JP2008289202A - Transmitter and network system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication technology with a delay kept constant for supporting data communication requiring a telephone line or a real-time property. <P>SOLUTION: In the transmitter for transferring data among a plurality of optical network devices, a subsequent basic cycle frame contains: fixed band data with a transmission position and a transmission band fixed; and variable band data configured of variable length packets and having unfixed transmission band. The transmission position is allocated to the fixed band data for each frame of an integral multiple of the basic cycle frame so that an optical subscriber device sends the fixed band data at an interval of the integral multiple of a cycle of the basic cycle frame. Then, after the transmission position is allocated to the fixed band data, in the frame based on the integral multiple of the basic cycle frame, a band allocation amount to the variable band data is calculated at a position which does not overlap with the fixed band data, to further allocate the transmission position. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmission apparatus that divides and transmits data in units of frames or packets, and in particular, a transmission apparatus that is physically or logically connected to a plurality of terminal apparatuses and multiplexes and accommodates the connections with the plurality of terminal apparatuses. The present invention relates to a bandwidth allocation device that controls the data transmission amount of each terminal device. Specifically, it is a subscriber line terminator that provides a connection line from a user's home or office building or apartment house to a carrier's user line accommodation station, using an optical cable for the access line, wavelength multiplexing or time multiplexing. The present invention relates to a line terminator that multiplexes data from user terminals according to a method and dynamically controls an allocated bandwidth in response to a data transmission request from a user.

  The transmission capacity of the access line is expanding from xDSL to FTTH, and information services provided on the network are diversified. This is because the transmission amount of data-related traffic such as Web browsing and downloading has been increasing year by year, and the necessity of traffic control requiring real-time characteristics represented by IP telephone service has increased.

The impact of service diversification is more conspicuous in access lines and access networks closer to user terminals than in core networks. In access infrastructure services, more complex QoS control than before is required according to user contracts and service types. Here, the QoS function determines the processing priority for each packet in the packet network, and data with high real-time properties is processed as priority data. However, priority setting levels are limited in priority control, and it is difficult to always process real-time packets at a constant rate. In other words, real-time data is always transmitted at a constant timing (transmission amount) at a constant timing, as realized in a conventional telephone network or a synchronous multiplex communication network using an SDH (Synchronous Digital Hierarchy) system. There is a need. With this control, the synchronous multiplex communication network can ensure the stability of communication quality and the reliability of network management. However, it is difficult to perform this control with QoS control.

  From the above, traffic control conditions in the access network can be roughly classified into two types due to the diversification of services. One is strict communication timing control, and the other is on-demand wide band reservation. Currently, the access environment is a hybrid type in which an SDH network and an IP network are provided on the WAN side in a carrier accommodation station. Therefore, in order to improve the service quality in the access system infrastructure, it is necessary to multiplex this bipolar access system traffic on the access line. On the other hand, GE-PON is being put into practical use in response to network desynchronization (IP). The current situation is parallel operation with the existing infrastructure, but it is expected to be integrated into the next generation network centering on the packet network. Affinity with the existing synchronous network is an indispensable function in the network transition period and provision of wide area connection services.

  Focusing on the widespread use of data communications, GE-PON (Gigabit Ethernet-Passive Optical Network) that uses variable-length packets for access networks has been standardized and is being introduced. In recent years, there has been a large movement to replace a conventional fixed telephone with a service using an IP network (so-called IP telephone), and the development of an access network based on Ethernet (registered trademark, the same shall apply hereinafter) is steadily progressing. Ethernet is expected to become the main technology for future access network development because of its ease of handling.

However, network management functions are not well organized in Ethernet as in the conventional SDH network. Furthermore, because it is a perfect best effort packet communication network, behind the ease of installation,
It has the aspect that it is difficult to guarantee the reliability of communication. In the future, where the network will become an indispensable information infrastructure in balance with service diversification, it is expected that demand will increase in the future in terms of communication reliability, communication safety, and confidentiality (security). In particular, in business activities, it is considered necessary to use a synchronous communication network that has been conventionally used for leased line services until the guarantee of reliability and safety in an asynchronous communication network is realized.

ITU-T G. Even in the G-PON (Gigabit-capable Passive Optical Network) system defined in 984, E1, T, which have been used for dedicated line services.
The simultaneous accommodation of fixed-band communication (synchronous multiplex frame) for one line and Ethernet variable-band data (asynchronous variable-length frame) used for data services is required. In this multiplexing, securing the quality of fixed band communication (used for voice communication or the like) becomes a problem. Therefore, the present invention proposes a bandwidth management method that identifies two traffic characteristics of fixed / variable bandwidth data communication and performs time scheduling in stages.

  The present invention is not limited to the PON system in particular, and can be applied to a bandwidth control apparatus and a dynamic bandwidth control method in a system that generally performs communication by time division multiplexing.

  Traffic that currently flows on the network can be broadly classified into a real-time type in which a transmission time slot (transmission timing) is fixed and a best effort type in which the transmission time slot changes depending on the traffic. For bandwidth control in a packet communication path using variable length data, for example, conventionally, for example, an OLT (Optical Line Terminal) of B-PON (Broadband Passive Optical Network), one bandwidth control table is provided in the bandwidth control device and fixed. Band data and variable band data have been handled in the same line.

For variable band data, it is necessary to calculate an allocated band for every fixed period and dynamically allocate it. However, when fixed bandwidth data and variable bandwidth data are handled by a single bandwidth control table, fixed bandwidth data is affected by variable bandwidth data, and dynamic bandwidth allocation to fixed bandwidth data is difficult. Constant communication CBR (Constant Bit Rate) communication cannot be performed stably. Specifically, when all traffic is handled equally, it is necessary to refer to the usage status of the variable bandwidth even when the fixed bandwidth is allocated. When fixed bandwidth data and variable bandwidth data are mixed, the fixed bandwidth data is secured. A resource that should have been used may be used to transmit other data. Therefore, TDMA (Time Division Multiplexing Access)
It is difficult to guarantee a fixed bandwidth for traffic of fixed bandwidth data while controlling variable bandwidth data and fixed bandwidth data in the same row. For this reason, the packet arrival time interval of the fixed band data changes and jitter occurs. In addition, fixed bandwidth data can be processed efficiently in the same way and frequency as variable bandwidth data when bandwidth allocation is calculated, even though the bandwidth used is universal and the communication cycle is constant during communication. There is a possibility of degrading.

  In packet communication using variable-length data such as Ethernet, a certain amount of data cannot be sent within a certain period, and jitter cannot be suppressed. In addition, even in ATM, jitter cannot be completely suppressed, and in order to cope with this, a mechanism for keeping the cell arrival interval constant during a fixed communication session is required. To suppress jitter, periodic communication control is indispensable, which is a method that has been used in conventional SDH. We propose a dynamic bandwidth allocation method that takes advantage of the characteristics of variable-length frames used for asynchronous communications in TDMA-based periodic bandwidth control so as not to impair bandwidth utilization efficiency in asynchronous communications.

An object of the present invention is to provide a communication technique that maintains a constant delay in order to support data communication requiring a telephone line or real-time property in a network in which various types of network service traffic having different required qualities coexist.

  The present invention is a transmission apparatus that performs data transmission / reception with a plurality of optical network apparatuses via one or a plurality of connection lines, and includes a basic periodic frame in which small frames transmitted from each of the optical network apparatuses are multiplexed. A receiving unit to receive; a memory in which a program is stored; a processor that reads the program from the memory and processes the basic period frame; and a basic period subsequent to the received basic period frame calculated by the processor A transmission unit that transmits bandwidth allocation information to the frame to the optical subscriber unit, and the subsequent basic period frame includes fixed-band data in which a transmission position and a transmission band are fixed, and a variable-length packet. And variable bandwidth data whose transmission bandwidth is not fixed, and the processor is configured such that the optical subscriber unit is the base. A transmission position is allocated to the fixed band data for each frame that is an integral multiple of the basic periodic frame so that the fixed band data is transmitted at an interval that is an integral multiple of the period of the periodic frame, and the transmission position is assigned to the fixed band data. After the allocation, a bandwidth allocation amount for the variable bandwidth data is calculated at a position that does not overlap with the fixed bandwidth data in a frame whose unit is an integral multiple of the basic period frame, and a transmission position is further allocated.

  In the present invention, the transmission position is transmitted to the fixed band data every frame that is an integral multiple of the basic period frame so that the optical subscriber unit transmits the fixed band data at an interval that is an integral multiple of the period of the basic period frame. And assigning the transmission position to the fixed band data, and then calculating a bandwidth allocation amount to the variable band data at a position that does not overlap the fixed band data in a frame whose unit is an integral multiple of the basic period frame. Further, since the transmission position is allocated, the fluctuation of the position of the time slot of the fixed band data is eliminated and the fluctuation of the arrival delay time of the data is not caused. For delayable data (variable bandwidth data), the bandwidth can be effectively utilized by dynamically changing the allocated bandwidth size.

  In addition, when a plurality of services having different requirements for traffic control are multiplexed on an access line or the like, it is possible to suppress the mutual influence of traffic and ensure stable communication quality.

  The present invention relates to a band allocation method, and it does not matter whether an optical signal or an electrical signal is used as a transmission medium in the physical layer of the OSI reference model. However, here, as a most preferable application example of the present invention, a band allocation method and apparatus in a PON system used for a user access line are assumed and described.

  FIG. 1 is a block diagram showing a configuration of a subscriber termination network configured using a PON system according to an embodiment of the present invention.

  This network includes OLTs 1-1 to 1-3, ONUs 2-1 to 2-3, optical splitters 3-1 to 3-3, optical fibers 10-1 to 10-3, and 11-1-1 to 11-3. -3. A plurality of OLTs 1-1 to 1-3 are provided at the edge of the user accommodation network, and each OLT accommodates a plurality of ONUs. Each of the OLTs 1-1 to 1-3 includes a plurality of PON-IFs (described later in the description of FIG. 2). For example, the OLT 1-2 includes an optical fiber 10-1, a splitter 3-1, and an optical fiber 11-1-2. Through the optical fiber 10-2, splitter 3-2, and optical fiber 11-2-2, and further through the optical fiber 10-3, splitter 3-3, and optical fiber 11. It is connected to the ONU 2-3 via 3-2.

  The splitters 3-1 to 3-3 are optical fibers 11-1-1 to 11-1-3, respectively, which branch signals sent from the OLT 1-2 through the optical fibers 10-1 to 10-3 to the ONU side. Branches (copies) to 11-2-1 to 11-2-3 and 11-3-1 to 11-3-3. Further, the splitter is sent from the ONU to the OLT 1-2 sent through the optical fibers 11-1-1 to 11-1-3, 11-2-1 to 11-2-3, and 11-3-1 to 11-3-3. Are transmitted on the common optical fibers 10-1, 10-2, 10-3, respectively, and transmitted to the OLT 1-2.

  At this time, for example, when paying attention to the optical fiber 10-2, the upstream signals transmitted from the plurality of ONUs including the ONU 2-2 through the optical fibers 11-2-1 to 11-2-3 are shared at the respective timings received. It is transmitted to the optical fiber 10-2. A multiplexing system using TDMA is used so that upstream signals from the ONUs do not overlap. In communication with the ONUs connected to the optical fibers 10-1 to 10-3, the OLT 1-2 notifies the individual ONUs of the transmission timing and the amount of transmittable data used for uplink communication. The transmission timing control using the TDMA method for allocating the communication band to the ONU is performed.

  The ONUs 2-1 to 2-3 accommodate subscriber data communication terminal devices 20-1 to 20-3 and TDM (Time Division Multiplexing) terminal devices 30-1 to 30-3, respectively. The former targets services such as PCs and mobile communication terminals that require data transmission efficiency such as browsing of WWW (World Wide Web) information and data download. The main connection service is Ethernet. Further, the TDM terminal device is connected to an ONU TDM interface (described later).

  With this interface, the ONUs 2-1 to 2-3 accommodate synchronous multiple frame communication (TDM communication) using a T1 line or an E1 line. This service is a communication method for multiplexing information by synchronizing communication control between information transmission side and reception side devices, and a typical example thereof is a telephone service using a circuit switching method. A plurality of data communication terminals and TDM terminals can be accommodated for each ONU.

  2 shows OLTs 1-1 to 1-3 (hereinafter referred to as OLT1 as a representative when describing the OLT) and ONUs 2-1-1 and 2-1-1 (hereinafter referred to as representatives) constituting the network of FIG. Device configuration) and a network connection form configured thereby. This drawing is a functional block diagram for explaining the flow of subscriber communication data in the PON system.

  The OLT 1 includes PON interfaces 200-1 to 200-n, an L2SW 130, Ethernet interfaces 110-1 to 110-n1, and TDM interfaces 120-1 to 120-n2. The PON interfaces 200-1 to 200-n terminate an optical signal transmitted through an optical fiber line. In the processing performed by the PON interfaces 200-1 to 200-n, the data format used for communication control of the Ethernet frame or TDM data and the PON section (between the OLT and the ONU PON interface) when transmitting data from the OLT 1 to the ONU 2 Conversion, bandwidth control for downstream data delivery, bandwidth allocation to ONUs for upstream data communication, and electrical signal and optical signal mutual conversion.

  The L2SW (L2 switch) 130 multiplexes the signal from the Ethernet interface 110 and the signal from the TDM interface 120 and sends the multiplexed signal to the PON interface 200. Further, the L2SW 130 decomposes the signal from the PON interface 200 and sends it to the Ethernet interface 110 or the TDM interface 120.

  The Ethernet interface 110 includes a data interface and is connected to the packet switching network 2001. The Ethernet interface 110 sends the packet input from the packet switching network 2001 to the L2SW 130. Further, the data received by the PON interface 200 is received from the L2SW 130. The packet switching network 2001 is a network that does not need to occupy a line until the end of data transmission, such as Ethernet.

  The TDM interface 120 includes a TDM line interface such as E1 or T1, and is connected to the circuit switching network 2002. The TDM interface 120 sends the packet input from the circuit switching network 2002 to the L2SW 130. Further, the data received by the PON interface 200 is received from the L2SW 130. The circuit switching network 2002 is a network that occupies a line until the end of data transmission, such as an SDH network or an ISDN network.

  Between PON interfaces (PON section), a bandwidth is allocated for each bandwidth management ID. Bandwidth is the amount of data in a time-divided time slot. The OLT 1 notifies the ONU 2 of bandwidth allocation for each management ID. The ONU 2 transmits data in the band notified from the OLT 1.

  The splitter 3 is a branching device provided in the middle of the optical fiber network. For example, a star coupler is used. A splitter 3 multiplexes signals from a plurality of ONUs 2. Between the splitter 3 and the OLT 1, fixed band data (TDM data) and variable band data (Ethernet data) are mixed on the same fiber.

  The ONU 2 transmits the packet accumulation status of the transmission queue to the OLT 1 and requests a transmission band. When the OLT 1 receives the packet accumulation status from the ONU 2, the OLT 1 adjusts the data transmission timing of the ONU 2 by dynamic bandwidth control using TDMA and notifies the ONU 2 of the transmission timing. The ONU 2 transmits a packet to the OLT 1 at the timing notified from the OLT 1. Thereby, the collision of the upstream packet in the line between the splitter 3 and the OLT 1 is prevented.

  An ONU (Optical Network Unit) 2 is a terminating device on the subscriber side of an optical fiber. The ONU 2 includes a PON termination unit 311, a signal multiplexing unit (MUX) 411, Ethernet interface units 511-1 to 511-n1, and TDM interface units 611-1 to 611-n2. The ONU 2 is connected to the data communication terminals 2110-1 to 2110-n 1 and the TDM terminals 2111-1 to 211-n 2 via the Ethernet interface unit 511 and the TDM interface unit 611. A plurality of Ethernet interfaces 511 and TDM interfaces 611 can be connected. The functions performed by the PON terminator 311 include optical-electric conversion for converting an optical signal transmitted from the OLT 1 into an electrical signal, and an Ethernet frame when data is transmitted to the ONU 2 subscriber side (UNI: User Network Interface). Alternatively, mutual conversion between TDM data and a data format used for communication control in the PON section, bandwidth control for downlink data distribution, and generation of an uplink transmission frame in accordance with a transmission timing instruction of OLT 1 are included. The L2SW (multiplexing unit) 411 operates in the same manner as the L2SW 130 of the OLT.

  The L2SW 130 transfers the signal received from the PON interface 200 to either the Ethernet interface 110 or the TDM interface 120 in accordance with the destination information of the signal given to the L2 frame. Further, the data received from the Ethernet interface 110 or the TDM interface 120 is transferred to the PON interface 200 serving as the respective destination. Multiplexing of Ethernet data and TDM data is performed in the PON interface 200. The function of this L2SW 130 is also the same in the ONU 2, and the signal from the PON interface 311 is distributed to the Ethernet / TDM interface (511/611), and the signal from the Ethernet / TDM interface (511/611) is sent to the PON interface 311. Forward.

  FIG. 3 shows functional blocks of the PON interface unit (200, 311) in the OLT 1 and the ONU 2 of FIG. In particular, it is a diagram for explaining functions related to bandwidth control in the PON section.

  The PON interface unit 200 of the OLT 1 is connected to the access network side (SNI: Service Network Interface) provided with the Ethernet interface 110 and the TDM interface 120 of the OLT 1, respectively for downstream communication (for subscriber terminals) and upstream communication (for access network). Ethernet frame processing unit 210 corresponding to the same, TDM processing unit 220 that performs upstream and downstream TDM data communication processing, PON termination unit 230 that interconnects communication control in the PON section and Ethernet or TDM communication control in the external network, An optical module 240, a CPU 250, and a communication that put a signal on an optical fiber after generation of a downstream frame in the PON termination unit 230, and convert the optical signal into an electrical signal and transmit it to the PON termination unit 230 when receiving an upstream signal through the optical fiber control A memory 260 is provided for data management and program retention. The memory 260 can also hold information such as frame analysis results and bandwidth control status.

  Data input through the SNI side line 201 is temporarily stored in a data queue 212 provided in the Ethernet frame processing unit 210. The accumulated data is read by an instruction from the queue control unit 211 and reconfigured into a downstream frame for PON section communication by the PON termination unit 230. The queue control unit 211 reads a frame held in the data queue 212 in accordance with an instruction from the PON termination unit 230.

  Similar to the Ethernet frame processing unit 210, the TDM processing unit 220 also includes processing blocks for upstream communication and downstream communication. The data received through the TDM line 202 is temporarily held in a buffer provided in the TDM processing unit 220 and then transferred to the PON termination unit 230 for the downlink frame configuration. Since TDM is a transfer method using a synchronous multiplex frame, transmission delay tolerance conditions are stricter than those of Ethernet, and data received by the TDM line 202 at a constant cycle is sent to the PON termination unit 230 at the same rate. The data transmission / reception cycle in the TDM line is a 125 microsecond cycle in the case of SDH (Synchronized Digital Hierarchy), and the periodic transmission / reception control in the PON section is performed in units of 125 microseconds in the standardization recommendation of G-PON (non-patent document (See “G-PON Recommendation”).

  The PON termination unit 230 generates a downstream frame to be transmitted to the PON section (NNI) from the reception data stored in the Ethernet frame processing unit 210 and the TDM processing unit 220. In the PON section, frame generation is periodically performed according to communication control using TDMA. In G-PON, downstream and upstream frames are transmitted and received at a period of 125 microseconds. This frame is hereinafter referred to as a basic period and a basic period frame. Data stored in the Ethernet frame processing unit 210 and the TDM processing unit 220 is reconfigured in this basic periodic frame format. In the basic period frame, data addressed to a plurality of ONUs 2 (subscribers or subscriber terminals) are multiplexed, and an identifier indicating the destination ONU 2 is inserted together with the data. The format of the basic periodic frame will be described later.

  In the PON termination unit 230, the upstream frame analysis unit 231 determines a transfer destination Ethernet port or TDM port of a frame transmitted in the upstream direction. Further, the traffic situation included in the upstream frame, that is, the transmission waiting data accumulation situation in the upstream frame transmission queue provided in the ONU 2 is extracted. This information is held in the memory 260 as band request information 263. This bandwidth request is used for communication bandwidth allocation from the OLT 1 to the ONU 2. The data transmission timing in the upstream direction in the PON section is in accordance with the data transmission permission given to the ONU 2 by the OLT 1. The ONU 2 sends out the designated data amount at the designated timing in accordance with the transmission schedule set so that the transmission data does not overlap after multiplexing by the splitter. As a result, the OLT 1 can identify the transmission source of each frame.

  The memory 260 includes a pointer calculator 261 and a bandwidth calculator 262. The bandwidth calculation unit 262 calculates a bandwidth to be allocated to each ONU 2 in the next basic period based on the bandwidth request information 263 extracted from the uplink frame. The allocated bandwidth calculated here is held in the variable bandwidth allocation table 265. The variable bandwidth refers to a bandwidth that is dynamically allocated to traffic that is transmitted / received by an Ethernet frame and whose transmission timing is arbitrary and whose transmission rate varies depending on the use state of network resources. DBA is a dynamic bandwidth allocation method based on bandwidth requirements, and is intended for variable bandwidth control. The memory 260 also holds a fixed bandwidth allocation table 264. This table holds the allocated amount of the synchronous multiplex communication band in a circuit switching network such as a telephone network.

  Since the bandwidth required for communication is constant from the start to the end of the session, the bandwidth allocation amount to the ONU does not fluctuate. However, as a case where the usage status of the fixed band changes, there may be a case where the number of channels set in advance in the synchronous multiplex communication line is changed by OpS (Operations System). Since the fixed band allocation table 264 is referred to by the downstream frame generation unit 232 and the band calculation unit 262 of the PON termination unit 230, the fixed band allocation table 264 holds the fixed band usage state set semi-fixed by OpS.

  The pointer calculation unit 261 in the memory 260 calculates a variable bandwidth transmission schedule when performing bandwidth allocation by DBA. This function operates when a band indication field (described later) in a downstream frame is generated in the downstream frame generation 232 in the PON termination unit 230. The pointer calculator 261 is necessary for variable bandwidth allocation. First, a communication band (fixed band) for a synchronous multiplex frame whose allocation band size and transmission timing are fixedly allocated is allocated based on the fixed band allocation table 264.

  Next, the allocation amount for each bandwidth setting unit is read from the variable bandwidth allocation table 265, and for each table entry (bandwidth setting unit), the free bandwidth after the transmission timing allocation processing for the fixed bandwidth and the preceding variable bandwidth entry (empty transmission timing, Specify an empty transmission position. At this time, the pointer calculation unit 261 manages the transmission timing allocation status to the upstream frame, and gives a start pointer or a start and end pointer indicating an empty band on the upstream frame.

  The ONU 2 includes an optical module 340 that terminates an optical fiber, a PON terminator 330, a memory 350, an Ethernet line terminator 310 that accommodates the Ethernet line 301, and a TDM line terminator 320 that accommodates the TDM line 302.

  The Ethernet line termination unit 310 extracts an Ethernet frame from a signal input via the Ethernet line 301 and notifies the PON termination unit 330 of the Ethernet frame. The Ethernet frame extracted by the Ethernet line termination unit 310 is stored in the data queue 352 of the memory 350. The data queue 352 is managed by the queue control unit 351, and is read according to an instruction notified from the upstream frame generation unit 332 of the PON termination unit 330 to the memory 350. Further, the Ethernet frame reconstructed from the downlink frame received by the optical module 340 is stored in the data queue (transmission queue) for the downlink Ethernet frame provided in the data queue 352 of the memory 350. The downlink queue control unit in the queue control unit 351 sequentially transfers frames from the data queue to the Ethernet line termination unit 310 in accordance with a read instruction from the Ethernet line termination unit 310.

  Similar to the TDM line termination unit 220 of the OLT 1, the TDM line termination unit 320 extracts TDM data transmitted by a certain amount at a certain period. Here, the information extracted by the TDM line termination unit 320 includes TDM data transmission cycle information, user data, and TDM channel information used in the data. The received TDM data is temporarily stored in a buffer, and is read from the buffer and transferred to the PON termination unit 330 at a constant rate in order to generate an upstream frame by the PON control unit 330.

  The ONU 2 shows a configuration in which the Ethernet and the TDM data transmission queue 352 are provided separately from the line termination unit (310/320). The data queue 352 may be provided in the line termination units 310 and 320. If the line termination units 310 and 320 and the main signal transfer path are secured, the function of the PON-IF 300 is not affected. The PON-IF is a set of a series of functional blocks configured on the ASIC, and any configuration may be adopted as long as the configuration described above can be performed.

  The downstream frame analysis unit 331 of the PON termination unit 330 extracts Ethernet and TDM data from the downstream PON section communication frame stored in the downstream frame buffer 333, and reconfigures the data into a format that can be transmitted from the line termination units 310 and 320. . Data frame processing after reconfiguration is as described above. The downlink frame analysis unit 331 also extracts device control information and band allocation information notified from the OLT 1.

  The device control information is processed by a CPU connected outside or inside the device. Band allocation to the upstream frame (transmission permission for each ONU 2) information is held in the band allocation information database 334 provided in the PON termination unit 330. This database is referred to by the upstream frame generation unit 332, and the transmission data amount (bandwidth allocation size) in the upstream frame is used in conjunction with the queue control unit 351 to control the read amount of the data queue 352.

  The bandwidth control in the PON section is divided into those for the upstream frame and those for the downstream frame. In the downstream direction, a frame input to the OLT 1 through the Ethernet or the TDM interfaces 110 and 120 is replaced with a basic periodic frame (125 microsecond periodic frame) for PON section communication in the downstream frame generation unit 232 of the PON termination unit 230. Here, bandwidth control is performed when performing data read control from the data queue 212 provided in the Ethernet frame processing unit 210 and the data queue provided in the TDM processing unit 220 at the time of frame generation.

  For example, the data is distributed to one or a plurality of queues, and the downlink communication band is controlled by the read priority set for each queue. In the ONU 2, the downstream frame analysis unit 331 performs bandwidth control when extracting the Ethernet frame or the TDM frame from the PON section communication frame and then performing the read control of the frames stored in the data queues of the line termination units 310 and 320. . Here, when the downlink PON frame is generated, the reading order of the data queues provided in the line termination units 310 and 320 can be arbitrarily set. In order to secure TDM communication quality, a method of preferentially allocating a transmission band required for TDM data to a frame is also possible. In addition to this, the reading order of the data queue can be arbitrarily set.

  The bandwidth control for the upstream frame is based on the upstream data queue 352 read control controlled by the upstream frame generation unit 332 in the ONU 2 and the data queue read control in the line termination units 210 and 220 in the OLT 1. In the bandwidth control for the downstream frame, it is determined by the received data type (Ethernet or TDM) and the read priority of the queue to which the received data is distributed. The uplink frame generation unit 332 generates a frame by reading the transmittable data from the uplink data queue according to the data transmission amount allocated for each uplink frame transmission period held in the band allocation information database 334.

  Band control is performed for each band allocation unit (hereinafter referred to as Alloc-ID) set for each ONU 2 or one or more. Therefore, both the fixed bandwidth allocation table 264 and the variable bandwidth allocation table 265 hold entries in which the bandwidth allocation amount for each Alloc-ID is set.

In addition, the downlink and uplink frames generate small frames for each of a plurality of Alloc-IDs, and combine (multiplex) them to generate a basic period frame of the PON section. Therefore, regarding the transmission bandwidth control in the PON section, it is desirable that the transmission bandwidth control in the PON-IF 200 on the OLT 1 side performs data queue read control in units of Alloc-ID.

  Of course, it is also possible to assign a plurality of Alloc-IDs having the same read priority to one data queue. Similarly, in upstream frame transmission control in the PON-IF 300 of the ONU 2, transmission control is performed from frame generation by setting a data queue for each Alloc-ID unit or by sharing a plurality of Alloc-IDs having the same priority. It is also possible to perform consistent bandwidth control.

  It is also possible to set the priorities for each data queue to be referred to after frame generation to be equal, and to operate the DBA calculation so as to reflect the actual bandwidth utilization rate without being influenced by other factors.

  FIG. 4 is a sequence diagram for explaining the relationship between the basic operation of the DBA and the control timings of the fixed band and the variable band when the present invention is applied. An operation when the OLT 1 performs bandwidth allocation of an upstream frame to the ONU 2 will be described.

  The OLT 1 instructs the transmission band and timing to the subordinate ONU 2 using the band indication field of the downstream frame. In FIG. 4, this corresponds to the transmission instruction 401 in the downstream frame #i. This frame is determined based on the transmission waiting data amount of each ONU 2 acquired by the OLT 1 in the upstream frame preceding this. The downstream frame 401 may include a queue state notification instruction from the OLT 1 to the subordinate ONU 2 in addition to the transmission instruction. Although the timing of this queue status transmission notification depends on the bandwidth allocation cycle of the OLT 1, the OLT 1 receives the queue status notification (transmission bandwidth request) from each ONU 2 at least once within the bandwidth allocation cycle.

  In response to the downstream frame 401, the ONU 2 transmits the upstream frame after a total value 420 of EqD (Equalization Delay) 421 and a time (BWstart) 422 to the transmission start time with reference thereto. Here, EqD 421 is a transmission waiting time designated to multiplex uplink frames from all ONUs 2 by TDMA on an optical fiber when OLT 1 has a plurality of ONUs 2 under its control. Normally, the frame arrival timing from ONU2 varies because the distance from OLT1 differs for each ONU2, but the upstream frame from ONU2 with a different distance is multiplexed after it passes through the splitter (when it is received at OLT1). Timing reference points must be matched.

  By measuring the distance for each ONU 2, the round-trip time from when the downstream frame is transmitted from the OLT 1 until the OLT 1 receives the upstream frame is measured, and the time until the upstream frame arrives from each ONU 2 in accordance with the ONU 2 with the longest delay. To decide. The signal processing time excluding the delay due to optical fiber transmission delay and O / E / E / O conversion for each ONU 2 from the common required time until the arrival of the response frame is held in the ONU 2 as EqD421. BWstart is a timing at which the ONU starts data transmission, and is a parameter indicating the elapsed time from the reference point for uplink frame transmission, which is designated by EqD. This parameter is expressed in units of bytes, for example, and is notified in a frame 401 from the OLT 1 to the ONU 2.

  When a queue state notification instruction is issued in the downstream frame 401, the transmission waiting data amount is notified in the upstream frame 402.

Thereafter, the queue state notification is received by the upstream frame, and the flow of performing the bandwidth allocation calculated based on the transmission waiting data amount in the next downstream frame is repeated. In the case where these processes are performed every 125 microseconds in the basic period of the PON, when OLT1 is used as a reference, the control period of the corresponding upstream frame and downstream frame is generated at intervals of EqD421, and the upstream frame OLT corresponding to each downstream frame is generated. The arrival time is delayed by a time including a signal transmission time in the PON section, a processing time required for generating an upstream frame inside the ONU, and EqD. Therefore, in a PON section, instructions (downstream frames) from a plurality of OLTs 1 are accumulated at a certain time, and responses (upstream frames) from the ONUs 2 are generated with a delay of a certain period.

  The fixed bandwidth allocation cycle and the variable bandwidth allocation cycle need not be set equal. The fixed bandwidth allocation cycle depends on the TDM data sampling cycle setting in the TDM processing unit 220 in the PON-IF 200 and the TDM processing unit 320 in the PON-IF 300. It is not necessary to allocate bandwidth to all TDM communication channels in units of 125 microseconds, and it is only necessary to be able to allocate a fixed bandwidth at a fixed cycle. Can be set.

  The variable band is allocated so as not to overlap with the fixed band transmission position allocated to the upstream frame. Therefore, it is only necessary to know the fixed bandwidth allocation status in the target uplink frame at the time of variable bandwidth allocation, and the variable bandwidth allocation cycle may be set in any manner.

  This is a method realized by separating the table and dividing and managing the bandwidth on the line. Since the fixed bandwidth is assigned to the position according to the setting of OpS, the generation of jitter can be suppressed, and only the variable bandwidth is handled by the bandwidth calculation unit, so that load is placed on processing that is virtually unnecessary, such as priority processing for fixed bandwidth data and allocation location calculation. Therefore, communication quality is stabilized and processing efficiency is improved.

  FIG. 4 shows the bandwidth allocation timing when 125 microseconds is used as the fixed bandwidth allocation cycle 440 and m times the 125 microsecond frame (fixed bandwidth allocation cycle 440) as the variable bandwidth allocation cycle 450. At this time, the fixed communication band is fixedly band-assigned (transmission permitted) by the immediately preceding downlink frame for each uplink frame based on the channel setting status held in the fixed band allocation table. Sets the transmission bandwidth only once in the variable bandwidth allocation period 450.

  That is, for the variable communication band, the amount of data that can be transmitted within the bandwidth allocation period is calculated from the amount of data waiting for transmission notified from each ONU 2. Here, the bandwidth allocation cycle refers to the update cycle of the variable bandwidth allocation table 265. Since the bandwidth set in the variable bandwidth allocation table 265 may be used up in the table update cycle, a plurality of implementations can be considered as the allocation method. One is a method of sequentially allocating all possible transmission bands for each entry (Alloc-ID) described in the variable band allocation table 265 as a series of (large) bands, and the other is a method of allocating to a specific Aloc-ID. In this method, a bandwidth is divided and assigned to a plurality of upstream frames within the periphery of the variable bandwidth allocation table 265 update. These methods will be described later.

  5 to 7 are flowcharts for explaining the bandwidth allocation processing in the present invention.

  FIG. 5 is a flowchart of uplink frame reception processing according to the embodiment of this invention, and is executed by OLT 1. In order to explain a series of processing related to bandwidth control, this flowchart shows a processing procedure when the OLT 1 receives a frame including upstream transmission waiting data amount information of the ONU.

  In the PON termination unit 230 of the OLT 1, when receiving the upstream frame, the upstream frame analysis unit 231 extracts the timing at which the upstream frame is received (S101). The frame reception timing is used to adjust EqD421. The data transmission amount and data transmission start timing instructed to each ONU 2 by the OLT 1 are held in the variable bandwidth allocation status table 265 in the OLT 1 and it is confirmed whether or not the data matches that of the received frame. (S102).

  When the intended transmission timing of the ONU 2 and the actual uplink frame reception position do not match (the difference exceeds a certain threshold), the transmission timing of the ONU 2 is corrected by resetting the EqD 421 (S103). If the transmission position is correct (the difference from the intended transmission timing of the ONU 2 is within a certain threshold value), and if the header analysis of the frame is possible after position correction in step S104, it is included in the header The amount of untransmitted data stored in the ONU 2 queue is extracted (S105). The extracted untransmitted data amount is held in the band request information 263 together with the corresponding band control ID (Alloc-ID) (S106).

  FIG. 6 is a flowchart showing the setting process of the variable bandwidth allocation table 265 in the present invention. This is executed by the bandwidth calculation unit 262 of the OLT 1 every variable bandwidth allocation cycle (variable bandwidth allocation table update cycle). As described above, the bandwidth allocation period may be a period of one uplink frame, or may be a period of a multiframe obtained by collecting a plurality of uplink frames.

  First, the bandwidth calculation unit 262 refers to the fixed bandwidth allocation table 264 (S201), and acquires the fixed bandwidth allocation status in the uplink frame that is the bandwidth setting target (S202). Here, when the update period of the fixed band allocation table and the update period of the variable band allocation table are different from each other as described above, the total bandwidth that can be used for variable band communication is acquired in the uplink frame transmission period to be controlled. Therefore, the fixed band allocation status is acquired for all uplink frames included in the period. Next, the newly received ONU2 transmission queue information is read from the bandwidth request information 263 (S203).

  The bandwidth request information 263 stores requested bandwidth information for each bandwidth allocation unit Alloc-ID to the ONU 2. Based on the acquisition result of the fixed bandwidth status, the bandwidth that is allowed to be transmitted until the next variable bandwidth allocation table update is calculated for each Alloc-ID (S204), and the calculated variable bandwidth allocation amount is entered in the variable bandwidth allocation table. (S205). In step S204, the bandwidth calculation unit 232 can calculate the variable bandwidth allocation amount for each bandwidth control ID by reflecting the control policy set for each Alloc-ID in addition to the bandwidth request information. As the control policy, it is conceivable that the bandwidth control IDs of the variable bandwidth are treated equally, or the priority is determined for each bandwidth control ID and the bandwidth is allocated non-uniformly based on the priority.

  FIG. 7 is a flowchart of bandwidth permission information allocation processing to an upstream frame in the embodiment of the present invention. Band allocation is performed at a basic period (125 microsecond frame) as shown in the description of the sequence of FIG.

  In the PON termination unit 230 of the OLT 1, the downlink frame generation unit 232 reads the fixed band allocation table 264 held in the memory 260. This table holds the band allocation size and allocation start position for each Alloc-ID. First, the fixed band transmission position is set according to the read band transmission amount and transmission timing (pointer). Specifically, the information is entered in the bandwidth notification field of the downstream frame.

Next, it is determined whether the DBA cycle (variable bandwidth allocation table update cycle) is continuous with the bandwidth allocation processing for the upstream frame prior to this (S303). Here, if the DBA cycle has been continued from the previous frame, the DBA cycle does not coincide with the fixed bandwidth allocation cycle, and the bandwidth allocation of the specific entry in the table is performed before the allocation of a large bandwidth. There can be situations where assignments to frames and ongoing operations occur. In order to perform bandwidth allocation correctly, it is checked here whether it is a boundary point of the DBA cycle. If it is not continuing, that is, if there is no Alloc-ID to which no bandwidth is allocated within the DBA cycle, the processing is terminated as it is.

  Next, as described above, it is determined whether there is a band being allocated across the frames (S304). For this determination, an allocation status flag may be defined in the variable bandwidth allocation table, or a register that temporarily records the Alloc-ID entry being allocated may be used. If there is an entry being allocated, the remaining bandwidth of the entry is read from the variable bandwidth allocation table 265 or the register (S306). If there is no assigned entry, an unassigned entry is newly read (S305).

  It is determined whether or not the read bandwidth size is smaller than the remaining available area on the uplink frame (all can be allocated on the uplink frame) (S307). When all the bands cannot be allocated, the size that can be allocated on the frame is extracted (S308), and the remaining is recorded in the table or in an unallocated register (S309).

  When all the bands can be allocated, or after the band division process is completed, the transmission start position is calculated from the empty band status of the upstream frame (S310), and the band is allocated (S311). In the band allocation process, as in the above-described fixed band allocation process, a description of the band instruction is added using the transmission start position, the transmission data amount, or the transmission end position in the band instruction field of the downlink frame.

  Finally, it is confirmed whether or not the allocation has been completed for all entries described in the variable bandwidth allocation table (S312). If there is an unallocated entry in the same DBA cycle, the processing from step S303 is performed. When all allocation processing is completed at the time of step S312, the variable bandwidth allocation processing in the DBA cycle is terminated.

  8A and 8B are explanatory diagrams of the fixed bandwidth allocation table 264 in the hierarchical bandwidth control method of the present invention.

  The fixed band data is allocated by the same amount at the same position for each frame based on the fixed band allocation table. For this reason, this table reflects the setting conditions of communication channels used for synchronous multiplex communication such as E1 and T1 lines connected to the TDM line terminator of the PON system, and is normally used semi-fixed. The fixed bandwidth allocation table can be implemented in two ways as shown in FIGS. 8A and 8B, depending on the combination of information held therein.

  The fixed band allocation table shown in FIG. 8A stores the allocation position of fixed band data determined by the band allocation amount and the allocation start position. This table includes a bandwidth control ID (Alloc-ID) 801, a bandwidth allocation amount 802, and an allocation start position 803. A bandwidth control ID (Alloc-ID) 801 is a basic unit of bandwidth control in the PON section, and can be associated with a service ID or a user ID. However, as a feature of fixed band communication, the number of channels between OLT1 and ONU2 is semi-fixed, and it is not a property that requires band control for each channel. Therefore, an Alloc-ID corresponding to TDM data is set for each ONU2. A method of assigning a fixed communication band in which one channel is set and the total number of all channels is assigned to each ONU 2 is also possible.

  The bandwidth allocation amount 802 is a bandwidth allocated to the data of the Alloc-ID, and is a data amount permitting transmission in a slot sandwiched between an allocation start position and an allocation end position, which will be described later. The allocation start position 803 is a position where allocation of data of the bandwidth control ID starts in the uplink cycle frame, and is expressed by the number of bytes from the payload start position of the uplink frame in this embodiment. The allocation start position 803 and the band allocation 802 determine the transmission timing in the uplink frame of the data of the band control ID. Since the fixed band data must have a fixed transmission timing within each frame transmission period, for example, if the transmission start position 803 is fixedly set in the band allocation table 264, the processing load at the time of band setting can be reduced. .

  FIG. 8B shows another embodiment of the fixed bandwidth allocation table 264. In the fixed band allocation table 264 of FIG. 8B, the allocation position of the fixed band data is determined by the allocation start position 803 and the allocation end position 804. The allocation end position 804 is a position where the allocation of the data of the band control ID ends in the uplink cycle frame, and is expressed by the number of bytes from the start position of the uplink frame in this embodiment. The allocation start position 803 and the allocation end position 804 determine the transmittable bandwidth (data amount) allocated to the Alloc-ID.

  FIG. 9 is an example of the variable bandwidth allocation table 265. The variable band data is allocated to an area that is free after the fixed band data is allocated. Furthermore, the allocation size of the variable bandwidth data is changed every DBA cycle (variable bandwidth allocation table update cycle), and when performing variable bandwidth allocation for a plurality of Alloc-IDs continuously, In some cases, the transmission permission size is also affected.

  Therefore, in order to set information regarding the variable band allocation start and end positions in the variable band allocation table 265 in advance, the band calculation unit 262 refers to the band request information 263 and calculates the allocated band at the same time. The band allocation position of the fixed band held in the table 264 must also be considered. Here, only the bandwidth allocation amount is set in the variable bandwidth allocation table 265 in order to reduce the load of the DBA processing and to divide the functions of the bandwidth calculation unit 262 and the downlink frame generation unit 231 to improve the processing efficiency. When the bandwidth allocation field is generated by the downlink frame generation unit 231, the bandwidth allocation position is calculated by the pointer calculation unit 261 from the previous bandwidth allocation status and the transmission permitted bandwidth defined in the variable bandwidth allocation table 265. And assign.

  The variable bandwidth allocation table 265 includes a bandwidth control ID (Alloc-ID) 901 and an allocated bandwidth 902. Further, a configuration including other flags 903 is also possible. The bandwidth allocation amount 902 is a bandwidth size allocated to the bandwidth controlled by the Alloc-ID, and is calculated by the bandwidth calculator 262 based on the bandwidth request information database 263. Note that, depending on the amount of bandwidth that can be transmitted in the entire uplink frame targeted by the DBA and the queue status indicated by the bandwidth request information 263, it is not always possible to assign a bandwidth that can be transmitted to all of the transmission-waiting data.

  Further, the amount of upstream transmission waiting data notified from the ONU 2 does not necessarily need to be notified for each Alloc-ID, and among the Alloc-IDs corresponding to the variable bandwidth data, for example, the minimum bandwidth guarantee is collected. You may receive and hold. Therefore, when a band is allocated to each Alloc-ID, a means for dividing a band that can be transmitted in an uplink frame after referring to a plurality of conditions is required. In the present invention, although details of the algorithm cannot be reached, a queue information collection unit, a bandwidth allocation unit, and bandwidth mapping information to an upstream frame must be associated with each other in the apparatus.

  This table defines the total amount of data to be transmitted in the DBA cycle. When bandwidth allocation over the basic period frame occurs, that is, when the bandwidth allocation does not fit in one frame, an external register for recording the remaining bandwidth allocation and a flag indicating whether transmission is completed or not included in the table field 903 are provided. It can respond by using.

  FIG. 10 shows another configuration example of the variable bandwidth allocation table 265. This table includes an Alloc-ID 901, an allocated bandwidth 902, and an unallocated bandwidth 1001.

  The unallocated bandwidth 1001 is a flow controlled by the Alloc-ID and indicates the remaining bandwidth that has not yet been allocated among the bandwidths to be transmitted within the DBA cycle. As a situation in which this field is used, when a large variable bandwidth is allocated across the basic period frame, and another Alloc-ID bandwidth allocation prior to the allocation of the Alloc-ID, a bandwidth that can be transmitted in an upstream frame is consumed. A case where a part of the allocation of the Alloc-ID spans the next basic period frame is conceivable. This is a method of recording the unallocated bandwidth in the variable bandwidth allocation table 265 in the case of the frame crossing allocation described in the explanation of FIG.

  In addition, it is possible to specify the maximum bandwidth 1002 that can be allocated for each basic periodic frame for Alloc-ID. In the present embodiment, the bandwidth allocation amount 902 in the DBA cycle specified for each Alloc-ID represents a bandwidth size that has not yet been allocated within the cycle. That is, it is the amount of data allocated to the subsequent frames among the data transmitted with the Alloc-ID.

  FIG. 11 is an explanatory diagram of the bandwidth request information 263 according to the embodiment of this invention.

  The bandwidth request information 263 is created when the packet accumulation status is received from the ONU 2. This information is referred to when the bandwidth calculation unit 262 determines a time slot (band allocation timing and size for each Alloc-ID) to be allocated to the upstream frame in the next cycle.

  The bandwidth request information 263 includes a bandwidth control ID (Alloc-ID) 1101 and an accumulated data amount 1102.

  The bandwidth control ID 1101 is an identifier for identifying a service or a user, and is a bandwidth control unit in the PON section. In the present embodiment, an allocation ID (Alloc-ID) is used as the bandwidth control ID 1101, but since the Alloc-ID is set in association with the ONU number or the queue number, it can be regarded as an identifier thereof. Each entry can also be configured using a bandwidth control ID (bandwidth management unit) converted from Alloc-ID included in the received frame to these other identifiers. The accumulated data amount 1102 is the amount of untransmitted data accumulated in the transmission queue managed by the bandwidth control ID 1101 for the ONU 2.

  A band control method 1103 indicating whether the data corresponding to each Alloc-ID transmitted from the ONU 2 is fixed band communication data or variable band communication data may be added to the table. Actually, in the case of fixed band communication data, the channel to be used in the PON section is actually determined based on the static setting by OpS, so there is no need to dynamically manage the queue status.

  However, for example, depending on the Alloc-ID, a fixedly allocated bandwidth amount for setting the minimum guaranteed bandwidth and a best effort bandwidth for improving transmission efficiency when there is a free bandwidth are allocated, and a bandwidth is determined by a combination thereof. In the case of control, etc., by referring to this parameter, it is possible to identify the Alloc-ID to be preferentially assigned and its bandwidth and to perform bandwidth control in detail.

A bandwidth allocation priority flag for reference during bandwidth calculation may be attached to each entry. This parameter is an implementation example of the parameter included in the other parameter 1104 of the table. This is used when priority needs to be set between the variable band communication data and between the fixed band communication data when the guaranteed band is allocated. The priority may be determined according to the type of communication traffic (that is, service or application) or the contract contents of the user. In this case, the bandwidth allocation priority flag is determined in advance based on a contract with the user.

  FIG. 12 shows a configuration of a downstream frame transmitted from the OLT 1 to the ONU 2 in order to notify bandwidth allocation information to the upstream frame. In the figure, description will be made on the assumption that the OLT 1 is arranged on the right and the ONU 2 is arranged on the left.

  Through communication using TDMA, a frame is periodically transmitted in units of 1201 basic frame periods (for example, 125 microseconds). In the uppermost stage of FIG. 12, the header portion 1210 and the payload portion 1220 of the downstream frame repeatedly appear toward the ONU 2 to show the state.

  The header section 1210 includes a Psync field 1211 for storing a specific signal pattern for frame synchronization on the receiving side (that is, the ONU 2 side), and a band information field 1230 for notifying each ONU 2 of bandwidth allocation information for an upstream frame. The ONU control information field 1213 for notifying control information such as activation and deactivation of each ONU 2 and other frame information for reference on the receiving side include the presence / absence of FEC processing for the frame, the frame counter, BIP, and header length. A frame information field 1212 is included. The frame information field 1212 and the ONU control information field 1213 may be rewritten or deleted as necessary.

  The bandwidth information field 1230 includes bandwidth control IDs (Alloc-IDs) 1231-1 to 1231-fN, 1232-1 to 1232-vN, and transmission start positions 1232-i (i = 1 to fN, 1 to vN), a transmission end position 1233, and a band control information field 1234 including whether or not a queue state notification instruction is necessary and whether or not FEC is used in an upstream frame for each Alloc-ID. The bandwidth information field 1230 includes bandwidth allocation information for all Alloc-IDs that allow transmission at the timing indicated by the downlink frame. For example, even when the payload portion contains only data addressed to a specific Alloc-ID (ONU2), the bandwidth control unit 1230 of the header 1210 is permitted to transmit data on the same upstream frame based on the DBA mechanism. The bandwidth allocation information for all Alloc-IDs to be notified is notified.

  In the present embodiment, the case where the fixed communication band notification area 1202 and the variable data transmission band notification area 1203 are separated with respect to the band information has been described, but the band notification order for each Alloc-ID is not particularly in this order. Good. In particular, when guaranteeing the minimum bandwidth, there may be a case where the transmission bandwidth is instructed to the Alloc-ID in a form in which a fixed bandwidth and a variable bandwidth are mixed. However, practically, it is convenient to process on a first-come-first-served basis, and therefore data using a fixed channel such as a telephone can be arranged in front of the band information field 1230.

  Further, as shown in the explanation of the DBA basic sequence, it is not always necessary to update the fixed bandwidth allocation table 264 every basic frame period 1201 with respect to traffic using a fixed channel such as a telephone. The fixed bandwidth allocation table 264 may be updated as a cycle.

  FIG. 13 shows a data allocation state in the uplink frame. The upper part of FIG. 13 shows the downstream frame of the PON section, and the left side of the figure is ONU2 and the right side is OLT1. The downstream frame header 1210, payload 1220, and basic frame period 1201 are the same as those in FIG. The header of the downstream frame includes a band control information field 1230 as shown in FIG.

  When receiving a downstream frame, the ONU 2 transmits data according to a time slot designation with a reference point after a predetermined delay time EqD (Equalization Delay) 1310 as described in the DBA sequence. The lower part of the figure shows the uplink frame transmission status. Here, in order to explain individual frame transmission timings, a data multiplexing state to an upstream frame when data from a plurality of ONUs 2 (Alloc-ID) is multiplexed by the splitter and then received by the OLT 1 is shown. Frame #i 1303-i shows a situation in which the frames transmitted from the respective ONUs 2 are multiplexed with respect to the downstream frame at the uppermost right end.

  The upstream frame includes fixed band data 1301 and variable band data 1302. Assuming that an SDH network is accommodated, the same amount of fixed band data is included at the same position in each frame unless the setting of the fixed band communication channel is changed by OpS. That is, the OLT 1 of the present embodiment allocates the same amount of fixed band data to the same position between a plurality of frames. Therefore, the position of the fixed band data does not change for each frame, and the transmission period of the fixed band data is constant.

  On the other hand, the allocation of variable bandwidth data may change from frame to frame. This is because the variable bandwidth data that needs to be allocated changes every basic frame period depending on the traffic situation that changes every moment. The OLT 1 according to the present embodiment allocates variable band data to a position where no fixed band data is allocated.

  The lowermost part of FIG. 13 shows an enlarged view of an individual frame. The frame is composed of a header part 1321 including identification information for identifying traffic (flow) carried by the frame, and a data part 1322 on which actually carried data is placed. Data and a header are provided for each bandwidth control ID, but in some cases, a plurality of flow identifiers may be used for each Alloc-ID. In that case, a plurality of individual frames are included in the band allocated to one Alloc-ID.

  In FIG. 13, the band-fixed data area is provided on the head side of the frame, but the band-fixed data area is not necessarily provided on the head side of the frame. Further, although one band fixed data area and one band variable data area are provided, a plurality of each may be provided.

  FIG. 14 is a diagram for explaining a frame multiplexing method on a fiber when an upstream frame is transmitted from ONU 2 to OLT 1. A situation in which a frame is transmitted from the left side of the figure to the OLT 1 on the right side of the figure is shown. Note that FIG. 14 shows an example of a frame arrangement state in which the right side of the figure is the earliest transmitted data and the transmission time from the ONU 2 is delayed toward the left side. A dotted line indicates a basic frame period (for example, 125 microseconds).

  Each frame transmitted from the ONU 2 passes through the splitter 3 and is multiplexed on one fiber. In the figure, 1401-1 to 1401-n represent transmission positions and sizes of fixed band communication data transmitted from ONU2 # 1 to ONU2 # n, respectively. Data 1401-1 to 140n distributed to a plurality of fibers before passing through the splitter are multiplexed after passing through the splitter. Frames 1402 to 1407 indicate variable bandwidth data transmitted from each ONU 2. The variable band data is inserted by the DBA mechanism so as not to overlap with the fixed band data when multiplexed.

FIG. 15 is a diagram illustrating fixed band communication data generation timing in the ONU 2 when TDM data received by the TDM-IF is transmitted on the fixed communication channel and transmitted to the PON section. This drawing is based on the assumption that the fixed-band communication band allocation period (that is, fixed-band allocation table update period) is the basic frame period. In principle, the sampling period is shortened.

  The data received through each fixed band communication channel by the TDM-IF has the same data reception periods 1501-1 to 1501-3 as shown in the figure, but the reception timing itself is dispersed.

  In the ONU 2, the amount of data to be transmitted in one cycle of the uplink frame transmission cycle is temporarily stored in the buffer, and this is transmitted on the uplink frame at a fixed bandwidth allocation table update cycle interval. Here, 1510-1 is transmitted to 1520-1, 1510-2 is transmitted to 1520-2, and 1510-3 is transmitted to 1520-3 with different timings. It should be noted that the same processing is performed in the OLT 1 when TDM data received from the SNI side is loaded in a downstream frame and transmitted to the PON section.

  A change in the queue state when the present invention is applied will be described with reference to FIGS. The operation follows the sequence of FIG.

  In FIG. 16, a plurality of ONUs 2 (# 1 to # 3) are connected to the OLT 1, and terminal devices 21 to 23 and telephone devices 31 to 33 are connected to each ONU 2, respectively. The SLT side of the OLT 1 is connected to an Ethernet network 1100 for data communication and a TDM network 1200 including a telephone network.

  Further, OpS5000 is connected to the OLT 1 via the Ethernet network, the TDM network, or directly as a control management terminal in the PON section. In addition, a setting state of a communication session used in the uplink direction is schematically shown.

  One fixed band communication session 1610-1 to 1610-3 is set for each ONU 2 from the OLT 1. This fixed band communication session is identified in the PON section by Alloc-ID # f1 to Alloc-ID # f3, which are band control IDs. Of the upstream band on the fiber 10, a band that is not used for fixed band communication is controlled by the DBA and is dynamically used as necessary.

  In FIG. 16, ONU2 # 1 accommodates two variable band Alloc-IDs # v1 and # v2 and transfers data using a total of three band control IDs together with the fixed band, and ONU2 # 2 is one variable. Data is transferred with a total of two band control IDs for band Alloc-ID # v3 and one fixed band, and ONU 2 # 3 assigns one variable band Alloc-ID # v4 and one fixed band Alloc-ID # f3. A case will be described in which data is transferred by a total of two band control IDs.

  Note that Alloc-ID is an ID for bandwidth control, and in practice, a plurality of session IDs can be associated with each Alloc-ID. Here, for the sake of simplicity, description will be made assuming that there is one session for each Alloc-ID. The session ID is a minimum unit of bandwidth control in the PON section, and can be normally controlled in association with a bandwidth control queue (transmission queue). By controlling the session ID and the queue in association with each other, the bandwidth management method of the present invention and the QoS control at a finer level are combined to effectively use the bandwidth in the PON section sharing the bandwidth. It is possible.

Further, a plurality of types of send queues can be used depending on the control function. For example, a fixed bandwidth queue that performs top-priority processing for fixed communications and maintains a constant rate, a fixed bandwidth guarantee queue that maintains an average communication rate over a certain time span, a minimum bandwidth, and a best-effort for flows that exceed that The minimum bandwidth guarantee queue that is treated as a maximum bandwidth, conversely, the maximum bandwidth limit queue that sets a certain upper limit rate and filters it so that it does not exceed it, and a combination of these to maintain the rate between the minimum bandwidth and the maximum bandwidth Complex queues are possible.

  Furthermore, a best effort type queue using only priority control can be used. By classifying the queue states according to the performance of these queues and notifying them to the OLT 1, theoretically more complex DBA control is possible. However, here, in order to show a fixed band / variable band control method according to the basic sequence, a description will be made assuming that the queue used for the variable band is basically only the best effort type.

  As an example, in the configuration of FIG. 16, for each Alloc-ID, one fixed rate queue for fixed bandwidth and one best effort queue for variable bandwidth are associated with each other.

  FIG. 17 shows a configuration example of the state management table of the upstream frame transmission queue in the ONU 2. Although not limited to the configuration of FIG. 16, it is generally described. However, one fixed band Alloc-ID and one or two variable band Alloc-IDs correspond to FIG. 16.

  In this embodiment, the management ID 1701 and the queue ID 1702 are associated with each other in order to include a case where a plurality of queues are assigned to the Alloc-ID. If the Alloc-ID to queue ID has a one-to-one correspondence, one of these columns is not necessary. For each queue ID 1702, a frame (data) accumulation amount 1703 and a queue control method 1704 are set. In some cases, it is difficult to dynamically set the queue control method in terms of the device configuration. In this case, the queue ID 1702 and the control method 1704 may be fixedly associated with each other. In that case, the control method 1704 becomes unnecessary. In addition, notification priority or the like may be described as a parameter for each queue in the table. Since the OLT 1 allocates a band in accordance with the notification from the ONU 2 side, by setting control parameters related to the operation of the own apparatus on the ONU 2 side, it is possible to compensate for a part that cannot be handled by the OLT 1.

  FIGS. 17A to 17C show queue states in the ONU 2 # 1 to ONU 2 # 3 before the queue state notification.

  When the queue state in FIG. 17 receives the queue state notification instruction 401 from the OLT 1, the queue state is notified to the OLT 1 by the upstream frame #i 402 in FIG. In the OLT 1, the received information is held in the bandwidth request information 263, and bandwidth calculation is performed based on this information. In order to comply with FIG. 4, it is assumed here that the fixed bandwidth allocation is based on the basic frame period (125 microseconds). FIG. 18 shows the contents entered in the bandwidth allocation tables 264 and 265 for the fixed bandwidth and the variable bandwidth after the bandwidth allocation size is calculated.

  DBA is a function that targets a variable bandwidth, and the state of the transmission queue of the bandwidth control ID of the fixed bandwidth is not notified to the OLT 1. The contents of the fixed band allocation table 264 shown in FIG. 18 are updated only when the setting of the fixed band communication channel is changed by OpS as described above. In normal operation, it is referred to when generating the band information field for the downstream frame. On the other hand, the contents of the variable bandwidth allocation table 265 are updated at the boundary point of the variable bandwidth allocation table update cycle (band allocation cycle by DBA). Based on the received queue state and the priority of Alloc-ID # v1 to Alloc-ID # v4, etc., the allocation of the bandwidth that can be used on the uplink frame included in the DBA cycle to each Alloc-ID is determined.

  Based on the fixed bandwidth allocation table 264 of FIG. 18, the fixed communication bandwidth is notified to each ONU 2 (specifically, each Alloc-ID) by the downstream frame # i + 1 of FIG. The variable bandwidth allocation based on the bandwidth request notified by the uplink frame #i is calculated during the variable bandwidth allocation table update period 450 of FIG. The calculation result shown in FIG. 18 shows that allocation starts from the frame following the upstream frame # i + m and is divided into a plurality of basic frames depending on the situation until the boundary point of the next variable bandwidth allocation cycle. I do. Therefore, the variable bandwidth allocated by the downlink frame # i + 1 is a value calculated in the previous variable bandwidth allocation table update period.

  FIG. 19 shows a queue state in each ONU 2 after sending variable band communication data according to the variable band allocation table of FIG. If each Alloc-ID is newly received from the UNI side interface of the ONU 2 as I_v1 to I_v4, the data size stored in the queue is L_vN + I_vN−BW_vN (N = 1 to 4).

  With respect to fixed band communication data using TDM, which is not subject to DBA processing, communication is always performed at a constant rate, so the queue state does not change during communication.

  As described above, the bandwidth control apparatus according to the embodiment of the present invention controls the allocated bandwidth for a plurality of data transmission apparatuses in time division multiplexing (TDM) communication. This bandwidth control device dynamically changes the bandwidth allocated to each transmission-side device in accordance with the use state of communication traffic (number of sessions, number of channels, transmission queue length of the transmission-side device, etc.).

  For this reason, a fixed bandwidth allocation table and a variable bandwidth allocation table are prepared separately. Then, the fixed bandwidth data is preferentially assigned and a certain amount of bandwidth is allocated every certain cycle. Thereafter, variable bandwidth data is allocated to the remaining bandwidth. As a result, fixed-band traffic that needs to suppress fluctuations in delay time and variable-band traffic (best-effort traffic) that has a relatively loose restriction on delay time are efficiently handled simultaneously. In addition, since the same amount of fixed band data arrives at a fixed time, jitter of the fixed band data can be suppressed. Moreover, jitter can be further suppressed by allocating fixed band data at the same timing during the band allocation period.

  In the prior art, fixed-band data and variable-band data were mixed and controlled. However, in order to secure the fixed-band data allocation amount and transmission timing, dynamic band control corresponding to dynamically changing variable-band data And static bandwidth control corresponding to fixed bandwidth data.

  In addition, since variable bandwidth data is assigned after assigning fixed bandwidth data to a specified location, calculations related to allocation of fixed bandwidth data are not required compared to the case of handling different types of traffic in a mixed manner as in the past. The amount of calculation of data allocation can be reduced.

  The following are typical examples of aspects of the present invention other than those described in the claims.

(1) A transmission device that performs data transmission / reception with one or more terminal devices via one or more connection lines,
A receiving unit for receiving a frame transmitted from the terminal device;
A storage unit that stores information that is included in the frame and indicates the amount of data that the terminal device intends to transmit;
A calculation unit that calculates a bandwidth allocation amount to be allocated to the terminal device based on the data amount;
A transmission unit for transmitting the calculated bandwidth allocation amount to the terminal device,
The transmission device, wherein the calculation unit calculates the bandwidth allocation amount according to the priority set for each type of flow for a plurality of types of flows having different transmission quality requirements.

  In the invention of (1), by preferentially securing a transmission timing and a transmission band to be fixed with respect to data (fixed band data) that is required to be transmitted at a constant period, the time slot of the fixed band data is set. Position fluctuations are eliminated and fluctuations in the arrival delay time of data are not caused. For delayable data (variable bandwidth data), the bandwidth can be effectively utilized by dynamically changing the allocated bandwidth size. In addition, by preparing multiple bandwidth allocation tables for each type of traffic, independent bandwidth allocation calculation is possible for each traffic, and multiple services with different requirements for traffic control on multiple access lines are multiplexed. In this case, the mutual influence of traffic can be suppressed and stable communication quality can be secured.

(2) The receiving unit receives a frame including information indicating a data amount to be transmitted by the terminal device at regular intervals,
The transmission device according to (1), wherein the transmission unit transmits a bandwidth allocation amount to the terminal device at each predetermined period.

  (3) The transmission according to (1), wherein the calculation unit includes means for determining a bandwidth allocation amount and means for determining a data transmission permission position in a frame transmitted from the terminal device. apparatus.

  (4) The transmission apparatus according to (1), wherein the calculation unit calculates a bandwidth allocation amount in units of the plurality of frames.

(5) The frame includes fixed band data whose transmission timing and transmission band are fixed, and variable band data which is composed of variable-length packets and whose transmission band is not fixed,
The arithmetic unit allocates a fixed amount of bandwidth for each flow to the fixed bandwidth data, and the fixed bandwidth within the frame transmitted by the terminal device so that the fixed bandwidth data is transmitted at a constant timing. The transmission apparatus according to (1), wherein a transmission position of band data is determined.

  (6) The fixed band data addressed to the terminal device is sampled at a constant period, rearranged in accordance with the transmission timing, assigned a fixed band, and transmitted at a constant timing ( The transmission device according to 5).

  (7) The transmission apparatus according to (5), wherein the calculation unit allocates a band of the variable band data to a position that does not overlap the fixed band data.

  (8) The transmission apparatus according to (5), wherein the calculation unit allocates a band to the variable band data after allocating a band to the fixed band data.

  (9) The transmission apparatus according to (5), wherein the calculation unit allocates a band in units of a plurality of the frames.

  (10) The transmission apparatus according to (9), wherein the calculation unit assigns a band to the fixed band data and the variable band data in units of different numbers of frames.

  (11) The transmission according to (10), wherein the calculation unit allocates a band to the variable band data in units of a number of frames that is an integral multiple of the number of frames in a unit to allocate a band to the fixed band data. apparatus.

  (12) The fixed bandwidth allocation table stores at least a bandwidth allocation amount and a transmission position of the fixed bandwidth data in the frame in association with a bandwidth control unit ID (11). The transmission apparatus described in 1.

(13) The variable bandwidth allocation table stores a bandwidth allocation amount in association with the bandwidth control unit ID,
The calculation unit, after allocating a band to the fixed band data, determines a transmission position of the variable band data in the frame based on a band allocation amount stored in the variable band allocation table. The transmission device according to (11).

(14) a fixed bandwidth allocation table for storing information necessary for calculating a bandwidth allocation amount of the fixed bandwidth data;
(5) The transmission apparatus according to (5), further comprising a variable bandwidth allocation table storing information necessary for calculating a bandwidth allocation amount of the variable bandwidth data.

  (15) When the allocation position of the bandwidth allocation amount set in the variable bandwidth allocation table crosses the boundary of the frame, the bandwidth size for which the bandwidth allocation has been completed and the bandwidth size for the unallocated bandwidth are retained, The transmission apparatus according to (14), wherein a remaining unallocated portion is allocated to the frame transmitted to the network.

  (16) The fixed and variable bandwidth allocation table includes at least one of a flag indicating presence / absence of encryption at the time of data transmission, a flag indicating presence / absence of FEC processing, and a flag indicating presence / absence of special frame transmission to the connection destination terminal device The transmission apparatus according to (14), wherein one flag is stored, and band information associated with at least one of the flags is stored.

It is a block diagram of a subscriber termination network according to an embodiment of the present invention. It is a block diagram of OLT and ONU which comprise the network shown in FIG. 3 is a functional block of a PON interface unit shown in FIG. 2. It is a sequence diagram which shows the basic operation | movement and control timing of DBA of embodiment of this invention. It is a flowchart of the upstream frame reception process of the embodiment of the present invention. It is a flowchart of the setting process of the variable bandwidth allocation table of embodiment of this invention. It is a flowchart of the band permission information allocation process to the upstream frame of the embodiment of the present invention. It is explanatory drawing of the fixed band allocation table of embodiment of this invention. It is explanatory drawing of the variable band allocation table of embodiment of this invention. It is explanatory drawing of a structure according to the variable band allocation table of embodiment of this invention. It is explanatory drawing of the bandwidth request information of embodiment of this invention. It is explanatory drawing of the structure of the downstream frame of embodiment of this invention. It is explanatory drawing of the data allocation state in the upstream frame of embodiment of this invention. It is explanatory drawing of the frame multiplexing system at the time of the uplink frame transmission of embodiment of this invention. It is explanatory drawing of the fixed band communication data generation timing in the case of transmitting the TDM data of embodiment of this invention on a fixed communication channel, and transmitting to a PON area. It is explanatory drawing of the connection relation of OLT and ONU of embodiment of this invention. It is explanatory drawing of the state management table of the upstream frame transmission queue of embodiment of this invention. It is explanatory drawing of the fixed band allocation table of embodiment of this invention. It is explanatory drawing of the queue state in each ONU after transmission of the variable band communication data of embodiment of this invention.

Explanation of symbols

1 ONU (Optical Network Unit)
2 OLT (Optical Line Terminal)
3 Splitter 4 Optical fiber network

Claims (6)

A transmission device that performs data transmission and reception with a plurality of optical network devices via one or a plurality of connection lines,
A receiver that receives a basic periodic frame in which small frames transmitted from each of the optical network devices are multiplexed;
Memory holding the program,
A processor that reads the program from the memory and processes the basic periodic frame;
A transmission unit that is calculated by the processor and transmits bandwidth allocation information to a basic period frame subsequent to the received basic period frame to the optical subscriber unit;
The subsequent basic period frame includes fixed band data with a fixed transmission position and transmission band, and variable band data with a variable length packet and a fixed transmission band.
The processor is
Assigning a transmission position to the fixed band data for each frame that is an integral multiple of the basic period frame so that the optical subscriber unit transmits the fixed band data at an interval that is an integral multiple of the period of the basic period frame,
After assigning the transmission position to the fixed band data, calculate a bandwidth allocation amount to the variable band data at a position that does not overlap the fixed band data in a frame whose unit is an integral multiple of the basic period frame, and further transmit A transmission device characterized by assigning a position. The transmission device according to claim 1,
Calculating the bandwidth allocation amount of the variable bandwidth data in units of integer periodic frames that are an integral multiple of the number of basic periodic frames in a unit for allocating the transmission position to the fixed bandwidth data, and allocating the transmission location. Transmission equipment. The transmission device according to claim 1,
Regarding the variable bandwidth data, when the allocation position of the bandwidth allocation amount set based on the bandwidth allocation information crosses the boundary of the subsequent frame, the bandwidth size for which the bandwidth allocation is completed, the bandwidth size for the unallocated bandwidth, And transmitting the unallocated portion to a frame transmitted next to the subsequent frame. A network system in which an optical line device and an optical network device are connected via an optical fiber, and the optical network device is further connected to a terminal via a network,
The optical line device is:
A receiver that receives a basic periodic frame in which small frames transmitted from each of the optical network devices are multiplexed;
Memory holding the program,
A processor that reads the program from the memory and processes the basic periodic frame;
A transmission unit that is calculated by the processor and transmits bandwidth allocation information to a basic period frame subsequent to the received basic period frame to the optical network device;
The subsequent basic period frame includes fixed band data with a fixed transmission position and transmission band and variable length packets, and includes variable band data with a fixed transmission band,
The processor sets a transmission position in the fixed band data for each frame that is an integral multiple of the basic period frame so that the optical line device transmits the fixed band data at an interval that is an integral multiple of the period of the basic period frame. allocation,
After assigning the transmission position to the fixed band data, calculate a bandwidth allocation amount to the variable band data at a position that does not overlap the fixed band data in a frame whose unit is an integral multiple of the basic period frame, and further transmit A network system characterized by assigning a position. The network system according to claim 4, wherein
Calculating the bandwidth allocation amount of the variable bandwidth data in units of integer periodic frames that are an integral multiple of the number of basic periodic frames in a unit for allocating the transmission position to the fixed bandwidth data, and allocating the transmission location. Network system. The network system according to claim 4, wherein
Regarding the variable bandwidth data, when the allocation position of the bandwidth allocation amount set based on the bandwidth allocation information crosses the boundary of the subsequent frame, the bandwidth size for which the bandwidth allocation is completed, the bandwidth size for the unallocated bandwidth, And assigning the unassigned portion to a frame transmitted next to the subsequent frame.

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