1. A radio communication system comprising: a first radio station that operates a first cell; and a second radio station that operates a second cell, wherein while a first radio connection on the first cell with a radio terminal is established, the first radio station requests or instructs the second radio station to prepare for communication with the radio terminal on the second cell, and the first radio station instructs the radio terminal or the second radio station to establish a second radio connection on the second cell between the second radio station and the radio terminal, while maintaining the first radio connection.

2. The radio communication system according to Claim 1, wherein the first radio station instructs the radio terminal to establish the second radio connection, and the radio terminal configures the second cell.

3. The radio communication system according to Claim 1, wherein the first radio station instructs the second radio station to establish the second radio connection, the second radio station instructs the radio terminal to establish the second radio connection, and the radio terminal configures the second cell.

4. The radio communication system according to any one of Claims 1 to 3, wherein the first radio station notifies the second radio station of terminal individual information of the radio terminal relating to establishment of the first or second radio connection.

5. The radio communication system according to Claim 4, wherein the second radio station triggers setup of a bearer for transferring user data of the radio terminal between an upper network and the second radio station, based on the terminal individual information.

6. The radio communication system according to any one of Claims 1 to 5, wherein the first radio station notifies the second radio station of at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.

7. The radio communication system according to any one of Claims 1 to 6, wherein the second radio station notifies the first radio station of at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.

8. The radio communication system according to any one of Claims 1 to 7, wherein the first cell is a primary cell, the second cell is a secondary cell, and the radio terminal sends at least one of Layer 1 control information and Layer 2 control information using a physical uplink control channel on the second cell.

9. The radio communication system according Claim 4 or 5, wherein the terminal individual information includes at least one of (a) radio terminal capability information, (b) radio terminal identifier information, (c) selected network information, (d) bearer information, (e) radio resource control information, (f) radio terminal mobility history information, and (g) service information.

10. The radio communication system according to Claim 6 or 7, wherein the radio connection configuration information includes at least one of (a) serving cell information, (b) system information, (c) radio resource configuration information, (c) measurement configuration information, (d) mobility control information, and (f) security configuration information.

11. The radio communication system according to Claim 6 or 7, wherein the radio access information includes at least one of (a) radio access identifier information and (b) radio access resource information.

12. The radio communication system according to any one of Claims 1 to 11, wherein the first radio station instructs the second radio station to establish the second radio connection in order to enable the radio terminal to simultaneously use the first and second cells for signal reception or transmission.

13. A first radio station that operates a first cell, the first radio station comprising: communication control means for controlling communication with a radio terminal having established a first radio connection on the first cell, wherein while the first radio connection on the first cell with the radio terminal is established, the communication control means requests or instructs a second radio station, which operates a second cell, to prepare for communication with the radio terminal on the second cell, and the communication control means instructs the radio terminal or the second radio station to establish a second radio connection on the second cell between the second radio station and the radio terminal, while maintaining the first radio connection.

14. The first radio station according to Claim 13, wherein the communication control means instructs the radio terminal to establish the second radio connection.

15. The first radio station according to Claim 13, wherein the communication control means instructs the second radio station to establish the second radio connection.

16. The first radio station according to any one of Claims 13 to 15, wherein the communication control means notifies the second radio station of terminal individual information of the radio terminal relating to establishment of the first or second radio connection.

17. The first radio station according to any one of Claims 13 to 16, wherein the communication control means notifies the second radio station of at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.

18. The first radio station according to any one of Claims 13 to 17, wherein the communication control means receives, from the second radio station, at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.

19. The first radio station according to any one of Claims 13 to 1 8, wherein the first cell is a primary cell, the second cell is a secondary cell, and the radio terminal sends at least one of Layer 1 control information and Layer 2 control information using a physical uplink control channel on the second cell.

20. The first radio station according to Claim 16, wherein the terminal individual information includes at least one of (a) radio terminal capability information, (b) radio terminal identifier information, (c) selected network information, (d) bearer information, (e) radio resource control information, (f) radio terminal mobility history information, and (g) service information.

21. The first radio station according to Claim 17 or 18, wherein the radio connection configuration information includes at least one of (a) serving cell information, (b) system information, (c) radio resource configuration information, (c) measurement configuration information, (d) mobility control information, and (f) security configuration information.

22. The first radio station according to Claim 17 or 18, wherein the radio access information includes at least one of (a) radio access identifier information and (b) radio access resource information.

23. The first radio station according to any one of Claims 13 to 22, wherein the communication control means instructs the second radio station to establish the second radio connection in order to enable the radio terminal to simultaneously use the first and second cells for signal reception or transmission.

24. A second radio station that operates a second cell, the second radio station comprising: communication control means for controlling communication with a radio terminal, wherein while a first radio connection with the radio terminal is established on a first cell operated by a first radio station, the communication control means prepares for communication with the radio terminal on the second cell in response to an instruction or a request from the first radio station, and the communication control means establishes, in response to an instruction from the first radio station, a second radio connection on the second cell between the second radio station and the radio terminal while the first radio connection is maintained.

25. The second radio station according to Claim 24, wherein the communication control means instructs the radio terminal to establish the second radio connection.

26. The second radio station according to Claim 24 or 25, wherein the communication control means receives, from the first radio station, terminal individual information of the radio terminal relating to establishment of the first or second radio connection.

27. The second radio station according to Claim 26, wherein the communication control means triggers setup of a bearer for transferring user data of the radio terminal between an upper network and the second radio station, based on the terminal individual information.

28. The second radio station according to any one of Claims 24 to 27, wherein the communication control means receives, from the first radio station, at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.

29. The second radio station according to any one of Claims 24 to 28, wherein the communication control means notifies the first radio station of at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.

30. A radio terminal that is used in combination with the radio communication system according to any one of Claims 1 to 12, the radio terminal comprising: radio communication means; and control means for configuring the second cell while maintaining the first radio connection with the first radio station, in response to an instruction from the first radio station or the second radio station.

31. The radio terminal according to Claim 30, wherein the first cell is a primary cell, the second cell is a secondary cell, and the radio communication means sends at least one of Layer 1 control information and Layer 2 control information using a physical uplink control channel on the second cell.

32. A communication control method in a first radio station that operates a first cell, the method comprising: requesting or instructing a second radio station, which operates a second cell, to prepare for communication with a radio terminal on the second cell, while a first radio connection on the first cell between the first radio station and the radio terminal is established; and instructing the radio terminal or the second radio station to establish a second radio connection on the second cell with the radio terminal, while maintaining the first radio connection.

33. The communication control method according to Claim 32, wherein the instructing to establish the second radio connection includes instructing the radio terminal to establish the second radio connection.

34. The communication control method according to Claim 32, wherein the instructing to establish the second radio connection includes instructing the second radio station to establish the second radio connection.

35. The communication control method according to any one of Claims 32 to 34, wherein the requesting or instructing to prepare for the communication with the radio terminal includes notifying the second radio station of terminal individual information of the radio terminal relating to establishment of the first or second radio connection.

36. The communication control method according to any one of Claims 32 to 35, wherein the requesting or instructing to prepare for the communication with the radio terminal includes notifying the second radio station of at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.

37. The communication control method according to any one of Claims 32 to 36, wherein the requesting or instructing to prepare for the communication with the radio terminal includes receiving, from the second radio station, at least one of radio connection configuration information relating to establishment of first or second radio connection and radio access information relating to the first or second radio connection.

38. A communication control method in a second radio station that operates a second cell, the method comprising: preparing for communication with a radio terminal on the second cell in response to an instruction or a request from a first radio station, while a first radio connection with the radio terminal on a first cell operated by the first radio station is established; and establishing, in response to an instruction from the first radio station, a second radio connection on the second cell between the second radio station and the radio terminal while the first radio connection is maintained.

39. The communication control method according to Claim 38, wherein the establishing includes instructing the radio terminal to establish the second radio connection.

40. The communication control method according to Claim 38 or 39, wherein the preparing includes receiving, from the first radio station, terminal individual information of the radio terminal relating to establishment of the first or second radio connection.

41. The communication control method according to Claim 40, further comprising triggering setup of a bearer for transferring user data of the radio terminal between an upper network and the second radio station, based on the terminal individual information.

42. A communication control method in a radio terminal that is used in combination with the radio communication system according to any one of Claims 1 to 12, the method comprising: configuring the second cell while maintaining the first radio connection with the first radio station, in response to an instruction from the first radio station or the second radio station.

43. A non-transitory computer readable medium that stores a program for causing a computer to perform a communication control method in a first radio station operating a first cell, the communication control method comprising: requesting or instructing a second radio station, which operates a second cell, to prepare for communication with the radio terminal on the second cell, while a first radio connection on the first cell with the radio terminal is established; and instructing the radio terminal or the second radio station to establish a second radio connection on the second cell with the radio terminal.

44. A non-transitory computer readable medium that stores a program for causing a computer to perform a communication control method in a second radio station operating a second cell, the communication control method comprising: preparing for communication with a radio terminal on the second cell in response to an instruction or a request from a first radio station, while a first radio connection with the radio terminal on a first cell operated by the first radio station is established; and establishing, in response to an instruction from the first radio station, a second radio connection on the second cell between the second radio station and the radio terminal while the first radio connection is maintained.

45. A non-transitory computer readable medium that stores a program for causing a computer to perform a communication control method in a radio terminal used in combination with the radio communication system according to any one of Claims 1 to 12, the communication control method comprising: configuring the second cell while maintaining the first radio connection with the first radio station, in response to an instruction from the first radio station or the second radio station.

DESCRIPTION
RADIO COMMUNICATION SYSTEM, RADIO STATION, RADIO
TERMINAL, COMMUNICATION CONTROL METHOD, AND
COMPUTER READABLE MEDIUM
Technical Field
[0001]
The present invention relates to a radio communication system in which a radio station communicates with a radio terminal using a plurality of cells. Background Art [0002]
In order to address a reduction in communication quality attributed to a sharp recent increase in mobile traffic and to provide faster high-speed communication, the 3GPP LTE (Long Term Evolution) has examined standardization of the carrier aggregation (Carrier Aggregation: CA) function in which a radio base station (eNode B: eNB) communicates with a radio terminal (User Equipment: UE) using a plurality of cells. Note that, cells that a UE can use in CA are limited to cells of a single eNB (i.e., cells operated by a single eNB). [0003]
The CA procedure will be described with reference to Fig. 17 (Non Patent Literature 1). Fig. 17 shows an example in which a UE performs CA of a first cell (Celll) and a second cell (Cell2) both operated by an eNB. In Step SI, the UE establishes a radio connection with the eNB on the first cell (RRC Connection Establishment). In Step S2, the UE receives downlink data from the eNB through the first cell (Downlink data on Celll). Here, for the UE, the first cell is the primary cell (Primary cell: PCell). [0004]

In Step S3, the eNB determines that it is necessary to configure a secondary cell (Secondary cell: SCell) for the UE, and configures a second cell as the SCell through the PCell (RRC Connection Reconfiguration on Celll (including Configuration of Cell2 (Secondary cell: SCell)). In Step S4, the UE sends a completion notification to the eNB in response to completion of configuration of the second cell, that is, in response to completion of preparation of using the second cell (RRC Connection Reconfiguration Complete). [0005]
In Step S5, the eNB sends to the UE a notification of second cell use initiation (Cell2 Activation). In Step S6, the UE receives downlink data by simultaneously using the first and second cells (DL data on Celll and Cell2). Note that, the UE in Step S6 is just required to be capable of simultaneously using the first and second cells for downlink data reception. In other words, the UE is not required to constantly receive downlink data on both the first and second cells. Whether to use one of the first and second cells for downlink data reception or to use both of them is determined, for example, based on downlink data quantity or a service that the UE uses. The case where the UE transmits uplink data on the second cell can also be basically carried out by using a procedure similar to that shown in Fig. 17. [0006]
Though the UE that performs CA has functions of a Physical layer and at least part of a MAC (Medium Access Control) layer for each of the aggregated cells, the UE has the same structure of the RLC (Radio Link Control) and higher layers as in the case where CA is not performed. Accordingly, the core network (Evolved Packet Core: EPC) does not know whether or not the UE is performing CA. [0007]
Further, about a heterogeneous network (HetNet) environment, there is proposed a concept of Inter-eNB CA in which cells operated by different eNBs are aggregated (Non Patent Literature 2). For example, in Inter-eNB CA, it is considered to use a macro cell operated by a

macro base station (Macro eNB: MeNB) and a pico cell operated by a
pico base station (Pico eNB: PeNB).
[0008]
Still further, there is also proposed a method in which a macro cell with wide coverage is used for transmission and reception of signals related to control such as UE mobility management, and a pico cell which has relatively good communication quality is used for transmission and reception of signals related to data such as user data (Non Patent Literature 3). Citation List Non Patent Literature [0009]
[Non-Patent Literature 1] 3GPP TS 36.331 Vll.0.0, "Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification". Section 5.3.5, July 2012
[Non-Patent Literature 2] 3GPP RWS-120046, Samsung Electronics, "Technologies for Rel-12 and Onwards", 3GPP TSG RAN Workshop on Rel-12 and Onwards Ljubljana, Slovenia, 11-12 June 2012 [Non-Patent Literature 3] 3GPP RWS-120010, NTT DOCOMO, "Requirements, Candidate Solutions & Technology Roadmap for LTE Rel-12 Onward", 3GPP TSG RAN Workshop on Rel-12 and Onwards Ljubljana, Slovenia, 11-12 June 2012 Summary of Invention Technical Problem [0010]
In the conventional carrier aggregation (CA), since a radio terminal (UE) communicates through cells operated by a single radio station (eNB), the UE can configure the cells accordingly. Meanwhile, in carrier aggregation of cells operated by different eNBs (i.e., Inter-eNB CA), in order to simultaneously use the cells operated by different eNBs, the UE is required to perform cell configuration for performing communication (e.g., either or both of RRC Connection Setup and RRC Connection Reconfiguration) in each of the cells. Under the current LTE specification, however, when a UE has established a radio

connection on a cell of one eNB, the UE cannot establish any radio
connection on a cell of another eNB.
[0011]
Accordingly, one object of the present invention is to provide a radio communication system, a radio station, a radio terminal, a communication control method, and a program which contribute to enabling a single radio terminal to establish radio connections with cells of a plurality of radio stations, in order to achieve carrier aggregation of cells operated by different radio stations. Solution to Problem [0012]
In a first aspect, a radio communication system includes a first radio station that operates a first cell and a second radio station that operates a second cell. While a first radio connection on the first cell with a radio terminal is established, the first radio station requests or instructs the second radio station to prepare for communication with the radio terminal on the second cell. Further, the first radio station instructs the radio terminal or the second radio station to establish a second radio connection on the second cell between the second radio station and the radio terminal, while maintaining the first radio connection. [0013]
In a second aspect, a first radio station that operates a first cell includes a communication control unit that controls communication with a radio terminal having established a first radio connection on the first cell. While the first radio connection on the first cell with the radio terminal is established, the communication control unit requests or instructs a second radio station to prepare for communication with the radio terminal on the second cell. Further, the communication control unit instructs the radio terminal or the second radio station to establish a second radio connection on the second cell between the second radio station and the radio terminal, while maintaining the first radio connection. [0014]

In a third aspect, a second radio station that operates a second cell includes a communication control unit that controls communication with a radio terminal. While a first radio connection with the radio terminal is established on a first cell operated by a first radio station, the communication control unit prepares for communication with the radio terminal on the second cell in response to an instruction or a request from the first radio station. Further, the communication control unit establishes, in response to an instruction from the first radio station, a second radio connection on the second cell between the second radio station and the radio terminal while the first radio connection is maintained. [0015]
In a fourth aspect, a radio terminal includes a radio communication unit and a control unit. The control unit configures the second cell while maintaining the first radio connection with the first radio station, in response to an instruction from the first or second radio station according to the first, second, or third aspects. [0016]
In a fifth aspect, a communication control method in a first radio station that operates a first cell includes:
(a) requesting or instructing a second radio station, which operates a second cell, to prepare for communication with a radio terminal on the second cell, while a first radio connection on the first cell between the first radio station and the radio terminal is established; and
(b) instructing the radio terminal or the second radio station to establish a second radio connection on the second cell with the radio terminal, while maintaining the first radio connection.
[0017]
In a sixth aspect, a communication control method in a second radio station that operates a second cell includes:
(a) preparing for communication with a radio terminal on the second cell in response to an instruction or a request from a first radio

station, while a first radio connection with the radio terminal on a first cell operated by the first radio station is established; and
(b) establishing, in response to an instruction from the first radio station, a second radio connection on the second cell between the second radio station and the radio terminal while the first radio connection is maintained. [0018]
In a seventh aspect, a communication control method in a radio terminal includes configuring the second cell while maintaining the first radio connection with the first radio station, in response to an instruction from the first or second radio station according to the first, second or third aspects. [0019]
In an eighth aspect, a program includes instructions for causing a computer to perform the communication control method in the first radio station according to the fifth aspect. [0020]
In a ninth aspect, a program includes instructions for causing a computer to perform the communication control method in the second radio station according to the sixth aspect. [0021]
In a tenth aspect, a program includes instructions for causing a computer to perform the communication control method in the radio terminal according to the seventh aspect. Advantageous Effects of Invention [0022]
According to the aspects described above, it is possible to provide a radio communication system, a radio station, a radio terminal, a communication control method, and a program which contribute to enabling a radio terminal to establish radio connections with cells of a plurality of radio stations, in order to achieve carrier aggregation of cells operated by different radio stations. Brief Description of Drawings [0023]

Fig. 1 is a diagram showing a configuration example of a radio communication system according to a first embodiment;
Fig. 2 is a diagram showing a configuration example of a first radio station according to the first embodiment;
Fig. 3 is a diagram showing a configuration example of a second radio station according to the first embodiment;
Fig. 4 is a diagram showing a configuration example of a radio terminal according to the first embodiment;
Fig. 5 is a flowchart showing an example of an operation of the first radio station according to the first embodiment (first exemplary procedure);
Fig. 6 is a flowchart showing an example of an operation of the second radio station according to the first embodiment (first exemplary procedure);
Fig. 7 is a flowchart showing an example of an operation of the radio terminal according to the first embodiment (first exemplary procedure);
Fig. 8 is a sequence diagram showing an example of a communication control method in the radio communication system according to the first embodiment (first exemplary procedure);
Fig. 9 is a flowchart showing an example of an operation of the first radio station according to the first embodiment (second exemplary procedure);
Fig. 10 is a flowchart showing an example of an operation of the second radio station according to the first embodiment (second exemplary procedure);
Fig. 1 1 is a flowchart showing an example of an operation of the radio terminal according to the first embodiment (second exemplary procedure);
Fig. 12 is a sequence diagram showing an example of a communication control method in the radio communication system according to the first embodiment (second exemplary procedure);

Fig. 13 is a sequence diagram showing an example of a communication control method in a radio communication system according to a second embodiment (third exemplary procedure);
Fig. 14 is a sequence diagram showing an example of a communication control method in the radio communication system according to the second embodiment (fourth exemplary procedure);
Fig. 15 is a diagram showing a configuration example of a radio communication system according to a third embodiment;
Fig. 16 is a sequence diagram showing an example of a communication control method in the radio communication system according to the third embodiment; and
Fig. 17 is a sequence diagram showing a carrier aggregation procedure in LTE (Background Art). Description of Embodiments [0024]
Hereinafter, specific embodiments will be explained in detail with reference to the drawings. The same or corresponding components are denoted by the same reference symbols throughout the drawings, and repetitive explanations will be omitted as necessary for the sake of clarity. [0025] First Embodiment
Fig. 1 shows a configuration example of a radio communication system according to the present embodiment. The radio communication system according to the present embodiment includes a first radio station 1, a second radio station 2, and a radio terminal 3. The radio stations 1 and 2 operate a first cell 10 and a second cell 20, respectively. The radio stations 1 and 2 are, for example, a radio base station or a base station controller. The radio terminal 3 is configured to establish a second radio connection on the second cell 20 while maintaining a first radio connection on the first cell 10. This allows the radio terminal 3 to simultaneously use a plurality of cells (e.g., the cells 10 and 20) for transmitting or receiving any signal (e.g., user data or control information). In other words, the radio terminal 3

10 su pp orts c arri er a ggr egat ion of ce ll s operat ed b y di f f erent rad io st at ion s. [ 0026]
Note t hat , Fig. 1 sho ws a Het Ne t enviro nm ent . Sp ecifi cal l y, t he
5 fi rst cell 1 0 sho wn i n Fi g. 1 has a wi de r co vera ge area th an the s eco nd
cell 2 0 do es . Furth er, Fi g. 1 s how s a hi erarch ic al cel l s truc tu re in which the se cond cel l 20 is arran ged i n t he first c el l 10. Ho wev er, t he cell stru cture sh own in Fi g. 1 i s m erel y an ex am ple . For ex ampl e, t he fi rst and s eco nd c ells 10 and 20 may ha ve eq uiv ale nt cov era ge areas.
10 In ot her w ords , th e radio comm unicatio n s yst em accordin g to t he
present embodiment may be applied to a homogeneous network envi ro nme nt . [ 0027]
In o rd er t o enable th e radio t ermin al 3 to sim ul tan eo us ly u s e th e
15 cells 10 and 20 , w hi ch a r e ope r ated b y th e d iffe ren t ra dio st ati ons 1
and 2 , for sign al tra nsmi ssio n or recepti on, t he r adio commu ni cation s ys tem of th e p r es ent em bodi me nt i s r eq uire d to esta bl is h a rad i o conn ect ion wit h th e radio t ermi nal 3 on ea ch of th e cell 1 0 and t he c ell 20. To th is en d, th e radio comm un icatio n s yst em a cc ordin g t o t he
20 pres ent emb od iment op erates i n t he foll owi ng man ne r . T hat i s, i n
order t o enable t he radio t ermin al 3 to sim ul tan eo usl y us e th e c ell s 1 0 and 20 fo r sign al t r ans miss ion o r rece pti on, th e rad io s tati on 1 is confi gure d to requ est o r i ns truc t t he ra di o st ati on 2 to prep are for commu nic ati on wi th th e r adio t ermi nal 3 on th e cel l 20 , whi le a first
25 r adio con ne ct ion wi th th e ra dio t ermin al 3 on the c el l 10 is e stablish ed.
F urt her, th e radio st at ion 1 i s co nfig ured to i ns truct th e rad io t ermi nal 3 o r t he ra di o st ation 2 to es tablish a s econd r ad io c onn ecti on on t he cell 2 0 wit h th e ra dio term ina l 3 , w hil e m aint ain i ng th e fi rst ra dio conn ect ion . Th us, ac co rdin g to t he p r esent embo dim e nt , th e radi o
30 t ermin al 3 c an est ablish a r adi o con ne ction o n ea ch of th e cells 10 and
20 fo r a chievin g c arri er aggr e gatio n o f the cel ls 10 and 2 0 operate d b y t he d i fferen t radi o s tati ons 1 and 2. No te t hat, the expressio n "to simul taneo us l y u s e c el ls " is not lim ite d t o the man ner of simul taneo us l y rec eivin g or tra nsmit tin g sign al s a ct ua lly o n the cel ls .

11
In st ead , it in clu de s the m an ne r of r ec eiv i ng or tra nsmi ttin g sign als
actu all y o n an y o ne o f t he cell s al th ough the r ad io t erminal 3 can
r ecei ve o r t ransmi t sign als on b oth of th e cell s, th e m ann er of
r ecei vin g or t ransmit t i ng sign als o f di fferent t ypes o n the res pe ctive
5 cells, or the m ann er of u si ng e ach o f t he c ell s for on e of sign al
r eceptio n or t ransmiss i on. [ 0028]
In a fi r st ex em pla r y pro cedu r e, th e ra dio st ati on 1 instru cts th e r adio te r mi n al 3 to es tab lish the s econd radi o con nec ti on on t he c el l 2 0.
10 Th en, the r adio t ermin al 3 co nfi gures t he cell 20 i n res ponse to t he
i nst ructi on from th e radio st ati on 1 . Thus, the r adio t ermin al 3 can es t abli s h t he second radio c onn ecti on w it h the r adi o stat ion 2 on t he cell 2 0. T he rad io s t ati o n 1 m a y s en d the i nstru cti on t o t he radio t ermin al 3 via a co ntrol co nn ectio n ( e.g., a con trol ch ann el, or a
15 si gn ali ng radi o be are r (Sign ali ng R adi o Be arer: SR B )) b etw ee n th e
r adio sta ti on 1 and t he radi o termin al 3 on t he cell 10 . Thu s, t he ra dio t ermin al 3 can eas il y pre pa re for co m mu ni cati on o n the cell 20 of th e r adio sta ti on 2 w hil e comm uni catin g wit h t he ra dio station 1 (i.e., while pe r fo rmi ng on e o r both of t ransmiss i on an d re cepti on o f s ign als
20 ca rr yin g user data o r the l ike ) .
[ 0029]
In a se co nd e x emp lary pro ce du re, the rad io s tat io n 1 inst ructs t he rad io st atio n 2 to establish th e s ec ond rad io c onnectio n on th e ce l l 20. Th e r adio sta tio n 2 i ns truc ts th e rad io t ermi nal 3 t o est abl is h th e
25 s econ d r adi o conn ect ion on t he cell 20 i n res pon s e t o t he in st r uct ion
f r om t he ra di o s tat ion 1. Th en , the r adi o t ermin al 3 co nfigu r es th e c ell 20 i n respo ns e to th e in st r uct i on from th e radio st at io n 1. Thus, th e r adio t erminal 3 c an e stablish t he s ec ond rad io c onn ectio n with t he r adio sta ti on 2 o n the cell 2 0. He r e, t he s ec ond rad io c onnectio n
30 es t abli s hme nt i nst ructi on from th e radi o st ation 1 to t he radio stati on 2
m a y be s ent si mult an eousl y wi th an i ns tructi on (or a reque st ) to prepar e for comm uni ca t i on with th e r adi o t ermin al 3 o n th e cell 20. Al tern ati vel y, t he instru cti on (o r th e req uest) to p r ep are fo r th e communication may double as the second radio connection

12
es t abli s hme nt i nst ructi on. In o th er wo r ds, t he messa ge i ns truc t i ng o r
r equest ing t o prep are for co mmut ation on t he cell 20 with t he rad io
t ermin al 3 m a y ex pli citl y o r i m pli citl y ind ic at e t he se con d radio
conn ect ion est abli sh m ent in st r uctio n from the r adi o station 1 to t he
5 r adio sta ti on 2. T hat is, up on receiv ing the i nstruct ion (o r a requ es t )
t o p rep are for co mmu ni cation with th e rad io t ermi nal 3, th e r adi o st at ion 2 m a y prepa r e fo r t he c ommu nic ati on with t he radi o te rmin al 3 and al s o instru ct th e radio t erm inal 3 to est abli s h th e se cond radio conn ect ion . Th e inst ruction f rom t he r adio s tat ion 2 to th e radi o
10 t ermin al 3 m ay b e sen t from t he rad io st a tion 2 to t he radio t erm inal 3
vi a a cont r ol con ne ct i on (e. g. , a con tr ol ch ann el o r a s ign aling radio be arer) bet ween the r ad io s tat ion 1 a nd t h e radio t ermin al 3 on th e c ell 20. Fu rt he r, in o r de r to enab le the radio t erm inal 3 to receiv e th e i nst ructi on s ent from t he radi o s t ati on 2, t he ra dio s tation 1 may s en d,
15 t o the radio t erm in al 3 vi a a co ntrol conn ect ion on t he c el l 10 , radio
r eso urce co nfi gura tion in fo r mat i on r equ ired for re ce pt ion on t he cell 20. [ 0030]
Note t hat , in th e pre sen t sp ec i fi catio n, "e st ablishi ng a radio
20 conn ect ion " m ean s , f or ex ampl e, th at a ra dio term ina l and a rad io
st at ion becom e c ommun ic abl e with e ac h ot he r , o r th at a radio t ermin al and a radio st ation sh are in f orm ati on r equired f or com muni ca ti on wi th ea ch oth er. Fu rt he r , "con fi gu r i ng a cel l at a ra dio termina l" mean s, for ex am ple, t hat a c ell b ec om e s a va i l ab le at a r adio t ermin al, o r t hat a
25 r adio t erminal compl et es p r eparatio n f or u si ng a cell . Stil l f urt her,
"p repari ng at a r ad io s tat i on for co m muni ca tion wi th a radi o te rmin al " m ean s , for ex am pl e, tha t a ra di o st at ion r et ai ns in f orm atio n req ui red f or a r adio conn ec tion wit h a r adi o t ermin al , tha t a ra dio s tat ion generat es i nform atio n requi r ed for a ra di o co nne cti on with a radio
30 t ermin al, t hat a r adio sta ti on p ermit s a ra di o co n ne cti on w ith a rad io
t ermin al, or t hat a rad i o st atio n i s i n a st ate r ea d y t o acc ept commu nic ati on with a r adi o t ermin al . [ 0031]

13
In th e first and se cond exe mpl ary p r o ced ures desc r i bed abov e,
t ermin al in di vidu al i n fo rm ati on o f t he r adio ter min al 3 r ela t i ng to
es t abli s hme nt o f t he firs t or s econ d ra dio co nne cti on ma y b e sent from
t he rad io st atio n 1 to the r adi o statio n 2, o r from th e ra dio st ati on 2 to
5 t he rad io st atio n 1. Fu rt he r, i n th e f ir st and s ec ond ex em pl ar y
procedure s , at l east one of r adi o con ne ct io n con fi gura tion in f orma ti on
and radio a ccess in fo rm atio n r elat ing to est abli s hment o f t he firs t or
s econ d r adi o conn ect ion may be sent f ro m th e radio s t atio n 2 t o th e
r adio sta ti on 1, o r from th e r adio st atio n 1 t o the radio stat io n 2.
10 [0032]
The t ermi n al i ndi vid ual in fo r mat ion o f th e radi o te rmi nal 3 r el ati ng to est abli sh m ent o f t he firs t or seco nd ra di o con ne ct ion m a y i nclu de a t l east o ne o f th e in form ation el em ents listed be low :
- r ad io te r mi nal ca pab i l it y in f orm ati on ; 15 - r ad io te r mi nal i de nti fier i n fo rm atio n;
- sel ect ed n et wo rk i nformati on ;
- b earer i nformat ion ;
- r ad io reso urce cont ro l in f orma t i on ;
- r ad io te r mi nal m obilit y hi st ory i nfo rm at ion ; and 20 - servi ce i nformat ion .
[ 0033]
The radi o conn ection confi gurat io n in fo r m atio n r el at ing to
es t abli shment of t he fi rst o r s econd r adio c onn ecti on ma y i ncl ude at
l east on e o f the i nfo rmat ion el e m ent s li sted bel ow:
25 - servi ng c ell in fo rm ation ;
- s yst em i nformat ion ;
- r ad io reso urce confi guratio n in formatio n ;
- m easure men t con fi gura ti on in f orm atio n ;
- m ob ilit y c ont rol in f orm atio n ; and 30 - securit y c onfi gurat ion in fo r mat io n .
[ 0034]
The radi o access in fo rm atio n r elat ing to est abli s hm ent o f t he fi rst or se cond ra dio co nn ect ion may i ncl ud e at le ast o ne o f t he i nformat ion el em ent s listed bel ow:

14
- r ad io a cc ess i den tifie r in fo r mat ion ; and
- r ad io a cc es s reso urc e in forma ti on . [ 0035]
The fi r st and s ec ond ex em pla r y pro c edu r es m a y be ap plied to
5 va riou s a ppli cati on s in cl udi ng, but n ot limi t ed to , a n app lic ati on wh ere
t he first radio st ation 1 i s a r ad io sta t io n t hat operates (m an ages ) a cell w ith re l ativ el y l arge co ve rage a nd t he s ec ond rad io sta t i on 2 is a low power radio station (Low Power Node: LPN) that operates (manages) a cell with small coverage. The LPN may be, for example, a
10 r adio sta ti on h avin g simi lar f unc ti ons as t he radio st ati on 1, or m a y b e
a new type network node (New Node) with reduced functions as comp ared with th e rad io st atio n 1 . Fu rt her, t he se cond cel l m a y be a ne w t yp e c ell (N ew C ell T ype ) bei ng di f f erent f ro m a con ve ntion al cell, i .e., th e second ce ll m a y use a ne w t yp e c arrier ( Ne w Carri er T ype)
15 bein g diffe rent fr om a co nv enti onal ca r ri er.
[ 0036]
In th e foll owin g, con f i gurat ion ex am pl es o f t he radi o s t atio ns 1 and 2 and the radi o t e rmin al 3 a cco r din g to t he p r esent embo di men t wi ll be d escribed . Fi g. 2 is a b lock di agram sh owing a co nfigu r atio n
20 ex am ple of t he fi r st rad io s t atio n 1. A radi o comm uni cat ion uni t 11
r ecei ves an u pl ink si gnal tra nsmi tted from the r adi o t ermin al 3 vi a an antenna. A recep tio n d ata proc essin g unit 13 r ec ons t ruct s an y r ec eiv ed uplink si gnal. T he o bt ain ed r ecep tion dat a i s t r ans ferre d to, v ia a commu nic ati on unit 1 4, ot he r n et wo rk nod e, e. g. , a data t ransfe r rin g
25 apparatu s o r a mo bilit y m an age ment app arat us i n a n upper net work, or
ot her ra dio s tati on . For ex amp l e, t he upl ink u s er d at a r ec ei ved f r om t he rad io t e rmi nal 3 i s trans f erred t o the data tran s ferri ng app ara tus i n t he up pe r n et wo rk . Furth er, N on-A cc ess -S trat um (NAS ) con tr ol dat a out o f t he co ntrol d ata r ec ei ved f r om t he ra dio term ina l 3 i s t r ansferred
30 t o t he m obili t y ma nagemen t app arat us i n t he u pper n etwo rk . Fu rt her,
t he recep tion d ata processin g unit 1 3 re ceiv es , f r om a commu nic ation cont ro l unit 15 , control d at a to be t r ans mitt ed to th e ra dio st ati on 2, and se nds t he cont r ol d at a to t he radio stat ion 2 v i a th e comm uni catio n unit 14 .

15 [ 0037]
A t ransmissi on d ata p ro cessin g unit 12 r ec ei ves us er d at a
des tin ed f or t he radio t erm ina l 3 fro m t he commu nic ati on unit 1 4, and
generat es a t ransp ort chann el b y per f ormi n g erro r - corre ct ion cod i ng,
5 r at e matc hi ng, int erl e avi ng or th e l i ke. Further, t he t rans miss ion data
processin g unit 1 2 ad ds cont ro l i nforma ti o n to t he data seq ue nc e of the t r anspo rt chan nel t o generat e a tran s mis si on s ym bo l se que nce. Th e r adio commu ni cation unit 11 p erforms proc es s es su ch as car r ier wav e m odul atio n b as ed on t he trans missio n s ym bo l seq ue nce, f r equ ency
10 conv ers ion , si gnal am pl ificatio n o r t he lik e to ge nerate a downl ink
si gn al (d ownlin k s ign al ), a nd t r an sm its t he gene r at e d d own link s ign al t o t he ra di o term in al 3. Fur th er, th e tr ansmission da ta pro cessin g u nit 12 receiv es, fro m the commun ic atio n cont r ol unit 1 5 , con trol dat a t o be t r ansmitt ed to th e ra di o te rm inal 3, a nd s en ds t he r ecei ved cont ro l dat a
15 t o t he ra di o term in al 3 via t he rad io c om muni cation un it 11.
[ 0038]
In o rd er t o enable t h e radio t ermi nal 3 t o sim ul tan eo us ly us e th e cells 10 and 20 fo r r ecep tion or t ransmiss i on o f u s er d ata , t he commu nic ati on co ntrol uni t 15 ex ch anges si gna l s wit h th e r adi o st atio n
20 2 and th e radi o te r minal 3 . That i s, th e commu nic atio n con trol unit 15
s ends, t o the r adi o st atio n 2 v ia th e comm uni ca t i on un it 14 , a me ssa ge r equest ing or inst r uctin g pre pa r ati on fo r co mmu nic at ion with th e radi o t ermin al 3 on the cel l 2 0. Furt her, th e commu nic ati on con trol unit 15 s ends a messa ge i nst ructi ng establish ment o f th e se cond r adio
25 conn ect ion on t he c el l 20 to the rad io t ermi nal 3 or t he r adio s tat ion 2
vi a th e r adi o com muni cati on un it 1 1 or th e comm uni catio n uni t 14. S t i ll f urth er, in t he cas e of th e fi r st ex em plar y p ro cedu r e, th e commu nic ati on co ntrol uni t 15 s end s , to t he rad io te rm inal 3, th e rad io conn ect ion co nfig uratio n info rm atio n r el at ing to the cell 2 0 op erat ed
30 b y the radio stat ion 2 . Th e rad io co nnecti on con f igu r ation i nformat ion
m a y be sent b y t he sa me messa ge a s a n instruct ion for e stablishi ng a r adio con nection , or m a y be s ent b y a separ ate message . In the case o f t he s econd exem pla r y pro cedu r e, th e co mmuni cat ion control u ni t 15

16 m a y sen d, t o th e r adio t ermin al 3, the rad io reso urce c onfi gu ratio n i nformat ion rel ati ng t o th e ce ll 2 0 op erated b y t he r adio s tat ion 2 . [ 0039]
F i g. 3 i s a bl ock dia gram sho wi ng a con f i gurat ion ex ampl e o f th e
5 s econ d r adi o station 2. T he fu nctio ns and op erat ion s of a radi o
commu nic ati on unit 2 1, a t r ansmi ss ion dat a p roc es si ng uni t 22, a
r eceptio n data proc ess in g uni t 23, and a co mm uni cati on uni t 2 4 sh ow n
i n Fi g. 3 a r e id ent ical t o th os e of th e corresp ond in g el eme nts o f t he
r adio sta ti on 1 sho wn in Fig. 2 , i. e., the rad io c om muni cat ion uni t 11,
10 t he trans mi ssio n dat a process in g uni t 12, t he re ce pt ion d at a proces si ng
unit 13 , a nd the commu ni cati on unit 14. [ 0040]
The com muni cati on c ontrol u nit 25 o f t he radi o s tatio n 2 r ecei ves, from th e r adio sta tion 1, a mess age r equ est ing o r i nstru cti ng
15 prepar ati on for co mmun i cati on wit h th e rad io t ermi nal 3 on th e c el l 20,
and confi gures t he r adi o commu nic at ion unit 21 based on t he m ess age , t hereb y p repar ing f or commu nic ation w ith th e r adi o t ermin al 3 o n th e cell 2 0. In th e c as e o f t he se cond exem plar y p r oc edure, th e commu nic ati on co ntrol uni t 25 s end s , to th e rad io t erm inal 3, radio
20 conn ect ion co nfi gu r atio n in f orma t i on re lat i ng to th e cel l 20 op erat ed
b y the radio stat ion 2 . Th e rad io co nnecti on con f igu r ation i nformat ion m a y be sent b y t he sa me messa ge a s a n instruct ion for e stablishi ng a r adio conn ecti on o r m a y b e t r ansmitt ed b y a sepa r at e m ess age. [ 0041]
25 F i g. 4 i s a bl ock dia gram sho wi ng a con f i gurat ion ex ampl e o f th e
r adio t erminal 3. A r adio comm unicatio n unit 3 1 s uppo rt s c arrier aggre gat ion of cells operate d b y d ifferent r adio stat ion s, and i s ca pabl e of s im ulta n eous l y usin g t he c ells (e.g . , th e cel ls 1 0 and 2 0) f or si gn al t r ansm is si on o r recep tion . S pe cificall y, t he radi o
30 commu nic ati on unit 3 1 receive s d ownli nk si gnals f r om o ne o r b ot h of
t he rad io st atio n 1 an d t he ra di o s tat ion 2 vi a a n an ten na. A r ec eptio n data p r oc essin g un it 32 rec o ns tructs re ce pti on d ata fro m an y recei ve d downl ink signal a nd s en ds t he recep tion data t o a dat a co ntrol un it 33 . Th e dat a co nt rol u nit 33 use s the recepti on dat a a cc ord ing to th e

17
purpose t h ereof . A t r ansm is si on d at a pro cessi ng u nit 34 and th e radio
comm unicati on unit 3 1 gen erat e an uplin k si gnal u si ng tran smi s si on
data su ppli ed from th e d ata con t ro l unit 33, and t r ans mit t he upli nk
si gn al to one o r bo th o f t he r adio s tat ions 1 and th e radi o st ati on 2.
5 [ 0042]
In o rd er t o enable th e radio com m unicati on un i t 31 t o simul taneo us l y u s e th e cell s 1 0 and 20 t o be s imul tan eousl y u s ed at th e r adio commu ni cation unit 31 , a commu nic ation con trol uni t 35 o f th e r adio t erminal 3 c onfi gu res t he cell 20 i n res pon s e to an in stru ctio n
10 f r om t he ra di o s tat ion 1 or th e radio st ation 2 . Thu s, th e r adio
t ermin al 3 can commu ni cate with th e rad io st atio n 2 also w hil e commu nic ati ng with t he radi o s tatio n 1 ( i.e. , w hil e perfo rmi ng on e or both o f t r ansm is si on and rec eptio n of s ignal s carr yi n g us er da t a or th e l i ke).
15 [0043]
In th e foll owi ng, a des cript io n wil l be giv en o f ex ampl es o f a procedure for e stablishi ng radi o co nnectio n s wi th t he r adi o t ermin al 3 on both t he c ell s 1 0 an d 20 in order to e nabl e t he radi o te r mi nal 3 t o simul taneo us l y u s e th e cell s 1 0 and 20 . Fi rs tl y, th e fi rs t exe mpl ary
20 procedure will be d es cribed wit h refere nc e to Figs. 5 t o 8, and
t hereafte r th e s ec ond ex em pla r y pro c edu r e wi ll be d es crib ed wit h
r eferenc e t o Figs. 9 to 12.
[ 0044]
( F i rst Ex em plary Pr oc edure)
25 F i g. 5 i s a flo wc ha rt sho win g a n op eratio n of th e r adio st at ion 1
ac cordin g t o the fi rst ex emp la r y pro ce dure . In S te p S1 01, th e radio st at ion 1 ( commu nic ati on co ntrol uni t 15) requ ests or i ns truc ts th e r adio sta ti on 2 to prepare for comm unicat ion (i . e. , on e o r bot h of t r ansmission an d re ce pt ion o f sign als ca r r yin g use r d ata o r t he lik e) on
30 t he cell 2 0 wi th th e radio t ermin al 3 b elongi ng to th e it s o wn cell 1 0.
In St ep S 1 02, t he ra di o st ati on 1 det ermines whe the r an
ac kn owl ed gem ent to t he req uest or inst ru ction i n S te p S101 h as be en r ecei ved from th e ra di o st ation 2. As h as be en descr ibe d, in t he firs t ex em plar y p ro cedu r e, th e ra dio st ati on 1 d i rectl y i ns truct s t he radi o

18
t ermin al 3 to est ab li sh t he se cond radio c onnecti on on th e c el l 20.
Accordingly, when the acknowledgement has been received (YES in
S t ep S 10 2), the radio sta t i on 1 s end s an in stru ctio n fo r es tab lishing th e
s econ d r adi o conn ect ion to t he radi o te rm in al 3 (St ep S1 03). On the
5 other hand, when no acknowledgement has been received (NO in Step
S 102), the radio stat i on 1 do es n ot in st r uct est abl ishm ent of th e secon d r adio conn ecti on a nd e nds the pro ces s shown in Fi g. 5. [ 0045]
F i g. 6 i s a flo wc ha rt sho win g a n op eratio n of th e radio st at ion 2
10 ac cordin g t o the fi rst ex emp la r y pro ce dure . In S te p S2 01, th e radio
st at ion 2 ( commu nic ati on co ntrol uni t 25) receiv es, from th e radio st at ion 1 , a m es s age in st r uct ing or re que stin g pre parat ion fo r commu nic ati on on th e c el l 20 wi th the r adio ter min al 3 bel ongin g to t he cell 1 0. In Ste p S2 02, th e radio st at ion 2 det erm in es wh et her o r
15 not to accept t he i ns tru cti on or r equ est fro m the radio st atio n 1. Fo r
ex am ple, i f t he r adio sta ti on 2 c an not pre pa r e ra dio reso urc e fo r commu nic ati on with t he radi o te rmi nal 3 be ca use of high lo ad o f t he cell 2 0, t hen the radi o station 2 m a y rej ect th e inst ru ctio n or r equ es t f r om t he ra dio s tat ion 1. Th e radi o s tati on 2 se nds a n egati ve
20 ac kn owl ed gem ent to t he radi o s tatio n 1 wh en rej ect ing th e inst ruct ion
or reque st f rom t he r adio s tat i on 1 (St ep S 203 ) , a nd s end s an ac kn owl ed gem ent to t he radi o s tatio n 1 wh en a cc epti ng the i nst ru ctio n or reque st (St ep S20 4). Wh en t he radi o st ation 2 a c c ept s th e i nst ructi on or req ue st from th e radi o st at ion 1 , t he radi o st ation 2
25 prepar es f or comm uni catio n w ith th e rad io t ermi nal 3 on th e c el l 20.
[ 0046]
F i g. 7 i s a flo wc ha rt sho win g a n op erati on o f th e rad io termi nal 3 accordi ng t o th e fi r st ex em pl a r y pr oc edure. In S tep S301 , the r adi o t ermin al 3 (com muni ca t i on contro l u nit 35 ) recei ve s an i ns tructi on for
30 es t abli s hin g t he s econ d rad i o con ne ction fro m the first radio st atio n 1 .
In St ep S 3 02, t he radi o te rmin al 3 c onfi gures t he cel l 20 i n respo ns e to t he inst ru ction in St ep S 301 , a nd esta bli s hes th e s econ d r adi o conn ect ion on t he c el l 20 w ith the r adi o station 2. In St ep S 303 , th e

19 r adio t erminal 3 noti fi es t he r ad io stat ion 1 o f c om pletio n of t h e s econ d r adi o conn ect ion est abli shm ent o n t he cell 2 0. [ 0047]
F i g. 8 i s a seq ue nc e diagr am showi ng t he ent ire fi rs t ex emp lary
5 procedure . In Ste p S 401, th e f i rst ra dio st ati on 1 an d the r ad io
t ermin al 3 e stablish the fi r st r ad io c onn ectio n on th e fir st cel l 10. In S t ep S40 2, th e ra dio stat ion 1 commun ic at e s w ith the r adi o t ermin al 3 on t he cel l 10 . In t he ex amp le of Fig . 8 , the r adi o station 1 t ransmit s on t he cel l 10 dow nlin k d ata des tin ed fo r th e radi o te r mi nal 3 .
10 [0048]
S t eps S40 3 to S 40 6 sh ow a p r oc ed ure fo r es tab li sh in g the s econd r adio conn ecti on o n t he cell 2 0 fo r t he radi o te rm inal 3 , whi ch is commu nic ati ng on th e c el l 10. T hat is, i n St ep S4 03, t he r adio s tat ion 1 requ est s o r in st r ucts the r adi o station 2 to pr ep are for co mmun ic at io n
15 wi th th e r ad io te r mi nal 3 o n t he cell 2 0 . In S tep S 404 , th e r adi o
st at ion 2 sends a respon s e t o the r eq ues t or ins truction in St ep S4 03 to t he rad io st atio n 1. The r es ponse i s a n ack now led gement or a negat ive acknowledgement. When sending an acknowledgement in Step S404, t he rad io st atio n 2 prep ares fo r com muni cati on with th e rad io t ermi nal
20 3 on the cel l 20 bas ed on th e r eq ues t or inst ruct ion from th e radio
st at ion 1. In S te p S 405, i n re sp on s e t o re ce i ving t he a ckno wle dge m ent , t he rad io st atio n 1 s end s , to t he r adi o t ermin al 3 on th e cel l 10 , an i nst ructi on f or es ta bli s hin g t he se co nd radi o conn ectio n on the cel l 2 0. In St ep S 4 06, t he ra di o term ina l 3 con f igures th e c el l 20 b as ed on th e
25 i nst ructi on from th e radio st ati on 1 . Thus, the r adio conn ectio n
between th e radi o st at ion 2 and th e ra di o term ina l 3 i s e st ablish ed on t he cell 2 0. [ 0049]
B y co mpl etion o f Step S40 6, the radio t erm in al 3 c an
30 simul taneo us l y u s e th e cell s 1 0 and 20 . A cco rd ingl y, in St ep S40 7, f or
ex am ple, t he radi o te rmin al 3 r ecei ves do wnlin k d at a at bo th o f th e cells 10 and 20 . No te th at, the radio t ermi nal 3 in S tep S407 is just r equi red to be capa bl e of s imul t aneousl y usin g the cell s 10 and 20 f or commu nic ati on (per f or mi ng on e o r bot h of recepti on a nd t r ansmi ss ion

20
of sign als c arryi ng u ser d at a or the l ik e). In other words, t he ra dio
t ermin al 3 is n ot re quired t o const an tl y r eceiv e do wnlink dat a or
t r ansmit u pl ink d ata at both of the firs t an d secon d c ell s. W h ether t o
us e o ne o f th e cell s 10 and 20 for us er da ta recept ion or tra ns mi ssio n
5 o r to us e b ot h of th em i s d et ermi ned , for ex amp l e, base d on us er d at a
quant it y or a servi ce t hat th e r ad i o t ermin al 3 use s. [ 0050]
F or ex a mpl e, wh en t he radi o s tatio n 2 is a radio st at ion th at has bas ic fun ctio ns fo r commun ic ating w ith t he radi o te rmi nal 3, t hat is ,
10 when i t is a radio st at ion t hat can commu nicate with th e rad io t ermi nal
3 o n its own simil arl y to th e ra di o st ation 1 , t he radi o stat i on 1 ma y s end a r equest for c ommuni cation prep arati on in St ep S403 i n F i g. 8. On the o th er h and , fo r ex am ple w h en t he radi o s t atio n 2 i s a ra dio st at ion t hat h as (o nl y) part of th e fun ct i ons for c om muni ca tin g wi th th e
15 r adio t erminal 3, th e radio st at i on 1 ma y se nd an instruct ion for
commu nic ati on prepa r ati on in S t ep S4 03. Here, a "r equ est " a nd an "instru cti on" are d if f erent iat ed as follo ws . A "Re quest" is u s ed wh en a node receivi ng such a r equ est d et erm ines w het her or no t to accep t th e r equest . M eanw hile , an " Instru ctio n" is use d wh en a n ode receivi ng
20 su ch an i ns t ru cti on sha l l acce pt t he instru ctio n. No te that , a radio
st at ion t hat h as (o nl y) part of th e fun ct i ons for c om muni ca tin g wi th th e r adio t erminal 3 is , for ex amp le, a r adi o station t hat t r ansfers o nl y us er d at a be tween th e radio t ermin al 3 a nd the upp er n etw ork, o r a r adio sta ti on th at on l y tra nsfers co nt rol - r ela t ed sign als b et we en t he
25 r adio t erminal 3 a nd t he u pp er netw ork. Al tern ati vel y, th e ra di o
st at ion t hat h as (o nl y) part of th e fun ct i ons for c om muni ca tin g wi th th e r adio t erminal 3 ma y b e a ra dio s tati on that has a f un ct ion fo r commu nic ati ng with t h e ra di o te rm in al 3 but l acks a fun ct i on for communicating with the upper network.
30 [0051]
In St ep S 4 03 i n Fig. 8, wh en se ndi ng th e r equ es t or in s tr uct ion , t he first radio st ation 1 m a y se nd t he foll owi ng i nform atio n :
- r ad io c onn ectio n co nfi guratio n in for mat ion: e. g. , servi ng c el l i nformat ion ;

21
- t erm ina l indiv idu al i nform atio n: e.g., r adio t ermi nal cap abil it y
i nformat ion , radi o te rmin al i denti fi er in form atio n, sel ect ed netwo r k
i dent if ie r info rm at ion, beare r info rm atio n, radio r esou rce control
i nformat ion , r adio t erminal mob i l it y histo r y i nforma ti on, s ervice
5 i nformat ion , or an y c ombi nat ion th ereof ; an d
- r ad io a cc es s in fo rm ation : e.g., radi o ac cess ide nti fier
i nformat ion .
S uch in f orm ati on ma y be s ent w ith th e r eq uest or instructi on
(i .e., b y t he s am e mess a ge), o r m a y b e se nt b y a s ep arat e m essage.
10 [0052]
In St ep S4 04 i n Fig. 8 , wh en ac cep ti ng t he r eq uest o r inst ru cti on f r om t he ra di o s tat ion 1, the r adio stat ion 2 ma y se nd t he fol l owin g i nformat ion :
- r ad io c onn ectio n co nfi guratio n in format ion: e. g. , s ys tem
15 i nformat ion , radi o resource c onfigu ratio n i nform atio n, m ea su r emen t
confi gurat ion in fo rm ation , m obil it y con trol info rm atio n, se cu rit y confi gurat ion in fo rm ation , o r an y co mbi na t i on th ere of ; and
- r ad io a cc es s in fo rm ation : e.g., radi o ac cess ide nti fier
i nformat ion , radi o a cc ess r esou r ce in fo r matio n, or the co mbin atio n
20 t hereof.
S uch in f orm ati on ma y be s ent w ith a respo nse to th e re qu est or i nst ructi on (i. e., by t he s ame message ) , or may b e s ent b y a se parat e message. [ 0053]
25 (Second Exemplary Procedure)
F i g. 9 i s a flo wcha rt sho win g a n op eratio n of th e radio st at ion 1 ac cordin g t o the s ec ond ex emp la r y p roc edu r e. T he p r ocesse s in St eps S 101 an d S 10 2 i n Fig. 9 are simil ar to those i n S te ps S10 1 an d S1 02 o f t he first ex empl ary proced ure shown in Fi g. 5. As h as been desc r i bed,
30 i n t he se con d exempla r y p roc edu r e, th e rad io st atio n 1 i ns tructs th e
r adio sta ti on 2 to est abli s h the second r adio conn ecti on o n t he cell 2 0. Th e com muni ca ti on p r ep aratio n inst ructi on (or req uest ) in St ep S101 m a y do ubl e as t he instru cti on from th e radio st at i on 1 to t he radio st at ion 2 t o es tab lish t he se con d radi o co nn ection . The p r oc edure

22
sh own in Fi g. 9 re present s th e c as e whe r e th e comm un ica ti on
prepar ati on i nstru ction i n Ste p S1 01 d oub l es as th e s econ d r ad i o
conn ect ion est abli sh m en t in st r uct ion. Th at is , t he c om muni ca tion
prepar ati on i nstru ction (o r r equ est ) message i n S te p S 101 expl i citl y o r
5 i m plicitl y rep rese nts th e se cond radio con nect ion e stablishm ent
i nst ructi on. A ccordi ngl y, in the ex ampl e of Fig. 9, t he r adio s tat ion 1 i s n ot requ ired to s end t o t he rad io stati on 2 a n i nde pe ndent m essa ge i ndicati ng t he s ec ond rad io co nn ecti on est ablishm ent inst ru cti on . In S t ep S50 3, th e ra dio stat ion 1 ( co mmun ic at ion cont r ol unit 1 5)
10 i nst ruct s, on th e f irs t cell 10, t he ra dio term in al 3 t o re ceiv e
i nformat ion of th e s eco nd c ell 2 0. In S t e p S5 04, t he radio st ati on 1 determ in es whether a n oti ficatio n o f compl eti on of the s econ d r adi o conn ect ion es tab lishm ent has b een recei ve d from th e ra dio st ati on 2, and ends the proc edu re of Fig. 9 on con diti on t hat the compl eti on
15 notificati on has been r ec eived.
[ 0054]
F i g. 1 0 is a fl ow ch art sho win g a n o pe r ati on o f t he rad io s t atio n
2 accordi ng t o th e s econ d ex emplary p ro ce dure. T he pro cesses i n
S t eps S20 1 t o S 20 4 in Fig. 10 a re si mila r to t hose i n Ste ps S201 t o
20 S204 of the second exemplary procedure shown in Fig. 6. In Step S605,
t he rad io st atio n 2 (comm uni cat i on cont ro l u nit 25 ) in s tr uct s th e r adi o t ermin al 3 to est ab li sh t he se cond radio c onnecti on on th e c el l 20. Th en, the r adio sta tion 2 s ends a com pl eti on no ti fi catio n t o t he r adio st at ion 1 i n res pon s e to c omplet ion o f th e s econ d r adi o con ne ction
25 es t abli s hme nt (St eps S 606 and S6 07).
[ 0055]
F i g. 1 1 is a fl ow ch art sho win g a n o pe r ati on o f t he rad io te rmi nal
3 accordi ng t o th e s econ d ex emplary p ro ce d ure . In Ste p S 701, th e
r adio t erminal 3 ( commu nicati on con tr ol un it 3 5) re ceiv es , o n th e first
30 cell 1 0 f r om t he fi rst rad io s tatio n 1, an in st r uctio n to re ceiv e
i nformat ion of th e s eco nd c ell 2 0. T he ra di o te rm i nal 3 pe r forms th e operation of receptio n o n t he s econd cell 20 , b as ed on the inst ru cti on f r om t he radio stat ion 1 . In S tep S 702, th e radio t ermi nal 3 re ce iv es, f r om t he se cond ra dio st ati on 2, an i ns tructi on to est ablish t he s ec ond

23
r adio conn ecti on. In St ep S7 03, i n r espon se t o the in st r ucti on i n S tep
S 701, the r adio t ermin al 3 co nfi gures t he cell 20 , a nd esta bl i s hes th e
s econ d r adi o conn ect ion wit h th e radio stati on 2 o n th e cell 20. In
S t ep S70 4, th e ra dio t erm in al 3 repo rt s , to th e rad i o st atio n 2,
5 compl eti on of s ec ond rad io co nn ecti on est abl i s hme nt o n the cell 2 0.
[ 0056]
F i g. 1 2 is a sequ en ce diagr am sho win g t he en tire se cond ex em plar y p ro cedu r e. The pr oc esses in St eps S 401 t o S 404 i n Fi g. 1 2 are simil ar to St eps S 401to S 404 of th e f irst ex em pla r y p r oc edu re
10 sh own in Fi g. 8. In Step S 805 , t h e r adio sta ti on 1 in st r ucts , on t he
fi rst cell 1 0, t he radi o t ermin al 3 to recei ve in fo r mat i on of th e secon d cell 2 0. Th e i ns tru cti on in S t ep S8 05 in clud es r adi o reso urc e confi gurat ion in fo rm ation of the secon d c ell 20 th at is n ec ess ary f or t he rad io t e r min al 2 to perform th e recept ion op erat ion on t he seco nd
15 cell 2 0. In Step S 805 , th e r adi o st ation 1 m a y al s o sen ds in fo r mat io n
t hat d efin es a gap pe riod ( e.g., gap p att ern ) f or t he rad io t ermi nal 3 t o pe rform th e recept ion op erati on on t he c ell 20 . Alt ernat ive l y, in t he ca se w he r e a gap pe ri od is pr ev io us l y de f i ned , th e radi o te rm i nal 3 m a y sp on taneo us l y set a gap per iod , in resp ons e to re ce pt ion o f t he radi o
20 r eso urce co nfi gura tion in fo r mat i on of th e secon d ce ll 20 from th e r ad io
st at ion 1 . Here, th e gap pe ri od means t he p erio d durin g whi ch , fo r r eceptio n of i nforma ti on on the s econd cell 2 0, t r an smiss ion on th e fi rst cell 1 0 to t he r ad io te r mi nal 3 is stop pe d or t he ra dio term ina l 3 i s not r equ i red to r ecei ve an y s ign al de st in ed for th e r adio t erminal 3
25 on t he fi rst cell.
[ 0057]
In St ep S 8 06, t he ra di o st ati on 1 instru ct s t he ra di o s tat ion 2 to es t abli s h t he second radio c onn ecti on o n th e cell 2 0 with t he radi o t ermin al 3. As h as be en desc r i bed , t he instru ctio n i n Ste p S 806 m a y
30 not be give n expl ici t l y. In S tep S 80 7, th e rad io st atio n 2 i ns truc ts th e
r adio te r mi n al 3 to es tab lish the s econd radi o con necti on on t he cell 20 . In St ep S 8 08, t he ra di o term ina l 3 con f igures th e c el l 20 b as ed on th e i nst ructi on from th e radio st ati on 2 . Thus, the r adio conn ect ion between the radio statio n 2 a nd t he r adi o t ermin al 3 is esta bl i s hed on

24
t he cell 2 0. In Ste p S8 09, th e radio st at ion 2 noti fies t he radi o s tati on
1 o f comp letio n of s ec ond rad io con necti on es tab lishment. B y th e
compl eti on i n Ste p S 808, th e radio t e rm i na l 3 can sim ul taneousl y use
t he cells 10 an d 20. Accordi ngl y, in St ep S 810 , fo r exam ple , the r adi o
5 t ermin al 3 receiv es downl ink d ata at e ach of th e c el ls 10 a nd 2 0.
[ 0058] Second Embodiment
In th e pre s ent em bod i m ent , a n example i n whi ch th e fi rst embodiment is applied to a 3GPP LTE system will be described. A
10 confi gurat ion example o f the radi o commu nic ati on s yst em acco rd ing to
t he pres ent em bod ime nt m a y be s i mi lar to t hat s ho wn i n Fig. 1. N ote t hat, th e r adio st atio ns 1 a nd 2 co rr espond t o eN Bs, and th e ra dio terminal 3 corresponds to a UE. The information exchange between r adio sta ti ons (i.e., betw ee n eNBs ) m a y be pe r f orm ed usin g X2 a s a
15 di rect int erface, m a y be pe r f orm ed usin g S1 as an i nte r face v ia the
co re n etw ork , o r ma y be per fo r m ed usin g a n ewl y d efi ned int erfa ce ( e. g. , X 3). The ra dio term ina l (UE ) 3 suppo rts ca r rier aggre gat ion o f cells op era t ed b y different r adio s tation s (eN Bs) (Int e r -eNB CA ). Not e t hat, th e " Int er -e NB C A" as us ed h erei n i s n ot l i mit ed to the m an ne r of
20 simul taneo us l y rec eivi ng o r trans mit tin g si gna l s actu all y on ce lls o f
di fferent eNBs. Ins t ead , it i nclu des th e m ann er of receivi ng or t r ansmitt ing s ign als (e. g. , u s er d at a or cont ro l in form atio n) act ual l y on an y on e of cells of di f f erent eN Bs alt hou gh th e UE 3 c an rece ive or t r ansmit sign al s on bot h of t he cell s of th e d iff eren t e NBs, t he m ann er
25 of receivin g o r t r ansmitti ng signals of di fferent t ypes on resp ec ti ve
cells o f di ffere nt eN Bs, o r th e m an ner o f u sin g ea ch of cells o f di fferent eNBs fo r o ne of s ign al recepti on an d tra n sm is sion . In the f oll owi ng, a des cript i on wil l be gi ven r egard in g t he radi o st ation s 1 and 2 as an eNB 1 and an eNB 2, and the radio terminal 3 as a UE 3.
30 [0059]
In th e pre s ent em bod i m ent , a p ro ce dure f or esta bl is hin g a radi o connection between each of the cells 10 and 20 and the UE 3 may be simil ar to t hat acc ording t o the first em bodim ent . That i s, t he eNB 1 r equest s o r inst ru cts t he e NB 2 to pre pa r e fo r c omm unicati on wit h th e

25
UE 3 on the ce ll 2 0, whil e t he fi rst radi o co nnection on the cel l 10
wi th t he UE 3 is establish ed. Fu rt he r, whi le mai nta ini ng t he fi rs t rad io
conn ect ion , t he eNB 1 i nst ruct s t he UE 3 or t he e NB 2 t o esta bl is h th e
s econ d r adi o conn ect ion with th e UE 3 on th e cell 20. In in st r uctin g
5 t he eNB 2 t o es tab lis h t he se cond radio c onnect ion , th e inst ru ction t o
t he eNB 2 m ay be giv en i mpli cit l y. Thu s, accord ing to th e pres en t em bod ime nt, t he U E 3 can est abli sh a r adio conn ect ion on ea ch of t he cells 10 and 20 fo r p erformin g c arrier aggre gati on o f the cel ls 1 0 and 20 oper at ed b y differ ent eN Bs 1 an d 2.
10 [0060]
Here, which one of the eNBs 1 and 2 is to be used for downlink us er d at a t ransmission may be determine d, fo r exa mple, b ased o n t he t yp e o f se r vi ce o r r equi red Qo S (o r QC I) . Fu rt he r, co ntrol -rela ted si gn als (C ontrol P lan e (CP) s ignal) ma y b e t ran smi t t ed from t he eN B 1
15 while us er dat a -relat ed si gnals (Use r Pl ane ( UP ) si gnal ) may b e
t r ansmitt ed from t he eNB 2. [ 0061]
A t hird ex empl ar y procedure co r resp onds to th e f irs t exem pla r y procedure accordi ng to th e f irs t embod ime nt . In th e t hird exempl ar y
20 procedure , t he eN B 1 instru cts t he U E 3 t o est abl is h t he se cond radio
conn ect ion on t he c el l 20. In t his case, t he eNB 1 m a y n oti f y th e UE 3 of radio c onnecti on c onfigu r ati on i nfo rm at ion (RR C C onn ect ion Re con fi gura t i on in f orm atio n) relat in g to th e radio con ne ct ion o n t he cell 2 0. Th en, t he U E 3 confi gures th e ce ll 2 0 in respo ns e to th e
25 i nst ructi on from th e eNB 1. Th us, th e UE 3 can esta bl is h the second
r adio conn ecti on o n t he cell 2 0 with th e eNB 2. [ 0062]
A fo urth ex empl ary proced ure c orresp o nds t o the fi r st ex em pla r y procedure accordi ng to th e s ec ond emb odim ent. In the fou rt h
30 ex em plar y p ro cedu r e, th e eNB 1 i nst ruct s the eN B 2 to est abli sh th e
s econ d r adi o conn ect ion on t he cell 20 . In respo ns e t o th e inst ruct ion f r om t he e NB 1, th e e NB 2 i ns tructs th e UE 3 t o est ab lish th e secon d radio connection on the cell 20. The eNB 2 may notify the UE 3 of the r adio conn ecti on c onfi gu ratio n i nforma tio n (R RC C onn ecti on

26
Re con fi gura t i on in f orm atio n) relat in g to t he radio conn ect ion on th e
cell 2 0. Th en, t he UE 3 c onfigu r es t he cell 2 0 i n r espo nse t o th e
i nst ructi on from th e eNB 2. Th us, th e UE 3 can esta bl is h the second
r adio conn ecti on o n t he cell 2 0 with th e eNB 2.
5 [ 0063]
In th e thi r d and fo urt h ex empl ary pro ced ures , i t is al s o possi ble
t hat at le as t p art of te rmin al i ndivid ual i nformat ion (UE Co ntex t
i nformat ion ) of th e UE 3 r el ati n g to esta bli s hme nt of t he se cond ra dio
connection is sent from the eNB 1 to the eNB 2 or from the eNB 2 to
10 t he eNB 1 . Furth er, in t he t hi rd an d f ourth ex em pl ar y p ro ce dure s , a t
l east on e o f radi o con nect ion config urati on info rm atio n ( RRC
Co nn ection R econ fi gurati on in f orm atio n) an d radio ac cess i nformat ion
(R adi o Ac ce ss info rm at ion ) r ela ti ng to e st ablishm en t o f th e fi rst o r
second radio connection may be sent from the eNB 2 to the eNB 1 or
15 from the eNB 1 to the eNB 2.
[ 0064]
The t ermi nal in div idu al i nform at ion ( UE C ont ext i nformati on) m a y in clud e at l ea st o ne of th e i nforma ti o n elem ent s liste d belo w:
- r ad io te r mi nal ca pab i l it y in f orm ati on (UE capab ilit y
20 i nformat ion ): e. g. , U E r ad io a cc ess cap abil i t y, U E net work c ap abilit y,
UE securit y cap ab ilit y, or an y comb in atio n th ere of;
- r ad io te r mi nal i de nti fier i nf orm ati on (U E identi fi cati on
i nformat ion ): e. g. , C -R NT I, (S - ) TMS I, sh ortMAC - I, o r an y c om bi nat ion
t hereof;
25 - sel ect ed n et wo rk in fo r matio n ( UE s el ected net work
information): e.g., GUMMEI (Globally Unique MME Identifier), eNB UE S1AP ID, MME UE S1AP ID, CSG ID, or any combination thereof;
- b earer i nformat ion ( Bearer in fo rm atio n): e.g., E -R AB ID , E -
RAB Level QoS Parameters, UL GTP Tunnel Endpoint ID, or any
30 combi nat ion th ereof;
- r ad io reso urce cont ro l in f orma t i on (RRC cont ext i nformat ion ):
AS -C onfig, AS -C ontex t, ue -C on figRel ea s e, u e -
Ra di oA cc essC ap ab ilit yInfo , o r an y c ombi natio n th ereo f;

27
- r ad io te r mi nal m obilit y hi st ory i n f ormatio n (UE histo r y i nformat ion ): e. g. , Las t Vi si ted C ell In f ormati on; an d
- servi ce i nformat ion (Servic e in form atio n): e.g., QC I, Qo S, MBMS information, or any combination thereof.
5 [ 0065]
The radi o conn ection confi gurat io n in fo r m atio n ( RR C Co nn ection R eco nfigu r atio n info rmation ) m a y i nclud e at least one of t he in fo r matio n el eme nts l is ted belo w:
- servi ng c ell in fo rm ation (S ervi ng Cell in form atio n): e. g. ,
10 Physical Cell ID (PCI), EUTRAN Cell Global ID (ECGI), or the
combi nat ion th ereof;
- s yst em i nform at ion (S ys te m i nform atio n): e.g., M IB ( M as te r
In fo rmati on Bl ock ) , S IB (S yst em In fo rm atio n Blo ck ) x (x = 1, 2, ..), or
t he co mbin atio n the r eo f;
15 - r ad io reso urce confi guratio n in formatio n (R ad io resource
confi gurat ion in fo rm ation ): e.g., P hys ic alC on fi gDe di cat ed, M ac -M ai nco nfig, R LC - Con fig, PDCP -Co nfi g, logi ca lCh ann el Iden tit y, d r b -Id entit y, ep s -B earer Id en t it y, or an y combi nat io n th ere of;
- m easure men t con fi gura ti on in f orm atio n (M easureme nt
20 confi gurat ion in fo rm ation ): e.g., MeasObj ect , Rep ort C onfi g, o r th e
comb i nat ion t he reof;
- m ob ilit y c ont rol in f orm atio n (M obilit y co nt rol in f orm atio n):
e.g. , t arge t P h ys C ell Id , carrie r Freq, ne wUE - Ide ntit y, o r an y
combi nat ion th ereof; an d
25 - securit y c onfi gurat ion in fo r mat io n (Se cu rit y con f igurat ion
i nformat ion ): e. g. , S ecu rit y A lgo rit hmCon fi g.
[ 0066]
The radi o access in fo rm atio n ( R ad io Ac ce s s info rm atio n) ma y
i nclu de a t l east o ne o f th e in form ation el em ents listed be low :
30 - r ad io a cc es s id enti fi er i nform at ion (Ra di o acces s i denti fi ca t i on
i nformat ion ): e. g. , R AC H pre amb l e ind ex; and
- r ad io a cc es s reso urc e in forma ti on (Radi o access r esou rce
i nformat ion ): e. g. , PR AC H reso urce confi guratio n.
[ 0067]

28
The t hird and fou r th exempl ar y procedu r es m a y be ap plied to
va riou s a ppli cati on s in cl udi ng, but n ot limi t ed to , a n app lic ati on wh ere
the eNB 1 is a macro radio base station (Macro eNB: MeNB) that
operates (man ages ) a m acro c ell wit h r el at ivel y la r ge cov era ge an d th e
5 eNB 2 is a low power radio station (Low Power Node: LPN) that
operates (manages) a cell with small coverage. The LPN may be, for ex am ple, a pi co ra dio bas e st ati on (P ico eNB: P eN B) havin g sim il ar functions as the MeNB, or may be a new type network node (New Node) with reduced functions as compared with the MeNB. Further,
10 t he s econd cell (c ell 20 ) m a y be a new t ype cel l ( Ne w Cell T ype) b ein g
di fferent fro m a c onv entio nal cell, i.e., th e s econ d ce ll m a y u s e a n ew t yp e carri er (New Ca r ri er T yp e) bein g different from a conv entio nal ca rrier . [ 0068]
15 In th e foll owin g, sp ecific ex amples o f t he thi rd and fou rt h
ex em plar y p ro cedu r es will b e desc r i bed . Fi g. 13 is a s equ en ce di agra m sh owin g t he en tire t hi rd ex empl ary pro ced ure, and F i g. 1 4 is a s equence diagram sho wi ng th e en t i re fou rt h ex empl ar y proc ed ur e. Note t hat , in Fi gs . 1 3 and 1 4, th e first cell 10 is referre d to as CE LL1,
20 and t he s econd cell 20 i s refer r ed to as CE LL2.
[ 0069] (Third Exemplary Procedure)
In St ep S 9 01, t he e NB 1 and th e UE 3 esta bl is h, on the cel l 10, t he first radio con ne ct ion (RRC Co nn ect ion Est abl is hmen t) . In Step
25 S902, the eNB 1 communicates with the UE 3 o n the cell 10. In the
ex am ple o f F i g. 1 3, the eNB 1 t r ansmits, on th e ce ll 1 0, do wnlin k dat a destined for the UE 3. In Step S903, the UE 3 or the eNB 1 performs detecti on or deci si on of t he cell 2 0 (secon dar y cell di s cover y or de ci si on). In St ep S 90 4, t h e e NB 1 re que sts or instructs the eNB 2 ,
30 which operat es the cell 20 , t o prep are fo r co mmu ni cat i on (i.e ., one o r
both o f t r ansm is si on and rec eptio n of s ignal s carr yi n g us er da t a or th e l i ke) on t he cell 2 0 wit h the UE 3 , whi ch bel on gs to th e its ow n cell (serv ing ce ll ) 10 ( S ec ondar y C ell P rep aratio n R eq uest (o r i ns t ru cti on)). In St ep S 9 05, t he e NB 2 s end s a r espo ns e to th e r eq ue st or inst ructio n

29
i n St ep S 904 to th e e NB 1 (Se con dary C ell Prepa r atio n Reque st (or
instruction) response). When an acknowledgeme nt (Acknowledgement)
i s trans mitted in S te p S 905 , th e eNB 2 p r epares fo r co mmu nic ation
wi th th e UE 3 on t he c ell 20 , b ased on th e re qu est or i nstru ctio n from
5 the eNB 1.
[ 0070]
In St ep S 9 06, i n r esponse t o r ecepti on of the ac kno wl ed gem ent, t he eNB 1 s ends , t o t he U E 3 on the cel l 10, an in st r uctio n fo r es t abli s hin g th e s econ d rad i o con ne ction o n th e cell 20 (RR C
10 Co nn ection R econ fi gurati on ). T he inst ru ction i ncl ud es ra dio
conn ect ion co nfig uratio n info rm atio n of t he secon d cell 2 0 ( S e co nd ar y Ce ll con fi gurat i on). In S t ep S9 07, t he U E 3 configu r e s the cel l 20 bas ed o n the instru ctio n from t he eNB 1. Th us, the r adio con ne ct ion between the eNB 2 and the UE 3 is established on the cell 20 (RRC
15 Co nn ection Es tab lishm ent).
[ 0071]
In St ep S 9 08, t he e NB 1 s end s, to t he UE 3 on th e fi r st cell 10 , a m es s age i ndi cat ing ac ti vat ion o f th e cell 20 (i.e ., us e init iat io n) in order to i ni t iat e c arri er a ggr e gatio n ( S ec ondar y C e l l Activa ti on ). In
20 Step S909, the eNB 1 notifies the eNB 1 of completion of
confi gurat ion of th e cel l 20 , i. e., c on figu rati on of the s econ dar y c ell f or carrie r aggr e ga tion (Secon da r y C ell C onfigu r at ion Com ple t e). B y compl eti on of S te p S 909, th e UE 3 can pe r form carri er aggre ga t i on o f t he cells 10 an d 20. Accordi ngl y, in St ep S 910 , fo r exam ple , the UE 3
25 r ecei ves d ownli nk d ata at ea ch o f the cel l s 10 and 20.
[ 0072] (Fourth Exemplary Procedure)
The proc ess es i n Ste ps S9 01 to S90 5 in Fi g. 1 4 are s imi lar to t hos e in St eps S 90 1 to S 905 i n F i g. 13. In St ep S 1006, th e e NB 1
30 i nst ruct s, at th e s ervin g cel l ( ser vin g cell) 10 , th e UE 3 t o rec eiv e
i nformat ion of th e s eco nd c ell 2 0 (R adi o R eso ur ce C on fi gura ti on o f S eco nd C ell ). In S tep S10 07, the eN B 1 in stru cts t he eNB 2 t o es t abli s h t he second radio c onn ecti on o n th e cell 2 0 with t he UE 3 (S eco nda r y C el l P r ep arat i on Co mpl ete ) . In Ste p S1 00 8, t he eNB 2

30 i nst ruct s the UE 3 to es tab lish t he se con d radio con nection o n t he c ell 20 (RRC c onn ecti on Re co nfigu r ati on). [ 0073]
In St ep S 1 009, the U E 3 confi gures th e ce ll 2 0 ba s ed on th e
5 i nst ructi on from th e eNB 2. Th us, th e r adi o con ne ctio n b etw ee n t he
eNB 2 and the UE 3 is established on the cell 20 (RRC Connection Estab lishm ent). In S t ep S1 010 , the eN B 2 noti f ies t he eN B 1 of compl eti on of s ec ond rad io co nn ecti on est ablishm ent (Seco nda r y C el l Configuration Complete). By completion of Step S1010, the UE 3 can
10 pe rform c arri er aggre gati on o f the cel ls 10 and 20. Accordin gl y, in
S t ep S10 11, for ex amp l e, t he U E 3 recei ve s dow nli nk data at e ach o f t he cells 10 an d 20. [ 0074] Third Embodiment
15 In th e pre s ent em bod i m ent , a modif i cat i on of th e seco nd
em bod ime nt wi ll be d escrib ed . In t he p r esent embo di ment, a
des crip tion wi ll be giv en o f b earers b etw een t he ra di o s tati ons 1 and 2 and th e up pe r net work , an d s etu p o f t he b earers in t he up pe r net wo rk . In ord er to t rans f er user dat a , t he b ea r ers ar e asso ci ate d with th e fi rst
20 and s econd r adio c onn ectio n s (i.e ., dat a ra di o be are r s (Ev olv ed Packe t
S ystem Radio bearers: EPS RBs)) on the cells 10 and 20, which are confi gure d b y t he procedures d es crib ed in th e s ec ond embod ime nt . [ 0075]
In an LTE s ys t em , an S1 b earer is us e d fo r t ran s f errin g u s er dat a
25 between the radio statio n (e NB ) 1 o r 2 a nd t he u ppe r n etw ork (Ev olv ed
P ack et C ore: EPC ) . An S 1 bearer i s e st ablish ed bet we en a dat a t r ansferrin g a pparatu s (i. e., S ervin g GW: S -GW ) i n the u pp er n etw ork and a n e NB. Furt her, i n an LTE s ys te m , a n S 5/S8 b ea r er i s est abl is hed between two data t r ans ferrin g a pp aratu s es i n t he EPC, i.e., th e S -GW
30 and the P -GW (Packet Data Network Gateway). An EPS RB and an S1
be arer are collecti vel y refe r r ed to as a ra dio acces s b ea rer (E -UTRA N Radio Access Bearer: E-RAB). An E-RAB is used for transferring user data between a UE and an EPC via an eNB. Further, bearers between a P-GW and a UE including an E-RAB and an S5/S8 bearer are referred

31
t o as a n EPS b ea r er. An EPS bearer is s et u p f or each U E. Fu rthe r , a
si ngle U E can use a pluralit y o f EPS b ea r ers. In t his ca s e, EPS beare r s
as so ciated wi th a sin gle U E is diffe r entiate d f rom ea ch o th er, f or
ex am ple, b y t heir Qo S class e s of us er da ta tha t th e y t r ansfer .
5 [ 0076]
Setup of an EPS bearer, an E-RAB, and an S1 bearer is controlled by a mobility management apparatus (Mobility Management En ti t y: MM E ) in t he u pper ne two r k. Wit h regar d to a n S 1 be are r, t he MME communicates with an S-GW and with an eNB to share bearer
10 c o n t ext (e . g. , th e IP address e s of t he S - GW and t he e NB , an d the end
point identifiers of the S-GW and the eNB) among the MME, the S-GW and th e e NB , and, con s equentl y, th e S1 b ea r er i s e st ablish ed . [ 0077]
F i g. 1 5 is a b loc k di agram sh owing a co nfi guratio n ex ample of
15 t he rad io c om muni cat ion s ys tem accordi ng t o th e pres ent embo di ment.
Th e EPC 4 , as t he spe ci fi c exampl e of t he u pper netwo r k , i ncl ud es an MME 5 and an S/P-GW 6. The eNBs 1 and 2 each establish a control connection with the MME 5 (S1 -MME) and a bearer (S1 bearer) as so ciated with t he S/ P -GW 6 for tra ns ferri ng u s er d ata .
20 [0078]
Next , a s etup p r oc edure of a n S1 be arer ( or E -RA B, EPS b ea r er ) ac cordin g t o the pre s en t emb odiment wil l be des crib ed with r eferen ce t o a s equ en ce di agram of Fi g. 1 6 . N ot e t hat , in Fi g. 1 6, th e firs t cell 10 i s re pre s en ted as CELL1, a nd th e s ec ond cell 2 0 i s represe nt ed a s
25 CELL2. In Step 1101, by signaling of the UE 3, the eNB 1, the MME 5,
and th e S /P -GW 6, an EP S bearer fo r trans f erri ng u s er data b et we en t he UE 3 and th e E PC 4 via t he cell 10 is con fi gu red . In St ep S1 102, in order t o enable t he UE 3 to p erfo rm carrier aggre gat ion o f th e ce ll s 1 0 and 20 ac cordin g to th e proc ed ur e des crib ed i n th e s econd emb od iment,
30 t he cell 2 0 is co nfi gured as th e seco nda r y cell . In Step S 110 3, the eNB
2 requests the MME 5 to set up a bearer (S1 the bearer, E-RAB, or EPS be arer) for tran s f erri ng use r d ata b et ween the UE 3 and t he EP C 4 v ia the cell 20. Thus, by the signaling of the UE 3, the eNB 2, the MME 5, and the S/P-GW 6, the bearer s etup procedure is executed. The eNB 2

32
s et s up the S1 b ea r er (o r t he E -RA B) acco r din g to t he b earer se tup
procedure. In Steps S1104 and S1106, the S/P -GW 6 transfers
downl ink u s er d ata d est ined fo r t he UE 3 to th e fi r st S 1 b ear er th at i s
as so ciated wi th t h e e NB 1 or to th e s eco nd S 1 be are r asso cia t ed wi th
5 the eNB 2. In Steps S1105 and S1107, the eNBs 1 and 2 transmit to
t he UE 3 t he do wn link user d at a rece ive d vi a th e S 1 beare r s . [ 0079]
Here, w hic h o ne o f t he eN B 1 a nd 2 to b e us ed fo r t ransmitt ing downl ink u s er data m a y be det ermin ed, for ex am ple, b ased on t he
10 s erv ice t ype o r r equi red QoS (o r QC I). F urt her, c ontrol -relat ed si gnals
(C ont rol P l an e (C P) si gn al) m a y be tra nsm i tted f r om th e eN B 1, whil e us er d at a - r el at ed s ignal s (U s er Pl an e (UP ) si gna l) m a y be t r ansm itt ed from the eNB 2. [ 0080]
15 Note t hat , wit h regard t o t he thi rd or fourth ex e m plary p r oc edure
described in the second embodiment, the example has been shown in which at l eas t on e of th e s el ect ed netwo r k i nform at ion and th e b ear er information of the UE 3 is sent from the eNB 1 to the eNB 2 in r equest ing (or inst r uctin g) pre parati on for com muni cat ion w it h the UE
20 3 o n the cell 2 0. Th e sp ec ific ex am ple o f th e s el ected ne two rk
information is a GUMMEI, an eNB UE S1AP ID, an MME UE S1AP ID, a CSG ID , o r an y com bi nat ion t he reof. Th e sp eci f ic ex ampl e of t he bearer information is an E-RAB ID, an E-RAB Level QoS Parameters, a UL GTP Tunnel Endpoint ID, or any combination thereof. One
25 advantage o f trans f erri ng at le ast o ne o f th e s el ected net wo r k
i nformat io n an d th e bearer information of th e UE 3 t o th e e NB 2 is th at, i n t he p r esent embod i m ent , th e eNB 2 ca n t ri gge r the s etu p o f t he be arer for tran s f erri ng , vi a t he cell 2 0, use r data o f t he UE 3. T hat is, t he eNB 2 i s o nl y re quired t o ge ne rate a b ea rer se t up r equest base d o n
30 at l eas t one o f th e selected ne t work i nformati on a nd the b ea r er
i nformat ion , an d s end t he gener ate d requ est to th e MME 5. Thus, t he pres ent emb od iment c an greatl y red uce the lo ad o f th e UE 3 du e to t he be arer s etup wi th di f ferent r adio b as e st atio ns. [ 0081]

33 Other Embodiments
In the second and third embodiments, the UE 3 may send control
i nformat ion (L1 / L2 c ontrol i nformat ion ) o f La yer 1 or Layer 2 usin g a
ph ysi cal up li nk c ont r ol chann el (p h ysi cal up link cont ro l ch annel :
5 P UCCH) on the s ec ondary c el l (cell 20). Sp eci f ic al l y, th e UE 3 m a y
us e a P UCC H of th e seco nda r y cell ( cell 2 0) f or r ep l yi n g a respon s e (e.g., H-ARQ (Hybrid Automatic Repeat Request) ACK, CQI (Channel Quali t y Ind i cat or)/PM I (P rec oding M atrix Indi cator), o r RI (R a nk In dicato r)) to downlin k r eceptio n on th e s ec ondary c el l (cel l 20 ).
10 [0082]
Note that, in the normal CA in which a single eNB operates a pl urali t y of cells, L1/ L2 cont r ol info rm ation us ing a P UC CH is en tire l y t r ansmitt ed on t he p r im ar y ce ll . If a rc hi t ecture si m il ar t o the normal CA is employed in the Inter -eNB CA, interworking between the eNB 1
15 and th e e NB 2 is r equ i red , and t hus a pro ces s d el a y, an a ddit io nal
network lo ad or the li ke woul d oc cu r . In con trast, us e o f th e ph ys ic al uplink con t ro l ch ann el of th e s e con dar y ce ll (cell 20 ) fo r a r es ponse t o downl ink re cep tio n on the se co ndar y cel l (cell 2 0) elimin at es th e necessity of interworking between the eNB 1 and the eNB 2.
20 [0083]
In the second and third embodiments, the eNB 1 may transmit, f or ex am ple , a rando m ac cess pre am ble i den ti fier (R A p reambl e ID), a mask value (RA PRACH Mask) used in a physical random access channel (Physical Random Access Channel: PRACH) to the eNB 2.
25 Th us, an ac cess de la y in th e up l i nk o n the second ce ll can be red uced.
[ 0084]
In th e s econd and thi r d em bo dim ent s , termi na l id ent ifie r s (C¬RN T I) o f a r adio l ink may b e id enti cal on t he p r ima r y cell (c ell 10 ) and th e s ec ondary cel l (cell 20).
30 [0085]
In the second and third embodiments, a Time Alignment (TA) Ti m er f or determini ng s yn ch r on ism of upli nk si gnals ( i .e., for managing synchronism) may be provided for each of the primary cell ( cell 1 0) an d th e s ec ondary c el l (cel l 20 ). Furth er, wh en th ere ar e a

34
pl urali t y of s econd ar y cel ls , it is al so po ssib le to p ro vid e a si ngl e T A
Ti m er to th e p lu ralit y of seco nda r y c ells, t o det ermi ne s ync hro ni sm .
Ac cordin gl y, t he p ri m ar y cell and th e s ec ondary c el l (or the s econd ar y
cell gr oup ) may b e lon g to d iffe r en t timin g gro up s ( T imi ng Ad va nc e
5 Groups: TAGs).
[ 0086]
In the second and third embodiments, t he eNB 2 may send MIB (Master In f ormati on B l ock )/ S IB (S ystem In fo rmati on B lo ck ) i nformat ion an d a se curit y co nt ext to t he eNB 1. T hus , t he U E 3 can
10 sm oo thl y c onfi gure t he s econd ar y ce ll ( ce l l 20).
[ 0087]
In th e first t o thi r d embo dime nts , th e s ec ondar y c ell ( cel l 2 0), which is add ed fo r carrier aggregati on , m a y b e us ed fo r onl y th e downlink component carrier (Component Carrier: CC) or for onl y the
15 uplink com ponent c arri er (C C).
[ 0088]
In th e first t o thi r d embo dime nts , th e primary c el l (cel l 10) and t he se cond ar y cel l (c ell 20) ma y be in di f f ere nt dupl ex mod es . For ex am ple, t he prim ar y cel l (c ell 10) ma y be in FDD (Frequ en c y Div is ion
20 Duplex) while the secondary cell (cell 20) may be in TDD (Time
Di visio n Dupl ex). [ 0089]
Th e draw in gs refer r ed to in t he f irs t t o thi rd em bod ime nts sho w the heterogeneous network (HetNet) environment. However, such
25 embodiments are applicable also to a homogenous network
(Homogeneous Network). Example of the Homogeneous Network may be a cellu l a r netwo rk form ed b y macro (o r m i cro ) cells o per ate d b y m acro (o r m i cro) ba s e station s. [ 0090]
30 The communication control methods performed by the radio
st at ion 1 ( commu nic ati on co ntrol uni t 15), t he ra di o s tation 2 ( commu nic ati on con trol unit 25), and th e radi o te rmin al 3 ( commu nic ati on cont ro l unit 35 ) desc rib ed in t he first to thi r d embodiments each may be implemented by using a semiconductor

35
processin g devi ce incl udin g an Ap plic ati on S pecific Int egra te d Circ uit
( AS IC)). Al tern at ivel y, the s e pro ces s es e ach ma y b e impl em ented b y
ca usin g a comp ute r s yst em i nclu din g at l east o ne pro ce sso r (e.g., a
m i crop r oc es sor, a Mic ro Pro ce ssing Unit (MPU) o r a Digit al S i gnal
5 P r ocesso r (DSP)) to ex ecute a program. More spe ci fi call y, o ne or
m ore pro gr ams i nc ludi ng i nstru cti on s fo r c ausin g a comp ute r s y s tem to pe rform th e algo r ithm s ex pla ine d with r efe ren ce t o t he fl owc ha rts an d sequence diagrams may be created and supplied to a computer system. [ 0091]
10 This program can be stored and provided to a computer using
an y t yp e o f non - t ransit or y com put er r ead a b le m ed ia. N on -tran si tory compu ter re adable m edi a i ncl ud e an y t yp e of t angi ble sto r age m edi a. Ex ampl es of non -t r ans ito r y c om pu ter r ead able m edi a incl ud e m agn eti c st orage m edia (su ch a s flex ibl e d is ks , m agnet ic t ap es, hard di sk d r ive s ,
15 et c.), opti cal m agn eti c sto r age m edi a (e.g., m agn et o -o pti cal di sk s ),
CD-ROM (Read Only Memory), CD-R, CD-R/W, and semiconductor memories (such as mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory), etc.). The program may be provided to a computer using any type of
20 t r ansito r y co mp ute r r eadable m edia. Exa mples o f t r an si tor y co m put er
r ead abl e medi a in clu de el ect r ic si gna ls, optical signals, and el ectrom agn etic wa ves. Tran si tory c ompu te r reada bl e medi a ca n provide the program to a c omputer via a wired communication line ( e. g. , e le ct ri c wi r es, an d opt ical fi be rs) or a wi r eless comm unicati on
25 l i ne.
[ 0092]
F urt her, in th e f irs t to t hird em bodi me nt s, th e de s cri pti on h as been given mainly of the LTE system. However, these embodiments m a y b e app lie d als o to a rad io c omm uni cat ion s yst em o ther th an th e
30 LTE system, e.g., a 3GPP UMTS (Universal Mobile
Telecommunications System), a 3GPP2 CDMA2000 system (1xRTT, HRPD (High Rate Packet Data)), a GSM (Global System for Mobile Communications) system, a WiMAX system or the like. [ 0093]

Furthermore, the embodiments stated above are merely examples of application of the technical ideas obtained by the present inventor. Needless to say, these technical ideas are not limited to those described in the above embodiments and may be changed in various ways. [0094]
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-223177 filed on October 5, 2012, and the disclosure of which is incorporated herein in its entirety by reference. Reference Signs List [0095]
1 FIRST RADIO STATION
2 SECOND RADIO STATION
3 RADIO TERMINAL 10 FIRST CELL
20 SECOND CELL
15 COMMUNICATION CONTROL UNIT
25 COMMUNICATION CONTROL UNIT
35 COMMUNICATION CONTROL UNIT

WE CLAIM:-
1. A radio communication system comprising:
a first radio station that operates a first cell; and a second radio station that operates a second cell, wherein while a first radio connection on the first cell with a radio terminal is established, the first radio station requests or instructs the second radio station to prepare for communication with the radio terminal on the second cell, and
the first radio station instructs the radio terminal or the second radio station to establish a second radio connection on the second cell between the second radio station and the radio terminal, while maintaining the first radio connection.
2. The radio communication system according to Claim 1,
wherein
the first radio station instructs the radio terminal to establish the second radio connection, and
the radio terminal configures the second cell.
3. The radio communication system according to Claim 1,
wherein
the first radio station instructs the second radio station to establish the second radio connection,
the second radio station instructs the radio terminal to establish the second radio connection, and
the radio terminal configures the second cell.
4. The radio communication system according to any one of
Claims 1 to 3, wherein the first radio station notifies the second radio
station of terminal individual information of the radio terminal
relating to establishment of the first or second radio connection.

5. The radio communication system according to Claim 4, wherein the second radio station triggers setup of a bearer for transferring user data of the radio terminal between an upper network and the second radio station, based on the terminal individual information.
6. The radio communication system according to any one of Claims 1 to 5, wherein the first radio station notifies the second radio station of at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.
7. The radio communication system according to any one of Claims 1 to 6, wherein the second radio station notifies the first radio station of at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.
8. The radio communication system according to any one of Claims 1 to 7, wherein
the first cell is a primary cell,
the second cell is a secondary cell, and
the radio terminal sends at least one of Layer 1 control
information and Layer 2 control information using a physical uplink
control channel on the second cell.
9. The radio communication system according Claim 4 or 5, wherein the terminal individual information includes at least one of (a) radio terminal capability information, (b) radio terminal identifier information, (c) selected network information, (d) bearer information, (e) radio resource control information, (f) radio terminal mobility history information, and (g) service information.

10. The radio communication system according to Claim 6 or 7, wherein the radio connection configuration information includes at least one of (a) serving cell information, (b) system information, (c) radio resource configuration information, (c) measurement configuration information, (d) mobility control information, and (f) security configuration information.
11. The radio communication system according to Claim 6 or 7, wherein the radio access information includes at least one of (a) radio access identifier information and (b) radio access resource information.
12. The radio communication system according to any one of Claims 1 to 11, wherein the first radio station instructs the second radio station to establish the second radio connection in order to enable the radio terminal to simultaneously use the first and second cells for signal reception or transmission.
13. A first radio station that operates a first cell, the first radio station comprising:
communication control means for controlling communication with a radio terminal having established a first radio connection on the first cell, wherein
while the first radio connection on the first cell with the radio terminal is established, the communication control means requests or instructs a second radio station, which operates a second cell, to prepare for communication with the radio terminal on the second cell, and
the communication control means instructs the radio terminal or the second radio station to establish a second radio connection on the second cell between the second radio station and the radio terminal, while maintaining the first radio connection.

14. The first radio station according to Claim 13, wherein the communication control means instructs the radio terminal to establish the second radio connection.
15. The first radio station according to Claim 13, wherein the communication control means instructs the second radio station to establish the second radio connection.
16. The first radio station according to any one of Claims 13 to
15, wherein the communication control means notifies the second radio
station of terminal individual information of the radio terminal
relating to establishment of the first or second radio connection.
17. The first radio station according to any one of Claims 13 to
16, wherein the communication control means notifies the second radio
station of at least one of radio connection configuration information
relating to establishment of the first or second radio connection and
radio access information relating to the first or second radio
connection.
18. The first radio station according to any one of Claims 13 to
17, wherein the communication control means receives, from the
second radio station, at least one of radio connection configuration
information relating to establishment of the first or second radio
connection and radio access information relating to the first or second
radio connection.
19. The first radio station according to any one of Claims 13 to 1 8, wherein
the first cell is a primary cell,
the second cell is a secondary cell, and
the radio terminal sends at least one of Layer 1 control information and Layer 2 control information using a physical uplink control channel on the second cell.

20. The first radio station according to Claim 16, wherein the terminal individual information includes at least one of (a) radio terminal capability information, (b) radio terminal identifier information, (c) selected network information, (d) bearer information, (e) radio resource control information, (f) radio terminal mobility history information, and (g) service information.
21. The first radio station according to Claim 17 or 18, wherein the radio connection configuration information includes at least one of (a) serving cell information, (b) system information, (c) radio resource configuration information, (c) measurement configuration information, (d) mobility control information, and (f) security configuration information.
22. The first radio station according to Claim 17 or 18, wherein the radio access information includes at least one of (a) radio access identifier information and (b) radio access resource information.
23. The first radio station according to any one of Claims 13 to 22, wherein the communication control means instructs the second radio station to establish the second radio connection in order to enable the radio terminal to simultaneously use the first and second cells for signal reception or transmission.
24. A second radio station that operates a second cell, the second radio station comprising:
communication control means for controlling communication with a radio terminal, wherein
while a first radio connection with the radio terminal is established on a first cell operated by a first radio station, the communication control means prepares for communication with the radio terminal on the second cell in response to an instruction or a request from the first radio station, and

the communication control means establishes, in response to an instruction from the first radio station, a second radio connection on the second cell between the second radio station and the radio terminal while the first radio connection is maintained.
25. The second radio station according to Claim 24, wherein the communication control means instructs the radio terminal to establish the second radio connection.
26. The second radio station according to Claim 24 or 25, wherein the communication control means receives, from the first radio station, terminal individual information of the radio terminal relating to establishment of the first or second radio connection.
27. The second radio station according to Claim 26, wherein the communication control means triggers setup of a bearer for transferring user data of the radio terminal between an upper network and the second radio station, based on the terminal individual information.
28. The second radio station according to any one of Claims 24 to 27, wherein the communication control means receives, from the first radio station, at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.
29. The second radio station according to any one of Claims 24 to 28, wherein the communication control means notifies the first radio station of at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.

30. A radio terminal that is used in combination with the radio
communication system according to any one of Claims 1 to 12, the
radio terminal comprising:
radio communication means; and
control means for configuring the second cell while maintaining the first radio connection with the first radio station, in response to an instruction from the first radio station or the second radio station.
31. The radio terminal according to Claim 30, wherein
the first cell is a primary cell,
the second cell is a secondary cell, and
the radio communication means sends at least one of Layer 1 control information and Layer 2 control information using a physical uplink control channel on the second cell.
32. A communication control method in a first radio station that
operates a first cell, the method comprising:
requesting or instructing a second radio station, which operates a second cell, to prepare for communication with a radio terminal on the second cell, while a first radio connection on the first cell between the first radio station and the radio terminal is established; and
instructing the radio terminal or the second radio station to establish a second radio connection on the second cell with the radio terminal, while maintaining the first radio connection.
33. The communication control method according to Claim 32,
wherein the instructing to establish the second radio connection
includes instructing the radio terminal to establish the second radio
connection.
34. The communication control method according to Claim 32, wherein the instructing to establish the second radio connection includes instructing the second radio station to establish the second radio connection.

35. The communication control method according to any one of Claims 32 to 34, wherein the requesting or instructing to prepare for the communication with the radio terminal includes notifying the second radio station of terminal individual information of the radio terminal relating to establishment of the first or second radio connection.
36. The communication control method according to any one of Claims 32 to 35, wherein the requesting or instructing to prepare for the communication with the radio terminal includes notifying the second radio station of at least one of radio connection configuration information relating to establishment of the first or second radio connection and radio access information relating to the first or second radio connection.
37. The communication control method according to any one of Claims 32 to 36, wherein the requesting or instructing to prepare for the communication with the radio terminal includes receiving, from the second radio station, at least one of radio connection configuration information relating to establishment of first or second radio connection and radio access information relating to the first or second radio connection.
38. A communication control method in a second radio station that operates a second cell, the method comprising:
preparing for communication with a radio terminal on the second cell in response to an instruction or a request from a first radio station, while a first radio connection with the radio terminal on a first cell operated by the first radio station is established; and
establishing, in response to an instruction from the first radio station, a second radio connection on the second cell between the second radio station and the radio terminal while the first radio connection is maintained.

39. The communication control method according to Claim 38, wherein the establishing includes instructing the radio terminal to establish the second radio connection.
40. The communication control method according to Claim 38 or 39, wherein the preparing includes receiving, from the first radio station, terminal individual information of the radio terminal relating to establishment of the first or second radio connection.
41. The communication control method according to Claim 40, further comprising triggering setup of a bearer for transferring user data of the radio terminal between an upper network and the second radio station, based on the terminal individual information.
42. A communication control method in a radio terminal that is used in combination with the radio communication system according to any one of Claims 1 to 12, the method comprising:
configuring the second cell while maintaining the first radio connection with the first radio station, in response to an instruction from the first radio station or the second radio station.
43. A non-transitory computer readable medium that stores a program for causing a computer to perform a communication control method in a first radio station operating a first cell, the communication control method comprising:
requesting or instructing a second radio station, which operates a second cell, to prepare for communication with the radio terminal on the second cell, while a first radio connection on the first cell with the radio terminal is established; and
instructing the radio terminal or the second radio station to establish a second radio connection on the second cell with the radio terminal.

44. A non-transitory computer readable medium that stores a program for causing a computer to perform a communication control method in a second radio station operating a second cell, the communication control method comprising:
preparing for communication with a radio terminal on the second cell in response to an instruction or a request from a first radio station, while a first radio connection with the radio terminal on a first cell operated by the first radio station is established; and
establishing, in response to an instruction from the first radio station, a second radio connection on the second cell between the second radio station and the radio terminal while the first radio connection is maintained.
45. A non-transitory computer readable medium that stores a program for causing a computer to perform a communication control method in a radio terminal used in combination with the radio communication system according to any one of Claims 1 to 12, the communication control method comprising:
configuring the second cell while maintaining the first radio connection with the first radio station, in response to an instruction from the first radio station or the second radio station.