WO2014181180A2 - Method of splitting data to a secondary base station - Google Patents

Method of splitting data to a secondary base station Download PDF

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Publication number
WO2014181180A2
WO2014181180A2 PCT/IB2014/001060 IB2014001060W WO2014181180A2 WO 2014181180 A2 WO2014181180 A2 WO 2014181180A2 IB 2014001060 W IB2014001060 W IB 2014001060W WO 2014181180 A2 WO2014181180 A2 WO 2014181180A2
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WO
WIPO (PCT)
Prior art keywords
base station
secondary base
data
user equipment
indication message
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PCT/IB2014/001060
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French (fr)
Other versions
WO2014181180A3 (en
Inventor
Tao Yang
Chongxian Zhong
Fanglei Sun
Original Assignee
Alcatel Lucent
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Publication date
Application filed by Alcatel Lucent filed Critical Alcatel Lucent
Publication of WO2014181180A2 publication Critical patent/WO2014181180A2/en
Publication of WO2014181180A3 publication Critical patent/WO2014181180A3/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/15—Setup of multiple wireless link connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/30—Connection release
    • H04W76/34—Selective release of ongoing connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/04—Large scale networks; Deep hierarchical networks
    • H04W84/042—Public Land Mobile systems, e.g. cellular systems
    • H04W84/045—Public Land Mobile systems, e.g. cellular systems using private Base Stations, e.g. femto Base Stations, home Node B

Definitions

  • the present disclosure relates to communication technology and particularly to a method of splitting data to a secondary base station in a carrier aggregation based communication system, a method of ending splitting data to a secondary base station in a carrier aggregation based communication system, and a method of processing data, which is buffered in a secondary base station due to release of a small cell, in a carrier aggregation based communication system.
  • the new R12 Study Item(SI) on Small cell enhancement-high layer has been approved in RAN 58.
  • SI small cell enhancement-high layer
  • One important objective of this SI is on "dual connectivity" research and realization. This refers to situation that UE keeps communication with at least two base stations at the same time, which are connected by non-ideal backhaul. And this is the key difference to Rl l CA (carrier aggregation) scenario.
  • UP data splitting is on UP data splitting.
  • the UP split scheme can be classified into two schemes: in core network or in RAN level. Regardless CN or RAN level UP splitting, the key issue is how to split data to small cell for DL transmission. And the following two options can be considered:
  • Option 1 scheduling decision triggered data forwarding
  • Option 2 Non- scheduling triggered forwarding.
  • the first option refers to situation that after scheduling decision, the amount of data determined by the scheduling grant is split to small cells for DL Tx. Hence there should no source data buffered in small cells since all split data will be sent down in one TTI. While for the later, the data is split to small cells by some kind of flow control functionality, which is either located in CN or in primary cell. After scheduling decision, these buffered source data will be sent down in small cells. Hence it is clear that there always will be source data buffered in small cells, which is the key difference to the first option.
  • Option 1 may be linked to MAC layer splitting scheme while option 2 is related to other RAN level and CN level UP splitting scheme. Since MAC layer splitting scheme would produce non-backhaul effect, the present invention will only focus on option 2 where data splitting is controlled by flow-control functionality, either located in CN or the primary cell.
  • a method, in a primary base station, of supporting splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells comprising:- sending a control signaling to a user equipment, the control signaling indicating that a small cell is added for the user equipment;- receiving a confirmation message from the user equipment in response to the control signaling;- sending a first indication message to the secondary base station, the first indication message indicating that the primary base station added the small cell for the user equipment; and - sending a second indication message to a core network, the second indication message indicating the core network to split the data to the secondary base station; or splitting the data to the secondary base station.
  • a method, in a secondary base station, of supporting splitting data to the secondary base station in a carrier aggregation based communication system wherein the secondary base station serves one or more small cells, the method comprising: - receiving a first indication message from a primary base station, the first indication message indicating that the primary base station added a small cell for a user equipment; and- sending a third indication message to a core network, the third indication message indicating the core network to split the data to the secondary base station, and receiving data from the core network; or receiving data from a core network; or receiving data from the primary base station.
  • a method, in a primary base station, of supporting splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells comprising:- determining a small cell to be activated for a user equipment, and sending a first notification to the secondary base station, the first notification indicating the secondary base station to activate the determined small cell; - sending a first controlling signaling to the user equipment, the first controlling signaling indicating the small cell activated for the user equipment;- receiving a first confirmation message from the user equipment in response to the first controlling signaling;- forwarding the first confirmation message to the secondary base station; and - sending a first indication message to a core network, the first indication message indicating the core network to split the data to the secondary base station; or splitting the data to the secondary base station.
  • a method, in a secondary base station, of supporting splitting data to the secondary base station in a carrier aggregation based communication system wherein the secondary base station serves one or more small cells, the method comprising:- receiving a first notification from a primary base station, the first notification indicating the secondary base station the small cell needed to be activated for a user equipment determined by the primary base station, and activating the small cell according to the first notification;- receiving a first confirmation message from the primary base station, the first confirmation message indicating that the user equipment confirmed that the small cell had been activated for it; and- sending a second indication message to a core network, the second indication message indicating the core network to split the data to the secondary base station, and receiving data from the core network; or receiving data from a core network; or receiving data from the primary base station.
  • a method, in a secondary base station, of supporting splitting data to the secondary base station in a carrier aggregation based communication system wherein the secondary base station serves one or more small cells, the method comprising:- sending a first controlling signaling to a user equipment, the first controlling signaling indicating that a small cell is activated for a user equipment;- receiving a confirmation message from the user equipment in response to the control signaling;- sending an indication message to a primary base station for requesting data split, and receiving data from the primary base station; or sending an indication message to a core network for requesting data split, and receiving data from the core network.
  • a method in a primary base station or a core network, of supporting splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising: - receiving an indication message from the secondary base station, the indication message requesting to split the data to the secondary base station; and- splitting the data to the secondary base station according to the indication message.
  • a method, in a secondary base station, of supporting stopping splitting data to the secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells comprising:- sending a control signaling to a user equipment, the control signaling indicating that one small cell is released for the user equipment;- receiving a first confirmation message from the user equipment in response to the control signaling;- sending an indication message to a primary base station, the indication message indicating the primary base station to end splitting data to the secondary base station; or sending an indication message to a core network, the indication message indicating the core network to end splitting the data to the secondary base station.
  • a method in a primary base station or a core network, of supporting ending splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising: - receiving an indication message from the secondary base station, the indication message indicating ending splitting the data to the secondary base station; and- ending forwarding the data to the secondary base station according to the indication message.
  • a method, in a primary base station, of supporting ending splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells comprising:- sending a control signaling to a user equipment, the control signaling indicating that one small cell is released for the user equipment;- receiving a first confirmation message from the user equipment in response to the control signaling;- forwarding the first confirmation message to the secondary base station; and- ending splitting the data to the secondary base station; or sending a first indication message to a core network, the first indication message indicating the core network to end splitting the data to the secondary base station.
  • a method, in a secondary base station, of supporting ending splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells comprising:- receiving a first confirmation message from a primary base station, the first confirmation message indicating that the user equipment confirmed that the small cell had been released for it; and- sending a second indication message to a core network, the second confirmation message indicating the core network to end splitting the data to the secondary base station.
  • a method, in a primary base station, of supporting forwarding data to the primary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, and the data is buffered in the secondary base station due to release of a small cell comprising:- sending a control signaling to a user equipment, the control signaling indicating that a small cell is released for the user equipment;- receiving a first confirmation message from the user equipment in response to the control signaling;- forwarding the first confirmation message to the secondary base station;- receiving an indication message from the secondary base station, the indication message indicating that the secondary base station will perform data forwarding;- receiving the data from the secondary base station or a core network; and- receiving an ending message from the secondary base station, the ending message indicating that the data forwarding is ended.
  • a method, in a secondary base station, of processing data, which is buffered in the secondary base station due to release of a small cell, in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells comprising:- discarding the data; or- forwarding the data, which further comprises the following steps: - receiving a first confirmation message from a primary base station, the first confirmation message indicating that a user equipment confirmed that the small cell had been released for it; - sending an indication message to the primary base station or a core network, the indication message indicating that the secondary base station will perform data forwarding; - forwarding the data to the primary base station or the core network; and - sending an ending message to the primary base station or the core network, the ending message indicating that the data forwarding is ended.
  • a seventh aspect of the invention there is proposed a method, in a secondary base station, of processing data, which is buffered in the secondary base station due to release of a small cell, in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:- discarding the data; or- forwarding the data, which further comprises the following steps: - sending a control signaling to a user equipment, the control signaling indicating that a small cell is released for the user equipment; - receiving a first confirmation message from the user equipment in response to the control signaling; - sending an indication message to the primary base station or a core network, the indication message indicating that the secondary base station will perform data forwarding; - forwarding the data to the primary base station or the core network; and - sending an ending message to the primary base station or the core network, the ending message indicating that the data forwarding is ended.
  • a method, in a primary base station, of supporting forwarding data to the primary base station in a carrier aggregation based communication system wherein the secondary base station serves one or more small cells, and the data is buffered in the secondary base station due to release of a small cell, the method comprising:- receiving an indication message from the secondary base station, the indication message indicating that the secondary base station will perform data forwarding;- receiving the data from the secondary base station or a core network; and- receiving an ending message from the secondary base station, the ending message indicating the data forwarding is ended.
  • Fig. l illustrates a flow chart of a method of splitting data to a secondary base station according to one embodiment of the present invention
  • Fig.2 illustrates a flow chart of a method of splitting data to a secondary base station according to another embodiment of the present invention
  • Fig.3 illustrates a flow chart of a method of splitting data to a secondary base station according to a further embodiment of the present invention
  • Fig.4 illustrates a flow chart of a method of ending splitting data to a secondary base station according to one embodiment of the present invention
  • Fig.5 illustrates a flow chart of a method of ending splitting data to a secondary base station according to another embodiment of the present invention
  • Fig. 6 illustrates a flow chart of a method of pending splitting data to a secondary base station according to another embodiment of the present invention
  • Fig. 7 illustrates a flow chart of a method of pending splitting data to a secondary base station according to a further embodiment of the present invention
  • Fig. 8 illustrates a flow chart of processing data, which is buffered in the secondary base station due to release of a small cell according to a further embodiment of the present invention.
  • Fig. 9 illustrates a flow chart of processing data, which is buffered in the secondary base station due to release of a small cell according to another embodiment of the present invention.
  • the present invention provides a procedure for forwarding data from a secondary base station to a primary base station or CN under the situation in which a small cell is released or deactivated in order to avoid data loss.
  • a secondary base station is connected to a primary base station by non-ideal backhaul.
  • Data can be split to a secondary base station either from CN or from a primary base station to guarantee data transmission in a small cell, so as to provide a higher system capacity.
  • the small cell will be always configured as Scell (Scell_S) to UE by RRC message.
  • Scell_S Scell
  • the Scell can be added/released/activated/de-activated for different purpose.
  • the present invention will support two kind of data transmission as listed here:
  • Fl data is split from CN or primary base station to secondary base station for DL Tx, which is determined by UP splitting scheme.
  • F2 data is split from secondary base station to CN or primary base station when secondary base station has no chance to continue the DL data transmission.
  • Option 1.1 data split to a small cell is started when a small cell is added.
  • Option 1.2 data split to a small cell is started when a small cell is activated.
  • Fig. l illustrates a flow chart of a method of splitting data to a secondary base station according to one embodiment of the present invention.
  • step S 101 the primary base station sends a control signaling to a user equipment, which indicates that a small cell is added for the user equipment.
  • This control signaling could be RRC control signaling, for example.
  • step S 102 the user equipment sends a confirmation message to the primary base station in response to the above control signaling.
  • step S 103 the primary base station sends a first indication message to the secondary base station, which indicates that the primary base station added the small cell for the user equipment.
  • the secondary base station will send a second confirmation message to the primary base station in response to this first indication message.
  • step S I 04 under the CN level data split mechanism, the primary base station will send a second indication message to CN, which indicates CN to split the data to the secondary base station.
  • CN This could be implemented by S I interface between CN and the primary base station.
  • the secondary base station also could send a third indication message to CN actively, which indicates CN to split the data to the secondary base station.
  • this procedure could also be implemented by S I interface between CN and the secondary base station.
  • the flow control functionality in CN can split data to the secondary base station, and then the secondary base station will use those data for DL Tx for the user equipment.
  • step S I 04 under the RAN level data split mechanism, the primary base station will split data to the secondary base station directly. That is, under this situation, the flow control functionality in the primary base station will split the corresponding data to the secondary base station.
  • step S I 04 could be conduct simultaneously as step S 103 or before step S 103.
  • option 1.1 when the secondary base station is ready for DL transmission, there is already data buffered in the secondary base station, hence it can start the DL transmission as early as possible.
  • option 1.2 will be discussed.
  • Fl will be trigged only when a small cell is trigged. This means that Fl is triggered only when the small cell is ready to conduct DL transmission.
  • the detail procedure to realize option 2 is related to where the small cell activation decision is made and where the related control signaling for activating the small cell will be sent down. Firstly, the situation, in which the small cell activation decision is made on the primary base station side, will be described.
  • FIG.2 illustrates a flow chart of a method of splitting data to a secondary base station according to another embodiment of the present invention.
  • step S201 the primary base station determines a small cell to be activated for a user equipment, and sends a first notification to the secondary base station, which indicates the secondary base station to activate the determined small cell.
  • step S202 the secondary base station activates the small cell according to the first notification.
  • the secondary base station will send a confirmation message to the primary base station in response to the first notification.
  • step S203 the primary base station sends a first control signaling to the user equipment, which indicates the small cell activated for the user equipment.
  • This signaling could be a MAC layer control signaling, for example.
  • step S204 the primary base station receives a first confirmation message in response to the first control signaling from the user equipment.
  • step S205 the primary base station forwards the first confirmation message to the secondary base station to inform the secondary base station that the user equipment has confirmed the activation of the small cell.
  • step S206 under the CN level data split mechanism, the primary base station sends a first indication message to CN, which indicates CN to split the data to the secondary base station.
  • CN This could be implemented by S I interface between CN and the primary base station, for example.
  • the secondary base station also could send a second indication message to CN actively, which indicates CN to split data to the secondary base station.
  • this procedure could also be implemented by S 1 interface between CN and the secondary base station.
  • the flow control functionality in CN can split data to the secondary base station, and then the secondary base station will use those data for DL Tx for the user equipment.
  • step S206 under the RAN level data split mechanism, the primary base station will split data to the secondary base station directly. That is, under this situation, the flow control functionality in the primary base station will split the corresponding data to the secondary base station.
  • step S206 could be conduct simultaneously as step S205, or step S206 could be implemented firstly.
  • FIG.3 illustrates a flow chart of a method of splitting data to a secondary base station according to a further embodiment of the present invention.
  • the secondary base station sends a first controlling signaling to a user equipment to indicate that a small cell is activated for a user equipment. Similar with above, this control signaling could be a MAC layer signaling, for example.
  • step S302 the secondary base station receives a confirmation message in response to the first control signaling from the user equipment.
  • step S303 under the CN level data split mechanism, the secondary base station sends an indication message to CN for requesting data split, and receives data from CN.
  • the secondary base station under the RAN level data split mechanism, the secondary base station sends an indication message to a primary base station for requesting data split, and receives data from the primary base station.
  • the flow control functionality in CN or the primary base station will prepare and split data to the secondary base station according to the indication message.
  • option 1.2 The advantage of option 1.2 is that the data will be timely split from CN or the primary base station to the secondary base station and will not buffered, since the small cell has already been activated for the DL transmission for the user equipment.
  • the small cell could be deactivated or released.
  • the DL transmission on the small cell will be temporarily or permanently pending. Therefore, it is necessary to end or pending splitting data to the secondary base station to avoid that the data are buffed on the side of the secondary base station and will not be used for DL transmission.
  • the sender of the control signaling for releasing the small cell is the secondary base station.
  • FIG.4 illustrates a flow chart of a method of ending splitting data to a secondary base station according to one embodiment of the present invention.
  • step S401 the secondary base station sends a control signaling to a user equipment, which indicates that a small cell is released for the user equipment.
  • This control signaling could be a RRC control signaling, for example.
  • step S402 the secondary base station receives a first confirmation message from the user equipment in response to the control signaling.
  • step S403 under the CN level data split mechanism, the secondary base station sends an indication message to CN, which indicates CN to end splitting the data to the secondary base station.
  • the secondary base station Under the RAN level data split mechanism, the secondary base station sends an indication message to the primary base station, which indicates the primary base station to end splitting the data to the secondary base station.
  • the flow control functionality in CN or the primary base station will end splitting data to the secondary base station according to the indication message.
  • the sender of the control signaling for releasing the small cell is the primary base station.
  • FIG.5 illustrates a flow chart of a method of ending splitting data to a secondary base station according to another embodiment of the present invention.
  • step S501 the primary base station sends a control signaling to a user equipment, which indicates that a small cell is released for the user equipment.
  • This control signaling could be a RRC control signaling, for example.
  • step S502 the primary base station receives a first confirmation message in response to the control signaling from a user equipment.
  • step S503 the primary base station forwards the first confirmation message to the secondary base station.
  • the secondary base station will send a second confirmation message to the primary base station in response to this message.
  • step S504 under the CN level data split mechanism, the primary base station sends a first indication message to CN, which indicates CN to end splitting the data to the secondary base station.
  • the secondary base station sends a second indication message to CN, which indicates CN to end splitting the data to the secondary base station.
  • the flow control functionality in CN will end splitting data to the secondary base station.
  • the primary base station ends splitting data to the secondary base station. That is, the flow control functionality in the primary base station functions to end splitting data to the secondary base station. It shall be noted that, similar to the above schemes, there is no fixed order between step S504 and previous step S502, S503. Those steps could be conduct inversely or simultaneously.
  • FIG. 6 illustrates a flow chart of a method of pending splitting data to a secondary base station according to another embodiment of the present invention.
  • step S601 the primary base station sends a control signaling to a user equipment, which indicates that a small cell is released for the user equipment.
  • This control signaling could be a MAC level signaling, for example.
  • step S602 the primary base station receives a first confirmation message from the user equipment in response to the first control signaling.
  • step S603 the primary base station sends a first indication message to the secondary base station, which indicates the secondary base station to deactivate the small cell for the user equipment.
  • step S604 preferably the primary base station receives a confirmation message in response to the first indication message from the secondary base station. And when it is determined that the deactivated time for the small cell reaches a predetermined threshold, under the CN level data split mechanism, the primary base station sends a second indication message to CN, which indicates CN to pending splitting data to the secondary base station. Alternatively, under the RAN level data split mechanism, the primary base station is directly pending splitting data to the secondary base station.
  • step S604 could be implemented after step S601 directly, and step S602 and step S603 could be implemented simultaneously or inversely.
  • FIG. 7 illustrates a flow chart of a method of pending splitting data to a secondary base station according to a further embodiment of the present invention.
  • step S701 the secondary base station sends a first control signaling to the user equipment, which indicates a small cell is deactivated for the user equipment.
  • This control signaling could be a MAC level signaling, for example.
  • step S702 the secondary base station receives a first confirmation message in response to the first control signaling from the user equipment, and deactivates the small cell.
  • step S703 when it is determined that the deactivated time for the small cell reaches a predetermined threshold, under the CN level data split mechanism, the secondary base station sends an indication message to CN, which indicates CN to pending splitting data to the secondary base station.
  • the secondary base station under the RAN level data split mechanism, the secondary base station sends an indication message to the primary base station, which indicates the primary base station to pending splitting data to the secondary base station.
  • the flow control functionality in CN or the primary base station will pending splitting data to the secondary base station according to the indication message.
  • the present invention has presented two schemes herein: 1. discarding those data directly; 2. forwarding those buffered data to the primary base station, or forwarding those data to the primary base station through CN.
  • FIG. 8 illustrates a flow chart of processing data, which is buffered in the secondary base station due to release of a small cell according to a further embodiment of the present invention.
  • step S801 the primary base station sends a control signaling to the user equipment, which indicates a small cell is released for the user equipment.
  • the control signaling could be a RRC control signaling, for example.
  • step S802 the primary base station receives a first confirmation message in response to the control signaling from the user equipment.
  • step S803 the primary base station forwards the first confirmation message to the secondary base station.
  • step S804 the primary base station receives an indication message from the secondary base station, which indicates the secondary base station to perform data forwarding.
  • step S805 the primary base station receives buffered data from the secondary base station or CN.
  • the secondary base station sends the data to CN at first, and CN will forward the data to the primary base station.
  • step S806 the secondary base station sends an ending message to the primary base station or CN, which indicates that the data forwarding is ended, that is the buffered data has been sent completely.
  • the primary base station could send those data to the user equipment without impact on the user experience, and guarantee the quality of DL transmission.
  • the secondary base station may not conduct the above steps, and instead discard the buffered data.
  • FIG. 9 illustrates a flow chart of processing data, which is buffered in the secondary base station due to release of a small cell according to another embodiment of the present invention.
  • the secondary base station sends a control signaling to the user equipment, which indicates a small cell is released for the user equipment.
  • the control signaling could be a RRC control signaling, for example.
  • step S902 the secondary base station receives a first confirmation message in response to the control signaling from the user equipment.
  • step S903 the secondary base station sends an indication message to the primary base station or CN, which indicates that the secondary base station will perform data forwarding.
  • step S904 the secondary base station forwards the buffered data to the primary base station or CN.
  • CN will forward those data to the primary base station.
  • step S905 the secondary base station sends an ending message to the primary base station or CN, which indicates that the data forwarding is ended, that is the buffered data has been sent completely.
  • the primary base station could send those data to the user equipment without impact on the user experience, and guarantee the quality of DL transmission.
  • the secondary base station may not conduct the above steps, and instead discard the buffered data.
  • some small cells will be configured as always in an activated mode, and of course those cells could also be released. This guarantees that before releasing those small cells, at least on small cell among the small cells served by the secondary base station is in the activated mode, which ensure that the data buffed in the secondary base station will be sent to the user equipment.
  • the procedure for defining those small cells can be based on the signaling of the base station or the user equipments could select by themselves through the predetermined rule shared with the base station.
  • the primary base station or the secondary base station can inform that which small cells are always in the activated mode, or if a certain small cell is always in the activated mode by a control signaling, a control signaling RRC for adding small cells, for example.
  • the user equipment could define the small cell, the index number of which is smallest, is the small cell which is always in the activated mode.

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Abstract

The invention provides a method of splitting data to a secondary base station in a carrier aggregation based communication System, a method of ending splitting data to a secondary base station in a carrier aggregation based communication System, and a method of processing data, which is buffered in a secondary base station due to release of a small cell, in a carrier aggregation based communication System. In one embodiment of the present invention, a primary base station sends a control signaling to a user equipment, the control signaling indicating that a small cell is added for the user equipment; receives a confirmation message from the user equipment in response to the control signaling; sends a first indication message to the secondary base station, the first indication message indicating that the primary base station added the small cell for the user equipment; and sends a second indication message to a core network, the second indication message indicating the core network to split the data to the secondary base station; or splits the data to the secondary base station.

Description

Method of Splitting Data to a Secondary Base Station
Field of the invention
The present disclosure relates to communication technology and particularly to a method of splitting data to a secondary base station in a carrier aggregation based communication system, a method of ending splitting data to a secondary base station in a carrier aggregation based communication system, and a method of processing data, which is buffered in a secondary base station due to release of a small cell, in a carrier aggregation based communication system.
Background of the invention
According to current status, the new R12 Study Item(SI) on Small cell enhancement-high layer has been approved in RAN 58. One important objective of this SI is on "dual connectivity" research and realization. This refers to situation that UE keeps communication with at least two base stations at the same time, which are connected by non-ideal backhaul. And this is the key difference to Rl l CA (carrier aggregation) scenario.
One potential solution to support this functionality is based on CA concept with Macro cell used as primary cell (Pcell) and small cell used as secondary cell (Scell). The most important benefit of this concept is no Pcell change situation hence no HO procedure will be triggered during UE staying in Macro coverage. And when a user equipment (UE) moves into a small cell coverage, it can be added as Scell to support the traffic offload. In general speaking, there maybe multiple carriers controlled by Macro base station (eNB_M) and small cell base station (eNB_S) respectively. For example, this means there will be one Pcell and, zero/one/multiple Scell controlled by eNB_M and zero/one/multiple Scell controlled by eNB_S.
Regarding dual connectivity topic, one of the key issues is on UP data splitting. The UP split scheme can be classified into two schemes: in core network or in RAN level. Regardless CN or RAN level UP splitting, the key issue is how to split data to small cell for DL transmission. And the following two options can be considered:
Option 1 : scheduling decision triggered data forwarding;
Option 2: Non- scheduling triggered forwarding.
The first option refers to situation that after scheduling decision, the amount of data determined by the scheduling grant is split to small cells for DL Tx. Hence there should no source data buffered in small cells since all split data will be sent down in one TTI. While for the later, the data is split to small cells by some kind of flow control functionality, which is either located in CN or in primary cell. After scheduling decision, these buffered source data will be sent down in small cells. Hence it is clear that there always will be source data buffered in small cells, which is the key difference to the first option. Option 1 may be linked to MAC layer splitting scheme while option 2 is related to other RAN level and CN level UP splitting scheme. Since MAC layer splitting scheme would produce non-backhaul effect, the present invention will only focus on option 2 where data splitting is controlled by flow-control functionality, either located in CN or the primary cell.
For option 2, as clarified above, there will be always source data (either as RLC SDU/PDCH PDU or PDCP SDU/IP) buffered at small cells waiting for DL Tx. And according to CA concept, the small cell of eNB_S will be configured as Scell_S to UE from UE perspective. The Scell of a UE will be added/released/activated/de-activated according to base station decision. Then, the following problem will come: those add/release/activate/de-activate process will have impacts on the DL data transmission for the small cell and how to solve these impacts. Summary of the invention
In view of this, according to a first aspect of the invention, there is proposed a method, in a primary base station, of supporting splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:- sending a control signaling to a user equipment, the control signaling indicating that a small cell is added for the user equipment;- receiving a confirmation message from the user equipment in response to the control signaling;- sending a first indication message to the secondary base station, the first indication message indicating that the primary base station added the small cell for the user equipment; and - sending a second indication message to a core network, the second indication message indicating the core network to split the data to the secondary base station; or splitting the data to the secondary base station.
Further, there is proposed a method, in a secondary base station, of supporting splitting data to the secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising: - receiving a first indication message from a primary base station, the first indication message indicating that the primary base station added a small cell for a user equipment; and- sending a third indication message to a core network, the third indication message indicating the core network to split the data to the secondary base station, and receiving data from the core network; or receiving data from a core network; or receiving data from the primary base station.
According to a second aspect of the invention, there is proposed a method, in a primary base station, of supporting splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:- determining a small cell to be activated for a user equipment, and sending a first notification to the secondary base station, the first notification indicating the secondary base station to activate the determined small cell; - sending a first controlling signaling to the user equipment, the first controlling signaling indicating the small cell activated for the user equipment;- receiving a first confirmation message from the user equipment in response to the first controlling signaling;- forwarding the first confirmation message to the secondary base station; and - sending a first indication message to a core network, the first indication message indicating the core network to split the data to the secondary base station; or splitting the data to the secondary base station.
Further, there is proposed a method, in a secondary base station, of supporting splitting data to the secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:- receiving a first notification from a primary base station, the first notification indicating the secondary base station the small cell needed to be activated for a user equipment determined by the primary base station, and activating the small cell according to the first notification;- receiving a first confirmation message from the primary base station, the first confirmation message indicating that the user equipment confirmed that the small cell had been activated for it; and- sending a second indication message to a core network, the second indication message indicating the core network to split the data to the secondary base station, and receiving data from the core network; or receiving data from a core network; or receiving data from the primary base station.
According to a third aspect of the invention, there is proposed a method, in a secondary base station, of supporting splitting data to the secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:- sending a first controlling signaling to a user equipment, the first controlling signaling indicating that a small cell is activated for a user equipment;- receiving a confirmation message from the user equipment in response to the control signaling;- sending an indication message to a primary base station for requesting data split, and receiving data from the primary base station; or sending an indication message to a core network for requesting data split, and receiving data from the core network.
Further, there is proposed a method, in a primary base station or a core network, of supporting splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising: - receiving an indication message from the secondary base station, the indication message requesting to split the data to the secondary base station; and- splitting the data to the secondary base station according to the indication message.
According to a fourth aspect of the invention, there is proposed a method, in a secondary base station, of supporting stopping splitting data to the secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:- sending a control signaling to a user equipment, the control signaling indicating that one small cell is released for the user equipment;- receiving a first confirmation message from the user equipment in response to the control signaling;- sending an indication message to a primary base station, the indication message indicating the primary base station to end splitting data to the secondary base station; or sending an indication message to a core network, the indication message indicating the core network to end splitting the data to the secondary base station.
Further, there is proposed a method, in a primary base station or a core network, of supporting ending splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising: - receiving an indication message from the secondary base station, the indication message indicating ending splitting the data to the secondary base station; and- ending forwarding the data to the secondary base station according to the indication message.
According to a fifth aspect of the invention, there is proposed a method, in a primary base station, of supporting ending splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:- sending a control signaling to a user equipment, the control signaling indicating that one small cell is released for the user equipment;- receiving a first confirmation message from the user equipment in response to the control signaling;- forwarding the first confirmation message to the secondary base station; and- ending splitting the data to the secondary base station; or sending a first indication message to a core network, the first indication message indicating the core network to end splitting the data to the secondary base station.
Further, there is proposed a method, in a secondary base station, of supporting ending splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:- receiving a first confirmation message from a primary base station, the first confirmation message indicating that the user equipment confirmed that the small cell had been released for it; and- sending a second indication message to a core network, the second confirmation message indicating the core network to end splitting the data to the secondary base station.
According to a sixth aspect of the invention, there is proposed a method, in a primary base station, of supporting forwarding data to the primary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, and the data is buffered in the secondary base station due to release of a small cell, the method comprising:- sending a control signaling to a user equipment, the control signaling indicating that a small cell is released for the user equipment;- receiving a first confirmation message from the user equipment in response to the control signaling;- forwarding the first confirmation message to the secondary base station;- receiving an indication message from the secondary base station, the indication message indicating that the secondary base station will perform data forwarding;- receiving the data from the secondary base station or a core network; and- receiving an ending message from the secondary base station, the ending message indicating that the data forwarding is ended.
Further, there is proposed a method, in a secondary base station, of processing data, which is buffered in the secondary base station due to release of a small cell, in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:- discarding the data; or- forwarding the data, which further comprises the following steps: - receiving a first confirmation message from a primary base station, the first confirmation message indicating that a user equipment confirmed that the small cell had been released for it; - sending an indication message to the primary base station or a core network, the indication message indicating that the secondary base station will perform data forwarding; - forwarding the data to the primary base station or the core network; and - sending an ending message to the primary base station or the core network, the ending message indicating that the data forwarding is ended.
According to a seventh aspect of the invention, there is proposed a method, in a secondary base station, of processing data, which is buffered in the secondary base station due to release of a small cell, in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:- discarding the data; or- forwarding the data, which further comprises the following steps: - sending a control signaling to a user equipment, the control signaling indicating that a small cell is released for the user equipment; - receiving a first confirmation message from the user equipment in response to the control signaling; - sending an indication message to the primary base station or a core network, the indication message indicating that the secondary base station will perform data forwarding; - forwarding the data to the primary base station or the core network; and - sending an ending message to the primary base station or the core network, the ending message indicating that the data forwarding is ended.
Further, there is proposed a method, in a primary base station, of supporting forwarding data to the primary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, and the data is buffered in the secondary base station due to release of a small cell, the method comprising:- receiving an indication message from the secondary base station, the indication message indicating that the secondary base station will perform data forwarding;- receiving the data from the secondary base station or a core network; and- receiving an ending message from the secondary base station, the ending message indicating the data forwarding is ended.
The respective aspects of the invention will become more apparent from the following description of particular embodiments.
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 a flow chart of a method of splitting data to a secondary base station according to one embodiment of the present invention;
Fig.2 illustrates a flow chart of a method of splitting data to a secondary base station according to another embodiment of the present invention;
Fig.3 illustrates a flow chart of a method of splitting data to a secondary base station according to a further embodiment of the present invention;
Fig.4 illustrates a flow chart of a method of ending splitting data to a secondary base station according to one embodiment of the present invention;
Fig.5 illustrates a flow chart of a method of ending splitting data to a secondary base station according to another embodiment of the present invention;
Fig. 6 illustrates a flow chart of a method of pending splitting data to a secondary base station according to another embodiment of the present invention;
Fig. 7 illustrates a flow chart of a method of pending splitting data to a secondary base station according to a further embodiment of the present invention;
Fig. 8 illustrates a flow chart of processing data, which is buffered in the secondary base station due to release of a small cell according to a further embodiment of the present invention; and
Fig. 9 illustrates a flow chart of processing data, which is buffered in the secondary base station due to release of a small cell according to another embodiment of the present invention.
In the drawings, identical or like reference numerals denote identical or corresponding components or features throughout the different figures.
Detailed description of embodiments
In the present invention, two options to realize the data splitting (from CN or a primary base station to a secondary base station) for offload will be presented.
1. Procedure under the situation in which a small cell is added for a user equipment;
2. Procedure under the situation in which a small cell is activated for a user equipment.
Further, in the present invention, there is proposed a procedure for ending splitting data from CN or a primary base station to a secondary base station under the situation in which a small cell is released or deactivated.
At last, the present invention provides a procedure for forwarding data from a secondary base station to a primary base station or CN under the situation in which a small cell is released or deactivated in order to avoid data loss.
The above points will be discussed in detail below.
As discussed above, a secondary base station is connected to a primary base station by non-ideal backhaul. Data can be split to a secondary base station either from CN or from a primary base station to guarantee data transmission in a small cell, so as to provide a higher system capacity. This refers to the data split from CN/primary base station to a secondary base station for DL transmission. It will be called as Fl in this application.
Further, the small cell will be always configured as Scell (Scell_S) to UE by RRC message. According to R10/R11 principles, the Scell can be added/released/activated/de-activated for different purpose. These operation will have following impacts:
When Scell is activated, DL transmission can be conducted.
When Scell is released, it will have no chance to conduct the DL data transmission.
When Scell is de-activated, no DL data will be transmitted till it is activated once again.
It is clear that there exists a situation that Scell_S can not be used for DL transmission, regardless this pending is temporarily or permanently. For this situation, how to deal with those data packets buffered at a secondary base station is very important. The straightforward scheme is just to discard these data packets. But this simple operation will definitely degrade UE experience. Hence it is propose in the present invention that for these situations, the secondary base station is required to forward those buffered packets back to a primary base station or CN so that these data packets can be sent down to UE as early as possible. For this situation, it will be called as F2 in the present application.
In summary, in order to support dual connectivity, the present invention will support two kind of data transmission as listed here:
1. Fl : data is split from CN or primary base station to secondary base station for DL Tx, which is determined by UP splitting scheme.
2. F2: data is split from secondary base station to CN or primary base station when secondary base station has no chance to continue the DL data transmission.
Firstly, the situation for Fl will be discussed in detail:
For Fl , there exists the following two situations:
1. Situation 1 : Fl is triggered which means data is split from CN or primary base station to secondary base station.
2. Situation 2: Fl is stopped which means CN or primary base station stops splitting data to secondary base station.
Firstly, for situation 1 , the following two options will be considered: Option 1.1 : data split to a small cell is started when a small cell is added.
Option 1.2: data split to a small cell is started when a small cell is activated.
For option 1.1, Fig. l illustrates a flow chart of a method of splitting data to a secondary base station according to one embodiment of the present invention.
As shown in Fig. l , in step S 101 , the primary base station sends a control signaling to a user equipment, which indicates that a small cell is added for the user equipment. This control signaling could be RRC control signaling, for example.
Then, in step S 102, the user equipment sends a confirmation message to the primary base station in response to the above control signaling.
Then, in step S 103, the primary base station sends a first indication message to the secondary base station, which indicates that the primary base station added the small cell for the user equipment. Here, preferably, the secondary base station will send a second confirmation message to the primary base station in response to this first indication message.
Then, in step S I 04, under the CN level data split mechanism, the primary base station will send a second indication message to CN, which indicates CN to split the data to the secondary base station. This could be implemented by S I interface between CN and the primary base station. Alternatively, herein, the secondary base station also could send a third indication message to CN actively, which indicates CN to split the data to the secondary base station. Similarly, this procedure could also be implemented by S I interface between CN and the secondary base station. In the above two situations, the flow control functionality in CN can split data to the secondary base station, and then the secondary base station will use those data for DL Tx for the user equipment.
Further, in step S I 04, under the RAN level data split mechanism, the primary base station will split data to the secondary base station directly. That is, under this situation, the flow control functionality in the primary base station will split the corresponding data to the secondary base station.
Herein, it shall be noted that the order of steps in this embodiment is not fixed. For example, step S I 04 could be conduct simultaneously as step S 103 or before step S 103.
The advantage of option 1.1 is that when the secondary base station is ready for DL transmission, there is already data buffered in the secondary base station, hence it can start the DL transmission as early as possible.
Further, the option 1.2 will be discussed. For this situation, Fl will be trigged only when a small cell is trigged. This means that Fl is triggered only when the small cell is ready to conduct DL transmission. The detail procedure to realize option 2 is related to where the small cell activation decision is made and where the related control signaling for activating the small cell will be sent down. Firstly, the situation, in which the small cell activation decision is made on the primary base station side, will be described.
For this situation, Fig.2 illustrates a flow chart of a method of splitting data to a secondary base station according to another embodiment of the present invention.
As shown in Fig.2, in step S201 , the primary base station determines a small cell to be activated for a user equipment, and sends a first notification to the secondary base station, which indicates the secondary base station to activate the determined small cell.
Then, in step S202, the secondary base station activates the small cell according to the first notification. Preferably, the secondary base station will send a confirmation message to the primary base station in response to the first notification.
In step S203, the primary base station sends a first control signaling to the user equipment, which indicates the small cell activated for the user equipment. This signaling could be a MAC layer control signaling, for example.
Then, in step S204, the primary base station receives a first confirmation message in response to the first control signaling from the user equipment.
In step S205, the primary base station forwards the first confirmation message to the secondary base station to inform the secondary base station that the user equipment has confirmed the activation of the small cell.
Then, in step S206, under the CN level data split mechanism, the primary base station sends a first indication message to CN, which indicates CN to split the data to the secondary base station. This could be implemented by S I interface between CN and the primary base station, for example. Alternatively, herein, the secondary base station also could send a second indication message to CN actively, which indicates CN to split data to the secondary base station. Similarly, this procedure could also be implemented by S 1 interface between CN and the secondary base station. In the above two situations, the flow control functionality in CN can split data to the secondary base station, and then the secondary base station will use those data for DL Tx for the user equipment.
Further, in step S206, under the RAN level data split mechanism, the primary base station will split data to the secondary base station directly. That is, under this situation, the flow control functionality in the primary base station will split the corresponding data to the secondary base station.
Herein, it shall be noted that the order of steps in this embodiment is not fixed. For example, step S206 could be conduct simultaneously as step S205, or step S206 could be implemented firstly.
Now, the situation, in which the small cell activation decision is made on the secondary base station side, will be described.
For this situation, Fig.3 illustrates a flow chart of a method of splitting data to a secondary base station according to a further embodiment of the present invention.
As shown in Fig.3, in step S301 , the secondary base station sends a first controlling signaling to a user equipment to indicate that a small cell is activated for a user equipment. Similar with above, this control signaling could be a MAC layer signaling, for example.
Then, in step S302, the secondary base station receives a confirmation message in response to the first control signaling from the user equipment.
Then, in step S303, under the CN level data split mechanism, the secondary base station sends an indication message to CN for requesting data split, and receives data from CN. Alternatively, under the RAN level data split mechanism, the secondary base station sends an indication message to a primary base station for requesting data split, and receives data from the primary base station. In the above two situations, the flow control functionality in CN or the primary base station will prepare and split data to the secondary base station according to the indication message.
The advantage of option 1.2 is that the data will be timely split from CN or the primary base station to the secondary base station and will not buffered, since the small cell has already been activated for the DL transmission for the user equipment.
Now, the situation 2, in which Fl will be ended, will be described.
As discussed above, the small cell could be deactivated or released. For those two situations, the DL transmission on the small cell will be temporarily or permanently pending. Therefore, it is necessary to end or pending splitting data to the secondary base station to avoid that the data are buffed on the side of the secondary base station and will not be used for DL transmission.
Firstly, the situation, in which the small cell is released, will be described. Herein, it will be dependent on the sender of the control signaling for releasing the small cell.
1. The sender of the control signaling for releasing the small cell is the secondary base station.
For this situation, Fig.4 illustrates a flow chart of a method of ending splitting data to a secondary base station according to one embodiment of the present invention.
In step S401 , the secondary base station sends a control signaling to a user equipment, which indicates that a small cell is released for the user equipment. This control signaling could be a RRC control signaling, for example.
In step S402, the secondary base station receives a first confirmation message from the user equipment in response to the control signaling.
Then, in step S403, under the CN level data split mechanism, the secondary base station sends an indication message to CN, which indicates CN to end splitting the data to the secondary base station. Under the RAN level data split mechanism, the secondary base station sends an indication message to the primary base station, which indicates the primary base station to end splitting the data to the secondary base station. Thus, the flow control functionality in CN or the primary base station will end splitting data to the secondary base station according to the indication message.
2. The sender of the control signaling for releasing the small cell is the primary base station.
For this situation, Fig.5 illustrates a flow chart of a method of ending splitting data to a secondary base station according to another embodiment of the present invention.
In step S501 , the primary base station sends a control signaling to a user equipment, which indicates that a small cell is released for the user equipment. This control signaling could be a RRC control signaling, for example.
In step S502, the primary base station receives a first confirmation message in response to the control signaling from a user equipment.
In step S503, the primary base station forwards the first confirmation message to the secondary base station. Preferably, the secondary base station will send a second confirmation message to the primary base station in response to this message.
At last, in step S504, under the CN level data split mechanism, the primary base station sends a first indication message to CN, which indicates CN to end splitting the data to the secondary base station. Alternatively, the secondary base station sends a second indication message to CN, which indicates CN to end splitting the data to the secondary base station. In the above two situations, the flow control functionality in CN will end splitting data to the secondary base station.
Alternatively, under the RAN level data split mechanism, the primary base station ends splitting data to the secondary base station. That is, the flow control functionality in the primary base station functions to end splitting data to the secondary base station. It shall be noted that, similar to the above schemes, there is no fixed order between step S504 and previous step S502, S503. Those steps could be conduct inversely or simultaneously.
Now the situation, in which a small cell is deactivated, will be described. Herein, when the deactivated time for the small cell reaches a predetermined threshold, the data will be pending to split to the secondary base station. The detail procedure of the scheme is dependent on where the small cell deactivation decision is made and where the related control signaling for deactivating the small cell will be sent down.
Firstly, the situation, in which the small cell deactivation decision is made on the primary base station side, will be described.
For this situation, Fig. 6 illustrates a flow chart of a method of pending splitting data to a secondary base station according to another embodiment of the present invention.
As shown in Fig.6, in step S601 , the primary base station sends a control signaling to a user equipment, which indicates that a small cell is released for the user equipment. This control signaling could be a MAC level signaling, for example.
In step S602, the primary base station receives a first confirmation message from the user equipment in response to the first control signaling.
Then, in step S603, the primary base station sends a first indication message to the secondary base station, which indicates the secondary base station to deactivate the small cell for the user equipment.
Then, in step S604, preferably the primary base station receives a confirmation message in response to the first indication message from the secondary base station. And when it is determined that the deactivated time for the small cell reaches a predetermined threshold, under the CN level data split mechanism, the primary base station sends a second indication message to CN, which indicates CN to pending splitting data to the secondary base station. Alternatively, under the RAN level data split mechanism, the primary base station is directly pending splitting data to the secondary base station.
Similarly, in this embodiment, the order of steps is not fixed. For example, step S604 could be implemented after step S601 directly, and step S602 and step S603 could be implemented simultaneously or inversely.
Now, the situation, in which the small cell deactivation decision is made on the secondary base station side, will be described.
For this situation, Fig. 7 illustrates a flow chart of a method of pending splitting data to a secondary base station according to a further embodiment of the present invention.
As shown in Fig.7, in step S701 , the secondary base station sends a first control signaling to the user equipment, which indicates a small cell is deactivated for the user equipment. This control signaling could be a MAC level signaling, for example.
In step S702, the secondary base station receives a first confirmation message in response to the first control signaling from the user equipment, and deactivates the small cell.
Then, in step S703, when it is determined that the deactivated time for the small cell reaches a predetermined threshold, under the CN level data split mechanism, the secondary base station sends an indication message to CN, which indicates CN to pending splitting data to the secondary base station. Alternatively, under the RAN level data split mechanism, the secondary base station sends an indication message to the primary base station, which indicates the primary base station to pending splitting data to the secondary base station. In the above two situations, the flow control functionality in CN or the primary base station will pending splitting data to the secondary base station according to the indication message.
Now, the situation for F2 will be described in detail.
As described above, when a small cell is released, the buffered data in the side of the secondary base station will not be transmitted to the user equipment. How to process those buffere data, the present invention has presented two schemes herein: 1. discarding those data directly; 2. forwarding those buffered data to the primary base station, or forwarding those data to the primary base station through CN.
Firstly, the situation, in which the control signaling for releasing the small cell is sent by the primary base station, will be described.
For this situation, Fig. 8 illustrates a flow chart of processing data, which is buffered in the secondary base station due to release of a small cell according to a further embodiment of the present invention.
As shown in Fig.8, in step S801 , the primary base station sends a control signaling to the user equipment, which indicates a small cell is released for the user equipment. The control signaling could be a RRC control signaling, for example.
In step S802, the primary base station receives a first confirmation message in response to the control signaling from the user equipment.
In step S803, the primary base station forwards the first confirmation message to the secondary base station.
In step S804, the primary base station receives an indication message from the secondary base station, which indicates the secondary base station to perform data forwarding.
Then, in step S805, the primary base station receives buffered data from the secondary base station or CN. In the later situation, the secondary base station sends the data to CN at first, and CN will forward the data to the primary base station.
At last, in step S806, the secondary base station sends an ending message to the primary base station or CN, which indicates that the data forwarding is ended, that is the buffered data has been sent completely.
Therefore, the primary base station could send those data to the user equipment without impact on the user experience, and guarantee the quality of DL transmission. Alternatively, the secondary base station may not conduct the above steps, and instead discard the buffered data.
Then, the situation, in which the control signaling for releasing the small cell is sent by the secondary base station, will be described.
For this situation, Fig. 9 illustrates a flow chart of processing data, which is buffered in the secondary base station due to release of a small cell according to another embodiment of the present invention.
As shown in Fig.9, in step S901 , the secondary base station sends a control signaling to the user equipment, which indicates a small cell is released for the user equipment. The control signaling could be a RRC control signaling, for example.
In step S902, the secondary base station receives a first confirmation message in response to the control signaling from the user equipment.
Then, in step S903, the secondary base station sends an indication message to the primary base station or CN, which indicates that the secondary base station will perform data forwarding.
Then, in step S904, the secondary base station forwards the buffered data to the primary base station or CN. In the later situation, CN will forward those data to the primary base station.
At last, in step S905, the secondary base station sends an ending message to the primary base station or CN, which indicates that the data forwarding is ended, that is the buffered data has been sent completely.
Therefore, the primary base station could send those data to the user equipment without impact on the user experience, and guarantee the quality of DL transmission.
Similarly, alternatively, the secondary base station may not conduct the above steps, and instead discard the buffered data.
Further, according to the present invention, some small cells will be configured as always in an activated mode, and of course those cells could also be released. This guarantees that before releasing those small cells, at least on small cell among the small cells served by the secondary base station is in the activated mode, which ensure that the data buffed in the secondary base station will be sent to the user equipment. The procedure for defining those small cells can be based on the signaling of the base station or the user equipments could select by themselves through the predetermined rule shared with the base station.
For the first situation, the primary base station or the secondary base station can inform that which small cells are always in the activated mode, or if a certain small cell is always in the activated mode by a control signaling, a control signaling RRC for adding small cells, for example.
For the later situation, for example, the user equipment could define the small cell, the index number of which is smallest, is the small cell which is always in the activated mode.
Through the above two ways for configuring small cells, the influence on the user experience will be reduced.
It shall be appreciated that the foregoing embodiments are merely illustrative but will not limit the invention. Any technical solutions without departing from the spirit of the invention shall fall into the scope of invention, including the use of different technical solutions appearing in different embodiments, and an apparatus and a method can be combined to advantage. Moreover any reference numerals in the claims shall not be construed as limiting the claims in question; and the term "comprising" will not preclude another device(s) or step(s) which is (are) listed in the other claim(s) or the description.

Claims

1. A method, in a primary base station, of supporting splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- sending a control signaling to a user equipment, the control signaling indicating that a small cell is added for the user equipment;
- receiving a confirmation message from the user equipment in response to the control signaling;
- sending a first indication message to the secondary base station, the first indication message indicating that the primary base station added the small cell for the user equipment; and
- sending a second indication message to a core network, the second indication message indicating the core network to split the data to the secondary base station; or
splitting the data to the secondary base station.
2. A method, in a secondary base station, of supporting splitting data to the secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- receiving a first indication message from a primary base station, the first indication message indicating that the primary base station added a small cell for a user equipment; and
- sending a third indication message to a core network, the third indication message indicating the core network to split the data to the secondary base station, and receiving data from the core network; or
receiving data from a core network; or
receiving data from the primary base station.
3. A method, in a primary base station, of supporting splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- determining a small cell to be activated for a user equipment, and sending a first notification to the secondary base station, the first notification indicating the secondary base station to activate the determined small cell;
- sending a first controlling signaling to the user equipment, the first controlling signaling indicating the small cell activated for the user equipment;
- receiving a first confirmation message from the user equipment in response to the first controlling signaling;
- forwarding the first confirmation message to the secondary base station; and
- sending a first indication message to a core network, the first indication message indicating the core network to split the data to the secondary base station; or
splitting the data to the secondary base station.
4. A method, in a secondary base station, of supporting splitting data to the secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- receiving a first notification from a primary base station, the first notification indicating the secondary base station the small cell needed to be activated for a user equipment determined by the primary base station, and activating the small cell according to the first notification;
- receiving a first confirmation message from the primary base station, the first confirmation message indicating that the user equipment confirmed that the small cell had been activated for it; and
- sending a second indication message to a core network, the second indication message indicating the core network to split the data to the secondary base station, and receiving data from the core network; or
receiving data from a core network; or receiving data from the primary base station.
5. A method, in a secondary base station, of supporting splitting data to the secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- sending a first controlling signaling to a user equipment, the first controlling signaling indicating that a small cell is activated for a user equipment;
- receiving a confirmation message from the user equipment in response to the control signaling;
- sending an indication message to a primary base station for requesting data split, and receiving the data from the primary base station; or
sending an indication message to a core network for requesting data split, and receiving the data from the core network.
6. A method, in a primary base station or a core network, of supporting splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- receiving an indication message from the secondary base station, the indication message requesting to split the data to the secondary base station; and
- splitting the data to the secondary base station according to the indication message.
7. A method, in a secondary base station, of supporting stopping splitting data to the secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- sending a control signaling to a user equipment, the control signaling indicating that a small cell is released for the user equipment;
- receiving a first confirmation message from the user equipment in response to the control signaling; - sending an indication message to a primary base station, the indication message indicating the primary base station to end splitting data to the secondary base station; or
sending an indication message to a core network, the indication message indicating the core network to end splitting the data to the secondary base station.
8. A method, in a primary base station or a core network, of supporting ending splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- receiving an indication message from the secondary base station, the indication message indicating ending splitting the data to the secondary base station; and
- ending forwarding the data to the secondary base station according to the indication message.
9. A method, in a primary base station, of supporting ending splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- sending a control signaling to a user equipment, the control signaling indicating that a small cell is released for the user equipment;
- receiving a first confirmation message from the user equipment in response to the control signaling;
- forwarding the first confirmation message to the secondary base station; and
- ending splitting the data to the secondary base station; or
sending a first indication message to a core network, the first indication message indicating the core network to end splitting the data to the secondary base station.
10. A method, in a secondary base station, of supporting ending splitting data to a secondary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- receiving a first confirmation message from a primary base station, the first confirmation message indicating that the user equipment confirmed that the small cell had been released for it; and
- sending a second indication message to a core network, the second confirmation message indicating the core network to end splitting the data to the secondary base station.
11. A method, in a primary base station, of supporting forwarding data to the primary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, and the data is buffered in the secondary base station due to release of a small cell, the method comprising:
- sending a control signaling to a user equipment, the control signaling indicating that a small cell is released for the user equipment;
- receiving a first confirmation message from the user equipment in response to the control signaling;
- forwarding the first confirmation message to the secondary base station;
- receiving an indication message from the secondary base station, the indication message indicating that the secondary base station will perform data forwarding;
- receiving the data from the secondary base station or a core network; and
- receiving an ending message from the secondary base station, the ending message indicating that the data forwarding is ended.
12. A method, in a secondary base station, of processing data, which is buffered in the secondary base station due to release of a small cell, in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- discarding the data; or - forwarding the data, which further comprises the following steps:
- receiving a first confirmation message from a primary base station, the first confirmation message indicating that a user equipment confirmed that the small cell had been released for it;
- sending an indication message to the primary base station or a core network, the indication message indicating that the secondary base station will perform data forwarding;
- forwarding the data to the primary base station or the core network; and
- sending an ending message to the primary base station or the core network, the ending message indicating that the data forwarding is ended.
13. A method, in a secondary base station, of processing data, which is buffered in the secondary base station due to release of a small cell, in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
- discarding the data; or
- forwarding the data, which further comprises the following steps:
- sending a control signaling to a user equipment, the control signaling indicating that a small cell is released for the user equipment;
- receiving a first confirmation message from the user equipment in response to the control signaling;
- sending an indication message to the primary base station or a core network, the indication message indicating that the secondary base station will perform data forwarding;
- forwarding the data to the primary base station or the core network; and
- sending an ending message to the primary base station or the core network, the ending message indicating that the data forwarding is ended.
14. A method, in a primary base station, of supporting forwarding data to the primary base station in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, and the data is buffered in the secondary base station due to release of a small cell, the method comprising:
- receiving an indication message from the secondary base station, the indication message indicating that the secondary base station will perform data forwarding;
- receiving the data from the secondary base station or a core network; and
- receiving an ending message from the secondary base station, the ending message indicating the data forwarding is ended.
15. A method of configuring a small cell in a carrier aggregation based communication system, wherein the secondary base station serves one or more small cells, the method comprising:
a primary base station or the secondary base station sends a control signaling to a user equipment, the control signaling indicating one or more first small cells in the one or more small cells, wherein the first small cell is always in a activated mode; or
a user equipment selects one or more first small cells from the one or more small cells according a predetermined rule, wherein the first small cell is always in a activated mode.
PCT/IB2014/001060 2013-05-10 2014-05-07 Method of splitting data to a secondary base station WO2014181180A2 (en)

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