KR100857953B1 - Ditial cordless telephone system having enhanced synchronization among base stations - Google Patents

Abstract

A digital cordless telephone (DCT) system is provided that implements enhanced base station synchronization. The DCT system according to the present invention includes a plurality of line cards, a common control fixed part (CCFP) connected to the plurality of line cards, and a plurality of base stations. Each of the plurality of base stations is connected to any one of the plurality of line cards. Each of the plurality of base stations also includes an RF wireless transceiver and a burst mode controller (BMC) for modulating and demodulating data transmitted to and received from the RF wireless transceiver. The CCFP includes a sync clock generator for generating a synch clock. Each of the plurality of base stations receives the synchronous clock generated in the CCFP and uses it to generate an accurate BMC clock signal to enable synchronization between BMCs.

Digital cordless telephone systems, line cards, BMC, CCFP, handover

Description

DITIAL CORDLESS TELEPHONE SYSTEM HAVING ENHANCED SYNCHRONIZATION AMONG BASE STATIONS

1 is an internal block diagram of a conventional exchange system mounted with a plurality of DCT line cards.

2A is a functional block diagram of a DCT in accordance with an embodiment of the present invention.

FIG. 2B is a detailed block diagram of a synchronous clock adjuster included in the base station of FIG. 2A. FIG.

3 is a flowchart illustrating a clock synchronization method between base stations installed with a BMC in a DCT system according to an embodiment of the present invention.

<Description of the reference numerals for the main parts of the drawings>

202: base station

204: BMC

206: synchronous clock adjustment unit

208: line card

210: DSP

212: CCFP

214: synchronous clock generator

220: VCO

222: phase detector

224 loop filter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital cordless telephone (DCT) system that implements improved synchronization between base stations. Particularly, the present invention provides a burst mode controller (BMC) in base stations to realize synchronization between base stations. It relates to a DCT system.

In order to implement a DCT system including a DECT (Digital Enhanced Cordless Telecommunication (DECT)), which is a European wireless communication system, in a private exchange, a DCT line card (DCT line card) that allows each wireless base station of the DCT system to be wired. Shall be mounted in a private exchange. When a DCT line card is mounted in the exchange and the line card and each base station are wired, if only one circuit card is mounted in the exchange, the number of base stations that can be connected is very limited. Therefore, when implementing a large-capacity private exchange supporting many wireless subscribers, a large number of line cards are generally mounted in one exchange. However, in the case where a plurality of circuit cards are installed in the exchange, a control module called a common control fixed part (CCFP) for arbitrating clock synchronization and message exchange between the plurality of circuit cards is installed in the exchange. There is a need.

1 is an internal block diagram of a conventional exchange system in which a plurality of DCT line cards are mounted. As shown in FIG. 1, the exchange system 100 includes a plurality of DCT line cards 104a-104n and CCFP modules 110, each connected to a plurality of base stations 102.

The DCT line cards 104a-104n in the exchange are a plurality of burst mode controllers (Burst Mode) that perform modulation / demodulation, encryption, RF frequency control, etc. on data transmitted and received from the base stations 102 connected to each line card. Controller: BMC) 106, and a digital signal processor 108 for converting ADPCM (Adaptive Differential PCM) signal data from BMC 106 into Pulse Code Modulation (PCM) speech signals. Although not shown in FIG. 1, each of the plurality of base stations 102 includes a power amplifier and amplified data for amplifying the data received from the BMC 106 in the line cards 104a-104n connected to each base station. And an RF transceiver for communicating with the wireless terminal user through. Each of the plurality of DCT line cards 104a-104n can be connected to a plurality of base stations (up to eight base stations), and can accommodate 12 subscribers for each base station, so one line card can accommodate up to 96 subscribers. Configured to do so.

The CCFP 110 includes a synchronous clock generator 112 for generating a synchronous clock SYNC used in the exchange system 100. The CCFP 110 supplies the synchronous clocks generated by the synchronous clock generator 112 to all the line cards 104a-104n to be used as the operation clocks of the line cards, thereby providing a plurality of DCT line cards 104a-104n. Synchronize the clock between them. By synchronizing the clocks of the plurality of circuit cards 104a-104n in this manner, the synchronization of the different base stations 102 connected to the respective circuit cards is synchronized with each other to enable handover between different base stations. do.

However, the conventional exchange system as described above in which the BMC 106 that performs processing for data to be transmitted and received wirelessly is installed in the line cards 104a-104n, provides the CCFP 110 which provides a synchronous clock throughout the system. Although it was possible to maintain synchronization between the base stations by using the, there is a hassle to modify the circuit card (104a-104n) or the CCFP (110) every time the BMC 106 is upgraded. In particular, considering that the BMC 106 is being upgraded very frequently as the DCT technology develops differently each day, the circuit card 104a-104n or the CCFP 110 is changed every time the BMC 106 is upgraded. Redevelopment is costly and time consuming.

An object of the present invention is to provide a DCT system in which a BMC module is mounted in a base station, not a circuit card, so that only the BMC module can be upgraded without replacing the circuit card or CCFP module in the exchange.

Another object of the present invention is to provide a DCT system that implements accurate synchronization between base stations equipped with a BMC module.

According to one aspect of the invention, there is provided a digital cordless telephone (DCT) system, which includes a plurality of line cards, a common control fixing unit (CCFP) connected to the plurality of line cards, and a plurality of line cards. A base station (each of the plurality of base stations is connected to any one of the plurality of line cards), the plurality of base stations, a burst mode controller for modulating and demodulating data transmitted and received through an RF wireless transceiver and the RF wireless transceiver (BMC), wherein the CCFP includes a synchronous clock generator for generating a synchronous clock, wherein the synchronous clock is transmitted to the plurality of circuit cards and is received by the plurality of circuit cards. Is transmitted to respective base stations connected with the plurality of circuit cards.

According to an embodiment of the present invention, each of the plurality of base stations further includes a synchronous clock adjusting unit for generating a BMC clock signal supplied to the BMC using the received synchronous clock.

According to another embodiment of the present invention, the synchronous clock adjusting unit may include a voltage controlled oscillator (VCO) for outputting a constant frequency signal according to a voltage control signal, the synchronous clock and receiving the phase of the synchronous clock and the VCO output signal. A phase filter for comparing the phases and converting the phase difference into a voltage form, and a loop filter for receiving the voltage signal output from the phase detector and removing high frequency components from the signal to generate the voltage control signal, wherein the BMC Let the clock signal be the output signal from the VCO.

According to another aspect of the invention, there is provided a base station connected to any one of the plurality of lines in a DCT telephone system comprising a plurality of line cards, a common control fixing unit (CCFP) connected to the plurality of line cards, The base station includes an RF wireless transceiver and a burst mode controller (BMC) for modulating and demodulating data transmitted and received via the RF wireless transceiver.

The above and other objects, advantages and features of the present invention will become apparent from the following detailed description, which is disclosed with reference to the accompanying drawings, which illustrate exemplary embodiments of the present invention.

The present invention provides a DCT system in which a BMC module is mounted in a base station, not a circuit card, so that only the BMC module can be upgraded without replacing the circuit card or CCFP module in the exchange.

2A illustrates a functional block diagram of a DCT system in accordance with an embodiment of the present invention.

As shown in FIG. 2A, a DCT system 200 according to an embodiment of the present invention is connected to a plurality of line cards 208a-208n, CCFP 212, and respective line cards 208a-208n. A plurality of base stations 202 is included.

Each of the plurality of line cards 208a-208n includes a digital signal processor 210, and the CCFP 212 supplies a synchronous clock SYNC for clock synchronization between the base station 202 and the line cards 208a-208n. And a synchronous clock generator 214 to generate.

The plurality of base stations 202 include a BMC 204 and a synchronous clock adjuster 206. Although not shown for simplicity of explanation, each base station 202 may further include an RF transceiver for communicating the power amplifier and amplified data with a wireless terminal user via a radio frequency. The synchronous clock adjuster 206 generates a BMC driving clock for maintaining accurate synchronization with the BMCs 204 of other base stations using the synchronous clock received from the CCFP 212. The functions of the BMC 204, the power amplifier and the RF transceiver in the base station 202 are the same as described with reference to FIG.

FIG. 2B shows a detailed block diagram of the synchronous clock adjuster 206 included in the base station 202 of FIG. 2A. As shown in FIG. 2B, the synchronous clock adjuster 206 includes a voltage-controlled oscillator (VCO) 220, a phase detector (PD) 222, and a loop filter (LPF) 224. It includes a phase locked loop (PLL) circuit. Although not shown in FIG. 2B, the synchronous clock adjusting unit 206 may further include a divider for dividing an output frequency from the VCO 220 according to a specific division ratio to output a required frequency.

As shown in Figs. 2A and 2B, the base station 202 is generated by the synchronous clock generation unit 214 of the CCFP 214 and received via the synchronous clocks SYNC (each circuit card 208a-208n) ( For example, instead of supplying 2.048 MHz to the driving clock (eg, 10.368 MHz) of the BMC 204 in the base station 202, the output of its own VCO 220 of the synchronous clock adjuster 206 in the base station 202 only. It is used as an input signal for correcting the phase of the signal, and supplies the output signal of this VCO 220 to the BMC 204.

In the synchronous clock adjusting unit 206, the phase detector 222 receives a synchronous clock output from the CCFP 212 and transmitted to each base station 202, and the phase of the input signal and the phase of the VCO 220 output are received. In comparison, the phase difference is converted into a voltage form and transmitted to the LPF 224. The LPF 224 removes high frequency components from the voltage signal from the phase detector 222 and feeds back a voltage for controlling the oscillation frequency of the VCO 220 to the VCO 220 such that the VCO 220 is a reference signal. It is possible to provide a stable oscillation output at the same frequency as that of the synchronous clock. The BMC 204 of the base station 202 uses the signal output from the VCO 220 which oscillates a stable frequency signal by the synchronous clock adjusting unit 206 as it is or divides it to use as a driving clock. As a result, the VCO 220 output signal having the exact frequency / phase coinciding with the synchronization clock generated by the CCFP 212 without skew or noise can be supplied to the driving clock of the BMC 204, thereby synchronizing between the plurality of base stations. Can be kept accurate.

3 is a flowchart illustrating a method for synchronizing clocks between base stations having BMCs installed in a DCT system according to an embodiment of the present invention. First, in step 302, a synchronous clock is generated from the synchronous clock generator of the CCFP in the exchange. In step 304, a synchronization clock from the CCFP is transferred to each line card. In step 306, the synchronous clock input to the line card is transferred to a plurality of base stations connected by wire with each line card. In step 308, each of the plurality of base stations supplies the received synchronization clock as an input signal of the synchronization clock adjuster included in the base station. In step 310, each base station supplies the VCO output signal phase-corrected by the synchronous clock in the synchronous clock adjuster as a driving clock of the BMC.

Although the present invention has been described in connection with the preferred embodiments with reference to the accompanying drawings, it will be apparent to those skilled in the art that various modifications and changes can be made without departing from the spirit and scope of the invention as defined in the following claims. Self-explanatory

According to the present invention as described above, it is possible to provide a scalable DCT system that can be upgraded only the BMC module without replacing the circuit card or CCFP module by mounting the BMC module in the base station, not the circuit card. In addition, instead of using the synchronous clock received from the CCFP module as the driving clock of the BMC module of the base station as it is, the output signal from the VCO oscillating stable frequency signal is supplied to the BMC by the PLL circuit which uses the synchronous clock as a reference input signal. This allows the BMC module to be driven with a signal free of skew or noise while keeping the frequency / phase of the synchronization clock generated by the CCFP accurate even when the base station and the exchange are far apart, thereby maintaining accurate synchronization between multiple base stations. It can set up call, handover, etc. stably.

Claims (7)

Digital Cordless Telephone (DCT) system, A Common Control Fixed Part (CCFP) for generating a synch clock; A plurality of line cards connected to said common control fixture to receive said synchronous clock; And A plurality of base stations, each of the plurality of base stations being connected to any one of the plurality of circuit cards to receive the synchronous clock; Each of the base stations includes a burst mode controller (BMC) for modulating and demodulating the RF radio transceiver and data transmitted and received through the RF radio transceiver, and adjusts a phase of the synchronization clock inputted from the connected line card. Generating a clock signal and supplying the clock signal to the BMC; The BMCs of the plurality of base stations are synchronized by the BMC clock signal. delete The method of claim 1, The synchronous clock adjusting unit may include a voltage controlled oscillator (VCO) for outputting a predetermined frequency signal according to a voltage control signal, and receiving the synchronous clock and comparing the phase of the synchronous clock with the phase of the VCO output signal to form a phase difference. A phase detector for converting the signal into a phase detector; And the BMC clock signal is an output signal from the VCO. The method of claim 3, The synchronous clock adjusting unit further includes a divider for dividing a frequency of the output signal from the VCO according to a predetermined division ratio to output a required frequency. The method of claim 4, wherein The frequency of the synchronous clock and the output signal from the VCO is 2.048 MHz, and the frequency of the BMC clock signal is 1.024 MHz. In the digital cordless telephone (DCT) system including a common control fixing unit (CCFP) for generating a synchronous clock and a plurality of line cards connected to the CCFP to receive the synchronous clock is connected to any one of the plurality of line cards As a base station, RF wireless transceivers; A burst mode controller (BMC) for modulating and demodulating data transmitted to and received from the RF wireless transceiver; And And a synchronous clock adjuster for adjusting a phase of the synchronous clock input from the connected line card to generate a BMC clock signal provided to the BMC. The method of claim 6, The synchronous clock adjusting unit may include a voltage controlled oscillator (VCO) for outputting a predetermined frequency signal according to a voltage control signal, and receiving the synchronous clock and comparing the phase of the synchronous clock with the phase of the VCO output signal to form a phase difference. A phase detector for converting the signal into a phase detector; And the BMC clock signal is an output signal from the VCO.

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