Field of the invention

The present invention relates to the wireless communication technology, and particularly to a method for supporting dual connectivity in the master eNB, the secondary eNB and user equipment of a carrier aggregation based wireless communication network.

Background of the invention

Nowadays, there are master eNBs with a relative large coverage and secondary eNBs with a relative smaller coverage which are simultaneously deployed in the wireless communication network. Fig. l illustrates a schematic diagram 100 of a network architecture in the prior art, and as can be apparent, in such a network environment, a master eNB 110 provides underlying network coverage (as illustrated by a dotted background in the figure), and in the meantime, for example, secondary eNBs 121 , 122, 123 and 124 at small power (that is, with small network coverage (areas illustrated by oblique lines in the figure) provide a possible network access at a higher speed. At this time, the UE 130 in the overlapped coverage may communicate with the master eNB and the secondary eNB simultaneously, and then how to utilize the resources of the master eNB or the secondary eNB for communication, namely how to efficiently realize the scheduling is very important for reaching an optimized and maximal utilization of the UE and the two types of eNBs.

Typically, the master eNB is used as a Pcell and the secondary eNB is used as a small cell Scell, such a configuration is advantageous for mobility management. At this time, the UE in the overlapped coverage may communicate with the master eNB and the secondary eNB simultaneously, but the master eNB and the secondary eNB are connected with each other via the non-ideal backhaul network which is not beneficial for the scheduling optimization.

For the downlink, how to buffer the data is important for how to distribute the data. If the distribution is accomplished at the core network, then the downlink data for the secondary eNB is sent from the core network to the secondary eNB and the secondary eNB will buffer the downlink transmission. Otherwise, the distribution scheme will be achieved at the level of access network, the data is possibly forwarded from the master eNB to the secondary eNB for downlink transmission.

For the uplink, the user equipment UE will get the uplink scheduling grant and then the uplink packet such as RRC signaling will be sent to the master eNB and the other part such as data packet will be sent to the secondary eNB. Then the secondary eNB will forward the received packet to the master eNB via the non-ideal backhaul network or send it to the core network directly.

Consequently, how to perform scheduling is very important for supporting the dual connectivity. For the downlink, the macro station should control the scheduling of the master eNB and the secondary eNB if buffering is done by the master eNB. It is totally correct for the downlink grant scheduling of the master eNB itself, however, the following problems will occur when the master eNB controls the downlink grant scheduling of the secondary eNB:

- The master eNB is not aware of the load situation of the secondary eNB, and thus cannot perform the scheduling operation efficiently;

- For LTE-A, scheduling related information is mainly the CSI information received from the UE. According to the concept of the carrier aggregation in the prior art, CSI can be sent on PUCCH or PUSCH. For the former, the master eNB will receive the CSI information of the secondary eNB. For the later, CSI information is possibly received by the secondary eNB and there is yet not any CSI information exchange mechanism between the master eNB and the secondary eNB.

The two problems mentioned above will induce that the master eNB cannot perform an efficient scheduling of the secondary eNB.

In the meanwhile, for the uplink related information, such as BSR or PHR information, it is not prescribed about how to send BSR and PHR based on the concept of the carrier aggregation in the prior art. They may be transmitted on any active uplink carrier component. Therefore, the BSR and PHR may be received by the master eNB or the secondary eNB, as mentioned in the foregoing, there is not any X2 signaling for exchanging these information. mary of the invention

In view of the prior art and the technical problem thereof identified as above, a first aspect of the invention proposes a method for supporting dual connectivity in a master eNB of a carrier aggregation based wireless communication system, the method comprising the following step:

- the master eNB receiving scheduling related scheduling information from a secondary eNB or a user equipment, or sending scheduling related scheduling information to a secondary eNB.

In such a manner, the scheduling information may be exchanged between the master eNB and the secondary eNB or received by the UE, such that the subsequent scheduling optimization is possible. The master eNB using the method according to the present invention may obtain the required scheduling information in time, such that the master eNB may realize a scheduling optimization and thus the communication performance of the whole wireless communication network is improved.

In one embodiment of the present invention, the secondary eNB manages one or more small cells, the method further comprises the following steps:

- sending control signaling to the user equipment, the control signaling indicating to add a small cell for the user equipment;

- receiving a first confirmation message from the user equipment in response to the control signaling; - sending a first indication message to the secondary eNB, the first indication message indicating that the master eNB has added the small cell for the user equipment; and

- receiving a second confirmation message from the secondary eNB in response to the first indication message.

Those skilled in the art should understand that the above mentioned steps are only one possible way to establish dual connectivity. It is also proper that the secondary eNB may send dual connectivity establishing indication or other dual connectivity establishing ways are also proper.

In one embodiment of the present invention, the master eNB receives the scheduling related scheduling information from the secondary eNB or sends the scheduling related scheduling information to the secondary eNB via X2 signaling when the master eNB receives the scheduling related scheduling information from the secondary eNB or sends the scheduling related scheduling information to the secondary eNB .

In such a manner, the secondary eNB may forward the scheduling information to the master eNB in time. Advantageously, the secondary eNB will forward the scheduling information to the master eNB without any delay.

In one embodiment of the present invention, the X2 signaling includes:

- user equipment identifier;

- small cell index; and at least one of:

- uplink BSR information; and

- downlink channel status information.

Those skilled in the art should understand that the content of the X2 signaling may be changed depending on the transmitted scheduling information, so as to achieve the forwarding of the scheduling information.

In one embodiment of the present invention, the user equipment only sends the scheduling related scheduling information to the master eNB when the master eNB receives the scheduling related scheduling information from the user equipment. In such a manner, the scheduling may be controlled by the master eNB .

In one embodiment of the present invention, for the uplink BSR or the uplink PHR, the user equipment only selects an active uplink carrier component controlled by the master eNB to send the scheduling information. In such a manner, it is ensured that the master eNB may receive the uplink BSR and uplink PHR information.

In one embodiment of the present invention, if the downlink CQI feedback is transmitted on PUSCH, the user equipment selects a small cell to send the scheduling information according to a predetermined rule. The predetermined rule here may be that the scheduling information is sent by the small cell managed by the master eNB which has the smallest small cell index. Those skilled in the art should understand that the predetermined rule may be any other proper rules.

The second aspect of the present invention provides a method for supporting dual connectivity in a secondary eNB of a carrier aggregation based wireless communication system, the method comprises the following steps:

- the secondary eNB receiving scheduling related scheduling information from a master eNB or a user equipment, or sending scheduling related scheduling information to the master eNB.

The secondary eNB using the method for supporting dual connectivity in a secondary eNB will efficiently cooperate with the master eNB to optimize the scheduling.

In one embodiment of the present invention, the secondary eNB manages one or more small cells, the method further comprises the following steps:

- receiving a first indication message from the master eNB, the first indication message indicates that the master eNB has added the small cell for the user equipment; and - sending a second confirmation message to the master eNB in response to the first indication message.

Those skilled in the art should understand that the above mentioned steps are only one alternative way; other proper ways are also possible.

In one embodiment of the present invention, the secondary eNB sends the scheduling related scheduling information to the master eNB via X2 signaling periodically or in response to a first request instruction sent from the master eNB.

In one embodiment of the present invention, the method further comprises the following steps:

- the secondary eNB sending a second indication information indicating the load situation of a small cell to the secondary eNB via X2 signaling periodically or in response to a second request instruction sent from the master eNB.

In one embodiment of the present invention, when the secondary eNB sends a second indication information indicating the load situation of a small cell to the secondary eNB via X2 signaling periodically or in response to a second request instruction sent from the master eNB, the secondary eNB sends a second indication information indicating the load situation of a small cell to the secondary eNB via X2 signaling periodically or in response to a second request instruction sent from the master eNB only when the load situation of the secondary eNB exceeds a first threshold. In such a manner, the network scheduling is further improved. Specifically, if the load situation of the secondary eNB is low for example lower than the first threshold, then the master eNB may schedule well even if the master eNB is not aware of the load situation of the secondary eNB. Therefore, it is not needed to transmit the load situation of the secondary eNB to the master eNB in this case. In contrary, if the load situation of the secondary eNB is high for example higher than the first threshold, then the master eNB must consider the load situation of the secondary eNB, at this time the load situation of the secondary eNB is needed to be transmitted to the master eNB.

In one embodiment of the present invention, the second indication information includes user equipment identifier and cell index.

The third aspect of the present invention provides a method for supporting dual connectivity in a user equipment of a carrier aggregation based wireless communication system, wherein the user equipment sends scheduling related scheduling information to a master eNB and a secondary eNB, respectively. Brief description of drawings

Other features, objects and advantages of the invention will become more apparent upon review of the following detailed description of non-limiting embodiments taken with reference to the drawings in which:

Fig. l illustrates the schematic diagram 100 of the network architecture in the prior art; and

Fig.2 illustrates a flow diagram of a method for supporting dual connectivity in a master eNB of a carrier aggregation based wireless communication system; and

Fig. 3 illustrates a flow diagram of a method for supporting dual connectivity in a secondary eNB of a carrier aggregation based wireless communication system.

Identical or similar devices (modules) or steps will be denoted by identical or similar reference numerals throughout the drawings. Detailed description of embodiments

The following described particular description of preferred embodiments will be given with reference to the drawings constituting a part of the invention. The drawings exemplarily illustrate particular embodiments, in which the invention can be practiced. The exemplary embodiments are not intended to exhaust all the embodiments of the invention. As can be appreciated, other embodiments can be possible or structural or logical modifications can be made without departing from the scope of the invention. Thus the following detailed description is not intended to be limiting, and the scope of the invention will be defined as in the appended claims.

Fig. l illustrates the schematic diagram 100 of the network architecture in the prior art, and this figure has been described in the section "Background of the invention", so a repeated description thereof will be omitted here.

Fig. 2 illustrates a method for supporting dual connectivity in a master eNB of a carrier aggregation based wireless communication system, as can be apparent from Fig. 2, the method comprises the following steps:

At first, the following operations will be done in steps 210 and 220:

- sending control signaling to the user equipment, the control signaling indicates to add a small cell for the user equipment;

- receiving a first confirmation message from the user equipment in response to the control signaling.

Then, the following operations will be done in steps 230 and 240:

- sending a first indication message to the secondary eNB, the first indication message indicating that the master eNB has added the small cell for the user equipment; and

- receiving a second confirmation message from the secondary eNB in response to the first indication message.

Up to now, the dual connectivity has been established. However, those skilled in the art should understand that the above mentioned steps are only one possible way to establish dual connectivity. It is also proper that the secondary eNB may send dual connectivity establishing indication or other dual connectivity establishing ways are also proper.

At last, the master eNB receives scheduling related scheduling information from a secondary eNB or user equipment, or sends scheduling related scheduling information to a secondary eNB, wherein the secondary eNB manages one or more small cells. In such a manner, the scheduling information may be exchanged between the master eNB and the secondary eNB or received by the UE, such that the subsequent scheduling optimization is possible. The master eNB using the method according to the present invention may obtain the required scheduling information in time, such that the master eNB may realize a scheduling optimization and thus the communication performance of the whole wireless communication network is improved.

The master eNB here may sends the scheduling related scheduling information to the secondary eNB, such that the secondary eNB may obtain other information required by scheduling in addition to the load situation itself, and thus the secondary eNB may achieve the scheduling of itself.

Optionally, the master eNB receives the scheduling related scheduling information from the secondary eNB or sends the scheduling related scheduling information to the secondary eNB via X2 signaling when the master eNB receives the scheduling related scheduling information from the secondary eNB or sends the scheduling related scheduling information to the secondary eNB. For example, the secondary eNB may forward the uplink BSR information, the downlink CSI information received by the secondary eNB to the master eNB without any delay, and thus the master eNB may obtain the latest information in time to do the scheduling. At this time, the X2 signaling needs to be defined, so as to ensure that the secondary eNB may forward the uplink BSR information, the downlink CSI information and PHR information received by the secondary eNB to the corresponding master eNB.

In one embodiment of the present invention, the X2 signaling includes:

- user equipment identifier;

- small cell index; and at least one of:

- uplink BSR information; and

- downlink channel status information. Those skilled in the art should understand that the content of the X2 signaling may be changed depending on the transmitted scheduling information, so as to achieve the forwarding of the scheduling information. The X2 signaling for different scheduling information may also contain different content. For example, when the scheduling information relates to an X2 signaling for forwarding the uplink BSR information, the X2 signaling must include the following portions:

UE identifier for indicating the master eNB that from which user equipment the uplink BSR information comes.

In the meanwhile, when the scheduling information relates to an X2 signaling for forwarding the downlink CSI/PHR information, the X2 signaling must include the following information:

UE identifier and the CSI information;

Small cell index for indicating the master eNB that for which small cell the CSI/PHR information is used. For example, if the CSI/PHR information is used for the master eNB, then the small cell index should be "000".

In such a manner, the secondary eNB may forward the scheduling information to the master eNB in time. Advantageously, the secondary eNB will forward the scheduling information to the master eNB without any delay.

The advantage of such a forward mechanism is that the current carrier aggregation specification regarding the BSR/PHR/CSI information transmission does not need to be updated, and thus such a mechanism only needs to define an X2 signaling and does not have any negative influence to the physical layer standards.

The above goal may achieved by defining a new BSR/PHR/CSI information transmission rule. In particular, in one embodiment of the present invention, the user equipment only sends the scheduling related scheduling information to the master eNB when the master eNB receives the scheduling related scheduling information from the user equipment. In such a manner, the scheduling may be controlled by the master eNB. For the uplink BSR or the uplink PHR, the user equipment only selects an active uplink carrier component controlled by the master eNB to send the scheduling information. In such a manner, it is ensured that the master eNB may receive the uplink BSR and uplink PHR information. Accordingly, if the downlink CQI feedback is transmitted on PUSCH, the user equipment selects a small cell to send the scheduling information according to a predetermined rule. The predetermined rule here may be that the scheduling information is sent by the small cell managed by the master eNB which has the smallest small cell index. Those skilled in the art should understand that the predetermined rule may be any other proper rules.

The above mentioned scheme may be used together with the rules of the user equipment, so as to ensure that the uplink BSR/PHR information and CSI information are only available at the master eNB, it is important for the master eNB to achieve the scheduling.

For the small cell controlled by the secondary eNB, the present invention provides a method for supporting dual connectivity in a secondary eNB of a carrier aggregation based wireless communication system, the method comprising the following steps:

At first, the following operations will be done in steps 310 and 320: receiving a first indication message from the secondary eNB, the first indication message indicates that the master eNB has added a small cell for the user equipment; and

sending a second confirmation message to the master eNB in response to the first indication message.

The secondary eNB manages one or more small cells.

Those skilled in the art should understand that the above mentioned steps are only one alternative way; other proper ways are also possible.

Then, in the step 330, the secondary eNB receives scheduling related scheduling information from a master eNB sends scheduling related scheduling information to the master eNB .

The secondary eNB using the method for supporting dual connectivity in a secondary eNB will efficiently cooperate with the master eNB to optimize the scheduling.

In one embodiment of the present invention, the secondary eNB sends the scheduling related scheduling information to the master eNB via X2 signaling periodically or in response to a first request instruction sent from the master eNB.

In one embodiment of the present invention, the method further comprises the following steps:

- the secondary eNB sends a second indication information indicating the load situation of a small cell to the secondary eNB via X2 signaling periodically or in response to a second request instruction sent from the master eNB.

In such a manner, the secondary eNB may send the load situation to the master eNB to optimize the scheduling of the master eNB.

In one embodiment of the present invention, when the secondary eNB sends a second indication information indicating the load situation of a small cell to the secondary eNB via X2 signaling periodically or in response to a second request instruction sent from the master eNB, the secondary eNB sends a second indication information indicating the load situation of a small cell to the secondary eNB via X2 signaling periodically or in response to a second request instruction sent from the master eNB only when the load situation of the secondary eNB exceeds a first threshold. In such a manner, the network scheduling is further improved. Specifically, if the load situation of the secondary eNB is low for example lower than a first threshold, then the master eNB may schedule well even if the master eNB is not aware of the load situation of the secondary eNB. Therefore, it is not needed to transmit the load situation of the secondary eNB to the master eNB in this case. In contrary, if the load situation of the secondary eNB is high for example higher than the first threshold, then the master eNB must consider the load situation of the secondary eNB, at this time the load situation of the secondary eNB is needed to be transmitted to the master eNB.

In one embodiment of the present invention, the second indication information includes user equipment identifier and cell index.

The present invention further provides a method for supporting dual connectivity in a user equipment of a carrier aggregation based wireless communication system, wherein the user equipment sends scheduling related scheduling information to a master eNB and a secondary eNB, respectively. As a result, both of the master eNB and the secondary eNB obtain the scheduling related scheduling information.

Specifically, assume that a logical channel is only controlled by one transmission point, the user equipment can transmit the uplink BSR information of the logical channel controlled by the master eNB on the uplink carrier component of the master eNB; accordingly, the user equipment can transmit the uplink BSR information of the logical channel controlled by the secondary eNB on the uplink carrier component of the secondary eNB. In contrary, if the above assumption does not hold, the user equipment may send the uplink BSR information to the master eNB and the secondary eNB simultaneously, such that the master eNB and the secondary eNB are aware of the related information as early as possible. The uplink PHR information of the uplink carrier component for the master eNB will be transmitted on the cell controlled by the master eNB and the uplink PHR information of the uplink carrier component for the secondary eNB will be transmitted on the cell controlled by the secondary eNB; the downlink CSI information of the downlink carrier component for the master eNB will be transmitted on the cell controlled by the master eNB and the downlink CSI information of the downlink carrier component for the secondary eNB will be transmitted on the cell controlled by the secondary eNB.

Those skilled in the art shall appreciate that the invention apparently will not be limited to the foregoing exemplary embodiments and can be embodied in other specific forms without departing from the spirit or essence of the invention. Accordingly the embodiments shall be construed anyway to be exemplary and non-limiting. Moreover apparently the term "comprising" will not preclude another element(s) or step(s), and the term "a" or "an" will not preclude plural. A plurality of elements stated in an apparatus claim can alternatively be embodied as a single element. The terms "first", "second", etc., are intended to designate a name but not to suggest any specific order.