Abstract:
A method, system and device for scheduling a non-contention based random access and transmitting a preamble are provided in the present invention. The present invention belongs to wireless telecommunication field and is used to solve a problem that the prior art is not able to support cross carrier non-competing random access scheduled by a Physical Downlink Control Channel (PDCCH). In the present invention, a Base Station (BS) adds Uplink Component Carrier (ul cc) identification information in a Downlink Control Information (DCI) signaling which is used to schedule a User Equipment (UE) to implement non-competing random access; and sends the UE the DCI signaling through the PDCCH. After detecting the DCI signaling, the UE sends the network side a preamble sequence on a UL CC corresponding to the UL CC identification. With the present invention, support is provided to realize cross carrier non-competing random access scheduled by PDCCH.

Description:
FIELD OF THE INVENTION  
       [0001]    The present invention relates to the field of radio communications and particularly to a method, system and device for scheduling a non-contention based random access and transmitting a preamble. 
       BACKGROUND OF THE INVENTION 
       [0002]    In a Long Term Evolution (LTE) system, there are two types of random accesses, i.e., a contention based random access and a non-contention based random access. Particularly the former is typically applicable to a scenario with an initial access of a user equipment, and a random access channel and a preamble sequence used in the contention based random access are selected by the User Equipment (UE) randomly from a set of configurations broadcast from a base station; and the latter is typically applicable to a scenario with downlink data arrival or handover, that is, the base station requires the random access to be initiated from the user equipment to establish uplink synchronization so that subsequent data transmission can be performed normally, and a random access channel and a preamble sequence used in the non-contention based random access are notified from the base station to the user equipment in signaling, particularly signaling over a Physical Downlink Control Channel (PDCCH). 
         [0003]    For a Long Term Evolution-Advanced (LTE-A) system, resources of a plurality of LTE carriers (also referred to as component carriers) have to be connected for use, particularly in the following two ways, so as to support a higher system bandwidth, e.g., 100 MHz, than the LTE system: 
         [0004]    In one way, a plurality of consecutive LTE carriers are aggregated to provide the Long Term Evolution-Advanced (LTE-A) with a larger transmission bandwidth. 
         [0005]    In the other way, a plurality of inconsecutive LTE carriers are aggregated to provide the LTE-A with a larger transmission bandwidth.  FIG. 1  illustrates an example of aggregating inconsecutive carriers. 
         [0006]    At present a common view of the standardization organization regarding a design of a carrier aggregation system is to keep a design over each carrier as consistent the LTE Release 8 (R8) as possible to thereby ensure that an LTE R8 user equipment can operate normally over each component carrier. 
         [0007]    In a carrier aggregation system, the 3GPP has come to a conclusion about determining an initial random access process, that is, a random access process is performed simply over a single carrier in a way consistent with the LTE Release 8 (R8). A non-contention based random access is still under study and discussion. A study showed that the continued use of LTE R8 single-carrier transmission for a non-contention based random access may not be applicable to all scenarios, and in some cases, a non-contention based random access with cross-carrier scheduling has to be adopted or can improve the performance of the system. 
         [0008]    In the LTE system, a non-contention based random access process includes the following several steps as illustrated in  FIG. 2 : 
         [0009]    Step  0 : A base station assigns a UE with a specific preamble sequence over a PDCCH of a downlink carrier in response to a current service demand; 
         [0010]    Step  1 : The UE transmits the specified preamble sequence at a specific time and frequency resource over a corresponding uplink carrier upon reception of a signaling indication over the PDCCH; and 
         [0011]    Step  2 : The base station transmits a random access response over the downlink carrier upon reception of the preamble sequence of a random access and performs subsequent signaling interaction and data transmission. 
         [0012]    In ongoing discussion about the standard of the LTE-A, there are two candidate solutions as follows to a PDCCH design of a carrier aggregation system in view of complexity of the PDCCH design, flexibility of scheduling and asymmetric uplink and downlink carrier aggregation: 
         [0013]    In one solution, a PDCCH is transmitted separately over each carrier, and a physical resource of only that carrier can be scheduled over the PDCCH, as illustrated in  FIG. 3 ; and 
         [0014]    In the other solution, a plurality of carrier resources are scheduled over a plurality of separate PDCCHs carried over one or more carriers, and this solution is an improvement, to the former solution. In this case, a resource of only one carrier can be scheduled over each PDCCH, as illustrated in  FIG. 4  taking a plurality of PDCCHs carried over a carrier as example. 
         [0015]    As currently discussed for the 3GPP standard, both non-cross-carrier scheduling and cross-carrier scheduling modes are supported for an LTE-A user, and a base station schedules a user equipment in either of the modes as needed in practice. 
         [0016]    Since there are only one pair of uplink and downlink carriers in the LTE system, all the foregoing flows take place over this pair of carriers. In the LTE-A system, control channel co-frequency interference between cells is very serious due to diversified types of base stations and a large number of densely deployed home base stations, relay stations, etc., and a current study showed that inter-cell interference in the LTE-A multi-carrier system can be lowered and the performance of the system can be improved effectively if different component carriers are used in adjacent cells as high power PDCCH transmission carriers in the system. 
         [0017]    In  FIG. 5 , for example, a downlink component carrier  1  (DL CC 1 ) is used in a cell  1  as a high power PDCCH transmission carrier, a downlink component carrier  2  (DL CC 2 ) is used in a cell  2  as a high power PDCCH transmission carrier, and PDCCHs of other carriers are transmitted at low power. In a scenario with limited interference, data transmission of respective downlink/uplink carriers can be scheduled over PDCCHs transmitted over high power carriers to ensure reliability of PDCCH transmission. 
         [0018]    Furthermore the 3GPP is also in discussion about whether introduce a new component carrier type (CC type) to the LTE-A, and as currently discussed, an extension carrier type may additionally be introduced besides R8 compatible component carriers, where only data but no control signaling may be transmitted over an extension carrier. As illustrated in  FIG. 6 , the DL CC 1  of the cell  1  is a R8 compatible component carrier, and the DL CC 2  is a extension carrier transmitting only data, so all the PDCCHs transmitting scheduling signaling in the cell  1  have to be transmitted over the DL CC 1 , and the DL CC 2  and the UL CC 2  are scheduled in the cross-carrier scheduling mode. 
         [0019]    In the scenarios illustrated in  FIG. 5  and  FIG. 6 , in order for a UE to obtain accurate uplink synchronization over each UL CC, a base station has to schedule the UE to be able to transmit a non-contention based Physical Random Access Control Channel (PRACH) over each uplink CC. As mentioned earlier, a non-contention based random access is generally scheduled over a PDCCH, and in the scenarios illustrated in  FIG. 3  and  FIG. 4 , PDCCH can only or preferably be transmitted over a specific carrier, and therefore cross-carrier scheduling has to also be supported for a PDCCH over which a non-contention based random access is scheduled. 
         [0020]    Also the following four scenarios are specified for identical or different Track Areas (TAs) of respective CCs in a 3GPP Radio Access Network (RAN4): 
         [0021]    Scenario 1: There are identical TAs of respective CCs in the case that a repeater, a Remote Radio Unit (RRU) and Coordinated Multi-Point (CoMP) are not introduced, as illustrated in  FIG. 7 . 
         [0022]    Scenario 2: TAs of different CCs may be different in the case that repeaters with different frequency selectivity are introduced, as illustrated in  FIG. 8 . 
         [0023]    Scenario 3: TAs of respective CCs may be different when there are non-collocated sites and the different CCs are transmitted through different stations, as illustrated in  FIG. 9 . 
         [0024]    Scenario 4: A user equipment has different TAs for different stations participating in coordination for uplink CoMP. 
         [0025]    Thus when there are different TAs of respective CCs, uplink synchronization has to be performed for those CCs to be aggregated so as to perform a carrier aggregation operation. 
         [0026]    In the LIE system, a user equipment receives a PDCCH through blind detection. Specifically blind detection is performed concurrently for PDCCHs in a common search space and a UE-specific search space, and a CCE (Control Channel Elements) aggregation level of a PDCCH can be 1, 2, 4 and 8. The number of candidate PDCCHs to be subject to blind detection is different at each CCE aggregation level. 
         [0027]    Also in each transmission mode, blind detection is performed for two Downlink Control Information (DCI) formats Which are differentiated from each other by their lengths. At the user equipment, there are at most 44 rounds of blind detection, including 12 ones in the common search space and 32 ones in the UE-specific search space, for a DCI format at the different aggregation levels. 
         [0028]    In the common search space, the UE performs blind detection for PDCCHs scrambled with a System Information Radio Network Temporary Identifier (SI-RNTI), a Private Radio Network Temporary Identifier (P-RNTI) and a Random Access Radio Network Temporary Identifier (RA-RNTI) for reception of system information, paging information and random access response information respectively. Also in the common search space, the UE performs blind detection for a PDCCH scrambled with a Cell Radio Network Temporary Identifier (C-RNTI) in the format of the DCI format  1 A. 
         [0029]    In the UE-specific search space, the UE performs blind detections for DCIs in different formats, including the DCI format  1 A, the DCI format  1 , the DCI format  1 B and the DCI format  1 D, in different transmission modes. 
         [0030]    A specific format of the DCI format  1 A is defined in the LTE R8. 
         [0031]    Also in the LTE R8, the base station schedules a non-contention based random access in the DCI format  1 A scrambled with a C-RNTI, and the specific length of the DCI is totally the same as the normal DCI format  1 A, but specific meanings of its information fields are specially defined particularly as follows: 
         [0032]    One bit is occupied for a field of a format  0 /format  1 A differentiation flag which takes the value of 0 to represent the format  0  and the value of 1 to represent the format  1 . This field is the same as the normal DCI format  1 A; 
         [0033]    One bit is occupied for a field of a Localized/Distributed VRB assignment flag which takes the value of 0. This information flag is set to 0 because this field is not required for scheduling a non-contention based random access; 
         [0034]    ┐log 2 (N RB   DL (N RB   DL +1)/2)┌ bits are occupied for a resource block assignment field, and all the bits are set to 1, where           represents a system bandwidth in Physical Resource Block (PRB); 
         [0035]    Six bits are occupied for a preamble index field to represent a preamble index for the random access; 
         [0036]    Four bits are occupied for a PRACH mask index field to indicate the index of a PRACH channel used for the random access; and 
         [0037]    All other bit fields (i.e., idle fields) are set to be all-zero. 
         [0038]    As can be apparent from the foregoing introduction, the DCI format  1 A has a variety of functions including scheduling system information scrambled with an SI-RNTI in the common search space, scheduling paging information scrambled with a P-RNTI in the common search space, scheduling random access response information scrambled with an RA-RNTI in the common search space, scheduling UE-specific data scrambled with a C-RNTI in the common search space, scheduling a non-contention based random access scrambled with a C-RNTI in the common search space, scheduling LIE-specific data scrambled with a C-RNTI in the LIE-specific search space, and scheduling a non-context random access scrambled with a C-RNTI in the UE-specific search space. 
         [0039]    The inventors have identified during making of the invention the following technical problem in the prior art: 
         [0040]    A cross-carrier non-contention based random access scheduled over a PDCCH cannot be supported in the prior art when a UE is configured in an cross-carrier scheduling mode. 
       SUMMARY OF THE INVENTION 
       [0041]    Embodiments of the invention provide a method, system and device for scheduling a non-contention based random access and transmitting a preamble so as to address the problem in the prior art of failing to support a cross-carrier non-contention based random access scheduled over a PDCCH. 
         [0042]    A method for scheduling a non-contention based random access includes:
       a base station adding information on an uplink component carrier identifier into Downlink Control Information, DCI, signaling for scheduling a user equipment to perform a non-contention based random access; and   the base station transmitting the DCI signaling to the user equipment over a Physical Downlink Control Channel, PDCCH, to instruct the user equipment to transmit a preamble sequence to the network side over an uplink component carrier corresponding to the information on the uplink component carrier identifier.       
 
         [0045]    A method for transmitting a preamble in a carrier aggregation system includes:
       a user equipment performing blind detection for a Physical Downlink Control Channel, PDCCH:   the user equipment determining detection of Downlink Control information, DCI, signaling carrying information on an uplink component carrier identifier, the DCI signaling scheduling the user equipment to perform a non-contention based random access; and   the user equipment transmitting a preamble sequence to the network side over an uplink component carrier corresponding to the uplink component carrier identifier.       
 
         [0049]    A base station includes:
       a carrier information adding unit configured to add information on an uplink component carrier identifier into Downlink Control Information, DCI, signaling for scheduling a user equipment to perform a non-contention based random access; and   a DCI signaling transmitting unit configured to transmit the DCI signaling over a PDCCH to the user equipment to instruct the user equipment to transmit a preamble sequence to the network side over an uplink component carrier corresponding to the uplink component carrier identifier.       
 
         [0052]    A user equipment includes:
       a blind detection unit configured to perform blind detection for a Physical Downlink Control Channel, PDCCH, and to determine detection of DCI signaling, carrying information on an uplink component carrier identifier, for scheduling the user equipment to perform a non-contention based random access; and   a sequence transmitting unit configured for the user equipment to transmit a preamble sequence to the network side over an uplink component carrier corresponding to the uplink component carrier identifier.       
 
         [0055]    A radio communication system includes:
       a base station configured to add information on an uplink component carrier identifier into Downlink. Control Information, DCI, signaling for scheduling a user equipment to perform a non-contention based random access and to transmit the DCI signaling to the user equipment over a Physical Downlink Control Channel, PDCCH; and   the user equipment configured to perform blind detection for the PDCCH, to determine detection of the DCI signaling, carrying the information on the uplink component carrier identifier, for scheduling the user equipment to perform a non-contention based random access, and to transmit a preamble sequence to the network side over an uplink component carrier corresponding to the uplink component carrier identifier.       
 
         [0058]    In the invention, a base station adds information on an uplink component carrier identifier into DCI signaling for scheduling a user equipment to perform a non-contention based random access and transmits the DCI signaling to the user equipment over a PDCCH, and the user equipment performs blind detection for the PDCCH and transmits a preamble sequence to the network side over an uplink component carrier indicated in the DCI signaling upon detection of the DCI signaling. Apparently in the invention, information on an uplink component carrier identifier is added into DCI signaling for scheduling a user equipment to perform a non-contention based random access so that the user equipment can determine from the DCI an uplink component carrier for transmission of a preamble sequence upon detection of the DCI and further transmit the preamble sequence over the uplink component carrier, thereby providing a support for an cross-carrier non-contention based random access scheduled over a PDCCH. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0059]      FIG. 1  is a schematic diagram of carrier aggregation in the prior art; 
           [0060]      FIG. 2  is a schematic diagram of a flow of non-contention based random access in the prior art; 
           [0061]      FIG. 3  is a schematic diagram of non-cross-carrier scheduling over a PDCCH in the prior art; 
           [0062]      FIG. 4  is a schematic diagram of cross-carrier scheduling over a PDCCH in the prior art; 
           [0063]      FIG. 5  is a schematic diagram of PDCCH power coordination between cells in the prior art; 
           [0064]      FIG. 6  is a PDCCH scheduling scheme with an extension carrier in the prior art; 
           [0065]      FIG. 7  is a schematic diagram of the scenario 1 in the prior art; 
           [0066]      FIG. 8  is a schematic diagram of the scenario 2 in the prior art; 
           [0067]      FIG. 9  is a schematic diagram of the scenario 3 in the prior art; 
           [0068]      FIG. 10  is a schematic flow chart of a method according to an embodiment of the invention; 
           [0069]      FIG. 11  is a schematic structural diagram of a system according to an embodiment of the invention; 
           [0070]      FIG. 12  is a schematic structural diagram of a base station according to an embodiment of the invention; and 
           [0071]      FIG. 13  is a schematic structural diagram of a user equipment according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0072]    In order to address the problem in the prior art of failing to support an cross-carrier non-contention based random access scheduled over a PDCCH, the embodiments of the invention provide a method for scheduling a non-contention based random access and transmitting a preamble in a carrier aggregation system, and in the method, a base station transmits, to a user equipment, DCI signaling, carrying information on an uplink component carrier identifier, for scheduling the user equipment to perform a non-contention based random access, and the user equipment transmits a preamble sequence over an uplink component carrier indicated in the DCI signaling. 
         [0073]    Referring to  FIG. 10 , a method for scheduling a non-contention based random access and transmitting a preamble in a carrier aggregation system according to an embodiment of the invention particularly includes the following steps: 
         [0074]    Step  10 : A base station adds information on an uplink component carrier identifier into DCI signaling for scheduling a user equipment to perform a non-contention based random access; 
         [0075]    Step  11 : The base station transmits the DCI signaling carrying the information on the uplink component carrier identifier to the user equipment over a PDCCH to instruct the user equipment to transmit a preamble sequence to the network side over an uplink component carrier corresponding to the uplink component carrier identifier; 
         [0076]    Step  12 : The user equipment performs blind detection for the PDCCH and determines detection of the DCI signaling, carrying the information on the uplink component carrier identifier, for scheduling the user equipment to perform a non-contention based random access; and 
         [0077]    Step  13 : The use equipment transmits the preamble sequence to the network side over the uplink component carrier corresponding to the information on the uplink component carrier identifier carried in the detected DCI signaling. 
         [0078]    At the base station side: 
         [0079]    The step  10  can be performed in the following two approaches: 
         [0080]    In one approach, the base station additionally sets a Carrier Indicator Field (CIF) in the DCI signaling for scheduling the user equipment to perform a non-contention based random access and adds the information on the uplink component carrier identifier into this CIF field. 
         [0081]    Specifically the base station additionally sets the CIF field at any fixed location in the DCI signaling for scheduling the user equipment to perform a non-contention based random access, and preferably can additionally set the CIF field at the head or tail of the DCI signaling. 
         [0082]    Correspondingly in the step  11 , the base station can transmit the DCI signaling carrying the information on the uplink component carrier identifier to the user equipment in a UE-specific search space. 
         [0083]    In the other approach, the base station takes a part of idle bits in the DCI signaling as a CIF field and carries the information on the uplink component carrier identifier in this CIF field, that is, adds the information on the uplink component carrier identifier into the CIF field. 
         [0084]    After the information on the uplink component carrier identifier is added into the CIF field, the base station can further determine whether there is(are) a(some) further idle bit(s) remaining in the DCI signaling, and if so, then the remaining idle bit(s) is(are) set to 0. 
         [0085]    Correspondingly in the step  11 , the base station transmits the DCI signaling to the user equipment in a common search space or a UE-specific search space. 
         [0086]    At the user equipment side: 
         [0087]    In correspondence to the foregoing first approach, in the step  12 , the DCI signaling detected by the user equipment is DCI signaling in which the CIF field carrying the information on the uplink component carrier identifier is set and which schedules the user equipment to perform a non-contention based random access. The user equipment can detect the DCI signaling in the UE-specific search space. 
         [0088]    In correspondence to the foregoing second approach, in the step  12 , the DCI signaling detected by the user equipment is DCI signaling in which the idle field carries the information on the uplink component carrier identifier and which schedules the user equipment to perform a non-contention based random access. The user equipment can detect the DCI signaling in the UE-specific search space or the common search space. 
         [0089]    In the invention, three bits can be occupied for the information on the uplink component carrier identifier carried in the DCI signaling, and the DCI signaling can particularly be a signaling in the format of the DCI format  1 A. 
         [0090]    The invention will be described in connection with embodiments thereof. 
       FIRST EMBODIMENT  
       [0091]    In this embodiment, a CIF field (for which three bits are occupied) is set at a fixed bit location in DCI signaling scrambled with a C-RNTI, for scheduling a non-contention based random access and in the DCI format  1 A, and for a simple design, the CIF field can be placed at the head or tail of the DCI signaling. The following description will be given taking a CIF field placed at the head of DCI signaling as an example: 
         [0092]    Step S 01 : A base station transmits DCI signaling carrying a CIF field to a UE over a PDCCH of a downlink carrier in response to a current service demand, and the DCI signaling is in the following format: 
         [0093]    CIF field, for which three bits are occupied and which carries information on an uplink component carrier identifier; 
         [0094]    Field of format  0 /format  1 A differentiation flag, for which one bit is occupied and which, for example, takes the value of 0 to represent the format  0  and the value of 1 to represent the format  1 , wherein this field is the same as the normal DCI format  1 A; 
         [0095]    Field of Localized/Distributed VRB assignment flag, for which one bit is occupied and which takes the value of 0, wherein this information field is set to 0 because this field is not required for scheduling a non-contention based random access; 
         [0096]    Resource block assignment field, for which ┐log 2 (N RB   DL (N RB   DL +1)/2)┌ bits are occupied, and all of which are set to 1, where           represents a system bandwidth in Physical Resource Block (PRB); 
         [0097]    Preamble index field, for which six bits are occupied to represent a preamble index for the random access; 
         [0098]    PRACH mask index field, for which four bits are occupied to indicate the index of a PRACH channel used for the random access; and 
         [0099]    All other bit fields (i.e., idle fields) are set to be zero. 
         [0100]    Step S 02 : The UE configured in an cross-carrier scheduling mode detects the DCI signaling in the forgoing format over the PDCCH and then determines that the DCI signaling is DCI signaling for scheduling a non-contention based random access and transmits a preamble sequence indicated in the preamble index field of the DO signaling to the base station at a time and frequency resource indicated in the resource block assignment field of the DCI signaling over an uplink component carrier corresponding to the uplink component carrier identifier carried in the CIF field of the DCI signaling; and 
         [0101]    Step S 03 : The base station transmits a random access response over the downlink carrier upon reception of the preamble sequence transmitted from the UE and performs subsequent signaling interaction and data transmission. 
         [0102]    Since the information length of the original LTE R8 DCI format  1 A is actually changed in this embodiment and the DCI format  1 A is also used to schedule system information, paging information, random access response information and other information common to LTE R8 and LTE-A users in a common search space, the DCI signaling generated according to this embodiment can be placed in a UE-specific search space without any influence upon blind detection of an LTE R8 user. 
       SECOND EMBODIMENT  
       [0103]    In this embodiment, three of idle bits in DCI signaling in the existing LTE R8, for scheduling a non-contention based random access and in the DCI format  1 A are taken as a CIF field, particularly as follows: 
         [0104]    Step S 11 : A base station transmits DCI signaling carrying a CIF field to a UE over a PDCCH of a downlink carrier in response to a current service demand, and the DCI signaling is in the following format: 
         [0105]    Field of format  0 /format  1 A differentiation flag, for which one bit is occupied and which, for example, takes the value of 0 to represent the format  0  and the value of 1 to represent the format  1 , wherein this field is the same as the normal DCI format  1 A; 
         [0106]    Field of Localized/Distributed VRB assignment flag, for which one bit is occupied and which takes the value of 0, wherein this information field is set to 0 because this field is not required for scheduling a non-contention based random access; 
         [0107]    Resource block assignment field, for which ┐log 2 (N RB   DL (N RB   DL +1)/2)┌ bits are occupied, and all of which are set to 1, wherein           represents a system bandwidth in Physical Resource Block (PRB); 
         [0108]    Preamble index field, for which six bits are occupied to represent a preamble index for the random access; 
         [0109]    PRACH mask index field, for which four bits are occupied to indicate the index of a PRACH channel used for the random access; 
         [0110]    CIF field, for which three bits are occupied and which carries information on an uplink component carrier identifier; and 
         [0111]    If there is(are) an(some) idle information bit(s) remaining, then it(they) is(are) set to 0 (there is no idle bit in the case of FDD and there are three idle bits in the case of TDD). 
         [0112]    Step S 12 : The UP configured in an cross-carrier scheduling mode detects the DCI signaling in the forgoing format over the PDCCH and then determines that the DCI signaling is DCI signaling for scheduling a non-contention based random access and transmits a preamble sequence indicated in the preamble index field of the DCI signaling to the base station at a time and frequency resource indicated in the resource block assignment field of the DCI signaling over an uplink component carrier corresponding to the uplink component carrier identifier carried in the CIF field of the DCI signaling; and 
         [0113]    Step S 13 : The base station transmits a random access response over the downlink carrier upon reception of the preamble sequence transmitted from the UE and performs subsequent signaling interaction and data transmission. 
         [0114]    Since the bit length of the DCI format  1 A defined in the LTE R8 is not changed in this embodiment and there is no influence upon blind detection of an LTE R8 user in a common search space, the DCI signaling generated according to this embodiment can be placed in the common search space. 
         [0115]    The first and second embodiments can be used separately or in combination, that is, an LTE-A UE configured in an cross-carrier scheduling mode detects blindly the DCI format  1 A generated according to the second embodiment in the common search space and then determines it as a DCI for scheduling a non-contention based random access and transmits the preamble over the specific UL CC indicated in the CIF field; and the LTE-A UE configured in an cross-carrier scheduling mode detects blindly the DCI format  1 A generated in the first approach in the UE-specific search space and then determines it as a DCI for scheduling a non-contention based random access and transmits the preamble over the specific UL CC indicated in the CIF field. 
         [0116]    Referring to  FIG. 11 , an embodiment of the invention further provides a radio communication system including: 
         [0117]    A base station  21  configured to add information on an uplink component carrier identifier into Downlink Control Information, DCI, signaling for scheduling a user equipment to perform a non-contention based random access and to transmit the DCI signaling to the user equipment over a Physical Downlink Control Channel, PDCCH; and 
         [0118]    The user equipment  22  configured to perform blind detection for the PDCCH, to determine detection of the DCI signaling, carrying the information on the uplink component carrier identifier, for scheduling the user equipment to perform a non-contention based random access, and to transmit a preamble sequence to the network side over an uplink component carrier corresponding to the uplink component carrier identified. 
         [0119]    The base station  21  is configured: 
         [0120]    To additionally set a CIF field at a fixed location in the DCI signaling for scheduling the user equipment to perform a non-contention based random access and to add the information on the uplink component carrier identifier into the CIF field; and 
         [0121]    Correspondingly the user equipment  22  is configured: 
         [0122]    To detect over the PDCCH the DCI signaling in which the CIF field carrying the information on the uplink component carrier identifier is set and which schedules the user equipment to perform a non-contention based random access. Specifically the DCI signaling can be detected in a UE-specific search space. 
         [0123]    The base station  21  is configured: 
         [0124]    To take a part of idle bits in the DCI signaling as a CIF field and to carry the information on the uplink component carrier identifier into the CIF field; and 
         [0125]    Correspondingly the user equipment  22  is configured: 
         [0126]    To detect over the PDCCH the DCI signaling in which the idle field carries the information on the uplink component carrier identifier and which schedules the user equipment to perform a non-contention based random access. Specifically the DCI signaling can be detected in a common search space or a UE-specific search space. 
         [0127]    Referring to  FIG. 12 , an embodiment of the invention further provides a base station which can be applied in a radio communication system and which includes: 
         [0128]    A carrier information adding unit  30  configured to add information on an uplink component carrier identifier into Downlink Control Information DCI, signaling for scheduling a user equipment to perform a non-contention based random access; and 
         [0129]    A DCI signaling transmitting unit  31  configured to transmit the DCI signaling over a PDCCH to the user equipment to instruct the user equipment to transmit a preamble sequence to the network side over an uplink component carrier corresponding to the uplink component carrier identifier. 
         [0130]    The carrier information adding unit  30  includes: 
         [0131]    A field setting unit configured to additionally set a CIF field at a fixed location in the DCI signaling for scheduling the user equipment to perform a non-contention based random access; and 
         [0132]    An identifier adding unit configured to add the information on the uplink component carrier identifier into the CIF field. 
         [0133]    The field setting unit is configured: 
         [0134]    To additionally set the CIF field at the head or tail of the DCI signaling for scheduling the user equipment to perform a non-contention based random access. 
         [0135]    The DCI signaling transmitting unit  31  is configured: 
         [0136]    To transmit the DCI signaling to the user equipment in a UE-specific search space. 
         [0137]    The carrier information adding unit  30  is configured: 
         [0138]    To take a part of idle bits in the DCI signaling as a CIF field and to carry the information on the uplink component carrier identifier in the CIF field. 
         [0139]    The information adding unit is further configured: 
         [0140]    To determine whether there is(are) a(some) further idle bits s) remaining in the DCI signaling, and if so, then set the idle bit(s) to 0. 
         [0141]    The DCI signaling transmitting unit  31  is configured: 
         [0142]    To transmit the DCI signaling to the user equipment in a common search space or a UE-specific search space. 
         [0143]    Referring to  FIG. 13 , an embodiment of the invention further provides a user equipment including: 
         [0144]    A blind detection unit  40  configured to perform blind detection for a Physical Downlink Control Channel, PDCCH, and to determine detection of DCI signaling, carrying information on an uplink component carrier identifier, for scheduling the user equipment to perform a non-contention based random access; and 
         [0145]    A sequence transmitting unit  41  configured for the user equipment to transmit a preamble sequence to the network side over an uplink component carrier corresponding to the uplink component carrier identifier. 
         [0146]    The blind detection unit  40  includes a first detection unit and/or a second detection unit, where: 
         [0147]    The first detection unit is configured to detect the DCI signaling in which a CIF field carrying the information on the uplink component carrier identifier is set and which schedules the user equipment to perform a non-contention based random access; and 
         [0148]    The second detection unit is configured to detect the DCI signaling in which an idle field carries the information on the uplink component carrier identifier and which schedules the user equipment to perform a non-contention based random access. 
         [0149]    The first detection unit is configured: 
         [0150]    To detect in a UE-specific search space the DCI signaling in which the CIF field is set and which schedules the user equipment to perform a non-contention based random access. 
         [0151]    The second detection unit is configured to detect in a common search space or a UE-specific search space the DCI signaling in which the idle field carries the information on the uplink component carrier identifier and which schedules the user equipment to perform a non-contention based random access. 
         [0152]    In summary, advantageous effects of the invention include: 
         [0153]    In the solutions according to the embodiments of the invention, abase station adds information on an uplink component carrier identifier into DCI signaling for scheduling a user equipment to perform a non-contention based random access and transmits the DCI signaling to the user equipment over a PDCCH, and the user equipment performs blind detection for the PDCCH and transmits a preamble sequence to the network side over an uplink component carrier indicated in the DCI signaling upon detection of the DCI signaling. Apparently in the invention, information on an uplink component carrier identifier is added into DCI signaling for scheduling a user equipment to perform a non-contention based random access so that the user equipment can determine from the DCI an uplink component carrier for transmission of a preamble sequence upon detection of the DCI and further transmit the preamble sequence over the uplink component carrier, thereby providing a support for an cross-carrier non-contention based random access scheduled over a PDCCH. 
         [0154]    Those skilled in the art shall appreciate that the embodiments of the invention can be embodied as a method, system or computer program product. Therefore, the invention can be embodied in the form of an all-hardware embodiment, an all-software embodiment or an embodiment of software and hardware in combination. Furthermore the invention can be embodied in the form of a computer program product embodied in one or more computer useable storage mediums (including but not limited to a disk memory an optical memory, etc.) in which computer useable program codes are contained. 
         [0155]    The invention has been described in a flow chart and/or a block diagram of the method, device (system) and computer program product according to the embodiments of the invention. It shall be appreciated that respective flows and/or blocks in the flow chart and/or the block diagram and combinations of the flows and/or blocks in the flow chart and/or the block diagram can be embodied in computer program instructions. These computer program instructions can be loaded onto a general-purpose computer, a specific-purpose computer, an embedded processor or a processor of another programmable data processing device to produce a machine so that the instructions executed on the computer or the processor of the other programmable data processing device create means for performing the functions specified in the flow(s) of the flow chart and/or the block(s) of the block diagram. 
         [0156]    These computer program instructions can also be stored into a computer readable memory capable of directing the computer or the other programmable data processing device to operate in a specific manner so that the instructions stored in the computer readable memory create an article of manufacture including instruction means which perform the functions specified in the flow(s) of the flow chart and/or the block(s) of the block diagram. 
         [0157]    These computer program instructions can also be loaded onto the computer or the other programmable data processing device so that a series of operational steps are performed on the computer or the other programmable data processing device to create a computer implemented process so that the instructions executed on the computer or the other programmable device provide steps for performing the functions specified in the flow(s) of the flow chart and/or the block(s) of the block diagram. 
         [0158]    Evidently those skilled in the art can snake various modifications and variations to the invention without departing from the spirit and scope of the invention. Thus the invention is also intended to encompass these modifications and variations thereto so long as the modifications and variations come into the scope of the claims appended to the invention and their equivalents.