[Technical Field] The present invention relates to an apparatus and a method for generating a beacon signal for handoff in a CDMA (Code division Multiple Access) wireless telecommunication system with a digital frequency hopping ability.

[Background Art] Generally, in a wireless telecommunication system, a beacon apparatus and method has been used because of a low cost manufacture, an easy management and repair, a smooth handoff process and a low power amplifier. Presently, IS-95A, IS-95B and CDMA2000 techniques proposed by Qualcomm and W-CDMA system specified by the 3GPP specification have been widely used in the commercialized mobile telecommunication systems. The telecommunications between subscribers are performed through more than one base station in asynchronous and/or synchronous CDMA systems. A first subscriber in a first area can communicate with a second subscriber, who is located in a second area, transmitting data to the second subscriber through a first base station on a reverse link. The first base station may transmit the data to a second base station involved in the second area. The data are transmitted to the second subscriber via a forward link of the second base station (if the first and second subscribers are located in the same area, the same base station is associated with such a communication) . The forward link means the data transmission from a base station to a subscriber and the reverse link means the data transmission from a subscriber to a base station. Different frequencies are respectively allocated to the forward and the reverse links. The base station is synchronized with another base station through a GPS and these base stations are distinguished from each other by PN offset. The PN offset of the base station is different from that of an adjacent base station. However, in the W-CDMA system, it is not necessary to synchronize the base stations through the GPS because the base station is distinguished from another base station by a scrambling code. On the other hand, in the 3GPP2 synchronous CDMA system, the forward link channels, such as the pilot, sync and paging channels, are commonly transmitted to the all subscribers, which are called "overhead channel." In the 3GPP asynchronous CDMA system, a Primary Common Pilot Channel (P-CPICH) , a Secondary Common Pilot Channel (S-CPICH) , a Primary Common Control Physical Channel (P-CCPCH) , a Secondary Common Control Physical Channel (S-CCPCH) , Primary SCH, and a Secondary SCH are representative of the overhead channel commonly transmitted to all the subscribers. A subscriber may move through more than one sector, cell, or base station on the telecommunication with someone. The subscriber may perform a hard handoff to change the used frequency or a soft handoff to change a frame due to the movement of the subscriber or a wireless environment during the telecommunication. At this time, in the CDMA mobile telecommunication system, the pilot beacon apparatus is used for support the hard handoff between different frequencies. The beacon apparatus supports the hard handoff for a continuous connection between the base stations, by shortening a synchronization acquisition time using information of pilot channel, time and the target base station frequency or information of target sector frequency. In general, the beacon apparatus is classified into two kinds of types as follows: 1) Wire communication with base station A beacon apparatus synchronizes with the base station, by receiving information of a code and code transmission time from a base station through a wire connection. However, there are some problems of a management and an installation because of the wire connection between the base station and the beacon apparatus. 2) Wireless communication with base station A beacon apparatus performs' a frequency conversion of all channels wirelessly received from a base station. Therefore, the apparatus needs a high power amplifier for such a frequency conversion. Due to the high power amplification, it is necessary to have an expensive amplifier and a noise problem will be caused.

[Disclosure] [Technical Problem] An object of the present invention is to provide an apparatus and a method for performing a low power consumption, in generating a beacon signal, by using a specific channel for a pilot signal. Another object of the present invention is to provide an apparatus and a method for carrying out an easy frequency conversion in generating a beacon signal. Also, another object of the present invention is to provide an apparatus and a method which can be easily repaired and -managed in generating a beacon signal. Further, another object of the present invention is to provide an apparatus and a method for smoothly processing a handoff using a beacon signal. Still another object of the present invention is to provide an improved beacon apparatus which is manufactured with a • low cost and which guarantees a signal quality of a beacon signal.

[Technical Solution] In accordance with an aspect of the present invention, there is provided a beacon apparatus for a digital frequency conversion comprising: an analog to digital converter; a digital to analog converter; and a DDS (Direct Digital synthesizer) . In accordance with another aspect of the present invention, there is provided a beacon apparatus comprising: the 3GPP2 synchronous CDMA modem for transmitting pilot, sync and paging channels, or the 3GPP asynchronous CDMA modem for transmitting a specific overhead channel.

[Advantageous Effects] A beacon apparatus according to the present invention improves a signal quality and a manufacturing cost, and easily controls the signals through a direct digital frequency conversation that carries out a digital frequency hopping instead of an analogue PLL. Also, the beacon apparatus prevents a call disconnection, by supporting a fast handoff processing through an overhead channel including a pilot signal with a low cost and easy management and repair. Further, in the beacon apparatus according to the present invention, an additional device, such as a GPS and a wire interface, for telecommunication with a base station is not needed. Since a data transmission is carried out only on an essential overhead channel, not on a traffic channel, a low power amplifier with no heat is required instead of a high power amplifier. [Description of Drawings] The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which: Fig. 1 is a schematic block diagram illustrating a pilot beacon apparatus with overhead channel transmission according to the present invention; Fig. 2 is a schematic block diagram illustrating a digital frequency hopping according to the present invention; Fig. 3 is a schematic block diagram illustrating a synchronous 3GPP2 CDMA modem in a beacon apparatus according to the present invention; Fig. 4 is a schematic block diagram illustrating a structure of a sync channel according to the present invention; Fig. 5 is a schematic block diagram illustrating a sync channel messages according to the present invention; and Fig. 6 is a schematic block diagram illustrating an asynchronous 3GPP W-CDMA modem in a beacon apparatus according to the present invention.

[Best Mode] According to an aspect of the present invention, it is characterized in that a beacon apparatus for digitally frequency converting comprises: an analog to digital converter; a digital to analog converter; and a DDS (Direct Digital synthesizer) . According to another aspect of the present invention, it is characterized in that a beacon apparatus comprises: the 3GPP2' synchronous CDMA modem for transmitting a pilot, a sync and a paging channels or the 3GPP asynchronous CDMA modem for transmitting overhead channel.

!_. Direct frequency conversion beacon apparatus First, a beacon apparatus according to the first embodiment of the present invention directly and digitally converts a received frequency, which is called a direct and digital beacon apparatus in the present invention. In this embodiment, even though four FAs (Frequency Allocation) will be illustrated in the direct and digital beacon apparatus, the number of FAs can be increased or decreased. In the forward link from a base station of Fig. 1, the FA signal is down-converted through a mixer 40 and a filter 50, passing through antenna 10 and duplexer 20. A signal within the converted frequency range is called as "IF (Intermediate Frequency)" signal. Generally, a conventional analog type apparatus performs a frequency hopping of a received IF (Intermediate Frequency) signal, converts the hopped signal to a high band signal using a mixer and a filter, amplifies the converted signal through a high power amplifier, and transmits the amplified signal to an antenna through a duplexer. At this time, the analog type apparatus performs the frequency hopping of the received signal using an analog PLL (Phase Lock Loop) . However, in the present invention, the direct and digital beacon apparatus performs frequency hopping using an ADC (Analog To Digital Converter) (reference numeral 90 in Fig. 2), an interpolation filter (reference numeral 91 in Fig. 2), a DAC (Digital To Analog Converter) (reference numeral 93 in Fig. 2) and a DDS (Direct Digital Synthesizer) (reference numeral 104 in Fig. 3) . In the direct and digital beacon apparatus according to the first embodiment, a CDMA modem (reference numeral 100 shown in Fig. 1) does not operate, the interpolation filter 91 works and a MUX 92 is coupled to the interpolation filter 91. In Fig. 2, a frequency line a) shows an IF band signal 200 which has a center frequency frc and a bandwidth BW and a frequency line b) illustrates a frequency characteristic when the received IF signal is sampled at a rate of 1/fsl by an ADC 90 and the sampled signal is processed at the same rate by the DAC 93. On the frequency line b) of Fig. 2, it is clear that a center frequency of the signal outputted from the DAC 93 is located at a point (flc) of the IF band signal 202 (fsl (Sampling rate) -frc (frequency of the signal inputted to the ADC) ) or at a point (fhc) of the IF band signal 203 (fsl+frc) based on the sampling technique. Referring to a frequency line d) of Fig. 2, in case of the digital frequency hopping method using the sampling, completed frequency hopping bands may be expressed as FAl (208), FA2 (209), FA3 (210) and FA4 (211) and a frequency hopping sequence then has a periodic rotation of frequency hopping bands FAl, FA2, FA3 and FA4 (that is, FA1->FA2->FA3->FA4) . Therefore, a high bandwidth HBW (High Bandwidth) may have a full range including all the completed frequency hopping bands. For the frequency hopping of the IF band signals according to the sequence, a signal of the FAl is sampled at an allocated sampling rate of 1/fsl using the ADC 90 and the DAC 93. If the ADC 90 and the DAC 93 perform the sampling successively at a sampling rate of l/fs2, l/fs3, and a l/fs4 for the FA2, FA3, and the FA4 respectively, the completed frequency hopping signal HBW, as shown in the frequency line d) of Fig. 2, is acquired. At this time, the 1/fs sampling rate of ADC 202 is larger than the 1/(2HBW) to avoid aliasing according to the sampling technique. In the digital type frequency hopping method, a spurious or an image signal is effectively eliminated using the interpolation filter 91. A parameter 'm' of the interpolation filter 91 is an integer. In the sampling theory, if the parameter 'm' is larger than 2, it is easy to design a filter used in analog processing steps due to the elimination in a specified frequency band because the image signal is moved to the m*fs frequency band. If the sampling rate of ADC 90 is the 1/fs and the interpolation filter 91 between the ADC 90 and the DAC 93 is used for interpolating the sampled IF signal at the parameter m, the DAC 93 must be operated at a sampling clock of m/fs. On the other hand, the sampling rate is determined as follows: [Equations] fsl = center frequency of FAl - center frequency of received IF signal; fs2 = center frequency of FA2 - center frequency of received IF signal; fs3 = center frequency of FA3 - center frequency of received IF signal; and fs4 = center frequency of FA4 - center frequency of received IF signal, where the sampling frequencies fsl, fs2, fs3, and fs4 are correspondent to the completed frequency hopping bands FAl, FA2, FA3 and FA4, respectively.

The DDS 104 is a clock generator for generating clock signals received by the ADC 90 and the DAC 93. The DDS 104 contributes to a fast frequency hopping through a fast clock change, instead of a conventional analog PLL to require a locking time. When a frequency hopping from one FA to another FA is carried out, a general pilot beacon apparatus does not output a signal for a specific time duration. In the present invention, this duration is called a release time and the above-mentioned operation about the release is called a release function. Meanwhile, the apparatus must outputs a signal for another specific time duration. In the present invention, this duration is called a continuous time and the above-mentioned operation based on such a continuous time is called a continuous function. In the direct and digital beacon apparatus, the release and the continuous function is easily realized by controlling the clock signals, which are provided to . the ADC 90 and the DAC 93 during the release and the continuous time.

2. Overhead channel transmission beacon apparatus Hereinafter, a beacon apparatus capable of transmitting an overhead channel according _ to the second embodiment of the present invention will be described in detail. In this embodiment, a CDMA modem 100 is employed, instead of the interpolation filter 91, and MUX 92 is connected to the CDMA modem 100. The CDMA modem means a synchronous 3GPP2 modem or an asynchronous 3GPP modem.

2-1. Channel structure of a synchronous CDMA system Fig. 4 shows a sync channel structure of Synchronous CDMA International Specifications. In the Specification, a 80ms superframe of the sync channel includes three frames of 26.66ms. Data, some of the superframes, are transmitted by the sync channel. One frame to be transmitted includes 32-bit data and one superframe includes a 96-bit data. Therefore, the sync channel can transmit data at a transmission of 1.2Kbps. Also, the frame of 32-bit data includes 31-bit real data and a start of message (SOM) of one bit for indicating a start and continuity of a sync channel message. The SOM bit of a first frame in a sync channel message capsule is "1", that of the others frames is "0" for indicating the continuity of the sync channel message. The sync channel message capsule includes the sync channel message and padding. The total data bits which are transmitted by one capsule is 93*N bits. The parameter ΛN' is the number of the superframes. Furthermore, the sync channel message includes MSG_LENGTH, MSG_BODY and CRC bits. In the synchronous CDMA system, a system time is a value that is counted every 80ms from GPS' s start time, 00:00:00, January 6, 1980. A starting point of a short PN code is the same as that of a long code; however, it will take 3,700 years to make the starting points of these two codes be the same again. A SYS_TIME, which is transmitted from the overhead channel beacon apparatus and included in the sync channel message, is a value that is counted every 80ms during a time difference (system time - pilot offset) after the last sync channel message has been transmitted. As a result, the value means the system time having a λ0' pilot offset. Also, at this time, the long code state is calculated and transmitted as LC_STATE in the sync channel message. The SYS_TIME and the LC_STATE in the sync channel message are influenced by the system time and the CRC (Cyclic redundancy Check) is also changed because the MSG_BODY in the sync channel is changed by these two massages.

2-2. Paging channel structure in a synchronous CDMA system A paging channel transmits information of an overhead, calling, command and channel allocation from a base station to a subscriber. The important message related to a hard handoff in a paging channel is the overhead message to transmit system information and the overhead messages includes: (A) System Parameter Message; (B) Access parameter Message; (C) Neighbor List Message; and (D) CDMA Channel List Message Besides, in the paging channel message, a Global Service Redirection Message is an important message to support the handoff of a terminal in an idle state.

2-3. The beacon apparatus transmitting overhead channel Referring to Figs. 1, 2 and 3, the beacon apparatus capable of transmitting an overhead channel comprises: a pilot searcher 103 for acquiring an initial synchronization using a pilot channel from a base station; a code power analyzer 108 for analyzing a relative power strength of the received pilot, the sync and the paging channels in channel transmission in a down link of the base station; a time compensator, such as a DLL (Delay Lock Loop) 110, for compensating for a time difference between the BS (base station) clock and the signal time to be transmitted based on the initial synchronization acquired by the pilot searcher; an overhead channel receiver for receiving the overhead channel which includes a paging channel receiver 120 and a sync channel receiver 110; a sync channel message generator 130 and a paging channel message generator 150 for generating overhead channel messages using messages acquired on the overhead channel; a CDMA modulator 160 having a pilot generator 161 and an overhead channel generator (162 and 163), which generates a pilot channel PN code using time information from the pilot searcher 103 and the DLL loop 102, generates overhead messages using information acquired by the overhead channel receiver, and modulates the generated overhead messages using CDMA modulation based on a pilot channel modulation " time arranged to the compensated time; a phase equalizer 106 for compensating for a phase distortion of a RF signal to be transmitted and filtering the modulated CDMA messages (107); a digital up-converter (Digital Mixer) 105 for converting the outputted signal from the Phase equalizer 106 to a IF band; a RF receiving part 10, 20, 30, 40 and 50 for receiving wireless signals; and a RF transmitting part 10, 20, 60, 70 and 80 for converting the IF band pilot channel and the overhead channel to a RF band and transmitting the RF band channels. The received forward link wireless signals through the RF receiving part 10, 20, 30, 40 and 50 are converted to the IF band. The converted signals are also converted to a base band I and Q signal in the ADC 90 and a QPSK demodulator 101.

2-3-1. The pilot searcher 103 acquires code and time information of the received pilot channel, which is included in the received forward link signals from the base station, by searching for energy of the pilot channel from the base band I and Q signals.

2-3-2. The DLL 102 compensates for the time difference (drift or skew) between the base station clock signal and the beacon apparatus, by continuously tracking the pilot channel and provides a system clock signal for the CDMA modulator 160. The time information acquired by the tracking operation of the DLL 102 is used to control a CDMA modulation time for transmission of the pilot and the overhead channel. That is, the time information is used for compensation of the time difference between the reception and the transmission of pilot channel. 2-3-3. The code power analyzer 108 analyzes power of the received forward link pilot channel and the sync and the paging channels in order that a relative power rate of the received channels is the same as that of the transmission channels (the pilot, sync and paging channels) to be transmitted in the beacon apparatus. This relative power rate is used to setup the channels to be transmitted by the CDMA modulator 160.

2-3-4. The overhead channel receiver (110 and 120) receives an overhead channel from the forward link signal using the code and time information acquired by the pilot searcher 103 and the DLL 102. In the synchronous CDMA system, the overhead channel receiver includes the sync channel receiver 110 and the paging Channel receiver 120 for demodulation of the received sync and paging channels. The overhead channel receiver performs PN despreading and Walsh decovering of the base band I and Q signals using demodulators 111 and 121, eliminating frequency, time and phase distortion remained at the sync and the paging channels and demodulating the sync and the paging channels using deinterleavers 112 and 122 and viterbi decoders 113 and 123.

2-3-5. An 80ms_timer 140 is a counter to generate a value every 80ms for compensating for an error in generating and transmitting a transmission system time TX_SYS_TIME in the beacon apparatus.

2-3-6. The sync channel message generator 130 generates the sync channel messages to be transmitted and includes a Fixed sync channel message generator 131 and a real time sync channel message generator 132. As shown in Fig. 5, sync channel structure specified in IS95A, IS95B and cdma2000 specifications will be described in detail. The sync channel message body 312 includes P_REV, MIN_P_REV, SID, NID, PILOT_PN, LC_STATE, SYS_TIME, LP_SEC, LTM_OFF, DAYLT, PRAT, CDMA_FREQ and EXT_CDMA_FREQ. In the present invention, to discriminate messages transmitted by the beacon apparatus from messages received by the beacon apparatus, the messages (which the beacon apparatus receives) from a base station is called "a sync channel message body 312." If a CRC error is not occurred during the sync channel reception from the base station, the message body demodulated by the sync channel receiver 110 and the message body transmitted by the base station are the same. However, when a CRC error is detected through a CRC check process, the received messages is not used for transmission of the overhead channel in the beacon apparatus according to the present invention. Basically, the overhead channel, which is demodulated, CDMA modulated and transmitted by the overhead channel beacon apparatus, have a time difference between the reception and the transmission. In the sync channel, the messages are changed due to the time difference and the time difference has an effect on the "X_SYS_TIME" and the VTX_LC_STATE" of the sync channel message body field. Also, the CRC 333 is recalculated due to the change of the messages. The "TX_SYSJTIME" and the λλTX_LC_STATE" are regenerated by the real time sync channel message generator 132. The other fields except for the two fields are generated by the fixed sync channel message generator 131. The fixed sync channel message generator 131 generates P_REV, MIN_P_REV, SID, NID, ILOT_PN, LPJSEC, LTMJDFF, DAYLT, PRAT, CDMA_FREQ and EXT_CDMA_FREQ fields.

2-3-6-1. A real time sync channel message generator The real time sync channel message generator 132 generates the TX_SYS_TIME and the TX_LC_STATE using some parameters and these parameters will be described in detail below. SYSJTIME: a value counted by a 80ms timer, starting at 00:00:00 AM, January 6f 1980, as a message transmitted via the sync channel of the base station in the synchronous CDMA system. TX_SYS_TIME: a system time message (327) to be transmitted by the overhead channel beacon apparatus. SYNC_PROCESSING_TIME: time taken from an acquisition of a valid SYSJTIME message from the sync channel receiver 110 until a TX_LC_STATE value calculated by the SYS__TIME message is applied to the CDMA modulator 160 and this time is expressed as an integer that is counted every 80ms. LC_STATE: a status value of the long code transmitted on the sync channel of the base station in the synchronous CDMA system. TX_LC_STATE: LC_STATE to be transmitted by the overhead channel beacon apparatus. SOM_START__TIME: a time value of the 80ms_Timer 140 at a point of time the SOM of the sync channel has "1" when the sync channel receiver 110 demodulates the sync channel messages, i.e., a time value of the 80ms_Timer in the first superframe of the sync channel on which the sync channel message starts. SYNC_GET_TIME: time taken from the SOM_START_TIME until the demodulation of the sync channel message, without there being an CRC error, has been completed and this time is expressed as an integer that is counted every 80ms. If the demodulation of the sync channel is performed with real time, the SYNC_GET_TIME and a SYNC_CAPSULE_TIME have the same values and, if the demodulation thereof is performed with delay time, the SYNC_GET_TIME is larger than the SYNC_CAPSULE_TIME. ) SYNC_CAPSULE_TIME: an integer obtained by counting the time from start to end of the valid sync channel message capsule every 80ms SYS TIME UPDATE: a value for updating the 80msJTimer 140 described as follow: [Equation] SYS_TIME__UPDAT= SYSJTIME + SYNC_CAPSULE_TIME - SYNC_PROCESSING_TIME - SYNC_GET_TIME

Hereinafter, the SYS_TIME_UPDAT' and the LC_STATE will be described in detail. Clock signals used in the 80ms_Timer 140 are synchronized with those of the base station. If they are not synchronized with each other, the 80msJTimer 140 may use, during the SYNC_PROCESSINGJTIME, other clock signals which have a maximum offset of less than +4Oms as compared with the clock signals of the base station. The starting point of the 80ms_Timer 140 is random before the valid sync channel message is acquired; however, if when the valid sync channel message is demodulated in the sync channel receiver and the SYS_TIME is then obtained, the 80ms_Timer 140 is updated by it. On the other hand, the sync channel receiver is determined if the SOM is "1" and read the SOME_STARTJTIME (time value of the 80ms_Timer) at a point of time the SOM is "1". If the SOM of "1" is received by the sync channel receiver 110, the sync channel receiver 110 performs demodulation, deinterleaving, Viterbi decoding processes to demodulate the sync channel message and performs a CRC checking process to determine if there is an error. If the CRC error is checked, the received sync channel message is abandoned. If it is not checked, the 80ms_Timer 140 is restarted or updated by the acquired SYSJTIMEJJPDATE. The continuous initialization of the valid SYS_TIME_ϋPDATE through the 80ms_Timer 140 compensates for the time difference between the clock signals of the base station and those of the pilot beacon apparatus according tot the present invention. If the 80ms_Timer 140 is restarted by the valid SYS_TIME_UPDATE, the time value of the 80ms_Timer, which is obtained after the restart, is the same as the sync time transmitted through the synch channel of the base station and is updated every 80ms. Thereafter, it is used as a time value of the TX_SYS_TIME 327. Hereinafter, the "LC_STATE" will be described in detail. The LC_STATE in the sync channel messages, which are transmitted from the BS in the synchronization CDMA system, is system long code information associated with the SYS_TIME. The long code for data scrambling is generated at 1.2288MHz chip rate using 42 phase shift registers and is synchronized with the synchronous CDMA system. Typically, a long code generator having a m-sequence characteristic acquires long code state values by mixing sequence outputs by using a mask vector in the shift registers to create a shift value at a specified time. This method for acquisition of the status value at the specified time has been developed by Qualcomm and widely used. The TX_LC_STATE in the MSG_BODY field of sync channel transmitted by the overhead channel beacon apparatus is calculated by Long code status calculator 133 based on a current value of the 80ms_Timer 140 as set forth in the above-mentioned method.

2-3-6-2. A fixed sync channel message generator The fixed sync channel message generator 131 generates other messages except the TX_SYS_TIME and the TX_LC_STATE. The others messages are generated using the received sync channel messages without any change. For the generation, the previously acquired other messages may be saved in a memory. Hereinafter, a sync channel message capsule structure transmitted by the overhead channel beacon apparatus will be described in detail. Fig. 5 shows the structure of the base station sync channel message capsule (311, 312 and 313) transmitted from the BS and receiving and transmission sync channel message capsules (321, 322, 323 331, 332 and 333) received and transmitted by the overhead channel beacon apparatus. The sync channel message capsule (331, 332 and 333) to be transmitted by the overhead channel beacon apparatus includes Padding and sync messages which include the TX_SYS_TIME, the TX_LC_STATE and the other sync channel messages generated by the real time 132 and the fixed sync channel message generator 131. After a new TX_CRC corresponding to the changed sync channel message is newly obtained, the perfect capsule is generated by filling the CRC field with the calculated TX_CRC and by processing zero padding for unused fields. Therefore, the transmission sync channel message capsule 331, 332 and 333 transmitted by the overhead channel beacon apparatus includes P_REV, MIN_P_REV, SID, NID, PILOT_PN, TX_LC_STATE, TX_SYS_TIME, LP_SEC, LTMJDFF, DAYLT, PRAT, CDMA_FREQ and EXT_CDMA_FREQ.

2-3-7. The paging channel message generator 150 generates a message to be transmitted from the overhead channel beacon apparatus. With respect to a hard handoff, there are five important ones of the transmission messages transmitted on the paging channel of the overhead channel beacon apparatus. The five messages include system information, such as "System Parameters Message", "Access parameters Message", "Neighbor List Message", "CDMA Channel List Message", which are related to hard handoff, and "Global Service Redirection Message" which is related to overhead information to support the handoff on idle state of a terminal. The five messages should be transmitted on the paging channel. The other messages may be transmitted according to the user's selection. The five and other messages are acquired by demodulation of a paging channel received in the paging channel receiver 120. 2-3-8. The CDMA modulator 160 performs the CDMA modulation of the sync channel message capsule and the paging channel messages acquired based on the above-mentioned modulation. Time information about the CDMA modulation related to the channels transmitted by the overhead channel beacon apparatus is in compliance with the synchronous CDMA system international specifications, because the received sync and paging channels are arranged to the received pilot channel. In the CDMA modulator 160, each start point of the sync and paging channel messages is modulated in order to be matched with the received pilot channel start point, and the pilot channel offset from the overhead channel beacon apparatus is matched with the received pilot channel offset using a time information of the pilot channel acquired by the pilot searcher 103. The CDMA modulator 160 modulates the channels based on the previously acquired relative power rate of the channels detected by the code power analyzer 108 in the above mentioned method.

2-3-9. A FIR filter 107 performs a filtering process of the CDMA channels modulated in CDMA modulator 160.

2-3-10. A phase Equalizer 106 compensates for a phase distortion of processed signal in the FIR filter 107. 2-3-11. A digital Mixer 105 performs a digital conversion of the output signal from the phase Equalizer 106 to IF band.

2-3-12. A mux 92 selectively outputs to the DAC 93 a signal from the digital mixer 105 or the interpolation filter 91 based on the operation of the overhead channel beacon apparatus.

3. Hereinafter, a overhead channel beacon apparatus in an asynchronous W-CDMA system according to the third embodiment of the present invention will be described in detail. As shown in Fig. 6, in the asynchronous W-CDMA system, the beacon apparatus capable of transmitting an overhead channel comprises; a pilot search/code sync acquisition unit 203 for acquiring code synchronization of SCH (sync channel) and for performing pilot search of P-CPICH (Primary-Common pilot channel: pilot channel) ; a code power analyzer 208 for analyzing a relative power strength of SCH, P-CPICH and CCPCH (P- CCPCH, S-CCPCH: Primary-Common Control Physical channel, Secondary-Common Control Physical channel) to be transmitted by the overhead channel beacon apparatus, referring to a received down link channel of the base station; a DLL (Digital Lock Loop) 202 for compensating for time difference between base station clock signals using synchronization information acquired from the pilot search/code sync acquisition unit 203; an overhead channel receiver including a P-CCPCH receiver 210 and S-CCPCH receiver 220 for receiving the overhead channel; a P-CCPCH message generator 233 and a S-CCPCH message generator 250 for generating overhead channel messages to be - transmitted in the overhead channel beacon apparatus using the messages acquired from the received overhead channel; a CDMA modulator 260 for generating the SCH and the P-CPICH to be transmitted from the overhead channel beacon apparatus using the time information acquired from the pilot search/code sync acquisition unit 203 and the DLL 202, generating overhead messages using information acquired from the overhead channel receiver, and modulating the generated overhead messages using the SCH and P-CPICH 261, the S- CCPCH 262 and the P-CCPCH 263 which are arranged for the compensation time in the CDMA modulation; a digital up converter (Digital Mixer) 205 for converting the outputted signal from the FIR filter 207 to an IF frequency band; a RF receiver (including a plurality of elements 10, 20, 30, 40 and 50) for receiving the down link channels; and a RF transmitter (including a plurality of elements 10, 20, 60, 70 and 80) for converting the pilot and the overhead IF band channels to RF band and transmitting the converted channels in the CDMA modulation.

3-1. The pilot search/code sync acquisition unit 203 acquires the code and the time information about the received down link channels through the energy search of base band I and Q signals of the SCH and the P-CPICH.

3-2. The DLL (Digital Lock Loop) 202 compensates for the time difference between the BS clock signal and the signal transmitted from the overhead channel beacon apparatus due, and continuously performs tracking of the P-CPICH about time information. The time information acquired by the tracking of the DLL 202, is used to control a CDMA modulation time for transmission of the SCH and P-CPICH and the overhead channel. That is, the time information is used for compensation of the time difference between the reception and the transmission on the P-CPICH.

3-3. The code power analyzer 208 analyzes the relative power rate of the SCH, P-CPICH, P-CCPCH and S- CCPCH in the down link and sets up the relative power rate of the SCH, P-CPICH, P-CCPCH and S-CCPCH to be transmitted in the overhead channel beacon apparatus in order that it has the same rate as that on the SCH, P- CPICH, P-CCPCH and S-CCPCH in the down link. The relative power rate among the SCH, P-CPICH, P-CCPCH and S-CCPCH in the down link, which is analyzed by the analyzer 208, is used for setting up the power rate of the channels to be transmitted by the CDMA modulator 260 in the overhead channel beacon apparatus. 3-4. The overhead channel receiver receive an overhead channel from the down link signal based on the code and time information acquired from the pilot search/code sync acquisition unit 203 and the DLL 202. In the asynchronous CDMA system, the overhead channel receiver includes the P-CCPCH receiver 210 and the S- CCPCH receiver 220 for demodulation of the P-CCPCH and the S-CCPCH messages. The overhead channel receiver performs scrambling Code De-spreading and OVSF (Orthogonal Variable Spreading Factor) Code De-covering of the base band I and Q signals using demodulators 211 and 221, performs elimination of frequency, time and phase distortion remained in the channels, and performs demodulation of the P-CCPCH and S-CCPCH using deinterleavers 212 and 222 and Viterbi decoders 213 and 223.

3-5. The P-CCPCH message generator 233 generates messages on the P-CCPCH.

3-6. The S-CCPCH message generator 250 generates messages on the S-CCPCH.

3-7. The CDMA modulator 260 performs modulation of the massages of the P-CCPCH and S-CCPCH. The CDMA modulation in the CDMA modulator 260 is carried out using the code and time information of P-CPICH acquired using the pilot search/code sync acquisition unit 203 and DLL 202 in order that the time offset of the P-CPICH to be transmitted in the overhead channel beacon apparatus is the same as that of the received P-CPICH. The CDMA modulator 260 modulates the channels according to the above mentioned power rate of the channels acquired from the analyzer 208.

3-8. A FIR filter 207 performs filtering operation of the output signal from the CDMA modulator 260.

3-9. A digital Mixer 205 performs a digital conversion of the filtering signal in the FIR filter 207 to the IF band.

3-10. A mux 92 outputs to the DAC 93 the signals from the digital mixer 205 or the interpolation filter 91 according to operation of the overhead channel beacon apparatus.

Although the present invention illustrates the direct and digital beacon apparatus based on the 3GPP2 synchronous CDMA modem and the 3GPP2 asynchronous CDMA modem, it is possible to combine the direct and digital beacon apparatus and the synchronous and asynchronous CDMA modem.

[industrial Applicability] The present invention is used for a beacon signal generation apparatus (beacon apparatus) for supporting the handoff in a wireless telecommunication system.