Abstract:
A method and apparatus are provided for transmitting and receiving System Information (SI) in a mobile communication system. The method for receiving the SI by a User Equipment (UE) includes receiving, by the UE, at a fixedly scheduled sub-frame of a predetermined radio frame within a Primary Broadcast CHannel (P-BCH) transmission period, the SI including first partial bits of a System Frame Number (SFN), the first partial bits indicating a repeated value; and acquiring, by the UE, second partial bits of the SFN in the predetermined radio frame by decoding the P-BCH, the second partial bits indicating a different value.

Description:
PRIORITY 
     This application is a Continuation of U.S. application Ser. No. 12/027,542, which issued as U.S. Pat. No. 8,169,986 on May 1, 2012, and claims priority under 35 U.S.C. §119(a) to Korean Patent Application Serial No. 2007-13863, which was filed in the Korean Intellectual Property Office on Feb. 9, 2007, the entire disclosure of each of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a mobile communication system. More particularly, the present invention relates to a method for efficiently broadcasting system information in a cell and a method for receiving the system information in a User Equipment (UE). 
     2. Description of the Related Art 
     The Universal Mobile Telecommunications System (UMTS) is a 3 rd  Generation (3G) asynchronous mobile communication system operating in Wideband Code Division Multiple Access (WCDMA), based on European mobile communication systems, Global System for Mobile Communications (GSM) and General Packet Radio Services (GPRS). The 3 rd  Generation Partnership Project (3GPP) that standardized UMTS is now discussing Long Term Evolution (LTE) as the next generation of UMTS, known as Evolved UMTS. The 3GPP LTE is a technology for enabling packet communications at or above 100 Mbps, aiming at commercialization by 2010. For deploying the LTE system, many communication schemes have been proposed. Among them are schemes of reducing the number of nodes on a communication line by simplifying a network configuration or of optimizing radio protocols for radio channels. 
       FIG. 1  is a diagram illustrating an Evolved UMTS system to which the present invention is applied. 
     Referring to  FIG. 1 , each of Evolved UMTS Radio Access Networks (E-UTRANs or E-RANs)  110  is simplified to a 2-node structure including Evolved Node Bs (ENBs)  120  and  122  and an anchor node  130 , or ENBs  124 ,  126  and  128  and an anchor node  132 . A User Equipment (UE)  101  is connected to an Internet Protocol (IP) network  114  via the E-UTRAN  110 . The ENBs  120  to  128  correspond to legacy Node Bs in the UMTS system and are connected to the UE  101  via radio channels. Compared to the legacy Node Bs, the ENBs  120  to  128  play a more complex role. Since all user traffic including real-time service such as Voice Over IP (VoIP) is serviced on shared channels in the 3GPP LTE, an entity for collecting the status information of UEs and scheduling them is required and the ENBs  120  to  128  are responsible for the scheduling. Generally, an ENB controls a plurality of cells. Generally, the ENBs  120  to  128  perform Adaptive Modulation and Coding (AMC) by adaptively selecting a modulation scheme and a channel coding rate for a UE according to the channel status of the UE. As with High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA) of UMTS (also referred to as Enhanced Dedicated CHannel (EDCH)), the LTE system uses Hybrid Automatic Repeat reQuest (HARQ) between the ENBs  120  to  128  and the UE  101 . Considering that a variety of Quality of Service (QoS) requirements cannot be fulfilled with HARQ alone, a high layer may perform an outer ARQ between the UE  101  and the ENBs  120  to  128 . HARQ is a technique for increasing reception success rate by soft-combining previous received data with retransmitted data without discarding the previous data. High-speed packet communication systems such as HSDPA and EDCH use HARQ to increase transmission efficiency. To realize a data rate of up to 100 Mbps, it is expected that the LTE system will adopt Orthogonal Frequency Division Multiplexing (OFDM) in a 20-MHz bandwidth as a radio access technology. 
       FIG. 2  illustrates system information broadcast in cells. 
     Referring to  FIG. 2 , reference numeral  201  denotes an ENB and reference numerals  211 ,  213  and  215  denote transmissions of system information from first, second and third cells, CELL # 1 , CELL # 2  and CELL # 3 , respectively. The system information includes essential physical parameters and high-layer parameters common to UEs in a cell so that the UEs can receive a service in the cell. The physical parameters include, but are not limited to, the bandwidth of the cell, a Cyclic Prefix (CP) length, a physical channel configuration, the number of transmit antennas, and a System Frame Number (SFN), for example. The high-layer parameters may include a measurement Identifier (ID) and scheduling information about frequency or time resources in which other high-layer parameters are transmitted. A Primary Broadcast CHannel (P-BCH) carries the system information. To stably reach a cell boundary, the P-BCH needs a high transmit power or a robust Modulation and Coding Scheme (MCS) level. 
       FIG. 3  illustrates an exemplary method for transmitting system information. 
     Referring to  FIG. 3 , a 10-ms radio frame  301  includes ten subframes  303 . It is assumed herein that a P-BCH carries system information in a 1.25-MHz subframe in every radio frame. As described before with reference to  FIG. 2 , to stably reach a cell boundary, the P-BCH carries a limited number of bits in a subframe. For example, a very low coding rate is applied to the P-BCH to achieve a 1% BLock Error Rate (BLER) for 98% of the cell coverage area and the P-BCH may deliver no more than 20 to 30 bits of information in a 1-ms subframe with a 1.25 MHz of bandwidth. The limitation on the number of P-BCH information bits makes it impossible to transmit all of the necessary system information on the P-BCH. If system information is ever managed to fit the allowed number of information bits, the system information size cannot be extended for the next transmission on the P-BCH. Accordingly, there is a need for a method for transmitting more information bits on the P-BCH in a given bandwidth. 
     SUMMARY OF THE INVENTION 
     The present invention is to address at least the problems and/or disadvantages described above and to provide at least the advantages described below. 
     Accordingly, an aspect of the present invention is to provide a method and apparatus for transmitting a greater number of information bits on a P-BCH with a predetermined bandwidth in a cell and a method and apparatus for receiving system information in a UE. 
     In accordance with an aspect of the present invention, a method for receiving System Information (SI) by a User Equipment (UE) in a mobile communication system is provided. The method includes receiving, by the UE, at a fixedly scheduled sub-frame of a predetermined radio frame within a Primary Broadcast CHannel (P-BCH) transmission period, the SI including first partial bits of a System Frame Number (SFN), the first partial bits indicating a repeated value; and acquiring, by the UE, second partial bits of the SFN in the predetermined radio frame by decoding the P-BCH, the second partial bits indicating different values. 
     In accordance with another aspect of the present invention, a method for transmitting SI by a Node B in a mobile communication system is provided. The method includes encoding, by the Node B, second partial bits of an SFN in a predetermined radio frame within a P-BCH transmission period, the second partial bits indicating different values; and transmitting, by the Node B, at a fixedly scheduled sub-frame of the predetermined radio frame, the encoded second partial bits and the SI including first partial bits of the SFN, the first partial bits indicating a repeated value 
     In accordance with another aspect of the present invention, a UE is provided for receiving SI in a mobile communication system. The UE includes a receiver that receives, at a fixedly scheduled sub-frame of a predetermined radio frame within a P-BCH transmission period, the SI including first partial bits of an SFN, the first partial bits indicating a repeated value; and a controller that acquires second partial bits of the SFN in the predetermined radio frame after decoding the P-BCH, the second partial bits indicating different values. 
     In accordance with another aspect of the present invention, a Node B is provided for transmitting SI in a mobile communication system. The Node B includes an encoder that encodes second partial bits of an SFN in a predetermined radio frame within a P-BCH transmission period, the second partial bits indicating different values; and a transmitter that transmits the encoded second partial bits and the SI including first partial bits of the SFN at a fixedly scheduled sub-frame of the predetermined radio frame, the first partial bits indicating a repeated value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of certain exemplary embodiments 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 3GPP LTE system according to an embodiment of the present invention; 
         FIG. 2  illustrates system information broadcast in cells; 
         FIG. 3  illustrates a method for transmitting system information; 
         FIG. 4  is a diagram illustrating a method for transmitting system information and a method for receiving the system information in a UE according to an embodiment of the present invention; 
         FIG. 5  is a flowchart of an operation of an ENB according to an embodiment of the present invention; 
         FIG. 6  is a block diagram of an ENB apparatus according to an embodiment of the present invention; 
         FIG. 7  is a flowchart of an operation of the UE according to an embodiment of the present invention; 
         FIG. 8  is a block diagram of a UE apparatus according to an embodiment of the present invention; 
         FIG. 9  is a diagram illustrating a method for transmitting system information and a method for receiving the system information in the UE according to an embodiment of the present invention; 
         FIG. 10  is a flowchart of an operation of the ENB according to an embodiment of the present invention; 
         FIG. 11  is a block diagram of an ENB apparatus according to an embodiment of the present invention; 
         FIGS. 12A and 12B  are a flowchart of an operation of the UE according to an embodiment of the present invention; and 
         FIG. 13  is a block diagram of a UE apparatus according to an embodiment of the present invention. 
     
    
    
     Throughout the drawings, the same drawing reference numerals will be understood to refer to the same elements, features and structures. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The matters defined in the description such as detailed constructions and elements are provided to assist in a comprehensive understanding of certain embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness. 
     While certain embodiments of the present invention will be described in the context of a 3GPP LTE system evolved from a 3GPP UMTS system, it is to be clearly understood that the present invention is applicable to other mobile communication systems as well. 
       FIG. 4  is a diagram illustrating a method for transmitting system information and a method for receiving the system information in a UE according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 4 , it is assumed herein that a 10-ms radio frame  401  includes ten subframes  403  and a P-BCH carries system information in a 1.25-MHz subframe of every radio frame. Reference numeral  411  denotes an SFN encoded in a predetermined coding scheme and transmitted in predetermined resources of the 1.25-MHz subframe. The resources can be frequency resources, a scrambling code, or the like. Reference numeral  413  denotes P-BCH information that has the same value during a P-BCH transmission period other than the SFNs. The P-BCH information  413  is encoded in a different coding scheme/coding rate from that of the SFN  411  and transmitted in different resources from those of the SFN  411  in the 1.25 MHz subframe. 
     If a UE receives system information from an ENB at a P-BCH transmission time  421 , the UE acquires an SFN  431 , SFN # 1000 , and the P-BCH information  413  by decoding and interpreting the system information in predetermined resources of 1.25 MHz (i.e. SFN transmission resources and other P-BCH transmission resources) according to a predetermined method. If the UE fails to receive the P-BCH information  413  at the P-BCH transmission time  421 , that is, the P-BCH information  413  turns out to have errors in a Cyclic Redundancy Check (CRC) check, the UE stores the P-BCH information  413  in a buffer, receives the P-BCH information  413  at the next P-BCH transmission time  423 , and combines the stored P-BCH information  413  with the received P-BCH information  413 . 
     The UE checks the continuity of SFNs received and decoded/interpreted at the P-BCH transmission times  421  and  423 , to thereby detect and correct reception errors in the SFNs if there are any reception errors. For instance, if the SFNs are # 1000  and # 1001 , they are successive, which implies successful reception of the SFNs  431  and  433 . Thus, the UE applies the SFNs, considering that the SFNs have been successfully acquired. On the other hand, if the SFNs are not successive (e.g. # 1000  and # 1200 ), the UE receives an SFN  435  at the next P-BCH transmission time  425  and detects and corrects reception errors in the SFNs. If the SFN  435  is # 1002 , the UE determines that SFN # 1200  received at the P-BCH transmission time  423  is wrong and corrects the SFN to # 1001 . 
       FIG. 5  is a flowchart of an operation of an ENB according to the exemplary embodiment of the present invention. 
     Referring to  FIG. 5 , when determining to transmit P-BCH information and an SFN in step  501 , the ENB encodes the P-BCH information and the SFN in predetermined coding methods/coding rates in step  511  and transmits the encoded P-BCH information and SFN in respective predetermined frequency/time resources in step  513 . Considering that a UE will combine the P-BCH information, the ENB transmits the P-BCH at a lower transmit power level or using an appropriate MCS level so that the P-BCH can carry more information bits. 
       FIG. 6  is a block diagram of an ENB apparatus according to the exemplary embodiment of the present invention. 
     Referring to  FIG. 6 , an SFN manager  601  is a function block for controlling and managing SFNs. The SFN manager  601  increases an SFN every radio frame. A P-BCH manager  603  controls and manages P-BCH information other than the SFNs. A coder  621  encodes the SFNs and the P-BCH information at predetermined respective coding rates according to predetermined respective coding methods. A controller  611  controls transmission timings of the SFNs and the P-BCH information from the SFN manager  601  and the P-BCH manager  603  and controls the coding methods and coding rates of the coder  621 . A transmitter  631  transmits the coded SFNs and the P-BCH information received from the coder  621  to a cell. 
       FIG. 7  is a flowchart of an operation of the UE according to the exemplary embodiment of the present invention. 
     Referring to  FIG. 7 , when determining that an SFN or P-BCH information needs to be received in step  701 , the UE determines in step  711  whether SFN information of a serving cell has been acquired. If the SFN information has not been acquired, the UE receives in step  731  an SFN and P-BCH information in predetermined respective resources using predetermined respective coding methods/coding rates. 
     In step  733 , the UE determines whether the P-BCH information has been successfully received by such as CRC error. If the P-BCH information has been successfully received, the UE receives in step  751 N SFNs (N&gt;=1) in next P-BCH transmission period and detects and corrects in step  753  SFN reception errors by checking the continuity of the received SFNs. For example, for N=1, if the SFN received in step  731  is SFN # 1000  and the SFN received in step  751  is SFN # 1001 , the UE determines that the SFN information has been successfully acquired because the SFNs are successive. For N=2, if the SFN received in step  731  is SFN # 1000  and the SFNs received in step  751  are SFN # 1200  and SFN # 1002 , the UE determines that SFN # 1200  is incorrect and corrects this SFN to # 1001 . 
     In step  755 , the UE checks the continuity of ordered SFNs resulting from step  753  and determines whether the SFN information has been successfully received. If the ordered SFNs are successive, the UE applies in step  757  the SFNs, considering that the SFN information has been successfully acquired. If it is determined in step  755  that the SFN information acquisition has been failed, the UE returns to step  751  and repeats  751  to  755 . 
     If a CRC has occurred to the P-BCH information in step  733 , the UE receives in step  741  an SFN and P-BCH information in the next transmission period and combines in step  743  the received P-BCH information with P-BCH information received in a previous transmission period. In step  745 , the UE checks the result of the combining. If the combining result tells that the P-BCH information has been successfully received (i.e. without a CRC error), the UE goes to step  753 . If the reception of the P-BCH information failed (i.e. a CRC error has occurred), the UE returns to step  741 . 
     If the UE has already acquired the SFN information of the cell in step  711 , the UE receives in step  721  only P-BCH information in predetermined resources using a predetermined coding method and coding rate. If the UE has failed to receive the P-BCH information successfully, in step  723  the UE receives P-BCH information in the next transmission period and combines the received P-BCH information with previous P-BCH information. 
       FIG. 8  is a block diagram of a UE apparatus according to the exemplary embodiment of the present invention. 
     Referring to  FIG. 8 , a receiver  811  receives system information from a cell. A controller  821  controls the application of a decoding method and a decoding rate to the system information. The controller  821  performs the control operation so that different decoding methods and decoding rates are applied to the SFN and P-BCH information. A decoder  831  decodes the SFN and the P-BCH information under the control of the controller  821  and provides the decoded SFN to an SFN manager  841  and the decoded P-BCH information to a P-BCH manager  843 . The SFN manager  841  checks the continuity of received SFNs and according to the result, the SFN manager  841  can additionally receive SFNs in next transmission periods through the controller  821 . If the P-BCH information reception failed, the P-BCH manager  843  stores the received P-BCH information in a buffer  845  and combines the stored P-BCH information with P-BCH information received in the next transmission period. 
       FIG. 9  is a diagram illustrating a method for transmitting system information and a method for receiving the system information in the UE according to another exemplary embodiment of the present invention. 
     Referring to  FIG. 9 , it is assumed herein that a 10-ms radio frame  901  includes ten subframes  903  and a P-BCH carries system information in a 1.25-MHz subframe of every radio frame. Reference numeral  911  denotes an SFN offset encoded in a predetermined coding scheme and transmitted in predetermined resources in the 1.25-MHz subframe. The resources can be frequency resources, a scrambling code, or the like. Reference numeral  913  denotes P-BCH information. The P-BCH information  913  is encoded in a different coding scheme/coding rate from that of the SFN offset  911  and transmitted in different resources from those of the SFN offset  911  in the 1.25 MHz subframe. The coding method can be repetition. The P-BCH information  913  includes a reference SFN instead of an actual SFN. The reference SFN is identical during one SFN offset period. The actual SFN is obtained by adding the reference SFN and an SFN offset. 
     For example, if an actual SFN is # 1000  at time  921  and an SFN offset is represented in two bits, the SFN offset is one of {0, 1, 2, 3} and a reference SFN is kept to be # 1000  during one SFN offset period. The SFN offset and the reference SFN are carried on the P-BCH. That is, the P-BCH delivers the same reference SFN, SFN # 1000 , in radio frames having SFN # 1000  to SFN # 1003 , and SNF offsets 0, 1, 2 and 3, respectively, at the transmission times of SFN # 1000  to SFN # 1003 . Since the same reference SFN, SFN # 1000  applies to the radio frames SFN # 1000  to SFN # 1003 , the UE can combine P-BCH information received in the radio frames SFN # 1000  to SFN # 1003 . As described before, an actual SFN is calculated by adding a reference SFN and an SFN offset received on the P-BCH in a radio frame. 
     If the UE receives system information at a P-BCH transmission time  921 , the UE acquires an SFN offset  931 , SFN offset 0, by decoding and interpreting the system information in predetermined resources of 1.25 MHz (i.e. SFN transmission resources and other P-BCH transmission resources) according to a predetermined method. If the UE fails to receive the P-BCH information  913 , that is, the P-BCH information  913  has a CRC error, the UE stores the P-BCH information  913  in a buffer, receives the P-BCH information  913  at the next P-BCH transmission time  923 , and combines the stored P-BCH information  913  with the received P-BCH information  913 . 
     The UE receives an SFN offset  933 , SFN offset 1 at the P-BCH transmission time  923  and SFN offset 1 is successive to SFN offset 0. Therefore, the UE determines that the SFN offsets have been received without errors. Since the P-BCH information  913  received at the P-BCH transmission times  921  and  923  includes the same reference SFN, the UE can combine the P-BCH information  913 . 
     In the case where an SFN offset received at the current P-BCH transmission time is one SFN offset period away from an SFN offset of the previous P-BCH transmission time, for example, when previous and current 2-bit SFN offsets are 3 and 0, respectively, P-BCH information received at the two P-BCH transmission times cannot be combined. Then, the UE clears its buffer and performs a CRC check on the P-BCH information received at the current P-BCH transmission time without combining. If the CRC check is bad, i.e. turns up errors, the UE stores the P-BCH information in the buffer and can correct the error in the P-BCH information using next-received P-BCH information. 
     If the SFN offsets received at the P-BCH transmission times  921  and  923  are not successive, the UE cannot determine whether the received P-BCH information is within the same SFN offset period. In this case, the UE performs a CRC check on the P-BCH information received at the P-BCH transmission time  923 . If the CRC check is bad, the UE combines the P-BCH information with the P-BCH information received at the P-BCH transmission time  921  and then checks a CRC in the combined P-BCH information. It can be further contemplated that the P-BCH information received at the P-BCH transmission times  921  and  923  are first combined and then CRC-checked, and if the CRC check is bad, the P-BCH information received at the P-BCH transmission time  923  is separately CRC-checked. It can also be further contemplated that the P-BCH information received at the P-BCH transmission times  921  and  923  are combined unconditionally. 
     If the UE cannot decide as to the continuity of the SFN offsets at any of the P-BCH transmission times  921 ,  923  and  925 , the UE combines P-BCH information received at the next P-BCH transmission time  925  with the P-BCH information received at the P-BCH transmission times  921  and  923  in all possible cases and performs a CRC check on the combined P-BCH information. For example, the UE combines the P-BCH information received at the next P-BCH transmission time  925  with the P-BCH information received at the P-BCH transmission time  921 , combines the P-BCH information received at the next P-BCH transmission time  925  with the P-BCH information received at the P-BCH transmission time  923 , and performs a CRC check on the combined information in every possible case. 
     If the P-BCH signal has been successfully received by combining at the P-BCH transmission time  923 , the UE obtains the actual SFN, SFN # 1000  for the P-NCH transmission time  921  by adding the reference SFN, SFN # 1000 , included in the P-BCH signal to SFN offset 0 for the P-BCH transmission time  921  and obtains the actual SFN, SFN # 1001 , for the P-NCH transmission time  923  by adding the reference SFN, SFN # 1000 , to SFN offset 1 for the P-BCH transmission time  923 . 
     The UE can detect and correct reception errors by checking the continuity of N (N&gt;=2) received SFN offsets. For example, for N=2, if SFN offsets 0 and 1 are received at the P-BCH transmission times  921  and  923 , respectively, the UE determines that the SFN information has been successfully received because SFN offsets 0 and 1 are successive. In the same manner, for N=3, if SFN offsets 0, 2 and 2 are received at the P-BCH transmission times  921 ,  923  and  925 , respectively, the UE determines that SFN offset 2 received at the P-BCH transmission time  923  is wrong and corrects this SFN offset to 1 using the previous and next SFN offsets. 
     While not shown, the UE can combine P-BCH information over every possible case (blind combining) and detect SFN offsets according to the combining results. For example, if a 1-bit SFN offset is used and the UE cannot decide as to the continuity of SFN offsets, the UE performs blind combining. If a CRC error is not detected from a certain combining case, the SFN offsets of two successive pieces of P-BCH information in the successful combining case are 0 and 1, sequentially. That is, if SFN offsets are represented in one bit, the P-BCH information received at the P-BCH transmission times  921 ,  923  and  925  is combined in every possible case. If no CRC error is found in the combination of the P-BCH information received at the P-BCH transmission times  923  and  925 , the SFN offsets of the P-BCH transmission times  923  and  925  are 0 and 1, sequentially. 
       FIG. 10  is a flowchart of an operation of the ENB according to the second exemplary embodiment of the present invention. 
     Referring to  FIG. 10 , when determining to transmit P-BCH information and an SFN offset in step  1001 , the ENB sets the SFN offset in step  1011 . For example, if the SFN offset is represented in two bits, the ENB can set the SFN offset mapped to an actual SFN by (SFN mod 4). In step  1013 , the ENB determines whether the SFN offset is within one SFN offset period. For example, if an SFN offset is 2 bits and set to be one of 0, 1, 2, 3, and 0, an SFN offset set to the second 0 is outside one SFN offset period. That is, one SFN offset period is a period for which SFN offsets are set to 0, 1, 2 and 3, sequentially. 
     If the SFN offset is within one SFN offset period in step  1013 , the ENB still uses a reference SFN included in P-BCH information transmitted at the previous P-BCH transmission time in step  1021 . The reference SFN is set to a value resulting from subtracting the SFN offset from an actual SFN. If the SFN offset is outside one SFN offset period in step  1013 , the ENB updates in step  1023  the reference SFN to be included in a P-BCH signal and in step  1025  encodes the P-BCH and the SFN offset in predetermined coding methods. Herein, transmit power or an MCS level is controlled for P-BCH information including the reference SFN corresponding to the SFN offset within one SFN offset period, under the assumption that the UE combines the P-BCH information. For example, the ENB uses a low transmit power level or an MCS level with a high coding rate for the P-BCH information. In step  1027 , the ENB transmits the P-BCH information and the SFN offset in predetermined respective resources. 
       FIG. 11  is a block diagram of an ENB apparatus according to the second exemplary embodiment of the present invention. 
     Referring to  FIG. 11 , the ENB apparatus has the same configuration as that illustrated in  FIG. 6  according to the first exemplary embodiment of the present invention, except for an SFN offset manager  1101 . The SFN offset manager  1101  sets and manages SFN offsets. The SFN offsets are set to {SFN mod 2 (number of bits allocated to SFN offset) }. A controller  1111  updates a reference SFN included in P-BCH information from a P-BCH information manager  1103  according to an SFN offset set by the SFN offset manager  1101 , when needed. A coder  1121  encodes the SFN offset and P-BCH information in predetermined coding methods/coding rates. 
       FIGS. 12A and 12B  are a flowchart of an operation of the UE according to the second exemplary embodiment of the present invention. 
     Referring to  FIGS. 12A and 12B , when determining that P-BCH information needs to be received in step  1201 , the UE determines in step  1211  whether SFN information of a serving cell has already been acquired. If the SFN information has not been acquired, the UE in step  1241  receives an SFN offset and P-BCH information in predetermined respective resources using predetermined respective coding methods/coding rates. In step  1243 , the UE checks whether the P-BCH information has a CRC error. If the P-BCH information has been successfully received without the CRC error, the UE receives in step  1251 N SFN offsets (N&gt;=1) in next P-BCH transmission periods, and in step  1253  detects and corrects SFN offset reception errors by checking the continuity of the received SFN offsets. For example, for N=1, if the SFN offset received in step  1241  is 0 and the SFN offset received in step  1251  is 1, the UE determines that the SFN offset information has been successfully acquired because the SFN offsets are successive. For N=2, if the SFN offset received in step  1241  is 0 and the SFN offsets received in step  1251  are 3 and 2, the UE determines that SFN offset 3 is wrong and corrects this SFN offset to 1. 
     In step  1255 , the UE checks the continuity of the SFN offsets corrected in step  1253  and determines whether the SFN offset information has been successfully acquired. If the SFN offsets are successive, the UE goes to step  1259 , considering that the SFN offset information has been successfully acquired in step  1255 . If in step  1255  it is determined that the SFN offset information acquisition failed, the UE returns to step  1251  and repeats  1251  to  1255 . 
     In step  1257 , the UE generates actual SFNs by combining a reference SFN included in the P-BCH information with the respective SFN offsets in step  1257  and in step  1259  applies the actual SFNs, considering that acquisition of SFN information of the cell has been completed. 
     If in step  1243  it is determined that a CRC error has occurred in the P-BCH information, in step  1261  the UE receives a new SFN offset and P-BCH information in the next transmission period. In step  1263 , the UE detects reception errors by checking the continuity of SFN offsets including the new SFN offset and if a reception error is detected, the UE corrects it. The UE determines whether the SFN offset received in step  1261  and corrected in step  1263  is within the same SFN offset period as an SFN offset received in the previous P-BCH transmission period in step  1265 . In step  1267 , the UE determines whether the received or corrected SFN offsets are successive in step  1267 . If the SFN offsets are not successive, the UE combines P-BCH information for every possible case (blind combining) in step  1281 . Every possible combing case may include the case of no combining. If the SFN offsets are successive in step  1267 , the UE in step  1271  determines whether the successive SFN offsets are within the same SFN offset period. If they are within the same SFN offset period, the UE in step  1273  combines the P-BCH information received in step  1261  with at least one piece of previously received P-BCH information. If the SFN offsets are within the same SFN offset period in step  1271 , the UE in step  1275  clears the buffer without combining. After step  1281 ,  1273 , or  1275 , the UE returns to step  1243 . 
     If the UE has already acquired the SFN information of the cell in step  1211 , the UE in step  1221  receives P-BCH information in predetermined resources using a predetermined coding method and determines in step  1223  whether the P-BCH information has been successfully received without a CRC error. If a CRC has occurred and the P-BCH information reception failed, the UE combines in step  1233  the P-BCH information with at least one piece of next P-BCH information whose SFN offsets are within the same SFN offset period. If the UE receives P-BCH information whose SFN offset does not fall within the same SFN offset period, in step  1235  the UE clears the buffer without combining the P-BCH information. After step  1235 , the UE returns to step  1223 . 
       FIG. 13  is a block diagram of a UE apparatus according to the second exemplary embodiment of the present invention. 
     Referring to  FIG. 13 , the UE apparatus has the same configuration as that illustrated in  FIG. 8  according to the first exemplary embodiment of the present invention, except for an SFN offset manager  1341 . A receiver  1311  receives P-BCH information and an SFN offset from a cell. A controller  1321  controls a decoder  1331  to decode the SFN offset and the P-BCH information in predetermined respective decoding methods. The decoded SFN offset and the decoded P-BCH information are provided to the SFN offset manager  1241  and a P-BCH manager  1343 , respectively. The SFN offset manager  1341  checks the continuity of decoded SFN offsets and according to the result. The SFN offset manager  1341  can additionally receive SFN offsets at next transmission times through the controller  1321 . If the P-BCH information reception failed, the P-BCH manager  1343  stores the received P-BCH information in a buffer  1345  and combines the stored P-BCH information with at least one piece of P-BCH information within the same SFN offset period, received through the SFN offset manager  1341  and the controller  1321 . An SFN offset can be transmitted on a physical channel after repetition. The repetition is considered as a kind of coding. In  FIG. 13 , for the sake of convenience, it is assumed that the decoder  1331  also interprets the SFN offset which was repeated. 
     As is apparent from the above description, the present invention advantageously enables more P-BCH information bits in a given bandwidth in a cell. 
     While the invention has been shown and described with reference to certain exemplary embodiments of the present invention 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 present invention as defined by the appended claims and their equivalents.