Abstract:
A transmitter provided in a mobile station of a CDMA communications system comprises a plurality of orthogonal modulators for orthogonal-modulating channel-coded transmitted signals with the orthogonal codes of corresponding channels, a plurality of gain adjustments for adjusting the gains of corresponding channels by selecting gain control signals of the channels or the complements of the gain control signals according to the orthogonal-modulated signals, and a plurality of circuits for separating the transmission signals of the gain adjusted channels into I-channel signals and Q-channel signals and band-spreading the I- and Q-channel signals with a PN sequence of the mobile station. A method for performing such transmission is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a transmitter of a mobile station in a CDMA (Code Division Multiple Access) communications system, and more particularly to such transmitter for controlling the channel gain of a transmitted binary signal and integer-spreading it. 
     2. Description of the Related Art 
     Referring to FIG. 1 for illustrating the structure of the transmitter of a mobile station in a conventional CDMA communications system, the orthogonal modulator  111  multiplies the transmitted signal of each channel by a corresponding orthogonal code of the channel to orthogonal spread the channel. The orthogonal code may be a Walsh code. The long PN (pseudo-noise) code spreader  113  and short PN code spreader  115  spread the transmitted signal of each channel modulated with the orthogonal code. The long code is for identifying the mobile station, and the short code is for identifying the base station. The base band filter  117  filters the spread transmitted signal into the base band. The modulator  119  modulates the transmitted signal of the base band with a carrier wave. 
     Such a conventional transmitter of the mobile station spreads binary data which has not been adjusted for channel gain after orthogonal modulation, and then filters the spread binary data, so that it requires a circuit for binary mapping to obtain binary data. Furthermore, additional multipliers are necessary for spreading the obtained binary data in long code and short code, complicating the hardware structure. Although FIG. 1 does not show the additional parts for gain adjustment, it will be readily noted that the circuit for binary mapping is required including additional multipliers. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a CDMA mobile phone with a simplified circuit for adjusting the channel gain, and method therefor. 
     It is another object of the present invention to provide a CDMA mobile phone with a simplified circuit for band spreading, and method therefor. 
     It is another object of the present invention to provide a CDMA mobile phone with a circuit for band spreading with adjustment of the channel gain without binary mapping. 
     According to the present invention, a transmitter provided in the mobile station of the CDMA communications system comprises an orthogonal modulator for orthogonal-modulating channel-coded transmission signals with the orthogonal codes of corresponding channels, a gain control value generator for obtaining the complement of a first channel gain control value corresponding to each channel to generate a second channel gain control value, and a selection circuit for selecting one of the first and second channel gain control values by the orthogonal-modulated signals. 
     The present invention will now be described more specifically with reference to the drawings attached only by of example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram for illustrating the structure of the transmitter of a conventional CDMA mobile station; 
     FIG. 2 is a schematic circuit diagram for illustrating the structure of the transmitter of a CDMA communications system according to the present invention; 
     FIG. 3 is a block diagram for illustrating the structure of a gain adjustment for multiplying the orthogonal-modulated data of FIG. 2 by the channel gain; and 
     FIG. 4 is a block diagram for illustrating the structure of a complex spreader for spreading the input data by the short PN code spread with the long PN code of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 2, the transmitter of the mobile station of a CDMA communications system according to the present invention includes a pilot channel for transmitting a pilot signal, a dedicated control channel for exclusively transmitting the control data of the mobile station to the base station when a link is established, a supplemental channel for transmitting packet or video data to the base station, and a fundamental channel for transmitting voice data to the base station. 
     The signal of the dedicated control channel is multiplied by the orthogonal code WGN 1  allotted to the control channel through a multiplier  212 . The signal of the supplemental channel is multiplied by the orthogonal code WGN 2  allotted to the supplemental channel through a multiplier  214 . The signal of the fundamental channel is multiplied by the orthogonal code WGN 3  allotted to the fundamental channel through a multiplier  216 . These multipliers serve as the orthogonal modulators to respectively modulate the transmitted signals with corresponding orthogonal codes. The orthogonal codes are respectively allotted to the transmission channels, and may be Walsh codes. 
     The gain of the dedicated control channel is adjusted by a gain adjustment  218  controlling the output of the multiplier  212  with the gain control value Gc of the dedicated control channel. The gain of the supplemental channel is adjusted by a gain adjustment  220  controlling the output of the multiplier  214  with the gain control value Gs of the supplemental channel. The gain of the fundamental channel is adjusted by a gain adjustment  222  controlling the output of the multiplier  216  with the gain control value Gf of the fundamental channel. The pilot channel signal and the output of the gain adjustment  218  are combined by an adder  224 . The output of the gain adjustment  220  and the output of the gain adjustment  222  are combined by an adder  226 . 
     A multiplier  228  is provided to multiply a short PN sequence PNi of an I-channel by a long PN sequence (long code). A multiplier  230  is provided to multiply the short PN sequence PNq of a Q-channel by the long PN sequence. In this case, the long code represents the identification code allotted by the base station to the mobile station while the PN sequences PNi and PNq represent the identification code of the base station communicating with the mobile station. Hence, the short PN sequences and long code serve as the codes for the base station to distinguish the mobile station. 
     The output of the adder  224  and the output of the multiplier  228  are multiplied and spread by a multiplier  232 . The output of the adder  226  and the output of the multiplier  228  are multiplied and spread by a multiplier  234 . The output of the adder  226  and the output of the multiplier  230  are multiplied and spread by a multiplier  236 . The output of the adder  224  and the output of the multiplier  230  are multiplied and spread by a multiplier  238 . A subtractor  240  is also provided to subtract the output of the multiplier  236  from the output of the multiplier  232 . The output of the multiplier  234  and the output of the multiplier  238  are combined by an adder  242 . This arrangement allows for spreading the transmitted signal of each channel with the PN sequences, and in particular allows for complex spreading of the transmitted signal with the long code and with the short PN sequences. 
     The output signal of the subtractor  240  is filtered through a band-pass filter  244  into a base band. The output signal of the adder  242  is filtered through a band-pass filter  246  into a base band. The output signal of the band-pass filter  244  is controlled by a gain adjustment  248  according to a pilot channel gain control value Gp so as to adjust the total gain of the signal transmitted through the I-channel. The output signal of the band-pass filter  246  is controlled by a gain adjustment  250  according to the pilot channel gain control value Gp so as to adjust the total gain of the signal transmitted through the Q-channel. The output signal of the multiplier  248  is multiplied by a carrier wave cos(2π fct) through a multiplier  252 , and the output signal of the multiplier  250  multiplied by a carrier wave sin(2π fct) through a multiplier  254 . Finally, the output signals of the multipliers  252  and  254  are added by an adder  256  to produce the transmission signal of the mobile station. This arrangement constitutes the modulation. Thus, the data inputted through the channels are multiplied by their respective orthogonal codes corresponding with the multipliers  212  to  216  to produce the orthogonal-modulated signals. 
     Referring to FIG. 3, the structure of the gain adjustments  218 , 220 , 222  includes a 2&#39;s complement circuit  311  to convert the gain control value into a complement of “2”. The gain control value and the complement of “2” are inputted to a multiplexer  313  which also receives an orthogonal-modulated signal as a selection signal. Thus, the multiplexer  313  selects the gain control value or the complement of “2” according to the logic of the orthogonal-modulated signal. Meanwhile, the orthogonal-modulated signal is inverted by an inverter  315 , and combined with the output signal of the multiplexer  313 . In this case, the orthogonal code generated from the inverter  315  serves as a sign bit (MSB). 
     Describing the operation of the gain adjustments  218 - 222  having the structure as shown in FIG. 3, the multipliers  212 - 216  are 1-bit multipliers for performing 1-bit multiplication, and therefore may consist of exclusive-OR gates. The output signals of the multipliers  212 - 216  are inputted to their respective gain adjustments  218 - 222 . The orthogonal-modulated transmission signals applied to the gain adjustments  218 - 222  are “1” or “0”, and are delivered as selection signals to the multiplexer  313 . In this case, the selection signals are integer data. Then, the multiplexer  313  selectively outputs the channel gain control value or 2&#39;s complement thereof. The channel gain control value is for adjusting the gain of the corresponding channel, and the 2&#39;s complement of the channel gain control value is taken by the 2&#39;s complement circuit. These values are binary data. The orthogonal-modulated signal is inverted by an inverter  315 , and is outputted as a sign bit combined with the channel gain control value or its 2&#39;s complement of the multiplexer  313 . After the spread signal gains of the channels are adjusted by corresponding gain adjustments  218 - 222 , the adders  224  and  226  combine the output signals of the channels as described. 
     More specifically describing the operation of the circuit as shown in FIG. 3, the orthogonal-modulated transmission signals produced from the Walsh modulator of the multipliers  212  to  216  have a value of 1 (corresponding to +1) or 0 (corresponding to −1). Hence, if the output of the Walsh modulator is 1, the sign bit (output data[ 8 ]) of the inverter  315  becomes 0(zero), and accordingly the multiplexer  313  selects the channel gain control value, so that the finally outputted data [ 8 : 0 ] comes to have a positive sign bit. Namely, the channel gain control value becomes the output data [ 7 : 0 ] itself. By contrast, if the output of the Walsh modulator is 0, the sign bit (output data) of the inverter  315  becomes 1, and accordingly the multiplexer  313  selects the 2&#39;s complement of the channel gain control value, so that the final output data [ 8 : 0 ] comes to have a negative sign bit, with the 2&#39;s complement becoming the output data [ 7 : 0 ]. Thus, the circuit as shown in FIG. 3 multiplies the Walsh modulated data by the gain. 
     The transmitter as shown in FIGS. 2 and 3 modulates the transmission data inputted to each channel with the corresponding orthogonal code, and multiplies the resulting orthogonal-modulated signal by the gain control value of the corresponding channel. In this case, the gain control values Gc, Gs, Gf respectively supplied from a controller (not shown) to the gain adjustments  218  to  222  are for adjusting the gains of the orthogonal-modulated signals of the corresponding channels. Then, the data from the pilot channel is combined with the data from the dedicated control channel, and the data from the supplemental channel is combined with the data from the fundamental channel, in order to obtain I-channel data and Q-channel data respectively applied to the I- and Q-channels of the complex spreader. The complex spread data is then applied to the band-pass filters  244  and  246 , whose output signals are adjusted for gains and then loaded on the carrier waves. 
     Describing more specifically the operation of the gain adjustments  218  to  222  with reference to FIG. 3, the sign bit of the output data is obtained by inverting the orthogonal-modulated signal by the inverter  315 . The orthogonal-modulated signal is simultaneously applied as the selection signal to the multiplexer  313 . In this case, the output signal (excluding the sign bit) becomes the gain control value or the complement of “2” thereof, depending upon whether the orthogonal-modulated signal is a “1” or a “0”. An output circuit (not shown) adds the inverted signal of the orthogonal modulated signal as a sign bit to the output signal of the multiplexer. In the present embodiment, the input data corresponding to the gain is 8-bit (0-255), where the output data is 9-bit. It may be also applied when the bit size of the input data is arbitrarily determined. 
     FIG. 4 illustrates the structure of a complex spreader for spreading the integer type input data by using the PN sequence spread by the long code. The 2&#39;s complement circuit  412  selects the 2&#39;s complement of the input data [ 7 : 0 ] excluding the input data [ 8 ] representing the sign bit of the input data [ 8 : 0 ] produced from the adders  224  and  226 . The output data of the adders  224  and  226  and of the complement circuit  412  are delivered to a multiplexer  414 , which also receives as the selection signal the PN sequence spread by the long code supplied by the multipliers  228  and  230 , so that the multiplexer  414  may select the input data [ 7 : 0 ] or the 2&#39;s complement thereof. The spread PN sequence and the input data [ 8 ] representing the sign bit are logically combined by an exclusive NOR gate  416 , whose output is combined with the output of the multiplexer  414 , generating the output data [ 8 : 0 ]. In this case, the output of the XNOR  416  serves as the sign bit (MSB) of the output data [ 7 : 0 ] produced from the multiplexer  414 . 
     Describing the operation of the circuit of FIG. 4, the input data [ 8 : 0 ] is the output data [ 8 : 0 ] of the adders  224  and  226 , having positive or negative value according as the sign bit [ 8 ] is 0(zero) or 1. Meanwhile, the spread PN sequence supplied by the multipliers  228  and  230  has a value of 1(corresponding to +1) or 0(corresponding to −1). The circuit is to multiply the input data [ 8 : 0 ] by the PN sequence. If the PN sequence is 1, the input data [ 8 : 0 ] is multiplied by +1, producing the output data [ 7 : 0 ]. In this case, the sign bit [ 8 ] of the output data is determined by the sign bit [ 8 ] of the input data. Hence, the input data [ 8 ] and the spread PN sequence are logically combined by XNOR gate  416 . If the spread code is 0, the input data is multiplied by −1, producing the output data [ 7 : 0 ] which is the 2&#39;s complement of the input data [ 7 : 0 ], so that the sign bit [ 8 ] of the input data is inverted. Consequently, the input data [ 8 ] and the spread PN sequence are logically combined by the XNOR gate  416  to produce the output data [ 8 ]. Thus, the circuit of FIG. 4 uses the PN code spread by the long code to spread the integer type input data adjusted by the gain adjustments  218  to  222 . The sign of the output data becomes positive or negative depending on whether the sign of the spread PN sequence is equal to that of the input data. In this case, the output data excluding the sign bit becomes the complement of “2” of the input signal except for the sign bit, or the input signal except for the sign bit, depending on whether the short PN sequence spread by the long signal is “0” or “1”. In the present embodiment, the input data is 8-bit. It may be also applied when the bit size of the input data is arbitrarily determined. 
     In the above embodiments, it is assumed that the orthogonal-modulated signal and spread PN sequence have the value of 1 or 0 to correspond to +1 or −1. However, these may be conversely defined. Namely, if it is defined that these have the value of 1 or 0 to correspond to −1 or +1, the inverter  315  of FIG. 3 is not required, and the XNOR gate  416  should be replaced by an XOR gate. 
     As described above, the inventive transmitter does not require a circuit for multiplying the orthogonal-modulated signal converted into binary data by the channel gain control value. Instead, it is structured to select the channel gain control value or the 2&#39;s complement thereof depending on the orthogonal-modulated data, thereby simplifying the hardware structure. Moreover, it does not require a circuit for multiplying the spread PN sequence converted into binary data by the input data. Instead, it is structured to select the input data or the 2&#39;s complement thereof depending on the spread PN sequence. While the present invention has been described with specific embodiments accompanied by the attached drawings, it will be appreciated by those skilled in the art that various changes and modifications may be made thereto without departing from the gist of the present invention.