provide at least one of the embodiments can also be provided. The device may comprise a communication device such as a user equipment or another node capable of wireless communication， or a network node.

A computer program comprising program code means adapted to perform the herein described methods may also be provided. In accordance with further embodiments apparatus and/or computer program product that can be embodied on a computer readable medium for providing at least one of the above methods is provided.

Various other aspects and further embodiments are also described in the following detailed description of examples embodying the invention and in the attached claims.

The invention will now be described in further detail， by way of example only， with reference to the following examples and accompanying drawings， in which：

Figure 1 shows an example of a radio access system；

Figure 2 shows an example of a communication device；

Figures 3 and 4 show schematic examples of control and user planes in a system；

Figures 5 and 6 illustrate two possibilities to arrange dual connectivity；

Figure 7 is a flowchart in accordance with an embodiment； and

Figures 8 to 14 shows exemplifying signalling flows in different scenarios.

In the following certain exemplifying embodiments are explained with reference to a wireless communication system serving devices adapted for wireless communication. Therefore， before explaining in detail the exemplifying embodiments， certain general principles of certain wireless systems， components thereof， and devices for wireless communication and issues underlying the invention are briefly explained with reference to Figures 1 to 6 to assist in understanding the described examples.

A communication device can be used for accessing various services and/or applications provided via a communication system. In wireless communication systems the access is provided via a wireless access interface between wireless communication devices and an appropriate access system. A device may access wirelessly a communication system via a base station. A base station site can provide one or more cells of a cellular system.

A base station node can be connected to a data network via an appropriate gateway. A gateway function between the access system and another network such as a packet data network may be provided by means of any appropriate gateway node， for example a packet data gateway and/or an access gateway. A communication system may thus be provided by one or more interconnect networks and the elements thereof， and one or more gateway nodes may be provided for interconnecting various networks.

A communication device can access a communication system based on various access techniques， for example those based on the third Generation Partnership Project (3GPP) specifications. A non-limiting example of mobile architectures is known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) . A non-limiting example of base station of a cellular system is what is termed as a NodeB or enhanced NodeB (eNB) in the vocabulary of the 3GPP specifications. The eNBs may provide E-UTRAN features such as user plane Radio Link Control/Medium Access Control/Physical Layer Protocol (RLC/MAC/PHY) and control plane Radio Resource Control (RRC) protocol terminations towards mobile communication devices. In 5G a base station is occasionally be referred to as a gNB， or gNodeB. In this specification terms eNB and gNB are used interchangeably， unless the context requires otherwise.

A communication device， referred to herein as user equipment (UE) may be connected to more than one cell at a same time. In the example of Figure 1 the UE 10 is connected to a first cell 13 having a base station 12 (such as an eNB， gNB or NCE or WLAN access point for example) and a second cell 15 having a base station 14 (eNB， gNB or NCE or WLAN access point for example) . The two

cells

13， 15 are， thus， at least partially overlapping.

In one type of example embodiment， the first cell may operate on a licensed band and the second one may operate on an unlicensed band. However， other combinations are also possible. For simplicity， there are just two cells depicted in the scenario shown in Figure 1. In other alternate examples any number of cells operating on licensed and/or unlicensed band (s) may be provided to work together for a suitable Carrier Aggregation (CA) or Dual Connectivity (DC) .

Dual connectivity is a mode of operation of a UE in RRC_CONNECTED mode， configured for dual connectivity with a Master Cell Group (MCG) and a Secondary Cell Group (SCG) . Figure 3 and Figure 4 show the C-plane and U-plane architecture for dual connectivity， respectively.

Further， the base station 12 and/or base station 14 as may comprise a Master eNB or Secondary eNB. For the transport of user plane data from the S-GW (serving Gateway) to the UE so-called ″split bearers″may be used. Split bearers provide two or more paths for downlink user plane data. They can either be sent from the S-GW via the ″Master eNB (MeNB) ″to the UE， or they can be sent from the S-GW via the MeNB to the Secondary eNB (SeNB) which finally sends them to the UE.

The example embodiments can be applied to NR Access Technology. In NR it has been agreed that to increase reliability as well as potentially decrease latency， packet duplication of packets at the Packet Data Convergence Protocol (PDCP) sublayer. NR operations can use high bit rates， such as for 5G operations， and in NRa system bandwidth can be aggregated over more than one carrier.

Figure 2 shows a schematic， partially sectioned view of a communication device 10 that a user can use for communications. Such a communication device is often referred to as a user equipment (UE) or a terminal. An appropriate communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples include a mobile station (MS) such as a mobile phone or what is known as a ’s mart phone’ ， a portable computer provided with a wireless interface card or other wireless interface facility， personal data assistant (PDA) provided with wireless communication capabilities， or any combinations of these or the like. A mobile communication device may provide， for example， communication of data for carrying communications such as voice， electronic mail (email) ， text message， multimedia， positioning data， other data， and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services include two-way or multi-way calls， data communication or multimedia services or simply an access to a data communications network system， such as the Internet.

A mobile device is typically provided with at least one data processing entity 23， at least one memory 24 and other possible components 29 for use in software and hardware aided execution of tasks it is designed to perform， including control of access to and communications via base stations or other access points and/or other user terminals， and dual connectivity. The data processing， storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets， denoted by reference 26. The apparatus 26 can comprise at least one timer function 29. For example， in relation to the herein disclosed rule based duplication activation /deactivation procedures， one or more timers can be provided by timer function 29 for controlling expiry of various possible periods， as explained by the examples below， and so on.

A display 25， a speaker and a microphone are also typically provided. Furthermore， a communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories， for example hands-free equipment， thereto.

The device 10 may receive and transmit signals 28 via appropriate apparatus for receiving and transmitting signals. In Figure 2 transceiver apparatus is designated schematically by block 27. The transceiver may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device. A wireless communication device can be provided with a Multiple Input /Multiple Output (MIMO) antenna system.

As mentioned above， dual connectivity (DC) is a mode of operation in RRC_CONNECTED mode， configured with a Master Cell Group (MCG) and a Secondary Cell Group (SCG) . Figure 3 and Figure 4 show control plane and user plane architectures for dual connectivity. More particularly， Figure 3 shows an example of C-Plane (Control plane) connectivity of eNBs involved in dual connectivity. Figure 4 shows an example of U-Plane (user plane) connectivity of eNBs involved in dual connectivity.

Three types of bearers are available in LTE dual connectivity. For MCG bearers the MeNB is U-plane connected to the S-GW via an interface known as S1-U. The SeNB is not involved in the transport of user plane data. For split bearers the MeNB is U-plane connected to the S-GW via S1-U and in addition， the MeNB and the SeNB are interconnected via X2-U. For SCG bearers the SeNB is directly connected with the S-GW via S1-U. A split bearer known as Secondary Cell Group (SCG) split bearer is also defined in NR-NR dual connectivity (NR DC) and Multi-RAT Dual Connectivity (MR-DC) . Ion this dual connectivity bearer radio protocols are split at the SgNB， and belong to both SCG and MCG.

As a part of the “New Radio” (NR) Access technology subject to 3GPP standardization Packet Data Convergence Protocol (PDCP) duplication has been suggested. According to a proposal for PDCP duplication， when duplication is configured for a radio bearer by RRC， an additional RLC entity and an additional logical channel are added to the radio bearer to handle the duplicated PDCP Protocol Data Units (PDUs) . Duplication at PDCP may therefore consist in sending the same PDCP PDUs twice： once on the original RLC entity and a second time on the additional RLC entity. When doing so， the original PDCP PDU and the corresponding duplicate shall not be transmitted on the same transport block. The two different logical channels can either belong to the same Medium Access Control (MAC) entity (CA of Figure 5) or to different Medium Access Control entities (DC of Figure 6) . In the former case， logical channel mapping restrictions are used to ensure that the original PDCP PDU and the corresponding duplicate are not sent on the same transport block.

It has been agreed that UL PDCP duplication is configurable per data radio bearer (DRB) and， for NR-NR DC case， per signalling radio bearer (SRB) . It is still open whether the initial state of the UL PDCP duplication (duplication active or not active and if not active which leg is used) is a default or whether the initial state can be signalled by RRC. The inventors have recognized that it would be advantageous to define at least one mechanism to start/stop PDCP duplication more quickly and with less signalling overhead compared to RRC reconfiguration.

In the case of carrier aggregation (CA) it has been agreed that duplication on a single carrier will not be supported. RRC configured mapping of two duplicate logical channels (LCHs) to different carriers will be supported (One carrier cannot have both of the duplicate LCHs mapped to it) . Duplicated PDCP PDUs can be submitted to two different RLC entities.

It has also been agreed that MAC control element (CE) approach will be used for control of UL duplication. Optimizations to reliability of the MAC CE will not be introduced for this mechanism. No optimizations or additional interactions between network nodes are introduced for this mechanism. MAC CE approach will also be used for control of uplink PDCP duplication activation and deactivation without interactions between network nodes for MAC CE coordination in network side. This can be problematic in certain occasions.

As shown in Figure 5 illustrating CA case， there is only one MAC entity located in one network node to serve two RLC entities/logical channels (that is， one node handles two legs) . In a DC case shown in Figure 6， two MAC entities are locates in master node (MN) and secondary node (SN) separately to serve two RLC entities/logical channels. Thus there are two legs and two nodes comprising a MAC entity each. In DC case a MAC command， for example a MAC CE for PDCP duplication activation/deactivation can be sent by any one of two MAC entities to a UE based on own channel quality of the respective leg. Thus there can be two MAC entities and two different logical channels for the original PDCP PDU and the corresponding duplicate belong to different MAC entities. The MAC entity in MgNB monitors only its own leg’s radio channel quality and will send MAC CE to UE in case this leg’s quality is not good enough. On the contrary， the MAC entity in SgNB controls the MAC CE for duplication activation and deactivation based on its own leg’s radio channel quality. There is no interaction between the two network nodes to coordinate the MAC CE command sending. A consequence of this is that neither MgNB nor SgNB knows if uplink PDCP duplication has been activated by another node. The UE may receive MAC CE commands independently from two different legs， such as same or different MAC CEs for activation or deactivation. These two commands may arrive at same time or one by one for a period.

Thus， in case of no MAC CE coordination between the two nodes， the UE may receive MAC CEs from two legs. It can be difficult for a UE to correctly perform these commands on uplink PDCP duplication activation/deactivation. For example， if uplink duplication is not activated and UE receives one MAC CE for duplication activation from one of the legs， and if another leg’s quality is considered good enough， the UE may be left in state where it does not know whether it needs to activate the duplication. In another case， if uplink duplication has been activated and a UE receives one MAC CE for duplication deactivation from one of the legs， the UE may enter into a state where it cannot decide whether to deactivate the duplication. In a case where UE receives two MAC CEs from different legs such that one is for activation and another is for deactivation， the UE also has the problem of deciding how to act.

In accordance with certain aspects described herein specific rules for DC duplication activation/deactivation by MAC CE are defined. According to an aspect the rules define how a device such as a UE can handle contradicting MAC CE orders from different legs for duplication. According to an aspect， in a rule based framework the UE can be configured to react only to one command received from one of the related MAC entities and ignore any consequent commands with same content from same MAC entities. The one command can be the first one to arrive or be selected on other basis.

According to an example shown by the flowchart of Figure 7 a method for controlling communications in a system where dual connectivity commands can be received from more than one medium access control entity comprises receiving at 100， by a communication device operated in a dual connectivity state for a radio bearer， a dual connectivity state change command from a medium access control (MAC) entity. The communication device then determines at 102 based on a predefined rule whether to change the dual connectivity state of the communication device based on the received dual connectivity state change command. The communication device is then operated according to the determining at 104.

Activation/deactivation based on predefined rules allows independent gNB operation， i.e.， no interaction is needed between the network nodes. Network configuration allows network to control the rules that the communication device is using， thus， allowing to optimize the duplication for different use cases. This clarifies the behavior of the device for contradicting orders received on MAC CF for duplication.

The following discusses more detailed examples in relation to uplink PDCP duplication for a radio bearer in dual connectivity (DC) cases where there are two MAC entities in two different nodes. In particular， examples of rules to implement duplication activation/deactivation by MAC CE are given.

When receiving a command for duplication activation/deactivation for a radio bearer， the UE stores in a memory thereof an indication of the MAC entity issuing the command and its content (activation or deactivation) in order to apply a predefined rule. The following gives certain examples of activation and deactivation rules.

According to an activation rule 1， when uplink PDCP duplication is not activated for a radio bearer， and if the UE receives one MAC CE for duplication activation from any of the MAC entities for that radio bearer， the UE activates PDCP duplication in uplink for the radio bearer. After having performed duplication activation for a radio bearer， the UE ignores any further MAC CE for duplication activation for that radio bearer received from the other MAC entity.

According to an activation rule 2， when uplink PDCP duplication is not activated for a radio bearer， and when UE receives one MAC CE for duplication activation from one MAC entity， the UE does not activate PDCP duplication for that radio bearer immediately. Only when receives another MAC CE for duplication activation for that radio bearer from the other MAC entity， or when one pre-configured waiting timer expires (started upon reception of the first MAC CE for activation) ， the UE activates PDCP duplication in uplink.

According to deactivation rule 1， when uplink PDCP duplication for a radio bearer is activated， the UE deactivates PDCP duplication in uplink only in response to determining a MAC CE for duplication deactivation for that radio bearer originating from the same MAC entity wherefrom the activation command was received to activate the duplication.

According to deactivation rule 2， when uplink PDCP duplication is activated for a radio bearer， and when the UE receives one MAC CE for duplication deactivation for that radio bearer from any one of two MAC entities， the UE deactivates PDCP duplication in uplink.

Selection between different rules and combination thereof can be configured by network via a RRC message. For example， a USE can be configured to select among combinations activation rule 1 + deactivation rule 1， activation rule 1 + deactivation rule 2， activation rule 2 + deactivation rule 1 or activation rule 2 + deactivation rule 2 by network via RRC message.

In case where activation rule 1 + deactivation rule 1 are configured， when MAC CE for duplication activation for a radio bearer is received simultaneously or during one pre-defined timer running (started upon reception of the first MAC CE for activation) from both MAC entities， and PDCP duplication in uplink for that radio bearer is activated accordingly， any MAC CE for duplication deactivation command for that radio bearer from any MAC entity will deactivate duplication in uplink.

According to one possibility a UE only reacts to one command received from one MAC entity and ignores consequent commands with same content and from the same MAC entity during a pre-configured Timer running.

In accordance with an example some combinations are preferred. For example， configuration may be selectable between combination of activation rule 1 + deactivation rule 1 and activation rule 2 + deactivation rule 2. According to one possibility a RRC configuration can be between these two combinations.

According to an example， when the default uplink duplication state configuration of a UE is duplication deactivation， and in case of two activation commands are received for one period， the UE may have two options how to handle the activation. According to first option duplication activation is triggered by the first MAC CE received from one of the legs. According to a second option duplication activation is triggered when MAC CEs are received from two different legs.

Both options have benefits， regarding the use cases. In the first option， PDCP duplication can be activated as early as possible if one leg’s quality is not good enough. There is a benefit for a radio bearer which has higher reliability requirements. However， too much radio resource may be used. In the second the duplication will be activated only when both legs’ quality is not good enough. This means that even though one leg may not be good enough， the other leg may still have acceptable quality， and the sending of radio bearer in uplink can be guaranteed without activation of DC. Thus， it is not necessary to activate duplication， and radio resources can be saved. A downside may be a risk of too late duplication activation. However， since both options can be used for different use cases， and the duplication can be configured to per radio bearer， both options for MAC CE of duplication activation can be selectively configured to one radio bearer which supports uplink PDCP duplication in DC case. The configuration can be e.g. by RRC.

According to an example received MAC CE commands for deactivation can be handled similarly as activation commands. A MAC entity can send deactivation command when the radio quality has recovered above a predefined level. It can be defined that it has to be only after the same MAC entity has sent an activation command earlier. The deactivation command can be associated with an activation command received from the same leg， and UE can be configured to react only to a deactivation command the associated activation command has been received from the same leg. It is also possible that UE has received activation commands from both legs， and UE may be configured to stop the duplication only after two deactivation commands are received， one from each leg. A benefit of the first option for deactivation is better radio resource utilization as the duplication is stopped as early as possible. The second option can provide high reliability that he first option. Both options can be configured by RRC to one radio bearer.

Figures 8 to 14 show exemplifying and non-limiting signalling flows in various scenarios.

Figure 8 is an example of Activation Rule 1 + Deactivation Rule 1 where MN MAC control activation/deactivation of uplink duplication. In the example MN MAC sends MAC CE for duplication activation and only MN MAC can stop deactivation whereas commands from SN MAC are ignored.

Figure 9 is an example of Activation Rule 1 + Deactivation Rule 1 where SN MAC can activate/deactivate uplink duplication. In the example SN MAC sends MAC CE for duplication activation， and only SN MAC can stop deactivation. Commands from MN MAC are ignored.

Figure 10 is an example of Activation Rule 2 + Deactivation Rule 2 where duplication is activated only when commands received from both MN and SN MAC but can be deactivated by command from MN MAC only. That is， duplication can be activated by receiving commands from both legs. There can be a wait period. Duplication is deactivated by command received from MN MAC.

Figure 11 is an example of Activation Rule 2 + Deactivation Rule 2 where duplication is activated when commands are received from MN and SN MAC and deactivated by a command from SN MAC. Thus duplication can only be activated by commands from both legs， but it is deactivated by command received from SN MAC only.

Figure 12 is an example of Activation Rule 2 + Deactivation Rule 2 where duplication can be activated by one command received from MN MAC’s leg and after a pre-configured waiting timer has expired. Duplication can be is deactivated by a command received from SN MAC as one example.

Figure 13 is an example of Activation Rule 1 + Deactivation Rule 2 where MN MAC activates and SN MAC deactivates uplink duplication. Activation command from SN MAC is ignored. Similarly， deactivation command from MN MAC is ignored.

Figure 14 is an example of activation rule 2 + deactivation rule 1 combination where duplication can only be activated by commands received from both legs. However， activated duplication can be only deactivated by command from MN MAC as leg1 is the leg where the first activation command was communicated. Duplication is thus activated when both commands received and MN MAC deactivates uplink duplication as it is the first leg where activation command was received.

The above examples enable operation without network level coordination between the two nodes at the network side. Rule 1 for activation and deactivation can benefit services requiring high reliability. PDCP duplication can be activated as early as possible if one leg is detected not to offer good enough service. Rule 2 for activation and deactivation can be beneficial from the point of view of uplink capacity and higher resource utilization efficiency. In this case PDCP duplication is activated only after the two legs are detected not to offer good enough service whilst activated PDCP duplication is deactivated as early as possible.

Duplication assumes that the data radio bearer (DRB) is configured as split bearer. For a UL split bearer， a threshold based scheme can be used such that when the amount of data is below a predefined threshold then all data is transmitted via a single (configured) cell group or MAC entity. If a threshold for UL split bearer has been configured and the threshold is larger than zero， then UE can be configured to obey a received deactivation MAC CE only from the MAC entity that has been configured for UL transmission for data amounts below the threshold. This can be so because in this case it is of no help that the other UL leg is very good if the UE is not allowed to send UL data on that UL leg when the data amount is below the threshold. This behavior can be achieved with deactivation rule 1 when the activation MAC CE is always sent from the same MAC entity.

If the threshold is configured to zero， i.e.， all data can be sent through any UL leg， then activation and deactivation rule 2 may be considered to be more appropriate.

Apparatus for controlling communications in a system where dual connectivity commands can be received from more than one medium access control entity may comprise means for receiving， by a communication device operated in a dual connectivity state for a radio bearer， a dual connectivity state change command from a medium access control (MAC) entity， means for determining by the communication device based on a predefined rule whether to change the dual connectivity state of the communication device based on the received dual connectivity state change command， and means for operating the communication device according to the determining.

The described functions may be provided by separate processors or by an integrated processor. The at least one data processor and memory may provide means for implementing the herein described methods. This includes means for activating and/or deactivating dual connectivity for the radio bearer according to the determining based on the rule， means for determining need of a change of the dual connectivity state based on a received dual connectivity state change command for the bearer in a period， means for operating the communication device according to the received dual connectivity state change command， and means for ignoring at least one further dual connectivity state change command for the bearer in the period. The means may be configured to require reception of at least two similar dual connectivity state change commands from different medium access control (MAC) entities before changing the dual connectivity state as requested， and/or allow activation of the dual connectivity state only after reception of a second dual connectivity activate command from a second medium access control (MAC) entity and/or deactivation of dual connectivity state in response to reception of a dual connectivity deactivate command from one of the medium access control entities.

Timer means that can be triggered in response to receiving a dual connectivity state change command can also be provided.

Means for controlling activation /deactivation of the duplication may react only to a first dual connectivity state change command from a medium access control entity and ignore consequent commands with same content during a period. A timer means may triggered in response to the first dual connectivity state change command， and ignoring dual connectivity state change commands from said medium access control entity until expiry of the timer means.

Means for controlling activation/deactivation rules at a communication device based on a control message received from an access network may also be provided. The means may be for switching configuration of the communication device between different rules based on the control message.

The data processors may be of any type suitable to the local technical environment， and may include one or more of general purpose computers， special purpose computers， microprocessors， digital signal processors (DSPs) ， application specific integrated circuits (ASIC) ， gate level circuits and processors based on multi core processor architecture， as non-limiting examples. The data processing may be distributed across several data processing modules. A data processor may be provided by means of， for example， at least one chip. Appropriate memory capacity can be provided in the relevant devices. The memory or memories may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology， such as semiconductor based memory devices， magnetic memory devices and systems， optical memory devices and systems， fixed memory and removable memory.

An appropriately adapted computer program code product or products may be used for implementing the embodiments， when loaded or otherwise provided on an appropriate data processing apparatus， for example for causing determinations， operation of the timers and communications of information. The program code product for providing the operation may be stored on， provided and embodied by means of an appropriate carrier medium. An appropriate computer program can be embodied on a computer readable record medium. A possibility is to download the program code product via a data network. In general， the various embodiments may be implemented in hardware or special purpose circuits， software， logic or any combination thereof. Embodiments of the inventions may thus be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

It is noted that whilst embodiments have been described in relation to certain architectures， similar principles can be applied to other systems. For example， this may be the case in application where no fixed access nodes are provided but a communication system is provided by means of a plurality of user equipment， for example in adhoc networks. Also， the above principles can also be used in networks where relay nodes are employed for relaying transmissions. Therefore， although certain embodiments were described above by way of example with reference to certain exemplifying architectures for wireless networks， technologies and standards， embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein. It is also noted that different combinations of different embodiments are possible. It is also noted herein that while the above describes exemplifying embodiments of the invention， there are several variations and modifications which may be made to the disclosed solution without departing from the spirit and scope of the present invention.

Claims

A method for controlling communications in a system where dual connectivity commands can be received from more than one medium access control entity， the method comprising：

receiving， by a communication device operated in a dual connectivity state for a radio bearer， a dual connectivity state change command from a medium access control (MAC) entity，

determining by the communication device based on a predefined rule whether to change the dual connectivity state of the communication device based on the received dual connectivity state change command， and

operating the communication device according to the determining.
A method as claimed in claim 1， comprising activating or deactivating dual connectivity for the radio bearer according to the determining based on the rule.
A method as claimed in claim 1 or 2， comprising

determining need of a change of the dual connectivity state based on a received dual connectivity state change command for the bearer in a period，

operating the communication device according to the received dual connectivity state change command， and

ignoring at least one further dual connectivity state change command for the bearer in the period.
A method as claimed in claim 3， wherein the dual connectivity is in deactivated state at the communication device at the time of reception of a dual connectivity state activate command， the method comprising

activating the dual connectivity state for the period， and

ignoring at least one further dual connectivity state activate command.
A method as claimed in claim 4， the method comprising deactivating the dual connectivity state only in response to a dual connectivity state deactivate command from the same medium access control entity from which the dual connectivity state activate command was received.
A method as claimed in claim 4， the method comprising deactivating the dual connectivity state in response to a dual connectivity state deactivate command from any medium access control entity.
A method as claimed in any preceding claim， wherein reception of at least two similar dual connectivity state change commands from different medium access control (MAC) entities is required before changing the dual connectivity state as requested.
A method as claimed in claim 7， comprising activation of the dual connectivity state only after reception of a second dual connectivity activate command from a second medium access control (MAC) entity and/or deactivation of dual connectivity state in response to reception of a dual connectivity deactivate command from one of the medium access control entities.
A method as claimed in any preceding claim， comprising triggering a timer in response to receiving a dual connectivity state change command， and waiting until the expiry of the timer before acting on the command unless a further dual connectivity state change command is received from a different medium access control (MAC) entity.
A method as claimed in claim 9， wherein the timer is triggered by a dual connectivity state activate command， the method comprising activating the dual connectivity state before expiry of the timer in response to receiving a further dual connectivity state activate command.
A method as claimed in any preceding claim， comprising reacting only to a first dual connectivity state change command from a medium access control entity and ignoring consequent commands with same content during a period.
A method as claimed in claim 11， comprising triggering a timer in response to the first dual connectivity state change command， and ignoring dual connectivity state change commands from said medium access control entity until expiry of the timer.
A method as claimed in any preceding claim， comprising controlling application of activation/deactivation rules by the communication device based on a control message received from an access network.
A method as claimed in claim 13， wherein the control message is communicated based on radio resource control signalling.
A method as claimed in claim 13 or 14， comprising switching configuration of the communication device between different rules based on the control message.
A method as claimed in any preceding claim， wherein the dual connectivity is based on packet data convergence protocol duplication for the uplink.
An apparatus for a communication device， the apparatus comprising at least one processor， and at least one memory including computer program code， wherein the at least one memory and the computer program code are configured， with the at least one processor， to

receive a dual connectivity state change command from a medium access control (MAC) entity，

determine based on a predefined rule whether to change the dual connectivity state based on the received dual connectivity state change command， and

operate the communication device according to the determining.
An apparatus as claimed in claim 17， configured to

determine need of a change of the dual connectivity state based on a received dual connectivity state change command for the bearer in a period，

cause the communication device to operate according to the received dual connectivity state change command， and

ignore at least one further dual connectivity state change command for the bearer in the period.
An apparatus as claimed in claim 18， configured to， when the dual connectivity is in deactivated state at the time of reception of a dual connectivity state activate command， activate the dual connectivity state for the period， and ignore at least one further dual connectivity state activate command.
An apparatus as claimed in claim 19， configured to deactivate the dual connectivity state only in response to a dual connectivity state deactivate command from the same medium access control entity from which the dual connectivity state activate command was received.
An apparatus as claimed in claim 19， configured to deactivate the dual connectivity state in response to a dual connectivity state deactivate command from any medium access control entity.
An apparatus as claimed in any of claims 17 to 21， wherein the rule requires reception of at least two similar dual connectivity state change commands from different medium access control (MAC) entities before the dual connectivity state can be changed as requested and/or the rule allows deactivation of dual connectivity state in response to reception of a dual connectivity deactivate command from one of the medium access control entities.
An apparatus as claimed in claim 22， configured to activate the dual connectivity state only after reception of a second dual connectivity activate command from a second medium access control (MAC) entity.
An apparatus as claimed in any of claims 17 to 23， comprising a timer configured to trigger in response to receiving a dual connectivity state change command， the apparatus being configured to wait until expiry of the timer before acting on the received command unless a further dual connectivity state change command is received from a different medium access control (MAC) entity.
An apparatus as claimed in claim 24， wherein the timer is configured to be triggered by a dual connectivity state activate command， the apparatus being configured to activate the dual connectivity state before expiry of the timer in response to receiving a further dual connectivity state activate command.
An apparatus as claimed in any of claims 17 to 25， configured to react only to a first dual connectivity state change command from a medium access control entity and ignore consequent commands with same content during a period.
An apparatus as claimed in any of claims 17 to 26， configured to switch between different rules based on a control message from an access system.
A communication device comprising an apparatus in accordance with any of claims 17 to 27.
An apparatus for a network node， the apparatus comprising at least one processor， and at least one memory including computer program code， wherein the at least one memory and the computer program code are configured， with the at least one processor， to

determine a rule to be used by a communication device for handling dual connectivity state change commands by medium access control (MAC) entities，

communicate a control message to at least one mobile communication device according to claim 28 for configuring the communication device accordingly.
A computer program comprising program code means adapted to perform the steps of any of claims 1 to 16 when the program is run on a data processing apparatus.