Propagation delay time adjustment method, propagation delay time adjustment system, propagation delay time adjustment device, propagation delay time adjustment program, and node device

The present invention relates to a propagation delay time adjustment method, a propagation delay time adjustment system, a propagation delay time adjustment device, a propagation delay time adjustment program, and a node device, for example, using a synchronous code division multiplexing (CDM) method. It can be applied to a method of adjusting the time in the receiving circuit in the one-side communication device in the access network.

An access network system using the code division multiplexing (CDM) method can multiplex multiple transmission signals at the same time, and can perform large-capacity data communication while saving communication resources such as frequency or time slot. It has the feature that it can be performed.

In particular, in the CDM method called synchronous type, the phases of coded signals encoded by different codes must be matched. This is called code synchronization.

In the access network system, one station-side device and N subscriber-side devices communicate. The transmission line lengths of the station-side device and each subscriber-side device are usually different from each other. Therefore, in order to perform code synchronization (this is called uplink synchronization) in uplink communication (communication from the subscriber side to the station side), work (ranging) to correct the phase shift caused by this difference in transmission line length. , I will call it).

Patent Document 1 discloses this method of ranging. The ranging method described in Patent Document 1 is the following technique.

In the 1-to-N communication system, the center node device (station side device) fixes the reception phase during the range processing. Then, the transmission permission signal instructing the transmission phase is repeatedly transmitted to the edge node device (subscriber side device) for which synchronization is to be established, and the transmission phase in the transmission permission signal at each repetition is converted. When the edge node device receives the transmission permission signal, it transmits the transmission signal for the synchronization establishment operation including the fixed signal in the transmission phase included in the received transmission permission signal.

Then, based on the diffused demodulation output signal for the fixed signal period in the received signal from the edge node device, the center node device determines whether or not the signal of the transmission phase can be effectively received, and swings the transmission phase. The optimum transmission phase that can be effectively received within the range is determined, and the edge node device is notified. As a result, the edge node device is a technique of setting the transmission phase to the optimum transmission phase when the optimum transmission phase is received.

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2007-158585</text></patcit>

<p> As described above, since the transmission path distances between the station-side device and each subscriber-side device are different, there is a difference in the transmission time of the transmission signal. Therefore, it is necessary to correct the difference in the transmission time of the transmission signal by the above-mentioned range processing.</p><p> However, in order to realize a state in which all the phases of the transmission signals of each channel are aligned (code synchronization) by performing the above-mentioned range processing, it is a prerequisite that the following two conditions are satisfied.</p><p>(Condition 1) The difference in transmission time (referred to as reception skew) from the distributor 49 in the station side device 2 to the gate 45-n in each receiver 40-n is zero (Patent Document 1). See Figures 3 and 4).</p><p>(Condition 2) The difference in transmission time (main clock skew) from the clock reproduction 44 to the gate 45-n in each receiver 40-n is zero (see FIG. 4 of Patent Document 1).</p><p> This reception skew and the main clock skew are collectively called a skew. This skew is unique to the reception configuration of the station side device 2.</p><p> Therefore, in order to make this skew zero, for example, a skew adjustment signal generator that generates a skew adjustment signal is arranged in the station side device 2, the skew adjustment signal is input to the distributor 49, and each channel. It is also conceivable to adopt a configuration in which the transmission time difference of the above is calculated and the skew is adjusted. By doing so, the skew can be adjusted by the station side device 2 alone.</p><p> However, since it is necessary to adjust the skew of each receiver 40-n, it is necessary to provide a large number of very complicated components, and it is very difficult to manufacture such a station-side device 2. Is.</p><p> Therefore, a propagation delay time adjustment method, a propagation delay time adjustment system, a propagation delay time adjustment device, and a propagation delay time adjustment program that can adjust skew and establish reliable code synchronization using a conventional device configuration or network configuration. And node devices are required.</p>

<p> In order to solve such a problem, the first propagation delay time adjusting method of the present invention follows a synchronous code division multiplexing method between a center node device and N (N is an integer of 2 or more) edge node devices. In the propagation delay time adjustment method for adjusting the propagation delay time generated inside the receiving circuit for each channel of the center node device constituting the 1-to-N communication system for communication, the center node device is (1) inside the receiving circuit for each channel. Each edge node device is provided with (2) a subordinate control means for controlling the propagation delay time in cooperation with the main control means, and the main control means is provided with a main control means for sequentially adjusting the propagation delay time generated in the above. (1-1) It has a transmission permission signal transmission step of transmitting a transmission permission signal with a specified diffusion code to the edge node device, and when the slave control means receives (2-1) the transmission permission signal. , A reception phase control step of having a transmission control step of repeatedly transmitting a synchronization signal encoded using a diffusion code, and (1-2) a reception phase control step of changing the reception phase of the reception circuit corresponding to the edge node device by the main control means. And (1-3) the reception availability determination step of determining whether or not the signal can be effectively received based on the diffusion demodulation output signal from the reception circuit for the fixed signal period in the reception signal from the edge node device, and ( 1-4) range was shake the received phase and optimum reception phase determination step of determining the effective optimal reception phase that can be received among circumference, (1-5) optimal reception phase the reception phase of the reception circuit It is characterized by having a reception phase setting step of setting as.</p><p> The second propagation delay time adjustment system of the present invention is a one-to-N communication system in which communication is performed between a center node device and N (N is an integer of 2 or more) edge node devices according to a synchronous code division multiplexing method. In the propagation delay time adjustment system that adjusts the propagation delay time that occurs inside the receiving circuit for each channel of the center node device that composes, the center node device sequentially (1) sequentially adjusts the propagation delay time that occurs inside the receiving circuit for each channel. Each edge node device is provided with a main control means to be adjusted, and each edge node device is provided with a subordinate control means for controlling the propagation delay time in cooperation with the main control means, and the main control means is (1-1) an edge node device. On the other hand, it has a transmission permission signal transmission unit that transmits a transmission permission signal for which a spread code is specified, and when the slave control means receives (2-1) the transmission permission signal, it is encoded by using the spread code. It has a transmission control unit that repeatedly transmits the synchronized signal, and the main control means is (1-2) a reception phase control unit that changes the reception phase of the reception circuit corresponding to the edge node device, and (1-3) edge. Based on the spread demodulation output signal from the reception circuit for the fixed signal period in the reception signal from the node device, the reception availability judgment unit that determines whether or not the signal can be effectively received, and (1-4) the reception phase are shaken. It has an optimum reception phase determination unit that determines the optimum reception phase that can be effectively received within the set range, and (1-5) a reception phase setting unit that sets the optimum reception phase as the reception phase of the reception circuit. It is characterized by that.</p><p> The third propagation delay time adjusting device of the present invention is a one-to-N communication system that communicates between a center node device and N (N is an integer of 2 or more) edge node devices according to a synchronous code division multiplexing method. In the propagation delay time adjusting device that adjusts the propagation delay time that occurs inside the receiving circuit for each channel of the center node device that constitutes, the center node device (1) determines the propagation delay time that occurs inside the receiving circuit for each channel. A transmission permission signal transmitter that is provided with a main control means that sequentially adjusts, and the main control means transmits a transmission permission signal with a spread code specified to the (1-1) edge node device, and (1-2) edge A signal is generated based on the reception phase control unit that changes the reception phase of the reception circuit corresponding to the node device, and (1-3) the spread demodulation output signal from the reception circuit for a fixed signal period in the reception signal from the edge node device. A reception availability determination unit that determines whether or not the signal was effectively received, and (1-4) an optimum reception phase determination unit that determines the optimum reception phase that was effectively received within the range in which the reception phase was changed. (1-5) It is characterized by having a reception phase setting unit that sets the optimum reception phase as the reception phase of the reception circuit.</p><p> The fourth propagation delay time adjustment program of the present invention is a one-to-N communication system that communicates between a center node device and N (N is an integer of 2 or more) edge node devices according to a synchronous code division multiplexing method. In the propagation delay time adjustment program that adjusts the propagation delay time that occurs inside the receiving circuit for each channel of the center node device that composes, the center node device sequentially adjusts the propagation delay time that occurs inside the receiving circuit for each channel. The main control means is provided with control means, and the main control means is (1) a transmission permission signal transmitter that transmits a transmission permission signal with a spread code specified to the edge node device whose propagation delay time is adjusted, and (2) an edge node device. The reception phase control unit that changes the reception phase of the reception circuit corresponding to (3) Was the signal effectively received based on the spread demodulation output signal from the reception circuit for the fixed signal period in the reception signal from the edge node device? Reception availability judgment unit that determines whether or not to receive, (4) Optimal reception phase determination unit that determines the optimum reception phase that can be effectively received within the range in which the reception phase is shaken, (5) Receives the optimum reception phase. It is characterized in that it functions as a reception phase setting unit that is set as the reception phase of the circuit.</p><p> The fifth node device of the present invention is a center node of a one-to-N communication system that communicates between a center node device and N (N is an integer of 2 or more) edge node devices according to a synchronous code division multiplexing method. A node device that functions as a device is characterized by including a third propagation delay time adjusting device of the present invention.</p>

<p> According to the present invention, the propagation delay time (skew) in the receiving circuit of the center node device can be adjusted by a simple configuration using the existing range processing. Further, if the range processing of the conventional example is performed after executing the skew adjustment procedure, reliable code synchronization can be established.</p>

(A) First Embodiment Hereinafter, the first embodiment of the propagation delay time adjusting method, the propagation delay time adjusting system, the propagation delay time adjusting device, the propagation delay time adjusting program, and the node device of the present invention will be described with reference to the drawings.

(A-1) Configuration of First Embodiment FIG. 1 is a block diagram showing an overall configuration of the communication system of the first embodiment and a transmission configuration in a station-side device (center node device).

In the following description, only the configuration related to synchronization establishment is described, and the configuration related to transmission / reception of user data is omitted.

In FIG. 1, the one-to-N communication system (hereinafter, simply referred to as a communication system) 1 of the first embodiment adopts a synchronous CDM method, and has two station-side devices and a plurality (N). ) Subscriber device (edge node device) 3-1 to 3-N, and distribution multiplier 4. The station side device 2 and the distribution multiplier 4 are connected via a common transmission line 5, and each subscriber device 3-n (n is 1 to N, the same applies hereinafter) and the distribution multiplier 4 are individual transmission lines 6-n. It is connected via. That is, the communication system 1 is configured by connecting the station side device 2 and the subscriber devices 3-1 to 3-N for N channels via the distribution multiplier 4.

In FIG. 1, the station-side device 2 has one main clock generator 14, transmission units 10-1 to 10-N for N channels, and one addition unit 11 as a transmission configuration.

The main clock generated by the main clock generator 14 determines the repetition period of the digital signals transmitted and received by the system. That is, the entire system is synchronized with this main clock.

Each transmission unit 10-n has a synchronization signal generation unit 13-n that generates a synchronization signal and a diffusion unit 12-n that spread-modulates with different diffusion codes. Here, as the diffusion code used for the diffusion modulation, for example, a code such as an orthogonal gold code having good autocorrelation characteristics and cross-correlation characteristics is used. The diffusion modulation signal (hereinafter referred to as a diffusion signal) from each transmission unit 10-n is multiplexed by the addition unit 11 and output to the common transmission line 5.

The communication system 1 is mainly intended to be applied to an optical access system, but since it has a feature in a synchronization method, the optical / electrical conversion configuration and the optical / electrical conversion configuration are shown in FIG. 1 and the drawings described later. Illustrations such as electrical / optical conversion configurations are omitted.

In FIG. 1, the multiplex signal (downlink signal) from the station side device 2 is branched into N signals by the distribution multiplexing device 4 and transmitted to each subscriber device 3-n via the individual transmission lines 6-n. To.

FIG. 2 is a block diagram showing a detailed configuration of a receiving unit in each subscriber device 3-n to which a multiplex signal branched from an individual transmission line 6-n is given.

In FIG. 2, the receiving unit 20-n of the subscriber device 3-n performs a correlation calculation (reverse spreading processing) between the received signal (multiple signal) and the spreading code, and generates a correlated output signal for the own channel (matched filter). MF) 21-n, clock reproduction section 24-n that reproduces the main clock from the output of the matched filter 21-n, variable phase shifter 23-n that changes the phase of the main clock, and variable output of the matched filter. It has a gate unit 25-n that latches with the main clock that has passed through the phase shifter 23-n, and a synchronization signal detection unit 22-n that detects a synchronization signal from the output of the gate unit 25-n.

A spreading code (diffusion code for each subscriber) corresponding to the transmitting unit 10-n of the corresponding station-side device 2 is assigned to the receiving unit 20-n of the subscriber device 3-n, and the matched filter 21- n uses the spreading code to demodulate the received signal.

FIG. 3 shows the detailed configuration of the transmission unit of each subscriber device 3-n and the overall configuration of the communication system along the flow of the transmission signal from the transmission unit to the station side device 2.

Each subscriber device 3-n includes a transmitter 30-n. The main clock (without phase shift processing) obtained by the clock reproduction unit 24-n of the reception unit 20-n described above is given to the transmission unit 30-n of the same subscriber device 3-n. The transmission unit 30-n performs transmission processing in synchronization with this main clock.

As shown in FIG. 3, the transmitter 30-n of the subscriber device 3-n spreads the data signal formed in synchronization with the clock extracted by the receiver 20-n, which is defined for each subscriber. A diffusion modulation unit 31-n that diffusely modulates with a code, a synchronization signal generation unit 32-n that generates a synchronization signal and gives it to the diffusion modulation unit 31-n, and a variable phase shifter 33-N that finely adjusts the transmission timing. Has. The variable phase shifter 33-N has, for example, a delay circuit configuration.

The spread signal transmitted from each subscriber device 3-n is multiplexed by the distribution multiplier 4 and input to the station side device 2.

The station-side device 2 includes a distributor 49 and a receiver 40-n of each channel as a reception configuration. The received signal (multiplex signal) of the station side device 2 is N-branched by the distributor 49 and input to the receiving units 40-n of each channel. When the transmission line is an optical fiber, an optical / electrical conversion configuration is provided in the front stage of the distributor 49 or the input stage of the receiving unit 40-n.

FIG. 4 is a block diagram showing a detailed configuration of the receiver 40-n of the station side device 2 to which the branch signal from the distributor 49 is given.

In FIG. 4, each receiving unit 40-n of the station side device 2 performs a correlation calculation (reverse spreading processing) between the received signal (multiple signal) and the spreading code, and generates a correlated output signal for the corresponding channel (MF). ) Detects synchronization signals from the gate 45-n that latches the output of the matched filter 41-n with the main clock output from the variable phase shifter 43-n, which will be described later, and the output of the gate 45-n. It has a synchronization signal detection unit 42-n.

The variable phase shifter 43-n is arranged between the main clock generator 14 and the gate portion 45-n. The variable phase shifter 43-n changes the phase of the main clock generated from the main clock generator 14 according to the correction information described later.

FIG. 5 is a block diagram showing a conceptual configuration of each part that functions during skew adjustment according to the first embodiment.

In FIG. 5, the station-side device 2 includes a control unit (main control means) 50 that sequentially adjusts and controls the skew generated in the reception unit 40-x for each channel. Further, the control unit (main control means) 50 controls the control information generation unit 51, the reception unit 40-x, the variable phase shifter 43-x, and the transmission unit 10-n.

Further, the subscriber device 3-n includes a control unit (subordinate control means) 52-n that adjusts and controls the skew of the reception unit 40-x in cooperation with the control unit 50 of the station side device 2.

Further, in FIG. 5, the station-side device 2 includes a control information generation unit (reception phase setting unit) 51. The control information generation unit 51 generates and outputs two types of information.

The first information generated by the control information generation unit 51 is code information (transmission signal) that specifies the diffusion code used for transmission of the subscriber device 3-n. The generated code information is given to the transmission unit 10-n and transmitted to the subscriber device 3-n by the transmission unit 10-n. The transmission unit 10-n includes not only a function of transmitting information such as code information but also a function of transmitting a transmission permission signal for which a diffusion code is specified (transmission permission signal transmission unit, etc.).

The second information generated by the control information generation unit 51 is the correction information of the latch timing for the reception unit 40-x (x is an integer from 1 to N). The generated correction information is given to the variable phase shift unit 43-x, and controls the phase shift amount (delay amount) of the variable phase shift unit 43-x. The control information generation unit 51 corresponds to, for example, a portion made of software or hardware that executes communication control in the station side device 2.

The receiving unit 20-n of the subscriber device 3-n receives the code information from the transmitting unit 10-n. The code information taken out by the receiving unit 20-n is given to the control unit 52-n.

The control unit 52-n controls the xth diffusion code supplied to the diffusion unit 31-n according to the code information. The control unit 52-n causes the synchronization signal encoded by the xth spreading code to be sequentially and repeatedly transmitted. That is, under the control of the control unit 52-x, the transmission signal from the subscriber device 3-n encoded by the xth spreading code is given to the station side device 2.

When a transmission signal is input to the receiving unit 40-x of the station side device 2, the synchronization signal detection result is output from the synchronization signal detection unit 42-n (not shown in FIG. 5) inside the receiving unit 40-x. It is fed back to the control information generation unit 51.

That is, when the receiving unit 40-x receives the signal from the station side device 2, the variable phase shifter 43-x changes the latch timing of the received signal by a predetermined period inside the receiving unit 40-x. Further, the synchronization signal detection unit 42-n diffuses and demodulates the signal from the fixed signal of the received signal and determines whether or not the signal can be effectively received. Then, the control information generation unit 51 detects the optimum reception phase within the range in which the fixed signal can be detected, and sets this as the reception phase of the reception unit 40-x.

(A-2) Operation of the first embodiment Hereinafter, the operation of the communication system 1 of the first embodiment will be described separately for a normal transmission operation, a skew adjustment operation, and a synchronization establishment operation after the skew adjustment.

(A-2-1) Normal communication operation First, a normal transmission operation from the station side device 2 to each subscriber device 3-n will be described. In this normal transmission operation, it is assumed that synchronization as a system has already been established for each subscriber device 3-n.

In the station side device 2, each of the transmission units 10-n of each channel generates a synchronization signal of its own channel, spread-modulates it with the diffusion code of its own channel, and then obtains a modulated signal (diffusion signal) of each channel. It is multiplexed by the addition unit 11 and sent to the common transmission line 5.

FIG. 6 is an explanatory diagram showing a configuration of communication signals exchanged between the station side device 2 and a certain subscriber device 3-n. The configuration of the communication signal is the same in both the up direction and the down direction.

The communication signal is composed of repeating fixed-length synchronization signals. The synchronization signal is divided into a fixed signal and a control signal. The fixed signal is a bit string having a predetermined pattern, and is used by the receiving side to detect the start position of the frame and to establish synchronization as described later. The control signal is a control signal for the station side device 2 to control the subscriber device 3-n, and the subscriber device 3-n reads the control signal and controls the inside of the own device. The control signal is also used when the subscriber device 3-n returns a control response to the station side device 2.

The output signal (multiplex signal) from the station side device 2 is N-branched via the distribution multiplier 4 and given to each subscriber device 3-n.

Each subscriber device 3-n reverse-spreads the received signal using the spreading code assigned to the own channel, and generates a correlation output signal (MF output signal) for the own channel. This MF output signal is input to the clock reproduction unit 24-n, and the clock reproduction unit 24-n reproduces the main clock (for example, a phase comparison between the MF output signal and the own oscillator output is performed using a PLL circuit). Form the main clock by doing). In addition, the gate section 25-n latches the MF output signal with the main clock to determine the received data.

Here, the principle of diffusion modulation and back-diffusion processing applied by the first embodiment will be described with reference to FIG. 7.

Diffuse modulation is an operation of converting each bit of a signal (digital signal) to be transmitted into a pattern having an interval shorter than the bit interval of the signal to be transmitted by using a predetermined bit string (FIGS. 7 (a) to 7 (b)). Refers to the operation of converting to. A predetermined bit string used for conversion is called a spreading code, and the spreading code is unique for each channel. When spreading the "1" and "0" of the signal to be transmitted, for example, a bit-inverted code is used. When the diffusion signal after diffusion modulation is inversely diffused with the same code (autocorrelation is taken), strong positive and negative peaks appear at each bit interval (Fig. 7 (c), (d)). If the threshold value processing is performed at the phase position where this peak appears, the transmitted signal can be taken out. On the other hand, when inversely diffused with different codes (cross-correlation is taken), peaks such as autocorrelation do not appear (Figs. 7 (e) and (f)). In particular, when the code used for diffusion is a Walsh-Hadamard sequence, there is no sound (MF output signal (correlation output) is 0) at the phase position where the peak appears by autocorrelation. As described above, even when a plurality of diffusion signals modulated with different diffusion codes are multiplexed, the transmission signal can be restored without interfering with each other on the receiving side (reverse diffusion processing side).

The extracted synchronization signal is given to the control unit 52-n in the upper layer of the subscriber device 3-n, and is used when synchronization is established.

Each subscriber device 3-n also generates a synchronization signal of its own channel, spread-modulates it with the spreading code of its own channel, and then sends it out.

The modulated signal (diffusion signal) from each subscriber device 3-n is multiplexed by the distribution multiplexing device 4 and then input to the station side device 2.

In the station side device 2, the received signal (multiplex signal) is N-branched by the distributor 49 and input to the receiving units 40-n of each channel.

Each receiving unit 40-n performs despreading processing on the received signal using the spreading code assigned to the own channel, and generates a correlation output signal (MF output signal) for the own channel. The gate portion 45-n determines the received data by latching the MF output signal with the main clock.

The synchronization signal detection unit 42-n captures the phase shift between the phase of the synchronization signal and the in-station phase, and gives the phase shift information to the upper layer control unit that functions as the control information generation unit 51. Is used in the range and the like described later.

(A-2-2) Operation of skew adjustment method Next, the operation of the skew adjusting method of the first embodiment will be described with reference to FIG.

FIG. 8 is a flowchart showing the operation of the skew adjustment method of the first embodiment. Since the skew adjustment method of the first embodiment includes the first to seventh steps, the processing contents will be described step by step in order from the first step.

The first step S10 is a step in which a transmission stop signal is transmitted from the station side device 2 to all of the subscriber devices 3 to put all of the subscriber devices 3 in the standby state. When the subscriber device 3 receives the transmission stop signal, each subscriber device 3 can receive the downlink signal, but cannot transmit the uplink signal.

The second step S20 is a step of transmitting a transmission permission signal and a signal designating the xth diffusion code as the transmission code from the station side device 2 to the subscriber device 3-n. Where n is any integer from 1 to N. x is an integer from 1 to N, with an initial value of 1 (step S15). This x corresponds to the channel to be skewed. When the subscriber device 3-n receives these two signals, the subscriber device 3-n encodes the synchronization signal using the xth spreading code and starts transmission to the station side device 2. ..

The second step S20 may be executed following the step S75 described later. In this case, the subscriber device 3-n is in a state of continuing to transmit the synchronization signal encoded by the diffusion code of the (x-1) th. When a signal that specifies the x-th diffusion code as the transmission code is received in this state, as shown in FIG. 9, the synchronization signal can always be continuously transmitted at the same cycle without any interval at the change of the code. is important.

The third step S30 is a step in which the receiving unit 40-x in the station side device 2 attempts to receive the synchronization signal transmitted from the subscriber device 3-n in the second step S20. At this time, the phase shift amount of the variable phase shifter 43-x is set to m · Δt. m is an integer from 0 to M, and Δt is the phase shift step amount.

The relationship shown in Eq. (1) holds between the maximum value M of the variable m, the phase shift step amount Δt, and the bit spacing in the data signal.

M · Δt = bit spacing ... (1) The fourth step S40 is a step of determining whether or not the value of the variable m described in the third step S30 is equal to M.

The fifth step includes the steps shown as S50 and S55 in FIG. If the condition of the fourth step is determined to be true, the process proceeds to step S50, and if it is determined to be false, the process proceeds to step S55.

Step S55 is a step of increasing the variable m by 1. After that, the process returns to the third step S30.

The loop of steps S30, S40, and S55 means that the timing (the amount of phase shift of the main clock) at which the receiving signal is latched by the receiving unit 40-x is set to 0, 1 · Δt, 2 · Δt, ... , M · Δt, and it is determined whether or not the synchronization signal can be received at each latch timing. After all the judgments of M + 1 times are completed, the process proceeds to the next step S50.

In step S50, the range AR in which the fixed signal obtained by executing the above loop can be detected is taken into consideration (see FIG. 10), and the values i · Δt at the center of the range AR are set to the optimum phase amount. The control information generation unit 51 sets the phase shift amount of the variable phase shifter 43-x to this optimum phase shift amount, and establishes (fixes) the reception timing. By executing the above steps, the skew adjustment of the receiver 40-x is completed.

The sixth step S60 is a step of determining whether or not the variable x is equal to N. That is, it is determined whether or not the skew adjustment of all the receiving units 40 is completed.

The seventh step includes the steps shown as S70 and S75 in FIG. If the condition of the sixth step is determined to be true, the process proceeds to step S70, and the skew adjustment of all the receiving units 40 is completed. If it is determined to be false, the process proceeds to step S75, and the value of the variable x is incremented by 1. After that, the process returns to the second step S20, and the skew adjustment of the next receiver is executed.

(A-2-3) Synchronization establishment operation Next, after performing skew adjustment for each channel in the receiving circuit of the station side device 2, the synchronization establishment operation (ranging) in the communication system 1 will be described. The synchronization establishment operation is mainly performed by the control unit in the upper layer of the transmission unit and the reception unit.

Here, the terminizing means synchronizing the phases of the transmission signals from all the subscriber devices 3-1 to 3-N. Ranger corrects the difference in data (transmission signal) transmission time because the transmission path distance from the station side device 2 to each subscriber device 3-n is different for each subscriber device 3-n. It is a process for.

First, the station side device 2 (control unit (not shown) causes all subscriber devices 3-1 to 3-N to transmit a communication stop command (transmission signal) to all subscriber devices 3-1. Put ~ 3-N in standby mode.

The communication stop command may be a range start command.

In the case of the first embodiment, after that, under the control of the station-side device 2, a process of determining the phase one channel at a time from channel CH1 to channel CHN is performed.

The phase determination process (ranging process) of each channel is the same, and channel CH1 will be described below with reference to FIGS. 10 and 11. During the range processing for channel CH1, the station side device 2 and the subscriber devices 3-2 to 3-N of other channels do not execute communication. Further, the receiver 40-n of the station side device 2 is skew-adjusted for each channel.

(S1) In FIG. 11, the station side device 2 transmits a transmission permission signal to the subscriber device 3-1. The transmission permission signal consists of one or more repetitions of the same synchronization signal, and the control signal in the synchronization signal controls the variable phase shifter 33-1 in the transmission unit 30-1 of the subscriber device 3-1. Information (phase shift amount information) is entered.

(S2) After receiving the transmission permission signal, the subscriber device 3-1 reads the phase shift amount information entered in the synchronization signal, sets the phase shift amount of the variable phase shifter 33-1, and responds. The signal is transmitted to the station side device 2. This response signal consists of one or more repetitions of the same sync signal.

(S3) The station side device 2 attempts to receive the fixed signal in the response signal sent from the subscriber device 3-1 by the receiving unit 40-1. Whether or not reception synchronization was possible is determined based on whether or not the fixed signal could be received without error.

The above operations (S1) to (S3) are repeated M times as shown in FIG. However, the phase amount information is increased by Δt for each repetition. At this time, the relationship shown in Eq. (1) holds between the number of repetitions M, the phase shift step amount Δt, and the bit interval in the data signal.

M · Δt = bit spacing ... (1) Here, there are many combinations of M and Δt. Increasing M allows the amount of phase shift to be adjusted accurately, but increases the time required for one range. Decreasing M increases the error in the amount of phase shift, but reduces the time required for one range. Since there is a so-called trade-off relationship, the values of M and Δt are appropriately determined according to the environment.

After repeating the above operations (S1) to (S3) M times, the station side device 2 looks at the range AR in which the fixed signal can be detected as shown in FIG. 10, and the value i · Δt at the center of the range AR. Is set to the optimum phase amount. As shown in FIG. 11, the station-side device 2 transmits a range-up completion notification in which the optimum phase shift amount is entered to the subscriber device 3-1 to establish (fix) the transmission phase of the subscriber device 3-1. ..

After that, as shown in FIG. 11, the station-side device 2 shifts to the range processing for the subscriber device 3-2 of the channel CH2, and similarly, the range processing for the subscriber device 3-2 of the channels CH3 to CHN is performed. Execute sequentially.

(A-3) Effect of the first embodiment As described above, according to the first embodiment, even if each receiving unit 40 in the station side device 2 has a skew, the skew can be brought close to zero by following the above procedure. Further, if the skew adjustment procedure of the first embodiment is executed and then the range processing of the conventional example is performed, reliable code synchronization can be established.

(B) Other embodiments The application of the 1-to-N communication system of the present invention is not limited. That is, the transmission line is not limited to PON (passive optical network), and the transmission line may be an electrical transmission line.

In the first embodiment, the case where the matched filter is used as the configuration for obtaining the correlation output for diffusion demodulation is illustrated, but another correlation calculation configuration such as a sliding correlator may be applied.

In the first embodiment, the range in which the phase is shaken is 1 bit interval (Δt to M · Δt), but the phase is shaken in a narrower range to determine a new optimum phase shift amount. You may do so. Further, although the phase change is shown to be gradually increasing, other change methods may be applied. For example, it may be a gradual decrease. Further, for example, a conversion method based on the dichotomy method or other search methods may be applied.

<figref num="1">It is a block diagram which shows the whole structure of the communication system of 1st Embodiment, and the transmission structure of a station side apparatus.</figref><figref num="2">It is a block diagram which shows the reception structure of the subscriber apparatus of 1st Embodiment.</figref><figref num="3">It is a block diagram which shows the transmission configuration of the subscriber apparatus of 1st Embodiment, and the whole configuration of the communication system along the flow of the transmission signal from the transmission part to the station side apparatus.</figref><figref num="4">It is a block diagram which shows the reception structure of the station side apparatus of 1st Embodiment.</figref><figref num="5">It is a block diagram which shows the conceptual structure of each part which functions at the time of skew adjustment of 1st Embodiment.</figref><figref num="6">It is explanatory drawing which shows the structure of the communication signal between a station side apparatus and a subscriber apparatus in 1st Embodiment.</figref><figref num="7">It is explanatory drawing of the principle of diffusion modulation and back diffusion processing of 1st Embodiment.</figref><figref num="8">It is a flowchart explaining the operation of the skew adjustment method in the receiving part of the station side apparatus of 1st Embodiment.</figref><figref num="9">It is explanatory drawing explaining the transmission timing of the synchronization signal of 1st Embodiment.</figref><figref num="10">It is a timing chart which shows the autocorrelation output which concerns on the skew adjustment processing and the range processing of 1st Embodiment.</figref><figref num="11">It is a sequence diagram for demonstrating the range operation of 1st Embodiment.</figref>

Code description

1 ... 1 to N communication system, 2 ... Station side equipment 10-1 ~ 10-N ... Transmitter, 11 ... Adder, 12-1 ~ 12-N ... Diffuse 13-1 ~ 13-N ... Synchronous signal generator, 40-1 ~ 40-N ... Receiver, 41-1 ~ 41-N ... Matched Filter, 42-1 ~ 42-N ... Synchronous signal detector, 43-1 ~ 43-N ... Variable phase shifter, 44-1 ~ 44-N ... Clock playback section, 45-1 ~ 45-N ... Gate section, 49 ... Distributor, 51 ... Control information generator, 3-1 ~ 3-N ... Subscriber equipment, 20-1 ~ 20-N ... Receiver, 21-1 ~ 21-N ... Matched Filter, 22-1 ~ 22-N ... Synchronous signal detector, 23-1 ~ 23-N ... Variable phase shifter, 24-1 ~ 24-N ... Clock playback part, 25-1 ~ 25-N ... Gate part, 30-1 ~ 30-N ... Transmitter, 31-1 ~ 31-N ... Diffusion Modulator, 32-1 ~ 32-N ... Synchronous signal generator, 33-1 ~ 33-N ... Variable phase shift part, 52-1 ~ 52-N ... Control unit, 4 ... Distribution multiplier, 5 ... common transmission line, 6-1 ~ 6-N ... Individual transmission line.