JPH11234233A - Hybrid access system, center equipment, fiber node and user equipment to be used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber node in simple configuration. SOLUTION: At center equipment S1, a plurality of down-signals are respectively digitized by a plurality of A/D parts 11 and a down-transmissionsignal is generated later by time division multiplexing due to a time division multiplexing part 12. Then, this down-transmission-signal is electrically optically converted by an electric/optic converting part 13 and transmitted later to an optical fiber F1 for down. At a fiber node N1, the down-transmission-signal coming through the optical fiber F1 for down is received and optically electrically converted by an optic/electric converting part 21. Then, the multiplexing system of each down-signal made into electric signal is converted to frequency division multiplexing by a time division/frequency division converting part 22 and sent to a coaxial cable C by a filter 23 later. At user equipment U1, the signal of a frequency band previously allocated to the present equipment is extracted from the down transmission signal coming through the coaxial cable C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to communication between a center device and a user device, in which an optical transmission line is integrated with a non-optical transmission line such as a wireless transmission line, a metal line, or a coaxial cable. The present invention relates to a hybrid access system that can be performed via a route, and a center device, a fiber node, and a user device used in the hybrid access system.

[0002]

2. Description of the Related Art A typical example of a public network access system is an analog telephone, a mobile telephone or a CATV using a metal line. There is an increasing demand for bidirectionality.

[0003] For example, analog telephones have shifted to ISDN, and ADSL systems capable of transmitting higher-speed data.
(Asymmetric Digital Subscriber Line). In mobile phones as well, proposals have been made for a method capable of data transmission and a method capable of transmitting and receiving data at a higher speed using wireless communication. Furthermore, CAT
As for V, an urban CATV to which a two-way communication service can be added has emerged from a conventional one-way service.

[0004] As described above, when the service is shifted to a wider band, the transmission distance becomes shorter on the existing transmission line such as a metal line or a coaxial cable.
In a system requiring a large transmission distance, use of an optical fiber is considered.

[0005] However, it is not easy to connect all the center device and the user device using the optical fiber due to the cost and the labor of laying the optical fiber. Therefore, a fiber node is installed near the user device, and the fiber node and the center device are connected by an optical fiber, and the existing transmission path other than light is connected between the fiber node and the user device (about 100 m). The form to use is considered.

Specifically, for example, in the case of a metal line, if the service is broadened, the existing service range of, for example, 7 km cannot be provided. Therefore, a fiber node is provided in the middle, and the existing metal from the fiber node to the user is provided. A system using a line has been developed. Also, in the case of using radio, a metal line is used between the radio base station and the center, but when the distance between the center and the radio base station is longer than 10 km, an optical fiber has been used. In the future, in order to provide broadband services wirelessly, optical fiber communication between the center and the wireless base station will be indispensable. Also, in the case of an urban CATV, connecting each user-side device with a coaxial cable causes a problem of ingress noise in which living noise, radio waves, and the like are mixed in an upstream frequency band. Number of 50
The form of HFC (hybrid fiber coaxial), which is limited to about 0, is provided with one fiber node for each area, and does not increase inflow noise, is becoming common.

However, the fiber node is interposed between the center device and the user device as described above, the optical transmission path is provided between the center device and the fiber node, and the optical fiber is used between the fiber node and the user device. If connection is made via transmission paths, there are various problems as described below.

First, the HFC used for urban CATV
In the case of a system, a configuration is adopted in which a semiconductor laser is directly analog-intensity-modulated by a frequency multiplexed signal transmitted coaxially. However, in the case of HFC, the transmission band of the downlink signal from the center device to the user device is very large, from 70 MHz to 750 MHz, whereas the uplink signal from the user device to the center device is a part of the band of 10 MHz to 50 MHz. It just uses. Therefore, although the configuration of the center device is complicated, the scale of the electrical / optical signal converter in the fiber node is not so large. However,
With respect to the downstream signal, since the required performances such as linearity, noise, and reflected return light tolerance of the semiconductor laser are strict, it is necessary to select and use a distributed feedback semiconductor laser, and the center device cannot be easily realized. There is.
Further, there is a problem that the demand for a semiconductor laser installed in a fiber node is strict for an upstream signal, and it cannot be easily realized.

On the other hand, in a fiber / wireless hybrid access system, in order to simplify the configuration of a fiber node, a method of transmitting an optical signal obtained by analog light intensity modulation using a wireless electric signal as it is, In order to reduce the frequency of analog light intensity modulation, there has been considered a method of transmitting an optical signal obtained by performing analog light intensity modulation using a signal obtained by converting a wireless electric signal into an intermediate frequency band. Since the signal is an analog intensity modulated signal, the same problems exist with the HFC system described above.

By the way, the relationship between the optical input and the optical output of a semiconductor laser that converts an electrical signal into an optical signal is not a perfect straight line, and particularly, third-order distortion is large and transmission characteristics are deteriorated. Therefore, although the degree of intensity modulation cannot be increased, there is a problem that if the intensity modulation is small, a large signal-to-noise ratio cannot be obtained when optical transmission is reproduced as an electric signal. Also, the transmission characteristics are greatly affected by the reflected return light from the connector portion of the optical fiber, and a mechanism is required to prevent the reflected return light from returning to the semiconductor laser chip. . There is a problem in installing such a complicated electric / optical conversion unit in a fiber node, and it is not put into practical use, but remains in the research stage.

As a method for performing high-speed transmission using an existing metal line, a method called carrierless amplitude phase (CAP) has been proposed. In this method, the amplitude of two axes orthogonal to the modulated wave is multi-valued,
This is a method for increasing the transmission capacity in a narrow band, and a method for separating the frequency bands in the upstream and downstream directions. When a signal according to such a method is transmitted through an existing metal line, a sufficient broadband transmission is possible if the transmission distance is short, but the transmission capacity decreases as the transmission distance increases.

Therefore, as described above, an optical signal is transmitted to a fiber node in the middle, and the last 100 m is transmitted by CA.
A form in which transmission is performed by the P method is considered. In this case, there is no problem regarding the transmission between the center device and the fiber nodes, but it is necessary to mount the CAP modems in the fiber nodes as many as the number of user devices connected to the fiber nodes. There is a problem that it will be.

Incidentally, in order to reduce the scale of the center device, a so-called passive double-star configuration in which the center device and a plurality of fiber nodes are connected by an optical star coupler may be adopted. In this case, since the upstream signals output from the plurality of fiber nodes flow into one fiber finally connected to the center device, the upstream signals output from the respective fiber nodes collide with the star coupler. It is necessary to perform access control so that there is no That is, the center device determines the output timing of each fiber node so that the signal does not collide on the star coupler, and notifies it to each fiber node in the downstream signal. Then, each fiber node transmits an uplink signal at the notified timing.

For this reason, the transmission termination is performed once between the center device and the fiber node, and the transmission termination is performed again between the fiber node and the user device, so that the device configuration of the fiber node becomes large. There is a problem that.

[0015]

As described above, conventionally,
It is necessary to provide an electrical / optical converter with a complicated configuration,
Since it is necessary to mount the CAP modulator / demodulator by the number of connected user devices or to provide an access control unit, there is a problem that the device configuration of the fiber node becomes large.

The present invention has been made in view of such circumstances, and a purpose thereof is to provide a hybrid access system capable of realizing a fiber node with a simple configuration and a hybrid access system used in this hybrid access system. A center device, a fiber node, and a user device.

[0017]

In order to achieve the above object, according to a first aspect of the present invention, for example, a plurality of A / D units for digitizing downlink signals respectively supplied to a plurality of user apparatuses to a center apparatus. Time-division multiplexing means such as a time-division multiplexing unit for generating one downlink transmission signal by time-division multiplexing each downstream signal digitized by the digitalization means; An optical transmission unit such as an electric / optical conversion unit is provided for transmitting the downstream transmission signal generated by the time division multiplexing unit to an optical transmission line such as a downstream optical fiber after performing electrical / optical conversion.

Further, the fiber node receives a downstream transmission signal arriving via the optical transmission line, and performs optical / electrical conversion, for example, an optical receiving unit such as an optical / electrical conversion unit, and the optical receiving unit converts the electric signal into an optical signal. For example, a time division / frequency division conversion unit that converts the obtained downlink transmission signal from a signal obtained by time division multiplexing each digital down signal to a signal obtained by frequency division multiplexing each analog down signal. Time-division / frequency-division conversion means, and the downstream transmission signal after the multiplexing method is converted by the time-division / frequency-division conversion means to a non-optical transmission line such as a coaxial cable, a radio line, or a metal line. Non-optical transmission means, such as a filter or an amplifier, for transmitting data is provided.

Furthermore, a non-optical device such as a receiver for extracting a signal assigned to the user device in advance from the downlink transmission signal arriving via the non-optical transmission line to the user device and receiving the downlink signal addressed to the user device. A receiving means was provided.

[0020] By adopting such means, a wide-band and long-distance transmission can be performed between the center device and the fiber node by using an optical transmission line, and then, the communication between the fiber node and the user device is performed. Between them, a hybrid access system using an inexpensive non-optical transmission path is constructed. In the optical transmission path, a plurality of downlink signals are digitized, and then time-division multiplexed downlink transmission signals are converted into optical signals and transmitted. In the fiber node, the downlink transmission signal is converted back to an electric signal, and the multiplexing method is converted from time division multiplexing to frequency division multiplexing and output to each user apparatus.

Therefore, it is possible to transmit a binary signal through the optical transmission line, although the user apparatus is compatible with the frequency division multiplexing system. In order to achieve the above object, a second invention of the present application provides a user equipment which converts an uplink signal into a specific time region or a frequency band previously allocated to the user equipment, and then converts the uplink signal into, for example, a coaxial cable, a radio line, or the like. Alternatively, a non-optical transmission unit such as a wireless transmission unit for transmitting to a non-optical transmission line such as a metal line is provided.

A non-optical receiving means for receiving an uplink transmission signal arriving at the fiber node via the non-optical transmission line, for example, comprising a transmission / reception separating unit and a down-converter, and an uplink received by the non-optical receiving means. The transmission signal is converted from a signal obtained by frequency-division multiplexing each analog uplink signal to a signal obtained by time-division multiplexing each digital uplink signal. For example, a frequency separation unit, a plurality of A / D converters Frequency division / time division conversion unit comprising a frequency division / time division multiplexing unit, and electrical / optical conversion of an upstream transmission signal whose multiplexing scheme has been converted by the frequency division / time division conversion unit, for example, an upstream optical fiber or the like. And an optical transmission unit such as an electric / optical conversion unit for transmitting to the optical transmission line.

Further, the center device receives a transmission signal arriving via the optical transmission line, and performs optical / electrical conversion, for example, optical receiving means such as optical / electrical converting means, and an electric signal by the optical receiving means. A time-division separation unit such as a time-division separation unit that separates each uplink signal from the separated uplink transmission signal, and a plurality of D / A units that each convert each of the uplink signals separated by the time-division separation unit into an analog signal. Analog conversion means.

By adopting such means, a wide-band and long-distance transmission is made possible by using an optical transmission path between the center device and the fiber node, and then the communication between the fiber node and the user device is performed. Between them, a hybrid access system using an inexpensive non-optical transmission path is constructed. The upstream signals transmitted from the respective user devices with different time slots or different frequencies are once separated by fiber nodes, digitized, time-division multiplexed, and further converted to optical signals. And transmitted through the optical transmission path.

Therefore, it is possible to transmit a binary signal through the optical transmission line, though the user apparatus is compatible with the frequency division multiplexing system. In order to achieve the above object, a third invention of the present application is directed to a center device in which an upstream signal transmitted from each of a plurality of user devices connected to each of a plurality of fiber nodes is connected to its own device. The transmission timing for each of the plurality of user devices is determined so as not to collide in an optical transmission line such as an upstream optical fiber, and the access timing is notified to the plurality of user devices. Control means were provided.

[0026] Further, for example, the slave access control means for transmitting an upstream signal to a non-optical transmission line such as a coaxial cable, a radio line, or a metal line at a timing for the own device notified to the user device by the access control unit. Transmission timing control means.

Further, a combining means, such as an adder, for directly combining upstream signals transmitted from a plurality of user apparatuses connected to the fiber node with the fiber node, and a signal obtained by the combining means, An optical transmission unit such as an electric / optical conversion unit for transmitting the converted signal to an optical transmission path such as an optical fiber for upstream is provided.

By taking such means, a wide-band and long-distance transmission is made possible by using an optical transmission path between the center device and the fiber node, and the transmission between the fiber node and the user device is performed. Between them, a hybrid access system using an inexpensive non-optical transmission path is constructed. Then, by adjusting the transmission timing of the uplink signal from each user device, an uplink transmission signal of the time division multiplexing method is generated by a simple combination, but the transmission timing of the uplink signal from each user device is controlled by the center. This is performed by access control means provided in the device and transmission timing control means provided in the user device. Therefore, the fiber node only needs to perform a simple intermediary operation such as a simple combination.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a functional block diagram showing a main configuration of a hybrid access system according to the present embodiment.

This hybrid access system uses C
It is intended to be applied to an urban CATV system in which ATV is bidirectional. As shown in the figure, the hybrid access system according to the present embodiment connects the center device S1 and the fiber node N1 via the downstream optical fiber F1 and the upstream optical fiber F2, respectively. (Up to n) user devices U1 (U1-1 to U1-n) are connected via a coaxial cable C. That is, this hybrid access system is in the form of an HFC.

The center device S1 has the same number (n) of A / Ds as the number of connectable user devices U1 to the fiber node N1.
It has a unit 11 (11-1 to 11-n), a time division multiplexing unit 12, an electric / optical conversion unit 13, an optical / electric conversion unit 14, and a D / A unit 15.

The fiber node N1 is connected to the optical / electrical
1. TDM / FDM converter 22, filter 23, down converter 24, A / D unit 25, and electrical / optical converter 2.
6.

Each of the user devices U1 has a receiving unit 3
1 (31-1 to 31-n) and a transmission unit 32 (32-1 to 32-n). Next, the operation of the hybrid access system configured as described above will be described.

The center device S1 transmits analog video signals such as moving images, digital video signals, digital signals for telephone calls, digital data such as the Internet, and the like to the user device U1 as downlink signals.

In the case of CATV, since the system is designed based on the conventional analog video signal, 6
Let's consider MHz as a unit. Recently, 16QA
M, 64 QAM, or 256 QAM or other multi-level digital modulation allows a 32 MHz
Digital signals can be transmitted at a speed of about bps. In addition, the progress of video signal coding has been remarkable, and the high-efficiency coding of MPEG2 has led to the conventional TV NTSC analog video signal.
It is also possible to compress to a bit rate of about 6 Mbps. Therefore, by combining this high-efficiency coding with multi-level digital modulation, 4 to 4
It is possible to transmit digital video signals of about six channels. Also in the case of such a digital video, it is also considered as one group at 6 MHz.
Also, in the case of data signals such as the Internet, 6M
Hz is treated as one group.

Each of the A / D units 11 in the center device S1 corresponds to a service to be supplied to a plurality of user devices U1, and a digital signal for a telephone which requires bidirectionality in the service; For digital data on the Internet or the like, a downstream signal to be provided to a plurality of user devices U1 is provided. This downlink signal is 6
It is a signal in an analog state that fits in the MHz band. For example, a conventional NTSC analog video signal is equivalent to one channel, and a digital signal such as a digital video signal is multiplexed on several channels as necessary. And encoded. Note that the modulation method of the digital signal only needs to use a carrier having a sufficiently low frequency that can be converted from analog to digital by the A / D unit 11. For example, Q
AM modulation and the like. Therefore, in the A / D section 11, the input analog down signal is converted from analog to digital to be in a digital state.

As described above, the down signals for n channels, each of which is in the digital state in the A / D unit 11, are time-division multiplexed in the time division multiplexing unit 12. At this time, a transmission frame or the like is provided to multiplex the signals so that the multiplexed signals can be separated on the receiving side. Also, at this time, it is assumed that a device is devised so that the code “0” or “1” does not occur continuously so that the timing can be reproduced by optical reception. This contrivance includes scrambling to take an exclusive OR with a pseudo random signal, mBnB, CMI
Well-known techniques such as can be applied arbitrarily.

A signal obtained by the time division multiplexing in the time division multiplexing section 12 (hereinafter referred to as a downlink transmission signal) is
After being converted into an optical signal by the optical conversion unit 13, the optical signal is transmitted to the downstream optical fiber F1.

The downstream transmission signal transmitted to the downstream optical fiber F1 is transmitted via the downstream optical fiber F1.
Reach the fiber node N1. Then, the downstream transmission signal is input to the optical / electrical conversion unit 21 at the fiber node N1.

The downstream transmission signal is transmitted to the optical / electrical converter 2
After being converted into an electric signal in step 1, the signal is collectively converted into a frequency multiplexed signal by the TDM / FDM conversion unit 22. T
For the specific configuration of the DM / FDM conversion unit 22,
“Taio Kimio:“ TDM / FDM Transmultiplexer ”, Journal of the Institute of Electronics, Information and Communication Engineers, 64, 2, p.212.
(Showa 56) "and" Bellanger M. and Daguet J .: "T
DM-FDM Transmultiplexer; Digital polyphase
and FFT ”, IEEE Transaction on Communication,
COM-22, p. 1199 (1974) ", and a plurality of methods are known, and these can be used as appropriate.

FIG. 2 is a diagram showing the basic configuration shown in the former of the above two documents. In this figure,
3 shows a configuration for processing a signal in which four channels are multiplexed.

The TDM / FDM conversion section includes a channel separation section 221, spectrum inversion processing sections 222 and 223, and sampling rate conversion sections 224 (224-1 to 224-224) of the same number (here, four) as the number of multiplexed channels. 4), the same number (here, four) of digital filter units 225 (22
U1-1 to 225-4), digital adder 226, D / A unit 2
27 and a low-pass filter (LPF) 228.

In this TDM / FDM converter, first, an input TDM signal is time-division multiplexed and separated by a channel separator 221 to be separated into four channels. Only the signals of the even-numbered channels among the four separated channels are input to the spectrum inversion processing units 222 and 223, respectively, and the spectrum is inverted. The reason for this is that a signal having a spectrum falling within a predetermined band is extracted as a residual sideband signal by the digital filter 225, and the directions of the sidebands are all made to coincide with each other.

The signals of the even channels are input to the sampling rate converters 224-2 and 224-4 after the above-described spectrum inversion processing. When the signal of the odd channel is output from the channel separation unit 221, it is directly input to the sampling rate conversion units 224-1 and 224-3. Then, the signals of these four channels are sampled by the sampling rate converter 224-1.
At 224-4, sampling rate conversion is performed.

That is, first, according to the sampling theorem, if the sampling rate on the transmitting side is set to be twice the analog signal band, an analog signal can be reproduced, and is represented by 2 × f _B.
The sampling rate converters 224-1 to 224-4 convert the sampling rate into a sampling rate 2 × N × f _B which is N times the number of channels.

The signals whose sampling rates have been converted are then input to digital filter units 22U1-1 to 225-4, where the residual sideband signals are extracted in units of 6 MHz. Are added to each other.
Subsequently, the signals obtained by adding the respective signals by the digital adder 205 are collectively subjected to digital / analog conversion by the D / A unit 227, and then the low-pass filter 22
8 removes harmonic components.

As a result, the output of the low-pass filter 228 becomes an FDM signal in which four channels are frequency-division multiplexed. In order to arrange the frequency-multiplexed signal in a predetermined frequency band, mixing with a predetermined frequency may be performed.

In the above configuration, there is an upper limit to the number of channels for performing the batch conversion process due to the scale of the digital signal processing and the speed limit of the D / A unit 227. In this case, parallel processing may be performed after time-division channel separation, and the output of frequency up-conversion by frequency mixing may be multiplexed on the frequency axis in group units.

By the way, actually, the TDM /
The FDM conversion unit 22, a signal including a service that can be received respective user equipment U1-1~U1-n is, the downlink transmission signal is obtained by frequency division multiplexing as the frequency band f _D-1 ~f _Dm for the downlink. The downlink transmission signal whose frequency division multiplex has been converted in this manner is transmitted to the coaxial cable C via the filter 23. The filter 23 separates the downstream transmission signal and the upstream transmission signal flowing through the coaxial cable C. In the case of an urban CATV, the downstream and upstream bands of the coaxial cable C are, for example, 70 MHz to 750 MHz in the downstream and 10 MHz to 40 MHz in the upstream.

In the user devices U1-1 to U1-n, the receiving units 31-1 to 31
-n is the downstream frequency band fD _-1 through the coaxial cable C
_fDm is received, and a downlink signal transmitted from the center device S1 to the own device multiplexed in the two-way data service included in this frequency band is obtained along with the broadcast service.

On the other hand, in the user equipment U1-1 to U1-n, the transmitting unit 32-1
To 32-n are coaxial using the uplink frequency band f _U (having a bandwidth of, for example, 6 MHz) common to the user devices U1-1 to U1-n at the transmission timing allocated to the own device. The upstream signal is transmitted to the cable C. That is, in this embodiment, the upstream channel is one channel of the 6 MHz band,
This is used by the user devices U1-1 to U1-n in a time sharing manner.

The upstream signals output from the user devices U1-1 to U1-n in this manner are time-division multiplexed signals on the coaxial cable C (hereinafter, referred to as upstream transmission signals).
The upstream transmission signal is extracted by the filter 23 at the fiber node N1, and then down-converted by the down-converter 24 to a frequency band in which the A / D unit 26 can perform analog / digital conversion. At this time, it is also possible to adopt a direct conversion method that eliminates a carrier wave.

The down-converted upstream transmission signal is
The analog / digital conversion is performed by the Α / D unit 26, and further converted into an optical signal by the electric / optical conversion unit 26, and transmitted to the upstream optical fiber F2. At this time, as in the case of the downlink transmission signal, transmission frame formation, scrambling and mBn
Encoding such as B is performed as appropriate.

In the center device S1, when an upstream transmission signal arrives via the upstream optical fiber F2, the upstream transmission signal is converted into an electric signal by the optical / electrical converter 14.
Further, the upstream transmission signal after being converted into an electric signal is D
The digital / analog conversion is performed by the / A unit 15, and the upstream signal is reproduced. In this embodiment, the D / A unit 15
Is an QAM signal. This is because the input of the A / D unit 25 is a QAM signal in the fiber node N1, and a signal other than the QAM signal can be transmitted.

Normally, when exchanging data signals on the Internet or the like, WA signals are transmitted using an urban CATV.
N (wide area network). Between the center device S1 and the plurality of user devices U1, the user device U
Instead of securing one independent line, the form of shared media in which the line is shared by a plurality of users is used. In that case, it is necessary to perform access control between the center device S1 and the user device U1. The access control includes a polling control for sequentially granting the user device U1 a transmission permission from the center device S1 and a contention method for requesting the user device U1 to transmit to the center device S1. In the present embodiment, there is a delay time due to analog / digital conversion and vice versa, but the delay time is not so great as to greatly affect access control.

Thus, according to the present embodiment, the optical signals transmitted through the downstream optical fiber F1 and the upstream optical fiber F2 indicate the digitized downstream transmission signal and upstream transmission signal, all of which are binary. Signal. Therefore, the electrical / optical converters 13 and 26 and the optical / electrical converter 1
The non-linear distortion of 4, 21 is no problem at all, and the configuration can be simplified. Thereby, the scales of the center device S1 and the fiber node N1 are greatly reduced, and a hybrid access system using an optical fiber and a coaxial cable can be realized by the simple fiber node N1.

Although the TDM / FDM converter 22 is provided for performing binary transmission on the downstream optical fiber F1, the increase in the size of the fiber node N1 due to this is simplified by the electric / optical converter 26. Therefore, the size of the fiber node N1 is reduced as compared with the amount of reduction in size due to the implementation.

Conventionally, the frequency-division multiplexed signal is subjected to electrical / optical conversion as it is, so that the degree of modulation per channel is as low as several percent, and in order to secure a predetermined signal-to-noise ratio, the optical transmission line must be provided. Although the allowable loss could not be increased, in the present embodiment, since the signal of one channel is directly converted into an electric signal and an optical signal, the degree of modulation is increased.
A sufficient signal-to-noise ratio can be ensured.

It is to be noted that the downlink transmission signal has a 10 Gbit
/ S optical digital transmission, and using an A / D unit 11 of 12 Msamples / s and 8 bits / 1 sample allows transmission of NTSC video signals of 100 channels. If 64QAM high-efficiency modulation and MPEG2 high-efficiency coding are used together, video signals of 500 to 600 channels can be transmitted. Also, regarding the upstream transmission signal,
By transmitting a 100 Mbit / s digital signal, 6
A MHz band can be secured, a band of about 30 Mbit / s can be secured by using 64QAM high-efficiency modulation, transparency with a coaxial cable is good, and access control similar to that of a conventional HFC can be performed.

(Second Embodiment) FIG. 3 is a functional block diagram showing a main configuration of a hybrid access system according to the present embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

This hybrid access system is intended to be applied to a system in which the user is a wireless device, such as a PHS (Personal Handyphon System).

As shown in this figure, in the hybrid access system of this embodiment, the center device S2 and the fiber node N2 are connected via the downstream optical fiber F1 and the upstream optical fiber F2, respectively, and are connected to the fiber node N2. On the other hand, a plurality of (up to k) user devices U2
(U2-1 to U2-k) are connected via a wireless line.

The center device S2 includes an A / D unit 11 (11-1 to 11-1).
11-n), a time division multiplexing unit 12, an electric / optical conversion unit 13, an optical / optical
The same number (k) as the number of user devices U2 that can be connected to the electrical conversion unit 14, the time division separation unit 41, and the fiber node N2
D / A section 42 (42-1 to 42-k).

The fiber node N2 is connected to the optical / electrical
1, TDM / FDM converter 22, electric / optical converter 26,
Upconverter 51, transmission / reception separation unit 52, antenna 5
3. The same number (k) of second downconverters 56 (56-1 to 56-) as the number of connectable user devices U2 to the downconverter 54, the frequency separation unit 55, and the fiber node N2.
k), and also has k A / D units 57 (57-1 to 57-k) and a time division multiplexing unit 58.

The user apparatus U2 includes a radio receiving unit 61 (61-1 to 61-k) and a radio transmitting unit 62 (62-1 to 62), respectively.
-k). Next, the operation of the hybrid access system configured as described above will be described.

In the center device S2, each of the A / D units 11 has n radio channels (PHS) set on a radio line between the fiber node N2 and each user device U2.
Corresponds to each of the four frequencies and eight frequencies, and downlink signals (# 1 to #n) to be supplied to the user apparatus U2 using the corresponding radio channel are provided. This down signal is a CAP signal here. That is, for example, in the case of PHS, the frequency band of the radio line is the 1.9 GHz band, and QPSK modulation is adopted.
It is assumed that the P signal is given to each A / D unit 11 as a downlink signal. Therefore, in the A / D section 11, the input analog down signal is converted from analog to digital to be in a digital state.

As described above, the down signals for n channels, each of which is in the digital state in the A / D section 11, are time-division multiplexed in the time division multiplexing section 12. At this time, a transmission frame or the like is provided to multiplex the signals so that the multiplexed signals can be separated on the receiving side. Also, at this time, it is assumed that a device is devised so that the code “0” or “1” does not occur continuously so that the timing can be reproduced by optical reception. This contrivance includes scrambling to take an exclusive OR with a pseudo random signal, mBnB, CMI
Well-known techniques such as can be applied arbitrarily.

The downstream transmission signal obtained by the time division multiplexing in the time division multiplexing section 12 is converted into an optical signal in the electrical / optical conversion section 13 and transmitted to the downstream optical fiber F1. The downstream transmission signal transmitted to the downstream optical fiber F1 is transmitted via the downstream optical fiber F1 and reaches the fiber node N2. Then, fiber node N2
The downlink transmission signal is input to the optical / electrical converter 21 at.

The downstream transmission signal is transmitted to the optical / electrical
After being converted into an electric signal in step 1, the signal is collectively converted into a frequency multiplexed signal by the TDM / FDM conversion unit 22. The downlink transmission signal thus converted into a frequency multiplexed signal is
After being up-converted to a predetermined carrier frequency (for example, 1.9 GHz band in PHS) by the up-converter 51, the signal is guided to an antenna via a transmission / reception separation unit 52 and transmitted to a wireless line. In the case of PHS,
Since transmission and reception are switched in a time-division manner, the transmission / reception separation unit 52 is a switch.

In the user devices U2-1 to U2-k, the receiving units 61-1 to 61-1
-k is, and performs reception of the downlink frequency band for the radio channel corresponding to the own device and time slot (f _D-1 ~f _Dk) from among the signals arriving via the radio channel, thereby self apparatus The downlink signal transmitted from the center device S1 to the destination is obtained.

On the other hand, in the user devices U2-1 to U2-k, the transmitting unit 62-1
To 62-k transmit the uplink signal to the radio line using the uplink frequency band ( _{fU -1 to fUk} ) and the time slot of the radio channel allocated to the own device.

The uplink signals output from the user apparatuses U2-1 to U2-k in this manner are signals multiplexed by frequency division multiplexing and time slots on a radio line (hereinafter referred to as uplink transmission signals). become. The upstream transmission signal is received by the antenna 53 at the fiber node N2, and is provided to the down converter 54 via the transmission / reception separation unit 52.

Then, the uplink transmission signal is once dropped to the intermediate frequency band by down converter 54, and then frequency-separated by frequency separation section 55 for each radio channel, that is, for each uplink signal. Each of the frequency-separated upstream signals is provided to each of the second down converters 56-1 to 56-k to be a carrier signal having a sufficiently low carrier. Each of the upstream signals is subjected to analog / digital conversion by each of the A / D units 57-1 to 57-n.

Each uplink signal PCM-converted by A / D section 319 is time-division multiplexed by time-division multiplexing section 58. In this way, the uplink transmission signal, which has been a frequency division multiplex system, is converted into a time division multiplex system. At this time, as in the case of the downlink transmission signal, transmission frame formation, scrambling, and encoding such as mBnB are appropriately performed so that the timing can be reproduced on the receiving side.

Then, the upstream transmission signal in the time division multiplex system is converted into an optical signal by the electrical / optical converter 26 and transmitted to the upstream optical fiber F2. In the center device S2, when the upstream transmission signal arrives via the upstream optical fiber F2, the upstream transmission signal is transmitted to the optical / electrical
Is converted into an electric signal. Further, the upstream transmission signal after being converted into an electric signal is separated into each upstream signal by a time division demultiplexing unit 41, and each upstream signal obtained by this is converted into a D / D signal.
The digital signals are converted from digital to analog by the A units 42-1 to 42-n, and the analog upstream signal is reproduced. In this embodiment, the upstream signal reproduced by the D / A unit 15 is a carrier signal having a sufficiently low frequency.

Thus, according to the present embodiment, the optical signals transmitted through the downstream optical fiber F1 and the upstream optical fiber F2 indicate the digitized downstream transmission signal and upstream transmission signal, and are all binary signals. Signal. Therefore, the electrical / optical converters 13 and 26 and the optical / electrical converter 1
The non-linear distortion of 4, 21 is no problem at all, and the configuration can be simplified. As a result, the scale of the fiber node N2 is greatly reduced, and a hybrid access system of an optical fiber and a wireless line can be realized by the fiber node N2 having a simple configuration.

In order to perform binary transmission on each of the downstream optical fiber F1 and the upstream optical fiber F2, TD
M / FDM conversion unit 22, frequency separation unit 55, A / D unit 57
-1 to 57-n and the time-division multiplexing unit 58 are provided, but the amount of increase in the scale of the fiber node N2 due to this is reduced by the simplification of the optical / electrical conversion unit 21 and the electric / optical conversion unit 26. And as a result the fiber node N
The size of 2 is reduced. Especially TDM / FDM converter 2
2 is of the above-described batch conversion method, the size of the TDM / FDM conversion unit 22 can be smaller, and the amount of reduction in the scale of the fiber node N2 can be increased.

In the prior art, the frequency-division multiplexed signal is directly subjected to electrical / optical conversion. Therefore, the modulation factor per channel is as low as several percent, and in order to secure a predetermined signal-to-noise ratio, it is necessary to use an optical transmission line. Although the allowable loss could not be increased, in the present embodiment, since the signal of one channel is directly converted into an electric signal and an optical signal, the degree of modulation is increased.
A sufficient signal-to-noise ratio can be ensured.

(Third Embodiment) FIG. 4 is a functional block diagram showing a main configuration of a hybrid access system according to the present embodiment. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

This hybrid access system uses an optical fiber and a metal line, adopts a passive double-star configuration in the transmission line by the optical fiber, and further transfers the ATM (Asynchronous Transfer Mode) cell to the system. It is intended for application.

As shown in this figure, in the hybrid access system of this embodiment, the center device S3 and a plurality (maximum m) of fiber nodes N3 (N3-1 to N3-m) are connected via the optical fiber network NW. And a plurality of (up to a maximum of n) user apparatuses U3 (U3-1 to U3-n) are connected to the metal lines M (M-1 to M-) for each fiber node N3.
n).

The center device S3 includes an access control unit 71,
It has an electrical / optical converter 13 and an optical / electrical converter 14. The optical fiber network NW is connected to the center device S3.
And the downstream optical fibers F4 (F4-1 to F4-m) connected to the fiber nodes N3-1 to N3-m, respectively, connected by the optical star coupler SC1. The upstream optical fiber F5 connected to the center device S3 and the upstream optical fiber F6 (F6-1 to F6-m) connected to each of the fiber nodes N3-1 to N3-m.
Are connected by an optical star coupler SC2 to form a passive double star configuration.

The fiber node N3 is connected to the optical / electrical
1, an electrical / optical converter 26, a selector 81, an address checker 82, and an adder 83. In addition, the user devices U3 each have a dependent access control unit 91 (91-1 to 91-
n).

Next, the operation of the hybrid access system configured as described above will be described. First, in the center device S3, an exchange is performed based on the ATM address in an ATM exchange unit (not shown), and a plurality of signal lines between the ATM exchange unit and the access control unit 71 correspond to the user device U3 serving as a destination. Is output, the ATM cell
Each is input to the access control unit 71 as a downlink signal.

Each downlink signal is sent to the access control unit 71 by A
Time division multiplexing is performed in units of TM cells. At this time, since the speed after multiplexing is limited, excess cells are discarded according to the priority shown in the cell header. At this time, overhead required for transmission to the user apparatus U3 is added. A particularly important item for this overhead is the user equipment U
3 is the destination address. This destination address is assigned based on a conversion map with an ATM address provided in the access control unit 71. Furthermore, in order to facilitate timing reproduction on the receiving side, transmission processing such as BSI conversion and scrambling may be performed in the electrical / optical converter as necessary.

The signal obtained by the access control unit 71 (hereinafter, referred to as a downlink transmission signal) is converted into an optical signal by the electrical / optical conversion unit 13 and transmitted to the downstream optical fiber F3. . The downstream transmission signal transmitted to the downstream optical fiber F3 flows through the downstream optical fibers F4-1 to F4-n via the optical star coupler SC1, and is transmitted to the fiber nodes N3-1 to F4-n. Reach each of N3-m.

When the downstream transmission signal arrives at the fiber node N3 via the downstream optical fiber F4, the downstream transmission signal is input to the optical / electrical converter 21 and converted into an electric signal.

By the way, the downlink transmission signals arriving at each fiber node N3 include not only those addressed to the user equipment U3 connected to the fiber node N3 but also those transmitted to the user equipment U3 connected to the other fiber node N3. Includes those addressed. Therefore, the downstream transmission signal after being converted into an electric signal by the optical / electrical conversion unit 21 is provided to the selector 81 and the address confirmation unit 82, respectively, and the user terminal U3 connected to the own device is connected by the address confirmation unit 82. The destination ATM cell is confirmed, and only the pertinent ATM cell is output by the selector 81 to the metal line M to which the destination user device U3 is connected.

Here, the signal output to the metal line M has the same transmission rate as that at the time of transmission from the center device S3, and the ATM cells are output in a burst.
At this time, one user device U3 is transmitted from the fiber node N3.
The average transmission speed is the speed divided by the number of metal lines M converged to one fiber node N3. Therefore, even if the transmission speed of the signal passing through the metal line M is reduced, no serious problem occurs. Thus, the selector 81 can also perform speed conversion. In this case, the maximum transmission rate that the user device U3 can receive will be reduced. Further, a specific modulation for transmitting a metal line may be performed.

Further, it is also possible to eliminate the address confirmation unit 82 in the fiber node N3 and transmit the same signal from the center apparatus S3 to all the user apparatuses U3 without confirming the address. In this case, it is important that the center device S3 sends an encryption key code for confidential communication together with the destination address, and that the user device U3 cannot access signals other than the signal addressed to the user device U3.

In the user apparatus U 3, when an uplink signal addressed to itself arrives via the metal line M, this is fetched via the subordinate access control section 91. At this time, the dependent access control unit 91 extracts control information for access control, and performs access control based on the control information, which will be described later.

On the other hand, an upstream signal (ATM cell) generated in the user apparatus U3 is once taken into the subordinate access control section 91 provided in the user apparatus U3, and then transmitted to the subsequent addition section 83 and the optical fiber network. Is output to the metal line M at a predetermined timing determined to collide with an uplink signal transmitted from another user apparatus U3.

The upstream signal output from the user equipment U3 in this way is transmitted to the fiber node N via the metal line M.
When the number reaches 3, the upstream signal is input to the adder 83. Uplink signals respectively output from the other user apparatuses U3 are also input in parallel to the adding section 83, and the uplink signals respectively output from the user apparatuses U3 are added. At this time, since the uplink signals output from the respective user devices U3 are controlled at timings at which they do not collide with each other as described above, the signal obtained by the adder 83 is the uplink signal output from the respective user devices U3. The signal is a time-division multiplexed signal. The signal output from the adder 83 is converted into an optical signal by the electrical / optical converter 26, and then sent out to the upstream optical fiber F6.

The signals output from the respective fiber nodes N3 in this manner are all output from the optical star coupler S.
It flows into the upstream optical fiber F5 via C2. At this time, the signals output from the respective fiber nodes N3 are combined, but also the signals output from the respective fiber nodes N3 are controlled so as not to collide with each other. Thus, a signal obtained by time-division multiplexing of the signals respectively output from is obtained. The signal flowing from the optical star coupler SC2 to the upstream optical fiber F5 is a signal obtained by time-division multiplexing upstream signals from all the user devices U3 connected to the respective fiber nodes N3-1 to N3-m, This is an uplink transmission signal.

This upstream transmission signal is transmitted to the upstream optical fiber F5.
In the center device, the upstream transmission signal is input to the optical / electrical conversion unit 14, where it is converted into an electric signal.

The upstream transmission signal after being converted to an electric signal by the optical / electrical conversion unit 14 is supplied to the access control unit 7.
1 and is separated into individual uplink signals for each user apparatus U3 as a transmission source, and supplied to the ATM switching unit in parallel.

The above is the description of the center device S3 and each user device U.
3 shows a flow of transmission and reception of a signal with respect to the third embodiment. Subsequently, access control by the access control unit 71 of the center device S3 and the dependent access control unit 91 of the user device U3 will be described in detail.

First, in the optical fiber network NW, the upstream transmission signal and the downstream transmission signal have transmission frames as shown in FIG. That is, this transmission frame is formed of a multi-frame, and one main frame is formed by connecting the same number of sub-frames as the maximum number of user devices U3 that can be connected to the optical fiber network NW via the fiber node N3. ing.

In each subframe, a number of time slots for inserting cells (hereinafter, referred to as HAN (hybrid access network) cells) each having an overhead (OH) added to an ATM cell are set, and a delay is added at the end. A time measurement area is set. In the overhead transmission signal, a destination address, an encryption key code for confidential communication, or an ID indicating an information cell or a control cell is inserted into the overhead. In the uplink transmission signal, a guard time for setting an interval between cells, a preamble and a framing word for enabling burst-like reception, an ID indicating a cell type, a source address, and the like are inserted. In the delay time measurement area, more than the maximum time required for a signal to reciprocate between the center device S3 and the user device U3 is secured. That is, the length of the delay time measurement area is determined by the center device S
The distance can be determined based on an allowable value of the distance from the user device U3 to the user apparatus U3. For example, if the allowable value is about 10 km, the length of the delay time measurement area is about 100 microseconds.

Now, the user equipment U3 transmits HAN cells at the timing of the time slot allocated to itself in each subframe. However, the user equipment U3 transmits the HAN cell from each user equipment U3 to the optical star coupler SC2. The distance varies for each user device U3, and the time required for the HAN cell transmitted from each user device U3 to reach the optical star coupler SC2 also differs. Therefore, if each user apparatus U3 sends out a HAN cell at the timing shown in FIG. 5, there is a possibility that a collision of the HAN cell occurs in the optical star coupler SC2 due to the difference in the transmission time.

Therefore, the following access control is performed using the delay time measurement area provided in the subframe, and
The timing of each upstream signal in the optical star coupler SC2 is set to the timing shown in FIG. Note that the delay time measurement area in one subframe is used for access control for one user device U3, and the delay time measurement area of each subframe in one mainframe is used. Access control for all the user devices U3 is sequentially performed.

First, the access control section 71 of the center device S3 starts the start of the delay time measurement area (the left end in FIG. 6).
, Transmission of a predetermined delay time measurement cell (hereinafter, referred to as a DM cell) is started (time T1 in FIG. 6). At the same time, the access control unit 71 presets the time of the delay time measurement area to the built-in subtraction counter, and starts the down-counting operation.

Here, at the start of the connection, the access control unit 71 of the center device S3 sends the ATM address and the HAN
If a conversion map with the destination address of the cell has not been created, the destination address of the overhead of the DM cell is a universal address indicating that any user equipment U3 can respond.

The DM cells transmitted from the center device S3 have different delays D for each user device U3.
A, and reaches each user device U3 (T2 in FIG. 6).
Time). When the DM cell arrives, the subordinate access control unit 91 of each user apparatus U3 generates a random number after confirming that the destination address is a universal address. Is secured. Then, the DM response cell is transmitted to the metal line M at the same time as the overhead of the DM cell is terminated only by the subordinate access control unit 91 having the transmission right (at time T3 in FIG. 6).

The DM response cell transmitted from the user device U3 reaches the center device S3 after receiving a certain delay DB (at time T4 in FIG. 6). When the DM response cell arrives, the access control unit 71 in the center device S3
At the end of the DM response cell (at time T5 in FIG. 6), the subtraction counter is stopped, and the value of the subtraction counter at this time is determined as a delay instruction value for the user apparatus U3 that has transmitted the DM response cell.

At this time, when the DM response cell is received, the access control unit 71 of the center device S3 transmits the DM response cell.
The address of the user device U3 indicated in the cell overhead is associated with the ATM address. By writing this in the conversion table between the ATM address and the address of the HAN cell, the next polling is performed. By using this conversion table, it is possible to specify and poll the user device U3.

The above processing is sequentially performed in the order of securing the transmission right for all the user devices U3 in subframe units. In order to speed up this convergence, the parameter of the random number is assigned to the transmission right. A method of sequentially subtracting when already secured is desirable.

In some cases, a plurality of user apparatuses U3 may simultaneously secure the transmission right. In this case, signals collide in the delay time measurement area. At that time, the same operation is repeated.

As described above, the method using contention has an advantage that the user apparatus U3 has an upper limit number, but can be freely registered in the network. However, in order to prevent a collision from occurring, a conversion table that associates ATM addresses with HAN cell addresses may be created in advance in the access control unit 71 of the center device S3 by a network administrator.

Now, in each subframe of the next mainframe cycle, the access control unit 71 of the center device S3
Then, the DM cell in which the destination address specifying the user apparatus U3 is indicated and the delay instruction value determined for the user apparatus U3 is written is transmitted to the downstream optical fiber F3 (at time T11 in FIG. 7).

The DM cell sent from the center device S3 also receives the delay DA and reaches the user device U3 (at time T12 in FIG. 7). In the subordinate access control unit 91 of the user apparatus U3, the own apparatus sets D in the destination address.
When an M cell is received, a DM response cell is transmitted at a timing corresponding to the reception timing of the DM cell as in the case of the previous mainframe. Here, the delay instruction value written in the DM cell is read. After waiting for the time indicated by the delay indication value (time T13 in FIG. 7) from the end of the overhead of the DM cell (time T13 in FIG. 7), the transmission of the DM response cell is performed. . That is, the transmission timing of the DM response cell is delayed by the time indicated by the delay instruction value in the current mainframe as compared with the previous mainframe.

The DM response cell transmitted from the user apparatus U3 in this way arrives at the center apparatus S3 after receiving the delay DB (at time T15 in FIG. 7). Thus, when reaching the center device S3, the DM response cell is located at the trailing edge of the delay time measurement area (the right end in FIG. 5).

Thereafter, this control is repeated in the main frame cycle. At this time, the delay instruction value indicated from the center device S3 to the user device U3 is only an error value.
Therefore, the delay instruction value is adjusted so that the arrival timing of the DM response cell to the center device S3 becomes the state shown in FIG.

The above is the access control. By the access control, each user device U3 adjusts the transmission timing of the HAN cell over the time indicated by the delay instruction value determined for each user device U3. ,
HAN cell collision does not occur on the upstream optical fiber F5.

In the actual transmission of the HAN cell, the access control unit 71 of the center device S3 transmits
The transmittable cell number for the uplink signal is inserted into the M cell, and a transmission instruction is given to each user apparatus U3. On the other hand, the user device U3 inserts a transmission request into the DM response cell and notifies the center device S3. The transmission request may be, for example, the number of queues in the transmission buffer of the user device U3 or the priority.

Thus, according to the present embodiment, the optical fiber network NW of the passive double star configuration is adopted so that the center device S3 can be reduced in size and accommodate a large number of user devices U3. Since the access control for avoiding the collision is performed between the center device S3 and each user device U3, it is not necessary to perform the transmission termination in the fiber node N3. Therefore, the scale of the fiber node N3 is greatly reduced, and a hybrid access system of the optical fiber network NW having the passive double star configuration and the metal line M can be realized by the fiber node N3 having a simple configuration.

The present invention is not limited to the above embodiments. For example, in each of the above embodiments, separate optical fibers are provided for downstream and upstream. However, a wavelength multiplexing bidirectional communication system for transmitting the same fiber with different optical wavelengths for downstream and upstream. Can also be used.

In the first embodiment, the fiber node N1 and the user equipment U1 are connected by the coaxial cable C. However, another non-optical transmission line such as a radio line or a metal line is used. You can also.

In the second embodiment, the fiber node N2 and the user equipment U2 are connected via a wireless line. However, another non-optical transmission line such as a coaxial cable or a metal line is used. You can also

In the second embodiment, transmission of a carrierless amplitude and phase modulation (CAP) signal is basically performed. However, a signal downconverted to an intermediate frequency band can be used depending on the A / D conversion capability.

In the second embodiment, the carrier component is removed and converted into a CAP signal. However, as described above, there is a carrier having a low intermediate frequency depending on the performance of the A / D unit. Is also good.

The processing of the upstream signal at the fiber node N2 in the second embodiment is not limited to the above. For example, by mixing the signal from the transmission / reception separation unit 52 directly with a local oscillation frequency having a carrier frequency and then passing through a low-pass filter, it is possible to perform carrierless and frequency separation at the same time. .

In the third embodiment, the fiber node N3 and the user equipment U3 are connected via the metal line M, but another non-optical transmission line such as a coaxial cable or a wireless line is used. You can also do so.

The structure of the transmission frame and the access control procedure in the third embodiment are not limited to those described above, and can be set arbitrarily. In addition, various modifications can be made without departing from the spirit of the present invention.

[0125]

According to the first aspect of the present invention, the center device includes:
Digitizing means for digitizing each of the downlink signals respectively supplied to a plurality of user apparatuses; and time-division multiplexing for generating one downlink transmission signal by time-division-multiplexing each of the downlink signals digitized by the digitizing means. And a light transmitting means for converting the downstream transmission signal generated by the time division multiplexing means into electric / optical conversion and transmitting the converted signal to an optical transmission line.

The fiber node receives a downstream transmission signal arriving via the optical transmission line, and performs optical / electrical conversion. The downstream node receives the downstream transmission signal converted into an electrical signal by the optical receiving unit. Time-division / frequency-division conversion means for converting a digital signal obtained by time-division multiplexing each downlink signal to a signal obtained by frequency-division-multiplexing each analog downlink signal; Non-optical transmission means for transmitting the downstream transmission signal after the multiplexing system has been converted by the means to the non-optical transmission path.

Further, a non-optical receiving means for extracting a signal in a frequency band assigned to the user device from a downlink transmission signal arriving via the non-optical transmission line to the user device and receiving a downlink signal addressed to the user device. With.

Further, in the second invention of the present application, the user equipment is provided with a non-optical transmission means for converting an upstream signal into a frequency band assigned to the user equipment before transmitting the converted signal to a non-optical transmission path. Further, a non-optical receiving means for receiving an upstream transmission signal arriving via the non-optical transmission path to the fiber node, and converting the upstream transmission signals received by the non-optical receiving means into analog upstream signals, respectively. Frequency division / time division conversion means for converting each of the digitally multiplexed signals into a time division multiplexed signal from a signal obtained by division multiplexing, and a multiplexing system converted by the frequency division / time division conversion means. Optical transmission means for converting the upstream transmission signal into an optical signal and transmitting the converted signal to an optical transmission line.

Further, an optical receiving means for receiving the transmission signal arriving via the optical transmission line at the center device and performing optical / electrical conversion, and converting each of the downstream transmission signals converted into an electric signal by the optical receiving means from each downstream transmission signal. The signal processing apparatus includes time-division separating means for separating signals, and analog converting means for converting the respective downstream signals separated by the time-division separating means into analog signals.

Further, in the third invention of the present application, an upstream signal transmitted from each of a plurality of user devices connected to each of a plurality of fiber nodes is transmitted to an optical transmission line connected to its own device. An access control unit is provided for determining transmission timings for each of the plurality of user devices so as not to cause a collision, and notifying the plurality of user devices of the transmission timing.

Further, the user apparatus is provided with transmission timing control means for transmitting an uplink signal to the non-optical transmission line at the timing for the own apparatus notified by the access control means. Further, combining means for directly combining upstream signals transmitted from a plurality of user equipments connected to the own apparatus to the fiber node, and converting the signal obtained by the combining means into an optical / optical signal and transmitting the converted signal to an optical transmission line And an optical transmitting means for transmitting.

Thus, it is possible to provide a hybrid access system that can realize a fiber node with a simple configuration, and a center device, a fiber node, and a user device used in the hybrid access system.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a main configuration of a hybrid access system according to a first embodiment.

FIG. 2 is a functional block diagram showing a basic configuration of a TDM / FDM conversion unit 22.

FIG. 3 is a functional block diagram showing a main configuration of a hybrid access system according to a second embodiment.

FIG. 4 is a functional block diagram showing a main part configuration of a hybrid access system according to a third embodiment.

FIG. 5 is a diagram schematically showing a transmission frame configuration of an upstream transmission signal and a downstream transmission signal in the optical fiber network NW in FIG. 4;

FIG. 6 is an exemplary view showing a procedure of access control in the hybrid access system shown in FIG. 4;

FIG. 7 is a view showing a procedure of access control in the hybrid access system shown in FIG. 4;

[Explanation of Symbols] S1, S2, S3: Center device N1, n2, n3: Fiber nodes F1, F3, F4 (F4-1 to F4-m): Downlink optical fibers F2, F5, F6 (F6-1 to F6) F6-m) ... Upstream optical fibers U1 (U1-1 to U1-n), U2 (U2-1 to U2-k), U3 (U3-1
~ U3-n) ... user equipment C ... coaxial cable NW ... optical fiber network SC1, SC2 ... optical star coupler M (M-1 to Mn) ... metal line 11 (11-1 to 11-n or 11-1 to 11) -k) A / D section 12 Time division multiplex section 13 Electric / optical conversion section 14 Optical / electric conversion section 15 D / A section 21 Optical / electric conversion section 22 TDM / FDM conversion section 221 Channel separators 222, 223: spectrum inversion processor 224 (224-1 to 224-4) sampling rate converter 225 (22U1-1 to 225-4) digital filter 226: digital adder 227: D / A section 228 low-pass filter (LPF) 23 filter 24 down converter 25 A / D section 26 electric / optical conversion section 31 (31-1 to 31-n) reception section 32 (32-1 to 32) 32-n) Transmitting unit 41 Time-division separating unit 42 (42-1 to 42-k) D / A unit DESCRIPTION OF SYMBOLS 1 ... Up converter 52 ... Transmission / reception separation part 53 ... Antenna 54 ... Down converter 55 ... Frequency separation part 56 (56-1 to 56-k) ... Second down converter 57 (57-1 to 57-k) ... A / D unit 58: time-division multiplexing unit 61 (61-1 to 61-k) wireless receiving unit 62 (62-1 to 62-k) wireless transmitting unit 71 access control unit 81 selector 82 address confirmation unit 83 ... Addition unit 91 (91-1 to 91-n) ... Dependent access control unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H04L 12/44 H04L 11/20 D // H04L 12/28

Claims (14)

[Claims] 1. A center device, a fiber node connected to the center device via an optical transmission line, and a fiber node connected to the fiber node via a non-optical transmission line using a predetermined transmission medium other than light. One of a signal transmitted in one direction or two directions between the center device and the user device via the fiber node, and a transmission signal in one of a downlink direction and an uplink direction. Or in a hybrid access system in which transmission signals in both the down direction and the up direction are analog signals, the transmitted analog signal is a time-division multiplexed digital signal between the center device and the fiber node. Transmitted, between the fiber node and the user equipment, is transmitted as a frequency-divided analog signal Hybrid access system. 2. A center device, one fiber node connected to the center device via an optical transmission line, and a fiber node connected to the fiber node via a non-optical transmission line using a predetermined transmission medium other than light. One of a signal transmitted in one direction or two directions between the center device and the user device via the fiber node, and a transmission signal in one of a downlink direction and an uplink direction. Or in a center device used in a hybrid access system in which transmission signals in both the down direction and the up direction are analog signals, wherein the analog signals transmitted or received between the fiber nodes are time-division multiplexed digital signals. A center device used in a hybrid system, wherein the center device is transmitted or received by a personal computer. 3. The center unit digitizes down signals respectively supplied to the plurality of user devices, and time-division multiplexes the down signals digitized by the digitizing unit. Time division multiplexing means for generating one downlink transmission signal, and optical transmission means for performing electrical / optical conversion of the downlink transmission signal generated by the time division multiplexing means and transmitting the signal to the optical transmission path. 3. The apparatus according to claim 2, wherein
The center device as described. 4. The center device receives a transmission signal arriving via the optical transmission line, and
Optical receiving means for electrical conversion; time-division separating means for separating each uplink signal from the upstream transmission signal converted into an electrical signal by the optical receiving means; and each of the upstream signals separated by this time-division separating means is converted into an analog signal. 3. The center device according to claim 2, further comprising at least an analog converting means. 5. A center device, one fiber node connected to the center device via an optical transmission line, and a fiber node connected to the fiber node via a non-optical transmission line using a predetermined transmission medium other than light. One of a signal transmitted in one direction or two directions between the center device and the user device via the fiber node, and a transmission signal in one of a downlink direction and an uplink direction. Or, in a fiber node used in a hybrid access system in which transmission signals in both the down direction and the up direction are analog signals, the analog signal is transmitted as a frequency division multiplexed analog signal with the user equipment. A fiber node used in a hybrid access system, characterized in that: 6. The fiber node receives a downlink transmission signal arriving via the optical transmission line,
An optical receiving unit for performing optical / electrical conversion, and a downstream transmission signal converted into an electric signal by the optical receiving unit is converted from a signal obtained by time-division multiplexing each digital downstream signal to each analog downstream signal. Time division / frequency division conversion means for converting into a signal obtained by frequency division multiplexing, and a downstream transmission signal after the multiplexing system has been converted by the time division / frequency division conversion means, is transmitted to the non-optical transmission path. The fiber node according to claim 5, further comprising at least a non-optical transmission unit. 7. The non-optical receiving means for receiving an upstream transmission signal arriving via the non-optical transmission path, and the upstream transmission signal received by the non-optical receiving means are analog. Frequency division / time division conversion means for converting a signal obtained by frequency division multiplexing each uplink signal into a signal obtained by time division multiplexing each digital uplink signal; and multiplexing by this frequency division / time division conversion means. 6. The fiber node according to claim 5, further comprising: an optical transmission unit configured to perform an electrical / optical conversion on the upstream transmission signal whose format has been converted and transmit the converted signal to the optical transmission line. 8. The center device and the plurality of fiber nodes are connected by connecting an optical transmission line connected to a center device and optical transmission lines respectively connected to a plurality of fiber nodes by an optical star coupler. A plurality of user devices are connected to each of the plurality of fiber nodes via a predetermined non-optical transmission path using a predetermined transmission medium other than light for each of the plurality of fiber nodes. In the hybrid access system performing transmission / reception, the center device collides with an upstream signal transmitted from each of the plurality of user devices connected to each of the plurality of fiber nodes in an optical transmission path connected to the own device. The transmission timing for each of the plurality of user devices is determined so that the An access control unit for notifying each of the devices, the plurality of user devices each include a transmission timing control unit for transmitting an uplink signal to the non-optical transmission line at a timing for the own device notified by the access control unit. The fiber node further comprises: combining means for directly combining upstream signals transmitted from a plurality of user equipment connected to the fiber node; and electrical / optical conversion of a signal obtained by the combining means. A hybrid transmission system comprising: an optical transmission unit that transmits the signal to the optical transmission line. 9. The center device and the plurality of fiber nodes are connected by connecting an optical transmission line connected to a center device and an optical transmission line respectively connected to a plurality of fiber nodes by an optical star coupler. A plurality of user devices are connected to each of the plurality of fiber nodes via a predetermined non-optical transmission path using a predetermined transmission medium other than light for each of the plurality of fiber nodes. In a center device used in a hybrid access system that performs transmission and reception of signals, an uplink signal transmitted from each of a plurality of user devices connected to each of the plurality of fiber nodes collides on an optical transmission line connected to the own device. The transmission timing for each of the plurality of user devices is determined so as not to Center apparatus characterized by comprising an access control means for notifying each of the over laser device. 10. The center device and the plurality of fiber nodes are connected by connecting an optical transmission line connected to a center device and optical transmission lines respectively connected to a plurality of fiber nodes by an optical star coupler. A plurality of user devices are connected to each of the plurality of fiber nodes via a predetermined non-optical transmission path using a predetermined transmission medium other than light for each of the plurality of fiber nodes. A user apparatus used in a hybrid access system that performs transmission and reception of transmission / reception information, comprising transmission timing control means for transmitting an uplink signal to the non-optical transmission path at a timing for the own apparatus notified by the access control means. User equipment. 11. The center device and the plurality of fiber nodes are connected by connecting an optical transmission line connected to a center device and optical transmission lines respectively connected to a plurality of fiber nodes by an optical star coupler. A plurality of user devices are connected to each of the plurality of fiber nodes via a predetermined non-optical transmission path using a predetermined transmission medium other than light for each of the plurality of fiber nodes. In a fiber node used in a hybrid access system for transmitting and receiving a signal, a combining means for directly combining uplink signals transmitted from a plurality of user devices connected to the own device, and a signal obtained by the combining means A fiber node, comprising: an optical transmission unit that performs optical conversion and transmits the optical transmission line to the optical transmission line. 12. The hybrid access system according to claim 1, wherein the non-optical transmission path is a coaxial cable. 13. The hybrid access system according to claim 1, wherein the non-optical transmission path is a wireless transmission path. 14. The hybrid access system according to claim 1, wherein the non-optical transmission path is a metal line.