KR100322841B1 - Synchronous signal providing apparatus and its method in microcellular system - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

Synchronization signal supply apparatus and method in a microcellular system.

2. The technical problem to be solved by the invention

In microcellular system, it is effective to provide synchronization signal to small base station to improve capacity and performance of whole system.

3. Summary of Solution to Invention

It is provided in the central base station controller and synthesizes the reference frequency signal for synchronization of each small base station generated by using the reference frequency tone received through the GPS receiver together with the forward control signal and the CDMA signal of the small base station. Reference frequency transmitting means for transmitting; And reference frequency receiving means for distributing the output of the reference frequency transmitting means received through the transmission network, extracting the reference frequency signal, correcting a phase of the extracted reference frequency signal, and providing the reference frequency signal as a reference frequency signal.

4. Important uses of the invention

It is used to provide a synchronization signal to a small base station in a microcellular system.

Description

SYNCHRONOUS SIGNAL PROVIDING APPARATUS AND ITS METHOD IN MICROCELLULAR SYSTEM}

The present invention relates to a synchronization signal supply apparatus and method for a microcellular system, and more particularly, to a microcellular system based on a subcarrier multiplexing (SCM) transmission method using a hybrid fiber radio network. The present invention relates to a synchronization signal supply device and a method for providing a synchronization signal to each small base station (mBS) miniaturized.

In the conventional base station system, the signal received from the primary and preliminary Global Position System (GPS) antennas is synchronized with the frequency synchronization and the time synchronization with a 10 MHz signal and a 1 pulse per second (PPS) signal from the GPS engine. On the other hand, as the cell is microcelled in the conventional mobile communication system, the base station has been miniaturized, and as the base station has been miniaturized, an asynchronous method is also sought. However, a synchronization scheme for a small base station is essential because a code division multiple access (CDMA) mobile communication system is based on synchronization. On the other hand, when a small base station is configured in an asynchronous manner, there is a difficulty in flexible soft handoff processing, and the performance of the system also depends on its performance.

Accordingly, the present invention devised to solve the problems of the prior art as described above provides a reference frequency and time synchronization information to each small base station from the central base station controller of the microcellular mobile communication system, thereby efficiently synchronizing the small base station. It is an object of the present invention to provide a synchronization signal supply apparatus and a method in a microcellular system that can be tailored, thereby improving the capacity and performance of the overall system.

1 is a schematic diagram of a microcellular system to which the present invention is applied.

2 is an overall block diagram of a synchronization signal supply device according to the present invention;

3 is a detailed block diagram of a reference frequency generator according to the present invention;

4 is a detailed block diagram of a reference frequency receiver according to the present invention;

* Explanation of symbols for the main parts of the drawings

101: central base station controller (mBSC) 102: small base station (mBS)

103: optical transmission network connection 104: GPS antenna

105: digital unit (DU) 106: transmission unit (TU)

107: maintenance unit (MU) 108: subcarrier conversion unit (SCMU)

201: reference frequency generator 202,216: power synthesizer

203,207,217,220: Amplifier 204,218: All-optical converter

205: optical node 206,219: optical / electric converter

208,212,221: Power divider 214: FSK modulator / demodulator

209,210,215,222,223: Band pass filter 211,213: Phase locked loop (PLL)

In accordance with another aspect of the present invention, there is provided a synchronization signal supply apparatus, comprising: a central base station controller and a plurality of small base stations connected to each other via a transmission network. And a reference frequency signal for synchronizing each small base station generated using a reference frequency tone received through a global position system (GPS) receiver with a forward control signal and a CDMA signal of the small base station. Reference frequency transmitting means for transmitting through; And each of the small base stations, and distributes the output of the reference frequency transmitting means received through the transmission network, extracts the reference frequency signal, corrects the phase of the extracted reference frequency signal, and corrects the reference frequency of each functional unit. Characterized in that it comprises a reference frequency receiving means for providing a signal.

In addition, the synchronization signal supply method according to the present invention for achieving the above object, for providing synchronization to each small base station applied to the micro-cellular mobile communication system including a plurality of small base station connected via a central base station controller and a transmission network. A method, comprising: a first step of generating a reference frequency signal for synchronization of each small base station using a reference frequency tone received through a Global Position System (GPS) receiver; A second step of power-synthesizing the generated reference frequency signal together with a forward control signal for controlling the small base station and a forward CDMA signal of a user; Extracting the reference frequency signal from the transmitted signal; And a fourth step of correcting a phase of the extracted reference frequency signal to provide the reference frequency signal.

According to the present invention, a 10 MHz reference frequency signal processed and output by a GPS receiver installed in a conventional base station system is converted or transmitted directly to each small base station through a composite optical transmission network, and each small base station uses the reference frequency signal as the frequency. Try to synchronize the frequency generated by the synthesizer. In this case, the reference frequency signal to be transmitted is selected as a frequency that is not affected by distortion caused by the CDMA signals transmitted together. That is, the reference frequency signal is determined by avoiding the frequency represented by the third order nonlinear distortion of the carrier wave being transmitted. By transmitting the reference frequency to the small base station in this way, it is possible to maintain the frequency synchronization and timing synchronization of the overall system, to enable flexible soft handoff, to achieve the miniaturization of the base station, ultimately the coverage that appears due to the advantages of the microcell As a result of expansion and capacity increase, it is possible to improve frequency resource efficiency and quality of service.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic configuration diagram of a microcellular system to which the present invention is applied, in which 101 is a central base station controller (mBSC), 102 is a small base station (mBS), 103 is an optical transmission network connection, 104 is a GPS antenna, and 105 is A digital unit (DU), 106 denotes a transmission unit (TU), 107 denotes a maintenance unit (MU), and 108 denotes a subcarrier modulation unit (SCMU).

In a microcellular system, a radio base (RF) front-end and a compound optical transmission matching module are placed in a small base station (mBS) 102 in a conventional base station, and a part and a controller corresponding to a digital module are controlled by a central base station controller. (mBSC) 101 to perform centralized control management and dynamic channel allocation.

The transmitting unit 106 of the central base station controller transmits and receives an intermediate frequency (IF) of the CDMA signal, and the received intermediate frequency (IF) signal includes a primary and diversity signal. The digital unit (DU) 105 receives a reference frequency tone of 10 MHz from a GPS antenna and provides the received 10 MHz reference frequency tone to a subcarrier conversion unit (SCMU) 108. Further, control data for controlling the small base station (mBS) 102 is transmitted and received with the maintenance unit (MU) 107.

The maintenance unit (MU) 107 matches the digital unit 105 to frequency control signals for network management, state management of a small base station (mBS), control of a small base station, downloading programs and databases, and gain control. Transmit and receive with the subcarrier conversion unit 108 through a frequency shift keying (FSK) modulation and demodulation scheme.

The subcarrier conversion unit 108 combines the CDMA transmission / reception signal, the reference frequency signal generated using the reference frequency tone, and the control signals, and transmits them through the optical transmission network, and transmits the CDMA signal and the control signal from the signal received through the optical transmission network. Separately, provided to the transfer unit 106 and the maintenance unit 107, respectively.

2 is an overall block diagram of a synchronization signal supply device according to the present invention, in which 201 is a reference frequency generator, 202 and 216 are power synthesizers, 203, 207, 217 and 220 are amplifiers, and 204 and 218 are all-optical converters (E / O), and 205 is optical. Nodes 206 and 219 are opto-electric converters (O / E), 208, 212 and 221 are power dividers, 209, 210, 215, 222 and 223 are band pass filters (BPF), 211 and 213 are phase locked loops (PLL) and 214 are frequency transition keying (FSK) changes. Each demodulator is shown.

The synchronization signal supply apparatus according to the present invention is provided in part at the subcarrier conversion unit (108 in FIG. 1) and the small base station.

The reference frequency tone of 10 MHz output from the digital unit 105 is input to the reference frequency generator 201. The reference frequency generator 201 generates a reference frequency (for example, 100 MHz) for synchronizing the system using a reference frequency tone of 10 MHz. The reference frequency thus generated is combined into one signal in the first power synthesizer 202 together with the CDMA transmission signal input from the transmission unit 106 and the control signal input from the maintenance unit 107. The synthesized signal is amplified by the amplifier 203, and then converted into an optical signal by the pre / optical converter (E / O) 204 and transmitted through the optical path. The signal transmitted through the optical line is branched at the optical node 205 and delivered to each small base station. Here, the optical path may be configured through one optical path when the wavelength division multiplexing method is used, and may be composed of two optical paths when the wavelength division multiplexing method is not used.

The optical signal transmitted to each small base station is converted into an electrical signal through the opto-electric converter (O / E) 206 of the small base station and amplified by the amplifier 207. The signal amplified by the amplifier 207 is divided into a plurality of signals to extract a control signal, a CDMA signal, and a reference frequency signal through the power divider 208 and are input to the respective band pass filters 209, 210, and 215. . The band-filtered control signal is input to the FSK modulator / demodulator 214 and demodulated, and then provided to the control board. The band-filtered CDMA signal is up-converted through an up converter and transmitted to the air through an antenna as a radio frequency (RF) signal. In addition, the band-filtered reference frequency signal is phase-corrected through a phase locked loop (PLL) 211 and input to the power divider 212. One signal distributed by the power divider 212 is phase-corrected again through the phase lock loop 213 and input to the frequency synthesizer used for the FSK modulator / demodulator 214. It is input to frequency synthesizer of up converter and down converter and used as reference frequency. The FSK modulator / demodulator 214 does not require a reference frequency in particular, but requires a reference frequency signal when using another synchronization modem.

Meanwhile, in the reverse transmission, the radio frequency signal received through the antenna is converted into a primary intermediate frequency signal and a diversity intermediate frequency signal through a down converter. In addition, the main intermediate frequency signal, the diversity intermediate frequency signal, and the reverse control signal input through the FSK modulator 214 are combined into one signal through the power synthesizer 216 and amplified by the amplifier 217. . The signal amplified by the amplifier 217 is converted into an optical signal through an electro-optical converter (E / O) 218, and the optical signal is combined with an optical signal of another small base station at the optical node 205 through an optical path. Subcarrier multiplexing unit 108 is transmitted. The signal input through the optical path is converted into an electrical signal through the opto-electric converter 219, and amplified by the amplifier 220. The signal amplified by the amplifier 220 is distributed by the power divider 221 to extract the reverse control signal and the reverse receive intermediate frequency signal, and are input to the respective band pass filters 222 and 223. The reverse control signal filtered by the band pass filter 222 is input to the FSK modulator / demodulator of the maintenance unit and demodulated, and the reverse receiving intermediate frequency filtered by the band pass filter 223 is input to the transmission unit 106. do.

3 is a detailed block diagram of the reference frequency generator of FIG. 2, in which 301 is a divider, 302 is a phase locked loop (PLL), 303 is a band pass filter (BPF), 304 is a variable attenuator, and 305 is a distribution and amplifier. Respectively.

The divider 301 receives a reference frequency of 10 MHz and distributes it, one is distributed and amplified into a plurality of identical signals by the distribution and amplifier 305 for the 10 MHz reference frequency used in the transmission unit 106. In addition, the other 10 MHz reference frequency distributed by the distributor is converted by the phase locked loop (PLL) 302 into the reference frequency (for example, 100 MHz) for synchronization of the small base station. The converted reference frequency is filtered by the band pass filter 303, so that spurious and harmonics are suppressed. In addition, the output of the band pass filter 303 is adjusted by the variable attenuator 304 in consideration of the length characteristics of the transmission line, the number of connected small base stations, and transmitted through the optical transmission network. The phase locked loop 302 should set a reference frequency in consideration of CDMA signals and control signals transmitted in different bands. When transmitting only a single reference frequency, it is possible to directly transmit a reference frequency of 10 MHz depending on the transmission distance and the like, but it is better to avoid it because the optical transmission characteristics of this band are not excellent. If a frequency of 10 MHz is transmitted directly, the phase locked loop 302 of FIG. 3 is not necessary, and the frequency divider 405 of FIG. 4 to be described later is not necessary. On the other hand, since the reference frequency is transmitted, the characteristics of the phase locked loop (PLL), the stability of the frequency, the phase noise, etc. must all be considered so that the transmitted signal can satisfy the characteristics of the reference frequency.

FIG. 4 is a detailed block diagram of the reference frequency receiver according to the present invention, showing in detail only the reference frequency receiver at the front end of the small base station of FIG. In the figure, 401 denotes an optical / electric converter, 402 denotes an amplifier, 403 denotes a bandpass filter, 404 denotes a variable amplifier, 405 denotes a divider, 406 denotes a phase locked loop, and 407 denotes a bandpass filter.

The reference frequency receiver is a part for converting the reference frequency received from the central base station controller back into the reference frequency required by the phase locked loop or the like. For example, the reference frequency transmitted from the central base station controller is 100 MHz, which is converted back to 10 MHz for use in a phase locked loop (PLL).

The optical / electric converter 401 converts the signal received through the optical transmission path into an electrical signal, and the signal converted into the electrical signal is amplified by the low noise amplifier 402. The output of the amplifier 402 is filtered by the bandpass filter 403. The variable amplifier 404 amplifies the signal by adjusting the gain so that the filtered signal is within the operating range of the divider 405 or the prescaler. The amplified signal is divided in frequency by a prescaler or divider 405. At this time, the prescaler or divider 405 should be selected in consideration of phase noise and stability, and generates 10 MHz according to the input frequency. Choose the appropriate one. As mentioned earlier, if the transmitted reference frequency is 100 MHz, the divider uses ÷ 10.

The divided signal is converted into a reference frequency signal fixed by the phase lock loop 406. The phase-locked loop 406 is used to synchronize 10 MHz with the input signal of 10 MHz again, and is otherwise required to improve the phase noise of the signal. The output of the phase locked loop 406 is suppressed and output through spurious and harmonics through the band pass filter 407 in order not to affect the entire system.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

According to the present invention as described above, in the micro-cellular system based on the subcarrier multiple transmission scheme, it is possible to efficiently transmit synchronization information to each small base station which is miniaturized, thereby enabling flexible soft handoff, thereby improving signal quality, and Cells can be miniaturized because each base station does not have to have a GPS receiver, thereby eliminating obstacles caused by the location of the base station, and minimizing the base station facilitates optimal cell placement as well as optimal cells. Deployment can result in improved call quality and increased subscriber capacity and reduced mortality and administrative costs.

Claims (9)

An apparatus for supplying a synchronization signal to each small base station in a microcellular mobile communication system including a plurality of small base stations connected via a central base station controller and a transmission network, A forward control signal for controlling the small base station, wherein the central base station controller is provided with a reference frequency signal for synchronizing each of the small base stations generated using a reference frequency tone received through a GPS (Global Position System) receiver. And reference frequency transmitting means for power combining with the CDMA signal of the user and transmitting through the transmission network. And The small base station is provided in each of the small base station, by distributing the output of the reference frequency transmitting means received through the transmission network, extracting the reference frequency signal, correcting the phase of the extracted reference frequency signal, the reference frequency signal of each functional unit Reference frequency receiving means provided by Synchronization signal supply device comprising a. The method of claim 1, The reference frequency transmitting means, Reference frequency generating means for generating a reference frequency for synchronization of the small base station by using the reference frequency tone received through the GPS receiver; Power synthesizing means for synthesizing a reference frequency generated by the reference frequency generating means, a forward control signal for controlling the small base station, and a CDMA signal of a user; And Transmission means for amplifying the output of the power synthesizing means, and then converted into an optical signal Synchronization signal supply device comprising a. The method of claim 2, The reference frequency generating means, First distributing means for distributing a signal received through the GPS receiver; Distribution and amplifying means for amplifying by distributing one output of the first distribution means into a plurality of signals; First band filtering means for band filtering the other output of the first distribution means; And Variable attenuation means for adjusting an output level of a signal input from the first band filtering means Synchronization signal supply apparatus comprising a. The method of claim 3, wherein A first phase locked loop provided with the other output of the first distribution means to generate a phase-locked reference frequency signal having a band different from the input reference frequency and providing the first frequency filtering means to the first band filtering means; Synchronization signal supply device further comprising. The method of claim 2, The reference frequency receiving means, Optical / electric conversion means for converting an optical signal received through the transmission network into an electrical signal; First amplifying means for amplifying the output of the photoelectric conversion unit; First power distribution means for distributing the output of the first amplification means into a plurality of signals; Second band filtering means for extracting a reference frequency signal by filtering an output of the first frequency distribution means; A second phase locked loop for correcting the output phase of the second band filtering means; And Second power distribution means for distributing the output of the second phase locked loop into a plurality of signals; Synchronization signal supply apparatus comprising a. The method of claim 5, Second amplifying means for amplifying the gain of the output of the second band filtering means; Synchronization signal supply device further comprising. The method of claim 6, Dispensing means for dispensing the output of the second amplifying means Synchronization signal supply device further comprising. The method of claim 5, A third phase locked loop configured to receive an output of the second power distribution means and provide a phase-locked reference frequency signal Synchronization signal supply device further comprising. A method for providing a synchronization signal to each small base station applied to a microcellular mobile communication system including a plurality of small base stations connected via a central base station controller and a transmission network, Generating a reference frequency signal for synchronizing each of the small base stations using a reference frequency tone received through a GPS (Global Position System) receiver; A second step of combining the generated reference frequency signal with a forward control signal for controlling the small base station and a forward CDMA signal of a user; Extracting the reference frequency signal from the transmitted signal; And A fourth step of correcting a phase of the extracted reference frequency signal to provide a reference frequency signal Synchronization signal providing method comprising a.