Patent Description:
3GPP in Release <NUM> proposes dual connectivity for increasing user's throughput. Dual connectivity to at least two cells may be served by different evolved NodeBs (eNB), linked with non-ideal backhaul, e.g., there may be an eNB in charge of a cluster of cells. Therefore, a user equipment (UE) may be served by multiple eNBs when it is in dual connectivity mode.

Under the present framework of the dual connectivity, a procedure of inter-node radio resource aggregation (INRRA) is proposed to build a UE's connection with more than one node. The INRRA can provide traffic load sharing between the network nodes and improve per-user throughput by utilizing radio resources in more than one node. In other words, the UE may receive different data and service from more than one network nodes. Within the context of the present invention, a node or a network node could be referred to an eNB.

Moreover, different service and different data may have different quality of service (QoS) requirements. In INRRA, traffic streams may be split over more than one network node depending on QoS requirements of each traffic type, loading situation, channel condition, and the combination thereof. In other words, a radio bearer may exist on more than one network node. Multiple network nodes need to maintain the QoS of the radio bearers.

However there is no specification for radio bearer establishment on multiple network nodes. Therefore, data transmission/reception to/from more than one network nodes cannot be realized. <CIT> is related prior art.

The present application aims at providing a method of radio bearer establishment in dual connectivity for a first and second base station in order to solve the abovementioned problems.

The dependent claims pertain to corresponding further developments and improvements.

<FIG> is a schematic diagram of a wireless communication system <NUM>. The wireless communication system <NUM> is a LTE/LTE-Advanced system or other mobile communication systems and is briefly composed of at least two network nodes, i.e. an master eNB (hereafter called M-node) and a secondary eNB (hereafter called S-node), and a user equipment (UE). In dual connectivity, M-node terminates at least S1-MME and therefore acts as mobility anchor towards the core network including a Mobility Management Entity (MME). On the other hand, S-node provides additional radio resource for the UE, which is not the M-node. <FIG> is simply utilized for illustrating the structure of the wireless communication system <NUM>, where the number of UEs and eNBs are not limited herein. The UEs can be devices such as mobile phones, computer systems, machine type devices, etc. Besides, the network node and the UE can be seen as a transmitter or receiver according to transmission direction, e.g., for uplink (UL), the UE is the transmitter and the network node is the receiver, and for downlink (DL), the network node is the transmitter and the UE is the receiver.

As shown in <FIG>, the UE has a first radio resource control (RRC) connection with M-node. The first RRC connection includes at least a radio bearer (RB). The term RB may cover signaling radio bearer (SRB) and data radio bearer (DRB). Based on 3GPP specification of Radio Resource Control (RRC) protocol, SRB is defined as RB that is used only for the transmission of RRC and non-access stratum (NAS) message. DRB transports the packets of an enhanced packet system (EPS) bearer between a UE and an eNB. When a data radio bearer exists, there is one to one mapping between this DRB and the EPS bearer/E-UTRAN radio access bearer (E-RAB). An E-RAB uniquely identifies the concatenation of an S1 bearer and the corresponding DRB. When an E-RAB exists, there is a one to one mapping between this E-RAB and an EPS bearer of the NAS. An EPS bearer/E-RAB is the level of granularity for bearer level QoS control in the EPC/E-UTRAN. The bearer may be associated with QoS parameters. For example, QoS Class Identifier (QCI), Allocation and Retention Priority (ARP), Guaranteed Bit Rate (GBR), Maximum Bit Rate (MBR), per APN Aggregate Maximum Bit Rate (APN-AMBR), and per UE Aggregate Maximum Bit Rate (UE-AMBR).

<FIG> illustrates a schematic diagram of an exemplary communication device <NUM>. The communication device <NUM> can be the UE, M-node, or S-node shown in <FIG>. The communication device <NUM> may include a processing means <NUM> such as a microprocessor or Application Specific Integrated Circuit (ASIC), a storage unit <NUM> and a communication interfacing unit <NUM>. The storage unit <NUM> may be any data storage device that can store program code <NUM>, for access by the processing means <NUM>. Examples of the storage unit <NUM> include, but are not limited, to a subscriber identity module (SIM), read-only memory (ROM), flash memory, random-access memory (RAM), CD-ROMs, magnetic tape, hard disk, and optical data storage device. The communication interfacing unit <NUM> is preferably a radio transceiver and can exchange wireless signals with a network (i.e. E-UTRAN) according to processing results of the processing means <NUM>.

<FIG> is a flowchart of a process <NUM> according to an example of the present disclosure. The process <NUM> is utilized in the communication device <NUM> (i.e. the M-node in <FIG>) for RB establishment in dual connectivity. The process <NUM> may be compiled into a program code <NUM> to be stored in the storage unit <NUM>, and may include the following steps:.

According to the process <NUM>, the UE connects to the M-node and transmits a measurement report associated to the at least one S-node to the M-node. In addition, the M-node asks one or more than one S-nodes to establish or release at least a RB with the request message according to the measurement report. More specific, the M-node may establish a new RB on S-nodes, or switch a subset of RBs, which is already established on the M-node, from M-node to other S-nodes. In an embodiment, the M-node may keep the switched RBs for data transmission/reception for the UE. Or, the M-node may release the switched RBs on the M-node.

The M-node may switch a subset of RBs for the UE from the M-node to the S-node, or release a subset of RBs because of QoS requirements of each traffic type, loading situation, channel condition, S-node connection failure, and the combination thereof. In addition, the M-node may switch a subset of RBs from a S-node back to the M-node, or release RBs on the S-node because the UE lose connection to the S-node due to movement or loading situation change.

Take an example based on the process <NUM>. <FIG> is a schematic diagram of a RB establishment with S-node configuration completion. <FIG> is a schematic diagram of a RB establishment with S-node configuration failure. The RB establishment procedure in dual connectivity comprises phases of preparation and activation. In the phase of preparation, a UE connects to a M-node and sends a measurement report to the M-node (step <NUM>). The measurement report may include the channel quality of S-nodes, e.g., RSRP, RSRQ. In the invention, the M-node decides to establish, or release a subset of RBs for e UE on one or more than one S-node according to the measurement report (step <NUM>). The M-node may send "S-node Request" message to one or more than one S-node, wherein the "S-node Request" message may include information of the RBs that the M-node would like to establish or release on the S-node. For example, the "S-node Request" message may include an E-RAB ID list and/or RB ID, E-RAB Level QoS Parameters, RB Level QoS Parameters. After the S-node receives the "S-node Request" message, the S-node may decide whether or not to accept the M-node's request (step <NUM>). In addition, the S-node sends "S-node Request ACK" message to the M-node, wherein the "S-node Request ACK" message includes information about the S-nodes' decision for the RB which is accepted, rejected, or released. For example, the "S-node Request ACK" message may comprise an E-RAB ID list and/or RB ID, information related to the configurations of RBs on S-node, information related to connection setup to S-node. After the M-node receives "S-node Request ACK" message, the M-node may select one or more than one S-node for establishing the RBs (step <NUM>). For example, the M-node may select one or more than one S-node to establish RBs according to S-nodes' ACK, M-node's preference, loading balance, and the combination thereof. The M-node may send "S-node Configuration" message including configurations of the S-node(s) to the UE for performing connection to the S-node(s). The "S-node Configuration" message may comprise cell list, physical cell ID, radio resource configuration for S-node (maybe include configurations of RB). In addition, the "S-node Configuration" message may be included in a RRC connection reconfiguration message.

Moreover, the M-node and the S-node(s) may setup a connection for the data transmission and/or forwarding. The S-node(s) may buffer packets from the M-node.

In the phase of activation, the UE may perform synchronization (i.e. a random access procedure) to the S-node, and the S-node may respond with uplink resource allocation and uplink synchronization information, e.g., timing advance. In response to "S-node Configuration" message, the UE may send a message to notify the M-node whether or not the UE completes the S-node configuration. For example, the UE sends "S-node Configuration Complete" message to the M-node in <FIG>, or sends "S-node Configuration Failure" message to the M-node in <FIG>. Further, the M-node may send "M-node Notification" message to the S-node for activating the established RBs. The "M-node Notification" message may comprise an E-RAB ID list and/or RB ID.

The M-node may release the configurations of the RBs on M-node which are the same as the RBs established on the S-node.

In an embodiment, the S-node(s) which are not selected to activate the RBs may release the reserved resource according to the "M-node Notification" sent from the M-node to release the reserved resource. Or, the S-node(s) waits for a pre-determined period of time to release the reserved resource. For example, after the release timer expires, the S-node releases the reserved resource. In addition, the M-node may deliver buffered and in transit packets to the S-node(s) if the UE completes the S-node configuration. Or, the M-node may send a message to the S-nodes to convey the sequence number (SN) status if the UE completes the S-node configuration.

<FIG> illustrates a schematic diagram of a first exemplary embodiment for the RB establishment procedure. In the first embodiment, the M-node sends multiple "S-node Request" messages to the S-node#<NUM>-<NUM> for asking whether or not to provide service for a subset of RBs for the UE. The "S-node Request" messages may include the same RB ID list or different RB ID list. In <FIG>, the "S-node Request" message includes the same RB ID list, i.e. RB#<NUM>-<NUM>, to be established on the S-node#<NUM>-<NUM>. After receiving the "S-node Request" message, the S-node#<NUM>-<NUM> may decide whether to accept or reject RB establishment on the S-node#<NUM>-<NUM>. The S-node#<NUM>-<NUM> reply "S-node Request ACK" messages indicating whether to accept or reject the RB establishment, to the M-node. In this case, the S-node#<NUM> accepts RB establishment, the S-node#<NUM> rejects RB establishment, and the S-node#<NUM> accepts RB establishment. After receiving the "S-node Request ACK" messages from the S-node#<NUM>-<NUM>, the M-node may select which S-node should establish RB. In this case, the M-node selects the S-node#<NUM> to establish RB, and then sends the "S-node Configuration" message including configuration of the S-node#<NUM> to the UE. Therefore, the UE connects to the S-node#<NUM> according to the "S-node Configuration" message. The UE may send the "S-node Configuration Complete" message to the M-node if the UE completes configuration for the S-node#<NUM>. After receiving "S-node Configuration Complete" message, the M-node may send the "M-node Notification" message including RB IDs, i.e. RB#<NUM>-<NUM>, to the S-node#<NUM> to activate the RB#<NUM>-<NUM> on the S-node#<NUM>. Thus, the UE is able to transmit/receive data with RB#<NUM>-<NUM> on the S-node#<NUM>, so as to increasing user's throughput. On the other hand, the M-node may optionally inform the other S-nodes, which is not selected by the M-node, to release the reserved resources with "M-node Notification" message. The "M-node Notification" message may include the RB ID to release the reserved resource. For example, in <FIG>, the S-node#<NUM> is informed to release the reserved resources with "M-node Notification" message. In other words, the RB-establishment is used for establishing RBs on at least a network node.

<FIG> is a schematic diagram of a second exemplary embodiment for the RB establishment procedure. Similar to the first exemplary embodiment, the M-node may send multiple "S-node Request" messages to multiple S-nodes. The S-nodes may reply "S-node Request ACK" messages to the M-node. After receiving the "S-node Request ACK" message, the M-node may select the S-node#<NUM> and S-node#<NUM>, and then send the "S-node Configuration" message to the UE. The UE may send the "S-node Configuration Complete" message to the M-node if completing configuration for the S-node#<NUM> and S-node#<NUM>. The M-node may send the "M-node Notification" message including RB IDs, RB#<NUM>-<NUM>, to the S-node#<NUM> to activate RB#<NUM>-<NUM> on the S-node#<NUM>, and release the RB#<NUM>-<NUM> on the S-node#<NUM>. In addition, the M-node sends "M-node Notification" message including RB IDs, RB#<NUM>-<NUM>, to S-node#<NUM> to activate RB#<NUM>-<NUM> on the S-node#<NUM> and release RB#<NUM>-<NUM> on the S-node#<NUM>.

<FIG> is a schematic diagram of a third exemplary embodiment for the RB establishment procedure. The M-node may send multiple "S-node Request" messages to multiple S-nodes. The S-nodes may reply "S-node Request ACK" message to accept or reject a subset of RB-establishment. The detailed description can be referred from above. The "S-node Request ACK" message may include a bit map to indicate establishment acceptance or rejection for each RB. For example, as shown in <FIG>, S-node#<NUM>-<NUM> respectively decides which RB could be established. The S-node#<NUM> transmits "S-node Request ACK" message indicating that establishment for RB#<NUM>-<NUM> is accepted and for RB#<NUM>-<NUM> is rejected to the M-node. The S-node#<NUM> transmits "S-node Request ACK" message indicating that establishment for RB#<NUM>/<NUM> is accepted and for RB#<NUM>/<NUM>/<NUM> is rejected, to the M-node. The S-node#<NUM> transmits "S-node Request ACK" message indicating that establishment for RB#<NUM>-<NUM> is accepted, and for RB#<NUM> is rejected, to the M-node. As a result, the M-node knows which RB the S-node could establish. The M-node may select the S-node#<NUM>-<NUM> to establish RBs. The M-node sends "M-node Notification" message including RB IDs, RB#<NUM>-<NUM>, to the S-node#<NUM> to activate RB#<NUM>-<NUM> on the S-node#<NUM>. The M-node sends "M-node Notification" message including RB IDs, RB#<NUM>, to S-node#<NUM> to activate RB#<NUM> on the S-node#<NUM>, and release RB#<NUM> on the S-node#<NUM>. The M-node sends "M-node Notification" message including RB IDs, RB#<NUM>-<NUM>, to S-node#<NUM> to activate RB#<NUM>-<NUM> on the S-node#<NUM> and release RB#<NUM>-<NUM> on the S-node#<NUM>.

<FIG> is a schematic diagram of a fourth exemplary embodiment for the RB establishment procedure. The M-node may send "S-node Request" messages including different RB ID list to the S-node#<NUM>-<NUM>. For example, the M-node sends the "S-node Request" message including RB#<NUM> to the S-node#<NUM>, sends "S-node Request" message including RB#<NUM>-<NUM> to the S-node#<NUM>, and sends "S-node Request" message including RB#<NUM>-<NUM> to the S-node#<NUM>. The S-node#<NUM> may accept establishment for RB#<NUM>, and transmits the "S-node Request ACK" message to notify the M-node. The S-node#<NUM> may reject establishment for RB#<NUM>-<NUM>, and transmit the "S-node Request ACK" message to notify the M-node. The S-node#<NUM> may accept establishment for RB#<NUM>-<NUM>, and transmits "S-node Request ACK" message to notify the M-node. After the M-node receives the "S-node Request ACK" message from the S-node#<NUM>-<NUM>, the M-node may select the S-node#<NUM> and S-node#<NUM> for RB establishment. The M-node further sends the "M-node Notification" message including RB IDs, RB#<NUM>, to S-node#<NUM> to activate RB#<NUM> on the S-node#<NUM>, and sends "M-node Notification" message including RB IDs, RB#<NUM>-<NUM>, to S-node#<NUM> to activate RB#<NUM>-<NUM> on the S-node#<NUM>.

<FIG> is a schematic diagram of a fifth exemplary embodiment for the RB establishment procedure. The M-node sends the "S-node Request" message including RB#<NUM> to the S-node#<NUM>, the "S-node Request" message including RB#<NUM>-<NUM> to the S-node#<NUM>, and the "S-node Request" message including RB#<NUM>-<NUM> to the S-node#<NUM>. The S-node#<NUM>-<NUM> may decide which RB could be served. In this case, the S-node#<NUM> may accept RB#<NUM>, the S-node#<NUM> may accept RB#<NUM> and reject RB#<NUM>, and the S-node#<NUM> may accept RB#<NUM> and reject RB#<NUM>. Similar to the third exemplary embodiment in <FIG>, the "S-node Request ACK" message include a bit map to indicate establishment acceptance or rejection for each RB. The detailed description can be referred from above. After receiving "S-node Request ACK" messages from the S-node#<NUM>-<NUM>, the M-node may select S-node#<NUM>-<NUM> for RB establishment. In addition, the M-node may send the "M-node Notification" message including RB IDs, RB#<NUM>, to S-node#<NUM> to activate RB#<NUM>, sends "M-node Notification" message including RB IDs, RB#<NUM>, to S-node#<NUM> to activate RB#<NUM>, and sends "M-node Notification" message including RB IDs, RB#<NUM>, to S-node#<NUM> to activate RB#<NUM>.

<FIG> is a schematic diagram of a sixth exemplary embodiment for the RB establishment procedure. The M-node may ask S-node#<NUM> to establish back or release a subset of RBs with the "S-node Request" message. The S-nodes may reply with "S-node Request ACK" message to the M-node. For example, as shown in <FIG>, the S-node#<NUM> provides service for RB#<NUM>-<NUM> for the UE. The M-node may send "S-node Request" message including RB#<NUM>-<NUM> to the S-node#<NUM> for releasing RB#<NUM>-<NUM>. Therefore, the S-node#<NUM> merely provides service for RB#<NUM>-<NUM> for the UE. On the other hand, the M-node may establish RB#<NUM>-<NUM> on itself.

<FIG> is a schematic diagram of a seventh exemplary embodiment for the RB establishment procedure. The M-node sends "S-node Request" messages each including RB#<NUM>-<NUM> to be established on the S-node#<NUM>-<NUM>, to the S-node#<NUM>-<NUM>. The S-nodes#<NUM>-<NUM> may decide which RB could be served. In this case, the S-node#<NUM> may accept RB#<NUM>-<NUM> and reject RB#<NUM>-<NUM>, the S-node#<NUM> may accept RB#<NUM>/<NUM> and reject RB#<NUM> /<NUM>/<NUM>, and the S-node#<NUM> may accept RB#<NUM>-<NUM> and reject RB#<NUM>. The M-node may select S-node#<NUM>-<NUM> to establish RBs, and then sends configuration of the S-node#<NUM>-<NUM> to the UE. If the UE fails to complete the S-node configuration for S-node#<NUM>, the M-node may send the "M-node Notification" message to the S-node#<NUM> to indicate the reserved RB(s) to be released. In addition, the M-node may re-send the "S-node Configuration" message to the UE for performing connection to the S-node#<NUM>-<NUM>. After the configuration for the S-node#<NUM>-<NUM> is completed, the M-node send the "M-node Notification" message including RB IDs, RB#<NUM>, to S-node#<NUM> to activate RB#<NUM> and release RB#<NUM>, and sends "M-node Notification" message including RB IDs, RB#<NUM>-<NUM>, to S-node#<NUM> to activate RB#<NUM>-<NUM>.

<FIG> is a schematic diagram of an eighth exemplary embodiment for the RB establishment procedure. The RB-establishment procedure may switch part of RBs from the M-node to S-node. i.e., an RB of a UE may be maintained on M-node and S-node simultaneously. The data corresponding to this RB could be transmitted through M-node and S-node. In other words, the M-node may not release the configuration of the RB(s) which are established to S-node. For example, as shown in <FIG>, the M-node may provide service for RB#<NUM>-<NUM>. The M-node may ask S-node#<NUM> whether or not to provide service for a subset of RBs of the UE with "S-node Request" message, wherein the "S-node Request" message including RB#<NUM>-<NUM>. The S-node#<NUM> may decide whether to accept the RB establishment request. The S-node#<NUM> may accept RB#<NUM>-<NUM> and sends "S-node Request ACK" message to the M-node. The M-node may select S-node#<NUM>, and send the "M-node Notification" message including RB IDs, RB#<NUM>-<NUM> to the S-node#<NUM> to activate RB#<NUM>-<NUM>. Therefore, both of the M-node and S-node#<NUM> may provide service for RB#<NUM>-<NUM>.

<FIG> is a schematic diagram of a ninth exemplary embodiment for the RB establishment procedure. The RB-establishment procedure may establish part of data transmission of a RB on S-node, i.e., an RB of a UE may be maintained on S-node only. The data corresponding to this RB could be transmitted through M-node and S-node. In this case, M-node may not maintain the configuration of the RB(s) which are established to S-node. For example, as shown in <FIG>, the M-node may ask S-node#<NUM> whether or not to provide service for a subset of RBs of a UE with "S-node Request" message including RB#<NUM>-<NUM>. The S-node#<NUM> may decide which RB could be served. In this case, the S-node#<NUM> accepts RB#<NUM>-<NUM>. The M-node may send the "M-node Notification" message including RB IDs, RB#<NUM>-<NUM>, to S-node#<NUM> to activate RB#<NUM>-<NUM>. Thus, the S-node#<NUM> may provide service for RB#<NUM>-<NUM>. As can be seen, the RB establishment procedure of the present invention may establish a new RB on a network node (i.e. S-node).

<FIG> is a flowchart of a process <NUM> according to an example of the present disclosure. The process <NUM> is utilized in the communication device <NUM> (i.e. the S-node in <FIG>) for RB establishment in dual connectivity. The process <NUM> may be compiled into a program code <NUM> to be stored in the storage unit <NUM>, and may include the following steps:.

According to the process <NUM>, the S-node receives from the M-node, the "S-node Request" message indicating RBs to be released or established on the S-node. The S-node determines whether to accept or reject the RB release or establishment, and then responds with "S-node Request ACK" message to the M-node. The "S-node Request" message may include the same or different RB ID list. The "S-node Request ACK" message may include a bit map to indicate establishment acceptance or rejection for each RB. The detailed operation can be referred from above, so it is omitted herein.

<FIG> is a flowchart of a process <NUM> according to an example of the present disclosure. The process <NUM> is utilized in the communication device <NUM> (i.e. the UE in <FIG>) for RB establishment in dual connectivity. The process <NUM> may be compiled into a program code <NUM> to be stored in the storage unit <NUM>, and may include the following steps:.

According to the process <NUM>, the UE receives "S-node Configuration" message from the M-node, and then performs connection to S-node according to the information of "S-node Configuration" message. If the UE completes the configuration for the S-node, the UE transmits "S-node Configuration Complete" message to the M-node. If the UE fails to complete the configuration for the S-node, the UE transmits "S-node Configuration Failure" to the M-node. Therefore, the M-node knows whether to activate or release the RBs on the S-node accordingly.

The abovementioned steps of the processes, including suggested additional steps, can be realized by means that could be hardware, firmware known as a combination of one or more hardware devices and computer instructions and data that reside as read-only software on the hardware device or an electronic system. Examples of hardware include analog, digital and mixed circuits known as microcircuit, microchip, or silicon chip. Examples of the electronic system include a system on chip (SOC), system in package (SiP), a computer on module (COM) and the communication device <NUM>.

Claim 1:
A method of radio bearer establishment or release in dual connectivity for a first base station in a wireless communication system, characterized by the method comprising:
by the first base station, connecting to a user equipment of the wireless communication system (<NUM>);
by the first base station, determining whether to establish or release at least a radio bearer for the user equipment on at least a second base station (<NUM>), wherein the first base station and the at least a second base station are connected to non-ideal backhaul;
by the first base station, transmitting to the at least a second base station (<NUM>) a request message including information of the at least one radio bearer to be established or released on the at least a second base station and information that the request message is an establishment request or a release request; and
by the first base station, receiving a response message including information about accepting or rejecting establishment or release for the at least a radio bearer on the at least a second base station, from the at least a second base station, wherein the response message includes information of at least one radio bearer identity to be established or released, information of release acknowledgement, information related to configuration of radio bearers on the at least a second base station, and information related to connection setup to the at least a second base station; and
by the first base station, establishing or releasing the at least a radio bearer on the at least a second base station.