EP2982160A2

EP2982160A2 - Method and apparatus for supporting dual connectivity

Info

Publication number: EP2982160A2
Application number: EP14734546.6A
Authority: EP
Inventors: Tao Yang; Pingping Wen
Original assignee: Alcatel Lucent SAS
Current assignee: Alcatel Lucent SAS
Priority date: 2013-04-03
Filing date: 2014-04-03
Publication date: 2016-02-10
Also published as: JP2016518062A; CN104105220B; CN104105220A; WO2014162203A2; WO2014162203A3; KR20150138359A

Abstract

Method and apparatus for supporting dual connectivity is provided in this invention. The method includes: an initialization step, when a UE initially accesses a macro base station, connecting the UE to a Pcell such that a current LCH is handled by the Pcell, wherein the Pcell is associated with the macro base station and operates on a primary component carrier; an indication step for indicating to the UE through a dedicated RRC message that the LCH is to be handled by the macro base station or a small cell base station, or is to be handled by the Pcell or a Scell, wherein the Scell operates on a secondary component carrier.

Description

METHOD AND APPARATUS FOR SUPPORTING DUAL CONNECTIVITY

TECHNICAL FIELD

The present disclosure relates generally to the wireless communication field, and more particularly, to a method and apparatus for supporting dual connectivity.

BACKGROUND

In a heterogeneous wireless communication network, there are usually macro base stations with broader coverage and micro base stations with relative small coverage. Figure 1 illustrates a schematic diagram of a wireless communication network 100 in prior art. As illustrated in Figure 1, the wireless communication network 100 includes a macro base station 110, which provides basic network coverage 120, and one or more small cell base stations 132, 134, 136, and 138 with lower power, which provide relatively small network coverage 142, 144, 146, and 148 (signed by backlash in the figure) respectively. A User Equipment (UE) 150 located in the common coverage of the macro base station and the small cell base station will be able to establish communication connections with both the macro base station 110 and the corresponding small cell base station (e.g., the small cell base station 134) simultaneously.

Currently, the new study item on small cell enhancement-high layer (the study item of the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Release 12 (R12) (SI: RP-121800)) has been approved in RAN 58. One important objective of this SI is about "dual connectivity" and " the separation of C(Control)-plane and U(User)-plane in different nodes", and the main research content and objective are as follows:

(1) Identify and evaluate the benefits of UEs having dual connectivity with macro and small cells served by different or identical carrier and for which scenarios such dual connectivity is feasible and beneficial;

(2) Identify and evaluate potential architecture and protocol enhancements for the feasible scenario of dual connectivity to minimize impacts on core network if feasible, including: overall structure of Control plane (C-plane) and User plane (U-plane) and their relation to each other, e.g., supporting C-plane and U-plane in different nodes, termination of different protocol layers, etc..

One potential solution to support "dual connectivity" is based on the Carrier

Aggregation (CA) concept with a macro cell used as a Primary Cell (Pcell) operating on a primary component carrier and a small cell used as a Secondary Cell (Scell) operating on a secondary component carrier. The most important benefit of this concept is no Pcell change situation will occur and hence no handover procedure will be triggered during a UE staying in macro cell coverage. And when the UE moves into small cell coverage, the small cell can be added as Scell. In general, there maybe multiple carriers controlled by a Macro Base Station (eNB_M) and a Small Cell Base Station (eNB_S) respectively. This means there will be one Pcell and the eNB_M may control zero/one/multiple S cells and the eNB_S may also control zero/one/multiple Scells.

Based on this "dual connectivity", another feature on separation of C-plane and U-plane is proposed in the SI. The background is based on such consideration that the small cell maybe located on higher frequency band, such as 3.5G. Hence it is beneficial to have important signaling, such as Physical Layer (PHY) signaling, Radio Resource Control (RRC) signaling to be transmitted in the macro cell for higher reliability. Hence it is beneficial to support the separation of RRC signaling and data transmission on different cells. Considering current CA specification, to support this separation, the key impact is the related operation to UE side Logical Channel Priority (LCP) procedure, as proposed in the Chinese patent application submitted by the applicant on 18 January 2013, entitled "METHOD FOR REALIZING THE SEPARATION OF CONTROL PLANE AND USER PLANE BASED ON CARRIER AGGREGATION".

In addition, most companies showed their supporting on "dual connectivity". One popular and largely proposed solution to support this feature is based on the CA concept. Regarding the separation of C-plane and U-plane, although there is still no clear decision as to whether to support this feature or not, its benefits have been recognized by many companies, especially on mobility management procedures. Also, to avoid the non- ideal interface between different base stations' impact on the system's performance, it is proposed by many companies that the eNB_S should do the scheduling operation to control its own Tx/Rx but not depend on the eNB_M scheduling. This means there will be two distributed scheduler procedures working simultaneously in the eNB_M and the eNB_S respectively. To facilitate this situation, it is also proposed that data of one service, one Logical Channel (LCH) or one Radio Bearer (RB) should only be sent on one node. This is similar to the concept of C-plane and U-plane separation. For this concept, the data of Signaling Radio Bearer (SRB) will only be sent through the eNB_M, while the data of Data Radio Bearer (DRB) will only be sent through the eNB_S. So we can see that this C-plane and U-plane separation concept is beneficial for achieving higher small cell scheduling efficiency. In summary, it is beneficial to support the proposal of sending the data of one service/RB/LCH through one node, which will help to improve the small cell scheduling efficiency. The present disclosure discusses and proposes solutions on how to realize this proposal.

SUMMARY

In view of the above problems, this invention provides several specific solutions that guarantee the data of one service/RB/LCH to only be sent through one cell/node, and also provides how to handle the impact of a secondary cell behavior in the case that the data of one service/RB/LCH is only sent through one cell/node.

According to one aspect of this invention, a method for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations is provided. The method comprises: an initialization step for, when a User Equipment (UE) initially accesses the macro base station, connecting the UE to a Primary Cell (Pcell) or the macro base station such that a current Logical Channel (LCH) is handled by the Pcell or the macro base station, wherein the Pcell is associated with the macro base station and operates on a primary component carrier; and an indication step for, indicating to the UE through a dedicated Radio Resource Control (RRC) message that the LCH is to be handled by the macro base station or one of the small cell base station, or is to be handled by the Pcell or a Secondary Cell (Scell), wherein the Scell operates on a secondary component carrier.

According to another aspect of this invention, a method for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations is provided. The method comprises: having data of a Logical Channel (LCH) to only be handled by a Primary Cell (Pcell) or a Secondary Cell (Scell), or to only be handled by the macro base station or one of the small cell base station; when the LCH mapped Scell of the small cell base station is de-activated or released, and when there is at least another one active Scell of the small cell base station in the wireless communication network, sending data of the LCH through the active small cell base station; and when all the Scells of small cell base stations are de-activated or released, sending data of the LCH through the macro base station.

According to another aspect of this invention, a method for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations is provided. The method comprises: having data of a Logical Channel (LCH) to only be handled by a Primary Cell (Pcell) or a Secondary Cell (Scell), or to only be handled by the macro base station or one of the small cell base stations; and when the LCH mapped Scell of the small cell base station is de-activated, pending transmission of the LCH until the Scell is re-activated.

According to another aspect of this invention, a method for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations is provided. The method comprises: having data of a Logical Channel (LCH) to only be handled by a Primary Cell (Pcell) or a Secondary Cell (Scell), or to only be handled by the macro base station or one of the small cell base stations; when the Scell of the small cell base station is de-activated, the macro base station indicating a UE behavior by setting "R" bit in the Scell activation/de-activation MAC CE.

According to another aspect of this invention, an apparatus for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations is provided. The apparatus comprises: an initialization unit, which is configured to, when a User Equipment (UE) initially accesses to the macro base station, connect the UE to a Primary Cell (Pcell) or the macro base station such that a current Logical Channel (LCH) is handled by the Pcell or the macro base station, wherein the Pcell is associated with the macro base station and operates on a primary component carrier; and an indication unit, which is configured to indicate to the UE through a dedicated Radio Resource Control (RRC) message that the LCH is to be handled by the macro base station or one of the small cell base stations, or is to be handled by the Pcell or a Secondary Cell (Scell), wherein the Scell operates on a secondary component carrier.

According to another aspect of this invention, an apparatus for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations is provided. The apparatus comprises: a dual connectivity enabling unit, which is configured to have data of a Logical Channel (LCH) to only be handled by a Primary Cell (Pcell) or a Secondary Cell (Scell), or to only be handled by the macro base station or one of the small cell base stations; and a cell change processing unit, which is configured to, when the LCH mapped Scell of the small cell base station is de-activated or released, and when there is at least one Scell of another active small cell base station in the wireless communication network, send data of the LCH through the active small cell base station; and wherein the processing unit is further configured to, when all Scells of small cell base stations are de-activated or released, send data of the LCH through the macro base station.

With the solutions of this invention, the small cell scheduling efficiency may be improved and the separation of C-plane and U-plane can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

After referring to the descriptions of the specific embodiments of the invention illustrated in the following figures, this invention will be better understood, and other objectives, details, features and benefits of this invention will become more obvious.

Figure 1 illustrates a schematic diagram of a network architecture in prior art.

Figure 2 illustrates a flow chart of a method for supporting dual connectivity according to the embodiments of the invention.

Figure 3 illustrates a flow chart of another method for supporting dual connectivity according to the embodiments of the invention.

Figure 4 illustrates a block diagram of an apparatus for supporting dual connectivity according to the embodiments of the invention.

Figure 5 illustrates a block diagram of another apparatus for supporting dual connectivity according to the embodiments of the invention.

Figure 6 illustrates a schematic diagram of the Scell activation/de-activation MAC CE in prior art; and

Figure 7 illustrates a schematic diagram of the Scell activation/de-activation MAC CE reconfigured according to the embodiments of the invention.

In all the above figures, the same or similar signs represent the same, similar or corresponding features or functionalities.

DETAILED DESCRIPTION

Hereinafter, the preferred embodiments of this disclosure will be described in detail with reference to the accompanying drawings. Although the accompanying drawings show the preferred embodiments of this disclosure, it should be understood that the disclosure may be implemented in various forms, without being limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure more thorough and complete, and can convey the scope of the disclosure to those skilled in the art completely.

Figure 2 illustrates a flow chart of a method 200 for supporting dual connectivity according to the embodiments of the invention. As illustrated in Figure 2, the method 200 includes an initialization step 210, wherein when a UE initially accesses a macro base station eNB_M, connecting the UE to a Pcell or the eNB_M such that a current LCH is handled by the Pcell or the eNB_M, wherein the Pcell is associated with the eNB_M and operates on a primary component carrier.

Next, in an indication step 220, the UE is indicated through a dedicated RRC message whether the LCH will be handled by the eNB_M or the eNB_S, or whether the LCH will be handled by the Pcell or a Scell.

As stated above, to support dual connectivity, it is important to guarantee that the data of a LCH is only sent through one cell/node, which is inline with the concept of C-plane and U-plane separation for achieving higher scheduling efficiency. Regarding how to indicate to the UE which LCH is handled by which cell/node, there are three options:

Option Al: indicating to the UE through which cell (Pcell or Scell) or through which node (eNB_M or eNB_S) the RB/LCH will be sent through a RB configuration/reconfiguration RRC message;

Option A2: indicating to the UE which service/RB/LCH the Scell will handle through a Scell configuration/reconfiguration RRC message;

Option A3: defining a new RRC message to configure each service/RB/LCH to indicate to the UE the Pcell or Scell for handling each service/RB/LCH.

These three options are discussed in detail below. Also, how to realize the separation of C-plane and U-plane is discussed in the following based on these three options.

With respect to option Al

For option Al, when configuring/reconfiguring the RB, the target cell (e.g., Pcell or

Scell) or the target node (e.g., eNB_M or eNB_S) for this RB transmission is indicated by adding a new information element to the RB configuration/reconfiguration message. And two sub-options may be considered regarding definition of this new information element:

Sub-option Al.l: this new information element indicates that the configured/reconfigured RB is handled by a Pcell or a Scell.

In one embodiment, the new information element includes index of the Pcell or Scell. The length of the new information element depends upon the number of all supported Pcells and Scells. For instance, when the network 100 supports one Pcell and seven Scells, the length of the information element is 3 bits. In this case, for example, the index 000 refers to the Pcell, and indexes 001-111 refer to the supported seven Scells respectively. Further, the new information element being empty indicates that the configured/reconfigured RB is handed by the Pcell.

Sub-option A1.2: this new information element indicates that the configured/reconfigured RB is handled by the eNB_M or the eNB_S .

In one embodiment, the new information element includes the index of the eNB_M or eNB_S. The length of the new information element depends upon the number of eNB_Ss that a UE can simultaneously connect with. For instance, when only one eNB_M and one eNB_S can be supported to be connected to one UE simultaneously, 1 bit is needed for this information element. If one eNB_M and up to three eNB_Ss can be connected to one UE simultaneously, 2 bits are needed for this information element. In this case, for example, the index 00 refers to the eNB_M, and the indexes 01-11 respectively refer to the three eNB_Ss.

Further, the new information element being empty indicates that the configured/reconfigured RB is handed by the eNB_M.

As can be seen, the only difference between sub-option A 1.1 and sub-option A 1.2 lies in the different granularities of the RB/ LCH processing unit indicated by the information element.

Sub-option A 1.1 indicates explicitly the specific cell (e.g., Pcell or Scell) for handling the RB/LCH, while the information about the Pcell or Scell further implicitly indicates which base station (e.g., eNB_M or eNB_S) will handle this RB/LCH.

With respect to option A2

For option A2, when configuring/reconfiguring the Scell, the eNB_M indicates to the UE the RB/LCH to be handled by the configured/reconfigured Scell by adding a new information element to the Scell configuration/reconfiguration RRC message. For example, it may indicate to the UE which LCH the configured/reconfigured Scell can handle. If the configured/reconfigured Scell belongs to a certain eNB_S, the UE is clear which logical channel will be handed by the eNB_S. This effect is similar to above proposed sub-option A 1.1. For example, when a first Scell is setup after the initialization step (step 210), the eNB_M can indicate to the UE whether some current LCHs will be handled by this Scell. If yes, the related LCH(s) will not be handled by the Pcell once more.

In addition, when the RB/LCH is further configured, two following sub-options can be considered to handle these new LCHs. (1) Sub-option A2.1: updating the RB/LCH configuration/reconfiguration message to add a new information element to indicate whether the configured/reconfigured RB/LCH is handled by the Pcell or the Scell. The specific indicating method is similar to the aforementioned sub-option ALL

(2) Sub-option A2.2: using the Scell configuration/reconfiguration RRC message to indicate to the UE whether the reconfigured/reconfigured RB/LCH is handled by the eNB_M or the eNB_S. Before the UE receiving this Scell configuration/reconfiguration RRC message, the configured/reconfigured RB/LCH will be handed by the Pcell by default, as stated in step 210.

Compared with sub-option A2.1, sub-option A2.2 will not impact the RB configuration RRC procedure.

With respect to option A3

For option A3, a new dedicated RRC message is defined in R12 to indicate the Pcell or the Scell for handling each RB/LCH, or indicate the eNB_M or the eNB_S for handling each RB/LCH. Before receiving this new RRC message, for this new configured/reconfigured RB, the UE knows that it will be handled by the Pcell by default.

As can be seen, option A3 has the same effect as option Al and option A2, with the cost of defining a new dedicated RRC message. Hence below we mainly focus on option Al and option A2.

According to the aforementioned method 200 for supporting dual connectivity, the data of one LCH is guaranteed to be sent through one cell (e.g., Pcell or Scell) only, or be sent by one node (e.g., eNB_M or eNB_S) only, so that the separation of C-plane and U-plane can be realized. Of course, these procedures may also realize that some LCH/RB is handled by multiple cells or multiple nodes.

In one embodiment, option Al and option A2 can be simplified as below to support the C-plane and U-plane separation according to current SI proposal.

For option Al, when the SRB is setup, no update to the RB setup procedure, so that the SRB will be handed by a Pcell or an eNB_M by default. And when the DRB is setup, a new RB setup procedure will be used and this new information element will be related to the eNB_S. That is, sub-option A1.2 may be beneficially chosen so that the UE may know that the DRB will be handed by the eNB_S. For option A2, before a new Scell belonging to the eNB_S is added, all current LCHs will be handled by the eNB_M by default. And when the Scell belonging to the eNB_S is setup, it should indicate which DRB will be handled by this new Scell. While when configuring/reconfiguring the Scell belonging to the eNB_M, this new information element is not needed and it is not necessary to indicate which LCH this new Scell will handle.

In addition, in R12, if the SRB is specified to be handled only by the eNB_M and the DRB is specified to be handled only by the eNB_S, then the UE only needs to know whether there is a Scell of the eNB_S is active or not. If yes, then the UE will conduct the specified behavior so that the DRB will be only handled by the eNB_S. If not, all current configured SRBs/DRBs will be handled by the eNB_M.

To let a UE know that at least one Scell belongs to the eNB_S, it can be done by adding a new information element to the Scell configuration/reconfiguration RRC message to identify whether this configured/reconfigured Scell belongs to the eNB_S or not. Alternatively, we have the following option A3' to support the C-plane and U-plane separation:

Option 3': inserting one new information element in the Scell configuration/reconfiguration RRC message to identify whether this configured/reconfigured Scell belongs to the eNB_S or not.

To sum up, options A1/A2/A3 can realize the target that one service/RB/LCH will be handled by only one cell/node to improve scheduling efficiency when supporting dual connectivity in R12. And also the C-plane and U-plane separation can be easily supported based on these options.

Figure 3 illustrates a flow chart of another method 300 for supporting dual connectivity according to the embodiments of the invention. The method 300 is directed to how to deal with the impact of Scell operation (e.g., Scell activation/de-activation/release) after guaranteeing that the data of a LCH is only handled by one cell/node, Here, the data of a LCH being handled only by one cell/node can be realized by any one of above options Al, A2, and A3. However, the invention is not limited to this, and any solution that can guarantee that the data of one LCH is only handled by one cell/node falls within the scope of the invention. The method 300 includes step 310, which achieves that the data of a LCH is only handled by a Pcell or a Scell, or is only handled by the eNB_M or the eNB_S. When guaranteeing that the data of a LCH is only handled by one cell/node, it is clear for a UE by which cell/node each RB/LCH is handled. According to the CA concept, the Pcell will always keep active, which will not impact those LCHs handled by the Pcell or by the eNB_M. While because a Scell may be de-activated/activated/released dynamically for different situations, these Scell operations will impact the LCH handled by it. The key impact to UE behavior is in the Uplink (UL) LCP procedure.

According to whether the service/RB/LCH is handled by a cell (e.g., a Pcell or a Scell) or by a node (e.g., an eNB_M or an eNB_S), Here, "handle" can also be called as "map" or "link," which means whether the processing unit of a LCH is a cell (e.g., a Pcell or a Scell) or a node (e.g., an eNB_M or an eNB_S). Hence there are two-level granularity to specify the processing unit for a LCH:

Level 1: specifying the specific cell for handling the LCH, such as the Pcell, the Scell of the eNB_M, or the Scell of the eNB_S. This can be done by option A1+ sub-option A 1.1 or option A2 or option A3 as proposed above.

Level 2: specifying the specific node for handling the LCH, such as the eNB_M or the eNB_S. This can be done by option A1+ sub-option A 1.2 or option A2 or option A3 as proposed above.

From high level perspective, regardless of the level, in R12, a new UL LCP procedure should be defined as below, which covers two cases:

Case 1: a UE conducts the R10 defined LCP procedure among LCHs handled by the eNB_M.

Case 2: a UE conducts the R10 defined LCP procedure among LCHs handled by the eNB_S.

The UE behavior is discussed as follows according to these two levels.

Level 1: LCH is mapped to one specific cell explicitly

For this level, the UE is very clear that one LCH will be handled by which cell (Pcell or eNB_M Scell or eNB_S Scell). When the Scell of the eNB_M is de-activated/released, case 1 will not be impacted, because at least the Pcell can be used. This is also inline with above proposal that does not need to assign LCHs to the Scell of the eNB_M. But when the Scell of the eNB_S is de-activated/released, the following two options can handle the LCHs assigned to the Scell: Option B l: in one embodiment, when an Scell of the eNB_S to which an LCH is mapped is de-activated or released, transmission of the LCH mapped to the Scell will be pended until the Scell is activated once again.

Option B2: in another embodiment, when an Scell of the eNB_S to which an LCH is mapped is de-activated or released, and when there is at least another active Scell of the eNB_S, the UE continues to send the data of the LCH through the active Scell, as depicted in step 320 of the method 300. And when all Scells of eNB_Ss are de-activated or released, the UE sends the data of the LCH through the eNB_M, as depicted in step 330 of the method 300. In this manner, the data of the LCH is guaranteed to have the chance to be transmitted even if its mapped Scell was de-activated.

To realize these two options, the following two schemes can be considered:

Scheme 1: the method 300 is automatically implemented by the UE according to predetermined rules;

Scheme 2: the method 300 is implemented by the UE explicitly commanded by the eNB_M.

These two schemes are discussed respectively as below.

Scheme 1 : the UE automatically operates according to predetermined rules

To realize the scheme 1, R12 needs to define new rules to guide UE behaviors as below:

New rules to support option B 1 :

Rule 1.1: the UE should pend the LCH transmissions if the LCH mapped/linked Scell is de-activated/released. Since this option is very simple, it will not be further discussed below. The drawback is that the interruption of impacted LCH transmission will occur.

New rules to support option B2:

Rule 2.1: when the LCH mapped Scell of the eNB_S is de-activated/released, and there is at least one active Scell of the eNB_S, the UE continues to send the data of the LCH through the active eNB_S .

Rule 2.2: when all Scells of eNB_Ss are de-activated, the UE continues to send the data of the LCH through the eNB_M. In addition, for the situation that the LCH mapped Scell of the eNB_S is released, Rule 2.3 may be defined as follows:

Rule 2.3: when the LCH mapped Scell of the eNB_S is released, a new information element is added to the RRC message for releasing the Scell to indicate by which cell (e.g., Pcell or Scell)/node (e.g., eNB_M or eNB_S) the LCH will be handled so as to avoid the UE confusion. In addition, it may be further defined that when the RRC message for releasing the Scell does not give this information or the added information element is empty, the UE knows that the LCH will be handled by the eNB_M.

The benefit of rules to support option B2 is to guarantee there will be no logical channel pending when the Scell of the eNB_S is becoming de-activated/released.

Specially, scheme 1 can be further simplified by the following rules to realize the C-plane and U-plane separation in R12:

Rule 2.1: given that there is at least one Scell of an eNB_S keeping active, the UE will send all DRBs through the eNB_S and will not be impacted by eNB_S Scell de-activation operation;

Rule 2.2: if all Scells of eNB_Ss are de-activated/released, the UE will start to send all DRBs through the eNB_M or pends all LCH transmissions handled by eNB_Ss.

Rule 2.3: the SRB will be sent through the eNB_M regardless of the eNB_M Scell de-activation/activation/release operation.

Scheme 2: the method 300 is implemented by the UE explicitly commanded by the eNB_M

For the scheme 2, all UE behaviors are controlled by the eNB_M. For example, when the Scell of the eNB_S is de-activated, and the eNB_S wants the UE to send the related LCH's data through the eNB_M, regardless whether there is active eNB_S Scell or not, the above new rules of scheme 1 cannot work. For this situation, the eNB_M can explicitly indicate the UE behavior by the Scell active/de-active Media Access Control (MAC) Control Element (CE).

Figure 6 illustrates a schematic diagram of the existing Scell activation/de-activation MAC CE. As illustrated in Figure 6, in the existing Scell activation/de-activation MAC CE according to 3GPP TS 36.321, there is a "R" bit which is reserved for later use. This "R" bit can be re-defined to indicate the UE behavior explicitly. Figure 7 illustrates a schematic diagram of the reconfigured Scell activation/de-activation MAC CE according to the embodiments of the invention.

As illustrated in Figure 7, "R"=0 indicates that the UE continues to send the data of impacted LCHs through the eNB_S. For this case, if the being de-activated Scell is the last one, the UE will pend the transmissions of the impacted LCHs. The reason is there is no active Scell on the eNB S and the UE is not permitted to send those impacted LCHs through the eNB_M.

As illustrated in Figure 7, "R"=l indicates that the UE may send the data of impacted LCHs through the eNB_M. For this case, regardless whether or not there is active Scell on the eNB _S, the UE will start to send data of those impacted LCHs through the eNB_M.

In addition, to realize the C-plane and U-plane separation, scheme 2 can be further defined as below:

In case that "R"=0 and there is at least one eNB_S Scell being active, the UE continues to send the DRB data through the eNB_S.

In case that "R"=0 and there is no eNB_S Scell being active, the UE will pend all DRB transmissions since the eNB_S is not permitted to send DRB through the eNB_M.

In case that "R"=l and there is at least one eNB_S Scell being active, UE will pend the impacted LCHs handled by the de-activated eNB_S Scells because the UE cannot send the DRB through the eNB_M. The reason is there is at least one eNB_S Scell that can be used and the transmission of DRB through the eNB_M is not permitted.

In case that "R"=l and there is no eNB S Scell being active, the UE continues to send all DRBs through the eNB_M.

Level 2: LCH is mapped to one node

For this level, the UE only knows by which node (e.g., eNB_M or eNB_S) one

LCH will be handled. Hence the eNB_S Scell de-activation/activation/release operation will not directly impact the UE UL LCP procedure, till the last eNB_S Scell is becoming de-activated. And the scheme 1 and the scheme 2 proposed for level 1 can be changed into the following scheme 1 ' and scheme 2' :

Scheme : the method 300 is automatically implemented by the UE according to predetermined rules, wherein the following new rules are defined: Rule : if there is at least one eNB_S Scell being active, all LCHs mapped to eNB_S are sent through eNB_S and will not be impacted by the eNB_S Scell de-activation/release operation;

Rule 2': when all eNB_S Scells are de-activated or released, the UE continues to send all LCHs mapped to eNB_S through the eNB_M temporarily so that there is no pending for the eNB S handled LCH transmission.

Scheme 2': the method 300 is implemented by the UE explicitly commanded by eNB_M.

In scheme 2', the "R" bit in the Scell activation/activation MAC CE will be defined as below:

If there is at least one eNB_S Scell being active, the "R" bit is ignored.

In case that "R=0" and all eNB_S Scells are de-activated, the UE continues to send all LCHs handled by eNB S through the eNB_M temporarily.

In case that "R=l" and all eNB_S Scells are de-activated, the UE pends all LCHs mapped to eNB_S since the eNB_S is not permitted to send its handled LCHs through the eNB_M.

Level 2 is very easy to realize the C-plane and U-plane separation.

In level 2, for scheme , new rules can be defined as below:

If there is at least one eNB_S Scell being active, the UE will continue to send all DRBs through the eNB_S.

When all eNB_S Scells are de-activated, the UE continues to send all DRBs through the eNB_M.

In level 2, for scheme 2', the "R" bit can be redefined as below:

If there is at least one eNB_S Scell being active, the "R" bit is ignored and the UE continues to send all DRBs through the eNB_S.

In case that "R"=0 and all eNB_S Scells are de-activated, the UE continues to send all DRBs through the eNB_M temporarily.

In case that "R"=l and all eNB_S Scells are de-activated, the UE pends all DRB transmissions since the eNB_S is not permitted to send DRBs through the eNB_M. Figure 4 illustrates a block diagram of an apparatus 400 for supporting dual connectivity according to the embodiments of the invention. The apparatus 400 can be implemented in the eNB_M or can be implemented by the eNB_M. As illustrated in Figure 4, the apparatus 400 includes an initialization unit 410, which is configured to, when a UE initially access to the eNB_M, connect the UE to a Pcell or the eNB_M such that current LCH is handled by the Pcell or the eNB_M. The apparatus 400 also includes an indication unit 420, which is configured to indicate to the UE through a dedicated RRC message that the LCH is to be handled by the eNB_M or an eNB_S, or is to be handled by the Pcell or a Scell.

Figure 5 illustrates a block diagram of another apparatus 500 for supporting dual connectivity according to the embodiments of the invention. The apparatus 500, for example, can be implemented in the eNB_M or can be implemented by the eNB_M. As illustrated in Figure 5, the apparatus 500 includes a dual connectivity enabling unit 510, which is configured to make the data of a LCH only be handled by a Pcell or a Scell, or only be handled by an eNB_M or an eNB_S. The apparatus 500 also includes a cell change processing unit 520, which is configured to, when the LCH mapped Scell of the eNB_S is de-activated or released, and when there is at least another one active Scell of the eNB_S, send the data of the LCH through the active eNB_S, and the cell change processing unit 520 is further configured to, when all Scells of eNB_Ss are de-activated or released, send the data of the LCH through the eNB_M.

In this disclosure, according to the context of a term used, the term "base station" can refers to the coverage of a base station and/or a base station or a base station subsystem serving the coverage.

In addition, in this disclosure, as stated about the method 300, the definition of "R" bit is merely an illustrative description. Those of ordinary skill in the art can easily make an opposite definition or other different definitions, as long as it can explicitly indicate the behavior of a UE.

Utilizing the dual connectivity schemes based on carrier aggregation proposed in this invention, the small cell scheduling efficiency can be improved and the separation of C-plane and U-plane can be achieved.

Here, the method as disclosed has been described with reference to the accompanying drawings. However, it should be appreciated that the sequence of the steps as illustrated in the figures and described in the description are only illustrative, and without departing from the scope of the claims, these method steps and/or actions may be executed in a different sequence, without being limited to the specific sequence as shown in the drawings and described in the description.

In one or more exemplary designs, the functions of the present application may be implemented using hardware, software, firmware, or any combinations thereof. In the case of implementation with software, the functions may be stored on a computer readable medium as one or more instructions or codes, or transmitted as one or more instructions or codes on the computer readable medium. The computer readable medium comprises a computer storage medium and a communication medium. The communication medium includes any medium that facilitates transmission of the computer program from one place to another. The storage medium may be any available medium accessible to a general or specific computer. The computer-readable medium may include, for example, but not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disc storage devices, magnetic disk storage devices, or other magnetic storage devices, or any other medium that carries or stores desired program code means in a manner of instructions or data structures accessible by a general or specific computer or a general or specific processor. Furthermore, any connection may also be considered as a computer-readable medium. For example, if software is transmitted from a website, server or other remote source using a co-axial cable, an optical cable, a twisted pair wire, a digital subscriber line (DSL), or radio technologies such as infrared, radio or microwave, then the co-axial cable, optical cable, twisted pair wire, digital subscriber line (DSL), or radio technologies such as infrared, radio or microwave are also covered by the definition of medium.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any normal processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

The above depiction of the present disclosure is to enable any of those skilled in the art to implement or use the present invention. For those skilled in the art, various modifications of the present disclosure are obvious, and the general principle defined herein may also be applied to other transformations without departing from the spirit and protection scope of the present invention. Thus, the present invention is not limited to the examples and designs as described herein, but should be consistent with the broadest scope of the principle and novel characteristics of the present disclosure.

Claims

WE CLAIM:

1. A method for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations, the method comprising:

an initialization step for, when a User Equipment (UE) initially accesses the macro base station, connecting the UE to a Primary Cell (Pcell) or the macro base station such that a current Logical Channel (LCH) is handled by the Pcell or the macro base station, wherein the Pcell is associated with the macro base station and operates on a primary component carrier; and

an indication step for indicating to the UE through a dedicated Radio Resource Control (RRC) message that the LCH is to be handled by the macro base station or one of the small cell base stations, or is to be handled by the Pcell or a Secondary Cell (Scell), wherein the Scell operates on a secondary component carrier.

2. The method according to claim 1, wherein the RRC message is a RRC message for Radio Bearer (RB) configuration/reconfiguration, and the indication step includes adding a new information element to the RRC message to indicate that the RB is to be handled by the Pcell or the Scell, or to indicate that the RB is to be handled by the macro base station or the small cell base station.

3. The method according to claim 2, wherein the information element being empty indicates that the RB is to be handled by the Pcell, or indicates that the RB is to be handled by the macro base station.

4. The method according to claim 1, wherein the RRC message is a RRC message for Scell configuration/reconfiguration, and the indication step includes, when configuring/reconfiguring a Scell, adding a new information element to the RRC message to indicate to the UE a RB/LCH to be handled by the configured/reconfigured Scell.

5. The method according to claim 4, wherein the indication step includes, when configuring/reconfiguring the RB/LCH, updating the RB/LCH configuration/reconfiguration message to add a new information element to indicate that the configured/reconfigured RB/LCH is to be handled by the Pcell or the Scell.

6. The method according to claim 4, wherein the indication step includes, when configuring/reconfiguring the RB/LCH, using the Scell configuration/reconfiguration RRC message to indicate to the UE that the configured/reconfigured RB/LCH is to be handled by the macro base station or the small cell base station.

7. The method according to claim 1, wherein the indication step includes defining a new dedicated RRC message to indicate the Pcell or the Scell for handling each RB/LCH, or to indicate the macro base station or the small cell base station for handling each RB/LCH.

8. The method according to claim 1, wherein the RRC message includes a RRC message for Scell configuration/reconfiguration, wherein the indication step includes inserting a new information element to the RRC message to indicate whether the Scell belongs to a small cell base station or not.

9. The method according to claim 1, further comprising:

when the LCH mapped Scell of the small cell base station is de-activated or released, and when there is at least another active Scell of the small cell base station in the wireless communication network, sending data of the LCH through the active small cell base station; and when all the Scells of small cell base stations are de-activated or released, sending data of the LCH through the macro base station.

10. A method for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations, the method comprising:

having data of a Logical Channel (LCH) to only be handled by a Primary Cell (Pcell) or a Secondary Cell (Scell), or to only be handled by the macro base station or one of the small cell base stations;

11. The method according to claim 10, wherein the method is implemented by a UE according to predefined rules.

12. The method according to claim 10, wherein when the LCH mapped Scell of the small cell base station is released, adding a new information element to the RRC message for releasing the Scell to indicate that the LCH is to be handled by the Pcell or the Scell, or to indicate that the LCH is to be handled by the macro base station or one of the small cell base stations.

13. A method for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations, the method comprising:

having data of a Logical Channel (LCH) to only be handled by a Primary Cell (Pcell) or a Secondary Cell (Scell), or to only be handled by the macro base station or one of the small cell base stations; and

when the LCH mapped Scell of the small cell base station is de-activated, pending transmission of the LCH until the Scell is re-activated.

14. A method for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations, the method comprising:

when the Scell of the small cell base station is de-activated, the macro base station indicating a UE behavior by setting "R" bit in the Scell activation/de-activation MAC CE.

15. The method according to claim 14, wherein "R"=0 indicates that the UE continues to send data of the LCH impacted by the deactivation of Scell through the small cell base station, and "R"=l indicates that the UE sends data of the LCH impacted by the deactivation of Scell through the macro base station.

16. The method according to claim 14, wherein when "R"=0 and there is at least one Scell of the small cell base station being active, indicating the UE to continue to send Data Radio Bearer (DRB) data through the small cell base station; when "R"=0 and there is no Scells of the small cell base stations being active, indicating the UE to pend all DRB transmissions; when "R"=l and there is at least one Scell of the small cell base station being active, indicating the UE to pend the LCH handled by the de-activated Scell of the small cell base station; and when "R"=l and there is no Scells of the small cell base stations being active, indicating the UE to continue to send all DRBs through the macro base station.

17. The method according to claim 14, wherein the "R" bit is to be ignored if there is at least one Scell of the small cell base station keeping active; when "R=0" and all Scells of the small cell base stations are inactive, the UE continues to send all LCHs handled by small cell base stations through the macro base station; when "R=l" and all Scells of small cell base stations are inactive, the UE pends all LCHs mapped to the small cell base stations.

18. An apparatus for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations, the apparatus comprising:

an initialization unit, which is configured to, when a User Equipment (UE) initially accesses to the macro base station, connect the UE to a Primary Cell (Pcell) or the macro base station such that a current Logical Channel (LCH) is handled by the Pcell or the macro base station, wherein the Pcell is associated with the macro base station and operates on a primary component carrier; and

an indication unit, which is configured to indicate to the UE through a dedicated Radio Resource Control (RRC) message that the LCH is to be handled by the macro base station or a small cell base station, or is to be handled by the Pcell or a Secondary Cell (Scell), wherein the Scell operates on a secondary component carrier.

19. An apparatus for supporting dual connectivity in a wireless communication network including one macro base station and one or more small cell base stations, the apparatus comprising:

a dual connectivity enabling unit, which is configured to have data of a Logical Channel (LCH) to only be handled by a Primary Cell (Pcell) or a Secondary Cell (Scell), or to only be handled by the macro base station or one of the small cell base stations; and

a cell change processing unit, which is configured to, when the LCH mapped Scell of the small cell base station is de-activated or released, and when there is at least another active Scell of the small cell base station in the wireless communication network, send data of the LCH through the active small cell base station; and wherein the processing unit is further configured to, when all Scells of the small cell base stations are de-activated or released, send data of the LCH through the macro base station.