JP2008160659A - Signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve transmission efficiency of a signal processor used for a communication device of an optical access network system. <P>SOLUTION: A signal cell of an ATM communication system is put in a GEM frame to be transmitted. A transmitter is provided with a port ID management table 510 containing port IDs to be allocated for each VPI/VCI stored in ATM cells. Then, the processor performs GEM frame generation processing 523 in which VPI/VCI is read out of the ATM cell and a port ID allocated to the VPI/VCI is read out of the port ID management table 510 to generate the GEM frame having the ATM cell put in a payload and the port ID put in a header, and GTC frame generation processing 525 wherein the GTC frame having the GEM frame stored is generated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a signal processing device used in an optical access network system capable of accommodating a plurality of types of frames. The present invention can be applied to, for example, GPON (Gigabit-capable Passive Optical Network).

  As a system for accessing a network such as the Internet using an optical fiber, for example, FTTx (Fiber To The Home / Curb / Node / Premises) is known. As a network for realizing FTTx, for example, PON (Passive Optical Network) is known.

  FIG. 9 is a conceptual diagram showing a schematic configuration of the PON. As shown in FIG. 9, a terminal unit (OLT; Optical Line Terminal) 901 on a central office side is connected to a plurality of subscriber-side terminal devices (ONU; Optical Network) via an optical fiber 903 branched by a splitter 902. Unit) 904-1 to 904-n. The OLT 901 is connected to a base network (regional IP (Internet protocol) network, the Internet, etc.) 905, and each ONU 904-1 to 904-n is connected to a communication terminal (personal computer or the like) 906-1 to 906-n. Yes.

  PON uses optical signals having different wavelengths for downstream communication and upstream communication. This makes it possible to perform bidirectional communication with a single optical fiber. As shown in FIG. 9, in downlink data transmission, communication frames addressed to the ONUs 904-1 to 904-n are time-division multiplexed and sent from the OLT 901 to the ONUs 904-1 to 904-n. Each ONU 904-1 to 904-n extracts only the communication frame addressed to itself from the received data using a technique such as encryption, and discards the other communication frames. On the other hand, in uplink data transmission, a communication frame is sent from each ONU 904-1 to 904-n to the OLT 901. At this time, each communication frame can be time-division multiplexed by the splitter 902 by appropriately adjusting the transmission timing of each of the ONUs 904-1 to 904-n. The OLT 901 sends a signal for controlling the uplink transmission timing to each ONU 904-1 to 904-n. The transmission timing in the upstream direction is determined in consideration of transmission delay variation between the splitter 902 and each ONU 904-1 to 904-n (that is, variation in distance between the optical coupler and the ONU).

  For example, GPON is known as the PON. GPON is an ITU-T (International Telecommunications Union-Telecommunications Sector) recommendation G.264. It is a network standardized by 984. GPON is an optical access network system that can accommodate an Ethernet (registered trademark, hereinafter the same) communication method, a TDM (Time Division Multiplexing) communication method, and an ATM (Asynchronous Transfer Mode) communication method. Here, Ethernet is a communication method used in the Internet, TDM is a communication method used in an existing telephone service, and ATM is a communication method used in all media communication of voice, data, and video. As documents disclosing GPON, for example, the following Patent Documents 1 and 2 and Non-Patent Document 1 are known.

  Hereinafter, a method of accommodating three types of communication methods of Ethernet, TDM, and ATM in GPON will be described separately for downlink communication and uplink communication.

  FIG. 10 is a conceptual diagram showing the structure of a communication frame in GPON. For GPON downlink communication, a frame having a period of 125 μsec called GTC (G-PON Transmission Convergence Layer) is used. As shown in FIG. 10, the GTC frame includes an overhead and a payload.

  The overhead is an area for storing information necessary for communication control, maintenance / operation, and the like, and as a frame header, PCBd (Physical Control Block downstream), that is, various information related to the frame is stored. The PCBd accommodates an upstream band map that is transmission control information of each ONU 904-1 to 904-n in upstream communication. In the example of FIG. 10, throttles “100” to “300” are assigned to Alloc-ID (Allocation Identifier) '1' (corresponding to ONU904-1 here), and Alloc-ID '2' (here ONU804-) is assigned. (Corresponding to 2) is assigned throttles '400' to '500', and Alloc-ID '3' (corresponding to ONU 904-3 here) is assigned throttles '520' to '600'. .

  The payload is an area for accommodating a user signal, and includes an ATM partition and a GEM (G-PON Encapsulation Method) partition. ATM cells are accommodated as they are in the ATM partition. A GEM frame is accommodated in the GEM partition. A GEM frame is a frame containing an Ethernet signal or a TDM signal (described later). Information indicating the boundary position between the ATM partition and the GEM partition is accommodated in the overhead PCBd.

  On the other hand, in the uplink signal, a frame composed of overhead and payload is used. Also in the upstream signal, in the case of an ATM signal, an ATM cell is directly mapped to the payload. In the case of an Ethernet signal or a TDM signal, the GEM frame is mapped after the GEM frame is formed.

  In FIG. 11, (A) is a conceptual diagram showing a layer configuration of a GTC frame, and (B) is a conceptual diagram showing a protocol stack. Each GTC framing sublayer 1110 of the ONUs 904-1 to 904-n reads the ATM signal from the ATM partition of the GTC frame based on the Alloc-ID when receiving the GTC frame for downlink communication, and from the GEM partition. Read the GEM frame. The TC (Transmission Convergence) adaptation sublayer 1120 captures an ATM signal (ATM TC adapter), and identifies a logical path using a VPI (Virtual Path Identifier) value and a VCI (Virtual Channel Identifier) value which are connection information of the ATM signal. Process (VPI / VCI filter) and output to ATM client. The TC adaptation sublayer 1120 captures a GEM signal (GEM TC adapter), and performs logical path identification processing using a port ID (Identification) value and a PTI (Payload Type Indicator) code as connection information of the GEM signal. (Port ID / PTI filter) and output to GEM client. The ATM client and the GEM client execute a predetermined service using the received ATM signal, Ethernet signal, or TDM signal.

  On the other hand, when performing upstream communication, the GTC framing sublayer 1110 of the ONUs 904-1 to 904-n generates a container corresponding to the Alloc-ID, accommodates the ATM signal or GEM frame in the payload of this container, and transmits it. (See FIG. 10). The containers transmitted from the ONUs 904-1 to 904-n are time-division multiplexed by the splitter 902 and transferred to the OLT 901 (see FIG. 9).

  FIG. 12A is a conceptual diagram showing the format of the GEM frame. As shown in FIG. 12A, the GEM frame has an overhead of 5 bytes (that is, 40 bits) and a payload of arbitrary bytes. Further, this overhead includes a 12-bit PLI (Payload Length Indicator), a 12-bit port ID, a 3-bit PTI, and a 13-bit HEC (Header Error Control). Here, PLI indicates the payload length, the port ID is connection information in the GPON, and the HEC is an area for correcting a header error. The meaning indicated by each code value of PTI is ITU-T recommendation G.264. 984 (see FIG. 12B).

  As mentioned above, ITU-T Recommendation G. In 984, an Ethernet signal or a TDM signal is accommodated in the GEM frame. At this time, one Ethernet signal or the like may be accommodated in one GEM frame or may be accommodated in a plurality of GEM frames. 13A shows an example in which one Ethernet signal or the like is accommodated in one GEM frame, FIG. 13B shows an example in which two Ethernet frames are accommodated, and FIG. 13C shows three GEMs. It is the example accommodated in the flame | frame. As shown in FIGS. 13A to 13C, in the last GEM frame (including the case where there is one GEM frame), the overhead PTI code is set to '001', and the other GEM frames Then, the PTI code is set to “000”. Further, when one Ethernet signal or the like is divided and accommodated in a plurality of GEM frames, these GEM frames can be divided and accommodated in a plurality of GTC frames. Thereby, it is possible to effectively use the payload of the GTC frame and improve communication efficiency. In the example of FIG. 13D, the first GTC frame (GTC1) contains a part of the first GEM frame (GEM1a) and the whole of the second GEM frame (GEM2). The GTC frame (GTC2) accommodates the rest of the first GEM frame (GEM1b) and the entire third GEM frame (GEM3). In FIG. 13D, PLOu (Physical Layer Overhead upstream) is an overhead area that accommodates a GTC frame preamble and the like.

  FIG. 14A is a conceptual diagram showing a method for accommodating an Ethernet signal in a GEM frame. In an Ethernet packet, IPG (Inter Packet Gap) is a signal corresponding to the waiting time from the previous packet transmission to the current packet transmission, preamble and SFD (Start Frame Delimiter) are signals indicating the start of frame transmission, DA (Destination Address) is the destination address, SA (Source Address) is the source address, Length / type is the information indicating the length or upper layer protocol of the data field, Mac client is the data field, and FCS (Frame Check Sequence) is an error. The detection data, EOF (End Of File), is the end of the Ethernet packet. In GPON, among these, DA, SA, Length / type, Mac client, and FCS are accommodated in the payload of the GEM frame.

FIG. 14B is a conceptual diagram showing a method for accommodating a TDM signal in a GEM frame. The TDM signal is accommodated in the payload of the GEM frame as it is.
JP 2004-320745 A JP 2004-320746 A Edited by ITU-T Study Group 15, 'SERIES G: TRANSMISSION SYSTEM AND MEDIA, DIGITAL SYSTEM AND NETWORKS', February 2004, published by INTERNATIONAL TELECOMMUNICATION UNION

  As mentioned above, ITU-T Recommendation G. In 984, it is specified that the ATM signal is accommodated in the ATM partition as it is, and the Ethernet signal and the TDM signal are accommodated in the GEM partition (see FIG. 10). The logical path of the ATM signal is determined using VPI / VCI, and the logical path of the Ethernet signal and the TDM signal is determined using the port ID value and the PTI code (see FIG. 11). Therefore, ITU-T Recommendation G. In the OLT and ONU conforming to 984, it is necessary to separately provide a processing function for ATM signals and a processing function for GEM frames (Ethernet signals and TDM signals). For this reason, GPON has the disadvantage that OLT and ONU are expensive.

  In the current communication service, the ATM communication method is used less frequently than the Ethernet communication method and the TDM communication method. For this reason, a technique for realizing a processing function for ATM signals at a low price is desired.

  Furthermore, in order to construct a GPON at a low price, it is desirable to increase the transmission efficiency when transmitting a GTC frame.

  An object of the present invention is to provide an optical access network system with high transmission efficiency at a low price.

  The present invention relates to an optical access network that supports both a first communication method in which a logical path is determined using first connection information and a second communication method in which a logical path is determined using second connection information. -It relates to the signal processing device of the system.

  Then, a management information storage unit that allocates and stores the first connection information for each second connection information, and the second connection information is read from the signal cell of the second communication method, and the first connection information allocated to the second connection information From the management information storage unit, an insertion frame generation processing unit for generating an insertion frame in which the signal cell is accommodated in the payload and the first connection information is accommodated in the header, and the propagation frame in which the insertion frame is stored A propagation frame generation processing unit.

  According to the present invention, when transmitting a signal cell of the second communication scheme, the insertion frame in which the signal cell is accommodated in the payload and the first connection information is accommodated in the header is generated. The signal cell of 2 communication systems and the signal cell of the 1st communication system can be accommodated in the insertion frame of the same standard. Therefore, according to the present invention, since the insertion frame can be unified by the first and second communication methods, the price of the signal processing device can be reduced.

  In addition, according to the present invention, by accommodating a plurality of insertion frames in one propagation frame, the propagation efficiency of the optical access network system can be improved, and the required number of second connection information can be reduced. It can be reduced to prevent the second connection information (for example, port ID) from being depleted.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the size, shape, and arrangement relationship of each component are shown only schematically to the extent that the present invention can be understood, and the numerical conditions described below are merely examples. .

First Embodiment As a first embodiment of the present invention, a case will be described in which the present invention is applied to a signal processing apparatus corresponding to a fixed bit rate optical access network system.

  An example of the signal processing apparatus of the present invention will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration example of a signal processing device mounted on an ONU. As described above, in the conventional signal processing apparatus, only the Ethernet signal and the TDM signal are mapped to the GTC frame, and the ATM is not mapped to the GEM frame (see FIG. 10). On the other hand, the signal processing apparatus 100 of this embodiment can map not only the Ethernet signal and the TDM signal but also the ATM signal to the GEM frame.

  Hereinafter, a case where an ATM signal is mapped to a GEM frame will be described as an example.

  The signal processing apparatus 100 includes a core unit 101a having a configuration that does not depend on the type of communication service, and a service unit 101b that depends on the type of individual communication service. The service unit 101b includes an Ethernet / GEM conversion function unit 112, a TDM / GEM conversion function unit 114, an ATM / GEM conversion function unit 116, a GEM / Ethernet conversion function unit 162, a GEM / TDM conversion function unit 164, and a GEM / ATM conversion. A function unit 166 and a port ID management unit 120 are included. The core unit 101a includes a GTC output unit 101c including a bandwidth management buffer function unit 130, a GEM mapping function unit 132, and a GTC framing function unit 134, a GTC decomposition function unit 150, a GEM extraction function unit 152, and a distribution function unit 154. A GTC input unit 101d including a mapping information extraction function unit 140 is included.

  Further, the signal processing apparatus 100 includes Ethernet interface units 102 and 172, TDM interface units 104 and 174, and ATM interface units 106 and 176, which input and output Ethernet signals, TDM signals, and ATM signals, respectively.

  Hereinafter, a part used for uplink communication among each component of the signal processing apparatus 100 will be described.

  As described above (see FIG. 9), the Ethernet signals, TDM signals, and ATM signals are input to the ONUs 904-1 to 904-n from the communication terminals 906-1 to 906-n on the subscriber side.

  The Ethernet interface unit 102 converts the input Ethernet signal into the ONU internal format, and sends the converted Ethernet signal to the Ethernet / GEM conversion function unit 112.

  The Ethernet / GEM conversion function unit 112 converts the Ethernet signal into a GEM frame. At this time, the Ethernet / GEM conversion function unit 112 receives the port ID necessary for generating the GEM frame from the port ID management unit 120 and uses the port ID for generating the GEM frame. The generated GEM frame is sent to the bandwidth management buffer function unit 130 and waits for output in a predetermined buffer.

  The TDM interface unit 104 converts the input TDM signal into an ONU internal format, and sends the converted TDM signal to the TDM / GEM conversion function unit 114.

  The TDM / GEM conversion function unit 114 converts the TDM signal into a GEM frame. At this time, the TDM / GEM conversion function unit 114 receives the port ID necessary for generating the GEM frame from the port ID management unit 120 and uses the port ID for generating the GEM frame.

  The ATM interface unit 106 converts the received ATM signal into the ONU internal format, and sends the converted ATM signal to the ATM / GEM conversion function unit 116.

  The ATM / GEM conversion function unit 116 converts the ATM signal into a GEM frame. At this time, the ATM / GEM conversion function unit 116 receives the port ID necessary for generating the GEM frame from the port ID management unit 120 and uses the port ID for generating the GEM frame.

  Thus, in the signal processing device of the present invention, in addition to the Ethernet signal and the TDM signal, the ATM signal is also accommodated in the GEM frame. FIG. 2 is a conceptual diagram illustrating a method for mapping ATM cells to GEM frames. The ATM cell is accommodated in the payload of the GEM frame as it is. A specific method for mapping (that is, accommodating) the ATM signal to the GEM frame will be described later (see FIGS. 5 and 6).

  The bandwidth management buffer function unit 130 receives GEM frames from the conversion function units 112 to 116 and temporarily accumulates them. Further, the bandwidth management buffer function unit 130 outputs these GEM frames in accordance with instructions from the GEM mapping function unit 132.

  The GEM mapping function unit 132 receives the GEM frame from the bandwidth management buffer function unit 130 and inputs mapping information from the mapping information extraction function unit 140, and outputs the GEM frame to the GTC framing function unit 134 at the timing indicated by the mapping information. To do. Here, the mapping information is information for determining the time division multiplexing position of the uplink GTC frame. Based on the mapping information, the timing for assigning the GEM frame to an appropriate output time slot on the GTC frame is determined. The function of the mapping information extraction function unit 140 will be described later.

  The GTC framing function unit 134 generates a GTC frame using the received GEM frame. That is, the GTC framing function unit 134 stores the GEM frame in which the time division multiplexing position is determined in the payload of the GTC frame, and generates the frame header of the GTC frame and stores it in the overhead.

  In this embodiment, since the Ethernet signal, the TDM signal, and the ATM cell are all mapped to the GEM frame, it is not necessary to provide an ATM partition (see FIGS. 10 and 11) in the payload of the GTC frame. As mentioned above, ITU-T Recommendation G. In 984, the boundary position between the ATM partition and the GEM partition can be arbitrarily set, and information indicating this boundary position is accommodated in the PCBd of the overhead. Therefore, the signal processing apparatus 100 according to this embodiment does not map the ITU-T recommendation G.D. GTC frames compliant with 984 can be used.

  The GTC frame generated by the GTC framing function unit 134 is output as an upstream signal from the PON interface of the ONU and sent to the OLT.

  Next, the part used for downlink communication among each component of the signal processing apparatus 100 is demonstrated.

  The ONU receives a GTC frame as a downlink signal from the OLT. The GTC frame received by the ONU is input from the PON interface of the ONU and sent to the GTC decomposition function unit 150.

  The GTC decomposition function unit 150 decomposes the GTC frame into an overhead and a payload. The GTC decomposition function unit 150 sends the payload of the GTC frame to the GEM extraction function unit 152 and sends the overhead to the mapping information extraction function unit 140.

  The mapping information extraction function unit 140 manages mapping information. The mapping information extraction function unit 140 extracts an uplink band map from the received overhead, and generates GEM mapping information from the uplink band map. As described above, this GEM mapping information is used when the GEM mapping function unit 132 determines the time division multiplexing position of the uplink signal.

  The GEM extraction function unit 152 extracts each GEM frame from the received payload. Each GEM frame extracted here is sent to the distribution function unit 154.

  The distribution function unit 154 determines whether each GEM frame includes an Ethernet signal, a TDM signal, or an ATM signal based on the port ID information received from the port ID management unit 120. The GEM frame including the Ethernet signal is sent to the GEM / Ethernet conversion function unit 162. The GEM frame including the TDM signal is sent to the GEM / TDM conversion function unit 164. The GEM frame including the ATM signal is sent to the GEM / ATM conversion function unit 166.

  When receiving the GEM frame, the GEM / Ethernet conversion function unit 162 converts the GEM frame into an Ethernet signal and sends the Ethernet signal to the Ethernet interface unit 172. The Ethernet interface unit 172 converts the Ethernet signal in the internal format into an appropriate format and outputs it to the communication terminal on the subscriber side.

  When the GEM / TDM conversion function unit 164 receives the GEM frame, the GEM / TDM conversion function unit 164 converts the GEM frame into a TDM signal and sends the TDM signal to the TDM interface unit 174. The TDM interface unit 174 converts the TDM signal in the internal format into an appropriate format and outputs it to the communication terminals 906-1 to 906-n on the subscriber side.

  Further, when receiving the GEM frame, the GEM / ATM conversion function unit 166 converts the GEM frame into an ATM signal and sends it to the ATM interface unit 176. The ATM interface unit 176 converts the ATM signal in the internal format into an appropriate format and outputs it to the communication terminal on the subscriber side.

  FIG. 3 is a conceptual diagram showing the layer configuration and protocol stack of the GTC frame according to this embodiment.

  As shown in FIG. 3A, the GTC frame includes an overhead for accommodating information necessary for communication control, maintenance / operation, and the like, and a payload for accommodating a user signal. Since the overhead is the same as that of the conventional GTC frame (see FIG. 11), the illustration and description are omitted here.

  A GEM partition is provided in the payload. The GEM partition accommodates a GEM frame including any one of an Ethernet signal, a TDM signal, and a non-GEM signal (ATM signal in this embodiment). For this reason, the GTC frame used in this embodiment does not include an ATM partition in the payload, and is different from the conventional GTC frame in this point. As described above, for example, by specifying the start position and length of the GEM partition in overhead, a GTC frame having no ATM partition is converted into an ITU-T recommendation G.264. 984.

  In the protocol stack shown in FIG. 3B, when receiving the GTC frame for downlink communication, the GTC framing sublayer 310 reads the GEM frame from the GEM partition of the GTC frame using the Alloc-ID filter 315. Of the functions performed by the GTC framing sublayer 310, the multiplexing 311 corresponds to the function in the GTC decomposition function unit 150. The GEM partition 313 corresponds to the function in the GEM extraction function unit 152.

  The TC adaptation sublayer 320 takes in the GEM frame (GEM TC adapter 321) and performs logical path identification processing using the port ID value and PTI (Payload Type Indicator) code (port ID / PTI filter 323). The Ethernet signal and TDM signal accommodated in the GEM frame are output as they are to the GEM client. On the other hand, the ATM signal accommodated in the GEM frame is subjected to logic identification processing (VPI / VCI filter 325) using the VPI value and the VCI value, and then output to the ATM client.

  Among the functions performed by the TC adaptation sublayer 320, the port ID / PTI filter 323 includes a distribution function unit 154, a GEM / Ethernet conversion function unit 162, a GEM / TDM conversion function unit 164, and a GEM / ATM conversion function unit 166. Corresponds to the function. The VPI / VCI filter 325 corresponds to the function in the GEM / ATM conversion function unit 166.

  Although not shown in FIG. 1, the GEM TC adapter 321 has a function of delivering a GEM frame from the GEM extraction function unit 152 to the distribution function unit 154. Note that, for example, logical identification processing using a MAC address in an Ethernet signal is also performed, but illustration and description thereof are omitted here.

  Next, a configuration example of a signal processing device mounted on the OLT will be described with reference to FIG. FIG. 4 is a block diagram illustrating a configuration example of a signal processing device mounted on the GPON OLT.

  The OLT receives an Ethernet signal, a TDM signal, an ATM signal, and the like from the base network side, for example.

  The Ethernet interface unit 402 provided in the OLT converts the received Ethernet signal into the OLT internal format, and sends the converted Ethernet signal to the Ethernet / GEM conversion function unit 412. Also, the TDM interface unit 404 provided in the OLT converts the received TDM signal into the internal format of the OLT, and sends the converted TDM signal to the TDM / GEM conversion function unit 414. Further, the ATM interface unit 406 provided in the OLT converts the received ATM signal into the internal format of the OLT, and sends the converted ATM signal to the ATM / GEM conversion function unit 416.

  In the Ethernet / GEM conversion function unit 412, the TDM / GEM conversion function unit 414 and the ATM / GEM conversion function unit 416, the port ID management unit 420, the bandwidth management buffer function unit 430, the GEM mapping function unit 432, and the GTC framing function unit 434, Since the function until generating the GTC frame from each signal is the same as that of the ONU described with reference to FIG. 1, the description thereof is omitted here.

  The GTC frame generated by the GTC framing function unit 434 is output as a downlink signal from the PON interface of the OLT and is sent to the ONU.

  The OLT receives a GTC frame from the ONU as an upstream signal. The GTC frame received by the OLT is input from the PON interface of the ONU and sent to the GTC decomposition function unit 450.

  GTC decomposition function unit 450, GEM extraction function unit 452, distribution function unit 454, GEM / Ethernet conversion function unit 462, GEM / TDM conversion function unit 464, GEM / ATM conversion function unit 466, Ethernet interface unit 472, TDM interface unit 474 In the ATM interface unit 476, the function until each signal is generated from the GTC frame is the same as the function in the ONU described with reference to FIG.

  The mapping information generation function unit 441 generates GEM mapping information of the uplink signal by calculating bandwidth allocation based on the bandwidth management information accommodated in the overhead of the GTC frame received from each ONU. The mapping information generation function unit 441 sends the generated GEM mapping information to the GEM mapping function unit 432.

  According to this configuration, Ethernet, TDM, and ATM signals handled by GPON are converted into GEM frames, whereby the signals are handled in a unified manner. For this reason, the circuit configuration is simplified and the circuit scale can be further reduced, such as eliminating the need for the ATM bandwidth management buffer function unit, ATM mapping function unit, and ATM extraction function unit.

  FIG. 5 is a conceptual diagram for explaining an operation when the signal processing apparatuses 100 and 400 according to this embodiment process ATM cells. Here, the operation of the signal processing apparatus 100 will be described as an example, but the operation of the signal processing apparatus 400 is the same.

  The port ID management table 510 corresponds to the port ID management unit 120 in FIG. The port ID management table 510 assigns and stores a port ID for each VPI / VCI of the ATM cell described above.

  The ATM / GEM conversion sequence 520 is a sequence for generating a GTC frame using an ATM cell input from the input port 521 and transmitting it from the output port 526. The ATM / GEM conversion sequence 520 includes an ATM cell buffer process 522, a GEM frame generation process 523, a timer 524, and a GTC frame generation process 525.

  The ATM cell buffer process 522 is a process for temporarily storing ATM cells input from the input port 521 and supplying the ATM cells to the GEM frame generation process 523. This processing is executed by the ATM / GEM conversion function unit 116 of FIG.

  The GEM frame generation processing 523 reads VPI / VCI from the ATM cell and reads the port ID assigned to the VPI / VCI from the port ID management table 510 (executed by the ATM / GEM conversion function unit 116). And a process of generating a GEM frame in which the ATM cell is accommodated in the payload and the port ID is accommodated in the header (executed by the GEM mapping function unit 132).

  The timer 524 is a process for generating a timing at which an ATM cell is read from the ATM cell buffer process 522 to the GEM frame generation process 523. This processing corresponds to timing management in which the GEM mapping processing function unit 132 in FIG. 1 reads a signal from the band management buffer function unit 130.

  The GTC frame generation process 525 is a process for generating a GTC frame containing a predetermined number of GEM frames. This process corresponds to the operation of the GTC framing function unit 134 of FIG.

  On the other hand, the GEM / ATM conversion sequence 530 is a sequence for decomposing a GTC frame input from the input port 531 and extracting an ATM cell. The GEM / ATM conversion sequence 530 includes a GTC frame decomposition process 532, a GEM frame decomposition process 533, and an ATM cell buffer process 534.

  The GTC frame decomposition process 532 is a process for extracting a GEM frame containing ATM cells from the GTC frame. This process is executed by the GTC decomposition function unit 150 in FIG.

  The GEM frame decomposition process 533 is a process of extracting an ATM cell and a port ID from the GEM frame (executed by the GEM extraction function unit 152) and the correspondence between the port ID and the VPI / VCI accommodated in the ATM cell. Is performed (executed by the distribution function unit 154).

  The ATM cell buffer process 534 is a process for temporarily accumulating ATM cells input from the GEM frame decomposition process 533. This process is executed by the GEM / ATM conversion function unit 166 of FIG.

  FIG. 6 is a conceptual diagram for explaining the overall communication operation of the optical access network system according to this embodiment. FIG. 6 shows an example in which three ONUs 621 to 623 are connected to one OLT 610. Here, the case of uplink communication will be described as an example, but the communication operation in the case of downlink communication is also the same.

  In FIG. 6, an OLT 610 includes a PON interface unit 611 that communicates with ONUs 621 to 623, a WAN interface unit 612 that communicates with an external network (such as the Internet), and a switch that switches connections between the interface units 611 and 612. Part 613. The signal processing apparatus (see FIG. 1) according to this embodiment is provided in the WAN interface unit 612. On the other hand, each ONU 621 to 623 is also provided with the signal processing device of this embodiment. Between the OLT 610 and the ONUs 621 to 623, ATM connections having a constant bit rate (Constant Bit Rate: CBR) are provided.

  The GPON GTC frame transmission period is 125 μs. On the other hand, in the example of FIG. 6, the number of connections of each ONU 621 to 623 is different from each other. In this example, each ONU 621 to 623 transmits one GTC frame every 125 μs using all of its own ATM connections. Therefore, the data length of the GTC frame transmitted by each ONU 621 to 623 is determined according to the number of ATM connections of the ONU. For this reason, the total ΣPCR of the accommodated ATM connection bandwidth is obtained for each of the ONUs 621 to 623. Since the system of this embodiment uses a fixed bit rate, the length of one GTC frame (that is, the number of bytes that can be transmitted every 125 μs) is determined from this sum ΣPCR, and is therefore accommodated in this GTC frame. The payload length of the GEM frame is also determined. ITU-T Recommendation G. In 984, the GEM frame length is arbitrary, and is determined by the value accommodated in the PLI (see FIG. 12) in the overhead. Therefore, the size of one GTC frame can be arbitrarily set according to the ATM connection bandwidth. For this reason, ATM cells can be efficiently transmitted without wasting bandwidth.

  In the ONUs 621 to 623, the cycle in which the timer 524 (see FIG. 5) outputs the timing signal is set to 125 μs. Therefore, the GEM frame generation process 523 generates a GEM frame every 125 μs, and accommodates the ATM cell received from the ATM cell buffer process 522 in the payload of the GEM frame. As described above, the data length of the ATM cell to be accommodated is predetermined according to the number of ATM connections. Further, the GEM frame generation processing 523 reads VPI / VCI from the accommodated ATM cell, and reads the port ID corresponding to this VPI / VCI from the port ID management table 510. The GEM frame generation process 523 accommodates this port ID in the overhead of the GEM frame. Then, the GTC frame generation processing 525 maps this GEM frame on the GTC frame and outputs it from the output port 526.

  In the signal processing apparatus on the OLT 610 side, the input port 531 receives the GTC frame, the GTC frame decomposition processing 532 extracts the GEM frame from the received GTC frame, and the GEM frame decomposition processing 533 extracts the ATM cell and the port ID from the GEM frame. It is extracted and the correspondence between this port ID and the VPI / VCI accommodated in the ATM cell is checked. If the correspondence is correct, the ATM cell is output from the output port 535 via the ATM cell buffer process 534.

  As described above, in this embodiment, ATM cells are accommodated in a GEM frame and transmitted. Therefore, not only the ATM cell payload (that is, user data) but also the ATM cell overhead is stored in the payload of the GEM frame. Here, the ATM cell is composed of a 5-byte overhead and a 48-byte payload, and the GEM frame has a 5-byte overhead. Therefore, when only one ATM cell is accommodated in one GEM frame, an overhead of 10 bytes is added when transmitting 48 bytes of user data. That is, in this case, 17.2% of the transmission data is overhead information. As described above, when only one ATM cell is accommodated in one GEM frame, the ratio of overhead information to user data to be actually transmitted becomes very high, and transmission efficiency is lowered. On the other hand, in this embodiment, since one GEM frame is transmitted using a plurality of ATM connections, it is possible to accommodate a large number of ATM cells in one GEM frame. The ratio of overhead information to user data to be transmitted can be reduced.

  In addition, when only one ATM cell is accommodated in one GEM frame, the number of GEM frames to be transmitted increases, and the number of necessary port IDs also increases. For this reason, there is a high possibility that the port ID will be exhausted. In contrast, in this embodiment, since the GEM frame is used for transmission of the ATM cell, it is easy to reduce the number of port IDs to be used and prevent the number of port IDs from being exhausted.

  6 illustrates the example in which the signal processing apparatus according to this embodiment is provided in the WAN interface unit 612, the signal processing apparatus may be provided in the PON interface unit 611. However, providing the WAN interface unit 612 makes it easier to reduce costs. In the WAN interface unit 612, ATM signal processing such as UPC (Usage Parameter Control) processing and shaper processing is performed, and it is better to perform ATM / GEM conversion processing and GEM / ATM conversion processing consistently with these processing. This is because the circuit configuration can be simplified.

  In the example of FIG. 6, one GEM frame is accommodated using all the ATM connections accommodated in the ONUs 621 to 623, but other methods such as accommodating one GEM frame for each connection, for example. But you can. In the example of FIG. 6, the transmission timing of the GEM frame is matched with the GPON frame transmission period (125 μs), but it is not always necessary to match, and it may be earlier or later than this period. . That is, the number of connections to be used and the transmission cycle of the GEM frame can be appropriately set according to the characteristics of the communication service and the communication band.

  In FIG. 6, the case where the ATM cell is accommodated in the GEM frame has been described as an example. However, the communication operation illustrated in FIG. 6 can also be applied to the case where the Ethernet signal or the TDM signal is accommodated in the GEM frame. . By determining the payload length of the GEM frame that accommodates Ethernet signals and TDM signals according to the total bandwidth used (that is, the number of connections used), these signals can be transmitted efficiently without wasting bandwidth. can do.

  As described above, according to this embodiment, since ATM cells can be accommodated in a GEM frame and transmitted, the configuration of the signal processing device can be simplified and the price can be reduced.

  In addition, according to this embodiment, a plurality of ATM cells can be combined to accommodate one GEM frame, and as described above, the overhead for the ATM cell payload (that is, the number of user data transmission bytes) Therefore, it is possible to reduce the number of bytes and thus increase the transmission efficiency.

  Furthermore, according to this embodiment, since a plurality of connections can be used together for transmission of one GEM frame, as described above, the port ID can be prevented from being exhausted and used effectively. .

Second Embodiment Next, as a second embodiment of the present invention, a case will be described in which the present invention is applied to a signal processing apparatus compatible with a variable bit rate optical access network system.

  FIG. 7 is a block diagram showing the port ID management table, ATM / GEM conversion unit, and GEM / ATM conversion unit according to this embodiment. In FIG. 7, components denoted by the same reference numerals as those in FIG. 5 are the same as those in FIG. 5.

  In the ATM / GEM conversion sequence 700 according to this embodiment, a GEM frame generation process 710 is different from the GEM frame generation process 523 according to the first embodiment described above. The GEM frame generation processing 710 of this embodiment matches the payload length of the generated GEM frame with the total sum of ATM cells stored in the ATM cell buffer processing 522 instead of a fixed size. However, the payload length of the GEM frame is set so that the transmission band of the GEM frame does not exceed a predetermined maximum band (described later). Similar to the first embodiment, the GEM frame generation processing 710 reads the port ID corresponding to the VPI / VCI of the ATM cell from the port ID management table 510 and stores it in the overhead of the GEM frame.

  FIG. 8 is a conceptual diagram for explaining the overall communication operation of the optical access network system according to this embodiment. FIG. 8 shows an example in which three ONUs 821 to 823 are connected to one OLT 810. Here, the case of uplink communication will be described as an example, but the communication operation in the case of downlink communication is also the same.

  In FIG. 8, an OLT 810 includes a PON interface unit 811 that communicates with ONUs 821 to 823, a WAN interface unit 812 that communicates with an external network (such as the Internet), and a switch that switches connections between the interface units 811 and 813. Part 813. The signal processing apparatus (see FIG. 1) according to this embodiment is provided in the WAN interface unit 812. On the other hand, each of the ONUs 821 to 823 is also provided with the signal processing device of this embodiment. A variable bit rate ATM connection is provided between the OLT 810 and the ONUs 821 to 823, respectively.

  The GPON GTC frame transmission period is 125 μs. In the example of FIG. 8, the number of connections of each ONU 821 to 823 is different from each other.

  In the ONUs 821 to 823, the cycle in which the timer 524 (see FIG. 7) outputs the timing signal is set to 125 μs. The GEM frame generation processing 710 checks whether or not the total number of bytes of ATM cells accumulated in the ATM cell buffer processing 522 exceeds the total number of bytes that can be transmitted in the maximum bandwidth ΣPCR. A GEM frame that accommodates the cell is generated. Then, the GEM frame generation processing 710 accommodates the ATM cell received from the ATM cell buffer processing 522 in the payload of the GEM frame. On the other hand, when the total number of bytes of ATM cells accumulated in the ATM cell buffer process 522 exceeds the total number of bytes that can be transmitted in the maximum bandwidth ΣPCR, the GEM frame generation process 710 discards the excess ATM cells or Tagging is performed, and only ATM cells corresponding to the maximum bandwidth ΣPCR are accommodated in the GEM frame. If no ATM cell is stored in the ATM cell buffer process 522, the GEM frame generation process 710 does not generate a GEM frame. Thus, the bandwidth can be used effectively by determining the payload length of the GEM frame in accordance with the size of the ATM cell.

  Thereafter, the GEM frame generation processing 710 reads VPI / VCI from the accommodated ATM cell, and reads the port ID corresponding to this VPI / VCI from the port ID management table 510. The GEM frame generation process 710 accommodates this port ID in the overhead of the GEM frame. Subsequently, the GTC frame generation processing 525 maps this GEM frame on the GTC frame and outputs it from the output port 526.

  In the signal processing apparatus on the OLT 810 side, as in the first embodiment, the input port 531 receives the GTC frame, the GTC frame decomposition process 532 extracts the GEM frame from the received GTC frame, and the GEM frame decomposition process 533 The ATM cell and port ID are extracted from the frame, and the correspondence between the port ID and the VPI / VCI accommodated in the ATM cell is checked. If the correspondence is correct, the ATM cell is output from the output port 535 via the ATM cell buffer process 534.

  In FIG. 8, the example in which the signal processing apparatus according to this embodiment is provided in the WAN interface unit 812 has been described. However, such a signal processing apparatus may be provided in the PON interface unit 811. However, providing the WAN interface unit 812 makes it easier to reduce costs. In the WAN interface unit 812, ATM signal processing such as UPC (Usage Parameter Control) processing and shaper processing is performed, and it is better to perform ATM / GEM conversion processing and GEM / ATM conversion processing consistently with these processing. This is because the circuit configuration can be simplified.

  In the example of FIG. 8, a case has been described in which all of the ATM connections accommodated in the ONUs 821 to 823 can be used for transmission of one GEM frame. For example, one GEM frame is accommodated for each connection. Other methods may be used. In the example of FIG. 8, the transmission timing of the GEM frame is matched with the GPON frame transmission cycle (125 μs), but it is not always necessary to match, and it may be earlier or later than this cycle. Good. That is, the number of connections to be used and the GEM frame transmission cycle can be appropriately set according to the characteristics of the communication service and the communication band.

  In FIG. 8, the case where the ATM cell is accommodated in the GEM frame has been described as an example. However, the communication operation illustrated in FIG. 8 can also be applied to the case where the Ethernet signal or the TDM signal is accommodated in the GEM frame. . By determining the payload length of the GEM frame that accommodates Ethernet signals and TDM signals according to the total bandwidth used (that is, the number of connections used), these signals can be transmitted efficiently without wasting bandwidth. can do.

  According to this embodiment, since the ATM cell can be accommodated in the GEM frame and transmitted as in the first embodiment, the configuration of the signal processing device can be simplified and the price can be reduced.

  In addition, according to this embodiment, since the length of the GEM frame is determined according to the length of the ATM cell, the number of overhead bytes for the payload of the ATM cell can be reduced, and thus the transmission efficiency can be increased. It is possible to prevent the port ID from being exhausted.

It is a block diagram which shows the structure of the ONU side signal processing apparatus which concerns on 1st Embodiment. It is a conceptual diagram which shows the method of mapping the ATM signal which concerns on 1st Embodiment to a GEM frame. It is a conceptual diagram which shows the GPON layer structure and GPON protocol stack of the signal processing apparatus which concerns on 1st Embodiment. It is a block diagram which shows the structure of the OLT side signal processing apparatus which concerns on 1st Embodiment. It is a block diagram which shows the principal part structure of the signal processing apparatus which concerns on 1st Embodiment. It is a conceptual diagram for demonstrating the whole communication operation | movement of the optical access network system which concerns on 1st Embodiment. It is a block diagram which shows the principal part structure of the signal processing apparatus which concerns on 2nd Embodiment. It is a conceptual diagram for demonstrating the whole communication operation | movement of the optical access network system which concerns on 2nd Embodiment. It is a conceptual diagram which shows schematic structure of PON. It is a conceptual diagram which shows the structure of the frame for GPON downlink communication. (A) is a conceptual diagram showing a layer configuration of a GTC frame, and (B) is a conceptual diagram showing a protocol stack of GPON. It is a figure for demonstrating the format of a GEM frame, (A) is a conceptual diagram, (B) is a PTI code table. (A)-(D) is a conceptual diagram for demonstrating the structure of a GEM frame. (A) is a conceptual diagram illustrating a method for mapping an Ethernet signal to a GEM frame, and (B) is a conceptual diagram illustrating a method for mapping a TDM signal to a GEM frame.

Explanation of symbols

510 Port ID table 521, 531 Input port 522 ATM cell buffer processing 523, 710 GEM frame generation processing 524 Timer 525 GTC frame generation processing 526, 535 Output port 610, 810 OLT
611, 811 PON interface unit 612, 812 WAN interface unit 613, 813 Switch unit 621, 622, 623, 821, 822, 823 ONU
700 ATM / GEM converter

Claims (7)

Optical access network system signal corresponding to both the first communication method in which the logical path is determined using the first connection information and the second communication method in which the logical path is determined using the second connection information A processing device comprising:
A management information storage unit for allocating and storing the first connection information for each second connection information;
Reading the second connection information from the signal cell of the second communication method, reading the first connection information assigned to the second connection information from the management information storage unit, the signal cell is accommodated in a payload, and the An insertion frame generation processing unit for generating an insertion frame in which the first connection information is accommodated in the header;
A propagation frame generation processing unit for generating a propagation frame in which the insertion frame is stored;
A signal processing apparatus comprising: A propagation frame decomposition processing unit for extracting the insertion frame in which the signal cell of the second communication method is accommodated from the propagation frame;
An insertion frame decomposition processing unit for extracting the signal cell and the first connection information from the insertion frame, and checking a correspondence relationship between the first connection information and the second connection information accommodated in the signal cell; ,
The signal processing apparatus according to claim 1, further comprising:   When the signal cell of the second communication method is accommodated in the insertion frame, the number of bytes of the signal cell accommodated in the insertion frame is fixed so that the entire bandwidth of the connection to be used is used. The signal processing device according to claim 1, wherein the signal processing device is set as follows.   When the signal cell of the first communication method is accommodated in the insertion frame, the number of bytes of the signal cell accommodated in the insertion frame is fixed so that the entire bandwidth of the connection to be used is used. The signal processing device according to claim 3, wherein the signal processing device is set.   When accommodating the signal cell of the second communication method in the insertion frame, the number of bytes of the signal cell accommodated in the insertion frame does not exceed the total bandwidth of the connection to be used, The signal processing apparatus according to claim 1, wherein the signal processing apparatus is variably set so that all the signal cells input after the previous transmission are transmitted.   When the signal cell of the first communication method is accommodated in the insertion frame, the number of bytes of the signal cell accommodated in the insertion frame is within the range not exceeding the total bandwidth of the connection to be used. The signal processing apparatus according to claim 5, wherein the signal processing apparatus is variably set so that all of the signal cells input after transmission are transmitted.   The first communication method is at least one of Ethernet or TDM, the second communication method is ATM, the insertion frame is a GEM frame, and the propagation frame is a GTC frame. The signal processing device according to claim 1.

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