Communication system using time division multiple access system

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a communication system using a time division multiplexing access system, and more particularly to a communication system in which a plurality of signals having different signal formats such as a transfer mode and a format are integrated and accommodated in an uplink.

【0002】

[Conventional technology]

A typical communication system in which a plurality of subscriber terminals share a communication medium and are connected to one terminal station device, and access control of an uplink from the subscriber terminal to the terminal station device is performed by a time division multiplexing access method. For example, there is ATM-PON (Asyncronous Transfer Mode Passive Optical Network).

【0003】

This is also called ATM-PDS (ATM-Passive Double Star). For an overview, for example, NTT R & D Vol.14 No.12, published in 1995, pp. 1157 to 1162, "High Speed". It is described in "Optical (ATM-PDS) Access System".

【0004】

Regarding the signal format, especially the frame structure of the signal, see "DRAFT E OF G.983 (EX G.PONB) AS A RESULT OF THE INTERIM MEETING IN AUGUST 1997 AND MINOR EDITIORIAL CHANGES" published by ITU-T. It is described in detail on pages 29 and 30.

【0005】

ATM-PON is a broadband access system for multimedia, and enables ATM communication with a code speed of 156 Mbps for uplink and downlink. In ATM-PON, terminal equipment and multiple subscriber terminals are connected using a passive optical fiber network, and in order to separate the downlink and uplink, wavelength division that allocates signal light of different wavelengths to both lines. The multiplex method is used.

【0006】

The terminal device and the subscriber terminal logically perform one-to-one communication, but when multiple subscriber terminals transmit at the same time on the uplink, an uplink signal collision occurs at a branch portion of the passive optical fiber network. .. In order to avoid this, the transmission timing of each subscriber terminal is controlled by the time division multiplex access method.

【0007】

The signal format adopted by ATM-PON is based on ATM cells. That is, an ATM cell-based flow in which ATM cells are connected is used for the downlink, and a burst signal having a configuration in which an overhead for synchronization is added to the ATM cells is used for the uplink. Therefore, the ATM-PON converts the signal format in order to match all the contained signals with the signal format of the ATM.

【0008】

Figure 5 shows a block diagram showing the configuration of ATM-PON. The terminal device 1 and the plurality of subscriber terminals 2 are connected by a passive optical fiber network 3. The terminal device 1 is connected to the STM network 23, the ATM network 24, and the Ethernet work 25. The signal from the ATM network 24 is input to the ATM switch 131, but the signals from the STM network 23 and the Ethernet work 25 are converted to ATM cells through the station-side CLAD132-a and the station-side ATM interface 133-a, respectively. It is input to the ATM exchange 131. The output of the ATM switch 131 is input to the station-side ATM-PON downlink signal generation circuit 134-a and output as an ATM-PON downlink signal 135.

【0009】

At the subscriber terminal 2, the ATM-PON downlink signal 135 is terminated by the subscriber side ATM-PON downlink signal termination circuit 134-b, and the ATM cell is taken out. The extracted ATM cell is separated by the multiplex separation circuit 136 into a cell containing an STM signal, a cell directly from the ATM network, and a cell containing an ether packet. The ATM cell containing the STM signal and the ether packet is input to the subscriber side CLAD132-b and the subscriber side ATM interface 133-b, respectively, and converted to the original signal format.

【0010】

On the other hand, even on the uplink, as shown in FIG. 5, the STM signal and the ether packet are transmitted after being once converted into an ATM cell. In the subscriber device 2, the STM signal and the ether packet are converted into an ATM cell by the CLAD and the ATM interface, respectively. Each of these ATM-converted signals is cell-multiplexed by the multiplex separation circuit 136 and input to the subscriber side ATM-PON uplink signal termination circuit 138-b. Here, the subscriber-side ATM-PON uplink signal termination circuit 138-b transmits the uplink signal according to the time division multiplex access control by the terminal device 1 in order to accommodate the uplink signal in the area allocated to the own device in the uplink. Send.

【0011】

[Problems to be Solved by the Invention]

However, in ATM-PON, it is necessary to convert all signals into ATM cells, and for example, CLAD is required even when accommodating telephone signals, which has been a factor of high cost. Also, when accommodating a low-speed constant bit rate signal such as a telephone signal, it is inefficient because most of the information area of the ATM cell is not used. Furthermore, when accommodating variable-length packets, segmentation is required to match the length of the ATM cell, and the interface for segmentation must be specified for each signal format, resulting in a new signal format. On the other hand, it was difficult to take immediate action.

【0012】

(Purpose of the Invention) An object of the present invention is to provide a communication system capable of easily accommodating signals of various formats in a media sharing type communication system using a time division multiplexing access system for an uplink. There is.

【0013】

[Means for solving problems]

The communication system according to the present invention is characterized in that a fixed-length frame is set for the uplink and the frame is further divided into a plurality of uplink subframes. The present invention is also characterized in that uplink signals of different signal formats are accommodated in separate uplink subframes. Therefore, according to the present invention, various uplink signals having different signal formats can be flexibly accommodated without affecting each other. The present invention is further characterized in that it is configured by a time slot having a unique length for each upstream subframe. By optimizing the length of this time slot according to the type of signal to be accommodated, it is possible to accommodate upstream signals of different signal formats without wasting bandwidth.

【0014】

In addition, the present invention is characterized in that the uplink signal termination device is switched for each uplink subframe. As a result, it is possible to separate and terminate the uplink signals of different formats accommodated in the uplink. Therefore, termination processing of uplink signals of different formats that have been integrated and transmitted can be easily performed.

【0015】

At least one of the uplink subframes according to the present invention is characterized in that a time slot at a fixed position in the uplink subframe is assigned to each subscriber terminal to accommodate a signal in the synchronous transfer mode. Further, the length of the time slot in this case is characterized by being the sum of the length of the signal emitted by the signal of the synchronous transfer mode to be accommodated during one frame interval and the length of the header for the uplink signal. As a result, the identifier of the subscriber terminal is not required, and the device can be simplified, the signal processing can be simplified, and the bandwidth can be used efficiently.

【0016】

At least one of the uplink subframes according to the invention is characterized by accommodating a fixed length cell in a time slot. Since a fixed-length cell is accommodated in a fixed-length time slot, it can be accommodated without wasting bandwidth.

【0017】

At least one of the uplink subframes according to the present invention is characterized in that a variable length packet is accommodated in a region in which time slots are concatenated. By this expropriation method, it is possible to provide an area corresponding to the length of a variable-length packet. Therefore, variable-length packets can be accommodated without wasting bandwidth.

【0018】

Further, in the present invention, a frame having a length equal to the frame of the uplink is set for the downlink, and the access control area in which the allocation of the time slot in the uplink subframe to the subscriber terminal is described is set for the uplink subframe. The access control area is set for each, and is characterized in that the access control area is inserted into a specific position in the downlink frame corresponding to the position in the uplink frame of the uplink subframe to be controlled by each. The phase of the frame in the downlink and the position of the access control area in the frame can give the phase of the frame in the uplink and the boundary position between the uplink subframes in the frame. Therefore, simple uplink control can be realized.

【0019】

In the present invention, the downlink frame divides the area other than the access control area into a plurality of downlink subframes, and inserts the downlink subframe boundary display area in which the boundary between the downlink subframes is described at a specific location of the downlink frame. It is characterized by. With this downlink subframe, independence between the downlink signals of each type can be realized even on the downlink. Therefore, each signal format is not easily affected by other signals on the downlink.

【0020】

The present invention is characterized in that the position of the access control area in the frame of the downlink is changed for each frame. By changing this position, the boundary between uplink subframes in the uplink can be freely set. Therefore, it is possible to flexibly cope with the increase / decrease of the signal amount between the uplink signals of each type.

【0021】

Further, in the present invention, an access control area in which a frame having a length equal to that of the uplink frame is set in the downlink and the allocation of the time slot in each uplink subframe to the subscriber terminal in the downlink frame is described. An uplink control area including an uplink subframe boundary position display area in which a boundary position between uplink subframes in the uplink is described is inserted at a specific location. In this upstream subframe boundary position display area, the boundary position between any upstream subframes within the frame can be entered. Therefore, simple uplink control can be realized.

【0022】

In the present invention, the downlink frame divides the area other than the uplink control area into a plurality of downlink subframes, and inserts the downlink subframe boundary display area in which the boundary between the downlink subframes is described at a specific location of the downlink frame. It is characterized by that. With this downlink subframe, independence between the downlink signals of each type can be realized even on the downlink. Therefore, each signal format is not easily affected by other signals on the downlink.

【0023】

Further, in one embodiment of the present invention, the code speed of the downlink is set to N times the code speed of the uplink (N is a positive integer), and the downlink is composed of N channels having the same code speed as the uplink. One of the N channels is provided with an uplink access control function. With this downlink configuration, the access control signal and the data signal can be completely separated in the downlink, and a signal used only for the downlink such as for broadcasting can be easily added.

【0024】

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the communication system using the time division multiplex access method of the present invention will be described in detail with reference to the drawings. An embodiment will be described with reference to an example in which the present invention is applied to an optical access system using a passive optical fiber network. FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

【0025】

The terminal device 1 and a plurality of subscriber terminals 2 are connected by a passive optical fiber network 3. In the passive optical fiber network 3, the downlink signal light 20 has a wavelength of 1.5 μm in order to separate the downlink from the terminal device 1 to the subscriber terminal 2 and the uplink from the subscriber terminal 2 to the terminal device 1. The signal light of the band is assigned, and the signal light of the wavelength 1.3 μm band is assigned to the uplink signal light 21. Both the downlink and uplink are 622 Mbps. The downlink signal light 20 and the uplink signal light 21 are separated by the station side WDM coupler 22-a inside the terminal station device 1.

【0026】

The terminal device 1 is connected to an STM network 23 that transmits STM signals such as telephones and N-ISDN signals, an ATM network 24 that transmits multimedia data signals, and an Ethernet work 25 that mainly transmits IP packets. The station-side downlink signal multiplexing circuit 8-a in the terminal device 1 accommodates the downlink STM signal 23-A, the downlink ATM signal 24-A, and the downlink ether packet signal 25-A, and transmits a downlink signal 4 of 622 Mbps. appear. Further, the downlink signal 4 also includes an uplink access control signal 26 output by the station side access control circuit 9. The downlink signal 4 is converted into downlink light 20 by the station-side optical signal transmission circuit 27-a and distributed to each subscriber terminal 2 through the passive optical fiber network 3.

【0027】

The subscriber terminal 2 separates the downlink signal light 20 and the uplink signal light 21 by the subscriber side WDM coupler 22-b, and converts the downlink signal light 20 into the downlink signal 4 by the subscriber side optical signal receiving circuit 28-b. To do. The downlink signal 4 is input to the subscriber side downlink signal termination circuit 8-b and separated into an access control signal 26, a downlink STM signal 23-A, a downlink ATM signal 24-A, and a downlink ether packet signal 25-A. .. The access control signal 26 is input to the subscriber side access control circuit 12 and terminated, and the internal information is sent as the uplink signal output timing control signal 19 to the subscriber side uplink signal multiplexing circuit 10-b, and the time in the frame is reached. It is used for timing control to transmit a burst signal according to the slot.

【0028】

On the other hand, regarding the uplink, the uplink STM signal 23-B is input to the first individual uplink signal generation circuit 14-1, and is assembled into the uplink signal cell by receiving header addition and the like. The upstream ATM signal 24-B and the upstream ether packet signal 25-B are temporarily stored in the first and second buffers 13-1 and 13-2 prepared for each signal. The first and second buffers 13-1 and 13-2 notify the subscriber side access control circuit 12 of the stored information as the first and second stored information signals 16-1 and 16-2, respectively. The subscriber-side access control circuit 12 that received the above outputs a band request signal 18 according to the amount of information accumulated and the priority. The band request signal 18 is accommodated in the bandwidth request area of the uplink and transmitted to the terminal device 1.

【0029】

The uplink ATM signal 24-B and the uplink ether packet signal 25-B are output from the first and second buffers 13-1 and 13-2, respectively, and are the second and third individual uplink signals, respectively. The generation circuits 14-2 and 14-3 receive header addition for each signal and are assembled into an uplink signal cell or an uplink signal packet. The outputs of the first to third individual uplink signal generation circuits 14-1 to 14-3 are input to the subscriber side uplink signal multiplexing circuit 10-b, and are accommodated in the uplink signal 5 together with the band request signal 18.

【0030】

The uplink signal 5 is converted into uplink signal light 21 by the subscriber side optical signal transmission circuit 27-b, output, and transmitted to the terminal device 1 through the passive optical fiber network 3. The terminal station device 1 separates the uplink signal light 21 from the downlink signal light 20 by the station side WDM coupler 22-a, inputs it to the station side optical signal receiving circuit 28-a, and converts it into the uplink signal 5. The uplink signal 5 is input to the station-side uplink signal termination circuit 10-a, and is separated into an uplink STM signal 23-B, an uplink ATM signal 24-B, and an uplink ether packet signal 25-B. At the same time, the band request signal 18 is also taken out and input to the station side access control circuit 9.

【0031】

The station-side access control circuit 9 processes the band request signal 18 issued from each subscriber device 2 and stores the band request signals 18 in the first and second buffers 13-1 and 13-2 for each subscriber device 2. get information. Since the first and second buffers 13-1 and 13-2 are operating independently, the station-side access control circuit 9 is independently connected to each subscriber device 2 for each signal in the uplink. Bands can be allocated, and this result is output as the access control signal 26 described above. Based on the access control signal 26, the subscriber terminal 2 accommodates the uplink ATM signal 24-B and the uplink ether packet signal 25-B by mapping them in the uplink signal frame, respectively.

【0032】

FIG. 2 shows the frame structure of the uplink signal 5 and the downlink signal 4 according to the embodiment of the present invention. The uplink signal 5 is composed of an uplink signal frame 30 having a length of 125 μs (9720 bytes), and the uplink signal frame 30 includes a first uplink subframe 31-1 and a second uplink subframe 31-2. It is composed of a third uplink subframe 31-3 and a fourth uplink subframe 31-4.

【0033】

The first uplink subframe 31-1 uses 1600 bytes out of 9720 bytes per frame, the second uplink subframe 31-2 uses 160 bytes, and the third uplink subframe 31-3 uses 3920 bytes. And the 4th uplink subframe 31-4 uses 4040 bytes. Each uplink subframe consists of time slots of different lengths for each uplink subframe, with the first uplink subframe 31-1 having a 50-byte first time slot 44-1 and a second uplink subframe. The uplink subframe 31-2 has a 5-byte second time slot 44-2, and the third uplink subframe 31-3 has a 56-byte third time slot 44-3, which has a fourth uplink sub. Frames 31-4 are each assigned a 40-byte fourth time slot 44-4.

【0034】

For each of the first to third time slots 44-1 to 44-3, an uplink signal cell having the same length as the time slot is accommodated. The first uplink signal cell 34-1 is accommodated in the first time slot 44-1, and the first uplink signal cell 34-1 is a 3-byte first uplink signal cell header 37-1. And a 47-byte first uplink cell payload 38-1. The first uplink signal cell payload 38-1 accommodates the 47-byte bandwidth request signal of each subscriber terminal 2.

【0035】

In the subscriber-side uplink signal multiplexing circuit 10-b in FIG. 1, the first uplink signal cell 34-1 generated by the subscriber-side access control circuit 12 is assigned to the own device in the first uplink subframe 31-1. It is accommodated in the first time slot 44-1. The position of the first time slot 44-1 assigned to each subscriber terminal 2 in the first uplink subframe 31-1 is fixed for each subscriber terminal 2.

【0036】

The second uplink signal cell 34-2 is accommodated in the second time slot 44-2, and the second uplink signal cell 34-2 is a 3-byte second uplink signal cell headers 37-2 and 2 It consists of a second uplink signal cell payload 38-2 of the byte. The second uplink signal cell payload 38-2 accommodates 1 byte of telephone STM signal and 1 byte of telephone control STM signal. In the subscriber-side uplink signal multiplexing circuit 10-b in FIG. 1, the second uplink signal cell 34-2 generated by the first individual uplink signal generation circuit 14-1 is placed in the second uplink subframe 31-2. It is accommodated in the second time slot 44-2 assigned to the own device. The position of the second time slot 44-2 assigned to each subscriber terminal 2 in the second uplink subframe 31-2 is fixed for each subscriber terminal 2.

【0037】

The third uplink signal cell 34-3 is accommodated in the third time slot 44-3, and the third uplink signal cell 34-3 is a 3-byte third uplink signal cell headers 37-3 and 53. It consists of a third uplink signal cell payload 38-3 of the byte. In the subscriber-side uplink signal multiplexing circuit 10-b in FIG. 1, the ATM cell is housed in the third uplink signal cell payload 38-3 by the second individual uplink signal generation circuit 14-2, and the second uplink signal cell payload 38-3 is accommodated therein. A signal cell header 37-2 is added, and the signal cell header 37-2 is added and accommodated in the third time slot 44-3 assigned to the own device in the third uplink subframe 31-3. The position of the third time slot 44-3 assigned to each subscriber terminal 2 is designated by the terminal device 1 as a result of requesting the bandwidth for each subscriber terminal 2.

【0038】

The fourth time slot 44-4 is a 40-byte time slot, and a plurality of consecutive time slots are concatenated to form a concatenated time slot 53, which accommodates an uplink signal packet 54 which is a variable length packet. The uplink packet 54 is composed of a 3-byte uplink packet header 55 and a variable-length uplink packet payload 56. In the subscriber-side uplink signal multiplexing circuit 10-b in FIG. 1, the ether packet signal is accommodated in the uplink packet payload 56 by the third individual uplink signal generation circuit 14-3, and the uplink packet header 55 is added thereto. It is accommodated in the connection time slot 53 assigned to the own device in the fourth uplink subframe 31-4. The position and length of the concatenated time slot 53 assigned to each subscriber terminal 2 is specified by the terminal device 1 as a result of requesting the bandwidth for each subscriber terminal 2.

【0039】

In this way, each uplink signal is accommodated in the time slot as an independent signal and burst-transmitted. Further, the first uplink signal cell header 37-1 and the second uplink signal cell header 37-2, the third uplink signal cell header 37-3, and the uplink packet header 55 have the same basic structure such as the preamble and are received. Bit synchronization for each cell or packet on the side can be performed with a common circuit.

【0040】

On the other hand, an access control method using a downlink will be described with reference to FIG. The downlink signal frame 49 has a length of 125 μs, which is equal to the uplink signal frame 30, and the first to fourth access control areas 43-1 to 43-4 are inserted therein. The 1st to 4th access control areas 43-1 to 43-4 are for performing access control in the 1st to 4th uplink subframes 44-1 to 44-4 in the uplink signal 5, respectively. A grant is transmitted to indicate which subscriber terminal's uplink signal is assigned to the time slot. The position in the downlink signal frame 49 at the beginning of the access control areas 43-1 to 43-4 of the first to fourth access control areas is a position corresponding to the division of the uplink subframe in the uplink signal frame 30, and this insertion Indicates the boundary between upstream subframes depending on the position.

【0041】

The area in the downlink frame 49 other than the first to fourth access control areas 43-1 to 43-4 is divided into the first to fourth downlink subframes 46-1 to 46-4. The first downlink subframe 46-1 contains the downlink signal for management, the second downlink subframe 46-2 accommodates the downlink STM signal 23-A in FIG. 1, and the third downlink subframe 46- 3 accommodates the downlink ATM signal 24-A in FIG. 1, and the fourth downlink subframe 46-4 accommodates the downlink ether packet signal 25-A in FIG. The boundary of each downlink subframe is described in the downlink subframe boundary display area 47 inserted at the beginning of each frame.

【0042】

If the ascending frame 30 and the descending frame 49 have a certain phase relationship, their start positions do not have to match in time.

【0043】

Next, FIG. 3 shows a second embodiment of the present invention. The present embodiment is the same as the first embodiment except that the structure of the downlink signal frame is different as shown in FIG. That is, in the present embodiment, the first to fourth access control areas 43-1 to 43-4 are collectively arranged at the beginning of each frame, and the boundary between the upstream subframes is described in the upstream subframe boundary display. The uplink control area 48 including the area 45 is arranged at the head position of the downlink frame 49. At this time, the downlink subframe boundary display area 47 is also arranged at the frame head position. The structure of the uplink is the same as in Fig. 2.

【0044】

Further, FIG. 4 shows a third embodiment of the present invention. In the present embodiment, the downlink code speed is 2.5 Gbps, the uplink code rate is 156 Mbps, and the downlink is divided into 16 channels having a code rate of 156 Mbps, which is equal to the uplink code rate. , One of them is configured to give an access control function. In this case, the channel having the access control function is set as the access control dedicated channel 58 dedicated to access control, and the polling signal 57 is used inside this channel. The access control dedicated channel 58 and the uplink are composed of a downlink frame 49 and an uplink frame 30 having a length of 125 μs, respectively. Like the up frame 30, the down frame 49 is composed of the first to fourth down subframes 46-1 to 46-4, and the first to fourth down subframes 46-1 to 46-4 are the first ones, respectively. The polling signal 57 corresponding to each time slot of the uplink subframes 31-1 to 31-4 of ~ 4 is transmitted. Therefore, the polling signals 57 of the first to fourth downlink subframes 46-1 to 46-4 are given the same length as the time slots in the corresponding uplink subframes, respectively. When each subscriber terminal receives the polling signal 57 addressed to its own device, each subscriber terminal accommodates the uplink signal cell in a time slot in the uplink corresponding to the received timing.

【0045】

Although the three embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the present invention.

【0046】

For example, there are a plurality of uplink subframes such as the first uplink subframe 31-1 and the second uplink subframe 31-2 in which one subscriber terminal 2 is always assigned a fixed time slot in the uplink subframe. In some cases, it is also possible to integrate these uplink subframes, construct an uplink signal cell in which one cell payload is composed of cell payloads concatenated with each other, and allocate a time slot to the uplink signal cell.

【0047】

In the present embodiment, the STM signal, the ATM signal, and the ether packet signal are all accommodated, but other signal formats can also be accommodated. In addition, the sign speeds of the uplink signal and the downlink signal are both 622 Mbps or 156 Mbps and 2.5 Gbps, but the speed is not limited to this. Furthermore, the length of the frame was set to 125 μs, but other than this is also possible. In the embodiment, the length of the upstream subframe is fixed, but if the length of the frame is constant, the length of each upstream subframe can be changed for each frame.

【0048】

[Effect of the invention]

As described above, the following effects can be obtained by the present invention.

【0049】

First, according to the communication system of the present invention, a plurality of subframes for signal transmission are set in a frame, and a time slot having a unique length is set for each subframe. Since various signals can be accommodated separately in the frame, it is possible to realize a communication system that can easily accommodate a plurality of signals having different signal formats without the need for conversion of signal formats such as transfer mode and format.

【0050】

Further, since the signal transmission can be performed independently for each signal in the subframe, the transmission quality of each signal can be easily guaranteed because the signals are not easily affected by each other.

【0051】

Further, according to the communication system of the present invention, for example, when a signal format conversion such as converting an STM signal into an ATM cell is performed, a surplus area in the cell is generated and the bandwidth utilization efficiency is lowered. For example, since various signals can be directly accommodated, the band utilization efficiency of the uplink signal can be improved.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows the structure of one Embodiment of this invention.

[Figure 2]

It is a figure which shows the 1st frame structure of this invention.

[Fig. 3]

It is a figure which shows the 2nd frame structure of this invention.

[Fig. 4]

It is a figure which shows the 3rd frame structure of this invention.

[Fig. 5]

It is a block diagram which shows the structure of the conventional example.

[Explanation of symbols]

1 Terminal equipment 2 Subscriber terminal 3 Passive fiber optic network 4 Down signal 5 Up signal 8-a Station side downlink signal multiplex circuit 8-b Subscriber side downlink signal termination circuit 9 Station side access control circuit 10-a Station side uplink signal termination circuit 10-b Subscriber side uplink signal multiplexing circuit 12 Subscriber side access control circuit 13-1 First buffer 13-2 Second buffer 14-1 First individual uplink signal generation circuit 14-2 Second individual uplink signal generation circuit 14-3 Third individual uplink signal generation circuit 16-1 First stored information signal 16-2 Second stored information signal 18 Bandwidth request signal 19 Upstream signal output timing control signal 20 Down signal light 21 Up signal light 22-a Station side WDM coupler 22-b Subscriber WDM Coupler 23 STM network 23-A Down STM signal 23-B Upstream STM signal 24 ATM network 24-A Down ATM signal 24-B upstream ATM signal twenty five Ethernet work 25-A Downstream Ether packet signal 25-B Upstream Ether Packet Signal 26 Access control signal 27-a Station side optical signal transmission circuit 27-b Subscriber side optical signal transmission circuit 28-a Station side optical signal receiving circuit 28-b Subscriber side optical signal receiving circuit 30 Up signal frame 31-1 1st upstream subframe 31-2 Second upstream subframe 31-4 4th upstream subframe 34-1 First uplink signal cell 34-2 Second uplink signal cell 34-3 Third uplink signal cell 37-1 1st uplink signal cell header 37-2 Second uplink signal cell header 37-3 Third uplink signal cell header 38-1 First uplink signal cell payload 38-2 Second uplink signal cell payload 38-3 Third uplink signal cell payload 43-1 First access control downlink cell 43-2 Down cell for second access control 43-3 Down cell for third access control 43-4 4th access control downlink cell 44-1 First time slot 44-2 Second time slot 44-3 Third time slot 44-4 4th time slot 45 Upstream subframe boundary position display area 46-1 1st downlink subframe 46-3 Third downlink subframe 46-4 4th downlink subframe 47 Downstream subframe boundary display area 48 Upline control area 49 Down signal frame 53 Concatenated time slot 54 Uplink packet 55 Uplink packet header 56 Uplink packet payload 57 Polling signal 58 Access control dedicated channel 131 ATM switch 132-a Station side CLAD 132-b Subscriber CLAD 133-a Station side ATM interface 133-b Subscriber ATM interface 134-a Station side ATM-PON downlink signal generation circuit 134-b Subscriber ATM-PON downlink signal termination circuit 135 ATM-PON downlink signal 136 Multiple separation circuit 137 ATM-PON uplink signal 138-a Station side ATM-PON uplink signal termination circuit 138-b Subscriber ATM-PON uplink signal termination circuit