Title of Invention

"AN OPTICAL REPEATING APPARATUS USING DAIZY CHAIN METHOD AND THE METHOD FOR THE SAME"

Abstract

Optical repeater using daizy chain method and the method for the same of the present invention is capable of reducing cost for extending of optical cable without being affected by size and temperature of the optical cable connecting the respective optical repeaters 400 and base station 600 and noise due to an optic module (E/O converter 500 and O/E converter 480) by transmitting the RF digital signal outputted from the last optical repeater 400 and base station 600 after converting the RF analog signal received from the plurality of optical repeaters 400 by the daizy chain method to the base band digital signal. Also, a method for optical repeater by the daizy chain method includes the steps of summing a converted base band digital signal and base band digital signal transmitted from the former stage, transmitting the summed base band digital signal to a base station and demodulating the received base band digital signal by the base station.

Full Text

BACKGROUND OF THE INVENTION 1. Field of Invention The present invention relates to an optical repeating apparatus using daizy chain method and the method for the same, and, in general, it pertains to an optical communication system and outputted from a last optical repeater after summing respective baseband digital signals of a plurality of optical repeaters connected by the daizy chain method. 2. Description of the Background Art In the past, Digital Cellular and Personal Communication Service mobile communication entrepreneurs had to extend base stations to extend speech area and increase extent of wireless communication net. However, since in extension of base station, much cost and installing time are needed, recently, mobile communication entrepreneurs who invested much in early extension of base station are trying to build optical repeaters rather than extending base station, to extend speech area and service extent by installing repeaters which are methods for obtaining various effects in cost and installing time with a small investment. Since a repeater system reamplifies and transmits signals in regions where reception of a terminal is impossible due to week strength of frequency (underground space, underground shopping district, tunnel, underground of a 1A building, indoor of a building and the like), a user can receive excellent service quality. A major principle of the repeater is that a radio frequency (RF) signal of a base station is reproduced as a RF signal again by transmitting the signal to a preferable remote position through a third transmitting medium. The RF signal is a general broadband spectrum having the extent of the frequency from 10KHz to 100KHz and the extent of the frequency is basic frequency in electromagnetic wave communication. The repeaters include to an optical repeater, frequency converting repeater, microwave (M/W) repeater, laser repeater and the like and further include an interference canceller for preventing oscillation which is an electric vibration generated by a phase control circuit inside the repeater, without any change of the signal. Among the above kinds of repeaters, an optical repeater is an apparatus which has the remote antenna function as an antenna attached to a base station by processing signals inputted/outputted through the remote antenna positioned away from the base station. Also, the above optical repeater is a diversity transmitting amplifying apparatus for extending of the service area and canceling a shadow area by transmitting a wave between a base station and moving station in a wireless communication service region using the Code Division Multiple Access (CDMA) method. When a converted RF optical signal is transmitted through an optical cable after converting the inputted RF electric signal to the RF optical signal, the signal can be transmitted to the shadow area, thus to cancel shadow, extend the service area and design a net having a separated capacity and coverage. Such optical repeater includes a donor portion for processing a baseband of a base station and 2 interface of the optical signal and a remote portion which is an interface portion of the optical cable and wireless RF signal. In the optical repeater, a process of receiving an analog signal generated in the base station, digitalizing the signal in the donor portion, calculating, processing and then transmitting the result to the remote portion is very important for overcoming attenuation generated in transmitting an optical signal. In case the signal modulated to the RF optical signal is a digital signal, the digital signal is not affected by the maximum attenuation of 35dB allowed in an optical signal transmitting module very much and is not affected by a signal to noise ratio (SNR) or an InterModulation Distortion (IMD). Figure 1 is a block diagram showing a conventional optical communication system including an analog optical repeater. As shown in Figure 1, the above optical communication system includes a plurality (1-N) of analog optical repeater 200 and a CDMA master base station 300 connected with the optical repeater 200 by optical cables respectively and the optical repeater 200 includes an antenna 210 for receiving the RF analog signal, a low noise tuning amplifier 220 for reducing internal noise, controlling the amplifying gain randomly and amplifying the RF analog signal, an Electrical signal to Optical signal (E/O) converter 230 for converting the RF electric analog signal to the RF optical signal. Also, the CDMA master base station 300 includes an optical combiner 310 for summing the RF optical signals transmitted from optical repeaters an Optical signal to Electrical signal (O/E) converter 320 for converting the RF analog optical signal to the RF analog electrical signal, a band-pass filter (BPF) 330 for filtering the RF analog signal to a RF band determined in the optical repeater 200, an 3 amplifier 340 for amplifying the RF signal received from the BPF 330, a Frequency converter 350 for converting the RF analog received from the amplifier 340 to a baseband digital signal, a CDMA modem 370 for performing demodulation by receiving the baseband digital signal outputted from the Frequency converter 350 and an auto gain control (AGC) circuit 360 for controlling an amplifying gain of the amplifier 340. And the Frequency converter 350 includes a Mixer(not shown) for converting RF analog signal into baseband analog signal and an analog signal to digital signal(A/D) converter(not shown) for converting a baseband analog signal received from the Mixer(not shown) to a baseband digital signal. The process for signal processing in an optical communication system including a conventional analog optical repeater will be described with reference to Figure 1. The antenna 210 of the optical repeater 200 receives and transmits the RF analog electrical signal, namely, an Arf_1(t) to the low noise tuning amplifier 220. The low noise tuning amplifier 220 transmits the RF analog electrical signal having lower noise level to the E/O converter 230 after the low noise tuning amplifier 220 maintains the RF signal (received by lowering the noise level of the whole system) at a low noise level. The E/O converter 230 transmits the converted RF analog optical signal to the optical combiner 310 of the CDMA master base station 300 through an optical cable after converting the received RF analog electrical signal to the RF analog optical signal. The Optical combiner 310 transmits summed RF analog optical signals to the O/E converter 320 after summing all of received RF analog optical signals. The O/E converter transmits converted RF analog electrical signals, namely, the 4 Arf_m(t) to the BPF 330 after converting the received RF analog optical signal to the RF analog electrical signal. The BPF 330 filters the size of the received RF analog electrical signal Arf_m(t) and then transmits the filtered RF signal to the amplifier 340. The amplifier 340 amplifies the received RF analog electrical signal to have a predetermined gain and transmits the amplified RF analog electrical signal to a Mixer(not shown) of the Frequency converter 350 and the Mixer converts the RF analog signal into the baseband analog signal and transmits baseband analog signal to a A/D converter(not shown). The A/D converter converts the baseband analog signal received from the Mixer(not shown) into the baseband digital analog signal and transmits to a CDMA modem 380. The CDMA modem 380 performs demodulation of the received baseband digital signal. The AGC circuit 360 controls the amplifier 340 to output a certain gain. Therefore, the AGC 360 maintain the size of baseband analog signal inputted the A/D converter(not shown) of the Frequency converter 350. However, in case the RF analog signals received from respective optical repeaters are summed in the CDMA master base station of the optical communication system including conventional analog optical repeater, there occurs a problem that signal transmission loss and signal delay characteristics are respectively different due to the size and temperature of the optical cable connecting the optical repeater and the CDMA master base station therefore an additional circuit for preventing transmission loss according to temperature of the optical cable is needed. When the RF analog signals received from respective optical repeaters are optically combined in the CDMA master base station, the size of the RF 5 analog signal must be adjusted using the low noise tuning amplifier of the optical repeater to obtain transmission signals of respective optical repeaters to make the transmission signals of respective optical repeaters transmitted to the CDMA master base station to have the same size. The output signal which passed through the O/E converter after being optically combined in the CDMA master base station, namely, the Arf_m(t) becomes to obtain received noise characteristic of the worst optical repeater among N optical repeaters and an additional circuit is necessary to have identical round trip time of respective optical repeaters. Also, much cost for building the optical cable is required since the respective optical repeater and CDMA master base station are connected by different optical cables respectively. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical repeater using daizy chain method and the method for the same capable of reducing cost for extending of optical cable without being affected by size and temperature of the optical cable connecting the respective optical repeaters and base station and noise according to an optic module (E/O converter and O/E converter) by transmitting the baseband digital signal outputted from the last optical repeater to the base station after converting the RF analog signal received from the plurality (1~N) optical repeaters connected each other by the daizy chain method into the baseband digital signal. To achieve these and other advantages and in accordance with the' purpose of the present invention, as embodied and broadly described herein, 6 there is provided an optical repeating apparatus, using daizy chain method, said apparatus comprising: a plurality of optical repeaters for converting a radio frequency analog signal inputted to an antenna to a baseband digital signal, summing the converted baseband digital signal and a baseband digital signal transmitted from a previous stage, and transmitting the summed signal to the next stage; and a base station for receiving and demodulating an output signal of the last optical repeater. Also, a method for optical repeater by the daizy chain method includes the steps of summing the converted baseband digital signal(converting a radio frequency analog signal inputted to an antenna to a baseband digital signal) and a baseband digital signal transmitted from a previous stage, and transmitting the summed signal to a base station and demodulating the received baseband digital signal by the base station. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: Figure 1 is a block diagram showing a conventional optical communication system including an analog optical repeater; and Figure 2 is an optical communication system including a digital optical repeater connected by the daizy chain method in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings Figure 2 is an optical communication system including a digita optical repeater connected by the daizy chain method in accordance with the present invention. As shown in Figure 2, an optical communication system in accordance with the present invention includes a plurality (1~N) of digital optical repeaters 400 for converting the RF analog signal to a baseband digital signal and transmitting the baseband digital signal to the following stage and a CDMA master base station 600 for receiving the baseband digital signal from the last optical repeater. The plurality (1~N) of optical repeaters 400 are connected by the daizy chain method. The daizy chain method is a structure of hardware devices connected consecutively. For example, it is a bus line-connecting method, wherein a device A is connected to a device B and device B is connected to device C consecutively. At this time, the last device is connected mainly to a resistance device or terminal device. The devices can receive identical signals but remarkably different from a simple bus, the devices can adjust one or more signals before transmitting the signal to another devices by respective devices included in the chain. 8 The optical repeater 400 includes an antenna 410 for receiving the RF analog signal, namely, an Arf(t) signal, a low noise tuning amplifier 420 for amplifying the Arf_1(t) signal, the RF analog signal received from the antenna 410, a band-pass filter (BPF) 430 for fitering the RF analog signal received from the low noise tuning amplifier 420 to a determined size of the RF band, an amplifier 440 for amplifying the received RF analog signal passed through BPF 430 to a determined amplifying gain, an Frequency converter 450 for converting the RF analog signal outputted from the amplifier 440 to a baseband digital signal, a digital delay device 470 for delaying the baseband digital signal outputted from the Frequency converter match a round trip time of each optical repeater, an Optical signal to Electric signal digital converter (O/E converter) 480 for converting the baseband digital optical signal received from another remote optical repeater to a baseband digital electrical signal, a digital summer 490 for summing the baseband digital signal outputted from the Frequency converter 450 and the baseband digital signal outputted from the O/E converter 480 and an Electric signal to Optical signal digital converter (E/O converter) 500 for converting the baseband digital electrical signal outputted from digital summer 490 to a baseband digital optical signal and an auto gain control (AGC) circuit 460 for controlling the gain of the amplifier 440 to maintain the gain of the amplifier 440 uniformly. The CDMA master station 600 includes an Optical signal to Electric signal digital converter (O/E converter) 610 for converting the baseband digital optical signal received from the E/O converter 500 of the optical repeater 400 through the optical cable into a baseband digital electrical signal and a CDMA modem 620 for performing demodulation by receiving the baesband signal transmitted from the O/E converter 610. 9 A Mixer(not shown) of the Frequency converter 450 converts the RF analog signal received from amplifier 440 to a baseband analog signal. An A/D converter(not shown) converts baseband analog signal received from the Mixer(not shown) to a baseband digital signal and trasmits the baseband digital signal, namely Abs_1(t) to the digital delay device 470. The process of signal processing in an optical communication system including a digital optical repeater by the daizy chin method in accordance with the present invention will be described with reference to Figure 2. The antenna 410 of the optical repeater 400 receives a RF analog signal, namely, an Arf_1(t) and transmits the signal to the low noise tuning amplifier 420. The low noise tuning amplifier 420 maintains the high frequency RF signal (received by lowering the noise level of the whole system) at a low noise level and transmits the RF signal having the lowered noise level to the BPF 430. The BPF 430 filters the received RF analog signal and transmits the fitered RF analog signal to the amplifier 440. The amplifier 440 amplifies the received RF analog signal using a certain gain and transmits the amplified RF analog signal to the Frequency converter 450. An Mixer(not shown) of the Frequency converter 450 converts RF analog signal received from amplifier 440 to a basaband analog signal. An A/D converter(not shown) converts baseband analog signal received from the Mixer(not shown) to a basaband digital signal and transmits the baseband digital signal, namely Abs_1(t) to the digital delay device 470. The digital delay device 470 delays the received baseband digital signal to match the round trip time of another respective optical repeaters and transmits the delayed baseband digital signal, namely, an Abs_1(t-t1) to the digital summer 490. 10 Also, the O/E converter 500 receives the baseband digital optical signal transmitted from another optical repeater, converts the received baseband digital optical signal to a baseband digital electrical signal and transmits the signal to the digital summer 490. The digital summer 490 sums the Abs_1(t-t1) signal received from the digital delay device 470 and the baseband digital signal received from the O/E converter 480 and transmits the summed signal to the E/O converter 500. The E/O converter 500 converts the received baseband digital electrical signal to a baseband digital optical signal and then converted baseband digital optical signal is transmitted to the Nth optical repeater, namely, the final remote optical repeater repeating the process of inputting the signal to another optical repeater. The baseband digital optical signal outputted from the final optical repeater is transmitted to the O/E converter 610 of the CDMA master base station 600 through the optical cable. The O/E converter 610 converts the received baseband digital optical signal to a baseband digital electrical signal and transmits the signal to the CDMA modem 620. The CDMA modem 620 demodulates the received baseband digital signal. As described above, the present invention can reduce the cost of building of the optical cable and minimize transmission loss due to the transmission size and temperature of the optical cable by converting the RF analog signal inputted in the optical repeater to a baseband digital signal, connecting the plurality of optical repeater by the daizy chain method, summing the baseband digital signal of respective optical repeaters and transmitting the outputted result to a base station. Even if a transmission loss is generated due to the transmission length and temperature of the optical cable, in the present invention, an additional circuit compensating for the loss is not necessary and the length of the optical cable 11 capable of restoring the digital signal affected by the transmission loss is wider than the diameter of the cell of the conventional remote optical repeater. Also, with the present invention, different from the conventional method, the RF signal is not affected by the received noise characteristic of the worst remote optical repeater among the plurality of optical repeaters and by the E/O converter, O/E converter and the noise generated in the optical cable. Also, there are further advantages that with the present invention, accurate controlling of the digital delay device for matching the round trip delay of respective repeaters can be easily performed and there is no tolerance. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalence of such meets and bounds are therefore intended to be embraced by the appended claims. s v 12 WE CLAIM: 1 An optical repeating apparatus, using daizy chain method, said apparatus comprising: a plurality of optical repeaters for converting a radio frequency analog signal inputted to an antenna to a baseband digital signal, summing the converted baseband digital signal and a baseband digital signal transmitted from a previous stage, and transmitting the summed signal to the next stage; and a base station for receiving and demodulating an output signal of the last optical repeater. 2 The apparatus as claimed in claim 1, wherein the optical repeater comprises: a band-pass filter (BPF) for filtering the received RF analog signal; an amplifier for amplifying the filtered RF analog signal; a frequency converter for converting the amplified RF analog signal to a baseband digital signal: a digital delay device for delaying the converted basebad digital signal; an Optical signal to Electrical signal digital converter (O/E converter) for converting the baseband digital optical signal received from another optical repeater to a baseband digital electrical signal:; a digital summer for summing the baseband digital signal outputted from the frequency converter and the baseband digital signal outputted from the O/E converter; an Electrical signal to Optical signal digital converter (E/O converter) for converting an baseband electrical signal outputted from the digital summer to a baseband optical signal; and 13 an auto gain control (AGC) circuit for controlling the amplifying gain of the amplifier. 3. The apparatus as claimed in claim 2, wherein the digital delay device is adapted to delay the baseband signal to match a round trip time of each optical repeater. 4. The apparatus as claimed in claim. 2, wherein the AGC circuit is adapted to control the amplifier to have a uniform amplifying gain for maintaining the size of the signal inputted to the frequency converter uniformly. 5. The apparatus as claimed in claim 2, wherein the O/E converter is adapted to receive the baseband digital optical signal transmitted from another optical repeater. 6. The apparatus as claimed in claim 1, wherein the optical repeater is connected with another optical repeater by an optical cable. 7. The apparatus as claimed in claim 1, wherein the optical repeater is connected with the base station by an optical cable. 8. The apparatus as claimed in claim 1, wherein the optical repeater is connected with another optical repeater by the daizy chain method. 9. An optical repeating method by the daizy chain method, comprising the steps of: summing the converted baseband digital signal (converting a radio 14 frequency analog signal inputted to an antenna to a baseband digital signal) and a baseband digital signal transmitted from a previous stage, and transmitting the summed signal to a base station; and demodulating the received baseband digital signal by the base station. 10. The method as claimed in claim 9, wherein the transmitting process comprises the steps of: converting a RF analog signal transmitted from the antenna to a basebad digital signal in an frequency converter; delaying the converted-baseband digital signal converted in the digital delay device; and summing the delayed baseband digital signal and the baseband digital signal transmitted from another optical repeater and transmitting the summed signals to the base station. 11. The method as claimed in claim 10, wherein the frequency converter receives input signals with a certain size by being amplified to a certain amplifying gain in an amplifier. 12. The method as claimed in claim 11, wherein the amplifier is controlled by an AGC circuit to maintain a certain amplifying gain. 13. The method as claimed in claim 10, wherein the digital delay device delays the baseband digital signal to match a round trip time with another optical repeaters. 15 14. The method as claimed in claim 10, wherein the number of the optical repeater is plural. 15. The method as claimed in claim 9, wherein the baseband digital signal is continuously summed by baseband digital signals of another optical repeaters. 16. The method as claimed in claim 9, wherein the base station receives the baseband digital optical signal outputted from a last optical repeater. 17. The method as claimed in claim 10 wherein the optical repeater is connected with another optical repeater by an optical cable. 18. The method as claimed in claim 10, wherein the optical repeater is connected with the base station by an optical cable. 19. The method as claimed in claim 10, wherein the optical repeater is connected with another optical repeater by the daizy chain method. 20. An optical repeating method by the daizy chain method, comprising the steps of: amplifying a RF analog signal inputted through an antenna in an amplifier; converting the RF amplified analog signal to a baseband digital signal in the A/D converter; delaying the converted baseband digital signal in a digital delay device; 16 summing the delayed baseband digital signal and a baseband digital signal transmitted from another optical repeater in a digital summer and transmitting the summed baseband digital signal to a base station; and demodulating the baseband digital signal in the base station. 21. The method as claimed in claim 20, wherein the amplifier amplifies the received RF analog signal to a certain amplifying gain to maintain the size of the RF analog signal inputted to the A/D converter uniformly. 22. The method as claimed in claim 21, wherein the amplifier is controlled by an AGC circuit to maintain a certain amplifying gain. 23. The method as claimed in claim 20, wherein the digital delay device delays the received baseband digital signal received to match a round trip time with baseband digital signals inputted from another optical repeaters. 24. The method as claimed in claim 20, wherein the base station receives the baseband digital optical signal outputted from a last optical repeater. 25. The method as claimed in claim 20, wherein the optical repeater is connected with another optical repeater by an optical cable. 26. The method as claimed in claim 20, wherein the optical repeater is connected with the base station by an optical cable. 17 27. The method as claimed in claim 20, wherein the optical repeater is connected with another optical repeater by the daizy chain method. 18 28. An optical repeating apparatus, substantially as herein described, particularly with reference to the accompanying drawings. Optical repeater using daizy chain method and the method for the same of the present invention is capable of reducing cost for extending of optical cable without being affected by size and temperature of the optical cable connecting the respective optical repeaters 400 and base station 600 and noise due to an optic module (E/O converter 500 and O/E converter 480) by transmitting the RF digital signal outputted from the last optical repeater 400 and base station 600 after converting the RF analog signal received from the plurality of optical repeaters 400 by the daizy chain method to the base band digital signal. Also, a method for optical repeater by the daizy chain method includes the steps of summing a converted base band digital signal and base band digital signal transmitted from the former stage, transmitting the summed base band digital signal to a base station and demodulating the received base band digital signal by the base station.

Documents:

00713-cal-2001-abstract.pdf

00713-cal-2001-claims.pdf

00713-cal-2001-correspondence.pdf

00713-cal-2001-description(complete).pdf

00713-cal-2001-drawings.pdf

00713-cal-2001-form-1.pdf

00713-cal-2001-form-18.pdf

00713-cal-2001-form-2.pdf

00713-cal-2001-form-3.pdf

00713-cal-2001-form-5.pdf

00713-cal-2001-g.p.a.pdf

00713-cal-2001-letters patent.pdf

00713-cal-2001-priority document others.pdf

00713-cal-2001-priority document.pdf

00713-cal-2001-reply f.e.r.pdf

713-CAL-2001-(17-11-2011)-CERTIFIED COPIES(OTHER COUNTRIES).pdf

713-CAL-2001-(17-11-2011)-CORRESPONDENCE.pdf

713-CAL-2001-(17-11-2011)-PA-CERTIFIED COPIES.pdf

713-CAL-2001-(22-08-2012)-CORRESPONDENCE.pdf

713-CAL-2001-(22-08-2012)-OTHERS.pdf

713-CAL-2001-(22-08-2012)-PA-CERTIFIED COPIES.pdf

713-CAL-2001-FORM-27-1.pdf

713-CAL-2001-FORM-27.pdf