JPH10243371A - Data communication device and data communication method - Google Patents

Abstract

(57) [Summary] A registration process is surely completed without lowering the transmission efficiency and the calculation accuracy of a pre-equalization coefficient. An uplink schedule creation circuit causes an initial ranging request to be transmitted on a narrow-band initial registration channel and sets a long preamble according to a schedule for initial registration of a terminal. The initial ranging request from the terminal 3 is transmitted on the initial registration channel, and its preamble length is long. As a result, the terminal address can be reliably identified from the initial ranging request in the center device 1, and the registration process can be completed without affecting the transmission efficiency of other burst signals and the calculation accuracy of the pre-equalization coefficient. Can be.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data communication apparatus and a data communication method suitable for registering a user terminal in an asymmetric data communication system using a CATV network.

[0002]

2. Description of the Related Art In recent years, CATV (cable television) using a coaxial cable, an optical fiber cable, or the like as a transmission path has become widespread. Paying attention to the large capacity and bidirectionality of CATV, the use of CATV for multimedia has recently been considered. In addition, taking advantage of the fact that CATV has been increased in scale and multi-channel, CT
Asymmetric data communication systems using an AV network as a transmission path are also being constructed. For an overview of an asymmetric data communication system using a CATV network, see the document "Introduction to Cable TV Technology-From Basics to Applications-" (Corona)
(Edited by the Japan Electronic Opportunity Manufacturers Association, CATV Technical Committee) and the like.

[0003] In CATV, a center device and each terminal are connected via a cable network. When the service range becomes large, the propagation delay between the center device and the terminal device cannot be ignored, and the transmission delay time needs to be corrected. Further, it is necessary to provide a pre-equalization filter in order to remove interference such as a transmission path.

In order to correct the transmission delay time and set the tap coefficients of the pre-equalization filter, ranging processing shown in the following steps 1 to 4 is performed between the center device and the terminal device.

[0005] 1. The center apparatus instructs a predetermined terminal to transmit a predetermined signal (ranging request) at a predetermined time.

[0006] 2. The terminal receiving this instruction transmits a ranging request at the instructed time.

[0007] 3. The center apparatus receives the ranging request transmitted by the terminal, measures the transmission delay time, calculates the tap coefficient of the pre-equalization filter (hereinafter, referred to as pre-equalization coefficient), and transmits the calculated value to the terminal.

[0008] 4. When the terminal receives the information of the transmission delay time and the pre-equalization coefficient, the terminal sets the coefficient in the pre-equalization filter. The terminal pre-equalizes the uplink signal based on the pre-equalization coefficient when transmitting the subsequent uplink signal. In addition, transmission is started at a timing earlier than the instructed time by a time in consideration of the transmission delay time.

The ranging request transmitted from the terminal is composed of a preamble and data indicating an address unique to the terminal.

[0010] Such ranging processing is periodically performed between the center apparatus and the terminal apparatus, so that the settings of the transmission delay time and the pre-equalization coefficient are maintained at optimal values.

[0011] The ranging process is also performed in the registration process performed when the terminal is first connected to the cable network. That is, in the registration process, the following five steps are executed.

1. The center device instructs all the terminals that perform the registration process with the transmission time of the ranging request.

2. Upon receiving the instruction, the terminal that performs registration transmits a ranging request at a specified time.

3. The center device receives the ranging request from the unregistered terminal, measures the transmission delay time and calculates the pre-equalization coefficient, and identifies the terminal address in the ranging request. The center device transmits the calculated transmission delay time and the pre-equalization coefficient to the end of the identified address.

4. The terminal receives the information of the transmission delay time and the pre-equalization coefficient from the center device, and sets the coefficient in the pre-equalization filter.

5. The terminal starts communication required for registration in consideration of the transmission delay time while following instructions from the center device.

As described above, the pre-equalization coefficient for removing the distortion based on the transmission path is set to an optimum value by the ranging process. However, the unregistered terminal cannot grasp the state of the transmission path at all, and the tap coefficient of the pre-equalization filter is not set to the optimum value for the unregistered terminal.
Therefore, in the ranging request (initial ranging request) transmitted first by the terminal in the registration process, sufficient pre-equalization is not performed.

Therefore, there is a high probability that the center device cannot identify the terminal address included in the initial ranging request. If the center device cannot identify the terminal address, the center device
It becomes impossible to transmit data such as tap coefficients of the pre-equalization filter to the terminal.

In this case, the terminal performs the registration process again. However, even in this case, since the transmission conditions are not improved, there is a high probability that the center device fails to identify the terminal address. That is, there is a problem that the registration process may be repeated many times depending on the transmission conditions.

It is also possible to increase the probability that the center device can identify the terminal address by appropriately setting the parameters of the ranging request, that is, the preamble length, the symbol rate, the modulation method, and the like. For example, it is conceivable to increase the preamble length and decrease the symbol rate.

However, if the length of the preamble is increased, the redundancy increases and the data transmission efficiency deteriorates. Further, since the tap coefficient of the pre-equalization filter is calculated based on the ranging request, if the symbol rate of the ranging request is set lower than that of the other burst signals, the tap coefficient of the pre-equalization filter is changed for other burst signals. Calculation cannot be performed with sufficient accuracy.

[0022]

As described above, conventionally, in a setting where sufficient transmission efficiency and tap coefficient calculation accuracy of the pre-equalization filter are obtained, the terminal address included in the initial ranging request cannot be identified. However, there has been a problem that the registration process of the terminal connected to the cable network may not be completed.

The present invention has been made in view of such a problem, and is intended to ensure that a terminal connected to a cable network can be securely connected even if the setting is such that sufficient transmission efficiency and tap coefficient calculation accuracy of a pre-equalization filter are obtained. It is an object of the present invention to provide a data communication apparatus and a data communication method capable of completing the registration processing of the data communication system.

[0024]

According to a first aspect of the present invention, there is provided a data communication apparatus for transmitting an uplink signal to a center device via a transmission line, and for performing initial registration of a terminal in the uplink signal. And an initial registration unit for making at least one of the format and the transmission condition of the transmission line used for transmission different from the other uplink signals, and the data according to claim 6 of the present invention. The communication device is a schedule transmission unit that creates a schedule for controlling data transmission from the terminal and sends the schedule to a transmission line, and a transmission channel for an uplink signal from the terminal based on a schedule for initial registration of the terminal. Initial registration setting means for specifying a channel of a narrower band than a transmission channel of an uplink signal from a terminal based on another schedule. The data communication apparatus according to claim 7 of the present invention, wherein a schedule transmission means for creating a schedule for controlling data transmission from a terminal and transmitting the schedule to a transmission path, and for initial registration of the terminal. And an initial registration setting means for setting a preamble of an uplink signal from the terminal based on a schedule to a preamble length longer than a preamble of an uplink signal from a terminal based on another schedule. The data communication method according to the first aspect includes a first transmission procedure of transmitting an uplink signal for initial registration of a terminal to a center device via a transmission path, and a format of an uplink signal other than the uplink signal for the initial registration. And a second condition that makes at least one of the transmission conditions of the transmission path used for transmission different from the uplink signal for the initial registration. It is obtained by and a signal procedures.

According to the first aspect of the present invention, the initial registration means determines that at least one of the format of the uplink signal for the initial registration and the transmission conditions of the transmission path used for the transmission is different from the other uplink signals. Is set. The transmitting means transmits the upstream signal to the center device via the transmission path. In the center device, the uplink signal for the initial registration and the other uplink signal are identified under mutually different conditions, and it becomes possible to easily identify the uplink signal for the initial registration.

[0026] In claim 6 of the present invention, the initial registration setting means sets the transmission channel of the uplink signal from the terminal based on the schedule for the initial registration to a narrower band than the transmission channels of the other uplink signals. The schedule transmitting means creates and transmits a schedule for controlling data transmission of the terminal. As a result, the uplink signal for initial registration is transmitted from the terminal on a relatively narrow channel, and the other uplink signals are transmitted on a relatively wide channel. As a result, the distortion of the uplink signal for initial registration in the transmission path is reduced more than other uplink signals.

[0027] In claim 7 of the present invention, the initial registration setting means sets the preamble of the uplink signal from the terminal based on the schedule for the initial registration to a longer preamble length than the preambles of other uplink signals. As a result, the uplink signal for initial registration has a higher identification probability than other uplink signals.

According to claim 8 of the present invention, an uplink signal for initial registration is transmitted by the first transmission procedure. In the second transmission procedure, an uplink signal other than the uplink signal for initial registration is transmitted by making at least one of the format and transmission conditions of the transmission line used for transmission different from the uplink signal for initial registration. I do. Thereby, the identification probability of the uplink signal for initial registration is improved as compared with other uplink signals.

[0029]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of a data communication device according to the present invention.

In a ranging process other than the initial ranging process which is normally performed periodically for each terminal, the center device is configured to instruct a timing of transmitting a ranging request to each terminal for each terminal. . Therefore, even when the center device cannot identify the terminal address in the ranging request, as in the case where the ranging request is transmitted in a state where the pre-equalization is not sufficient, any one of the ranging requests depends on the arrival time of the ranging request. The center device can determine whether the ranging request has been transmitted from the terminal. Therefore, only in the case of the initial ranging process at the time of registration, the setting may be made so that the center device can reliably identify the terminal address.

For this reason, in this embodiment,
By changing the setting at the time of the initial ranging request in the initial registration process and the setting at the time of transmitting another burst signal, the center for the initial range request can be reduced without lowering the transmission efficiency and the tap coefficient calculation accuracy of the pre-equalization filter. The terminal address identification probability of the device is improved. However, there is a system in which only the same setting is allowed in the same channel due to the standard in the data communication system. Therefore, in the present embodiment, a channel for transmitting an initial ranging request and a channel for transmitting another burst signal are switched.

In FIG. 1, a center device 1 and a terminal 3 are connected by a cable network 2. The center device 1 includes an uplink schedule creation circuit 5, a downlink signal transmission block 6, a duplexer 7, an uplink signal reception block 8, a terminal address identification circuit 9, a delay measurement circuit 10, a pre-equalization coefficient calculation circuit 11, and a ranging response creation. The circuit 12 is configured.

The upstream schedule creation circuit 5 creates a schedule according to various communication protocols with the terminal. The schedule information created by the uplink schedule creation circuit 5 is supplied to the downlink signal transmission block 6. Examples of the schedule include an outgoing schedule (initial ranging schedule) for a terminal desiring registration, a normal ranging schedule, and a schedule for data communication. The information on these schedules includes information on the transmission timing of the ranging request and the like, the uplink channel used for transmission, the information on the preamble length, and the like.

In the present embodiment, the upstream schedule creation circuit 5 designates, as the initial ranging schedule, a channel having the narrowest band among a plurality of available transmission channels as an upstream channel, and transmits another burst signal when transmitting another burst signal. A longer preamble length is specified. In addition, the upstream schedule creation circuit 5 generates a normal ranging schedule as
The same channel and preamble length setting as in the transmission of other burst signals except for the initial ranging schedule are designated.

FIG. 2 is an explanatory diagram for explaining the preamble length of the initial ranging request. FIG.
FIG. 2A shows an initial ranging request, and FIG.
(B) shows a normal ranging request. In FIG. 2, the vertical direction indicates the band (symbol rate), and the horizontal direction indicates the time required for transmission. In addition,
The product of the transmission time and the rate is a bit length.

FIG. 2 shows an example in which the initial ranging request is transmitted at a rate of 1 Mbps (bits / second), and the ranging request is transmitted at a rate of 4 Mbps. As shown in FIG. 2A, the initial ranging request includes a 7t preamble, a 2t header, and a 4t terminal address. As shown in FIG. 2B, the normal ranging request is configured by arranging a preamble of 1t time, a header of 0.5t time, and a terminal address of 1t time.

That is, the bit lengths of the header and the terminal address are the same in the initial ranging request and the normal ranging request, but the preamble length of the initial ranging request is longer in both the transmission time and the bit length than the normal ranging request. Is also long. Assuming that the modulation method and the coefficient of the band limiting filter are the same, the bit rate and the bandwidth are proportional, and FIG. 2 shows that the initial ranging request is transmitted in a band narrower than the normal ranging request. ing.

It should be noted that the uplink schedule creation circuit 5 may set only one of the preamble length and the transmission band to be different between the initial ranging request and other burst signals.

The downstream signal transmission block 6 multiplexes a plurality of pieces of input information, converts the multiplexed information into packets that can be transmitted through the cable network 2, modulates the packets, and outputs the packets to the duplexer 7.
The demultiplexer 7 transmits the packet from the downstream signal transmission block 6 to the cable network 2 and transmits the packet from the cable network 2 to the upstream signal reception block 8
To be supplied.

The upstream signal receiving block 8 demodulates a packet of the received upstream signal and extracts an upstream signal such as a ranging request. The upstream signal receiving block 8 outputs the received ranging request to the delay measuring circuit 10, the pre-equalization coefficient calculating circuit 11, and the terminal address identifying means 9.

The delay measuring circuit 10 measures the delay time on the transmission line based on the reception timing of the ranging request, which is an uplink signal from the terminal, and outputs the measured delay time to the ranging response creating circuit 12. The pre-equalization coefficient calculation circuit 11 calculates a pre-equalization coefficient according to the distortion state of the ranging request, which is an uplink signal from the terminal, and outputs the pre-equalization coefficient to the ranging response creation circuit 12. The terminal address identification circuit 9 identifies a terminal address included in the ranging request, which is an uplink signal, and outputs an identification result to the ranging response creation circuit 12 and the uplink schedule creation circuit 5.

The ranging response creation circuit 12 grasps the terminal based on the result of identifying the terminal address with respect to the initial ranging request, and completes the registration of the terminal. Create a ranging response that includes In addition, the upstream schedule creation circuit 5
Creates a normal ranging schedule and data communication schedule for a terminal for which registration processing has been completed.

The cable network 2 is, for example, a CATV
This is a transmission path configured by a network or the like, and performs data transmission between the center device 1 and the terminal 3.

The terminal 3 is a branching filter 21 and a downstream signal receiving block.
22, a ranging response extraction / analysis circuit 23, a ranging signal creation circuit 24, an uplink schedule extraction / analysis circuit 25, an uplink signal transmission block 26, a pre-equalization filter 27, and a transmission delay correction circuit 28.

The demultiplexer 21 supplies packet data, which is a downstream signal from the cable network 2, to the downstream signal receiving block 22, and transmits the packet data supplied from the transmission delay correction circuit 28 to the cable network 2 as an upstream signal. It is designed to be sent. The downlink signal receiving block 22 demodulates the received downlink signal and extracts schedule information, ranging response, and the like from the packet.

The upstream schedule extraction / analysis circuit 25 extracts and analyzes schedule information from the downstream signal receiving block 22. That is, the upstream schedule extraction analysis circuit 25
Knows the type of data to be transmitted, the channel to be used for transmission, the transmission timing, and the like from the schedule information, and outputs it to the ranging signal creation circuit 24 and the upstream signal transmission block 26 as an analysis result.

When the schedule information indicates that the ranging process based on the initial registration or the normal ranging process is to be executed, the ranging signal creating circuit 24 creates a ranging request based on these instructions and transmits the uplink signal. Output to block 26. The upstream signal transmission block 26 converts the ranging request or normal communication data supplied from the ranging signal generation circuit 24 into a packet that can be transmitted in the cable network 2 with a channel and transmission timing based on the analysis result and outputs the packet as an upstream signal. I do.

On the other hand, a ranging response extraction / analysis circuit
23 extracts and analyzes the ranging response received by the downlink signal receiving block 22. That is, the ranging response extraction / analysis circuit 23 obtains the transmission delay time and the pre-equalization coefficient included in the ranging response, and outputs them to the transmission delay correction circuit 28 and the pre-equalization filter 27, respectively.

The ranging response extraction / analysis circuit
When the ranging response to the initial ranging request is not obtained, the instruction 23 outputs an instruction for transmitting the initial ranging request again to the ranging signal creation circuit 24.

The pre-equalization filter 27 performs an equalization process on the upstream signal from the upstream signal transmission block 26 using the pre-equalization coefficient, and outputs the result to the transmission delay correction circuit 28. The transmission delay correction circuit 28 delays the upstream signal from the pre-equalization filter 27 by a set transmission delay time and transmits the signal from the duplexer 21 to the cable network 2.

Next, the operation of the embodiment configured as described above will be described with reference to FIGS. FIG. 3 is an explanatory diagram for explaining a usable band in the data communication system using the cable network 2, and FIG. 4 is a flowchart for explaining an operation of the embodiment.

It is assumed that there are a plurality of available transmission channels in a data communication system using the cable network 2, and that at least one channel has a narrower band than other channels.
FIG. 3 shows the band of such a transmission channel by taking the frequency on the horizontal axis. FIG. 3 shows an example having five transmission channels. A plurality of channels having a relatively wide band, for example, a channel in the highest frequency band in FIG. 3 is a data transmission channel, a channel having a relatively narrow band,
For example, the channel with the narrowest transmission band is the initially registered channel.

FIG. 4 shows a flow of processing between the center device and the terminal device in the initial registration of the terminal, the normal ranging process, and the normal data communication process. The left side of FIG. 4 shows the processing of the center device, and the right side shows the processing of the terminal. It is assumed that the terminal 3 has not been registered at present.

First, as shown in step S1 of FIG.
The uplink schedule creation circuit 5 of the center device 1 creates a registration request transmission schedule for initial registration at a predetermined timing. According to this schedule, the up channel to which the unregistered terminal 3 transmits the registration request and the transmission time are determined. In the present embodiment,
The uplink schedule creation circuit 5 sets the narrowest-band initial registration channel in FIG. 3 as a channel for transmitting an initial ranging request that is a registration request. Further, the upstream schedule creation circuit 5 instructs the preamble length of the initial ranging request to be longer than the preamble length of another burst signal.

The schedule from the uplink schedule creation circuit 5 is supplied to the downlink signal transmission block 6, multiplexed with other downlink data, and subjected to a predetermined modulation process.
The signal is transmitted to the cable network 2 via the duplexer 7 (transmission D1 in FIG. 4). The transmission D1 is performed by broadcast or multicast so that an unspecified number of unregistered terminals can receive the data.

On the terminal side, the process of step T1 is performed. That is, the branching filter 21 of the terminal 3 gives the input schedule information to the downlink signal receiving block 22. The downlink signal receiving block 22 demodulates the input packet to obtain schedule information and supplies the schedule information to the uplink schedule extraction / analysis circuit 25. The uplink schedule extraction analysis circuit 25 determines that the downlink signal is a schedule for initial registration, and outputs the determination result to the ranging signal creation circuit 24. In addition, the uplink schedule extraction analysis circuit 25 outputs to the uplink signal transmission block 26 information indicating that the initial registration channel is used as the transmission channel, information indicating that the preamble length is to be increased, and information of the transmission time as the analysis result of the schedule. I do.

The ranging signal generating circuit 24 is shown in FIG.
Is generated and output to the uplink signal transmission block 26. Uplink signal transmission block
26 modulates the input initial ranging request at a specified time on a specified channel and transmits it. This upstream signal is transmitted to the cable network 2 via the pre-equalization filter 27, the transmission delay correction circuit 28, and the duplexer 21 (transmission D2). At this time, since the pre-equalization coefficient and the transmission delay time are not supplied to the terminal 3 from the center device 1, the pre-equalization coefficient and the transmission delay time of the pre-equalization filter 27 and the transmission delay correction circuit 28 are It is set to a predetermined initial value.

The center device 1 receives an upstream signal from the cable network 2 via the branching filter 7. The upstream signal is input to the upstream signal receiving block 8, and the upstream signal receiving block 8 demodulates the upstream signal to obtain an initial ranging request signal, and receives a delay measurement circuit 10, a pre-equalization coefficient calculation circuit 11, and a terminal address identification circuit. 9 is output.

The delay measuring circuit 10 obtains a delay time to be set in the terminal 3 from the transmission time of the schedule for the initial registration and the arrival time of the uplink signal from the terminal 3. The pre-equalization coefficient calculation circuit 11 calculates a pre-equalization coefficient according to the distortion of the initial ranging request. The obtained delay time and pre-equalization coefficient are used in the ranging response creation circuit 12.
Supplied to

On the other hand, the terminal address identification circuit 9 identifies the terminal address of the terminal 3 included in the initial ranging request. In this case, using the preamble part of the initial ranging request,
Clock recovery and waveform equalization by L (phase locked loop) are performed. Since the preamble length is long, the removal of distortion due to the waveform equalization processing of the center device 1 is ensured, and the stability of clock reproduction is also improved.

Further, since the initial ranging request is transmitted through a narrow-band channel, even if the frequency characteristics such as the frequency-gain characteristic and the frequency-phase characteristic of the transmission path are poor, the gain of the transmitted initial ranging request can be reduced. Are relatively small and the phase rotation is relatively small.
Therefore, even when sufficient pre-equalization is not performed on the terminal side, the distortion of the transmitted initial ranging request is relatively small. For these reasons, the terminal address identification circuit 9 has a relatively high address recognition rate.

The center device 1 performs the registration processing of the terminal 3 based on the terminal address identified by the terminal address identification circuit 9. The terminal address identified by the terminal address identification circuit 9 is supplied to the ranging response creation circuit 12 and the uplink schedule creation circuit 5. The ranging response creating circuit 12 creates a ranging response of the terminal for which registration has been completed,
Output to The downstream signal transmission block 6 sends the input ranging response to the cable network 2 via the duplexer 7 with the identified terminal address as the destination address (transmission D3).

The terminal 3 fetches the transmission data via the duplexer 21, and the downlink signal receiving block 22 receives the ranging response. Ranging response extraction analysis circuit 23
Confirms that the registration was successful from the ranging response addressed to its own terminal in step T2.

The ranging response extraction / analysis circuit
If the ranging response of the transmission D3 cannot be extracted within a predetermined time from the transmission of the initial ranging request, it is determined that the registration processing has not been successful. In this case, the terminal transmits an initial ranging request again when the next schedule for the initial registration is transmitted.

Next, normal ranging processing is performed as preparation for normal data communication. The center apparatus 1 creates a schedule for a normal ranging process and outputs it to the downlink signal transmission block 6. In the present embodiment, the upstream schedule reproducing circuit 5 is a channel for transmitting a ranging request for normal ranging processing, for example, a channel having a band wider than the initial registration channel of FIG. 3 and is used for normal data communication. The data transmission channel is specified, and the preamble length is set to be shorter than the preamble length of the initial ranging request.
The downstream signal transmission block 6 transmits this schedule to the duplexer 7
Via the cable network 2 in unicast (transmission D4).

When the terminal 3 which has already completed the initial registration receives the schedule of the transmission D 4, the upstream schedule extraction / analysis circuit 25 analyzes the set transmission time, channel and preamble length, and analyzes the information. The signal is output to the ranging signal generation circuit 24 and the upstream signal transmission block 26.

Thus, the ranging signal creating circuit 24 creates the ranging request shown in FIG. This ranging request is sent by the upstream signal transmission block 26.
At a predetermined transmission time, the data is transmitted using the data transmission channel. The ranging request is sent to the cable network 2 via the duplexer 21 (transmission D5).

When the center device 1 receives the ranging request by the transmission D5, the delay measuring circuit 10 measures the delay time of the transmission line, and the pre-equalization coefficient calculation circuit 11 calculates the pre-equalization coefficient to be set in the terminal 3. . Also,
The terminal address identification circuit 9 identifies a terminal address from the ranging request. In this case, since the preamble length of the ranging request is relatively short, the stability of the PLL in the center device 1 and the performance of the equalization processing are relatively low. Further, since the transmission channel of the ranging request by the transmission D5 has a relatively wide band, the gain fluctuation and the phase rotation of the received ranging request are large.

However, even when the terminal address cannot be identified by the terminal address identification circuit 9, the scheduling request for ranging processing is transmitted by unicast designating each terminal. The terminal that has transmitted the ranging request can be reliably identified according to the time. The information of the identified terminal address is used as the ranging response creation circuit.
Supplied to 12.

Delay measuring circuit 10 and pre-equalization coefficient calculating circuit
Information on the delay time and the pre-equalization coefficient from 11 is supplied to the ranging response creating circuit 12. The pre-equalization coefficient is
This is in accordance with the state of the transmission path using the data transmission channel. A ranging response including the information of the delay time and the pre-equalization coefficient is created in the ranging response creation circuit 12, and transmitted by the downlink signal transmission block 6 with the terminal 3 as the destination address (transmission D6).

The downstream signal receiving block 22 of the terminal 3 receives the ranging response of the transmission D6 (step T4).
). The ranging response extraction analysis circuit 23 analyzes that the response is a normal ranging response, and sets the transmission delay time and the pre-equalization coefficient in the transmission delay correction circuit 28 and the pre-equalization filter 27, respectively. As a result, in the subsequent ranging processing and other communication processing, the transmission delay time correction and the pre-equalization processing are performed using the set transmission delay time and the pre-equalization coefficient.

For example, it is assumed that the schedule for normal communication shown in step S5 is created in the upstream schedule creating circuit 5 of the center device 1. In this case, the center device 1 designates a data transmission channel as a transmission channel for uplink data of the terminal 3. Transmission D
7 is analyzed by the upstream schedule extraction / analysis circuit 25, and the analysis result is supplied to the upstream signal transmission block 26. The upstream signal transmission block 26 transmits a predetermined upstream signal at a set time using a data transmission channel.

The upstream signal is pre-equalized by the pre-equalization filter 27, and is transmitted from the demultiplexer 21 after the transmission delay time is corrected by the transmission delay correction circuit 28 (transmission D).
8). In the pre-equalization process, since the pre-equalization coefficient according to the state of the transmission path using the data transmission channel is used, the waveform distortion of the uplink signal received by the center device 1 is sufficiently small. Thereby, the center device 1 and the terminal 3
Reliable data communication with the device.

As described above, in the present embodiment, the preamble length of the initial ranging request is set to be longer than the preamble length of the normal ranging request, and the initial ranging request is set to a band narrower than the transmission channel of another burst signal. Thus, the center device can reliably identify the terminal address from the initial ranging request. Further, since the preamble length of a normal ranging request is short, the redundancy is small and the data transmission efficiency is high. Also, in the normal ranging request, since transmission is performed using the channel used for normal data communication, the calculation accuracy of the pre-equalization coefficient obtained at the time of normal ranging processing is high, and this pre-equalization coefficient is used. By performing ordinary data communication, distortion of an uplink signal from a terminal can be sufficiently reduced.

In the present embodiment, as described above, either one of increasing the preamble length of the initial ranging request and using a narrow band channel as the transmission channel may be employed. Even in this case, it is clear that the identification probability of the terminal address can be improved.

FIG. 5 is a block diagram showing another embodiment of the present invention. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, an initial ranging request for initial registration is transmitted using a telephone line.

This embodiment is different from the embodiment shown in FIG. 1 in that a telephone line input circuit 34 is provided in the center device 31, and a registration signal creating circuit 35 and a telephone line output circuit 36 are provided in each terminal.

The telephone line input circuit 34 of the center device 1
An up signal from the telephone line 37 is taken in and supplied to the terminal address identification circuit 9.

The registration signal creation circuit 35 of the terminal 33 creates registration data and outputs it to the telephone line output circuit 36 when performing initial registration. Note that the registration data created by the registration signal creation circuit 35 is a signal including information on its own terminal address. The telephone line output circuit 36 converts the input registration data into a signal that can be transmitted to the telephone line 37 and sends the signal to the telephone line 37.

Next, the operation of the embodiment configured as described above will be described with reference to FIG. FIG. 6 is a flowchart for explaining the operation of the embodiment. FIG.
In FIG. 4, the same steps as those in FIG.

Registration signal generation circuit of terminal 33 for initial registration
Reference numeral 35 creates registration data necessary for initial registration in step T11 of FIG. The created registration data is supplied to the telephone line output circuit 36. The telephone line output circuit 36 converts the registered data into a signal that can be transmitted on the telephone line 37 and
Output to 37 (transmission D11). In this case, the telephone line 37
Thus, unlike the case of transmission via the cable network 2, there is no need to follow the schedule of the center device 31.

The registration data transmitted via the telephone line 37 is received by the telephone line input circuit 34 of the center device 31. The telephone line input circuit 34 supplies the received registration data to the terminal address identification circuit 9. The terminal address identification circuit 9 identifies the terminal address of the terminal 33 from the registered data and outputs it to the ranging response creation circuit 12 and the uplink schedule creation circuit 5. Thus, the initial registration of the terminal 33 in the center device 31 is completed.

Since the registration data is transmitted via the telephone line 37, the terminal address identification circuit 9 can reliably identify the terminal address.

The operations in the normal ranging process and the normal data communication are the same as those in the embodiment of FIG. 1 as shown in FIG.

As described above, also in this embodiment, FIG.
The same effect as that of the embodiment can be obtained.

[0086]

As described above, according to the present invention, even if the setting is such that sufficient transmission efficiency and tap coefficient calculation accuracy of the pre-equalization filter are obtained, the registration processing of the terminal connected to the cable network can be surely performed. Can be completed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a data communication device according to the present invention.

FIG. 2 is an explanatory diagram for explaining a ranging request.

FIG. 3 is an explanatory diagram for explaining channels used for transmission.

FIG. 4 is a flowchart for explaining the operation of the embodiment of FIG. 1;

FIG. 5 is a block diagram showing another embodiment of the present invention.

FIG. 6 is a flowchart for explaining the operation of the embodiment of FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Center apparatus, 2 ... Cable network, 3 ... Terminal, 5 ... Up-schedule creation circuit, 9 ... Terminal address identification circuit, 24 ... Ranging signal creation circuit, 27 ... Pre-equalization filter, 28 ... Transmission delay correction circuit

Claims (10)

[Claims] A transmission means for transmitting an uplink signal to a center device via a transmission line; a format of an uplink signal for initial registration of a terminal among the uplink signals and a transmission condition of the transmission line used for transmission; And an initial registration unit for making at least one of them different from other uplink signals. 2. The transmission path has a plurality of transmission channels having different bandwidths, and the initial registration unit transmits another uplink signal as a transmission channel for transmitting an uplink signal for the initial registration. 2. The data communication device according to claim 1, wherein a channel having a narrower band than the band of the channel is selected. 3. The uplink signal has a predetermined preamble, and the initial registration unit sets a preamble length longer than the length of the preamble of another uplink signal as a preamble of the uplink signal for the initial registration. The data communication device according to claim 1, wherein: 4. The transmission path has a plurality of transmission channels having different bandwidths, the uplink signal has a predetermined preamble, and the initial registration unit transmits the uplink signal for the initial registration. A channel having a narrower band than the band of the transmission channel transmitting the other uplink signal is selected as the transmission channel to be transmitted, and a preamble length longer than the preamble length of the other uplink signal is used as the preamble of the uplink signal for the initial registration. 2. The method according to claim 1, wherein
A data communication device according to claim 1. 5. The data communication device according to claim 1, wherein the transmission path is a telephone line. 6. A schedule transmission means for creating a schedule for controlling data transmission from a terminal and transmitting the schedule to a transmission line, and a transmission channel for an uplink signal from the terminal based on a schedule for initial registration of the terminal. A data communication device comprising: an initial registration setting unit that specifies a channel of a narrower band than a transmission channel of an uplink signal from a terminal based on another schedule. 7. A schedule transmitting means for creating a schedule for controlling data transmission from a terminal and transmitting the schedule to a transmission line, and transmitting a preamble of an uplink signal from the terminal based on a schedule for initial registration of the terminal. An initial registration setting unit for setting a preamble length longer than a preamble of an uplink signal from a terminal based on another schedule. 8. A first transmission procedure for transmitting an uplink signal for initial registration of a terminal to a center device via a transmission path, and for formats and transmissions of uplink signals other than the uplink signal for initial registration. And a second transmission procedure for making at least one of the transmission conditions of the transmission path used for the transmission different from the uplink signal for the initial registration. 9. The transmission path has a plurality of transmission channels having different bandwidths, and the second transmission procedure includes the initial transmission channel for transmitting an uplink signal other than the uplink signal for the initial registration. 9. The data communication method according to claim 8, wherein a channel wider than a band of a transmission channel for transmitting an uplink signal for registration is designated. 10. The uplink signal has a predetermined preamble, and the second transmission procedure includes a preamble of the uplink signal for the initial registration as a preamble of an uplink signal other than the uplink signal for the initial registration. The data communication method according to claim 8, wherein a preamble length shorter than the length of the preamble is set.