KR100748093B1 - Burst data reception method and apparatus in epon - Google Patents

Abstract

The present invention provides an optical module for receiving burst data of different optical power levels from a plurality of optical termination devices (ONU), level recovery and converting optical signals of the burst data into electrical signals, and synchronizing time of the burst data. A connection control unit generated by generating a multi-point control protocol loss signal for reducing and reducing a synchronization time when the multi-point control protocol loss signal is generated, and a code group in a section where the multi-point control protocol loss signal is not generated. By receiving the burst data in the Ethernet passive optical subscriber network by including a sused portion for aligning and recovering the received burst data, the synchronization time, that is, the reception recovery time can be reduced by the fast operation characteristics such as the actual optical signal. This improves upband efficiency and burst data reception performance. There is an effect.

EPON, OLT, ONU, MPCP LOS, MPCP RESET, Burst Data, CDR, Discovery, Optical Module, Suddes Chip, OLT MAC.

Description

BURST DATA RECEPTION METHOD AND APPARATUS IN EPON}

1 is a block diagram showing the structure of a general Ethernet passive optical subscriber network;

2 is a block diagram schematically illustrating a data transmission method in a general Ethernet passive optical subscriber network;

3 is a block diagram schematically showing the internal structure of the optical line terminal (OLT) in FIG.

4 is a block diagram showing the structure of an optical line terminal (OLT) according to an embodiment of the present invention;

5 is a timing diagram illustrating signals generated in an optical line terminal (OLT) according to an embodiment of the present invention;

 6 is a flowchart illustrating a discovery process for operating a synchronization time in an Ethernet passive optical subscriber network according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10: Optical line terminal (OLT) 11: Receiver (OLT OTRx)

12: SerDes 13: connection control unit (OLT EPON MAC)

20: optical termination device (ONU) 30: subscriber terminal (User)

The present invention relates to a data receiving processing method and apparatus in an optical line terminal (OLT) of an Ethernet passive optical subscriber network, and more particularly, to a burst data receiving processing method and apparatus for improving a burst mode reception performance in an optical line terminal. will be.

Nowadays, with the rapid increase of Internet users using wireless communication, high speed internet technologies are being developed to provide users with faster internet services. The wireless LAN technology is a typical technology for such a high speed Internet service. However, the WLAN provides a large gap between the wide area network and the end user request, and causes a bottleneck in the end user. Recently, passive optical network (PON) has been developed to solve such band bottlenecks. Such PON technology may be classified into ATM PON (APON) and Ethernet (Ethernet PON: EPON). Here, the EPON technology is a control chip technology that can be connected to an FTTH (Fiber To The Home) that can use various communication services such as the Internet, Internet TV, digital TV, and telephone at a low price with only one fiber. to be.

The structure of the EPON is as shown in Figure 1 attached, the EPON is a system for transmitting a signal to the end user through the optical cable network, depending on where the EPON is terminated, FTTC, FTTB or FTTH, etc. Separated by.

Referring to FIG. 1, the EPON includes, for example, an optical line terminal (hereinafter referred to as an OLT) 10 that interoperates with an IP network, a broadcasting network, a TDM network, and the like. An optical network unit (hereinafter referred to as ONU) 20 located at the subscriber end of the optical subscriber network and connected to the subscriber terminal 30, for example, an STB, a PC, or the like. And EPON typically uses a single fiber to apply to the subscriber end in a point-to-multi-tree structure. The optical signal transmitted from the Ethernet passive optical network system is divided by an optical star coupler / splitter 40 according to whether the direction of the light is upward or downward, and is loaded on multiple optical fibers or combined to provide a single optical signal. Is transmitted to the optical fiber. As an example, a data transmission method in EPON will be described with reference to FIG. 2.

The EPON transmits data in transmission units of Ethernet frames, and each ONU 20 is dynamically or fixedly allocated to a time slot in an uplink path to transmit data to a common OLT 10. The data output from each ONU 20 are multiplexed by the optical star coupler 40 and transmitted to the OLT 10. On the contrary, in the downlink path, when the OLT 10 transmits a data stream, the optical star coupler 40 demultiplexes and transmits the data stream to each ONU 20.

The OLT 10 recovers burst data transmitted by the ONU 20 in a burst manner through an uplink channel. However, since EPON is a technology for high-speed Internet service, the delay of such burst data recovery time can significantly affect the speed of the Internet and cause bandwidth consumption of the uplink channel. The causes of such upband waste are largely the time required for recovering the transmission data from the ONU in the OLT and the laser on / off time of the ONU. The sum of these times, excluding the actual data transfer, is called the guard time.

Therefore, it is necessary to shorten the clock and data recovery time when the burst data is received at the OLT 10. However, the conventional EPON only considers the allocation of the SYNC time.

In general, the receiving part of the OLT of the EPON system uses an EtherSupp chip, which takes about 200 nsec CDR time depending on the type and the method of use. However, the CDR time becomes a synchronization time in addition to the OLT optical reception level recovery time. When the CDR time is large, the synchronization time becomes longer, and when the synchronization time becomes longer, a wasteful band is generated in the uplink. As the number of branches increases, the overhead caused by the synchronization time increases.

Accordingly, an object of the present invention is to provide a burst data reception processing method and apparatus for shortening a recovery time (synchronization time) in an optical line terminal (OLT) of an Ethernet passive optical subscriber network (EPON) to increase upband efficiency.

It is another object of the present invention to receive burst data by reducing reception recovery time (synchronization time) by having a sustain chip that applies Loss (LOS) generated by a multipoint control protocol (MPCP) to an optical line terminal (OLT). A method and apparatus for processing are provided.

The burst data reception processing method in the Ethernet passive optical subscriber network for achieving the above objects of the present invention, in the Ethernet passive optical subscriber network having an optical line terminal (OLT) and a plurality of optical termination devices (ONU), An optical line terminal (OLT) for processing burst data received from the plurality of optical termination devices (ONU), comprising: receiving burst data from the plurality of optical termination devices (ONU), and the burst data Generating a multi-point control protocol loss signal for reducing the synchronization time of the signal, shortening the synchronization time according to the generation of the multi-point control protocol loss signal, and a section in which the multi-point control protocol loss signal does not occur Aligning the code groups to recover the received burst data.

A burst data reception processing apparatus in an Ethernet passive optical subscriber network for achieving the objects of the present invention, receiving burst data of different optical power levels from a plurality of optical termination devices (ONU) to recover the level and restore the burst data. An optical module for converting an optical signal into an electrical signal, a connection controller generated by generating a multi-point control protocol loss signal for reducing the synchronization time of the burst data, and a synchronization time when the multi-point control protocol loss signal is generated. And a sustain unit for recovering the received burst data by aligning code groups in a section in which the multi-point control protocol loss signal does not occur.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals have the same reference numerals as much as possible even if displayed on different drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

An embodiment of the present invention will be described by applying an Ethernet passive optical subscriber network (EPON), the optical receiving the burst data transmitted from the optical termination devices (ONU) through the uplink channel as shown in FIG. The line terminal (OLT) will be described, and the OLT operation for reducing reception recovery time by including a SerDes chip in the optical line terminal (OLT) will be described. Here, the time taken to recover stable data from the burst optical signal in the OLT is the level recovery time of the optical module and the CDR (Cloc & Data Recovery) time of the sused chip, and the sum of these times is called a synchronization time. Since the CDR time generally requires several usec in several hundred nsec, it is necessary to reduce the CDR time in order to increase the upband efficiency.

First, the up / down data transmission of the EPON system as shown in FIG. 2 will be briefly described again for convenience of description of the embodiment of the present invention.

Again, referring to FIG. 2, the EPON system includes a single optical line terminal (OLT) 10 and a plurality of optical termination units (ONUs) 20 in a point-to-multiple tree structure through a passive distributor 30. Is done.

The OLT 10 broadcasts downlink frames transmitted to the plurality of ONUs 20 in variable length packets according to the IEEE802.3 protocol. Here, each frame may process only a specific ONU 20, or all ONU 20 may process, and are delivered to the subscriber of the ONU 20.

The plurality of ONUs 20 transmits an uplink frame only during a time determined by the OLT 10 so that collision does not occur between adjacent ONUs 20 using a TDMA scheme. Accordingly, the plurality of ONUs 20 transmits data in a burst manner. Therefore, the OLT 10 should be able to receive burst data transmitted from the plurality of ONUs 20.

In case of such uplink data transmission, there are times to consider in addition to the actual data transmission time in the use of the band, which is the laser on / off time of the ONU 20, the level recovery time and the CDR time and the code group of the OLT 10 optical module. (code group) sort time, etc. Therefore, it is necessary to reduce these times to improve upband usage performance.

Then, the accompanying drawings of the apparatus and method for receiving the burst data in the OLT in consideration of the times according to an embodiment of the present invention will be described. For convenience of explanation, the burst data receiving apparatus according to the standard will be described, and then the burst data receiving apparatus according to the embodiment of the present invention will be described.

FIG. 3 is a block diagram schematically illustrating an internal structure of an optical line terminal (OLT) in FIG. 1.

Referring to FIG. 3, the OLT 10 includes a receiving unit (OLT OTRx) 11, a sub-deser (SerDes (PMA)) 12, and an access control unit (OLT EPON MAC) in the form of chips. It is provided inside.

When the receiver 11 of the OLT 10 receives burst data from each ONU 20, the receiver 11 generates a LOS signal to the susceptor 12. Here, a gap (Gap) exists between burst signals when the burst is received, and a section in which there is no optical signal occurs.

In general, the sudest unit 12 attempts to lock the PLL to a non-normal signal even in a period where the optical signal is absent. Therefore, the clock is severely shaken, and the lock time of the PLL is released so that the time required for the lock of the PLL in the next ONU burst reception becomes considerably longer, thereby increasing the CDR time. Therefore, the susceptor 12 receives the LOS signal of the optical module transmitted from the receiver 11 to shorten the times. That is, when the LOD signal of the optical module receives the LOS signal, the sudest unit 12 does not lock the reception signal of the receiver 11 rotor in the LOS period, but locks the TBC, which is the transmission clock, to stabilize the LOS signal. Generate a receive clock and then fast CDR lock.

The susceptor 12 receives the LOS signal of the optical module receiver 11 through the LCK_REF or SYNC_EN pin. In this case, the LCK_REF is an active low signal. When the LCK_REF is inactive, the receiving PLL operates normally to lock the serial data from the receiving unit 11. The transmission clock TBC is locked. On the other hand, SYNC_EN (EN_CDET) is an enable comma detector signal that enables code-group alignment in a section in which there is no LOS signal.

However, in general, OLT is difficult to apply to burst data reception in EPON because the LOS signal of the optical module does not have the fast operation characteristics like the actual optical signal and has a slow response characteristic.

Therefore, in the embodiment of the present invention, since the burst data reception time from the ONU is known in advance in the multi-point control protocol (MPCP) of the OLT, the LOS signal is generated using the same as the actual received optical signal. At this time, the generated MPCP LOS signal should be made to increase the delay or LOS interval in consideration of the laser on / off time of the ONT optical module and the level recovery time of the OLT optical module. In the same principle, when the EPON OLT optical module requires a reset signal, the OLT MPCP reset signal is generated and transmitted to the OLT optical module to reduce the level recovery time.

4 is a block diagram illustrating a structure of an optical line terminal (OLT) according to an exemplary embodiment of the present invention.

Here, it should be noted that the OLT according to the embodiment of the present invention is shown with reference numerals differently from the OLT 10 according to the standard.

Referring to FIG. 4, the OLT 100 of the EPON includes an OLT OTRx 110, a Serde 120, and a connection controller OLT EPON MAC of the optical module. 130 is provided inside in the form of a chip.

The EPON provides a time division multiple access scheme (TDMA) for an uplink channel, and when the ONU 20 transmits an Ethernet frame to the OLT 10, several ONUs 20 may overlap each other so that collision of traffic may occur. Will occur. In order to avoid such a collision, the EPON provides a method of uplink sharing through time division multiple access using the MPCP protocol. Accordingly, the OLT 100 of the EPON applies the OLT MPCP protocol to the connection controller 130.

The receiving unit 110 of the optical module receives burst data of different optical power levels from each ONU 20, converts the level recovery and received optical signals into electrical signals, and receives burst data when the burst data is received. A reception bit (rx_bit) signal is generated at 120, and a transmission bit (tx_bit) signal is received from the sustain unit 120.

The sustain unit 120 is a chip of the PMA layer, performs data and clock recovery, and performs code group alignment. In addition, when the transmission clock (tx_clk, TBC) is generated from the connection controller 130 and the reception unit 120 receives the reception bit (rx_bit) signal from the reception unit 110, the reception unit 110 transmits a transmission bit ( tx_bit) signal. The sudest unit 120 receives an MPCP LOS signal from the access controller 130. At this time, the MPCP LOS signal is input to the LCK_REF or SYNC_EN pin, like the LOS signal of the optical module of FIG. 3.

When the MPCP LOS signal is generated, the susceptor 120 inputs a signal to the LCK_REF pin, and when the signal is inactive as described above, the reception PLL operates normally to lock the serial data from the receiver 11. In the case of being active, the transmission clock TBC from the connection control unit 13 is locked.

On the other hand, when the MPCP LOS signal is not generated, the sudes unit 120 inputs a signal to SYNC_EN (EN_CDET) to perform code-group alignment in a section in which there is no LOS signal.

The access controller 130 generates the MPCP LOS and transmits the generated MPCP LOS signal to the sudest unit 120 to shorten the CDR lock time.

The access control unit 130 uses OLT MPCP, which is a protocol for controlling in a media access control (MAC) layer, and burst data upon receiving burst data from each ONU 20 through the OLT MPCP. Not only can you know the gap between the received data, but you can also see the starting point of the next burst. This is because the ONUs 20 are configured to transmit burst data in the OLT only at a predetermined time from the OLT MPCP. Accordingly, the access controller 130 may generate an OLT MPCP LOS signal using the OLT MPCP.

In addition, when the receiver 110 of the optical module needs the reset signal, the connection controller 130 generates an MPCP reset signal and transmits the generated MPCP reset signal to the receiver 110. Accordingly, the receiver 110 receives the MPCP reset signal and uses it to shorten the burst level recovery time.

By generating and applying the MPCP LOS signal instead of the LOS signal of the optical module in the OLT 100, the CDR lock time can be shortened, and the reception clock can be prevented from being severely changed, thereby improving the burst reception performance of the OLT. have. The effect of this performance improvement can be clearly seen in the timing diagram shown in FIG.

As shown in FIG. 5, a reception clock signal (OLT Optical Rx) is generated as the burst data is received by the receiver 110 of the optical module. At this time, the OLT 10 according to the standard generates an optical module loss (OTRx LOS) signal, the OLT 10 is delayed after the gap (gap) starts after the first clock (ONU i) generation of the received clock signal ( The delay occurs and the LOS signal of the optical module is generated only after the second clock (ONU i + 1) occurs.

On the other hand, as shown in FIG. 5, the MPCP LOS generated by the access control unit 130 according to the embodiment of the present invention is generated when the gap Gap starts after the first clock ONU i of the received clock signal is generated. Generated with the same signal as the gap time, the OLT 100 considers the laser on / off time of the ONT optical module and the level recovery time of the OLT optical module by providing an extended area in the MPCP LOS signal. Delay or LOS interval can be increased. The MPCP RESET signal is also generated at the same time as the MPCP LOS.

Meanwhile, according to the EPON standard, the synchronization (SYNC) time information of the OLT 10 is exchanged in the registration of the new ONT 20, and when the synchronization time is set during the discovery process (hereinafter referred to as the registration process), the registered time is registered. It is set to continue to use the same value afterwards. This synchronization time can be reduced by applying the above-described OLT 100. When registering, an error occurs when receiving the burst data from the ONU 20 due to insufficient synchronization time. Can be.

In addition, in order to apply the MPCP LOS or the MPCP reset according to the embodiment of the present invention as described above, it is necessary to know the exact burst start point from the ONUs, which is possible in the case of pre-registered ONUs, so when there is a new ONU registration request The MPCP LOS or MPCP reset may not be applied to short sync time. Therefore, in the EPON system according to the embodiment of the present invention, the synchronization time must be newly set during the registration process between the OLT and the ONU.

In the embodiment of the present invention, even when the new ONU is registered, a registration process for short operation of synchronization time by applying the MPCP LOS or MPCP reset will be described with reference to the accompanying drawings.

6 is a flowchart illustrating a registration process for operating a synchronization time in an Ethernet passive optical subscriber network according to an embodiment of the present invention.

Referring to FIG. 6, in step 210, the OLT 100 transmits a gate message to the ONU 20. Here, the gate message includes DA, SA, Grant, and Sync_Time1 information. Then, the ONU 20 generates a random delay time from the starting point of the grant, and responds only after the random delay time passes. Accordingly, since the connection control unit 130 of the OLT 100 does not know when to receive the burst data from the ONU 20, the OLT 100 may subsequently transmit the first synchronization time Sync_Time1 included in the gate message. Different from the second synchronization time (Sync_Time2) of the registration message. That is, initially, the first synchronization time used during the registration process is set long, and after the registration is completed, the second synchronization time used for transmission is set short and exchanged.

After the random delay time, in step 220, the OLT 100 receives a registration request (REGISTER_REQ) message from the ONU 20. Here, the registration request message includes DA, SA, Grant, and Pending grants information.

Then, in step 230, the OLT 100 transmits a REGISTER message to the ONU 20. Here, the registration message includes DA, LLID, Sync_Time 2, and echo of pending grants information. The ONU 20 then sets and stores the information included in the received registration message.

In step 240, the OLT 100 transmits a gate message to the ONU 20. At this time, the transmitted gate message includes DA, SA, LLID, and Grant information. The OLT 20 then sends a registration response (REGISTER_ACK) message as a response to the registration message. Accordingly, in step 250, the OLT 100 receives a registration response message transmitted from the ONU 20. The registration response message includes DA, SA, echo of LLID, and echo of Sync_Time information.

As such, when there is a request for registration of a new optical termination device, the new optical termination device transmits burst data at a time within a predetermined period set by the chip control unit OLT MPCP. Since the exact burst start point is unknown, the synchronization time required to receive burst data must be long. Therefore, the first exchange time is set long enough, and after that the starting point of burst data from ONU can be known accurately, the synchronization time is reduced. The registration process is performed by setting and exchanging.

According to the embodiment of the present invention as described above, the present invention, OLT MPCP equal to the actual received optical signal that can know in advance the burst data reception time from the ONU instead of a signal having a slow response characteristics, such as the LOS signal of a conventional optical module By generating the MPCP LOS signal and the MPCP reset signal in the OLT connection controller using the Suther chips, the synchronization time, that is, the reception recovery time, can be reduced with fast operation characteristics such as an actual optical signal.

In addition, the present invention is to set the synchronization time to be used during the registration process and the later synchronization time differently to exchange the synchronization time information between the OLT and ONU to reduce the synchronization time and at the same time generated in the OLT using MPCP LOS The lack of synchronization time can also be solved.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention generates the MPCP LOS signal and the MPCP reset signal by using the OLT MPCP in the OLT, and applies the same to a sutherce chip so as to reduce the synchronization time, that is, the reception recovery time, with fast operating characteristics such as an optical signal. As a result, the efficiency of uplink bandwidth and burst data reception can be improved.

Claims (10)

In an Ethernet passive optical subscriber network having an optical line terminal (OLT) and a plurality of optical termination units (ONU), the optical line terminal (OLT) to process burst data received from the plurality of optical termination units (ONU) In the method for Receiving burst data from the plurality of optical termination devices (ONU), Generating a multi-point control protocol loss signal for reducing the synchronization time of the burst data; Shortening the synchronization time according to the generation of the multi-point control protocol loss signal; And recovering the received burst data by aligning code groups in a section in which the multi-point control protocol loss signal does not occur. The method of claim 1, And generating a multi-point control protocol reset signal for reducing the level recovery time of the optical module and generating the reset signal to the optical module. The method of claim 1, wherein the generating of the multi-point control protocol loss signal comprises: Checking a plurality of optical termination devices (ONUs) and a preset burst data transmission time; Identifying a gap between the burst data signals and a start point of the next burst data when the burst data is received; And generating the multi-point control protocol loss signal using the identified gap and starting point. The method of claim 1, If there is a request for registration of a new optical terminator, further comprising registering the new optical terminator using a different synchronization time before and after a time point at which a start point of burst data is known from the new optical terminator. A burst data reception processing method in an Ethernet passive optical subscriber network. The process of claim 4, wherein the registering of the new optical termination device comprises: Setting and exchanging a long length of a first synchronization signal when the exact starting point of the burst data is not known through the multi-point control protocol; When the exact starting point of the burst data is known through the multi-point control protocol, setting and replacing the second synchronous signal exchanged to be small; . An optical module for receiving burst data of different optical power levels from a plurality of optical termination devices (ONU) to recover the level and convert the optical signal of the burst data into an electrical signal; A connection controller generated by generating a multi-point control protocol loss signal for reducing the synchronization time of the burst data; When the multi-point control protocol loss signal is generated, the synchronization time is reduced, and a sustain unit for recovering the received burst data by aligning code groups in a section in which the multi-point control protocol loss signal is not generated. An apparatus for processing burst data in an Ethernet passive optical subscriber network. The method of claim 6, And the connection controller generates a multi-point control protocol reset signal for reducing the level recovery time of the optical module and generates the multi-point control protocol reset signal to the optical module. The method according to claim 6 or 7, The access control unit generates the multi-point control protocol loss signal using a gap between the plurality of optical end devices ONU and the burst data signal identified through a preset burst data transmission time and a start point of the next burst data. An apparatus for processing burst data in an Ethernet passive optical subscriber network comprising: The method of claim 6, When there is a registration request of a new optical termination device, the access controller sets a different synchronization time before and after a time point at which a start point of burst data is known from the new optical termination device, and sets the new synchronization time using the different synchronization times. An apparatus for processing burst data in an Ethernet passive optical subscriber network, comprising registering an optical termination device. The method of claim 9, The connection control unit sets and exchanges a first synchronization signal long when the exact starting point of the burst data is not known through the multi-point control protocol, and exchanges a second synchronization signal when the exact starting point of the burst data is known. A burst data receiving processing device in an Ethernet passive optical subscriber network, wherein the new optical terminator is registered by setting a small value and exchanging the same.

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