Title of Invention MOBILE COMMUNICATION SYSTEM, RELAY STATION, BASE STATION, AND CONTROL METHOD THEREOF Technical Field [0001] The present application relates to a method of selecting a cell to be used for connection between a relay station and a base station from a plurality of candidate cells in a mobile communication system including a base station and a relay station that belongs to the base station. Background Art [0002] In LTE-Advanced (Long Term Evolution Advanced) of 3GPP (3rd Generation Partnership Project), the introduction of relay stations (hereinafter "RNs (Relay Nodes)") has been examined (see NPL 1 and 2). The RN is one of techniques for increasing the communication speed of mobile stations (hereinafter "UEs (User Equipments)") located at cell edges and/or for increasing cell areas of base stations (hereinafter "eNBs (Evolved Node Bs)"). The details of the RN architecture examined in 3GPP are shown in NPL 2. [0003] The outline of a mobile communication system based on the RN architecture disclosed in NPL 2 is explained hereinafter. Fig. 1 shows a network configuration example when the RN examined in 3GPP is used. A base station (eNB) 9 1 belongs to a core network (hereinafter "CN") 4 of a mobile telecommunications carrier. The base station (eNB) 9 1 creates an eNB cell 10 and relays traffic between a mobile station (UE) 3 and the core network (CN) 4. A relay station (RN) 92 belongs to the base station (eNB) 9 1 by means of a backhaul link (BL1 in the figure) and also belongs to the core network (CN) 4 via the backhaul link (BL1). The base station (eNB) 9 1 and the relay station (RN) 92 can connect to a management apparatus 5 via the core network (CN) 4. The management apparatus 5 is an OAM (Operation Administration and Maintenance) system, and administers information set by the mobile telecommunications carrier. The relay station (RN) 92 is able to acquire information from the management apparatus 5. The mobile station (UE) 3 belongs to the base station (eNB) 9 1 or the relay station (RN) 92 by means of an access link (ALl in the figure). The relay station (RN) 92 creates an RN cell 20 and relays traffic between the mobile station (UE) 3 and the core network (CN) 4. Details of the backhaul link and the access link are explained later. [0004] Fig. 2 is a sequence diagram showing the outline of an RN start-up procedure described in Section 4.7.6 of NPL 3. The start-up procedure includes a phase 1 and a phase 2 explained below. In the phase 1, the relay station (RN) 92 connects to a network (E-UTRAN/EPC) as a mobile station (UE). Then, the relay station (RN) 92 acquires initialization parameters from the management apparatus 5 (i.e., OAM system). The initialization parameters include a list (i.e., a donor cell list) of eNB cells to which the relay station (RN) 92 can belong as an RN by using a backhaul link (BL1). After acquiring the initialization parameters, the relay station (RN) 92 releases the network connection as the UE and thereby finishes the phase 1. Note that the base station (eNB) 91-1 to which the relay station (RN) 92 belongs in the phase 1 does not necessarily have the function of allowing a relay station (RN) to belong thereto. [0005] In the phase 2, the relay station (RN) 92 selects one of at least one eNB cell (i.e., candidate for donor cell) indicated by the donor cell list acquired from the management apparatus 5, and belongs to a base station (eNB) 91-2 operating the selected cell as a relay station (RN). Then, the relay station (RN) 92 acquires configuration information of the backhaul link (BL1) from the base station (eNB) 91-2 to which the relay station (RN) 92 belongs, and configures the backhaul link (BL1). After finishing the procedure of the phase 2, the relay station (RN) 92 starts to operate the relay station cell (RN cell) 20. [0006] Further, as disclosed in NPL 4, there are three types, i.e., type 1, type la, and type l b in the RN examined in 3GPP. The RN may support only one of these three types, or may change the operating mode between plural types. Alternatively, different operating modes may be used for different UEs. The type-1 RN uses the same carrier (i.e., the same frequency) for the backhaul link and the access link (in-band), and time-divides the radio resources for the backhaul link and the radio resources for the access link. The main purpose of this scheme is to avoid the interference from the access-link transmission to the backhaul-link reception in the RN. [0007] The type-la RN uses different carriers (i.e., different frequencies) for the backhaul link and the access link (out-band). Therefore, the type- l a RN does not require the time-division for radio resources unlike the type-1 RN, and performs mutually independent communications between the backhaul link and the access link. [0008] Similarly to the type-1 RN, the type- l b RN uses the same frequency for the backhaul link and the access link. However, the type- l b RN does not time-divide the radio resources. This type is used on condition that the interference from the access-link transmission to the backhaul-link reception is sufficiently suppressed. [0009] In the phase 2 of the above-described start-up procedure, the RN transmits RN identification information including an RN type to the eNB. Then, the eNB determines the control method of the backhaul link based on the RN type information included in the RN identification information. More specifically, the eNB determines whether the resources of the backhaul link should be time-divided or not based on the RN type information. [0010] In the specification of the present application, among the eNBs, an eNB that can allow an RN to belong thereto is called "Donor eNB" (hereinafter "DeNB"). A mobile station (UE) that directly belongs to a relay station (RN) is called "RN-UE". Further, in the discussion on 3GPP, a demand for supporting multihop RNs in the future is arising. The multihop RN is a technique that makes it possible to connect an additional relay station (RN) to a relay station (RN) that already belongs to an eNB in a cascade configuration. In this specification, in the explanation relating to the multihop technique, a relay station (RN) belonging to an eNB through a radio interface is called "upper RN" and a relay station (RN) belonging to the upper RN through a radio interface is called "lower RN" in order to distinguish them from each other. Further, in this specification, a radio interface between an eNB and an RN and between an upper RN and a lower RN is called "backhaul link". Meanwhile, a radio interface between an eNB and an eNB-UE and between an RN and an RN-UE is called "access link". Citation List Non Patent Literature [001 1] NPL 1: 3GPP TR 36.912 V9.2.0 (2010-03), "Feasibility study for Further Advancements for E-UTRA (LTE-Advanced)", 3GPP (3rd Generation Partnership Project), March 2010 NPL 2 : 3GPP TR 36.806 V9.0.0 (2010-03), "Relay architectures for E-UTRA (LTEAdvanced)", 3GPP, March 2010 NPL 3: 3GPP TS 36.300 V10.2.0 (2010-12), "Overall description; Stage 2 (Release 10)", 3GPP, December 2010 NPL 4: 3GPP TR 36.814 V9.0.0 (2010-03), "Further advancements for E-UTRA physical layer aspects", 3GPP, March 2010 Summary of Invention Technical Problem [0012] The inventors of the present application have made detailed examination on the donor cell selection method that is used when plural candidate donor cells are indicated by the donor cell list. In the above-described procedure disclosed in NPL 3, the relay station (RN) acquires a donor cell list from a management apparatus such as an OAM system that is different from the base station (eNB). Further, the RN selects a donor cell from the donor cell list based solely on information administered by the RN (e.g., received power measured by the RN) and requests connection with the selected cell. However, the candidate donor cells indicated by the donor cell list, which is supplied from the management apparatus (i.e., OAM system) to the RN, are controlled by eNB(s) based on information administered by the eNB(s) (e.g., the load of the cells and the backhaul link configuration of other RN). Therefore, there is a possibility that a donor cell that is selected based solely on the information administered by the RN (such as received power measured by the RN) is not a desirable cell for the eNB(s) included in the mobile communication system. [0013] For example, assume a case where an eNB generates two cells (first and second cells). When the first and second cells are both indicated by a donor cell list acquired from the management apparatus, the RN selects one of the first and second cells as a donor cell based on the reception quality of the first and second cells measured by the RN itself. In this example, assume that the first cell is selected. Then, the RN requests the eNB that the RN connects to the first cell as an RN. However, there is a possibility that the second cell is more desirable than the first cell as the cell to which the RN newly connects in consideration of the status of the first and second cells at the time when the connection is requested from the RN, i.e., in consideration of the load of the first and second cells, the connection status of other RN, and the like. However, the eNB cannot effectively control the decision on the donor cell that is made by the RN. [0014] As a way of solving this problem, it is conceivable that the eNB (s) waits until the RN requests connection with the most suitable donor cell. Specifically, the eNB (s) may respond with the rejection to the connection request by the RN when the donor cell requested by the RN is not a suitable cell. The RN that receives the rejection response requests connection with a newly-selected donor cell. The eNB (s) repeats the rejection response as long as the donor cell requested by the RN is not a suitable cell, and waits for a connection request for the most suitable donor cell. However, in this method, the rejection response is possibly repeated for many times and therefore a long time is wasted until finding the optimal donor cell. In particular, when the donor cell is switched (backhaul link is switched) after the operation of the RN cell is started, i.e., when the donor cell is switched in a state where an RN-UE already exists, the operation of the RN is temporarily suspended. Therefore, taking a long time for the switching of the donor cell may cause a significant impact on the RN-UE. [0015] The present invention has been made in consideration of the above-described problems. Certain embodiments of the present invention provide a mobile communication system, a relay station, a base station, a control method thereof, and a program, capable of determining a donor cell based on both donor cell selection criteria on a relay station side and donor cell selection criteria on a base station side. Solution to Problem [0016] According to one embodiment, a mobile communication system includes at least one base station and a relay station. The relay station is configured to acquire a donor cell list indicating at least one candidate cell. Further, one of a first base station, included in the at least one base station, and the relay station is configured to determine a donor cell, to be connected to the relay station by the backhaul link, from the donor cell list based on both first cell management information and second cell management information. The first cell management information relates to the at least one candidate cell and originates from the at least one base station. The second cell management information originates from the relay station. [0017] According to another embodiment, a relay station apparatus includes a radio communication unit and a control unit. The radio communication unit is configured to relay transmission and reception data to and from a mobile station by using a backhaul link connected to one of at least one base station and an access link connected to the mobile station. The control unit acquires a donor cell list indicating at least one candidate cell through the radio communication unit. Further, the control unit maintains second cell management information. Further, the control unit determines a donor cell, to be connected to the relay station apparatus by the backhaul link, from the donor cell list in response to receiving first cell management information relating to the at least one candidate cell and originating from the at least one base station. [0018] According to still another embodiment, a base station apparatus includes a radio communication unit and a control unit. The radio communication unit is configured to perform data transfer, through a backhaul link connected to a relay station, with a mobile station connected to the relay station by means of an access link. The control unit maintains or receives, from another base station apparatus, first cell management information. Further, the control unit determines a donor cell, to be connected to the relay station by the backhaul link, from the donor cell list in response to receiving second cell management information from the relay station. The first cell management information relates to the at least one candidate cell. [0019] According to yet another embodiment, a control method of a relay station apparatus includes: (a) acquiring a donor cell list indicating at least one candidate cell; (b) maintaining second cell management information; and (c) determining a donor cell, to be connected to the relay station apparatus by the backhaul link, from the donor cell list in response to receiving first cell management information relating to the at least one candidate cell from the at least one base station. [0020] According to further embodiment, a control method of a base station includes: (a) maintaining or receives, from another base station apparatus, first cell management information; and (b) determining a donor cell, to be connected to the relay station by the backhaul link, from the donor cell list in response to receiving second cell management information from the relay station, the first cell management information relating to the at least one candidate cell and originating from at least one base station including the base station apparatus. [0021] According to still further embodiment, a program for causing a computer to carry out the method according to the yet another embodiment is provided. [0022] According to yet further embodiment, a program for causing a computer to carry out the method according to the further embodiment is provided. Advantageous Effects of Invention [0023] According to the above-mentioned embodiments of the present invention, it is possible to provide a relay station, a base station, a control method thereof, and a program which are capable of determining a donor cell based on both donor cell selection criteria on a relay station side and donor cell selection criteria on a base station side. Brief Description of Drawings [0024] [Fig- 1] Fig. 1 is a block diagram showing a configuration example of a mobile communication system according to related art; [Fig. 2] Fig. 2 is a sequence diagram showing a start-up procedure of a relay station according to related art; [Fig- 3] Fig. 3 is a block diagram showing a configuration example of a mobile communication system according to a first illustrative embodiment of the present invention; [Fig. 4] Fig. 4 is a block diagram showing a configuration example of a base station according to the first illustrative embodiment of the present invention; [Fig- 5] Fig. 5 is a block diagram showing a configuration example of a base station according to the first illustrative embodiment of the present invention; [Fig. 6] Fig. 6 is a block diagram showing a configuration example of a base station according to the first illustrative embodiment of the present invention; [Fig. 7] Fig. 7 is a block diagram showing a configuration example of a base station control apparatus according to the first illustrative embodiment of the present invention; [Fig. 8] Fig. 8 is a sequence diagram showing an example of a donor cell selection procedure of a relay station according to the first illustrative embodiment of the present invention; [Fig- 9] Fig. 9 is a sequence diagram showing another example of a donor cell selection procedure of a relay station according to the first illustrative embodiment of the present invention; [Fig. 10] Fig. 10 is a flowchart showing an operation example of a relay station according to the first illustrative embodiment of the present invention; [Fig. 11] Fig. 11 is a flowchart showing an operation example of a base station according to the first illustrative embodiment of the present invention; [Fig. 12] Fig. 1 is a sequence diagram showing an example of a donor cell selection procedure of a relay station according to a second illustrative embodiment of the present invention; [Fig. 13] Fig. 13 is a flowchart showing an operation example of a relay station according to the second illustrative embodiment of the present invention; [Fig. 14] Fig. 14 is a flowchart showing an operation example of a base station according to the second illustrative embodiment of the present invention; [Fig. 15] Fig. 15 is a sequence diagram showing an example of a donor cell selection procedure of a relay station according to a third illustrative embodiment of the present invention; and [Fig. 16] Fig. 16 is a flowchart showing an operation example of a base station according to the third illustrative embodiment of the present invention. Description of Embodiments [0025] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. Identical or corresponding elements are designated by identical reference numerals throughout the drawings, and redundant description thereof will be omitted except when necessary. [0026] In the above-described first to third illustrative embodiments, examples of an LTEAdvanced- type mobile communication system are explained. However, the application of the present invention is not limited to LTE-Advanced-type mobile communication systems. That is, the present invention can be widely applied to mobile communication systems including a relay station. [0084] Any of the processes of the base station 1 and the relay station 2 that are performed for determining a donor cell as described in the above-described first to third illustrative embodiments may be implemented by using a semiconductor processing device such as an ASIC (Application Specific Integrated Circuit) or a DSP (Digital Signal Processor). Alternatively, these processes may be implemented by causing a computer such as a microprocessor to execute a program. Specifically, a program including instructions to cause a computer to execute an algorithm shown in at least one of Figs. 10, 11, 13, 1 and 16 may be created, and the created program may be supplied to a computer. [0085] This program can be stored in various types of non-transitory computer readable media and thereby supplied to computers. The non-transitory computer readable media includes various types of tangible storage media. Examples of the non-transitory computer readable media include a magnetic recording medium (such as a flexible disk, a magnetic tape, and a hard disk drive), a magneto-optic recording medium (such as a magneto-optic disk), a CD-ROM (Read Only Memory), a CD-R, and a CD-R/W, and a semiconductor memory (such as a mask ROM, a PROM (Programmable ROM), an EPROM (Erasable PROM), a flash ROM, and a RAM (Random Access Memory)). Further, the program can be supplied to computers by using various types of transitory computer readable media. Examples of the transitory computer readable media include an electrical signal, an optical signal, and an electromagnetic wave. The transitory computer readable media can be used to supply programs to computer through a wire communication path such as an electrical wire and an optical fiber, or wireless communication path. [0086] Further, the first to third illustrative embodiments according to the invention can be combined as desired. [0087] For the setting-up and handover of the relay station, it is desirable that determination of the donor cell is performed in a shorter time in comparison to the setting-up and handover of the mobile station. This is because the faster determination can prevent the communication disconnection of the RN-UE. In the handover of mobile stations, the target cell is typically determined by selecting a cell of which the quality of the downlink reception at the mobile station is the best from a neighbor cell list supplied from the source base station. If this target cell determination method used in the handover of mobile stations is applied to relay stations, only the circumstances on the relay station side and the requirement conditions from the relay station to the donor cell are taken into consideration. As a result, as stated previously as the problem to be solved, if the base station cannot allow the relay station to belong to the base station due to the circumstances on the base station side, the relay station is rejected from belonging to the base station. In contrast to this, in each of the above-described embodiments, the donor cell is determined with consideration given to not only the circumstances/requirement conditions on the relay station side but also to the circumstances/requirement conditions on the base station side. Therefore, in each of the above-described embodiments, it is possible to select an appropriate candidate cell as a donor cell in a short time and thereby to prevent the frequent occurrences of the repetition of the initial start-up procedure and the handover procedure, which would otherwise occur due to the unsuccessful donor cell selection. [0088] Further, the present invention is not limited to the above-described illustrative embodiments, and needless to say, various modifications can be made without departing from the spirit and scope of the present invention described above. [0089] This application is based upon and claims the benefit of priority from Japanese patent application No. 201 1-089287, filed on April 13, 201 1, the disclosure of which is incorporated herein in its entirety by reference. Reference Signs List [0090] 1 BASE STATION 2 RELAY STATION 3 MOBILE STATION 4 CORE NETWORK 1 1 RADIO COMMUNICATION UNIT 12 TRANSMISSION DATA PROCESSING UNIT 1 RECEPTION DATA PROCESSING UNIT 14 COMMUNICATION UNIT 15 BACKHAUL LINK CONTROL UNIT 2 1 LOWER RADIO LINK COMMUNICATION UNIT 22 TRANSMISSION DATA PROCESSING UNIT 23 RECEPTION DATA PROCESSING UNIT 24 UPPER RADIO LINK COMMUNICATION UNIT 25 BACKHAUL LINK CONTROL UNIT 3 1 RADIO COMMUNICATION UNIT 32 RECEPTION DATA PROCESSING UNIT 33 TRANSMISSION DATA CONTROL UNIT 34 TRANSMISSION DATA PROCESSING UNIT 35 BUFFER UNIT 5 1 COMMUNICATION UNIT 52 TRANSMISSION DATA PROCESSING UNIT 53 RECEPTION DATA PROCESSING UNIT 54 CANDIDATE CELL MANAGEMENT UNIT CLAIMS [Claim 1] A mobile communication system comprising: at least one base station; and a relay station that relays transmission and reception data to and from a mobile station by using a backhaul link connected to one of the at least one base station and an access link connected to the mobile station, wherein the relay station is configured to acquire a donor cell list indicating at least one candidate cell, and one of a first base station, included in the at least one base station, and the relay station is configured to determine a donor cell, to be connected to the relay station by the backhaul link, from the donor cell list based on both first cell management information and second cell management information, the first cell management information relates to the at least one candidate cell and originates from the at least one base station, and the second cell management information originates from the relay station. [Claim 2] The mobile communication system according to Claim 1, wherein the first cell management information includes a first parameter to be used by the at least one base station if the at least one candidate cell is determined as the donor cell, and the second cell management information includes a second parameter to be used by the relay station if the at least one candidate cell is determined as the donor cell. [Claim 3] The mobile communication system according to Claim 2, wherein the first parameter includes at least one of: an operation status associated with the at least one candidate cell and a performance condition of the at least one candidate cell requested by the at least one base station to be the donor cell, and the second parameter includes at least one of: a radio quality of the at least one candidate cell and a performance condition of the at least one candidate cell requested by the relay station to be the donor cell. [Claim 4] The mobile communication system according to any one of Claims 1 to 3, wherein the first cell management information includes at least one of (1) a load of the at least one candidate cell, (2) a connection status to the at least one candidate cell from another relay station, (3) cell configuration information indicating a time-division implementing status of a radio resource of the at least one candidate cell, (4) a priority among the at least one candidate cell as stored in the at least one base station, and (5) a list of cells selected by the at least one base station based on at least one of the aforementioned items (1) to (4). [Claim 5] The mobile communication system according to any one of Claims 1 to 4, wherein the second cell management information includes at least one of (a) a reception quality of a down link signal from the at least one candidate cell, (b) whether a radio resource time-division of a backhaul link is necessary, (c) type information of the relay station, (d) performance of the relay station, (e) a priority among the at least one candidate cell as stored in the relay station, and (f) a list of cells selected by the relay station based on at least one of the aforementioned items (a) to (e). [Claim 6] The mobile communication system according to any one of Claims 1 to 5, wherein the first cell management information includes cell configuration information indicating a time-division implementing status of a radio resource of the at least one candidate cell, the second cell management information includes type information of the relay station indicating whether a radio resource time-division of the backhaul link is necessary, and when a type of the relay station indicates that a radio resource time-division is necessary between an access link and a backhaul link, the first base station or the relay station determines a cell in which a radio resource time-division is already implemented among the at least one candidate cell as the donor cell. [Claim 7] The mobile communication system according to any one of Claims 1to 5, wherein the first cell management information includes cell configuration information indicating a time-division implementing status of a radio resource of the at least one candidate cell, the second cell management information includes performance information relating to a data transfer capability of the relay station, when the relay station possesses a first performance, the first base station or the relay station determines a cell in which a radio resource time-division is already implemented among the at least one candidate cell as the donor cell, and when the relay station possesses a second performance with a data transfer capability higher than that of the first performance, the first base station or the relay station determines a cell in which a radio resource time-division is not yet implemented among the at least one candidate cell as the donor cell. [Claim 8] The mobile communication system according to any one of Claim 4 and Claims 5 to 7 depending from Claim 4, wherein the priority among the at least one candidate cell is determined in such a manner that a priority of a second cell is lower than a priority of a first cell, the second cell being dependently formed under condition of formation of the first cell. [Claim 9] The mobile communication system according to Claim 8, wherein the first cell is backward compatible carrier, and the second cell is non-backward compatible carrier. [Claim 10] The mobile communication system according to any one of Claims 1 to 9, wherein the relay station receives the first cell management information transmitted from at least one second base station included in the at least one base station and thereby determines the donor cell. [Claim 11] The mobile communication system according to Claim 10, wherein the first cell management information includes information regarding a cell selected from the at least one candidate cell that satisfies a predetermined condition. [Claim 12] The mobile communication system according to Claim 11, wherein the predetermined condition relates to a load of the at least one candidate cell. [Claim 13] The mobile communication system according to Claim 12, wherein the at least one second base station transmits the first cell management information including information regarding a cell that is selected from the at least one candidate cell on a basis of its cell load. [Claim 14] The mobile communication system according to Claim 11, wherein the predetermined condition relates to a priority among the at least one candidate cell. [Claim 15] The mobile communication system according to Claim 14, wherein the first cell management information includes information regarding a cell that is selected from the at least one candidate cell based on the priority. [Claim 16] The mobile communication system according to any one of Claims 10 to 15, wherein the at least one second base station transmits the first cell management information including information regarding a candidate cell operated by another base station. [Claim 17] The mobile communication system according to any one of Claims 1 to 9, wherein the first base station receives the second cell management information transmitted from the relay station and thereby determines the donor cell. [Claim 18] The mobile communication system according to Claim 10, wherein the second cell management information includes information regarding a cell selected from the at least one candidate cell that satisfies a predetermined condition. [Claim 19] The mobile communication system according to Claim 18, wherein the predetermined condition relates to reception quality of a downlink signal from the at least one candidate cell. [Claim 20] The mobile communication system according to Claim 19, wherein the relay station transmits the second cell management information including information regarding a cell that is selected from the at least one candidate cell on a basis of the reception quality. [Claim 21] The mobile communication system according to any one of Claims 17 to 20, wherein the relay station transmits the second cell management information including information regarding a candidate cell operated by the first base station. [Claim 22] The mobile communication system according to any one of Claims 17 to 21, wherein the first base station receives the second cell management information via another base station included in the at least one base station. [Claim 23] The mobile communication system according to any one of Claims 17 to 22, wherein when the second cell management information received from the relay station includes information regarding a cell operated by the first base station, the another base station transfers the second cell management information to the first base station and transfers information regarding the donor cell received from the first cell to the relay station. [Claim 24] The mobile communication system according to any one of Claims 1to 23, wherein the relay station connects to one of the at least one base station as a mobile station and thereby acquires the donor cell list from a management apparatus via the one of the at least one base station. [Claim 25] The mobile communication system according to any one of Claims 1 to 23, wherein the relay station acquires the donor cell list from the at least one base station. [Claim 26] A relay station apparatus comprising: a radio communication means for relaying transmission and reception data to and from a mobile station by using a backhaul link connected to one of at least one base station and an access link connected to the mobile station; and a control means for controlling the backhaul link, wherein the control means acquires a donor cell list indicating at least one candidate cell through the radio communication means, maintains second cell management information, and determines a donor cell, to be connected to the relay station by the backhaul link, from the donor cell list in response to receiving first cell management information relating to the at least one candidate cell from the at least one base station. [Claim 27] The relay station apparatus according to Claim 26, wherein the first cell management information includes a first parameter to be used by the at least one base station if the at least one candidate cell is determined as the donor cell, and the second cell management information includes a second parameter to be used by the relay station apparatus if the at least one candidate cell is determined as the donor cell. [Claim 28] The relay station apparatus according to Claim 27, wherein the first parameter includes at least one of an operation status associated with the at least one candidate cell and a performance condition of the at least one candidate cell requested by the at least one base station to be the donor cell, and the second parameter includes at least one of a radio quality of the at least one candidate cell apparatus and a performance condition of the donor cell requested by the relay station apparatus to be the donor cell. [Claim 29] The relay station apparatus according to any one of Claims 26 to 28, wherein the first cell management information includes at least one of (1) a load of the at least one candidate cell, (2) a connection status to the at least one candidate cell from another relay station, (3) cell configuration information indicating a time-division implementing status of a radio resource of the at least one candidate cell, (4) a priority among the at least one candidate cell as stored in the at least one base station, and (5) a list of cells selected by the at least one base station based on at least one of the aforementioned items (1) to (4). [Claim 30] The relay station apparatus according to any one of Claims 26 to 29, wherein the second cell management information includes at least one of (a) a reception quality of a down link signal from the at least one candidate cell, (b) whether a radio resource time-division of a backhaul link is necessary, (c) type information of the relay station apparatus, (d) performance of the relay station apparatus, (e) a priority among the at least one candidate cell as stored in the relay station apparatus, and (f) a list of cells selected by the relay station apparatus based on at least one of the aforementioned items (a) to (e). [Claim 31] The relay station apparatus according to any one of Claims 26 to 30, wherein the first cell management information includes cell configuration information indicating a time-division implementing status of a radio resource of the at least one candidate cell, the second cell management information includes type information of the relay station indicating whether a radio resource time-division of the backhaul link is necessary, and when a type of the relay station apparatus indicates that a radio resource time-division is necessary between a backhaul link and an access link, the control means determines a cell in which a radio resource time-division is already implemented among the at least one candidate cell as the donor cell. [Claim 32] The relay station apparatus according to Claim 30, wherein the first cell management information includes cell configuration information indicating a time-division implementing status of a radio resource of the at least one candidate cell, the second cell management information includes performance information relating to a data transfer capability of the relay station apparatus, when the relay station apparatus possesses a first performance, the control means determines a cell in which a radio resource time-division is already implemented among the at least one candidate cell as the donor cell, and when the relay station apparatus possesses a second performance with a data transfer capability higher than that of the first performance, the control means determines a cell in which a radio resource time-division is not yet implemented among the at least one candidate cell as the donor cell. [Claim 33] The relay station apparatus according to any one of Claims 26 to 32, wherein the relay station apparatus connects to one of the at least one base station as a mobile station and thereby acquires the donor cell list from a management apparatus via the one of the at least one base station. [Claim 34] The relay station apparatus according to any one of Claims 26 to 33, wherein the control means receives the first cell management information transmitted from at least one second base station included in the at least one base station and thereby determines the donor cell. [Claim 35] A base station apparatus comprising: a radio communication means for performing data transfer, through a backhaul link connected to a relay station, with a mobile station connected to the relay station by means of an access link; and a control means for controlling the backhaul link, wherein the control means maintains or receives, from another base station apparatus, first cell management information and determines a donor cell, to be connected to the relay station by the backhaul link, from the donor cell list in response to receiving second cell management information from the relay station, wherein the first cell management information relates to the at least one candidate cell. [Claim 36] The base station apparatus according to Claim 35, wherein the first cell management information includes a first parameter to be used by the at least one base station if the at least one candidate cell is determined as the donor cell, and the second cell management information includes a second parameter that is used by the relay station if the at least one candidate cell is determined as the donor cell. [Claim 37] The base station apparatus according to Claim 36, wherein the first parameter includes at least one of an operation status associated with the at least one candidate cell and a performance condition of the donor cell requested by the at least one base station to be the donor cell, and the second parameter includes at least one of a radio quality of the at least one candidate cell measured or held by the relay station and a performance condition of the at least one candidate cell requested by the relay station to be the donor cell [Claim 38] The base station apparatus according to any one of Claims 35 to 37, wherein the first cell management information includes at least one of (1) a load of the at least one candidate cell, (2) a connection status to the at least one candidate cell from another relay station, (3) cell configuration information indicating a time-division implementing status of a radio resource of the at least one candidate cell, (4) a priority among the at least one candidate cell as stored in the at least one base station, and (5) a list of cells selected by the at least one base station based on at least one of the aforementioned items (1) to (4). [Claim 39] The base station apparatus according to any one of Claims 35 to 38, wherein the second cell management information includes at least one of (a) a reception quality of a down link signal from the at least one candidate cell, (b) whether of a radio resource time-division of a backhaul link is necessary, (c) type information of the relay station, (d) performance of the relay station, (e) a priority among the at least one candidate cell as stored in the relay station, and (f) a list of cells selected by the relay station based on at least one of the aforementioned items (a) to (e). [Claim 40] The base station apparatus according to any one of Claims 35 to 39, wherein the control means receives the second cell management information transmitted from relay station and thereby determines the donor cell. [Claim 41] The base station apparatus according to any one of Claims 35 to 39, wherein the control means receives the second cell management information via another base station included in the at least one base station. [Claim 42] A control method of a relay station apparatus configured to relay transmission/reception data of a mobile station by using a backhaul link connected to one of at least one base station and an access link connected to the mobile station, the control method comprising: acquiring a donor cell list indicating at least one candidate cell; maintaining second cell management information; and determining a donor cell, to be connected to the relay station apparatus by the backhaul link, from the donor cell list in response to receiving first cell management information relating to the at least one candidate cell from the at least one base station. [Claim 43] A control method of a base station apparatus configured to perform data transfer, through a backhaul link connected to a relay station, with a mobile station connected to the relay station by means of an access link, the control method comprising: maintaining or receives, from another base station apparatus, first cell management information; and determining a donor cell, to be connected to the relay station by the backhaul link, from the donor cell list in response to receiving second cell management information from the relay station, wherein the first cell management information relates to the at least one candidate cell. [Claim 44] A non-transitory computer readable medium storing a program for causing a computer to carry out the control method according to Claim 42. [Claim 45] A non-transitory computer readable medium storing a program for causing a computer to carry out the control method according to Claim 43.