JP4882734B2 - Terminal apparatus, central station apparatus, synchronization establishment system, and synchronization establishment method - Google Patents

Description

  The present invention relates to a terminal device, a central station device, a synchronization establishment system, and a synchronization establishment method, and, for example, communicates using a code division multiplexing (CDM) method between a central station and a plurality of terminal devices. Therefore, it can be applied to a method for synchronizing the transmission timing of each terminal device.

  For example, an access network system using a code division multiplexing (CDM) system can multiplex a plurality of transmission signals at the same time, and saves communication resources such as frequency or time slot, while storing a large amount of data. It has the feature that it can perform communication, and is put to practical use mainly in mobile communication.

  Among the CDM methods, a method called a synchronous CDM method has a feature that a signal of an arbitrary channel can be stably extracted from a multiplexed signal, but means for synchronizing transmission timings of a plurality of terminal devices. is necessary.

  As a conventional technique for synchronizing the transmission timings of the plurality of terminal devices, means described in Patent Document 1 can be cited.

  In Patent Document 1, an echo transmission command is sent from the central office to the terminal device, the terminal device that receives this command returns an echo, the central office receives the echo, evaluates the timing, and measures the distance. A method is described.

JP 2005-33544 A

  By the way, in general, in an access network system in which a central station and a plurality of terminal devices communicate, another terminal device participates in communication from the middle while the central station and at least one terminal device are communicating. Situations occur frequently. Such a situation is referred to as halfway participation of the terminal device.

  However, in the method described in Patent Document 1, when a certain terminal device participates midway, it is necessary to stop all data transmission / reception of the already-established terminal device. There is a problem that it is necessary to mount a large amount of memory for buffering data that arrives during the synchronization establishment period, and the apparatus cost is increased.

  Therefore, in the access network system, even when a terminal device joins midway, it is possible to establish synchronization including the halfway joined terminal device without stopping data transmission / reception of the terminal device that has established synchronization. There is a need for a synchronization establishment system and method for establishing synchronization.

  In order to solve such a problem, the terminal device of the first aspect of the present invention is a one-to-N communication system that performs communication according to a code division multiplexing method between a central station device and a plurality of terminal devices via a distribution multiplexer. In the terminal device that establishes synchronization with the central station device and participates midway, the synchronization establishment slave controls the synchronization establishment with the central station device in cooperation with the synchronization establishment main control means possessed by the central station device. Control means, and when the synchronization establishment slave control means receives the frame synchronization signal transmission permission signal from the synchronization establishment main control means of the central station apparatus, the code length is longer than the code used for encoding the transmission signal. A frame synchronization signal transmission unit for transmitting a frame synchronization signal, which has a long period that coincides with the upstream frame, the head of the code coincides with the head of the upstream frame, and has a fixed signal, and (2) a central station device Synchronization establishment A bit synchronization signal transmission unit for transmitting a bit synchronization signal including a fixed signal during a non-signal period constituting a frame when a bit synchronization signal transmission permission signal is received from the control means; When receiving the phase shift amount information of the transmission phase related to frame synchronization from the control means, or when receiving the optimal transmission phase, the phase shift amount information of the transmission phase related to frame synchronization, or the above-mentioned optimal transmission And a transmission phase control unit that adjusts the transmission phase according to the phase.

  A central station apparatus according to a second aspect of the present invention is a central station apparatus that is a component of a one-to-N communication system that performs communication according to a code division multiplexing method between a central station apparatus and a plurality of terminal apparatuses via a distribution multiplexer. And a synchronization establishment main control means for controlling synchronization establishment with each terminal device in cooperation with the synchronization establishment slave control means possessed by each terminal device, wherein the synchronization establishment main control means is (1) A frame synchronization signal transmission permission signal transmitting unit that transmits a frame synchronization signal transmission permission signal to the terminal device; and (2) receiving a frame synchronization signal from a terminal device that participates midway, and fixing the received frame synchronization signal. Based on the spread demodulation output in the signal period, the phase shift amount information of the transmission phase related to the frame synchronization of the terminal device is obtained, and the phase shift amount information of the transmission phase related to the frame synchronization is transmitted to the terminal device participating in the middle A synchronization execution unit; (3) a bit synchronization signal transmission permission signal transmission unit that transmits a bit synchronization signal transmission permission signal including phase shift amount information related to bit synchronization to a terminal device that participates in the middle; Based on the spread demodulation output of the fixed signal period in the bit synchronization signal received from the participating terminal device, when it is determined that the signal of the transmission phase has been received effectively, the optimal transmission phase is determined, And a bit synchronization execution unit configured to transmit to the terminal device and set as a synchronization phase.

  A synchronization establishment system according to a third aspect of the present invention is a 1-to-N communication system in which a central station apparatus and a plurality of terminal apparatuses communicate via a distribution multiplexer according to a code division multiplexing system. In a synchronization establishment system that establishes synchronization with devices, the central station device has synchronization establishment main control means for controlling synchronization establishment of each terminal device, and each terminal device cooperates with synchronization establishment main control means And (A) synchronization establishment main control means (1) frame synchronization signal transmission for transmitting a frame synchronization signal transmission permission signal to a terminal device participating in the middle And (2) receiving a frame synchronization signal from a terminal device participating in the middle, and based on the spread demodulation output of the fixed signal period in the received frame synchronization signal, relating to the frame synchronization of the terminal device Sending A frame synchronization execution unit that obtains phase phase shift amount information and transmits the phase shift amount information of the transmission phase related to the frame synchronization to the halfway participating terminal device; and (3) bit synchronization for the halfway participating terminal device. A bit synchronization signal transmission permission signal transmission unit for transmitting a bit synchronization signal transmission permission signal including phase shift amount information according to (4), and a spread demodulation output of a fixed signal period in a bit synchronization signal received from a terminal device participating midway And a bit synchronization execution unit that determines an optimal transmission phase and transmits it to a terminal device that participates midway and sets it as a synchronization phase when it is determined that the signal of that transmission phase has been received effectively. (B) When the synchronization establishment slave control means receives (1) the frame synchronization signal transmission permission signal, the code length is longer than the code used for encoding the transmission signal and has a period matching the upstream frame. Shi A frame synchronization signal transmission unit for transmitting a frame synchronization signal having a fixed signal and a head of the code coincides with the head of the upstream frame; and (2) a frame is formed when the bit synchronization signal transmission permission signal is received. When a bit synchronization signal transmission unit that transmits a bit synchronization signal including a fixed signal and (3) phase shift amount information of a transmission phase related to frame synchronization is received or an optimum phase is received during a no-signal period And a transmission phase control unit for adjusting the transmission phase.

  A synchronization establishment method according to a fourth aspect of the present invention is a 1-to-N communication system in which communication is performed according to a code division multiplexing method between a central station apparatus and a plurality of terminal apparatuses via a distribution multiplexer. In a synchronization establishment method for establishing synchronization with a device, the central station device has synchronization establishment main control means for controlling synchronization establishment of each terminal device, and each terminal device cooperates with synchronization establishment main control means And (A) synchronization establishment main control means (1) frame synchronization signal transmission for transmitting a frame synchronization signal transmission permission signal to a terminal device participating in the middle And (2) receiving a frame synchronization signal from a terminal device participating in the middle, and based on the spread demodulation output of the fixed signal period in the received frame synchronization signal, relating to the frame synchronization of the terminal device Transmission phase A frame synchronization execution step of obtaining phase shift amount information and transmitting the phase shift amount information of the transmission phase related to the frame synchronization to the terminal device participating midway; and (3) relating to bit synchronization to the terminal device participating midway. Based on a bit synchronization signal transmission permission signal transmission step for transmitting a bit synchronization signal transmission permission signal including phase shift amount information, and (4) a spread demodulation output in a fixed signal period in the bit synchronization signal received from a terminal device participating midway When determining that the signal of the transmission phase has been received effectively, the optimum transmission phase is determined, transmitted to the terminal device participating in the middle, and has a bit synchronization execution step for setting as a synchronization phase, (B) When the synchronization establishment slave control means receives (1) a frame synchronization signal transmission permission signal, the code length is longer than the code used for encoding the transmission signal and has a period that matches the upstream frame. A frame synchronization signal transmission step of transmitting a frame synchronization signal having a fixed signal and the head of the code matching the head of the upstream frame; and (2) forming a frame when the bit synchronization signal transmission permission signal is received. When receiving a bit synchronization signal transmission step for transmitting a bit synchronization signal including a fixed signal and (3) phase shift amount information of a transmission phase related to frame synchronization, or when receiving an optimum phase during a no-signal period And a transmission phase control step of adjusting the transmission phase.

  According to the terminal device, the central station device, the synchronization establishment system, and the synchronization establishment method of the present invention, in the access network system, even when the terminal device participates in the middle, data transmission / reception of the terminal device that is establishing synchronization is performed. Without stopping, it is possible to establish synchronization including a terminal device that participates midway.

(A) First Embodiment Hereinafter, a first embodiment to which a terminal device, a central station device, a synchronization establishment system, and a synchronization establishment method of the present invention are applied will be described in detail with reference to the drawings.

  In the first embodiment, a case where the present invention is applied to an access network system that performs 1-to-N communication adopting the CDM method will be described.

(A-1) Configuration of the first embodiment (A-1-1) Configuration during downlink transmission First, the central station 2 changes to the terminal device 3 (3-1 to 3-N; N is an integer of 2 or more). The configuration of the access network system along the flow of the transmitted signal (hereinafter, this direction is assumed to be the downlink direction) will be described.

  FIG. 1 is a schematic block diagram showing a configuration along downlink transmission of the access network system of the first embodiment.

  In FIG. 1, an access network system 1 according to the first embodiment includes a central office 2, a plurality (N in FIG. 1) of terminal devices 3 (3-1 to 3-N), a distribution multiplexer 4, and a common transmission path. 6, at least a branch transmission path 7 (7-1 to 7-N).

  In the access network system 1 of FIG. 1, a distribution multiplexer 4 is provided at one end of a common transmission line 6, and the central station 2 coupled to the other end of the common transmission line 6 is branched by the distribution multiplexer 4. The first terminal device 3-1 to the N-th terminal device 3-N coupled to each of the N branch transmission lines 7 (7-1 to 7-N).

  With such a configuration, the central office 2 and the terminal device 3 (3-1 to 3-N) are connected via the common transmission path 6 and the branch transmission path 7 (7-1 to 7-N). N channel communication is possible.

  In the following description, when it is necessary to identify which channel is an apparatus related to each channel, the channel number is added after the main number. For example, in the case of indicating the transmission units of the central office corresponding to the first channel to the Nth channel, they are indicated as the first transmission unit 10-1 to the Nth transmission unit 10-N. On the other hand, when it is not necessary to identify which channel is the device, only the main number is shown. For example, the first transmission unit 10-1 to the N-th transmission unit 10-N are collectively referred to simply as the transmission unit 10.

  The central office 2 is a station side node provided on the provider side, for example, and is also called a center node, a service node, or the like. The central office 2 is configured to have at least a transmission unit 10 (10-1 to 10-N) for N channels and one addition unit 11 as a transmission configuration. In FIG. 1, only the main transmission processing configuration of the central office 2 is shown for convenience of explanation.

  The transmission unit 10 spread-modulates the data signals (first data signal to N-th data signal) of each channel (first channel to N-th channel), and codes the spread modulation signal (hereinafter also simply referred to as an extension signal). This signal is output to the adder 11 as a transmission signal. Note that each of the first transmission unit 10-1 to the Nth transmission unit 10-N has the same configuration.

  Furthermore, the transmission unit 10 is configured to include at least a synchronization signal providing unit 13 and a spread encoding unit 12.

  The synchronization signal giving unit 13 gives a synchronization signal to the data signal of each channel, and gives the data signal to which the synchronization signal is given to the spread encoding unit 12.

  When receiving the data signal to which the synchronization signal is given from the synchronization signal giving unit 13, the spread coding unit 12 performs spread coding on the data signal to which the synchronization signal is given using the spreading code, and the spread coded transmission signal (Encoded transmission signal) is given to the adder 11. Here, as a spreading code used for spreading modulation, a code having good autocorrelation characteristics and cross-correlation characteristics (for example, orthogonal gold code) can be applied.

  The adder 11 receives each encoded transmission signal (first spread signal to Nth spread signal in FIG. 1) from each transmitter 10, multiplexes each encoded transmission signal, and generates a signal ( Code division multiplexed signal) is output to the common transmission line 6.

  The common transmission line 6 is a transmission line that gives the code division multiplexed signal output from the central part 2 to the distribution multiplexer 4. As the common transmission line 6, for example, a PON system realized by an optical fiber, an electric line that transmits an electric signal, or the like can be applied. When using an optical fiber, optical signal conversion means for converting the encoded transmission signal output from the transmission unit 10 into an optical signal is provided, and the optical signals converted by the optical signal conversion means are multiplexed and transmitted in common. This can be realized by providing a configuration for outputting to the path 6.

  The distribution multiplexer 4 has a function of branching and outputting one input signal into N branches or outputting the N input signals together as one signal. In FIG. 1, the distribution multiplexer 4 N-divides the code division multiplexed signal from the central station and gives it to each terminal device 3 (3-1 to 3 -N).

  The terminal device 3 is a node provided on the subscriber side, and is called, for example, an edge node. The terminal device 3 includes at least a receiving unit that receives the code division multiplexed signal from the distribution multiplexer 4 and decodes the code division multiplexed signal.

  FIG. 2 is a block diagram illustrating an internal configuration of the receiving unit included in the terminal device 3. In FIG. 2, the receiving unit 20 of the terminal device 3 includes at least a matched filter 21, a synchronization signal detecting unit 22, a variable phase shifter 23, a clock signal reproducing unit 24, a gate unit 25, and branching units 60 and 62. Composed.

  The matched filter 21 reproduces and outputs a correlation output signal from the received code division multiplexed signal. The correlation output signal output from the matched filter 21 is branched by the branching device 60, and one is supplied to the clock signal reproducing unit 24 and the other is supplied to the gate unit 25.

  The clock signal reproduction unit 24 receives the correlation output signal branched by the branching unit 60, generates a reproduction clock signal from the correlation output signal, and supplies it to the variable phase shifter 25.

  Note that the recovered clock signal generated by the clock signal recovery unit 24 is used as a transmission signal executed by the transmission unit 30 of the terminal device 3 to be described later, in addition to being used as the latch signal described above.

  When the variable phase shifter 23 receives the reproduction clock signal from the clock signal reproduction unit 24, the variable phase shifter 23 gives the reproduction clock signal whose phase has been changed to the gate unit 25.

  The gate unit 25 receives the correlation output signal branched by the branching device 60, latches the correlation output signal with the recovered clock signal from the variable phase shifter 23, and outputs it. The output signal from the gate unit 25 is branched by the branching device 62, one of which is output as the output signal of the receiving unit 20, and the other is output to the synchronization signal detecting unit 22.

  The synchronization signal detection unit 22 receives an output signal from the gate unit 25 branched by the branching device 62, detects a synchronization signal included in the output signal, and uses the synchronization signal to be described later as a control unit of the terminal device 3 25.

(A-1-2) Configuration at Uplink Transmission Next, the flow of a transmission signal from the terminal device 3 (3-1 to 3-N) toward the central station 2 (hereinafter, this direction is referred to as the uplink direction). A configuration of the access network system 1 will be described.

  FIG. 3 is a schematic block diagram illustrating a configuration of uplink transmission of the access network system according to the first embodiment. In FIG. 3, only the transmission part 30 (30-1 to 30-N) with which the terminal device 3 is provided is shown.

  The transmission unit 30 (30-1 to 30-N) of the terminal device 3 performs transmission processing of the terminal device 3. Here, the transmission process in the terminal device 3 includes a synchronization code adding process for adding a synchronization signal to a signal transmitted from the terminal apparatus 3 toward the central station 2, an encoding process for encoding the transmission signal, and frame synchronization. This refers to frame synchronization signal generation processing for generating a frame synchronization signal to be transmitted when establishing. The synchronization code assigning process, the encoding process, and the frame synchronization signal creating process are performed using a known device such as a central processing unit (CPU). As a clock signal for driving a CPU (not shown) that controls these processes, a recovered clock signal generated by the clock signal recovery unit 24 is used.

  In FIG. 3, the transmission unit 30 (30-1 to 30-N) of the first embodiment includes a data signal encoding unit 31 (31-1 to 31-N) and a synchronization signal adding unit 32 (32-1). 32 -N), variable phase shifter 33 (33-1 to 33-N), frame synchronization signal encoding unit 34 (34-1 to 34-N), and selector 35 (35-1 to 35-35). N) at least.

  The data signal encoding unit 31 receives the data signal to which the synchronization signal is added from the synchronization signal adding unit 32, and encodes the transmission signal formed in synchronization with the reproduction clock signal with a code assigned to each channel. An encoded transmission signal is generated and given to the selector 35.

  In the first embodiment, the data signal encoding unit 31 performs spreading coding using a spreading code as a code assigned to each channel. For example, the first channel data signal encoding unit 31-1 receives the first spreading code and performs spreading coding.

  Here, the data signal refers to a signal carrying information to be transmitted, and when transmitted, it is generated and transmitted as a transmission signal with a synchronization signal described later.

  The synchronization signal applying unit 32 generates a transmission signal by applying the synchronization signal to the data signal and supplies it to the data signal encoding unit 31.

  The frame synchronization signal encoding unit 34 encodes the frame synchronization signal with a frame synchronization spreading code common to all the terminal devices 3 to generate an encoded frame synchronization signal, which is given to the selector 35.

  Here, the frame synchronization signal refers to a signal necessary for detecting the head of a frame to be described later. After the decoding by the central office 2, it is sufficient that a correlation peak is established in the frame period, and it is not necessary to put information in particular. Therefore, the frame synchronization signal may always be a signal such as logic “1”.

  The selector 35 switches an input port for inputting an input signal in accordance with a control signal from a control unit of each terminal device 3 (not shown). Thus, the output signal to be output can be changed by switching the input port. The selector 35 includes, for example, three input ports and one output port, the first input port is connected to the frame synchronization signal encoding unit 34, the second input port is opened, and the third The input port is connected to the data signal encoding unit 31 and the output port is connected to the variable phase shifter 33.

  The variable phase shifter 33 adjusts the transmission timing of the output signal from the selector 35. That is, the variable phase shifter 33 adds the delay necessary for adjusting the transmission timing to the encoded transmission signal or the encoded frame synchronization signal selected by the selector 35 and outputs the result.

  The distribution multiplexer 4 multiplexes a signal (encoded transmission signal or encoded frame synchronization signal) transmitted from each terminal device 3 and supplies the multiplexed signal as a code division multiplexed signal to the central station 2 through the common transmission path 6. .

  Next, the reception configuration of the central office 2 will be described. In FIG. 3, a reception configuration provided in the central station 2, that is, a configuration for receiving a signal from each terminal device 3 is shown.

  In FIG. 3, the central office 2 has, as a reception configuration, a distributor 49, a transmission signal reception unit 40 (first reception signal reception unit 40-1 to Nth transmission signal reception unit 40 -N), and frame synchronization signal reception unit 55. , At least.

  The distributor 49 receives the code division multiplexed signal received through the common transmission path 6 and distributes the code division multiplexed signal to each transmission signal receiving unit 40 and the frame synchronization signal receiving unit 55.

  The transmission signal reception unit 40 is a reception processing unit for each channel. When the code division multiplexed signal distributed by the distributor 49 is received, the transmission signal reception unit 40 performs reception processing on the received signal.

  The frame synchronization signal receiving unit 55 performs reception processing on the code division multiplexed signal distributed by the distributor 49.

  Here, the transmission signal receiving unit 40 and the frame synchronization signal receiving unit 55 have a transmission timing correction information notification function for notifying the variable phase shifter 33 of each terminal device 3 of the transmission timing correction information. The detailed description of the transmission timing correction information notification function will be described later.

  For example, in FIG. 3, the concept of transmission timing correction information notification is shown by taking the first channel as an example, and the first transmission signal receiving unit 40-1 or the frame synchronization signal receiving unit 55 of the central office 2 is a terminal device. A state in which transmission timing correction information is notified to the variable phase shifter 33-1 of 3-1 is indicated by a broken line.

  FIG. 4 is a block diagram showing an internal configuration of the transmission signal receiving unit 40 provided in the central office 2. In FIG. 4, the transmission signal receiving unit 40 of the central office 2 includes at least a transmission signal matched filter 41, a gate unit 45, a synchronization signal detection unit 42, and a branching unit 43.

  The transmission signal matched filter 41 decodes the received code division multiplexed signal to generate a correlation signal, and supplies the generated correlation signal to the gate unit 45.

  The gate unit 45 receives the correlation signal from the transmission signal matched filter 41, latches the correlation signal with the master clock signal from the clock signal generation unit 44, and supplies the correlation signal to the branching unit 43. An output signal from the gate unit 45 is branched by the branching unit 43, one is output as an output signal from the transmission signal receiving unit 40, and the other is given to the synchronization signal detecting unit 42.

  The synchronization signal detection unit 42 receives an output signal from the gate unit 45 via the branching unit 43 and detects a synchronization signal included in the received output signal.

  FIG. 5 is a block diagram showing an internal configuration of the frame synchronization signal receiving unit 55 of the central office 2. In FIG. 5, the frame synchronization signal receiving unit 55 of the central office 2 includes at least a frame synchronization signal matched filter 56 and a threshold value determination unit 57.

  The frame synchronization signal matched filter 56 decodes the received code division multiplexed signal to generate a correlation signal, and outputs this correlation signal.

  The threshold determination unit 57 determines whether or not the amplitude of the correlation output signal output from the frame synchronization signal matched filter 56 exceeds a set value, and outputs the result.

(A-1-3) Configuration related to establishment of uplink synchronization Next, a configuration related to establishment of uplink synchronization according to the first embodiment will be described with reference to FIG. It should be noted that the following uplink synchronization establishment processing is performed not only by the terminal device 3 participating midway but also by all the terminal devices 3.

  FIG. 6 is a schematic block configuration diagram of the access network system 1 showing a control system that plays a central role in performing uplink synchronization.

  In FIG. 6, for the sake of easy understanding, only the functional part that adjusts the reception timing necessary for establishing uplink synchronization is extracted and systematically shown. That is, only the variable phase shifter 33, the receiving unit 20, and the control unit 52 are shown for the terminal device 3, and for the central office 2, the transmitting unit 10, the transmission signal receiving unit 40, the frame synchronization signal receiving unit 55, the transmission Only the unit 10 and the correction information generation unit 51 are shown.

  In the process of establishing uplink synchronization according to the first embodiment, the central station 2 transmits a signal including frame synchronization signal permission information that permits transmission of a frame synchronization signal to each terminal device 3 (hereinafter referred to as frame synchronization signal permission). (Also called a signal).

  The variable phase shifter 33 of the terminal device 3 that has received the frame synchronization signal permission signal transmits the encoded transmission signal or the encoded frame synchronization signal to the transmission signal reception unit 40 and the frame synchronization signal reception unit 55 of the central office 2. To do.

  When the transmission signal reception unit 40 of the central office 2 receives the encoded transmission signal, the synchronization signal detection unit 42 (see FIG. 4 and not shown in FIG. 6) of the transmission signal reception unit 40 detects the synchronization signal. Generate a signal that reflects the result. Then, a signal reflecting this synchronization signal detection result is given to the correction information generation unit 51 of the central office 2.

  On the other hand, when the frame synchronization signal receiving unit 55 of the central office 2 receives the encoded frame synchronization signal, the threshold value determination unit 57 of the frame synchronization signal receiving unit 55 (see FIG. 5 and not shown in FIG. 6). .) Generates a signal reflecting the frame synchronization signal detection result. The signal reflecting the result of frame synchronization signal detection is also provided to the correction information generation unit 51 of the central office 2.

  Here, the correction information generation unit 51 of the central office 2 has a transmission timing correction information notification function for notifying the transmission timing correction information to the terminal device 3. When the correction information generation unit 51 generates transmission timing correction information for the terminal device 3, the correction information generation unit 51 transmits the transmission timing correction information to the reception unit 20 of the terminal device 3.

  When the reception unit 20 of the terminal device 3 receives the transmission timing correction information (phase shift amount information), the transmission timing correction information is given to the control unit 52, and the phase delay amount is calculated based on the transmission timing correction information. The variable phase shifter 33 is instructed to add a phase delay corresponding to the phase delay amount to the encoded transmission signal, and the reception timing is adjusted. By transmitting the encoded transmission signal whose reception timing is adjusted toward the central station 2, the feedback loop is completed.

(A-1-4) Signal Format FIG. 7 shows the format of signals transmitted and received between the central office 2 and the terminal device 3.

  FIG. 7A is a schematic configuration diagram of a signal (downlink signal) transmitted from the central office 2 to the terminal device 3. The synchronization signal and the data signal are combined to form one frame, and this signal is formed by repeating this frame. The synchronization signal is composed of a fixed signal and a control signal. The fixed signal is a bit string having a predetermined pattern and is used for bit synchronization described later on the receiving side.

  FIG. 7B is a schematic configuration diagram of a signal (uplink signal) transmitted from the terminal device 3 toward the central station 2. Similar to the downlink signal described above, the frame is configured by repeating a frame, but is different from the downlink signal in that a no-signal section is inserted in the frame of the uplink signal of the first embodiment. This no-signal section refers to a time zone in which the terminal device 3 stops transmission.

  In the first embodiment, when the terminal device 3 that participates in the middle establishes bit synchronization, the terminal device 3 that participates in the middle transmits a bit synchronization signal to the central station 2 during this non-signal period, so that synchronization is already performed. Interference with other established terminal devices 3 can be avoided.

  The no-signal section length can be determined as appropriate according to the operation, and the section length once determined may be changed as appropriate.

(A-1-5) Encoding Process (Spread Modulation Process) and Decoding Process (Despreading Process) FIG. 8 is a diagram illustrating the principles of the encoding process and the decoding process.

  FIG. 8A illustrates a part of the time waveform of the transmission signal (2 bits in FIG. 8A). FIG. 8B is a diagram showing a time waveform of cross-correlation of the correlation output signal. FIG. 8C is a diagram illustrating a time waveform of autocorrelation of the correlation output signal. FIG. 8D is a diagram illustrating a time waveform of cross-correlation of the correlation output signal. 8A to 8D, the horizontal axis indicates the time axis, and the vertical axis is omitted, but the signal intensity is shown in an arbitrary scale in the vertical axis direction.

  The encoding process and the decoding process are also called spread modulation, and indicate a process of converting each bit constituting a digital signal to be transmitted into a bit pattern having an interval narrower than the bit interval.

  A bit string constituting this bit pattern is a code, and a different code is assigned to each channel. The difference in code corresponds to the difference in bit pattern. The example shown in FIG. 8B is a 16-bit bit string given by (1, 1, 0, 1, 0, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0, 0). It is an example of the code | symbol given by.

  Encoding corresponds to generating a product signal of the signal shown in FIG. 8A and the signal shown in FIG. For example, the product signal is generated by adjusting the bias voltage of the signal shown in FIG. 8A and the signal shown in FIG. 8B to set the center of the amplitude of these signals to 0 level, The signal format formed by the binary values “0” and “1” is changed to the signal format formed by the binary values “+1” and “−1”, and the product of the two is obtained. In order to obtain this product, for example, an EXNOR (exclusive NOR) circuit, which is a gate circuit in which an inverter is connected to the output of an exclusive logical ring operation EXOR (exclusive OR) gate, is used. Of course, other existing methods may be applied to perform processing equivalent to the processing described above.

  The correlation output signals shown in FIG. 8C and FIG. 8D are obtained by obtaining a product signal of the encoded signal again with the same code as that obtained by encoding, and calculating the sum of each bit of the product signal (decoding). Generated). That is, a product signal of the code division multiplexed signal in which the encoded transmission signal is multiplexed and the code signal is obtained. The encoded transmission signal component decoded with the same code as that used for decoding is decoded as an autocorrelation signal. Also, the encoded transmission signal component decoded with a code different from the code used for decoding is generated as a cross-correlation signal.

  As shown in FIG. 8C, in the time waveform of the autocorrelation signal, a strong positive / negative peak (hereinafter referred to as an autocorrelation peak) appears at every bit interval of the transmission signal. In FIG. 8C, it is indicated by an autocorrelation peak arrow. This means that if the autocorrelation signal is subjected to threshold processing for extracting only this autocorrelation peak, the transmission signal can be extracted.

  On the other hand, the peak of the autocorrelation signal does not appear in the time waveform of the cross correlation signal as shown in FIG. In particular, when an encoded transmission signal is generated by performing spread modulation with a code of an orthogonal code sequence of the transmission signal, the cross-correlation signal is in a silent state (a signal equal to 0 level) at a position on the time axis where the autocorrelation peak appears. Strength state).

  Therefore, when spread modulation is performed using codes of orthogonal code sequences, the correlation peak in the correlation output signal obtained by decoding the code division multiplexed signal obtained by multiplexing is subject to interference from signal components of other channels. Therefore, it is easier and more reliable to restore the transmission signal by threshold processing.

(A-1-6) Frame Sync Signal FIG. 9 is a diagram for explaining a frame sync signal. FIGS. 9A and 9B show relative positions on the time axis of the encoded transmission signal and the encoded frame synchronization signal that have reached the input port of the selector 35 of the terminal device 3. The code period of the frame synchronization signal matches the period of the upstream frame, and the head of the code matches the head of the upstream frame.

  FIG. 9C shows an autocorrelation waveform subjected to correlation processing by the frame synchronization signal matched filter 56 of the central office 2. The period in which the autocorrelation peak appears coincides with the period of the frame, and the phase thereof coincides with the beginning of the frame.

  It should also be noted that the code length of the frame synchronization signal is much longer than the code length of the code used for encoding the transmission signal. In general, the height of the autocorrelation peak is proportional to the code length. Therefore, even if the transmission power of a signal encoded with a long code is kept low, a strong autocorrelation peak is obtained when correlation processing is performed on the receiving side, and threshold processing becomes easy.

(A-1-7) Frame synchronization and bit synchronization As shown in FIGS. 8A and 8B, one bit of the transmission signal is encoded by a predetermined spreading code. Then, the transmission signal encoded in each channel forms a multiplexed transmission signal.

  When multiplexing, the state in which the time phases of the transmission bits of each channel are aligned is called a bit synchronization state. In synchronous CDM communication using an orthogonal code sequence, the correlation peak is less susceptible to interference from signal components of other channels on the premise that signal transmission / reception is performed with this bit synchronization established. Benefits. Therefore, in the access network system 1, establishment of bit synchronization is essential for stable signal transmission / reception.

  On the other hand, frame synchronization refers to a state in which the heads of frames transmitted by the respective channels shown in FIG. In general, it is possible to transmit and receive data without performing frame synchronization on a code division multiple access network system.

  However, it is assumed that frame synchronization is performed in the downlink communication of the system 1 of the first embodiment.

(A-1-8) Configuration of Synchronization Signal The configuration of the synchronization signal according to the first embodiment will be described.

  In order for the fixed signal transmitted from the terminal device 3 to the central office 2 to be received, it is not sufficient that the frequency of the master clock signal matches the frequency of the clock signal extracted from the fixed signal. It is necessary to synchronize so that the phases of both coincide.

  As described with reference to FIG. 8, this is because the rising position of the master clock signal on the time axis is within the time axis of the autocorrelation peak. This corresponds to the necessity of adjusting the positional relationship at.

  FIG. 12 is a configuration diagram showing the configuration of the synchronization signal. Here, as an example of the fixed signal constituting the synchronization signal, a 5-bit signal (0, 1, 0, 1, 0) is assumed. If this 5-bit signal can be reproduced in the central office 2, a fixed signal can be received.

  On the other hand, the control signal includes transmission permission bits EN1 and EN2 for giving a transmission stop command or a transmission permission command for the transmission signal and the synchronization signal to the terminal device 3, and a phase shift amount information signal composed of 8 bits D7 to D0. And have.

  For example, as transmission permission bits, for (EN1, EN2), (0, 0) indicates all signal transmission stop, (0, 1) indicates frame synchronization signal transmission permission, and (1, 0) indicates The bit synchronization signal transmission permission is indicated, and (1, 1) is defined in advance as indicating the completion of bit synchronization.

  As the phase shift amount information signal, for example, when the phase shift amount set for the variable phase shifter 33 provided in the terminal device 3 is 0 ps (picosecond), 8 bits (D7 to D0) ( D7, D6, D5, D4, D3, D2, D1, and D0) are (0, 0, 0, 0, 0, 0, 0, 0). The amount of phase shift from 0 ps to 255 ps can be indicated using an 8-bit binary value. For example, in the case of 255 ps, (1, 1, 1, 1, 1, 1, 1, 1) is obtained.

(A-2) Operation of the First Embodiment Hereinafter, the uplink synchronization method will be described, but a normal communication operation will be described before that. In the description of the normal communication operation, it is assumed that uplink synchronization has already been completed and the reception timing is adjusted between the central office 2 and the terminal device 3.

(A-2-1) Normal Communication Operation; Downlink Transmission First, an operation of transmission (downlink transmission) from the central office 2 to the terminal device 3 will be described.

  In downlink transmission, a synchronization signal is added to a data signal to be transmitted, and then encoded with the synchronization signal and converted into an encoded transmission signal. The synchronization signal is added by the synchronization signal adding unit 13, and the encoding is performed by the spread encoding unit 12.

  The encoded transmission signals of the respective transmitters 10 are added by the adder 11 to be generated as a code division multiplexed signal, and this code division multiplexed signal is transmitted to the terminal device 3.

Note that the spreading code assigned to each channel is input to the spreading coding unit 12. For example, the first spreading code assigned to the first channel is input to the first channel spreading coding unit 12 (see FIG. 1).
The terminal device 3 receives the code division multiplexed signal and performs a decoding process by the matched filter 21 (see FIG. 2). Here, the decoding process refers to a process of performing a despreading process on a code division multiplexed signal using a code previously assigned to the own channel and generating a correlation output signal for this code.

  The correlation output signal is input to the clock signal recovery unit 24 (see FIG. 2), and a recovered clock signal is generated and output. Various methods can be applied to the generation of the reproduction clock signal. For example, an existing method using a PLL (Phase Locked Loop) circuit can be applied. In addition, the correlation output signal is generated and determined as reception data by latching with the above-described reproduction clock signal.

(A-2-2) Normal Communication Operation; Uplink Transmission Next, a transmission (uplink transmission) operation from the terminal device 3 to the central station 2 will be described.

  In uplink transmission, the code division multiplexed signal from the terminal device 3 is N-branched by the distributor 49 of the central office 2 and provided to the transmission signal receiving unit 40 for each channel.

  In the transmission signal receiving unit 40, despreading processing is performed on the uplink signal (code division multiplexed signal) using a code assigned to the own channel, and a correlation output signal for the own channel is generated. That is, the transmission signal receiving unit 40 performs a decoding process on the uplink signal. This correlation output signal is latched by the master clock signal, generated as reception data, and determined.

(A-2-3) System Flow The access network system 1 according to the first embodiment is activated when the central office 2 is turned on.

  Prior to starting transmission / reception of data signals, first, an operation of establishing frame synchronization and bit synchronization is performed between the central office 2 and the terminal device 3 that is powered on at this time. This is called initial adjustment. Various known methods can be applied as the initial adjustment method. For example, the method described in Patent Document 1 can be used.

  After the initial adjustment is completed, data signal transmission / reception is started between the central office 2 and the terminal device 3. Since the transmission / reception of the data signal has been described in the section of the normal communication operation of (A-2-1) and (A-2-2), detailed description thereof is omitted here.

  While a normal communication operation is being performed, a situation occurs in which a certain terminal device 3 participates midway. At this time, a process for realizing midway participation without affecting the communication operation between the terminal apparatus 3 and the central office 2 that have already established synchronization will be described below.

(A-2-4) Synchronization establishment process for realizing midway participation FIG. 10 is a flowchart for explaining the operation of the synchronization establishment process for realizing midway participation.

  As described above, when the central station 2 and at least one terminal device 3 are performing normal communication operations, when the other terminal devices 3 connected to the central station 2 are powered on, the central station 2 Detects this and performs synchronization establishment processing described below.

  Note that the flowchart shown in FIG. 10 has no end condition and is an infinite loop. This is because the terminal device 3 that always participates on the way is always monitored while the system performs a normal communication operation.

  First, the central station 2 initializes n (n = 1) in order to confirm the power state of the terminal device 3-n (n is an integer of 1 to N), and a terminal management table (not shown) in its own station ), The power state of the terminal device 3-n (here, n = 1) is confirmed (step S10).

  Here, the terminal management table is a table for managing the power state of each terminal device 3 confirmed by at least the central office 2, and the central office 2 is in a state where the power of the terminal device 3 is turned on (power ON state). If it is confirmed that the power is turned off or the power is turned off (power is turned off), the result is recorded.

  In step S10, when the terminal device 3-n is powered off, the process proceeds to step S20, where the current power status of the terminal device 3-n is checked, and when the terminal device 3-n is powered on, The process proceeds to step S110.

  In step S110, the central office 2 increments the value of the argument n by one in order to confirm the power state of the next terminal device 3 in the terminal management table. Therefore, it indicates that nothing is performed with respect to the terminal device 3 whose power is turned on. In step 120, the central office 2 checks the value of the argument n, and if n = N, sets n = 1, otherwise moves directly to step S10.

  On the other hand, in step S10, when it is confirmed in the terminal management table that the terminal device 3-n is in the power-off state, the central office 2 confirms whether the terminal device 3-n is still in the power-off state. A frame synchronization signal transmission permission signal is transmitted to the n-th terminal device 3-n (step S20). A specific example of the frame synchronization signal transmission permission signal will be described in detail in the column of the synchronization signal configuration described later.

  When the frame synchronization signal transmission permission signal from the central office 2 is given to the nth terminal device 3-n, when the nth terminal device 3-n is in the power ON state, the nth frame synchronization signal permission signal is The n-th terminal device 3-n receives the n-th frame synchronization signal from the n-th terminal device 3-n to the central station 2 (step S30).

  Here, the amount of phase shift of the variable phase shifter 33 in the n-th terminal device 3-n is arbitrary. At this time, the n-th terminal apparatus 3-n is in a state of waiting for an instruction from the central office 2 in order to perform uplink synchronization.

  Note that the operation of step S30 can be performed only when the power of the n-th terminal device 3-n is on, but when the power is off, the n-th frame synchronization signal transmission permission signal is received. Neither can the n-th frame synchronization signal be transmitted.

  When the n-th frame synchronization signal from the n-th terminal apparatus 3-n is given to the central station 2 and the central station 2 has successfully received the n-th frame synchronization signal, the process proceeds to step S50, and the n-th frame If reception of the synchronization signal has failed, the process proceeds to step S110, and a confirmation process is performed for the next terminal device 3 (step S40).

  Since the operations in steps S110 and S120 are as described above, they are omitted. Transition to step S110 means that if the power supply state is confirmed again with respect to the terminal device 3 that has been confirmed that the power supply has not been turned on at the previous confirmation, the power supply is still turned off. Accordingly, the central office 2 increments the argument n by one and performs a confirmation process for the next terminal device 3.

  When the central station 2 successfully receives the n-th frame synchronization signal in step S40, the central station 2 compares the autocorrelation peak position of the received encoded frame synchronization signal with the reception timing of the frame in the local station, and compares these positions. Detect phase difference. Then, the n-th phase shift amount in the variable phase shifter 33 of the n-th terminal apparatus 3-n is calculated so that this phase difference becomes zero. Then, the central office 2 transmits the n-th phase shift amount together with the n-th frame synchronization completion notification to the n-th terminal device 3-n (step S50). Thereby, the frame synchronization of the terminal device 3-n is completed. Note that the configuration of the synchronization signal shown in FIG. 12 can be applied to a specific example of the n-th frame synchronization completion notification.

  Next, the central office 2 transmits an nth bit synchronization signal transmission permission signal to the nth terminal apparatus 3-n (step S60).

  The nth bit synchronization signal transmission permission signal is composed of one or more synchronization signals. In the control signal included in the synchronization signal, phase shift amount information for setting and instructing the phase shift amount to be set in the nth variable phase shifter 33 is placed.

  When the nth bit synchronization transmission permission signal from the central office 2 is given to the nth terminal device 3-n, the nth control included in the nth bit synchronization signal transmission permission signal in the nth terminal device 3-n. The n-th phase shift amount information given by the signal is read, and the n-th phase shift amount according to the n-th phase shift amount information is set in the n-th variable phase shifter 33 of the n-th terminal device 3-n. Then, the n-th terminal device 3-n transmits the n-th bit synchronization signal to the central station 2 (step S70). The nth bit synchronization signal is composed of one or more fixed signals.

  Here, the transmission timing of the n-th bit synchronization signal in the terminal device 3 will be described with reference to FIG. FIG. 11 is a diagram illustrating the arrival timing of the signal transmitted by each terminal device 3 in the central office 2. The horizontal axis indicates time.

  In FIG. 11, terminal devices 3-a to 3-i (FIGS. 11A to 11C) are terminal devices that have already established synchronization with the central office 2, and perform normal operations. ing. The terminal device 3-n (FIG. 11D) is a terminal device that participates during the process of step S70.

  In this case, it is assumed that the terminal apparatus 3-n transmits the n-th bit synchronization signal composed of a fixed signal within a no-signal section provided in the uplink frame. As a result, the n-th bit synchronization signal can be transmitted at a time that does not overlap in time with a signal (for example, a synchronization signal or a data signal) transmitted by another terminal device 3 that is already synchronized. Can be avoided.

  Here, the terminal device 3-n has established frame synchronization with the central office 2 through the processing of steps S20 to S50. Therefore, since the terminal device 3-n can know the no-signal section of the uplink frame, it can transmit the nth bit synchronization signal in this radio signal section.

  When the n-th bit synchronization signal from the n-th terminal apparatus 3-n is given to the central station 2 and the n-th transmission signal reception unit 40-n of the central station 2 has successfully received the n-th bit synchronization signal, the step is performed. The process proceeds to S95, and if the reception of the nth bit synchronization signal has failed, the process proceeds to Step S90 (Step S80). At this time, the n-th fixed signal determination process is performed by the n-th transmission signal receiver 40-n.

  In step S80, when the reception of the n-th bit synchronization signal by the n-th transmission signal receiving unit 40-n fails, the transmission timing of the n-th terminal device 3-n is corrected in the central station 2, and the transmission timing correction information is stored. The loaded nth bit synchronization signal transmission permission signal is transmitted to the nth terminal apparatus 3-n (step S90).

  That is, in step S90, the central office 2 changes the n-th phase shift amount, generates a phase shift amount different from the phase shift amount previously given to the n-th terminal device 3-n as the correction information, and this correction information. The n-th bit synchronization signal transmission permission signal carrying the (n-th phase shift amount) is transmitted to the terminal device 3-n (step S90).

  On the other hand, when the reception of the n-th bit synchronization signal by the n-th transmission signal receiver 40-n is successful in step S80, the central office 2 gives an n-th bit synchronization completion notification to the n-th terminal device 3-n. The n-th phase shift amount is determined and fixed as the n-th phase shift amount of the variable phase shifter 33 of the n-th terminal device 3-n (step S95).

  Then, the central station 2 updates the power state of the terminal device 3-n to ON in the terminal management table provided in the local station (step S100). Thereafter, the process returns to step S10 via steps S110 and S120, and the same processing is performed for the next terminal device 3.

  Here, the determination process of the n-th fixed signal by the n-th transmission signal receiving unit 40-n in step S80 will be described.

  The first to n-th fixed signals used for the synchronization determination may all be the same as the signals assigned to the first terminal device 3-1 to the n-th terminal device 3-n, or may be different signals. good.

  Various methods can be applied as a method for determining the fixed signal. For example, the fixed signal is stored in advance in storage devices (not shown) of the central office 2 and the terminal device 3 and reproduced. And the fixed signal of the storage device are subjected to pattern matching. If they match, it is assumed that the fixed signal has been successfully received, and if they do not match, the fixed signal has failed to be received. Various existing techniques can be applied to the fixed signal pattern matching method.

  As another fixed signal determination method, for example, when the central office 2 transmits a transmission permission signal (the nth frame synchronization signal transmission permission signal and / or the nth bit synchronization signal transmission permission signal) to the terminal device 3, The instruction information of the fixed signal to be returned in advance is transmitted on the transmission permission signal. Then, the central office 2 performs pattern matching between the reproduced fixed signal and the fixed signal instructed to be returned. If they match, the fixed signal is successfully received. If they do not match, the fixed signal fails to be received. You can apply the method that you did. Various existing techniques can also be applied to the pattern matching method of the fixed signal in this case.

  FIG. 13 is a configuration diagram showing an example of a transmission permission signal (synchronization signal) that instructs a fixed signal to be sent back from the terminal device 3 toward the central office.

  The control signal of the transmission permission signal shown in FIG. 13 is a signal of 5 bits (F4, F3, F2, F1, F0) of F4 to F0 in addition to the transmission permission bit and the phase shift amount information signal described in FIG. Consists of.

(A-2-5) Detailed Explanation of Signal Processing in Terminal Device 3 Referring to FIG. 14, after receiving various transmission permission signals from central station 2 in terminal device 3, a response signal is transmitted to central station 2. The steps up to are explained.

  FIG. 14 is a block diagram showing only a part necessary for explanation of a signal processing step of transmitting a response signal after receiving a transmission permission signal in the terminal device 3.

  The fixed signal transmitted from the central office 2 is controlled and output as a correlation output signal by the matched filter 21, and the correlation output signal is touch-processed by the master clock signal and output by the gate unit 25. This output signal is branched by the branching device 62 and input to the synchronization signal detection unit 22 to detect the synchronization signal.

  As shown in FIG. 12, the control signal included in the detected synchronization signal is a signal in which information on stoppage of transmission or transmission permission and the amount of phase shift are expressed in the form of digital data. The control signal is input to the control unit 52 as shown in FIG.

  Here, the control signal indicates transmission timing correction information extracted in the receiving unit 20 included in the terminal device 3.

  An example of calculating the phase delay amount notified by the transmission timing correction information and instructing the variable phase shifter 33 to add a phase delay corresponding to the phase delay amount to the encoded transmission signal is a specific example. The following are the contents.

  As the variable phase shifter 33, for example, DS1023 manufactured by Maxim can be appropriately used. The variable phase shifter 33 has a function of adding an arbitrary delay amount to a signal input from an input terminal (indicated in FIG. 14) and outputting the signal from an output terminal (indicated as OUT in FIG. 14). ing. The delay amount is controlled by a binary voltage signal output from output terminals (P0,..., P7) provided in the control unit 52.

  As the selector 35, for example, an AD8174 manufactured by Analog Devices, Inc. can be used as appropriate. The selector 35 has a function of selecting and outputting one of signals input from a plurality of input ports. Selection of the input port is controlled by a voltage signal output from a SEL terminal included in the control unit 52.

  If the (EN1, EN2) bits of the control signal are (0, 0), that is, if all signal transmission is stopped, transmission can be stopped by connecting the second input port (open) to the output port.

  If the (EN1, EN2) bits are (0, 1), that is, if the frame synchronization signal transmission is permitted, the first input port (connected to the frame synchronization signal encoding unit 34) is connected to the output port. A frame synchronization signal can be output.

  If the (EN1, EN2) bit is (1, 0), that is, if bit synchronization signal transmission is permitted, bit synchronization is achieved by connecting the third input port (connected to the transmission signal encoding unit 31) to the output port. A signal can be output.

  If the (EN1, EN2) bit is (1, 1), that is, if frame synchronization is completed, the transmission signal can be output by connecting the third input port to the output port.

(A-3) Effect of First Embodiment As described above, according to the first embodiment, after frame synchronization is completed, a terminal device that has joined midway transmits a bit synchronization signal to a no-signal section of an uplink frame. By transmitting, it is possible to avoid interference with a signal from a terminal device with which synchronization is established in the central office, so that synchronization of the terminal device with midway participation is established without stopping communication of the terminal device with which synchronization is established Can do.

(B) Other embodiments In the first embodiment, the application of the 1-to-N communication system is not limited. That is, the transmission path is not limited to PON, and the transmission path may be an electrical transmission path.

  In the first embodiment, the variable phase shifters 23 and 33 in the receiving configuration are provided in the sampling clock path. However, if the predetermined phase relationship can be achieved, the variable phase shifters 23 and 33 are provided in the data signal path. Alternatively, both the sampling clock path and the data signal path may be provided.

  In the first embodiment, the configuration for obtaining the correlation output for the spread demodulation has been shown for the matched filter, but other correlation calculation configurations such as a sliding correlator may be applied.

  In the first embodiment, when confirming the power state of the terminal device based on the terminal management table, the terminal device 3-1 is sequentially confirmed as n = 1, but the terminal device to be confirmed is randomly selected. It may be determined.

  In the first embodiment, the phase indication from the central office to each terminal device is included in the synchronization signal. However, if the phase indication can be given to each terminal device, other signals may be notified.

It is a block diagram which shows the whole structure of the access network system of 1st Embodiment, and shows the transmission structure of a central office (up direction). It is a block diagram which shows the reception structure of the terminal device of 1st Embodiment. It is a block diagram which shows the whole structure of the access network system of 1st Embodiment, and shows the receiving structure of a terminal device. It is a block diagram which shows the internal structure of the transmission signal receiving part of the central office of 1st Embodiment. It is a block diagram which shows the internal structure of the frame-synchronization signal receiving part of the central office of 1st Embodiment. It is a block diagram which shows the structure which concerns on the uplink synchronization establishment of 1st Embodiment. It is explanatory drawing explaining the signal format of 1st Embodiment. It is explanatory drawing which shows the principle of the spreading | diffusion modulation process and de-spreading process of 1st Embodiment. It is explanatory drawing explaining the frame synchronizing signal of 1st Embodiment. It is a flowchart which shows the uplink synchronization establishment process of 1st Embodiment. It is explanatory drawing explaining the timing of the bit synchronizing signal of 1st Embodiment. It is explanatory drawing explaining the structure of the synchronizing signal of 1st Embodiment. It is explanatory drawing explaining another structure of the synchronizing signal of 1st Embodiment. It is explanatory drawing explaining the signal processing in the terminal device of 1st Embodiment.

Explanation of symbols

1 ... Access network system,
2 ... central office, 10 (10-1 to 10-N) ... transmission unit, 11 ... addition unit, 12 (12-1 to 12-N) ... spread coding unit, 13 (13-1 to 13-N) ... synchronization signal giving unit, 40 ... transmission signal reception unit, 55 ... frame synchronization signal reception unit, 51 correction information generation unit,
DESCRIPTION OF SYMBOLS 3 ... Terminal device, 20 ... Reception part, 21 ... Matched filter, 22 ... Synchronization signal detection part, 23 ... Variable phase shift part, 24 ... Clock signal reproduction | regeneration part, 25 ... Gate part, 30 ... Transmission part, 31 (31- 1-31-N) ... data signal encoding unit, 32 (32-1 to 32-N) ... synchronization signal applying unit, 33 (33-1 to 33-N) ... variable phase shifter, 34 (34-1) 34-N) ... frame synchronization signal encoding unit, 35 (35-1 to 35-N) ... selector, 52 ... control unit.

Claims (4)

In a terminal device that establishes synchronization with the central station device and participates in a 1-to-N communication system that communicates between the central station device and a plurality of terminal devices via a distribution multiplexer according to the code division multiplexing system ,
In cooperation with the synchronization establishment main control means of the central station device, the synchronization establishment slave control means for controlling synchronization establishment with the central station device,
The synchronization establishment subordinate control means is
When the frame synchronization signal transmission permission signal is received from the synchronization establishment main control means of the central station device, the code length is longer than the code used for encoding the transmission signal, and has a period that matches the upstream frame. A frame synchronization signal transmitter that transmits a frame synchronization signal, the head of which coincides with the head of the upstream frame and has a fixed signal;
When receiving a bit synchronization signal transmission permission signal from the synchronization establishment main control means of the central station apparatus, a bit synchronization signal transmission unit that transmits a bit synchronization signal including a fixed signal during a no-signal period constituting the frame;
When receiving the phase shift amount information of the transmission phase related to frame synchronization from the synchronization establishment main control means of the central station apparatus, or when receiving the optimum transmission phase, the transmission phase related to the frame synchronization And a transmission phase control unit that adjusts the transmission phase according to the phase shift amount information or the optimal transmission phase. In the central station apparatus that is a component of a one-to-N communication system that performs communication according to a code division multiplexing method between a central station apparatus and a plurality of terminal apparatuses via a distribution multiplexer,
In cooperation with the synchronization establishment subordinate control means possessed by each of the terminal devices, a synchronization establishment main control means for controlling synchronization establishment with each of the terminal devices is provided,
The synchronization establishment main control means is
A frame synchronization signal transmission permission signal transmission unit that transmits a frame synchronization signal transmission permission signal to the terminal devices participating in the middle,
Receives a frame synchronization signal from the terminal device participating midway, and based on the spread demodulation output of the fixed signal period in the received frame synchronization signal, information on the amount of phase shift of the transmission phase related to the frame synchronization of the terminal device A frame synchronization execution unit that transmits the phase shift amount information of the transmission phase related to the frame synchronization to the terminal device that participates halfway;
A bit synchronization signal transmission permission signal transmission unit that transmits a bit synchronization signal transmission permission signal including phase shift amount information related to bit synchronization to the terminal devices participating in the middle,
Based on the spread demodulation output of the fixed signal period in the bit synchronization signal received from the terminal device joined in the middle, when it is determined that the signal of the transmission phase has been received effectively, the optimum transmission phase is determined, A central station apparatus comprising: a bit synchronization execution unit configured to transmit to the participating terminal apparatus and set the phase as a synchronization phase. Synchronization establishment for establishing synchronization between a participating terminal apparatus and a central station apparatus in a one-to-N communication system that communicates between a central station apparatus and a plurality of terminal apparatuses via a distribution multiplexer according to a code division multiplexing system In the system,
The central station device has synchronization establishment main control means for controlling synchronization establishment of each terminal device, and each terminal device cooperates with the synchronization establishment main control means to control synchronization establishment. Having control means,
The synchronization establishment main control means is
A frame synchronization signal transmission permission signal transmission unit that transmits a frame synchronization signal transmission permission signal to the terminal devices participating in the middle,
Receives a frame synchronization signal from the terminal device participating midway, and based on the spread demodulation output of the fixed signal period in the received frame synchronization signal, information on the amount of phase shift of the transmission phase related to the frame synchronization of the terminal device A frame synchronization execution unit that transmits the phase shift amount information of the transmission phase related to the frame synchronization to the terminal device that participates halfway;
A bit synchronization signal transmission permission signal transmission unit that transmits a bit synchronization signal transmission permission signal including phase shift amount information related to bit synchronization to the terminal devices participating in the middle,
Based on the spread demodulation output of the fixed signal period in the bit synchronization signal received from the terminal device joined in the middle, when it is determined that the signal of the transmission phase has been received effectively, the optimum transmission phase is determined, A bit synchronization execution unit that transmits to the participating terminal device and sets it as a synchronization phase;
The synchronization establishment subordinate control means is
When the frame synchronization signal transmission permission signal is received, the code length is longer than the code used for encoding the transmission signal, has a period that matches the upstream frame, the head of the code matches the head of the upstream frame, And a frame synchronization signal transmission unit that transmits a frame synchronization signal having a fixed signal;
A bit synchronization signal transmission unit that transmits a bit synchronization signal including a fixed signal in a non-signal period constituting the frame when the bit synchronization signal transmission permission signal is received;
A synchronization establishment system, comprising: a transmission phase control unit that adjusts a transmission phase when the phase shift amount information of a transmission phase related to frame synchronization is received or when the optimum phase is received. Synchronization establishment for establishing synchronization between a participating terminal apparatus and a central station apparatus in a one-to-N communication system that communicates between a central station apparatus and a plurality of terminal apparatuses via a distribution multiplexer according to a code division multiplexing system In the method
The central station device has synchronization establishment main control means for controlling synchronization establishment of each terminal device, and each terminal device cooperates with the synchronization establishment main control means to control synchronization establishment. Having control means,
The synchronization establishment main control means is
A frame synchronization signal transmission permission signal transmission step of transmitting a frame synchronization signal transmission permission signal to the terminal device participating midway;
Receives a frame synchronization signal from the terminal device participating midway, and based on the spread demodulation output of the fixed signal period in the received frame synchronization signal, information on the amount of phase shift of the transmission phase related to the frame synchronization of the terminal device Frame synchronization execution step of transmitting the phase shift amount information of the transmission phase related to the frame synchronization to the terminal device participating in the middle,
A bit synchronization signal transmission permission signal transmission step for transmitting a bit synchronization signal transmission permission signal including phase shift amount information related to bit synchronization to the terminal device participating midway,
Based on the spread demodulation output of the fixed signal period in the bit synchronization signal received from the terminal device joined in the middle, when it is determined that the signal of the transmission phase has been received effectively, the optimum transmission phase is determined, A bit synchronization execution step that is transmitted to the participating terminal devices and set as a synchronization phase;
The synchronization establishment subordinate control means is
When the frame synchronization signal transmission permission signal is received, the code length is longer than the code used for encoding the transmission signal, has a period that matches the upstream frame, the head of the code matches the head of the upstream frame, And a frame synchronization signal transmission step of transmitting a frame synchronization signal having a fixed signal,
A bit synchronization signal transmitting step of transmitting a bit synchronization signal including a fixed signal during a no-signal period constituting the frame when the bit synchronization signal transmission permission signal is received;
A synchronization establishment method comprising: a transmission phase control step of adjusting a transmission phase when the phase shift amount information of the transmission phase related to frame synchronization is received or when the optimum phase is received.

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