Abstract:
A physical channel transmission method and a transmission chain therefor in a communication system are disclosed. In transmitting packet data or packet control data through a physical channel having a transmission format of variable lengths, the data transmission chain includes a scrambler for scrambling the packet data or packet control data using the transmission format information.

Description:
CROSS REFERENCE TO RELATED ART  
         [0001]    This application claims the benefit of the Korean Application Nos. P2002-05389 filed on Jan. 30, 2002, and P2002-10700 filed on Feb. 21, 2002, which is hereby incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates generally to a wireless communication system, and more particularly, to a data transmission method through a physical channel and a transmission chain therefor.  
           [0004]    2. Discussion of the Related Art  
           [0005]    In a certain wire/wireless communication system, a transmitter transmits one among various types of transmission formats over a specified physical channel. Nevertheless, if it is required for a receiver to receive the data over the channel without any information on the transmission format, the receiving end performs a blind format detection. As an example of such a system, there is the 1x-EVDV system  
           [0006]    In the 1x-EVDV system, at least one of a plurality of forward packet data control channels (F-PDCCHs) may be used to transmit control information of a forward packet data channel (F-PDCH) that is a physical channel for transmitting packet data.  
           [0007]    Specifically, for the packet data transmission, the conventional wireless communication systems use a physical channel, such as a packet data channel (PDCH), a packet data control channel (PDCCH), etc.  
           [0008]    The PDCH is a channel that is used to transmit packet data to a corresponding terminal (or a user, hereinafter referred to as terminal).  
           [0009]    The PDCCH contains control information for enabling the corresponding terminal to receive, without error, the packet data being transmitted through the PDCH.  
           [0010]    The PDCCH is a forward channel that includes the control information on the PDCH. The receiver extracts the control information from the PDCCH, and decodes the PDCH using the control information.  
           [0011]    Generally, the PDCCH is composed of various kinds of information required for decoding of 13˜21 bits, cyclic redundancy checking (CRC) bits of 6˜8 bits for checking existence/nonexistence of a receiving error of the information, and convolutional encoder tail bits of 8 bits.  
           [0012]    The whole information of 27˜37 bits as constructed above is produced as coded bits of 54˜64 bits (in case of ½-coding) or coded bits of 108˜128 bits (in case of ¼-coding) by a convolutional encoder having a ½ or ¼ code rate.  
           [0013]    Hereinafter, a conventional method of puncturing the coded bits will be explained with reference to the following drawings.  
           [0014]    [0014]FIG. 1 is a block diagram of a transmission chain of a general F-PDCCH.  
           [0015]    The data (i.e., input sequence) transmitted through a general F-PDCCH is combined with an error detection code, such as a CRC code, through an error detection code addition block  101  which consists of a single CRC generator.  
           [0016]    Generally, a medium access control (MAC) identifier (MAC_ID) is the control information included in a service data unit (SDU) transferred from a MAC layer, and indicates an identifier of the terminal to which the corresponding SDU is to be transmitted. The error detection code addition block  101  generates an error detection code.  
           [0017]    Tail bits for sending the final state of the encoder as a trellis termination state are added to the bits having the CRC code in a tail bit addition block  102 .  
           [0018]    The bits to which the tail bits are added is encoded using a convolutional code in an encoder  103 .  
           [0019]    Through the above-described process, the generated coded bits are repeated through a symbol repetition block  104  to match the length of a transmission slot, and the repeated bits are punctured in a puncturing block  105 .  
           [0020]    For instance, since the number of usable Walsh codes is limited in the 1x-EVDV system, a Walsh code having a length of 64 chips is used for the PDCCH. Thus, the number of coded bits included in one slot is 48.  
           [0021]    The slot length used to transmit the PDCCH is classified into one slot, two slots, and four slots. For example, the 48 coded bits are included in one slot, 96 coded bits are included in two slots, and 192 coded bits are included in four slots.  
           [0022]    For instance, as shown in FIG. 1, if 8-bit CRC bits and 8-bit encoder tail bits are added to the 18-bit information bits, and a channel code having a ½ code rate is used for the transmission of one slot, 68 coded bits are generated. Then, the generated coded bits are punctured through the puncturing block  105  to match the length of the transmission slot.  
           [0023]    Since one slot is for transmitting 48 coded bits, the puncturing of  20  (i.e., 68−48=20) bits is performed, and then 48 coded bits are transmitted through the one slot.  
           [0024]    At this time, if the same amount of information is transmitted through four slots, the corresponding information bits, as shown in FIG. 1, are generated as 136 coded bits through an encoder having a ¼ code rate, and then generated as 272 bits through a symbol repetition block. Since these 272 bits should be transmitted through four slots, i.e., 192 bits,  80  (=272−192) bits are punctured. These 192 bits are transmitted, being equally divided into four slots.  
           [0025]    The punctured bits are interleaved through a block interleaver  106 , and then modulated by a modulator  107  in accordance with a QPSK method. The modulated signal is divided into an I-channel signal and a Q-channel signal using a portion of Walsh codes.  
           [0026]    As described above, the transmission length of the F-PDCCH may be one slot, two slots, or four slots. Here, the slot means a time unit of 1.25 msec. At this time, the transmitter does not inform the length of the F-PDCCH currently being transmitted to the receiver. In other words, the receiver does not accurately know what format is being received. Accordingly, the receiver performs the decoding process with respect to three formats (i.e., three lengths of one slot, two slots, and four slots) and checks the CRC to detect what is the transmission length (or format) of the received F-PDCCH.  
           [0027]    As described above, in case that the receiver determines the format of the transmission channel only using the CRC, a case that the CRC has the same value of ‘1’ (which corresponds to the case that an accurate transmission format is detected) may occur with respect to two or more kinds of formats. In this case, the receiver cannot accurately determine what kind of transmission format is transmitted through the channel. Accordingly, an additional device for minimizing the occurrence of such a case is required.  
         SUMMARY OF THE INVENTION  
         [0028]    Accordingly, the present invention is directed to a data transmission method through a physical channel and a transmission chain therefor that substantially obviates one or more problems due to limitations and disadvantages of the related art.  
           [0029]    An object of the present invention is to provide a data transmission method and a transmission chain therefor that enables a receiver to accurately determine a transmission format by scrambling according to transmission format information through a transmitter.  
           [0030]    Another object of the present invention is to provide a data transmitting method and a transmission chain therefor that can reduce the load of a receiver by descrambling.  
           [0031]    In another aspect of the present invention, a data transmitting/receiving method includes scrambling data to be transmitted using the length of the transmission format on a physical channel having the transmission format of the variable length, transmitting the scrambled data to a receiving end, and descrambling the transmitted data without detecting the information on the transmission format from the received data, wherein the scrambling code at a time point of the scrambling is equal to the descrambling code at a time point of the descrambling after the predetermined number of slots.  
           [0032]    Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
           [0033]    To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a data transmission chain in transmitting certain data through a physical channel having a transmission format of a variable length, the data transmission chain comprises a scrambler for scrambling the certain data using a scrambling code including information on the transmission format.  
           [0034]    In another aspect of the present invention, A communication system comprises a transmitter including a scrambler for scrambling a signal to be transmitted using a mask code that includes information on a transmission format of a variable length on a physical channel having the transmission format of the variable length, and a receiver including a descrambler for descrambling a signal received from the transmitter using a specified mask code without detecting the information on the transmission format from the received signal, wherein an output when the scrambler operates is equal to that when the descrambler operates.  
           [0035]    In another aspect of the present invention, a data transmitting/receiving method includes scrambling data to be transmitted using a mask code that includes information on a transmission format of a variable length on a physical channel having the transmission format of the variable length, transmitting the scrambled data to a receiving end, and descrambling the transmitted data using a specified mask code without detecting the information on the transmission format from the received data, wherein the scrambling code at a time point of the scrambling is equal to the descrambling code at a time point of the descrambling after a predetermined number of slots.  
           [0036]    According to one embodiment of the present invention, a wireless communication method comprising the steps of scrambling in a scrambler the packet control data with a scrambling sequence, wherein the scrambling sequence is generated in response to a slot length; and transmitting the scrambled packet control data to a receiver. A descrambler of the receiver descrambles the packet control data using a common descrambling sequence that is independent of the slot length. Preferably, the scrambling sequence is generated in response to the slot length and a system time in slot units. Also, the scrambling sequence may be generated in response to different long code masks based on the slot length. Preferably, the slot length comprises one of one, two and four slots.  
           [0037]    According to one aspect of the present invention, the method further comprises the steps of adding an error detection code to the packet control data; adding tail bits to the packet control data having the error detection code; encoding the packet control data with the tail bits added thereto; performing at least one of symbol repetition and puncturing the coded packet control data to match a length of a transmission slot; interleaving the symbol-repeated or punctured data; and modulating the interleaved data, wherein the step of scrambling is performed after any one of the above steps.  
           [0038]    According to another embodiment of the present invention, a communication channel capable of transferring packet control data having variable slot lengths, comprising the steps of: receiving a scrambled packet control data, wherein the packet control data is scrambled with a scrambling sequence that is generated in response to a slot length; and descrambling the scrambled packet control data by using a descrambling sequence. Preferably, the scrambling sequence is generated based on the slot length and a transmission time. The descrambling sequence is generated based on a receiving time.  
           [0039]    According to another embodiment of the present invention, a wireless communication system comprises a scrambler for scrambling the packet control data with a scrambling sequence, wherein the scrambling sequence is generated in response to a slot length; and a transmitter portion for transmitting the scrambled packet control data to a receiver. The system further comprises a descrambler for descrambling the packet control data using a common descrambling sequence that is independent of the slot length.  
           [0040]    According to an embodiment of the present invention, a wireless communication method using communication channels capable of transferring packet control data having variable slot lengths, comprises the steps of: scrambling the packet control data with at least one of a plurality of long code masks in a transmitting device, wherein the packet control data having different slot lengths and being substantially parallely transmitted are scrambled with scrambling codes generated using different code masks; communicating the scrambled packet control data to a receiving device; and descrambling the packet control data in the receiving device using a common long code mask that is used to generate descramble codes corresponding to the plurality of code masks used in the transmitting device.  
           [0041]    According to one aspect of the invention, in the transmitting device a first packet control data having a first slot length is scrambled with a first code mask and a second packet control data having a second slot length is scrambled with a second code mask. Preferably, in the receiving device the first and the second packet control data are descrambled using the common code mask that is used to generate the first and the second code masks in response to a difference in transmission and reception time.  
           [0042]    According to another aspect of the invention, the wireless communication method further comprising the steps of: adding an error detection code to the packet control data; adding tail bits to the packet control data to which the error detection code is added; encoding the packet control data to which the tail bits are added; performing a symbol repetition and/or puncturing the coded packet control data to match a length of a transmission slot; interleaving the symbol-repeated and/or punctured data; and modulating the interleaved data, wherein the step of scrambling is performed after any one of the above steps. The step of adding the error detection code comprises the steps of: adding a first error detection code to the packet control data using a medium access control identifier (MAC ID) provided as an identifier of the receiving end to which the packet control data is to be transmitted; and generating a second error detection code using the packet control data to which the first error detection code is added, wherein the packet control data to which the first error detection code is added is scrambled.  
           [0043]    According to another aspect of the invention, the plurality of code mask is determined so that a scrambling code mask at a time point when the packet control data is scrambled is equal to a descrambling code used at a time point when the receiving end descrambles the transmitted packet control data. With respect to a slot length N for transmitting the packet control data and a predetermined constant Δ, a descrambling code generated from the common code mask comprises the code after N+Δ from a time point when the data is scrambled.  
           [0044]    According to another aspect of the invention, the information used generated the scrambling code and descrambling code includes at least one of a system time and the number of slots. According to another embodiment, a wireless communication system using communication channels capable of transferring packet control data having variable slot lengths, comprises: a scrambler comprising a system timer, a calculator connected to the system timer, wherein the calculator calculates a value using the system timer output and/or the number of slots, wherein the scrambler generates the scrambler code using the value  
           [0045]    According to another embodiment, a wireless communication system using communication channels capable of transferring packet control data having variable slot lengths, comprises: a scrambler comprising a long code generator operable in response to a plurality of code masks to generate long codes; a bit extractor operably connected to the long code generator; a first shift register operably connected to the bit extractor; a switch operably connected to the first shift register to control an output signal of the first shift register; a second shift register operably connected to the switch, wherein the scramber scrambles the packet control data using at least one of the plurality of code masks in a transmitting device, wherein the packet control data having different slot lengths and being substantially parallely transmitted are scrambled with scrambling codes generated using different code masks.  
           [0046]    According to another embodiment, a mobile terminal uses the scrambling technique described herein. The mobile terminal is for use with a wireless transmission system using communication channels capable of transferring packet control data having variable slot lengths, the communication system comprising a scrambler for scrambling the packet data with at least one of the plurality of code masks, wherein the packet control data having different slot lengths and being substantially parallely transmitted are scrambled with scrambling codes generated using different code masks. The mobile terminal comprises a descramber that descrambles the scrambed packet data using a common code mask that is used to generate the plurality of code masks used in the transmission system.  
           [0047]    It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0048]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:  
         [0049]    [0049]FIG. 1 is a block diagram of a transmission chain of a general F-PDCCH;  
         [0050]    [0050]FIG. 2 is a block diagram of a transmission chain of an F-PDCCH according to an embodiment of the present invention;  
         [0051]    [0051]FIG. 3 illustrates the construction of a first embodiment of a scrambler illustrated in FIG. 2;  
         [0052]    [0052]FIG. 4 illustrates a scrambling format insertion state for a long code according to an embodiment of the present invention;  
         [0053]    [0053]FIG. 5 illustrates the construction of a second embodiment of a scrambler illustrated in FIG. 2;  
         [0054]    [0054]FIG. 6 is a block diagram of a transmission chain of an F-PDCCH according to a second embodiment of the present invention;  
         [0055]    [0055]FIG. 7 is a block diagram of a scrambler illustrated in FIG. 6;  
         [0056]    [0056]FIG. 8 illustrates the construction of a descrambler for descrambling the scrambler illustrated in FIG. 6;  
         [0057]    [0057]FIG. 9 illustrates the operation of a mask according to the present invention; and  
         [0058]    [0058]FIGS. 10A to  10 D illustrate scrambling and descrambling of a transmitting end and a receiving end according to a second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0059]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0060]    [0060]FIG. 2 is a block diagram of a transmission chain of an F-PDCCH according to an embodiment of the present invention.  
         [0061]    In particular, FIG. 2 shows the transmission chain of the F-PDCCH used for transmission of control information of an F-PDCH that is a physical channel for transmitting packet data (such as packet control data) in, for example, the 1x-EVDV system.  
         [0062]    It is assumed that the system uses two F-PDCCHs, and they are called F-PDCCH( 0 ) and F-PDCCH( 1 ). Also, it is assumed that the transmission formats of each F-PDCCH(i) are classified into N in accordance with the transmission lengths of one slot, two slots, and four slots. The formats are preferably called FM(i,N). For example, in FM(i,N), i=0,1 represents F-PDCCH( 0 ) and F-PDCCH( 1 ), respectively, and N=1,2,4 represents one slot, two slots, and four slots, respectively.  
         [0063]    The above description is for illustrating the preferred embodiment of the present invention, and may also be applicable to other systems that have different number of channels or formats.  
         [0064]    The construction of the F-PDCCH transmission chain is illustrated in FIG. 2. A scrambler  110  for enabling the receiver to perform a blind format detection with respect to the F-PDCCH without error is additionally provided, and is driven by applying the type of channel and the transmission format information according to a predetermined rule. By specifying the transmission format information as shown in Table 1, the receiver can accurately detect the transmission format with its load reduced.  
         [0065]    The scrambler  110  is a device that relatively randomly or pursuant to specific rule generates ‘0’ and ‘1’. The scrambler  110  may be placed at any one of the following locations: P 1 , P 2 , P 3 , P 4 , P 5 , P 6 , P 7 , and P 8 .  
         [0066]    [0066]FIG. 2 shows the case that the scrambler  110  is added to a location designated as P 7 .  
         [0067]    In FIG. 2, Mask(i,N) is a sequence that is in a one-to-one corresponding relation with FM(i,N), and serves to generate the scrambler  110  output differently in accordance with the kind of channel and/or the transmission format.  
         [0068]    [0068]FIG. 3 illustrates the construction of a first embodiment of a scrambler illustrated in FIG. 2. FIG. 4 illustrates an example of a mask insertion with respect to transmission format information in a long code mask in case of using the scrambler illustrated in FIG. 2.  
         [0069]    In FIG. 3, in order to implement the scrambler  110  illustrated in FIG. 2, a long code generator used in the existing code division multiple access (CDMA) system may be employed.  
         [0070]    The long code generator  109   a  as shown in FIG. 3 generates the bits outputted with a high-speed chip rate, and a scrambling bit extractor  109   b  extracts necessary bits from the bits outputted at a high speed from the long code generator  109   a . A scrambling bit repetition section  109 C is optionally added, and repeats the output of the scrambling bit extractor  109   b  as needed. A srambling code application section  111  applies the scrambling code to information bits.  
         [0071]    At this time, Mask(i,N) may be in the one-to-one corresponding relation with FM(i,N), and has the same operation principle as the existing long code mask.  
         [0072]    [0072]FIG. 4 shows an example of Mask(i,N) when the degree of a polynomial that prescribes the characteristic of the long code generator  109   a  illustrated in FIG. 3 is  42 . In Mask(i,N), the field  0 , field  1 , field  3 , and field  4  are fixed to specified numerals that are distinguishable from other channels used in the system. The field  2  is predetermined value according to FM(i,N).  
         [0073]    In Table 1, several examples of the long code mask to be inserted into field  2  of FIG. 4 according to the kind of transmission format are presented.  
                                                                             TABLE 1                                   FM(0,1)   FM(0,2)   FM(0,4)   FM(1,1)   FM(1,2)   FM(1,4)                                    L2 L1 L0   000   001   010   100   101   110   first example           000   001   010   011   100   101   second example           000   001   010   000   001   010   third example           001   010   100   001   010   100   4th example                  
 
         [0074]    [0074]FIG. 5 is a view illustrating the construction of a second embodiment of the scrambler illustrated in FIG. 2.  
         [0075]    In order to implement the scrambler illustrated in FIG. 2, a shift register may be employed. Specifically, FIG. 5 shows the embodiment in that the polynomial that prescribes the characteristic of the long code generator is h(D)=D 17 +D 14 +1. In this case, Mask(i,N) may be in the one-to-one corresponding relation with FM(i,N). Using this value, the memory value of the shift register is initialized.  
         [0076]    One example of Mask(i,N) related to FIG. 5 can be represented by 
         Mask(i,N)=( 1   1   1   1   1   1   1   1   1   1   1   1   1   1  L 2  L 1  L 0 )  [Eq.1] 
         [0077]    Here, as an example of the values of (L 2  L 1  L 0 ) in the equation 1, values in Table 1 may be used.  
         [0078]    As another example of Mask(i,N), time information can be added to Mask(i,N) as follows. 
         Mask(i,N)=( 1   1   1   1   1   1   1   1   1   1   1   1  T 1  T 0  L 2  L 1  L 0 )  [Eq.2] 
         [0079]    Here, as an example of the values of (L 2  L 1  L 0 ) in the equation 2, the values in Table 1 may be used. Also, (T 1  T 0 ) in the equation 2 is a sequence according to the present transmission time or system time in slot unit. As an example, it is assumed that the transmission timing of the present transmission slot is Slot(t), and the value of Slot(t) is one among { 0 ,  1 ,  2 , . . .  14 ,  15 }.  
         [0080]    At this time, if it is determined that Val=(Slot(t) %  4 ), Val has one value among { 0 ,  1 ,  2 ,  3 }, and the relationship between T 1 , T 0  and Val can be defined as in Table 2.  
                                       TABLE 2                                       Val   0   1   2   3           T1 T0   00   01   10   11                      
 
         [0081]    [0081]FIG. 6 is a block diagram of a transmission chain of an F-PDCCH according to a second embodiment of the present invention. FIG. 7 is a block diagram of a scrambler illustrated in FIG. 6. FIG. 8 illustrates the construction of a descrambler for descrambling the data scrambled by the scrambler illustrated in FIG. 6.  
         [0082]    In the same manner as the first embodiment, without increasing the hardware complexity, the present invention is additionally provided with a scrambler  110   a  for the effective transmission/reception of the F-PDCCH, and drives the scrambler  110   a  based on the specified rule to be explained hereinafter.  
         [0083]    The proposed specified rule is related to the generation of output bits of the scrambler  110   a  in consideration of the transmission/reception time difference of the F-PDCCH between the transmitter (for example, a base station) and the receiver (for example, a mobile station) in accordance with FM(i,N) of the F-PDCCH currently being transmitted/received.  
         [0084]    [0084]FIG. 7 shows an example of the scrambler illustrated in FIG. 6 from the viewpoint of the transmitter in the base station (BS).  
         [0085]    As described above, a long code generator  201   a  generates the output bits with a high-speed chip rate (i.e., 1228800 output symbols per sec).  
         [0086]    A scrambling bit extractor  202   a  extracts with a desired rate the bits outputted at a high speed from the long code generator  201   a , for example, at a speed of 19.2 kbps.  
         [0087]    Mask(i,N), that is the long code mask in this example, is in a one-to-one corresponding relation with FM(i,N), and operates in the same manner as the existing long code mask. A switch  204   a  between Z 4  and Z 5  is used to copy an output of a 21-bit shift register A  203   a  into a 21-bit shift register B  205   a  at a specified time point predetermined between the BS and the MS (mobile station) in one slot. Also, the 21-bit shift register B  205   a  generates its output only during the scrambling operation, and a first scrambling code application section  206   a  performs an XOR operation with respect to an output of the register B  205   a  and data bits processed from an input sequence, for example, a 21-bt output of a first CRC generator (i.e., inner CRC)  100 .  
         [0088]    Preferably, the scrambling sequence generated using information pertaining to system time and/or number of slots. Mask(i,N) is related to system time and/or number of slots The system time is preferably the system time in 1.25 MS slots. The scrambler sequence is preferably equal to a predetermined (for example 13) least significant bits of the system time+number of slots, where the system time is in units of the first slot of the packet data control channel transmission.  
         [0089]    [0089]FIG. 8 illustrates the construction of a descrambler from the viewpoint of the receiver in the MS when used in conjunction with the scrambler shown in FIGS. 6 and 7.  
         [0090]    In FIG. 8, the operations of the respective parts coincide with those of FIG. 7. However, the used long code mask is not Mask(i,N), but is CommonMask(i) as described above. On the other hands, a second scrambling code application section  206   b  performs an XOR operation with respect to an output of the register B  205   b  and data bits processed from a receiving sequence, wherein the data bits vary dependent on a position of a scrambler  110  in the transmitter of the base station (BS).  
         [0091]    As described above, Mask(i,N) in FIG. 7 and CommonMask(i) in FIG. 8 are designed to be mutually related to each other, and at this time, it is assumed that the output of the long code generators  201   a  and  201   b  used in the BS and the MS are synchronized in time with each other.  
         [0092]    [0092]FIG. 9 illustrates an examplary relationship between the scrambler and the descrambler illustrated in FIGS. 7 and 8. When the system is initially designed, Mask(i,N) is determined using CommonMask(i) and the slot length information N.  
         [0093]    Preferably, CommonMask(i) is defined not to overlap other long code masks used by other transmission channels of the designed system. At this time, CommonMask(i) may have the different value or the same value according to the value of i. Herein , the i means a priority order of the transmission channel  
         [0094]    In case that the BS uses Mask(i,N) as the long code mask, Mask(i,N) is designed so as to make the output of the second register (at this time, it is assumed that the receiver uses CommonMask(i)) to be generated after a (N+Δ) slot time from the present time point be generated at the present time point.  
         [0095]    Preferably, if the transmitter in the BS uses Mask(i,N) as the long code mask designed as described above, the receiver in MS can perform the descrambling using CommonMask(i) after the (N+Δ) slot time. At this time, α is a certain fixed constant which takes into consideration the hardware related delay. For example, the Δ is one of 0,0.5 and 1.  
         [0096]    In other words, the scrambler in the transmitter is designed by alleviating the processing complexity at the descrambler in mobile station.  
         [0097]    As described above, the present invention can be applied irrespective of the number of input bits of the F-PDCCH for scrambling.  
         [0098]    [0098]FIGS. 10A to  10 D illustrate scrambling and descrambling of the transmitter and the receiver according to an embodiment of the present invention.  
         [0099]    In FIG. 10A, it is assumed that no transmission delay occurs between thetransmitter and receiver.  
         [0100]    Referring to FIG. 10A, a scrambler(x) means an 21-bit output of a second register  205   a  used by the BS to scramble a 21-bit output of the first CRC generator (i.e., inner CRC)  100  at the corresponding time point.  
         [0101]    In the same manner, a descrambler(x′) means a 21-bit output of a second register  205   b  used by the MS to descramble at the corresponding time point. Herein, the output bits of the scrambler(x) may be varied by the position of the scrambler on the transmission chain  
         [0102]    For instance, the output bits of the second register  205   a  used by the BS to transmit (a), (b), and (c) F-PDCCHs at the start point of the slot  2  are the scrambler( 1 ). Also, the output bits of the second register  205   b  used by the MS to descramble the F-PDCCH indicated as (a) are the descrambler( 2 ′).  
         [0103]    As described above, if the BS and the MS drive the scrambler and the descrambler according to the same operational principle, in other words, if it is determined that scrambler(x)=descrambler(x′), the output bits of the second registers  205   a  and  205   b  used to scramble and descramble the same F-PDCCH are different from each other. As a result, a receiver (such as a mobile terminal) cannot descramble the packet data.  
         [0104]    For example, the output bits of the second register  205   a  used by the BS to scramble the F-PDCCH indicated as (a) are the scrambler( 1 ), and the output bits of the second register  205   b  used by the MS to descramble the F-PDCCH indicated as (a) are the descrambler( 2 ′). If the BS and the MS drive the scrambler and the descrambler according to the rule which is scrambler(x)=descrambler(x′) Generally , the relation of scrambler( 1 )=descrambler( 2 ′) is not established. So the descrambling of MS is not operated correctly.  
         [0105]    At this time, the effects achieved by the present invention are as follows.  
         [0106]    The scrambler/descrambler of the BS and the MS are driven according to the different rules, and the output bits of the second registers  205   a  and  205   b  used during the scrambling and the descrambling of the same F-PDCCH become the same.  
         [0107]    As one method for this, they may be driven so that the output of the second register  205   a  of the BS becomes different according to FM(i,N) of the F-PDCCH to be currently transmitted.  
         [0108]    This method will be explained with reference to FIG. 10A.  
         [0109]    In case that the BS transmits the F-PDCCH indicated as (a), it drives its own scrambler so that the scrambler( 1 ) has the same output value as the descrambler( 2 ′).  
         [0110]    In case that the BS transmits the F-PDCCH indicated as (b), it drives its own scrambler so that the scrambler( 1 ) has the same output value as the descrambler( 3 ′).  
         [0111]    In case that the BS transmits the F-PDCCH indicated as (c), it drives its own scrambler so that the scrambler( 1 ) has the same output value as the descrambler( 5 ′).  
         [0112]    [0112]FIG. 10B exemplifies the case that a switch  204   a  between Z 4  and Z 5  of the BS is used to copy the output of the 21-bit shift register  203   a  into the 21-bit shift register  205   a  at a center time point in one slot. For purpose of illustration, it is assumed that Δ is ‘0’, and no transmission delay occurs between the BS and the MS.  
         [0113]    First, if the BS transmits the F-PDCCH having a transmission length of one, two, or four slots in the slot 2  region to the MS, the one or more slots are scrambled using the output of the shift register B  205   a  of the t 1  time period.  
         [0114]    In the same manner, if the BS transmits the F-PDCCH having a transmission length of one, two, or four slots in the slot 5  region to the MS, the one or more slots are scrambled using the output of the shift register B  205   a  of the t 7  time period. The long code mask used at this time is Mask(i,N).  
         [0115]    The MS uses the same output of the shift register B  205   a  of the t 3  time period to descramble the F-PDCCH having a length of one slot received in the time period of the slot 2 .  
         [0116]    Also, the MS uses the same output of the shift register B  205   a  of the t 5  time period to descramble the F-PDCCH having a length of two slots received in the time period of the slot 2  and the slot 3 .  
         [0117]    Also, the MS uses the same output of the shift register B  205   a  of the t 9  time period to descramble the F-PDCCH having a length of four slots received in the time period of the slot 2  to the slot 5 .  
         [0118]    In the same manner, the MS uses the same output of the shift register B  205   a  of the t 7  time period to descramble the F-PDCCH having a length of one slot received in the time period of the slot 4 .  
         [0119]    That is, if the MS uses CommonMask(i) , the output of the second register  205   a  that the BS generates by Mask(i,N) at a specified time will be the output values of the second register  205   b  to be generated after an N-slot time from the specified time.  
         [0120]    As a result, in order to correctly descramble the received F-PDCCH after the N-slot time length, the MS can use CommonMask(i).  
         [0121]    That is, as shown in FIG. 10B, the F-PDCCH of a two-slot length, which the BS scrambled using the sequence of the shift register B  205   a  of the t 1  time period, is descrambled by the output of the shift register B  205   b  of the t 5  period that is after the two-slot time length.  
         [0122]    Table 3 shows an example of the long code masks composed of 42 bits for the system operating in the second embodiment of the present invention. At this time, it is assumed that CommonMask(i) has the same value with respect to all i.  
                   TABLE 3                       Long Code           Mask Types   MSB . . . LSB                   CommonMask(i)   110001100110110000000000000000000000000000       Mask(i,1)   001100110110110011100001001100000100101000       Mask(i,2)   000110000110101011000110000110011000100101       Mask(i,4)   010110010100111101111000011110110010000011                  
 
         [0123]    [0123]FIG. 10C exemplifies the case that the switch  204   a  between Z 4  and Z 5  of the BS is used to copy the output of the 21-bit shift register  203   a  into the 21-bit shift register  205   a  at a start time point of one slot. It is assumed that Δ=1, and no transmission delay occurs between the BS and the MS.  
         [0124]    First, if the BS transmits the F-PDCCH having a transmission length of one, two, or four slots at the start time point of the slot 2 , the one or more slots are scrambled using the output of the shift register B  205   a  of the t 1  time period.  
         [0125]    In the same manner, if the BS transmits the F-PDCCH having a transmission length of one, two, or four slots at the start time point of the slot 5 , the one or more slots are scrambled using the output of the shift register B  205   a  of the t 4  time period. The long code mask used at this time is Mask(i,N).  
         [0126]    The MS uses the output of the shift register B  205   b  of the t 3  time period to descramble the F-PDCCH having a length of one slot received in the time period of the slot 2 .  
         [0127]    Also, the MS uses the output of the shift register B  205   b  of the t 4  time period to descramble the F-PDCCH having a length of two slots received in the time period of the slot 2  and the slot 3 .  
         [0128]    Also, the MS uses the output of the shift register B  205   b  of the t 6  time period to descramble the F-PDCCH having a length of four slots received in the time period of the slot 2  to the slot 5 .  
         [0129]    In the same manner, the MS uses the output of the shift register B  205   b  of the t 3  time period to descramble the F-PDCCH having a length of one slot received in the time period of the slot 4 .  
         [0130]    That is, if the MS uses CommonMask(i), the output of the second register  205   a  that the BS generates by Mask(i,N) at a specified time will be the output values of the second register  205   b  to be generated after an (N+1)-slot time from the specified time.  
         [0131]    As a result, in order to descramble the received F-PDCCH after the N-slot time length, the MS may use CommonMask(i).  
         [0132]    For example, as shown in FIG. 10C, the F-PDCCH of a two-slot length, which the BS scrambled using the output of the shift register B  205   a  of the t 1  time period, is descrambled by the output of the shift register B  205   b  of the t 3  period that is after the three-slot time length.  
         [0133]    Table 4 shows another example of the long code masks composed of 42 bits for the system operating as in the second embodiment of the present invention. At this time, it is assumed that CommonMask(i) has the same value with respect to all i.  
                   TABLE 4                       Long Code           Mask Types   MSB . . . LSB                   CommonMask(i)   110001100110110000000000000000000000000000       Mask(i,1)   000110000110101011000110000110011000100101       Mask(i,2)   100000100011100001111111001011111111001110       Mask(i,4)   101000011111110010101001100101001111011010                  
 
         [0134]    In FIG. 10D, it is not necessarily required for the operational time points of the switch  204   a  and  204   b  between Z 4  and Z 5  of the BS and the MS to coincide with each other. FIG. 10D exemplifies the case that the switch  203   a  between Z 4  and Z 5  of the BS is used to copy the output of the 21-bit shift register A  203   a  into the 21-bit shift register  205   a  at a specified center time point within one slot, and the switch  204   b  between Z 4  and Z 5  of the MS is used to copy the output of the 21-bit shift register A  203   b  into the 21-bit shift register  205   b  at the start time point of one slot. It is assumed that Δ=0.5, and no transmission delay occurs between the BS and the MS.  
         [0135]    First, if the BS transmits the F-PDCCH having a transmission length of one, two, or four slots at the start time point of the slot 2 , the one or more slots are scrambled using the output of the shift register B  205   a  of the t 1  time period. In the same manner, if the BS transmits the F-PDCCH having a transmission length of one, two, or four slots at the start time point of the slot 5 , the one or more slots are scrambled using the output of the shift register B of the t 7  time period. The long code mask used at this time is Mask(i,N).  
         [0136]    The MS uses the output of the shift register B  205   b  of the t 4  time period to descramble the F-PDCCH having a length of one slot received in the time period of the slot 2 .  
         [0137]    Also, the MS uses the output of the shift register B  205   b  of the t 6  time period to descramble the F-PDCCH having a length of two slots received in the time period of the slot 2  and the slot 3 .  
         [0138]    Also, the MS uses the output of the shift register B  205   b  of the t 10  time period to descramble the F-PDCCH having a length of four slots received in the time period of the slot 2  to the slot 5 .  
         [0139]    Also, the MS uses the output of the shift register B  205   b  of the t 8  time period to descramble the F-PDCCH having a length of one slot received in the time period of the slot 4 .  
         [0140]    That is, if the MS uses CommonMask(i), the output of the second register  205   a  that the BS generates by Mask(i,N) at a specified time will be the output values of the second register  205   b  to be generated after an (N+0.5)-slot time from the specified time. As a result, in order to descramble the received F-PDCCH after the N-slot time length, the MS can use CommonMask(i).  
         [0141]    For example, as shown in FIG. 10D, the F-PDCCH of a two-slot length, which the BS scrambled using the output of the shift register B  205   a  of the t 1  time period, is descrambled by the output of the shift register B  205   b  of the t 6  period that is after the 2.5-slot time length.  
         [0142]    Table 5 shows another example of the long code masks composed of 42 bits for the system operating as in the second embodiment of the present invention. At this time, it is assumed that CommonMask(i) has the same value with respect to all i.  
                   TABLE 5                       Long Code           Mask Types   MSB . . . LSB                   CommonMask(i)   110001100110110000000000000000000000000000       Mask(i,1)   101011111011111010011010000110101010000100       Mask(i,2)   111011101100101101011101010101100001011111       Mask(i,4)   101001010000000100000001011011110110000010                  
 
         [0143]    As described above, according to the present invention, since the transmitting end scrambles the transmission format of a physical channel of a variable length and the receiving end accurately detects the transmission format, the waste of resources can be reduced, and thus the whole performance of the system can be improved.  
         [0144]    Also, if the scrambler/descrambler is designed according to the present invention, the time delay of the scrambler/descrambler between the transmitter and the receiver can be considered. Thus, it is not required for the receiving end (i.e., MS) to store the descrambling code for several slot lengths in order to compensate for the time delay, and thus the hardware complexity can be reduced.  
         [0145]    It will be apparent to one skilled in the art that the preferred embodiments of the present invention can be readily implemented using, for example, a suitably programmed digital signal processor (DSP) or other data processing device, either alone or in combination with external support logic. The preferred embodiments may be implemented as a method, apparatus or article of manufacture using standard programming and/or engineering techniques to produce software, firmware, hardware, or any combination thereof. The term “article of manufacture” as used herein refers to code or logic implemented in hardware logic (e.g., an integrated circuit chip, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC), etc.) or a computer readable medium, volatile and non-volatile memory devices (e.g., EEPROMs, ROMs, PROMs, RAMs, DRAMs, SRAMs, firmware, programmable logic, etc.). Code in the computer readable medium is accessed and executed by a processor. Of course, those skilled in the art will recognize that many modifications may be made to this configuration without departing from the scope of the present invention, and that the article of manufacture may comprise any information bearing medium known in the art.  
         [0146]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.