Abstract:
Disclosed is a method and an apparatus for transmitting and receiving control information for receiving a service in a broadcast communication system. The method includes inserting first control information for receiving at least one different service at a next frame in each of multiple service data pieces of a current frame and transmitting a frame including the first control information, making it possible to efficiently transmit and receive a frame, which includes multiple services configured through a combination of one or more radio frequencies, and thereby enabling rapid receiving of a switched service in the case of service switching.

Description:
PRIORITY 
     This application claims priority under 35 U.S.C. §119(a) to Korean Patent Applications Serial No. 10-2008-0002361 and 10-2008-0005061, filed in the Korean Intellectual Property Office on Jan. 8, 2008 and Jan. 16, 2008, respectively, and to PCT/KR2009/000093 filed Jan. 8, 2009, the entire contents of each which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and an apparatus for transmitting and receiving control information in a broadcast communication system and, more particularly to a method and an apparatus for transmitting and receiving control information about a frame, which includes multiple services, in a broadcast communication system. 
     2. Description of the Related Art 
     In our 21 st  century information society, broadcast communication services are digitized, and multi-channel, high-quality broadband service is provided. The recent increase in the spread of high screen quality digital televisions (TVs), Portable Multimedia Players (PMPs), and portable broadcast devices has caused an increasing demand for the support of various receiving schemes in the digital broadcast service. 
     In order to fulfill such a demand, the Digital Video Broadcasting-Terrestrial (DVB-T2), which is a second generation European terrestrial wave digital broadcast standard, is preparing standards for a receiving scheme reusing the conventional home digital receiving antenna, a receiving scheme using multiple antennas in order to increase capacity, and a receiving scheme for a portable mobile terminal, respectively. DVB-T/H, which is a first generation terrestrial wave digital broadcast standard, takes only the two schemes including a stationary receiving scheme and a mobile receiving scheme into consideration. However, the DVB-T2 also includes a scheme of using multiple antennas, and considers a physical layer structure and a change of control information according to the physical layer structure as a main standardization job. 
     In the physical layer structure of the DVB-T2, a control channel is a channel for transmitting a control message with respect to a transmission scheme in the physical layer. In the control channel, a basic unit of a transmitted signal is a frame, which may include multiple services, and includes a service index, location information, a modulation scheme/coding rate, and a cell identifier (ID) of each service. In the control channel, the service configuration and related information may be different according to each frame. Therefore, for each frame, the control channel is transmitted separately from the data channel. 
     Referring to  FIG. 1 , a transmitter  102  transmits different broadcast services in multiple Radio Frequency (RF) bands, respectively, and a receiver  104  tunes to an RF containing a desired service and receives the desired service. For example, when the receiver  104  wants to receive the service  1 , the receiver  104  tunes to RF # 1 , obtains information, such as location information and modulation/coding scheme, relating to the service  1 , and then decodes the service  1 . 
     Referring to  FIG. 2A , the transmitter  202  divides a service (corresponding to each service in  FIG. 1 ), which includes an existing long packet configured by combining multiple RFs, into multiple short sub-slots, and then transmits the divided sub-slots through multiple RF bands. The receiver  204  detects the location of a pertinent service in each RF band including a desired service through the control information and then receives the pertinent service. In receiving the service  1 , the receiver  204  decodes the pertinent services in an order capable of receiving the sub-slots in the time domain, i.e., in the order of RF 1 , RF 4 , RF 3 , and RF 2 . Therefore, for the same quantity of service, transmission of a smaller quantity of data through multiple frequencies is expected to be capable of achieving more time and frequency diversity gains than simultaneous transmission of a large quantity of data by using a fixed RF for each service. Such a frame configuration scheme as described above is called Time-Frequency Slicing (TFS). 
     In the structure shown in  FIG. 2B , ten service packets are transmitted through four RFs. In such a TFS frame, all service packets are first allocated to one RF, and packets cyclic-shifted from the initial group of all the service packets are then allocated to an adjacent RF. When four RF bands are used as shown in  FIG. 2B , one service is transmitted through four RFs (RF 1 ˜RF 4 ). Therefore, each service basically includes four sub-slots. However, as in the service  3 , the service may include five sub-slots due to the cyclic shift. 
     Referring to  FIG. 2B , a P 1  signal  201  and a P 2  signal  203  are transmitted at the initial portion of each frame. The P 1  signal  201  may be used as a preamble for synchronization, and the P 2  signal  203  transmits control information for each service included in the current or next frame. The control information includes location information indicating the start point and the terminating point of data of each service. When the receiver switches the service channel while receiving the service, the receiver can receive the switched service only after acquiring the control information of the switched service. 
       FIG. 3  illustrates conventional service switching. When multiple frames (frame n, . . . , frame n+3) are being transmitted in the time domain, each frame includes a P 2  signal  303  to  311  at the initial portion thereof and multiple services following the P 2  signal. The frame may be transmitted in the FF mode or TFS mode, as shown in  FIG. 1  or  2 . However, for convenience of description, transmission in the FF mode will be taken into consideration in the following description. Further, for convenience of description, it is assumed that the P 2  signal indicates control information of the current frame. 
     Referring to  FIG. 3 , when the receiver switches the channel to another service while receiving a service at frame n ( 301 ), the receiver decodes the P 2  signal for receiving the switched service at the next frame. Since the P 2  signal  305  includes the scheduling information at frame (n+1), the receiver is unable to receive the switched service at frame (n+1) if the receiver fails to decode the P 2  signal  305 . Further, if the receiver continuously fails to decode the P 2  signal, that is, if the receiver fails to decode not only the P 2  signal  305  but also the P 2  signal  307  of frame (n+2), the receiver receives the switched service at frame (n+3) by using the control information  313  acquired from the P 2  signal  309  of frame (n+3). 
     According to the conventional systems described above, when a service switching occurs, the zapping time from the time point of the service switching to the time point of reception of the switched service may be too long according to whether the decoding of the P 2  signal is a success or failure. Therefore, there has been a request for a scheme for transmitting and receiving control information of switched service so that the receiver can efficiently receive the switched service when a service switching has occurred. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made to solve the above-mentioned problems, and the present invention provides a method and an apparatus for efficiently transmitting and receiving control information for receiving a service in a broadcast communication system. 
     Also, the present invention provides a method and an apparatus for efficiently transmitting and receiving service data including control information for receiving a service in a broadcast communication system. 
     The present invention also provides a method and an apparatus for transmitting and receiving control information of a switched service to enable efficient reception of the switched service, in response to the occurrence of a service switching in a broadcast communication system. 
     SUMMARY OF THE INVENTION 
     In accordance with an aspect of the present invention, there is provided a method of transmitting control information in a broadcast communication system, the method including the steps of inserting first control information for receiving at least one different service at a next frame in each of multiple service data pieces of a current frame; and transmitting a frame including the first control information. 
     In accordance with another aspect of the present invention, there is provided a method of receiving control information in a broadcast communication system, the method including the steps of receiving a current frame including multiple service data pieces in each of which first control information for receiving at least one different service at a next frame is inserted; acquiring the first control information from the received current frame when a service switching occurs; and receiving service data of the switched service by using the first control information. 
     In accordance with yet another aspect of the present invention, there is provided an apparatus for transmitting control information in a broadcast communication system, the apparatus including a control information processing unit for generating first control information for receiving at least one different service at a next frame and inserting the first control information in each of multiple service data pieces of a current frame; and a transmission unit for configuring a frame including the first control information in a predetermined format and transmitting the frame. 
     In accordance with a further aspect of the present invention, there is provided an apparatus for receiving control information in a broadcast communication system, the apparatus including a frame receiving unit for receiving a current frame including multiple service data pieces in each of which first control information for receiving at least one different service at a next frame is inserted; a service switching determiner for determining if a service switching to another service occurs during receiving of a service at the current frame; and a service decoder for acquiring the first control information from the received current frame when the service switching occurs, and receiving service data of the switched service by using the first control information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a conventional scheme of transmitting and receiving a broadcast service according to a Fixed Frequency (FF) mode in the 1 st  generation broadcast system; 
         FIG. 2A  illustrates a scheme of transmitting and receiving a broadcast service in the conventional 2 nd  generation broadcast communication system; 
         FIG. 2B  illustrates a transmission frame standard of the conventional TFS; 
         FIG. 3  illustrates conventional service switching; 
         FIG. 4A  illustrates a configuration of control information transmitted through each service according to service type when multiple services are transmitted according to a first embodiment of the present invention; 
         FIG. 4B  illustrates a switching from an existing service to a target service in a service switching according to the first embodiment of the present invention; 
         FIG. 5A  illustrates a configuration of control information transmitted through each service according to the service type when multiple services are transmitted according to a second embodiment of the present invention; 
         FIG. 5B  illustrates a switching from an existing service to a target service in a service switching according to the second embodiment of the present invention; 
         FIG. 6  is a flowchart illustrating the operation of a transmitter for transmitting a P 2  signal in a broadcast communication system to which the present invention is applied; 
         FIG. 7  is a flowchart illustrating the operation of a receiver for receiving a P 2  signal in a broadcast communication system to which the present invention is applied; 
         FIG. 8  is a flowchart illustrating the operation of a transmitter for transmitting control information according to the first embodiment of the present invention; 
         FIG. 9  is a flowchart illustrating the operation of a receiver for receiving control information according to the first embodiment of the present invention; 
         FIG. 10  is a flowchart illustrating the operation of a transmitter transmitting control information according to the second embodiment of the present invention; 
         FIG. 11  is a flowchart illustrating the operation of a receiver for receiving control information according to the second embodiment of the present invention; 
         FIG. 12  is a block diagram illustrating the structure of a transmitter according to the first embodiment of the present invention; 
         FIG. 13  is a block diagram illustrating the structure of a transmitter according to the second embodiment of the present invention; and 
         FIG. 14  is a block diagram illustrating a structure of a receiver according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted to avoid making the subject matter of the present invention unclear. 
     The present invention provides a signaling technique by which, in the case of the occurrence of a service switching due to user&#39;s switching of the service channel that the user wants to receive, even when a receiver has failed to decode a P 2  signal including control information, the receiver can acquire control information of the next frame. Specifically, the present invention provides an in-band signaling scheme in which service data of a transmitted frame includes control information indicating scheduling information of the frame. 
     In the in-band signaling, the service type is divided into an anchor service, a primary service, and a secondary service, and the control information transmitted through each service has different configurations according to the service type. Further, by appointing the number of primary services, signaling is performed based on the result of a comparison between the total number of the services transmitted through frames and the predetermined number of primary services. 
     Referring to  FIG. 4A , based on an assumption that a total of (N+K) services are transmitted through frames, N primary services (1 to N services)  410  and K secondary services ((N+1) to (N+K) services)  430  exist, and one service from among the N primary services  410  is appointed as an anchor service  410   a.    
     As noted by the arrows between the N primary services in  FIG. 4A , each of the N primary services include scheduling information relating to all the other primary services as well as itself. One primary service from among the N primary services is appointed as the anchor service, and the anchor service includes not only the scheduling information of all the primary services but also scheduling information of the K secondary services. Meanwhile, the secondary services transmit scheduling information of the anchor service including themselves. 
     Therefore, when the total number of transmitted services does not exceed N, all the transmitted services become primary services and each transmitted service includes scheduling information of all the services. Meanwhile, when the total number of transmitted services exceeds N, that is, when (N+K) and K secondary services exist as well as the primary services, one service is determined as the anchor service from among the N primary services, and the anchor service includes control information of all the services including the primary services and the secondary services. 
     In  FIG. 4B , a service is transmitted through a Packet Layer Pipe (PLP), which is a Time Division Multiplexing (TDM) channel, and a target/anchor PLP refers to a target/anchor service. However, the present invention is not limited to the case of using the PLP and is also applicable to other types of services. 
     In  FIG. 4B  it is assumed that each of the P 2  signals  403  to  411  includes control information of a current frame, and the control information included in the service data indicates scheduling information of a next frame. Also, it is assumed that the number N of primary services is 30. Further, it is assumed that decoding of the P 2  signals  405  and  407  of frames (n+1) and (n+2) has been proved a failure. 
     First, if the number of transmitted services does not exceed the number N of the primary services, when a service switching occurs at frame n ( 401 ), the service received at frame n becomes a primary service and the receiver acquires control information of a target service by decoding of the primary service. That is, since the control information acquired through an in-band signaling at frame n indicates control information of the next frame, the receiver can instantly receive the switched service at frame (n+1). As a result, when decoding of the two continuous P 2  signals  405  and  407  is a continuous failure, the signaling scheme of the preferred embodiment can achieve a zapping time two frames faster than the conventional signaling scheme depending on only the P 2  signal. Even when decoding of the P 2  signal  405  is a failure and decoding of the next P 2  signal  407  is a success, it is possible to receive the switched service at frame (n+1) instantly after the occurrence of service switching. Therefore, the present signaling scheme can achieve a zapping time one frame faster than the conventional signaling scheme depending on only the P 2  signal. 
     Further, when the total number of transmitted services exceeds N, the receiver acquires control information of the anchor service by decoding the existing service at frame n and acquires control information of the target service by receiving the anchor service at frame (n+1). Therefore, the receiver can receive the switched service from frame (n+2). 
     Meanwhile, the in-band signaling having a very excellent performance in view of the zapping time corresponds to the case in which each service includes control information of all services. However, since this scheme requires a vary large overhead, there is inevitably a limitation in the number of services capable of satisfying an allowable overhead. For example, 30 services are considered and an overhead for each service is assumed to be 50 bits. When each service includes control information of all the 30 services, the total quantity of the overhead is 45,000 bits (30*(30*50)=45,000), and the overhead ratio is calculated as 0.125. Therefore, the overhead ratio satisfies the below-par value of 0.25, which is the allowable maximum overhead ratio. When extended to two times the number of services, that is, when 60 services are supported, the overhead ratio has a value of 0.5, a value obtained from 60*(60*50)=180,000 bits, which exceeds the threshold, i.e. the allowable maximum overhead ratio. Therefore, the maximum number of supportable services satisfying the overhead threshold is 42. 
     Therefore, there is a need for a signaling technique that can support as many services as possible while allowing each service to include control information of many services, so as to achieve a good performance in the zapping time. 
     Referring to  FIG. 5A , a total of K services are transmitted and (2N+1) services can be supported by the in-band signaling. The (2N+1) services include one primary service and 2N secondary services. One primary service appointed from among the (2N+1) services includes control information of all the services. 
     Referring to  FIG. 5A , the (2N+1) services are divided into two groups  510  and  530 , and the primary service  510   a  belongs to both of the two groups and serves as a connection point between the two groups. Further, when the (2N+1) services are arranged in turn according to the size of the service index, first N secondary services arranged in turn from the service having the smallest index belong to group # 1   510 , and next N secondary services belong to group # 2   530 , while the service having the index of (2N+1) is a primary service  510   a  and belongs to both groups. Therefore, each group includes (N+1) services including one primary service and N secondary services. Data of each service includes scheduling information for all the services of the group, to which the service belongs, and the primary service repeatedly belongs to every group. As a result, the primary service includes control information of all the services belonging to all the groups. 
     In other words, the N secondary services belonging to each group have scheduling information for all the services belonging to the group. That is, each secondary service includes control information of the primary service and all the secondary services including itself belonging to its group. In contrast, the primary service includes control information of all the services including itself belonging to all the groups. 
     For comparison with the configuration shown in  FIG. 4A  according to the first embodiment of the present invention, consider a service having a service index of (N+3) belonging to group # 2  in the second embodiment of the present invention shown in  FIG. 5A . In the first embodiment, the receiver should acquire the control information of a target service through the anchor service, in order to determine if the service having a service index of (N+3) switches to another service within the group including the N services or another service out of the group including the N services. In contrast, according to the second embodiment, for example, in order to perform a service switching from a service having a service index of (N+3) belonging to group # 2  to a service belonging to group # 1 , it is necessary to acquire control information for a target service through a primary service having a service index of (2N+1). However, it is possible to instantly, i.e. without acquisition of additional control information, switch from the service having the service index of (N+3) belonging to group # 2  to a target service belonging to the same group, i.e. group # 2 . 
     That is, for the service switching between groups, scheduling information for the target service can be obtained through decoding of an additional service, such as the primary service. However, in relation to the service switching within the same group, it is possible to directly obtain scheduling information of the target service without receiving an additional service. 
     Further, consider the same signaling overhead ratio while maintaining the basic configuration in which each service includes control information of other services. For example, assuming that the maximum number of supportable services capable of satisfying the overhead ratio of below par 0.25% is 42, the second embodiment of the present invention can support a total of 60 services through two groups each including 30 services at an overhead ratio below par 0.25%. Specifically, the quantity of required overhead corresponds to 90,000 bits (2*30*(30*50)=90,000), which is similar to 88,200 bits (42*(42*50)=88,200) when each of the 42 services includes control information of all the services. That is, the configuration shown in  FIG. 5A  can support  18  more services than the case of supporting  42  services, with nearly the same assumption in view of the signaling configuration and the overhead. 
     In  FIG. 5B  it is assumed that each of the P 2  signals  503  to  511  includes control information of a current frame, and the control information included in the service data indicates scheduling information of a next frame. Further, it is assumed that decoding of the P 2  signals  505  and  507  of frames (n+1) and (n+2) has been proved a failure. Also, it is assumed that the number of secondary services for each group is N. 
     Referring to  FIG. 5B , when the service that the receiver is currently receiving and the target service to which the receiver wants to switch belong to the same group, the current service includes control information of the target service. Therefore, when a service switching  501  occurs at frame n ( 501 ), the receiver can receive the target service at frame (n+1), which is the next frame. That is, since the control information acquired through an in-band signaling from the current service at frame n indicates control information of the next frame, the receiver can instantly receive the switched service at frame (n+1). Therefore, in the case of a continuous failure in decoding two P 2  signals  505  and  507 , the two frames can achieve faster zapping time in the scheme of the preferred embodiment than in the conventional signaling scheme depending on only the P 2  signal. 
     Further, when the service being currently received and the target service to which switching is required belong to two different groups, the receiver uses the primary service in order to get control information of the target service. That is, the receiver acquires control information for the primary service by decoding the existing service at frame n, and acquires control information for the target service by receiving the primary service at frame (n+1). Therefore, from frame (n+2), the receiver can receive the switched service. Accordingly, in the case of a continuous failure in decoding the two P 2  signals  505  and  507 , the scheme of the preferred embodiment can achieve zapping time one frame faster than the conventional signaling scheme depending on only the P 2  signal. 
     Referring to  FIG. 6 , in order to enable a receiver to acquire control information for a target service when the receiver switches from a service being received to the target service, a transmitter needs to transmit a P 2  signal including control information through a separate channel different from the data channel. Therefore, in step  602 , the transmitter configures a P 2  signal including control information indicating scheduling information for services and inserts the P 2  signal in the frame. Then, in step  604 , the transmitter transmits the frame including the P 2  signal to the receiver. 
     Referring to  FIG. 7 , in step  702 , the receiver receives service n at the current frame. Then, in step  704 , the receiver determines if a service switching has occurred during receiving of service n. When a service switching has occurred during receiving of service n, the receiver decodes a P 2  signal including control information for the switched service at the next frame in order to acquire the P 2  signal in step  706 . When a service switching has not occurred during the receiving of service n, the receiver returns to step  702 , in which the receiver continuously receives service n. 
     In step  708 , the receiver determines if the decoding of the P 2  signal is successful. When the decoding of the P 2  signal has been proved a failure, the receiver returns to step  706 , in which the receiver tries to decode the P 2  signal again. When the decoding of the P 2  signal has been proved a success as a result of the determination in step  708 , the receiver acquires control information for the target service m from the decoded signal P 2  and receives the target service m at the location at which the target service m is transmitted at the next frame according to the control information in step  710 . 
     In  FIG. 8 , the transmitter transmits service data including control information according to the scheme as described above with reference to  FIGS. 4A and 4B . 
     Referring to  FIG. 8 , in step  802 , the transmitter determines the number N of primary services and parameters relating to the frame configuration, such as the index of an anchor service. Then, in step  804 , the transmitter configures the P 2  signal in consideration of the determined parameters. At this time, the number N of primary services may be predetermined between the transmitter and the receiver, in which case it is unnecessary to perform a separate signaling for the parameter N indicating the number of primary services. Further, in selecting one service from among the primary services as an anchor service, it is possible to use a service index predetermined between the transmitter and the receiver, which makes it unnecessary to perform a separate signaling of related information. For example, in an arrangement of indexes of N primary services according to the magnitude of the index number, the first index or the last index (corresponding to the anchor service in  FIG. 4A ) may be predetermined to be used for the anchor service. 
     In step  806 , control information indicating scheduling information on other services to be included in each service according to its service type based on the classification criterion illustrated in  FIG. 4A  is inserted in each service data. In step  808 , the transmitter configures a frame including the P 2  signal and service data and transmits it to the receiver. 
     In  FIG. 9 , the receiver receives service data including control information according to the scheme as described above with reference to  FIGS. 4A and 4B . 
     Referring to  FIG. 9 , in step  902 , the receiver receives service n at frame n (i.e. at current frame). Then, in step  904 , the receiver determines if a service switching to another service during the service receiving at frame n has occurred. When a service switching has not occurred, the receiver returns to step  902 , in which the receiver continuously receives service n at the next frame. In contrast, when a service switching has occurred, the receiver proceeds to step  906 , in which the receiver completes decoding of service n at the current frame. Thereafter, in step  908 , the receiver compares the total number of the services transmitted from the transmitter with the number N of the primary services either pre-promised between the transmitter and the receiver or acquired through a separate signaling. When the total number of services does not exceed the number N of primary services, the receiver proceeds to step  910 , in which the receiver acquires control information of service m, which is the target service, at the current frame n. Then, in step  912 , the receiver receives service m by using the control information. 
     Meanwhile, as a result of the comparison in step  908 , when the total number of services exceeds the number N of primary services, the receiver proceeds to step  914 , in which the receiver acquires control information for the anchor service through the decoded service n. Then, in step  916 , by using the control information for the anchor service, the receiver decodes the anchor service at the next frame, i.e. at frame (n+1). In step  918 , the receiver acquires control information of service m from the decoded anchor service. In step  920 , the receiver receives service m at the next frame, i.e. at frame (n+2), by using the control information. 
     In  FIG. 10 , in regard to the second embodiment, the transmitter transmits service data including control information according to the scheme as described above with reference to  FIGS. 5A and 5B . 
     Referring to  FIG. 10 , in step  1002 , the transmitter determines parameters relating to the frame configuration, such as the number of groups, the group size N, and an index of a primary service. In step  1004 , the transmitter configures a P 2  signal in consideration of the determined parameters. The group size N, which corresponds to the number of services included in each group, and the number of groups may be predetermined as a number promised between the transmitter and the receiver, in which case it is unnecessary to perform a separate signaling of the parameters relating to the number of groups and the group size. Further, in determining one service from among the services as a primary service, it is possible to use a service index predetermined between the transmitter and the receiver, which makes it unnecessary to perform a separate signaling of related information. For example, in an arrangement of indexes of (2N+1) service indexes according to the magnitude of the index, the first index or the last index (corresponding to the primary service in  FIG. 5A ) may be predetermined to be used for the primary service. 
     In step  1006 , control information indicating scheduling information on other services to be included in each service according to the service type based on a standard set in  FIG. 5A  is inserted in each service data. That is, the service data of the primary service includes control information of all the services belonging to all of the groups. Further, service data of the secondary services belonging to each group includes control information of all the services belonging to the group. In step  1008 , the transmitter transmits a frame including the P 2  signal and service data including the control information to the receiver. 
     In  FIG. 11 , the receiver receives control information included in service data according to the scheme as described above with reference to  FIGS. 5A and 5B . 
     Referring to  FIG. 11 , in step  1102 , the receiver receives service n at frame n (i.e. at a current frame). Then, in step  1104 , the receiver determines if service n switches to another service during the service receiving at frame n has occurred. When a service switching has not occurred, the receiver returns to step  1102 , in which the receiver continuously receives service n at the next frame. In contrast, when a service switching has occurred, the receiver proceeds to step  1106 , in which the receiver completes decoding of service n at the current frame. Thereafter, in step  1108 , the receiver determines if service m, which is a target service to be newly received, exists within the same group as the group of the service n. As a result of the determination in step  1108 , when the target service exists within the same group, the receiver proceeds to step  1110 , in which the receiver acquires control information of service m at the current frame. Then, in step  1112 , the receiver receives service m by using the control information. 
     Meanwhile, as a result of the determination in step  1108 , when it is determined that service m belongs to a group different from the group of service n, the receiver proceeds to step  1114 , in which the receiver acquires control information for the primary service through the decoding of service n. Then, in step  1116 , by using the control information, the receiver decodes the primary service at the next frame, i.e. at frame (n+1). In step  1118 , the receiver acquires control information of service m from the decoded primary service. In step  1120 , the receiver receives service m at the next frame, i.e. at frame (n+2), by using the control information. 
     The structure shown in  FIG. 12  corresponds to a structure for performing the operation as shown in  FIG. 8 . 
     Referring to  FIG. 12 , a P 2  signal generator  1206  generates a P 2  signal by using the parameters determined by an anchor service index determiner  1202  and a primary service number determiner  1204 . The anchor service control information inserter  1212  inserts control information, which is to be included in the anchor service, in the service data of the anchor service by using information input from the primary service number determiner  1201  and the anchor service index determiner  1202  and information input from a service control information generator  1208  and a service data generator  1210 . The service control information generator  1208  generates control information indicating scheduling information of all the services for the anchor service. 
     Meanwhile, a primary service control information inserter  1214  inserts control information, which is to be included in the primary service, in the data of the primary service by using information input from the anchor service index determiner  1204 , the service control information generator  1208 , and the service data generator  1210 . For the primary service, the service control information generator  1208  generates control information indicating scheduling information of all the primary services. Finally, a secondary service control information inserter  1216  inserts control information, which is to be included in the secondary service, in the data of the secondary service by using information input from the primary service number determiner  1202 , the service control information generator  1208 , and the service data generator  1210 . For the secondary service, the service control information generator  1208  generates control information indicating scheduling information of the anchor service and a pertinent secondary service. 
     An FF/TFS frame configuration unit  1218  configures an FF or TFS frame by using service data of all the services in which the control information has been inserted, together with a P 2  signal. A frame transmitter  1220  transmits the configured FF or TFS frame to a receiver. 
     The structure shown in  FIG. 13  corresponds to a structure for performing the operation described in  FIG. 10 . 
     Referring to  FIG. 13 , a P 2  signal generator  1306  generates a P 2  signal by using the parameters determined by a primary service index determiner  1304  and a group number/size determiner  1302 . The primary service control information inserter  1312  inserts control information, which is to be included in the primary service, in the service data of the primary service by using information input from the primary service index determiner  1304  and information input from a service control information generator  1308  and a service data generator  1310 . The service control information generator  1308  generates control information indicating scheduling information of all the services including the primary service for the primary service. 
     Meanwhile, a secondary service control information inserter  1314  inserts control information, which is to be included in the secondary service, in the data of the secondary service by using information input from the group number/size determiner  1302 , the service control information generator  1308 , and the service data generator  1310 . For each secondary service, the service control information generator  1308  generates scheduling information of all the services (i.e. all the secondary services and the primary service) within the group including the secondary service. 
     Further, an FF/TFS frame configuration unit  1318  configures an FF or TFS frame by using service data of all the services in which the control information has been inserted, together with a P 2  signal. A frame transmitter  1320  transmits the configured FF or TFS frame to a receiver. 
     Referring to  FIG. 14 , the frame receiver  1406  receives a frame transmitted from the transmitter and delivers the received frame to the service decoder  1404 , and the service switching determiner  1402  determines if a service switching to a target service has occurred during reception of the service at the frame. 
     For the first embodiment described above with reference to  FIG. 9 , the service decoder  1404  decodes the service at the current frame and acquires control information for the anchor service or target service from the decoded service. When the total number of services exceeds the number of primary services, the service decoder  1404  decodes the anchor service by using the acquired control information for the anchor service, and acquires control information for the target service from the decoded anchor service. Then, the service decoder  1404  receives the target service by using the control information for the target service. 
     For the second embodiment described above with reference to  FIG. 11 , the service decoder  1404  decodes the service at the current frame and acquires control information for the primary service or target service from the decoded service. When the target service belongs to a group different from the group including the current service, the service decoder  1404  decodes the primary service by using the control information for the primary service, and then acquires control information for the target service from the decoded primary service. Then, the service decoder  1404  receives the target service by using the control information for the target service. 
     According to the present invention, it is possible to efficiently transmit and receive a frame, which includes multiple services configured through a combination of one or more RFs. Therefore, the present invention enables rapid receiving of a switched service in the case of service switching. 
     While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.