Title of Invention	"FRAME SYNCHRONIZATION METHOD AND COMMUNICATION NETWORK SYSTEM"
Abstract	A frame synchronization method for establishing synchronization between each base station in a TDMA/TDD mode communication network. A control channel transmission timing generated at a master base station 1 is converted into a timing signal and transmitted to subsidiary base stations 2 using commercial power supply line 100. The subsidiary base station 2 generates a control channel transmission timing based on the timing signal received from the commercial power supply line 100.

Title of Invention

"FRAME SYNCHRONIZATION METHOD AND COMMUNICATION NETWORK SYSTEM"

Abstract

A frame synchronization method for establishing synchronization between each base station in a TDMA/TDD mode communication network. A control channel transmission timing generated at a master base station 1 is converted into a timing signal and transmitted to subsidiary base stations 2 using commercial power supply line 100. The subsidiary base station 2 generates a control channel transmission timing based on the timing signal received from the commercial power supply line 100.

Full Text	BACKGROUND OF THE INVENTION FIELD OF THE INVENTION This present invention relates to a frame synchronization method and also to a communication network system which establishes synchronization of phases of control signal cycles among a plurality of base stations employing a Time Division Multiple Access / Time Division Duplex (TDMA/ TDD) method. DESCRIPTION OF THE PRIOR ART Figure 7, for example, depicts a configuration of a base station disclosed in Japanese Patent Laid-Open Publication No. Hei 04-94226. A network control unit 301 is connected to a "Public, Switched Telephone Network (PSTN) or Private Branch exchange (PBX) or the like which are not shown in Figure 7. A codec converter 302, which has connections with a buffer memory 303 and a clock oscillator circuit 304, is connected to the network control unit 301 A communication control unit 305 which is connected to the network control unit 301 has connections with a TDMA/TDD processor 306, a transmitter unit 310, and a receiver unit 320 Both the transmitter and receiver units are connected to an antenna 330 via an antenna switch 340. A power supply unit 350 is connected to the clock oscillator circuit 304 where a clock based on a frequency of commercial power supply line (50 Hz or 60 Hz) is provided. The transmitter unit 310 comprises a modulator 311, a transmitter 312, and a synthesizer 313, whereas the receiver unit 320 comprises a receiver 321, a demodulator 322, and a synthesizer 323. An explanation of the action of the above mentioned base station will next be given At the network control unit 301, in a reverse direction from a base station to a mobile station, a signal transmitted from the network is supplied in a burst mode and this input burst signal is divided into a control signal and a communication signal. In this reverse direction, the communication signal from the network divided by the network control unit 301 is supplied to the codec A/D converter 302. The codec converter 302 executes analogue conversion of the communication signal such as coded voice signal from the network. In the reverse direction, an analogue-converted communication signal is supplied in a burst mode into the buffer memory 303. The buffer memory 303 temporarily stores the supplied communication signal The clock oscillator circuit 304 generates a timing pulse which is referred to by transmission clocks for both this base station and the mobile station accessing the base station. This timing pulse is generated individually at each base station To the clock oscillator circuit 304, a clock is supplied based on the frequency of the commercial power supply (perhaps 50 Hz or 60 Hz), from the power supply unit 350 that provides local power to this base station The clock is produced by multiplication or division the frequency of the commercial ppwer supply. Based on this given clock, the clock oscillator circuit 304 generates and then sends out a timing pulse which establishes synchronization between each of the base stations The communication control unit 305 is connected to the network control unit 301, and to the buffer memory 303 by way of the TDMA/TDD processor 306 In the reverse direction, both the control signal from the network which was divided by the network control unit 301 and the communication signal stored in the buffer memory 303 are given to the communication control unit 305. When the control signal from the network is given, the communication control unit 305 searches an idle channel and provides the mobile station with a terminating traffic signal including information of the searched idle channel to negotiate establishment of a channel that will be used for communication In the reverse direction, the timing pulse from the clock oscillator circuit 304, the communication signal from the buffer memory 303 and the control signal from the communication control unit 305 are provided to the TDMA/TDD processor 306. In the forward direction from a mobile station to a base station, a transmission signal from the mobile station received by a later-described receiver unit 320 is supplied to the TDMA/TDD processor 306. In the reverse direction, based on the communication signal and the control signal from the buffer memory 303 and the communication control unit 305, the TDMA/TDD processor determines a content of both a channel burst signal and a TDMA/TDDMA frame to transmit a signal to the mobile station. Based on the timing of the timing pulse from the clock oscillator circuit 304, the TDMA/TDD processor 306 supplies the transmission signal for a mobile station comprising the determined TDMA/TDDMA frame, in a burst mode, to a later-described transmitter unit 310. At the same time, TDMA/TDD processor 306 sends a transmission start signal to the transmitter unit 310 to order an activation of transmission. In the forward direction, among signals from the mobile station received by the later-described receiver unit 320, this TDMA/TDD processor 306 sends out a control signal to the communication control unit 305 and a communication signal to the buffer memory 303. The TDMA/TDD 306 also monitors the received transmission signal I e., the frame synchronization signal in the channel burst signal, by a frame synchronization detector circuit (not shown in Figure 7) placed in the TDMA/TDD processor 306. In the forward direction the buffer memory 303 where the communication signal from the TDMA/TDD processor 306 is supplied, stores this communication signal temporarily and sends it out in a burst mode to the network control unit 301. On the other hand, the communication control unit 305 where the control signal from the mobile station is received through the TDMA/TDD processor 306, determines, using this control signal, a channel for communication signal transmission which will be used between the base station itself and the mobile station. Then it notifies the TDMA/TDD 306 of the determined channel. Accordingly, the TDMA/TDD processor 306 which received the channel notification notifies a carrier frequency of the determined channel to the transmitter unit 310 and the receiver unit 320 which execute radio transmission and reception. At the transmitter unit 310, the modulator 311 is connected to the TDMA/TDD processor 306 and modulates the transmission signal from the TDMA/TDD processor 306 The transmitter 312 is connected to this modulator 311, and sends out the modulated signal to the mobile station via the antenna 330 and a mobile radio circuit (not shown in Figure 7). On the other hand, in the receiver unit 320, a transmission signal from the mobile station via the antenna 330 and a mobile radio circuit (not shown in Figure 7) is supplied to the receiver 321 The receiver 321 detects a reception level of the received transmission signal from the mobile station, and notifies this to the TDMA/TDD processor 306 as an electric field detection signal. The demodulator 322 is connected to the receiver 321 and sends out to the TDMA/TDD processor 306 a digital signal which was demodulated from the transmission signal from the mobile station The antenna switch 340 exists between the antenna 330 and both the transmitter 312 and the receiver 321, and switches a connection to either the transmitter 312 or the receiver 321 This antenna switch 340 switches the status of the base stations to transmission or reception in accordance with a timing of an area of reverse or forward direction communication in the TDMA/TDDMA frame in the mobile radio channel. Normally in order to receive a control signal it is switched to the receiver 321 so that it receives a signal at a fixed carrier. A transmission start signal from the TDMA/TDD processor 306 is sent to both the antenna switch 340 and the receiver 321. Based on this transmission start signal, the antenna switch 340 switches its connection to the transmitter 312, and the transmitter 312 sends out the transmission signal from the TDMA/TDD processor 306 via the modulator 311 to the mobile station. The synthesizer 313 and 323 which oscillate at a variable frequency are connected to the transmitter 312 and the receiver 321 respectively Both the transmitter 312 and the receiver 321 can discretionally change a frequency of transmission or reception at the transmitter 312 or the receiver 321 based on the order of the communication control unit 305 Each synthesizer 313 or 323, if the base station is in a stand-by status, oscillates by a control of the communication control unit 305 at a frequency so that the transmitter 312 and the receiver 321 can always execute transmission or reception matching a control signal to a fixed carrier for transmission. They change frequency according to that of an idle channel to transmit communication signal when they are in communication with the network. Each synthesizer 313 or 323 as well as the TDMA/TDD processor 306 receive from the network control unit 305 the result of channel selection for communication signal transmission The frequency is changed in accordance with this selection result. Having a configuration of the prior art base stations, an additional judgment circuit to distinguish 50 Hz from 60 Hz is necessary in order to synchronize phases between base stations to the one of the commercial power supply line. This judgment circuit is placed in the clock oscillator circuit 304 and judges if a signal from the power supply unit is 50 Hz or 60 Hz by the frequency of the signal. Based on this judgment, the clock oscillator circuit multiples the signal from the power supply unit and generates a certain reference timing pulse. In this instance, the base station automatically judges if the power supply is 50 Hz or 60 Hz without set up on activation The prior art base stations have possibilities of a control channel conflict depending on a situation of signal transmission route Each clock oscillator circuit 304 in each station generates a timing pulse respectively. The timing pulse is generated by multiplying a signal from the power supply unit. If all multiplying circuit work accurately, there will be no problem. However, in reality, there exist small errors and accumulation of these errors causes a conflict of timing slots and consequently a control channel conflict can occur. Besides, upon activation of transmission, each base station searches an idle channel for communication at a same time and a time slot of a same channel can be selected . In this case control channels conflict. SUMMARY OF THE INVENTION This invention is created to solve the above-described problems and its purpose is to obtain a frame synchronization method and a device which can synchronize phases with certainty by transmitting a signal from a master base station to a subsidiary base station. To achieve these objects, the frame synchronization method related to this invention includes the steps of transmitting a control channel transmission timing signal generated at the master base station to a TDMA/TDD mode subsidiary base station through commercial power supply line, and of generating a control channel transmission timing based on the received timing signal at the subsidiary base station. By this method, synchronization of control signal phases between the master and the subsidiary base stations can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal from the master base station via commercial power supply line. Another aspect of the frame synchronization method related to this invention is characterized by a frame synchronization method wherein a control channel transmission timing generator by a base station is converted into a timing signal, and wherein this timing signal is transmitted to a TDMA/TDD mode subsidiary base station using a radio wave or an infrared, and wherein the subsidiary base station generates a control channel transmission timing based on the timing signal In this method, a synchronization of phases of control signals between the master base station and the subsidiary base station can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal provided by the master base station in the form of a radio wave or an infrared signal Another aspect of the frame synchronization method related to this invention is characterized by a frame synchronization method wherein a control channel transmission timing generated by a base station is converted into a timing signal, and wherein this timing signal is transmitted to a TDMA/TDD mode subsidiary base station using a communication channel, and wherein said subsidiary base station generates a control channel transmission timing based on said timing signal. In this method, synchronization of phases of control signals between the master base station and the subsidiary base station can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal provided by the master base station via a communication channel. A communication network system related to this invention is a communication network system of TDMA/TDD mode involving a master base station and at least one subsidiary base station wherein said master base station generates a timing signal based on a control channel transmission timing, and has a timing generator which supplies this timing signal to commercial power supply line, and wherein said subsidiary base station has a timing receiver which generates a control channel transmission timing based on the timing signal from the commercial power supply line, and wherein frame synchronization between the master base station is established and the subsidiary base station is established based on said timing signal supplied through the commercial power supply line. In this system, a synchronization of phases of control signals between a master base station and a subsidiary base station can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal provided by the master base station via commercial power supply line. A further aspect of a communication network system related to this invention is a communication network system of TDMA/TDD mode comprising a master base station and at least one subsidiary base station wherein said master base station includes a timing generator which generates an electric timing signal based on a control channel transmission timing and means for transmitting said electric timing signal generated by said timing generator in a form of a radio wave or an infrared beam, and wherein said subsidiary base station includes means for receiving said signal in a form of a radio wave or an infrared beam and converting it into an electric timing signal, and a timing receiver which generates a control channel transmission timing based on said timing signal received by said receiving means, and wherein frame synchronization between said master base station and said subsidiary base station is done based on said timing signal transmitted or received as a signal in a form of a radio wave or an infrared beam In this system, synchronization of phases of control signal between the master base station and the subsidiary base station can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal provided by the master base station in the form of a radio wave or an infrared beam A still further aspect of a communication network system related to this invention is a TDMA/TDD mode communication network system comprising a master base station and at least one subsidiary base station wherein said master base station has a timing generator which generates a timing signal based on a control channel transmission timing and supplies said timing signal to a communication channel, and wherein said subsidiary base station has a timing receiver which generates a control channel transmission timing based on said timing signal received from said communication channel, and wherein frame synchronization between said master base station and said subsidiary base station can be done based on said timing signal transmitted via said communication channel In this system, synchronization of phases of control signals between the master base station and the subsidiary base station can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal provided by the master base station via a communication channel. Accordingly, the present invention relates to a frame synchronization method comprising the steps of converting a control channel transmission timing generated by a master base station into a timing signal, transmitting said timing signal to at least one subsidiary base station of TDMA/TDD mode via commercial power supply line, and generating a control channel transmission timing based on said timing signal at said subsidiary base station The present invention also relates to a frame synchronization method comprising the steps of converting a control channel transmission timing generated by a master base station into a timing signal, transmitting said timing signal to at least one subsidiary base station of TDMA/TDD mode using a radio wave or an infrared, and generating of a control channel transmission timing based on said timing signal at said subsidiary base station The present invention also relates to a frame synchronization method comprising the steps of converting a control channel transmission timing generated by a master base station into a timing signal, transmitting said timing signal to at least one subsidiary base station of TDMA/TDD mode through communication line, and generating a control channel transmission timing based on said timing signal at said subsidiary base station The present invention also relates to a TDMA/TDD mode communication network system comprising a master base station and at least one subsidiary base station wherein said master base station is provided with a timing generating means which generates a timing signal based on a control channel transmission timing and supplies said timing signal to a commercial power supply line, and wherem said subsidiary base station is provided with a timing receiving means which generates a control channel transmission timing based on said timing signal received from said commercial power supply line, and frame synchronization between said master base station and said subsidiary base station is established based on said timing signal transmitted via said commercial power supply line The present invention also relates to a communication network system of TDMA/TDD mode comprising a master base station and at least one subsidiary base station wherein said master base station includes a timing generating means which generates an electnc timing signal based on a control channel transmission timing and means for transmitting said electnc timing signal generated by said timing generating means in radio or infrared form, and wherein said subsidiary base station includes receiving means for receiving said signal in a form of a radio wave or an infrared and converting it into an electric timing signal, and a timing receiving means which generates a control channel transmission timing based on said timing signal received by said receiving means, and a frame synchronization between said master base station and said subsidiary base station is established based on said timing signal transmitted or received as a signal in radio or infrared form The present invention also relates to a TDMA/TDD mode communication network system comprising a master base station and at least one subsidiary base station wherein said master base station is provided with a timing generating means which generates a timing signal based on a control channel transmission timing and supplies said timing signal to a communication channel, and wherein said subsidiary base station is provided with a tuning receiving means which generates a control channel transmission timing based on said timing signal received from said communication channel, and frame synchronization between said master base station and said subsidiary base station is established based on said timing signal transmitted via said communication channel BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Figure 1 is a diagram showing configurations of a master base station and a subsidiary base station used in the present invention. Figure 2 is a diagram showing a configuration of a timing generator used in this invention. Figure 3 is a diagram showing a configuration of a timing receiver used in this invention Figure 4 is a timing chart of timing signals used in this invention. Figure 5 is a diagram showing configurations of a master base station and a subsidiary base station in accordance with another embodiment of the present invention. Figure 6 is a diagram showing configurations of a master base station and a subsidiary base station in accordance with another embodiment of the present invention. Figure 7 is a diagram showing a configuration of a base station used in the prior art. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Figure 1 is a diagram showing configurations of a master base station and a subsidiary base station in which the frame synchronization method described in embodiment 1 of this invention is applied. In embodiment 1, a control channel transmission timing generated at a master base station 1 is converted into a pulse signal P (see Figure 4) and is transmitted through commercial power supply line 100 to a subsidiary base station 2 of a TDMA/TDD mode. The master base station 1 comprises an antenna switch (ANT-SWITCH) 11-1, a transmitter 12-1, a receiver 13- 1, a TDMA/TDD processor 14-1, a Central Processing Unit (CPU) 15-1, a codec Analogue to Digital (A/D) converter 16-1, a network control unit 17-1, a power supply unit 18-1, and a timing generator 19-1 which is connected to the power supply unit. The power supply unit is connected to commercial power supply line 100. Figure 2 shows a configuration of the timing generator 19-1. As is shown in Figure 2, the timing generator 19-1 comprises a reference clock generator circuit 21-1 which generates a reference clock, a frame clock generator 22-1, and a signal converter 23-1. Based on a reference clock given by the reference clock generator circuit 21-1, the frame clock generator 22-1 generates one frame clock made of a transmission frame TX and a reception frame RX in Figure 4. With control channel transmission timing which is a timing to switch the generated transmission frame TX and the reception frame RX, the TDMA/TDD processor 14-1 and the codec A/D converter 16-1 process data. The control channel transmission timing is converted into a pulse signal P at the signal converter 23-1, and supplied to the commercial power supply line 100 via the power supply unit 18-1. The subsidiary base station 2 in Figure 1 comprises an antenna switch 11-2, transmitter 12-2, a receiver 13-2, a TDMA/TDD processor 14-2, a CPU 15-2, a codec A/D converter 16-2, a network control unit 17-2, a power supply unit 18-2, and a timing receiver 19-2 which is connected to the power supply unit. The power supply unit 18-2 is connected to a commercial power supply line 100. Figure 3 is a diagram showing a configuration of the timing receiver 19-2. The timing receiver 19-2 comprises a reference clock generator circuit 21-2, a frame clock generator unit 22-2, and a signal converter 23-2. The signal converter 23-2 generates a control channel transmission timing based on a received pulse signal from commercial power supply line 100 by way of the power supply unit 18-2, whereas the frame clock generator unit 22-2 generates a frame clock based on the control channel transmission timing and the reference clock. The TDMA/TDD processor 14-2 and the codec A/D converter 16-2 process data signals based on the frame clock and control channel transmission timing. An illustration of the embodiment follows. The network control unit 17-1 in the master base station 1 is connected to Public Switched Telephone Network (PSTN) 102 and controlled by the CPU 15-1. A data signal given to this network control unit is converted by the codec A/D converter 16-1 and supplied to the TDMA/TDD processor 14-1. This TDMA/TDD processor 14-1 supplies the data signal to transmitter 12-1 based on a timing signal from the timing generator 19- 1. The data signal is transmitted from an antenna A-l via the antenna switch ANT-SW 11-1. On the other hand, data signal received by this antenna A-l is given to the receiver 13-1 via the antenna switch 11-1 and then sent to the PSTN 102 in a route which is a reversal of transmission process described above The network control unit 17-2 in the subsidiary base station 2 is connected to the PSTN 102 and controlled by the CPU 15-2. A data signal input to the network control unit 17-2 is converted by the codec A/D converter 16-2 and supplied to the TDMA/TDD processor 14-2. This TDMA/TDD processor 14-2 supplies the data signal to transmitter 12-2 based on a timing signal from the timing receiver 19-2. The data signal is transmitted from an antenna A-2 via the antenna switch ANT-SW 11-2. On the other hand, data signal received by this antenna A-2 is given to the receiver 13-2 via the antenna switch 11-2 and then sent to the PSTN 102 in a route which is a reversal of transmission. In embodiment 1 described above, a timing signal generated by the timing generator 19-1 in the master base station 1 is sent to each subsidiary base station 2 through the commercial power supply line 100. At each subsidiary base station 2, the timing receiver 19-2 generates a control channel transmission timing based on the previously-described timing signal. This enables synchronization between the master base station 1 and the subsidiary base station 2 with certainty. Therefore, unlike the prior method in which each station individually sets timing based on the frequency of the commercial power supply, in this method conflicts of timing slot and the like are avoidable. It is also possible in embodiment 1 for any subsidiary base station 2 to function as a new master base station, replacing the master base station 1 in case of possible failure of the timing generator 19-1. In this case, the subsidiary base station 2 replacing the master base station 1 sends out a reference timing signal to commercial power supply line 100 using a previously established timing generator. A diagnosis of a failure in the master base station 1 can be made by a known failure diagnostic function In embodiment 1 it is also preferable for each station to decide in advance an order of idle channel search at a time of transmission activation. One way to accomplish this is that the master base station 1 searches an idle channel first, followed by each subsidiary station sequentially, following an order from the master base station 1. In this way, multiple selection a time slot of the same channel at the same time can be avoided with certainty Another method is to set timings of idle channel search by the master base station 1 and the subsidiary base station 2 in advance In this way, a control channel conflict in the prior art can be avoided Embodiment 2 In embodiment 2, a control channel transmission timing generated by the timing generator 19-1 in the master base station 1 is converted into a tone signal T which is shown in Figure 4, and this tone signal T is then sent out as a timing signal to commercial power supply line 100 via power supply unit 18-1. On the other hand, at the subsidiary base station 2, control channel transmission timing is generated in the timing receiver 19-2 using the tone signal T input to the power supply unit 18-2 via commercial power supply line 100, and a frame clock is then generated based on this timing Embodiment 3 In embodiment 3, a control channel transmission timing generated by the timing generator 19-1 in the master base station 1 is converted into a frame synchronization signal F m spread spectrum which is shown m Figure 4, and this frame synchronization signal F in spread spectrum is then sent out as a timing signal to a commercial power supply line 100 via power supply unit 18-1. On the other hand, at the subsidiary base station 2, a control channel transmission timing is generated by the timing receiver 19-2 using the spread spectrum synchronization signal F given to the power supply unit 18-2 via the commercial power supply line 100, and a frame clock is then generated based on this timing. Embodiment 4 In embodiment 4, a control channel transmission timing generated by the timing generator 19-1 at the master base station 1 is converted into a frame synchronization and data signal FD which is shown in Figure 4, and this frame synchronization and data signal FD is then sent out as a timing signal to commercial power supply line 100 via power supply unit 18-1. On the other hand, at the subsidiary base station 2, a control channel transmission timing is generated by the timing receiver 19-2 using the frame synchronization and data signal FD given to the power supply unit 18-2 via the commercial power supply line 100, and a frame clock is then generated based on this timing. Embodiment 5 In embodiment 5, a control channel transmission timing generated by the timing generator 19-1 in the master base station 1 is converted into a voltage signal V shown in Figure 4 using a voltage converter circuit (not shown in Figure 1), and then this voltage signal V is sent out as a timing signal to commercial power supply line 100 via the power supply unit 18-1. On the other hand, at the subsidiary base station 2, control channel transmission timing is generated by the timing receiver 19-2 using the voltage signal V given to the power supply unit 18-2 via commercial power supply line 100, and then a frame clock is generated based on this timing. In the above described embodiments 2 to 5, the tone signal T, the frame synchronization signal F, the frame and data signal FD, and the voltage signal V are transmitted respectively as a timing signal from the master base station 1 to the subsidiary base station 2 through the commercial power supply line 100, and synchronization between base stations can be controlled with certainty by the timing signal. Embodiment 6 Figure 5 is a diagram showing configurations of a master base station and a subsidiary base station in accordance with another embodiment of the present invention. In embodiment 6, a control channel transmission timing generated by a base station 1 is converted into a pulse signal P (see Figure 4) and transmitted to a subsidiary base station 2 using a radio wave or an infrared 101 as a medium. The master base station 1 comprises an antenna switch 41-1, a transmitter unit 42-1, a receiver unit 43-1, a TDMA/TDD processor 44-1, a CPU 45-1, a codec A/D converter 46-1, a network control unit 47-1, a power supply unit 48-1, and a timing generator 49-1 connected to the transmitter unit 42-1. The subsidiary base station comprises an antenna switch 41-2, a transmitter 42-2, a receiver 43-2, a TDMA/TDD processor 44-2, a CPU 45- 2, a codec A/D converter 46-2, a network control unit 47-2, a power supply unit 48-2, and a timing receiver 49-2 connected to the receiver 43-2. Configurations of the timing generator 49-1 and the timing generator 49-2 are the same as for respective timing generator 19-1 and the timing receiver 19-2 in Figures 2 and 3 of embodiment 1. However, in this embodiment 6, a signal from the timing generator 49-1 is sent out to the transmitter 42-1 and then transmitted from the antenna A-l via the antenna switch 41-1. A signal is given to the timing receiver 49-2 from the receiver 43-2 through the antenna A-2 and the antenna switch 41-2. An example of this embodiment follows The network control unit 47-1 in the master base station 1 is connected to the Public Switched Telephone Network (PSTN) 102 and controlled by the CPU 45-1 A data signal given to this network control unit is converted by the codec A/D converter 46-1 and supplied to the TDMA/TDD processor 44-1. This TDMA/TDD processor 44-1 supplies the data signal to the transmitter 42-1 based on a timing signal from the timing generator 49-1. The data signal is transmitted as a signal in a form of a radio wave or an infrared, from the antenna A-l via the antenna switch ANT-SW 41-1. On the other hand, the data signal received by this antenna A-l is given to the receiver 43-1 via the antenna switch 41-1 and then sent to the PSTN 102 in a route which is a reversal of transmission. The network control unit 47-2 in the subsidiary base station 2 is connected to the PSTN 102 and controlled by the CPU 45-2. A data signal given to the network control unit 47-2 is converted by the codec A/D converter 46-2 and supplied to the TDMA/TDD processor 44-2. The TDMA/ TDD processor 44-2 sends the data signal to the transmitter 42-2 based on the timing signal from the timing receiver 49-2, and then transmits it as a signal in a form of a radio wave or an infrared, from the antenna A-2 via the antenna switch 41-2 The data signal received by the antenna A-2 is given to the receiver 43-2 via the antenna switch 41-2 and then sent to the PSTN 102 in a reverse route from transmission Hence, in this embodiment 6, the timing signal generated by the timing generator 49-1 is transmitted from the antenna as a signal in a form of a radio wave or an infrared beam. This signal is received by each subsidiary base station 2 and a timing signal separated from a data signal is supplied from the receiver 43-2 to the timing receiver 49-2 of the subsidiary base station 2 Synchronization between station 1 and station 2 can be established as in the above and, as a result, undesirable phenomena such as channel conflicts can be prevented with certainty Embodiment 7 In embodiment 7, a control channel transmission timing generated by the timing generator 49-1 in the master base station 1 is converted into a tone signal T shown in Figure 4. The tone signal T is sent out to the transmitter 42-1 as a timing signal via the antenna switch 41-1, and sent out from the antenna A-l as a signal 101 in a form of a radio wave or an infrared. On the other hand, in the subsidiary base station 2, the tone signal T sent as a signal 101 in a form of a radio wave or an infrared is received by the antenna A-2. It is then sent to the timing receiver 49-2 via the antenna switch 41-2 and the receiver 43-2. The timing receiver 49-2 generates a control channel transmission signal based on this tone signal T , and a frame clock is generated based on this timing. Embodiment 8 In embodiment 8, a control channel transmission timing generated at the timing generator 49-1 in the master base station 1 is converted into a spread spectrum frame synchronization signal F shown in Figure 4. The spread spectrum frame synchronization signal F is sent out to the transmitter 42-1 as a timing signal via the antenna switch 41-1, and sent out from the antenna A-l as a signal 101 in a form of a radio wave or an infrared. On the other hand, in the subsidiary base station 2, the spread spectrum frame synchronization signal F sent as a signal 101 in a form of a radio wave or an infrared is received by the antenna A-2 It is then sent to the timing receiver 49-2 via the antenna switch 41-2 and the receiver 43-2 The timing receiver 49-2 generates a control channel transmission signal based on this spread spectrum frame synchronization signal F, and frame clock is generated based on this timing Embodiment 9 In embodiment 9 a control channel transmission timing generated at the timing generator 49-1 in the master base station 1 is converted into a frame synchronization and data signal FD shown in Figure 4. The frame synchronization and data signal FD is sent out to the transmitter 42-1 as a timing signal via the antenna switch 41-1, and from the antenna A-l as a signal 101 in the form of a radio wave or an infrared beam. On the other hand, in the subsidiary base station 2, the frame synchronization and data signal FD sent as a signal 101 in the form of a radio wave or an infrared beam is received by the antenna A-2. It is then sent to the timing receiver 49-2 via the antenna switch 41-2 and the receiver 43-2. The timing receiver 49-2 generates a control channel transmission signal based on this frame synchronization and data signal FD, and frame clock is generated based on this timing. As described above, in embodiments 7, 8, and 9, the timing signal is converted into the tone signal T, the frame synchronization signal F, and the frame synchronization and data signal FD, respectively. Since this timing signal is sent from the master base station 1 to the subsidiary base station 2 as a signal 101 in radio or infrared form, synchronization between each of stations can established with certainty. Embodiment 10 Figure 6 is a diagram showing a system configuration related to embodiment 10 In embodiment 10, in order to synchronize phases of base stations which are not reachable by radio waves, a control channel transmission timing generated by the master base station 1 is converted into a pulse signal P (see Figure 4) or other form of signal, and then sent to the subsidiary base station 2 via the PSTN 102 as a communication channel. A master base station 1 comprises an antenna switch 51-1, a transmitter 52-1, a receiver 53-1, a TDMA/TDD processor 54-1, a CPU 55-1, a codec A/ D converter 56-1, a network control unit 57-1, a power supply unit 58-1, and a timing generator 59-1 connected to the codec A/D converter 56-1. A subsidiary base station 2 comprises an antenna switch 51-2, a transmitter 52-2, a receiver 53-2, a TDMA/TDD processor 54-2, a CPU 55- 2, a codec A/D converter 56-2, a network control unit 57-2, a power supply unit 58-2, and a timing receiver 59-2 which is connected to the codec A/D converter 56-2. Configurations of the timing generator 59-1 and the timing receiver 59- 2 are the same as for the timing generator 19-1 and the timing receiver 19-2 in Figures 2 and 3 of embodiment 1. In this embodiment 10, a timing signal from the timing generator 59-1 is sent out to the codec A/D converter 56-1, and then to the PSTN 102 via the network control unit 57-1. A timing signal is supplied to the timing receiver 59-2 through the PSTN 102, the network control unit 57-2 and the codec A/D converter 56-2. An example of this embodiment follows. The network control unit 57-1 is connected to the PSTN 102 and controlled by the CPU 55-1. A data signal given to the network control unit 57-1 is converted by the codec A/D converter 56-1 and then supplied to the TDMA/TDD processor 54-1. The TDMA/TDD processor 54-1 sends the data signal to the transmitter 52-1 based on the timing signal of the timing generator 59-1. It then transmits the data signal from the antenna A-1 via the antenna switch 51-1. On the other hand, a data signal received at this antenna A-1 is sent the receiver 53-1 via the antenna switch 51-1, and then sent to the PSTN 102 in a route opposite to transmission. The network control unit 57-1 in the subsidiary base station 2 is connected to the PSTN 102 and controlled by the CPU 55-2. The data signal given to the network control unit 57-2 is converted by the codec A/D converter 56-2 and then given to the TDMA/TDD processor 54-2. This TDMA/TDD processor 54-2 sends the data signal to the transmitter 52-2 based on a timing by the timing receiver 59-2. The data signal is transmitted from the antenna A-2 via the antenna switch 51-2. A data signal received by the antenna A-2 is sent to the receiver 53-2 via the antenna switch 51-2, and then supplied to the PSTN in a route opposite that of transmission. In this embodiment 10, a timing signal generated by the timing generator 59-1 is sent to the network control unit 57-1 via the codec A/ D converter 56-1, and then to the PSTN with a data signal. At each subsidiary base station 2, the signal received by the network control unit 57-2 through the PSTN is divided into the data signal and the timing signal The separated timing signal is sent from the codec A/D converter 56-2 to the receiver 59-2, and then used as the timing signal for the subsidiary base station 2. Therefore, by this timing signal the master base station 1 and the subsidiary base station 2 can establish synchronization with certainty. The master base station 1 is also always monitoring traffic of PSTN at the CPU 55-1. If it judges that the traffic is less than a prescribed threshold value, it connects a channel to a subsidiary base station 2 and sends out a timing signal. In this case, since the channel is not always open, gradual phase shift can occur, and a phase jump is possible upon synchronization of phases To prevent this, it is preferable for the reference clock oscillator circuits 21-1 and 21-2 of the timing generator 59-1 and the timing receiver 59-2 to have circuits with highly accurate original oscillation frequency. Embodiment 11 In embodiment 11, a control channel transmission timing generated by the timing generator 59-1 in the master base station 1 is converted into a tone signal T shown in Figure 4. The tone signal T is then converted into a voice signal and sent to the PSTN 102 from the network control unit 57-1 In the subsidiary base station 2, a control channel transmission timing is generated at by the timing receiver 59-2 based on the tone signal T given to the network control unit 57-2 from the PSTN. A frame clock is generated by this timing Embodiment 12 In embodiment 12, a control channel transmission timing generated by the timing generator 59-1 in the master base station 1 is converted into a spread spectrum frame synchronization signal F shown in Figure 4. The spread spectrum frame synchronization signal F is then converted into a voice signal and sent to the PSTN 102 from the network control unit 57-1. In the subsidiary base station 2, a control channel transmission timing is generated at by the timing receiver 59-2 based on the spread spectrum frame synchronization signal F given to the network control unit 57-2 from the PSTN. A frame clock is generated by this timing. Embodiment 13 In embodiment 13, a control channel transmission timing generated by the timing generator 59-1 in the master base station 1 is converted into a frame synchronization and data signal FD shown in Figure 4. The frame synchronization and data signal FD is then converted into a voice signal and sent to the PSTN 102 from the network control unit 57-1. In the subsidiary base station 2, a control channel transmission timing is generated at by the timing receiver 59-2 based on the frame synchronization and data signal FD given to the network control unit 57- 2 from the PSTN A frame clock is generated by this timing. As described above, in embodiments 11, 12, and 13, a timing signal is sent to the PSTN as a tone signal T, or a frame synchronization signal F, or a frame synchronization and data signal FD, respectively. Synchronization between the master base station 1 and the subsidiary base station 2 can be established using this timing signal. In these embodiments above, a control channel transmission timing is converted into any signal of a pulse, a tone, a frame synchronization, or a frame and data It is then sent out through any medium of commercial power supply line 100, a radio wave or an infrared beam 101, or the PSTN 102 as communication line. Signals other than the ones described above can be used in the same way as in these embodiments, as long as they can be transmitted as described above. Further, if both the master base station 1 and the subsidiary base station 2 have batteries and are made as to be switched to a precise self-running clock in a case of service interruption of commercial power supply, the status before interruption can be held and restart of an action after the power supply is reestablished can be smoothly accomplished In this invention, a master base station is assumed to synchronize timing However, it is possible for the timing generator of the master base station to be out of order. As a countermeasure of a failure of the master base station, it is preferable for a base station previously working as a subsidiary base station to function as the base station for generating timing signals. Failure detection of the master base station can be done by self-diagnostics Further, by deciding the order of each station's idle channel search at the time of activation of transmission, conflicts of control channel can be avoided. As one means to accomplish this, the master base station first selects a channel, then each subsidiary base station sequentially selects a channel following orders from the master base station. Another method is a prescribed timing setting of an idle channel search by each station. While there have been described what are at present considered to be preferred embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention. We claim: 1. A frame synchronization method to synchronize a control channel transmission timing comprising the steps of: converting a control channel transmission timing generated by a master base station into a timing signal; transmitting said timing signal to at least one subsidiary base station of TDMA/TDD mode via commercial power supply line or using a radio wave or an infrared or through communication line, and generating a control channel transmission timing based on said timing signal at said subsidiary base station. 2. A method as claimed in claim 1, wherein said timing signal is transmitted from the master base station to each subsidiary base station as a pulse signal or as a tone signal or as a spread spectrum frame synchronization signal or as a frame synchronization and data signal. 3. A method as claimed in claim 1, wherein said communication channel is a Public Switched Telephone Network (PSTN). 4. A method as claimed in claim 3, wherein said master base station is always monitoring said PSTN traffic; and said master base station connects a channel to said subsidiary base station and sends said timing signal when said traffic is less than a predetermined threshold value. 5. A TDMA/TDD mode communication network system for synchronizing a control channel transmission timing by a method as claimed in any one of claimed comprising a master base station and at least one subsidiary base station wherein said master base station is provided with a timing generating means which generates a timing signal based on a control channel transmission timing and supplies said timing signal to a commercial power supply line or to a communication channel; and wherein said subsidiary base station is provided with a timing receiving means which generates a control channel transmission timing based on said timing signal received from said commercial power supply line or from said communication channel; and frame synchronization between said master base station and said subsidiary base station is established based on said timing signal transmitted via said commercial power supply line or via said communication channel. 6. A TDMA/TDD mode communication network system as claimed in claim 1, comprising a master base station and at least one subsidiary base station wherein said master base station includes a timing generating means which generates an electric timing signal based on a control channel transmission timing and means for transmitting said electric timing signal generated by said timing generating means in radio or infrared form; and wherein said subsidiary base station includes receiving means for receiving said signal in a form of a radio wave or an infrared and converting it into an electric timing signal, and a timing receiving means which generates a control channel transmission timing based on said timing signal received by said receiving means; and a frame synchronization between said master base station and said subsidiary base station is established based on said timing signal transmitted or received as a signal in radio or infrared form. 7. A system as claimed in any of claim 5 or 6 wherein said at least one of subsidiary base, stations is provided with said timing generating means, and said master base station is provided with detecting means for detecting failure of said timing generating means. A frame synchronization method substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. A TDMA/TDD mode communication network system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. Dated

Full Text

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION
This present invention relates to a frame synchronization method and also to a communication network system which establishes synchronization of phases of control signal cycles among a plurality of base stations employing a Time Division Multiple Access / Time Division Duplex (TDMA/ TDD) method.
DESCRIPTION OF THE PRIOR ART
Figure 7, for example, depicts a configuration of a base station disclosed in Japanese Patent Laid-Open Publication No. Hei 04-94226. A network control unit 301 is connected to a "Public, Switched Telephone Network (PSTN) or Private Branch exchange (PBX) or the like which are not shown in Figure 7. A codec converter 302, which has connections with a buffer memory 303 and a clock oscillator circuit 304, is connected to the network control unit 301 A communication control unit 305 which is connected to the network control unit 301 has connections with a TDMA/TDD processor 306, a transmitter unit 310, and a receiver unit 320 Both the transmitter and receiver units are connected to an antenna 330 via an antenna switch 340. A power supply unit 350 is connected to the clock oscillator circuit 304 where a clock based on a frequency of commercial power supply line (50 Hz or 60 Hz) is provided.
The transmitter unit 310 comprises a modulator 311, a transmitter 312, and a synthesizer 313, whereas the receiver
unit 320 comprises a receiver 321, a demodulator 322, and a synthesizer 323.
An explanation of the action of the above mentioned base station will next be given
At the network control unit 301, in a reverse direction from a base station to a mobile station, a signal transmitted from the network is supplied in a burst mode and this input burst signal is divided into a control signal and a communication signal.
In this reverse direction, the communication signal from the network divided by the network control unit 301 is supplied to the codec A/D converter 302. The codec converter 302 executes analogue conversion of the communication signal such as coded voice signal from the network.
In the reverse direction, an analogue-converted communication signal is supplied in a burst mode into the buffer memory 303. The buffer memory 303 temporarily stores the supplied communication signal
The clock oscillator circuit 304 generates a timing pulse which is referred to by transmission clocks for both this base station and the mobile station accessing the base station. This timing pulse is generated individually at each base station
To the clock oscillator circuit 304, a clock is supplied based on the frequency of the commercial power supply (perhaps 50 Hz or 60 Hz), from the power supply unit 350 that provides local power to this base station The clock is produced by multiplication or division the frequency of the commercial
ppwer supply. Based on this given clock, the clock oscillator circuit 304 generates and then sends out a timing pulse which establishes synchronization between each of the base stations
The communication control unit 305 is connected to the network control unit 301, and to the buffer memory 303 by way of the TDMA/TDD processor 306 In the reverse direction, both the control signal from the network which was divided by the network control unit 301 and the communication signal stored in the buffer memory 303 are given to the communication control unit 305. When the control signal from the network is given, the communication control unit 305 searches an idle channel and provides the mobile station with a terminating traffic signal including information of the searched idle channel to negotiate establishment of a channel that will be used for communication
In the reverse direction, the timing pulse from the clock oscillator circuit 304, the communication signal from the buffer memory 303 and the control signal from the communication control unit 305 are provided to the TDMA/TDD processor 306. In the forward direction from a mobile station to a base station, a transmission signal from the mobile station received by a later-described receiver unit 320 is supplied to the TDMA/TDD processor 306.
In the reverse direction, based on the communication signal and the control signal from the buffer memory 303 and the communication control unit 305, the TDMA/TDD processor determines a content of both a channel burst signal and a TDMA/TDDMA frame to transmit a signal to the mobile station.
Based on the timing of the timing pulse from the clock oscillator circuit 304, the TDMA/TDD processor 306 supplies the transmission signal for a mobile station comprising the determined TDMA/TDDMA frame, in a burst mode, to a later-described transmitter unit 310. At the same time, TDMA/TDD processor 306 sends a transmission start signal to the transmitter unit 310 to order an activation of transmission.
In the forward direction, among signals from the mobile station received by the later-described receiver unit 320, this TDMA/TDD processor 306 sends out a control signal to the communication control unit 305 and a communication signal to the buffer memory 303. The TDMA/TDD 306 also monitors the received transmission signal I e., the frame synchronization signal in the channel burst signal, by a frame synchronization detector circuit (not shown in Figure 7) placed in the TDMA/TDD processor 306.
In the forward direction the buffer memory 303 where the communication signal from the TDMA/TDD processor 306 is supplied, stores this communication signal temporarily and sends it out in a burst mode to the network control unit 301.
On the other hand, the communication control unit 305 where the control signal from the mobile station is received through the TDMA/TDD processor 306, determines, using this control signal, a channel for communication signal transmission which will be used between the base station itself and the mobile station. Then it notifies the TDMA/TDD 306 of the determined channel.
Accordingly, the TDMA/TDD processor 306 which received the channel notification notifies a carrier frequency of the determined channel to the transmitter unit 310 and the receiver unit 320 which execute radio transmission and reception.
At the transmitter unit 310, the modulator 311 is connected to the TDMA/TDD processor 306 and modulates the transmission signal from the TDMA/TDD processor 306 The transmitter 312 is connected to this modulator 311, and sends out the modulated signal to the mobile station via the antenna 330 and a mobile radio circuit (not shown in Figure 7).
On the other hand, in the receiver unit 320, a transmission signal from the mobile station via the antenna 330 and a mobile radio circuit (not shown in Figure 7) is supplied to the receiver 321 The receiver 321 detects a reception level of the received transmission signal from the mobile station, and notifies this to the TDMA/TDD processor 306 as an electric field detection signal. The demodulator 322 is connected to the receiver 321 and sends out to the TDMA/TDD processor 306 a digital signal which was demodulated from the transmission signal from the mobile station
The antenna switch 340 exists between the antenna 330 and both the transmitter 312 and the receiver 321, and switches a connection to either the transmitter 312 or the receiver 321
This antenna switch 340 switches the status of the base stations to transmission or reception in accordance with a timing of an area of reverse or forward direction communication in the TDMA/TDDMA frame in the mobile radio
channel. Normally in order to receive a control signal it is switched to the receiver 321 so that it receives a signal at a fixed carrier.
A transmission start signal from the TDMA/TDD processor 306 is sent to both the antenna switch 340 and the receiver 321. Based on this transmission start signal, the antenna switch 340 switches its connection to the transmitter 312, and the transmitter 312 sends out the transmission signal from the TDMA/TDD processor 306 via the modulator 311 to the mobile station.
The synthesizer 313 and 323 which oscillate at a variable frequency are connected to the transmitter 312 and the receiver 321 respectively Both the transmitter 312 and the receiver 321 can discretionally change a frequency of transmission or reception at the transmitter 312 or the receiver 321 based on the order of the communication control unit 305
Each synthesizer 313 or 323, if the base station is in a stand-by status, oscillates by a control of the communication control unit 305 at a frequency so that the transmitter 312 and the receiver 321 can always execute transmission or reception matching a control signal to a fixed carrier for transmission. They change frequency according to that of an idle channel to transmit communication signal when they are in communication with the network.
Each synthesizer 313 or 323 as well as the TDMA/TDD processor 306 receive from the network control unit 305 the result of channel selection for communication signal
transmission The frequency is changed in accordance with this selection result.
Having a configuration of the prior art base stations, an additional judgment circuit to distinguish 50 Hz from 60 Hz is necessary in order to synchronize phases between base stations to the one of the commercial power supply line. This judgment circuit is placed in the clock oscillator circuit 304 and judges if a signal from the power supply unit is 50 Hz or 60 Hz by the frequency of the signal. Based on this judgment, the clock oscillator circuit multiples the signal from the power supply unit and generates a certain reference timing pulse. In this instance, the base station automatically judges if the power supply is 50 Hz or 60 Hz without set up on activation
The prior art base stations have possibilities of a control channel conflict depending on a situation of signal transmission route Each clock oscillator circuit 304 in each station generates a timing pulse respectively. The timing pulse is generated by multiplying a signal from the power supply unit. If all multiplying circuit work accurately, there will be no problem. However, in reality, there exist small errors and accumulation of these errors causes a conflict of timing slots and consequently a control channel conflict can occur. Besides, upon activation of transmission, each base station searches an idle channel for communication at a same time and a time slot of a same channel can be selected . In this case control channels conflict.
SUMMARY OF THE INVENTION
This invention is created to solve the above-described problems and its purpose is to obtain a frame synchronization method and a device which can synchronize phases with certainty by transmitting a signal from a master base station to a subsidiary base station.
To achieve these objects, the frame synchronization method related to this invention includes the steps of transmitting a control channel transmission timing signal generated at the master base station to a TDMA/TDD mode subsidiary base station through commercial power supply line, and of generating a control channel transmission timing based on the received timing signal at the subsidiary base station.
By this method, synchronization of control signal phases between the master and the subsidiary base stations can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal from the master base station via commercial power supply line.
Another aspect of the frame synchronization method related to this invention is characterized by a frame synchronization method wherein a control channel transmission timing generator by a base station is converted into a timing signal, and wherein this timing signal is transmitted to a TDMA/TDD mode subsidiary base station using a radio wave or an infrared, and wherein the subsidiary base station generates a control channel transmission timing based on the timing signal
In this method, a synchronization of phases of control signals between the master base station and the subsidiary
base station can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal provided by the master base station in the form of a radio wave or an infrared signal
Another aspect of the frame synchronization method related to this invention is characterized by a frame synchronization method wherein a control channel transmission timing generated by a base station is converted into a timing signal, and wherein this timing signal is transmitted to a TDMA/TDD mode subsidiary base station using a communication channel, and wherein said subsidiary base station generates a control channel transmission timing based on said timing signal.
In this method, synchronization of phases of control signals between the master base station and the subsidiary base station can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal provided by the master base station via a communication channel.
A communication network system related to this invention is a communication network system of TDMA/TDD mode involving a master base station and at least one subsidiary base station wherein said master base station generates a timing signal based on a control channel transmission timing, and has a timing generator which supplies this timing signal to commercial power supply line, and wherein said subsidiary base station has a timing receiver which generates a control channel transmission timing based on the timing signal from the commercial power supply line, and wherein frame
synchronization between the master base station is established and the subsidiary base station is established based on said timing signal supplied through the commercial power supply line.
In this system, a synchronization of phases of control signals between a master base station and a subsidiary base station can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal provided by the master base station via commercial power supply line.
A further aspect of a communication network system related to this invention is a communication network system of TDMA/TDD mode comprising a master base station and at least one subsidiary base station wherein said master base station includes a timing generator which generates an electric timing signal based on a control channel transmission timing and means for transmitting said electric timing signal generated by said timing generator in a form of a radio wave or an infrared beam, and wherein said subsidiary base station includes means for receiving said signal in a form of a radio wave or an infrared beam and converting it into an electric timing signal, and a timing receiver which generates a control channel transmission timing based on said timing signal received by said receiving means, and wherein frame synchronization between said master base station and said subsidiary base station is done based on said timing signal transmitted or received as a signal in a form of a radio wave or an infrared beam
In this system, synchronization of phases of control signal between the master base station and the subsidiary base station can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal provided by the master base station in the form of a radio wave or an infrared beam
A still further aspect of a communication network system related to this invention is a TDMA/TDD mode communication network system comprising a master base station and at least one subsidiary base station wherein said master base station has a timing generator which generates a timing signal based on a control channel transmission timing and supplies said timing signal to a communication channel, and wherein said subsidiary base station has a timing receiver which generates a control channel transmission timing based on said timing signal received from said communication channel, and wherein frame synchronization between said master base station and said subsidiary base station can be done based on said timing signal transmitted via said communication channel
In this system, synchronization of phases of control signals between the master base station and the subsidiary base station can be established, since the subsidiary base station can generate a control channel transmission timing based on the timing signal provided by the master base station via a communication channel.
Accordingly, the present invention relates to a frame synchronization method comprising the steps of
converting a control channel transmission timing generated by a master base station into a timing signal,
transmitting said timing signal to at least one subsidiary base station of TDMA/TDD mode via commercial power supply line, and
generating a control channel transmission timing based on said timing signal at said subsidiary base station
The present invention also relates to a frame synchronization method comprising the steps of
converting a control channel transmission timing generated by a master base station into a timing signal,
transmitting said timing signal to at least one subsidiary base station of TDMA/TDD mode using a radio wave or an infrared, and
generating of a control channel transmission timing based on said timing signal at said subsidiary base station
The present invention also relates to a frame synchronization method comprising the steps of
converting a control channel transmission timing generated by a master base station into a timing signal,
transmitting said timing signal to at least one subsidiary base station of TDMA/TDD mode through communication line, and
generating a control channel transmission timing based on said timing signal at said subsidiary base station
The present invention also relates to a TDMA/TDD mode communication network system comprising a master base station and at least one subsidiary base station wherein
said master base station is provided with a timing generating means which generates a timing signal based on a control channel transmission timing and supplies said timing signal to a commercial power supply line, and wherem
said subsidiary base station is provided with a timing receiving means which generates a control channel transmission timing based on said timing signal received from said commercial power supply line, and
frame synchronization between said master base station and said subsidiary base station is established based on said timing signal transmitted via said commercial power supply line
The present invention also relates to a communication network system of TDMA/TDD mode comprising a master base station and at least one subsidiary base station wherein
said master base station includes a timing generating means which generates an electnc timing signal based on a control channel transmission timing and means for transmitting said electnc timing signal generated by said timing generating means in radio or infrared form, and wherein
said subsidiary base station includes receiving means for receiving said signal in a form of a radio wave or an infrared and converting it into an electric timing signal, and a timing receiving means which generates a control channel transmission timing based on said timing signal received by said receiving means, and
a frame synchronization between said master base station and said subsidiary base station is established based on said timing signal transmitted or received as a signal in radio or infrared form
The present invention also relates to a TDMA/TDD mode communication network system comprising a master base station and at least one subsidiary base station wherein
said master base station is provided with a timing generating means which generates a timing signal based on a control channel transmission timing and supplies said timing signal to a communication channel, and wherein
said subsidiary base station is provided with a tuning receiving means which generates a control channel transmission timing based on said timing signal received from said communication channel, and
frame synchronization between said master base station and said subsidiary base station is established based on said timing signal transmitted via said communication channel BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 is a diagram showing configurations of a master
base station and a subsidiary base station used in the present invention.
Figure 2 is a diagram showing a configuration of a timing generator used in this invention.
Figure 3 is a diagram showing a configuration of a timing receiver used in this invention
Figure 4 is a timing chart of timing signals used in this invention.
Figure 5 is a diagram showing configurations of a master base station and a subsidiary base station in accordance with another embodiment of the present invention.
Figure 6 is a diagram showing configurations of a master base station and a subsidiary base station in accordance with another embodiment of the present invention.
Figure 7 is a diagram showing a configuration of a base station used in the prior art.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1
Figure 1 is a diagram showing configurations of a master base station and a subsidiary base station in which the frame synchronization method described in embodiment 1 of this invention is applied. In embodiment 1, a control channel transmission timing generated at a master base station 1 is converted into a pulse signal P (see Figure 4) and is transmitted through commercial power supply line 100 to a subsidiary base station 2 of a TDMA/TDD mode. The master base station 1 comprises an antenna switch (ANT-SWITCH) 11-1, a
transmitter 12-1, a receiver 13- 1, a TDMA/TDD processor 14-1, a Central Processing Unit (CPU) 15-1, a codec Analogue to Digital (A/D) converter 16-1, a network control unit 17-1, a power supply unit 18-1, and a timing generator 19-1 which is connected to the power supply unit. The power supply unit is connected to commercial power supply line 100.
Figure 2 shows a configuration of the timing generator 19-1. As is shown in Figure 2, the timing generator 19-1 comprises a reference clock generator circuit 21-1 which generates a reference clock, a frame clock generator 22-1, and a signal converter 23-1. Based on a reference clock given by the reference clock generator circuit 21-1, the frame clock generator 22-1 generates one frame clock made of a transmission frame TX and a reception frame RX in Figure 4. With control channel transmission timing which is a timing to switch the generated transmission frame TX and the reception frame RX, the TDMA/TDD processor 14-1 and the codec A/D converter 16-1 process data. The control channel transmission timing is converted into a pulse signal P at the signal converter 23-1, and supplied to the commercial power supply line 100 via the power supply unit 18-1.
The subsidiary base station 2 in Figure 1 comprises an antenna switch 11-2, transmitter 12-2, a receiver 13-2, a TDMA/TDD processor 14-2, a CPU 15-2, a codec A/D converter 16-2, a network control unit 17-2, a power supply unit 18-2, and a timing receiver 19-2 which is connected to the power supply unit. The power supply unit 18-2 is connected to a commercial power supply line 100.
Figure 3 is a diagram showing a configuration of the timing receiver 19-2. The timing receiver 19-2 comprises a reference clock generator circuit 21-2, a frame clock generator unit 22-2, and a signal converter 23-2. The signal converter 23-2 generates a control channel transmission timing based on a received pulse signal from commercial power supply line 100 by way of the power supply unit 18-2, whereas the frame clock generator unit 22-2 generates a frame clock based on the control channel transmission timing and the reference clock. The TDMA/TDD processor 14-2 and the codec A/D converter 16-2 process data signals based on the frame clock and control channel transmission timing.
An illustration of the embodiment follows.
The network control unit 17-1 in the master base station 1 is connected to Public Switched Telephone Network (PSTN) 102 and controlled by the CPU 15-1. A data signal given to this network control unit is converted by the codec A/D converter 16-1 and supplied to the TDMA/TDD processor 14-1. This TDMA/TDD processor 14-1 supplies the data signal to transmitter 12-1 based on a timing signal from the timing generator 19- 1. The data signal is transmitted from an antenna A-l via the antenna switch ANT-SW 11-1.
On the other hand, data signal received by this antenna A-l is given to the receiver 13-1 via the antenna switch 11-1 and then sent to the PSTN 102 in a route which is a reversal of transmission process described above
The network control unit 17-2 in the subsidiary base station 2 is connected to the PSTN 102 and controlled by the
CPU 15-2. A data signal input to the network control unit 17-2 is converted by the codec A/D converter 16-2 and supplied to the TDMA/TDD processor 14-2. This TDMA/TDD processor 14-2 supplies the data signal to transmitter 12-2 based on a timing signal from the timing receiver 19-2. The data signal is transmitted from an antenna A-2 via the antenna switch ANT-SW 11-2.
On the other hand, data signal received by this antenna A-2 is given to the receiver 13-2 via the antenna switch 11-2 and then sent to the PSTN 102 in a route which is a reversal of transmission.
In embodiment 1 described above, a timing signal generated by the timing generator 19-1 in the master base station 1 is sent to each subsidiary base station 2 through the commercial power supply line 100. At each subsidiary base station 2, the timing receiver 19-2 generates a control channel transmission timing based on the previously-described timing signal. This enables synchronization between the master base station 1 and the subsidiary base station 2 with certainty. Therefore, unlike the prior method in which each station individually sets timing based on the frequency of the commercial power supply, in this method conflicts of timing slot and the like are avoidable.
It is also possible in embodiment 1 for any subsidiary base station 2 to function as a new master base station, replacing the master base station 1 in case of possible failure of the timing generator 19-1. In this case, the subsidiary base station 2 replacing the master base station 1 sends out a
reference timing signal to commercial power supply line 100 using a previously established timing generator. A diagnosis of a failure in the master base station 1 can be made by a known failure diagnostic function
In embodiment 1 it is also preferable for each station to decide in advance an order of idle channel search at a time of transmission activation. One way to accomplish this is that the master base station 1 searches an idle channel first, followed by each subsidiary station sequentially, following an order from the master base station 1. In this way, multiple selection a time slot of the same channel at the same time can be avoided with certainty Another method is to set timings of idle channel search by the master base station 1 and the subsidiary base station 2 in advance In this way, a control channel conflict in the prior art can be avoided
Embodiment 2
In embodiment 2, a control channel transmission timing generated by the timing generator 19-1 in the master base station 1 is converted into a tone signal T which is shown in Figure 4, and this tone signal T is then sent out as a timing signal to commercial power supply line 100 via power supply unit 18-1. On the other hand, at the subsidiary base station 2, control channel transmission timing is generated in the timing receiver 19-2 using the tone signal T input to the power supply unit 18-2 via commercial power supply line 100, and a frame clock is then generated based on this timing
Embodiment 3
In embodiment 3, a control channel transmission timing generated by the timing generator 19-1 in the master base station 1 is converted into a frame synchronization signal F m spread spectrum which is shown m Figure 4, and this frame synchronization signal F in spread spectrum is then sent out as a timing signal to a commercial power supply line 100 via power supply unit 18-1. On the other hand, at the subsidiary base station 2, a control channel transmission timing is generated by the timing receiver 19-2 using the spread spectrum synchronization signal F given to the power supply unit 18-2 via the commercial power supply line 100, and a frame clock is then generated based on this timing.
Embodiment 4
In embodiment 4, a control channel transmission timing generated by the timing generator 19-1 at the master base station 1 is converted into a frame synchronization and data signal FD which is shown in Figure 4, and this frame synchronization and data signal FD is then sent out as a timing signal to commercial power supply line 100 via power supply unit 18-1. On the other hand, at the subsidiary base station 2, a control channel transmission timing is generated by the timing receiver 19-2 using the frame synchronization and data signal FD given to the power supply unit 18-2 via the commercial power supply line 100, and a frame clock is then generated based on this timing.
Embodiment 5
In embodiment 5, a control channel transmission timing generated by the timing generator 19-1 in the master base station 1 is converted into a voltage signal V shown in Figure 4 using a voltage converter circuit (not shown in Figure 1), and then this voltage signal V is sent out as a timing signal to commercial power supply line 100 via the power supply unit 18-1. On the other hand, at the subsidiary base station 2, control channel transmission timing is generated by the timing receiver 19-2 using the voltage signal V given to the power supply unit 18-2 via commercial power supply line 100, and then a frame clock is generated based on this timing.
In the above described embodiments 2 to 5, the tone signal T, the frame synchronization signal F, the frame and data signal FD, and the voltage signal V are transmitted respectively as a timing signal from the master base station 1 to the subsidiary base station 2 through the commercial power supply line 100, and synchronization between base stations can be controlled with certainty by the timing signal.
Embodiment 6
Figure 5 is a diagram showing configurations of a master base station and a subsidiary base station in accordance with another embodiment of the present invention. In embodiment 6, a control channel transmission timing generated by a base station 1 is converted into a pulse signal P (see Figure 4) and transmitted to a subsidiary base station 2 using a radio wave or an infrared 101 as a medium. The master base station
1 comprises an antenna switch 41-1, a transmitter unit 42-1, a receiver unit 43-1, a TDMA/TDD processor 44-1, a CPU 45-1, a codec A/D converter 46-1, a network control unit 47-1, a power supply unit 48-1, and a timing generator 49-1 connected to the transmitter unit 42-1.
The subsidiary base station comprises an antenna switch 41-2, a transmitter 42-2, a receiver 43-2, a TDMA/TDD processor 44-2, a CPU 45- 2, a codec A/D converter 46-2, a network control unit 47-2, a power supply unit 48-2, and a timing receiver 49-2 connected to the receiver 43-2.
Configurations of the timing generator 49-1 and the timing generator 49-2 are the same as for respective timing generator 19-1 and the timing receiver 19-2 in Figures 2 and 3 of embodiment 1. However, in this embodiment 6, a signal from the timing generator 49-1 is sent out to the transmitter 42-1 and then transmitted from the antenna A-l via the antenna switch 41-1. A signal is given to the timing receiver 49-2 from the receiver 43-2 through the antenna A-2 and the antenna switch 41-2.
An example of this embodiment follows
The network control unit 47-1 in the master base station 1 is connected to the Public Switched Telephone Network (PSTN) 102 and controlled by the CPU 45-1 A data signal given to this network control unit is converted by the codec A/D converter 46-1 and supplied to the TDMA/TDD processor 44-1. This TDMA/TDD processor 44-1 supplies the data signal to the transmitter 42-1 based on a timing signal from the timing generator 49-1. The data signal is transmitted as a signal in
a form of a radio wave or an infrared, from the antenna A-l via the antenna switch ANT-SW 41-1.
On the other hand, the data signal received by this antenna A-l is given to the receiver 43-1 via the antenna switch 41-1 and then sent to the PSTN 102 in a route which is a reversal of transmission.
The network control unit 47-2 in the subsidiary base station 2 is connected to the PSTN 102 and controlled by the CPU 45-2. A data signal given to the network control unit 47-2 is converted by the codec A/D converter 46-2 and supplied to the TDMA/TDD processor 44-2. The TDMA/ TDD processor 44-2 sends the data signal to the transmitter 42-2 based on the timing signal from the timing receiver 49-2, and then transmits it as a signal in a form of a radio wave or an infrared, from the antenna A-2 via the antenna switch 41-2
The data signal received by the antenna A-2 is given to the receiver 43-2 via the antenna switch 41-2 and then sent to the PSTN 102 in a reverse route from transmission
Hence, in this embodiment 6, the timing signal generated by the timing generator 49-1 is transmitted from the antenna as a signal in a form of a radio wave or an infrared beam. This signal is received by each subsidiary base station 2 and a timing signal separated from a data signal is supplied from the receiver 43-2 to the timing receiver 49-2 of the subsidiary base station 2 Synchronization between station 1 and station 2 can be established as in the above and, as a result, undesirable phenomena such as channel conflicts can be prevented with certainty
Embodiment 7
In embodiment 7, a control channel transmission timing generated by the timing generator 49-1 in the master base station 1 is converted into a tone signal T shown in Figure 4. The tone signal T is sent out to the transmitter 42-1 as a timing signal via the antenna switch 41-1, and sent out from the antenna A-l as a signal 101 in a form of a radio wave or an infrared. On the other hand, in the subsidiary base station 2, the tone signal T sent as a signal 101 in a form of a radio wave or an infrared is received by the antenna A-2. It is then sent to the timing receiver 49-2 via the antenna switch 41-2 and the receiver 43-2. The timing receiver 49-2 generates a control channel transmission signal based on this tone signal T , and a frame clock is generated based on this timing.
Embodiment 8
In embodiment 8, a control channel transmission timing generated at the timing generator 49-1 in the master base station 1 is converted into a spread spectrum frame synchronization signal F shown in Figure 4. The spread spectrum frame synchronization signal F is sent out to the transmitter 42-1 as a timing signal via the antenna switch 41-1, and sent out from the antenna A-l as a signal 101 in a form of a radio wave or an infrared. On the other hand, in the subsidiary base station 2, the spread spectrum frame synchronization signal F sent as a signal 101 in a form of a radio wave or an infrared is received by the antenna A-2 It
is then sent to the timing receiver 49-2 via the antenna switch 41-2 and the receiver 43-2 The timing receiver 49-2 generates a control channel transmission signal based on this spread spectrum frame synchronization signal F, and frame clock is generated based on this timing
Embodiment 9
In embodiment 9 a control channel transmission timing generated at the timing generator 49-1 in the master base station 1 is converted into a frame synchronization and data signal FD shown in Figure 4. The frame synchronization and data signal FD is sent out to the transmitter 42-1 as a timing signal via the antenna switch 41-1, and from the antenna A-l as a signal 101 in the form of a radio wave or an infrared beam. On the other hand, in the subsidiary base station 2, the frame synchronization and data signal FD sent as a signal 101 in the form of a radio wave or an infrared beam is received by the antenna A-2. It is then sent to the timing receiver 49-2 via the antenna switch 41-2 and the receiver 43-2. The timing receiver 49-2 generates a control channel transmission signal based on this frame synchronization and data signal FD, and frame clock is generated based on this timing.
As described above, in embodiments 7, 8, and 9, the timing signal is converted into the tone signal T, the frame synchronization signal F, and the frame synchronization and data signal FD, respectively. Since this timing signal is sent from the master base station 1 to the subsidiary base
station 2 as a signal 101 in radio or infrared form, synchronization between each of stations can established with certainty.
Embodiment 10
Figure 6 is a diagram showing a system configuration related to embodiment 10 In embodiment 10, in order to synchronize phases of base stations which are not reachable by radio waves, a control channel transmission timing generated by the master base station 1 is converted into a pulse signal P (see Figure 4) or other form of signal, and then sent to the subsidiary base station 2 via the PSTN 102 as a communication channel. A master base station 1 comprises an antenna switch 51-1, a transmitter 52-1, a receiver 53-1, a TDMA/TDD processor 54-1, a CPU 55-1, a codec A/ D converter 56-1, a network control unit 57-1, a power supply unit 58-1, and a timing generator 59-1 connected to the codec A/D converter 56-1.
A subsidiary base station 2 comprises an antenna switch 51-2, a transmitter 52-2, a receiver 53-2, a TDMA/TDD processor 54-2, a CPU 55- 2, a codec A/D converter 56-2, a network control unit 57-2, a power supply unit 58-2, and a timing receiver 59-2 which is connected to the codec A/D converter 56-2.
Configurations of the timing generator 59-1 and the timing receiver 59- 2 are the same as for the timing generator 19-1 and the timing receiver 19-2 in Figures 2 and 3 of embodiment 1. In this embodiment 10, a timing signal from the timing
generator 59-1 is sent out to the codec A/D converter 56-1, and then to the PSTN 102 via the network control unit 57-1. A timing signal is supplied to the timing receiver 59-2 through the PSTN 102, the network control unit 57-2 and the codec A/D converter 56-2.
An example of this embodiment follows.
The network control unit 57-1 is connected to the PSTN 102 and controlled by the CPU 55-1. A data signal given to the network control unit 57-1 is converted by the codec A/D converter 56-1 and then supplied to the TDMA/TDD processor 54-1. The TDMA/TDD processor 54-1 sends the data signal to the transmitter 52-1 based on the timing signal of the timing generator 59-1. It then transmits the data signal from the antenna A-1 via the antenna switch 51-1.
On the other hand, a data signal received at this antenna A-1 is sent the receiver 53-1 via the antenna switch 51-1, and then sent to the PSTN 102 in a route opposite to transmission.
The network control unit 57-1 in the subsidiary base station 2 is connected to the PSTN 102 and controlled by the CPU 55-2. The data signal given to the network control unit 57-2 is converted by the codec A/D converter 56-2 and then given to the TDMA/TDD processor 54-2. This TDMA/TDD processor 54-2 sends the data signal to the transmitter 52-2 based on a timing by the timing receiver 59-2. The data signal is transmitted from the antenna A-2 via the antenna switch 51-2.
A data signal received by the antenna A-2 is sent to the receiver 53-2 via the antenna switch 51-2, and then supplied to the PSTN in a route opposite that of transmission.
In this embodiment 10, a timing signal generated by the timing generator 59-1 is sent to the network control unit 57-1 via the codec A/ D converter 56-1, and then to the PSTN with a data signal. At each subsidiary base station 2, the signal received by the network control unit 57-2 through the PSTN is divided into the data signal and the timing signal The separated timing signal is sent from the codec A/D converter 56-2 to the receiver 59-2, and then used as the timing signal for the subsidiary base station 2. Therefore, by this timing signal the master base station 1 and the subsidiary base station 2 can establish synchronization with certainty.
The master base station 1 is also always monitoring traffic of PSTN at the CPU 55-1. If it judges that the traffic is less than a prescribed threshold value, it connects a channel to a subsidiary base station 2 and sends out a timing signal. In this case, since the channel is not always open, gradual phase shift can occur, and a phase jump is possible upon synchronization of phases To prevent this, it is preferable for the reference clock oscillator circuits 21-1 and 21-2 of the timing generator 59-1 and the timing receiver 59-2 to have circuits with highly accurate original oscillation frequency.
Embodiment 11
In embodiment 11, a control channel transmission timing generated by the timing generator 59-1 in the master base station 1 is converted into a tone signal T shown in Figure 4. The tone signal T is then converted into a voice signal and
sent to the PSTN 102 from the network control unit 57-1 In the subsidiary base station 2, a control channel transmission timing is generated at by the timing receiver 59-2 based on the tone signal T given to the network control unit 57-2 from the PSTN. A frame clock is generated by this timing
Embodiment 12
In embodiment 12, a control channel transmission timing generated by the timing generator 59-1 in the master base station 1 is converted into a spread spectrum frame synchronization signal F shown in Figure 4. The spread spectrum frame synchronization signal F is then converted into a voice signal and sent to the PSTN 102 from the network control unit 57-1. In the subsidiary base station 2, a control channel transmission timing is generated at by the timing receiver 59-2 based on the spread spectrum frame synchronization signal F given to the network control unit 57-2 from the PSTN. A frame clock is generated by this timing.
Embodiment 13
In embodiment 13, a control channel transmission timing generated by the timing generator 59-1 in the master base station 1 is converted into a frame synchronization and data signal FD shown in Figure 4. The frame synchronization and data signal FD is then converted into a voice signal and sent to the PSTN 102 from the network control unit 57-1. In the subsidiary base station 2, a control channel transmission
timing is generated at by the timing receiver 59-2 based on the frame synchronization and data signal FD given to the network control unit 57- 2 from the PSTN A frame clock is generated by this timing.
As described above, in embodiments 11, 12, and 13, a timing signal is sent to the PSTN as a tone signal T, or a frame synchronization signal F, or a frame synchronization and data signal FD, respectively. Synchronization between the master base station 1 and the subsidiary base station 2 can be established using this timing signal.
In these embodiments above, a control channel transmission timing is converted into any signal of a pulse, a tone, a frame synchronization, or a frame and data It is then sent out through any medium of commercial power supply line 100, a radio wave or an infrared beam 101, or the PSTN 102 as communication line. Signals other than the ones described above can be used in the same way as in these embodiments, as long as they can be transmitted as described above.
Further, if both the master base station 1 and the subsidiary base station 2 have batteries and are made as to be switched to a precise self-running clock in a case of service interruption of commercial power supply, the status before interruption can be held and restart of an action after the power supply is reestablished can be smoothly accomplished
In this invention, a master base station is assumed to synchronize timing However, it is possible for the timing generator of the master base station to be out of order. As a countermeasure of a failure of the master base station, it is
preferable for a base station previously working as a subsidiary base station to function as the base station for generating timing signals. Failure detection of the master base station can be done by self-diagnostics
Further, by deciding the order of each station's idle channel search at the time of activation of transmission, conflicts of control channel can be avoided. As one means to accomplish this, the master base station first selects a channel, then each subsidiary base station sequentially selects a channel following orders from the master base station. Another method is a prescribed timing setting of an idle channel search by each station.
While there have been described what are at present considered to be preferred embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention.

We claim:
1. A frame synchronization method to synchronize a control channel
transmission timing comprising the steps of:
converting a control channel transmission timing generated by a master base station into a timing signal;
transmitting said timing signal to at least one subsidiary base station of TDMA/TDD mode via commercial power supply line or using a radio wave or an infrared or through communication line, and
generating a control channel transmission timing based on said timing signal at said subsidiary base station.
2. A method as claimed in claim 1, wherein said timing signal is transmitted from the master base station to each subsidiary base station as a pulse signal or as a tone signal or as a spread spectrum frame synchronization signal or as a frame synchronization and data signal.
3. A method as claimed in claim 1, wherein said communication channel is a Public Switched Telephone Network (PSTN).
4. A method as claimed in claim 3, wherein said master base station is always monitoring said PSTN traffic; and said master base station connects a channel to said subsidiary base station and sends said timing signal when said traffic is less than a predetermined threshold value.
5. A TDMA/TDD mode communication network system for synchronizing a control channel transmission timing by a method as claimed
in any one of claimed comprising a master base station and at least one subsidiary base station wherein
said master base station is provided with a timing generating means which generates a timing signal based on a control channel transmission timing and supplies said timing signal to a
commercial power supply line or to a communication channel; and wherein
said subsidiary base station is provided with a timing receiving means which generates a control channel transmission timing based on said timing signal received from said commercial power supply line or from said communication channel; and
frame synchronization between said master base station and said subsidiary base station is established based on said timing signal transmitted via said commercial power supply line or via said communication channel.
6. A TDMA/TDD mode communication network system as claimed in claim 1,
comprising a master base station and at least one subsidiary base station wherein
said master base station includes a timing generating means which generates an electric timing signal based on a control channel transmission timing and means for transmitting said electric timing signal generated by said timing generating means in radio or infrared form; and wherein
said subsidiary base station includes receiving means for receiving said signal in a form of a radio wave or an infrared and converting it into an electric timing signal, and a timing receiving means which generates a control channel transmission timing based on said timing signal received by said receiving means; and
a frame synchronization between said master base station and said subsidiary base station is established based on said timing signal transmitted or received as a signal in radio or infrared form.

7. A system as claimed in any of claim 5 or 6 wherein
said at least one of subsidiary base,
stations is provided with said timing generating means, and said
master base station is provided with detecting means for detecting
failure of said timing generating means. A frame synchronization method substantially as hereinbefore
described with reference to and as illustrated in the accompanying
drawings. A TDMA/TDD mode communication network system substantially
as hereinbefore described with reference to and as illustrated in
the accompanying drawings. Dated

Documents:

355-del-1997-abstract.pdf

355-del-1997-claims.pdf

355-del-1997-complete specification (as files).pdf

355-del-1997-complete specification (granted).pdf

355-del-1997-correspondence-others.pdf

355-del-1997-correspondence-po.pdf

355-del-1997-description (complete).pdf

355-del-1997-drawings.pdf

355-del-1997-form-1.pdf

355-del-1997-form-13.pdf

355-del-1997-form-19.pdf

355-del-1997-form-2.pdf

355-del-1997-form-3.pdf

355-del-1997-form-6.pdf

355-del-1997-gpa.pdf

355-del-1997-petition-137.pdf

355-del-1997-petition-138.pdf

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Patent Number

197352

Indian Patent Application Number

355/DEL/1997

PG Journal Number

31/2009

Publication Date

31-Jul-2009

Grant Date

11-Aug-2006

Date of Filing

13-Feb-1997

Name of Patentee

MITSUBISHI DENKI KABUSHIKI KAISHA

Applicant Address

2-3,MARUNOUCHI 2-CHOME, CHOME, CHIYODA-KU, TOKYO 100, JAPAN

Inventors:

#	Inventor's Name	Inventor's Address
1	SHUHEI YASUDA	C/O MITSUBISHI DENKI KABUSHIKI KAISHA OF 2-3, MARUNOUCHI 2-CHOME, CHIYODA- KU, TOKYO 100 JAPAN

PCT International Classification Number

H03M 13/29

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	HEI 8-296839	1996-11-08	Japan