Abstract:
Provided is an apparatus for modulation in a base station with a smart antenna. The smart antenna system has many advantages that it is possible to deal with the large volume of subscribers; communication quality is increased; etc. However, the smart antenna system has disadvantages that cost is increased due to many antennas; base station transceivers have a complicated structure due to multiple antennas per base station; it is too complicated to manage resource and channel allocation; there is required compatibility with a conventional system; etc. The present invention provides an apparatus for modulation in a base station with a smart antenna, which can solve the foregoing problems by employing a modulator using a time division multiplexing method, a sector beam selector, and a TX beam former, thereby providing good compatibility regardless of a change in the number of base station sectors and the number of antennas.

Description:
BACKGROUND  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an apparatus for modulation in a base station with a smart antenna.  
         [0003]     2. Description of the Related Art  
         [0004]     A smart antenna system uses multiple antenna elements and adjusts a gain and a phase of signals received from the respective antenna elements, so that a base station receives a signal transmitted from a user in only a desired direction and largely decreases a noise signal level due to multiple-access interference with signals transmitted from other directions, thereby improving performance of the system and increasing channel capacity of the base station. In particular, the smart antenna system is called an antenna array system to be applied to mobile communication, and its frequency efficiency has been recently exhausted. Further, according as the mobile communication has recently been improved in quality and the system adaptive to high-speed data transmission has actively researched, there have been studied on the smart antenna system and concern about the smart antenna system has been also growing.  
         [0005]     In the smart antenna system, a concept of a spatial division multiple access (SDMA) system is used, so that the gain of the desired signal source is increased and thus a region corresponding to one base station is expanded, thereby reducing the number of the base stations as compared with those of a conventional system. Further, in the smart antenna system, only a selected signal source is intensively detected, so that power consumption of a terminal is reduced as compared with that of the conventional system, and thus call duration and battery lasting time of the terminal can be increased. Also, the smart antenna system allows one base station to serve more subscribers than that of the conventional system in the case of voice communication, and the high-speed data transmission to be possible in the case of data communication.  
         [0006]     As compared with the conventional system, the smart antenna system has many advantages that it is possible to deal with the large volume of subscribers, communication quality is increased, etc. However, the smart antenna system has disadvantages that cost is increased due to an increase of many antennas; base station transceivers have a complicated structure due to the use of multiple antennas in the base station; it is too complicated to manage resource and channel allocation; there is required compatibility with a conventional system; etc.  
         [0007]     On the other hand, in order to meet a wideband code division multiple access (WCDMA) specification, which is applied to the present invention, a base station modulator should perform modulation of physical channels in a forward link such as a dedicated physical channel (DPCH), a primary common control channel (P-CCPCH), a secondary common control channel (S-CCPCH), a physical downlink shared channel (PDSCH), a primary common pilot channel (P-CPICH), a secondary common pilot channel (P-CPICH), a primary synchronization channel (P-SCH), a secondary synchronization channel (S-SCH), an acquisition indicator channel (AICH), an access preamble acquisition indicator channel (AP-AICH), a collision detection/ channel assignment indicator channel (CD/CA-ICH) and a paging indicator channel (PICH).  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention is directed to an apparatus for modulation in a base station with a smart antenna, which can solve problems such as bulky hardware components for modulation and low compatibility due to a change in the number of base station sectors and the number of antennas, that is, a time division multiplexing method is fully used to decrease reliance on the hardware components, and a sector beam selector and a TX beam former are used to be compatible with a conventional base station system without separate hardware components, for example, one hardware component allows a smart antenna base station system of 3 sectors and 8 antennas to be readily compatible with a conventional base station system of 3 sectors and 2 antennas or 6 sectors and 2 antennas.  
         [0009]     To achieve the above purposes, one aspect of the present invention provides an apparatus for modulation in a base station with a smart antenna, the apparatus comprising: a multiplexing modulator having a time division multiplexing structure; a plurality of non-multiplexing modulators which does not have the time division multiplexing structure; a channel adder adding outputs of the plurality of non-multiplexing modulators; a sector beam selector outputting a plurality of beam signals, wherein each beam signal is a signal obtained by adding a signal of the multiplexing modulator, which is accumulated during a multiplexing period after controlling each output signal to be turned on/off, to each output signal of the channel adder, which is controlled to be turned on/off, or a signal accumulated during the multiplexing period after controlling the outputs of the multiplexing modulator to be turned on/off; and a TX beam former outputting a plurality of antenna signals to a plurality of antennas, wherein each antenna signal is a signal obtained by adding the plurality of beam signals after being multiplied with a plurality of weights. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail preferred embodiments thereof with reference to the attached drawings in which:  
         [0011]      FIG. 1  is a view illustrating an apparatus for modulation in a base station with a smart antenna according to an embodiment of the present invention;  
         [0012]      FIG. 2  is a view illustrating a detailed structure of the channel selector in  FIG. 1 ;  
         [0013]      FIG. 3  is a view illustrating a detailed structure of the sector beam selector in  FIG. 1 ; and  
         [0014]      FIG. 4  is a view illustrating a detailed structure of the TX beam former in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.  
         [0016]     According to the present invention, an apparatus for modulation in a base station with a smart antenna has developed to meet a WCDMA specification employed in 3 rd  generation partnership project (3GPP), but may be applied to a CDMA2000 employed in 3GPP2 or a specification employed in 4 th  generation partnership project (4GPP) or the like which is being currently developed.  
         [0017]     In the present invention, a smart antenna system will be described by way of example, which requires parameters as follows: 3 sectors, 12 beams per sector, and 8 antennas per sector. Further, in a base station system, it is important to accept a plurality of subscribes at one channel card in order to secure realization efficiency and saving of expenses, therefore the base station system will be described by way of example, which comprises a DPCH of 32 channels and a dedicated S-CPICH of 32 channels.  
         [0018]      FIG. 1  is a view illustrating an apparatus for modulation in a base station with a smart antenna according to an embodiment of the present invention.  
         [0019]     Referring to  FIG. 1 , a digital signal processor (DSP)  40  controls a smart antenna base station modulator  10  through a storage/read register, and provides input data to be modulated by TrCH modulators  100 ,  101 ,  102  and  103  via an external memory  30 . The smart antenna base station modulator  10  is composed of 32-channel TrCH modulators  100 ,  101 ,  102  and  103 ; 32-channel S-CPICH modulators  110 ,  111 ,  112  and  113 ; a P-CPICH modulator  120 ; an SCH modulator  130 ; an AICH modulator  140 ; an AP-AICH modulator  150 , a CD/CA-ICH modulator  160 ; a PICH modulator  170 ; a channel adder  180 ; a sector beam selector  200 ; and a TX beam former  300 . The smart antenna base station modulator  10  outputs signals to three sectors of eight antennas  60 ,  70  and  80  via an analog radio frequency (RF) transmitting filter  50 .  
         [0020]     The TrCH modulator  100  performs modulation of TrCH encoding channels among forward link channels, that is, DPCH, P-CCPCH, S-CCPCH, and PDSCH. Here, the highest speed of clock to be processed in the TrCH modulator  100  is a chip speed clock (CHIPX 1 ), so that a clock (CHIPX 8 ) that is eight times faster than the chip speed is used for time division multiplexing. Hence, eight channels are processed by the minimum hardware at the same time. As shown in  FIG. 1 , when four TrCH modulators are connected in parallel, it is possible to process the maximum thirty-two independent channels. The TrCH modulators  100 ,  101 ,  102  and  103  each having eight channels output signals SYM 0 , SYM 1 , SYM 2  and SYM 3 , respectively. In four signals SYM 0 , SYM 1 , SYM 2  and SYM 3 , signals of antenna 0  and antenna 1  resulted from STTD encoding are combined with signals of I-channel and Q-channel each corresponding to the antenna 0  and antenna 1  in a bus form. Here, like a period of the CHIPX 1 , a period for which time division multiplexing is performed is called a multiplexing period. Further, like the TrCH modulator  100 , a modulator performing the time division multiplexing is called a multiplexing modulator. Contrarily, a modulator that does not perform the time division multiplexing is called a non-multiplexing modulator.  
         [0021]     The S-CPICH modulator  110  is a block used for processing the dedicated S-CPICH. Like the TrCH modulator  100 , one block of the S-CPICH modulator  110  uses the CHIPX 8  for the time division multiplexing, thereby processing eight channels. Hence, when four S-CPICH modulators  110  are connected in parallel, it is possible to process maximum thirty-two independent S-CPICH channels. Thirty-two S-CPICH channels of four S-CPICH modulators  110 ,  111 ,  112  and  113  output signals SCPI 0 , SCPI 1 , SCPI 2  and SCPI 3 , respectively. In four signals SCPI 0 , SCPI 1 , SCPI 2  and SCPI 3 , the signals of the antenna 0  and antenna 1  resulted from STTD encoding are combined in a bus form with the signals of the I-channel and Q-channel each corresponding to the antenna 0  and antenna 1 .  
         [0022]     The P-CPICH modulator  120  performs modulation in the forward link channel such as the P-CPICH. The SCH modulator  130  performs modulation in the P-SCH and the S-SCH. The AICH modulator  140  performs modulation in the AICH. The AP-AICH modulator  150  performs modulation in the AP-AICH. The CD/CA-ICH modulator  160  performs modulation in the CD/CA-ICH. The PICH modulator  170  performs modulation in the PICH. Here, detailed inner structures and functions of these modulator blocks are not claimed, and therefore descriptions thereof will be omitted.  
         [0023]     The P-CPICH modulator  120 , the SCH modulator  130 , the AICH modulator  140 , the AP-AICH modulator  150 , the CD/CA-ICH modulator  160 , the PICH modulator  170  output signals corresponding to the antenna 0  and the antenna 1  at a speed of spreading factor  256  (SF 256 ), and each antenna output value is a complex number of the I-channel and the Q-channel, which is inputted to the channel adder  180 .  
         [0024]      FIG. 2  is a view illustrating a detailed structure of the channel adder  180  in  FIG. 1 .  
         [0025]     Referring to  FIG. 2 , P-CPICH_A 0  and P-CPICH_A 0  outputted from the P-CPICH modulator  120 , SCH_A 0  and SCH_A 1  outputted from the SCH modulator  130 , AICH_A 0  and AICH-A 1  outputted from the AICH modulator  140 , AP-AICH_A 0  and AP-AICH_A 1  outputted from the AP-AICH modulator  150 , CD/CA-ICH_A 0  and CD/CA-ICH_A 1  outputted from the CD/CA-ICH modulator  160 , and PICH_A 0  and PICH_A 1  outputted from the PICH modulator  170  are divided according to the antennas. In the case of the antenna 0 , they are multiplexed by a multiplexer  181  at a speed of the CHIPX 8  and are outputted, and sequentially added by an accumulator composed of an adder and a register  182  at the speed of the CHIPX 8 . The accumulated value is stored by a register  183  at the speed of the CHIPX 1 , thereby allowing the channel adder of the antenna 0  to create N_A 0 . Actually, this value is a complex number including values of the I-channel and the Q-channel. Likewise, in the case of the antenna 1 , they are multiplexed by a multiplexer  184  and accumulated by an accumulator composed of an adder and a register  185 , and the accumulated value is stored by a register  186  at the speed of CHIPX 1 , thereby allowing the channel adder of the antenna 1  to create N_A 1 .  
         [0026]      FIG. 3  is a view illustrating a detailed structure of the sector beam selector  200  in  FIG. 1 .  
         [0027]     As shown in  FIG. 3 , the sector beam selector  200  performs an on/off function by selecting sectors and beams, each of which must be transmitted for total thirty-two channels of four TrCH modulators (SYM 0 , SYM 1 , SYM 2 , SYM 3 ), total thirty-two channels of four S-CPICH modulators (SCPI 0 , SCPI 1 , SCPI 2 , SCPI 3 ), and the outputs (N_A 0 , N_A 1 ) of the channel adder, and performs a function of adding the on/off controlled channel values according to the selected sectors and beams.  
         [0028]     Each output of the thirty-two channels of four TrCH modulators and each output of the thirty-two channels of four S-CPICH modulators is inputted to a common beam selector and all beam selectors with respect to all sectors, and the DSP stores on/off control values in an on/off register  280  with respect to each output of the channels, thereby flexibly controlling the output of the random channel to be transmitted to any beam of any sector.  
         [0029]     When the DPCH channel of the forward link is set, at the beginning, the DPCH channel of the reverse link is not set and therefore it is impossible to know a direction of a terminal, thereby transmitting the output of the corresponding DPCH channel to the common beam. This is implemented by the DSP, wherein the DSP controls the on/off value of the on/off register  280  corresponding to the common beam selector  250 . After the forward link DPCH channel is set to the common beam, the reverse link DPCH is synchronized. After the reverse link beam is formed by a receiver, the channel setting is changed from the common beam selector to a beam selector # 0  through a beam selector # 11 .  
         [0030]     The sector beam selector  200  is composed of three sector selectors  210 ,  260  and  270 , and the on/off register  280  to control the DSP, wherein each sector selector is composed of twelve beam selectors from the beam selector# 0  to the beam selector# 11 , and the common beam selector  250 .  
         [0031]     Each of the time division multiplexed output values SYM 0 , SYM 1 , SYM 2 , SYM 3 , SCPI 0 , SCPI 1 , SCPI 2  and SCPI 3  from eight channels to be inputted to the beam selector# 0 , which are combined by the TrCH modulator and S-CPICH modulator as the bus, is divided into values of the antenna 0  and the antenna 1 . The divided values have a complex value of the I-channel and the Q-channel. An on/off controller  231  controls each of sixteen inputs SYM 0 _A 0 , SYM 0 _A 1 , SYM 1 _A 0 , SYM 1 _A 1 , SYM 2 _A 0 , SYM 2 _A 1 , SYM 3 _A 0 , SYM 3 _A 1 , SCPI 0 _A 0 , SCPI 0 _A 1 , SCPI 1 _A 0 , SCPI 1 _A 1 , SCPI 2 _A 0 , SCPI 2 _A 1 , SCPI 3 _A 0 , and SCPI 3 _A 1  to be turned on/off. Here, these sixteen inputs are time division multiplexed at the speed of CHIPX 8 , so that the on/off-controlled channel values are added by a parallel adder  232 . The outputs of the parallel adder  232  are accumulated by the accumulator composed of the adder and the register  233  at the speed of CHIPX 8 , and updated by the register  234  at the speed of CHIPX 1 , thereby creating S 0 _B 0  (sector 0 , beam 0 ). Likewise, the other eleven beam selectors are operated to create S 0 _B 1 , S 0 _B 2 , . . . , S 0 _B 11 . Likewise, the sector selector# 1   260  and the sector selector# 2   270  are operated to create S 1 _B 0 , S 1 _B 1 , . . . , S 1 _B 11 , S 2 _B 0 , S 2 _B 1 , . . . , S 2 _B 11 .  
         [0032]     Eight signals of the common beam selector  250  in the sector selector# 0   210 , that is, SYM 0 _A 0 , SYM 1 _A 0 , SYM 2 _A 0 , SYM 3 _A 0 , SCPI 0 _A 0 , SCPI 1 _A 0 , SCPI 2 _A 0  and SCPI 3 _A 0  are inputted to an on/off controller  251  to be turned on/off. The eight outputs of the on/off controller  251  are added by a parallel adder  252 . Then the added outputs are accumulated by the accumulator composed of the adder and the register  253  at the speed of CHIPX 8 , and updated by the register  254  at the speed of CHIPX 1 . The updated values are added, to an output N_A 0  of the channel adder controlled by an on/off controller  256 , by an adder  255 , thereby creating S 0 _CA 0  (sector 0 , common beam, antenna 0 ). Likewise, S 0 _CA 1  (sector 0 , common beam, antenna 1 ) is created from eight signals SYM 0 _A 1  SYM 1 _A 1 , SYM 2 _A 1 , SYM 3 _A 1 , SCPI 0 _A 1 , SCPI 1 _A 1 , SCPI 2 _A 1 , and SCPI 3 _A 1  and output N_A 1 . Likewise, the common beam selectors in the sector selector# 1   260  and the sector selector# 2   270  are operated to create S 1 _CA 0 , S 1 _CA 1 , . . . , S 1 _CA 11 , S 2 _CA 0 , S 2 _CA 1 , . . . , S 2 _CA 11 .  
         [0033]      FIG. 4  is a view illustrating a detailed structure of the TX beam former  300  in  FIG. 1 .  
         [0034]     Referring to  FIG. 4 , the TX beam former  300  forms beams according to the sectors and performs an output interface with a weight calculated by the DSP  40  and provided through a weight register  350 .  
         [0035]     The TX beam former  300  employs the following time division multiplexing method to use the minimum hardware. The outputs of the sector beam selector inputted to the TX beam former  300  are multiplexed by a beam multiplexer  310  into two groups every three sectors, thereby creating a 00  and a 01  for the sector 0 , a 10  and all for the sector 1 , a 20  and a 21  for the sector  2 . For instance, in the case of a 00  and a 01  for the sector 0 , a 00  is multiplexed into seven values S 0 _B 0 , S 0 _B 2 , . . . , S 0 _B 10 , S 0 _CA 0  in sequence at the speed of CHIPX 8 , and a 01  is multiplexed into seven values S 0 _B 1 , S 0 _B 3 , . . . , S 0 _B 11 , S 0 _CA 1  in sequence at the speed of CHIPX 8 . The DSP  40  stores a weight of each antenna according to the sectors and beams in the weight register  350 , so that the output g 00  of the weight register  350  is outputted by multiplexing a weight according to each of the beams of the sector 0  and antenna 0  at the speed of the CHIPX 8 , depending on the multiplexing sequence of a 00  and a 01 . Likewise, a weight according to each of the sectors, beams and antennas is multiplexed at the speed of the CHIPX 8 , thereby outputting g 00 , g 01 , . . . , g 07 , g 10 , g 11 , . . . , g 17 , g 20 , g 21 , . . . , g 27 .  
         [0036]     A sector 0 _beam former  320  is composed of eight sub-blocks such as an antenna 0 _beam former  330 , an antenna 1 _beam former, . . . an antenna 7 _beam former  330 . The antenna 0 _beam former  330  receives the outputs a 00  and a 01  corresponding to the sector 0  and the weight g 00  of the weight register corresponding to the sector 0  and antenna 0  among the outputs of the beam multiplexer  310 . The outputs a 00  and a 01  are the complex numbers and are complex-multiplied with the weight g 00  by complex multipliers  331  and  338 . The outputs of the complex multipliers are accumulated by the accumulator composed of the adder and the register  332 ,  339  at the speed of CHIPX 8 , and then added by an adder  333 .  
         [0037]     In the apparatus for modulation in the base station with the smart antennas, the output of the final adder  333  is 15 bits. By the way, in consideration of three sectors, eight antennas, and the I- and Q-channels, total output is 720 bits which is too large to realize the system. To solve this problem within the given clocks, a parity check  334  of 1 bit is added to a top of the adder output of 15 bits and then stored in the register  335  at the speed of CHIPX 1 . Then, the output is parallel-serial converted  336  and  337  according to whether the bit is odd or even, thereby being converted into a complex value S 0 _A 0  of 2 bits. Thus, after performing the output interface, the final output of the base station modulator is total 96 bits because 2 bits are given to the I- and Q-channels, three sectors, and eight antennas.  
         [0038]     Likewise, the antenna 1 _beam former, the antenna 2 _beam former, the antenna 3 _beam former, the antenna 4 _beam former, the antenna 5 _beam former, the antenna 6 _beam former and the antenna 7 _beam former are operated to create S 0 _A 1 , S 0 _A 2 , S 0 _A 3 , S 0 _A 4 , S 0 _A 5 , S 0 _A 6  and S 0 _A 7  as to the outputs of the sector 0 . Like the sector 0 _beam former  320 , the sector 1 _beam former  340  and the sector 2 _beam former  360  are operated to create S 1 _A 0 , S 1 _A 2 , . . . , S 1 _A 7 , and S 2 _A 0 , S 2 _A 1 , S 2 _A 7 , respectively.  
         [0039]     As described above, the present invention provides a simple apparatus for modulation.  
         [0040]     Further, the present invention provides an apparatus for modulation in a base station with a smart antenna, which has good compatibility regardless of a change in the number of base station sectors and the number of antennas.  
         [0041]     While the present invention has been described with reference to a particular embodiment, it is understood that the disclosure has been made for purpose of illustrating the invention by way of examples and is not limited to limit the scope of the invention. And one skilled in the art can make amend and change the present invention without departing from the scope and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.