Time delay indication information distribution method, device and system

Abstract

The embodiment of the invention provides a time delay indication information distribution method, which comprises the following steps that: in a registration stage of a first SFU, an MFU obtains a round-trip delay RTD1 of an optical fiber line between the first SFU and the MFU; in a registration stage of a second SFU, obtaining a round trip delay RTD2 of an optical fiber line between the second SFU and the MFU; the MFU assigns equalization time delays EqD1 and EqD2 for the first SFU and the second SFU respectively, the sum of RTD1 and EqD1 is equal to the sum of RTD2 and EqD2, and the difference value between EqD1 and EqD2 is not greater than 12us; and the MFU sends the EqD1 to the first SFU, sends the EqD2 to the second SFU, and instructs the first SFU and the second SFU to respectively delay the EqD1 and the EqD2 and then send a response message. The embodiment of the invention further provides a device and a system. By using the embodiment of the invention, the MFU can receive the response message more quickly, so that the back-and-forth interaction information processing efficiency between the MFU and the SFU is higher.

Description

Technical Field

[0001] The present invention relates to the field of network communications, and in particular to a method, device and system for allocating delay indication information. Background Art

[0002] Fiber to the room (FTTR) is a new home network access architecture. Simply put, the main gateway connected to the external network is further connected to the sub-gateway in each room through optical fiber. The sub-gateway provides users with reliable wireless access points (APs) to allow wireless signals to cover every corner of the home scene. However, the traditional main gateway to sub-gateway generally uses the Passive Optical Network (PON) technology protocol. Since PON is a point-to-multipoint fiber optic transmission and access technology, the length of the connecting optical fiber corresponding to different connection points is inconsistent, and the maximum difference may be close to 20KM. The resulting delay is relatively large and may not meet the needs of each AP in the FTTR scenario. Summary of the invention

[0003] In view of the above problems in the prior art, the embodiments of the present invention provide a method, device and system for allocating delay indication information.

[0004] A specific embodiment of the present invention provides a method for allocating delay indication information, including: the MFU obtains the round-trip delay RTD1 of the optical fiber line between the first SFU and the MFU during the registration stage of the first SFU; obtains the round-trip delay RTD2 of the optical fiber line between the second SFU and the MFU during the registration stage of the second SFU; the MFU specifies equalization delays EqD1 and EqD2 for the first SFU and the second SFU respectively, wherein RTD1+EqD1=RTD2+EqD2, i.e., ensuring that the response messages of the first SFU and the second SFU can arrive at the MFU at the same time; wherein the difference between EqD1 and EqD2 is required to be no more than 12us; the MFU sends the EqD1 to the first SFU and sends the EqD2 to the second SFU, and instructs the first SFU and the second SFU to send response messages after delaying EqD1 and EqD2 respectively.

[0005] As an optional embodiment, the difference between EqD1 and EqD2 is further no greater than 39 us, or even no greater than 28 us.

[0006] The embodiment of the present invention further provides a transmission method, comprising: a master optical fiber unit MFU sends an equalization delay EqD1 to a first slave optical fiber unit SFU; specifically, the EqD1 is used to instruct the first SFU to send a response message after delaying the EqD1 after starting to receive a data frame; the MFU starts to send a first data frame to the first SFU through a first optical fiber line at time T0; the first SFU sends a first data frame to the first SFU at time T1; sr1 The first SFU starts to receive the first data frame at (T sr1 +EqD1) starts to send a response message; the MFU starts to send a response message at T mr1 The MFU receives a response message sent by the first SFU at T f The first data frame is sent at time T f Greater than or equal to T mr1 .

[0007] As an optional embodiment, the first SFU starting to receive the first data frame at time Tsr1 means receiving the first bit of the first data frame at time Tsr1.

[0008] As another optional embodiment, the MFU starting to send the first data frame at time T0 means sending the first bit of the first data frame at time T0.

[0009] As another optional embodiment, the first data frame may be a superframe.

[0010] An embodiment of the present invention further provides a network device, including a processor, a memory, a PON media access control chip and a transceiver; wherein the memory is used to store program codes, and the processor cooperates with the memory 602, the PON MAC chip and the transceiver to execute the above-mentioned MFU execution method.

[0011] An embodiment of the present invention further provides a signal transmission system, which includes the above-mentioned master optical fiber unit MFU and at least one slave optical fiber unit SFU.

[0012] It can be seen from the technical solutions provided above that the MFU can receive the response message more quickly, making the back-and-forth interactive information processing between the MFU and the SFU more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of a PON system architecture provided by the prior art;

[0014] Figure 2 A schematic diagram of the distributed balanced delay provided by the prior art;

[0015] Figure 3A schematic diagram of the system architecture of the FTTR provided by an embodiment of the present invention;

[0016] Figure 4 A flow chart of a method for allocating delay indication information provided by an embodiment of the present invention;

[0017] Figure 5 A flow chart of a signal transmission method provided by an embodiment of the present invention;

[0018] Figure 6 A structural diagram of a network device provided for an embodiment of the present invention; DETAILED DESCRIPTION

[0019] Figure 1 A schematic diagram of a PON system architecture is shown in FIG. Figure 1 As shown, the PON system 100 includes at least one OLT 110, at least one ODN 120 and multiple ONUs 130. Among them, the OLT 110 provides a network side interface for the PON system 100, and the ONU 130 provides a user side interface for the PON system 100 and is connected to the ODN 120. If the ONU 130 directly provides a user port function, it is called an optical network terminal (Optical Network Terminal, ONT). For the convenience of description, the ONU 130 mentioned below refers to the ONT that can directly provide a user port function and the ONU that provides a user side interface. The ODN 120 is a network composed of optical fibers and passive optical splitters, which is used to connect the OLT 110 device and the ONU 130 device, and is used to distribute or multiplex data signals between the OLT 110 and the ONU 130.

[0020] In the PON system 100, the direction from OLT 110 to ONU 130 is defined as the downstream direction, and the direction from ONU 130 to OLT 110 is defined as the upstream direction. In the downstream direction, OLT 110 broadcasts downstream data to multiple ONUs 130 managed by OLT 110 using time division multiplexing (TDM), and each ONU 130 only receives data carrying its own identification; in the upstream direction, multiple ONUs 130 communicate with OLT 110 using time division multiple access (TDMA), and each ONU 130 sends upstream data according to the time domain resources allocated to it by OLT 110. Using the above mechanism, the downstream optical signal sent by OLT 110 is a continuous optical signal, and the upstream optical signal sent by ONU 130 is a burst optical signal.

[0021] For OLT, the logical distances from different ONUs to OLT are not equal, the transmission time of optical signals on optical fibers is different, and the time when they arrive at each ONU is different. At the same time, the round trip delay (RTD) between OLT and ONU will also change with time and environment; the RTD includes the transmission delay on the line and the data processing delay (also known as reaction delay) of the equipment. In order to ensure that the uplink data sent by each ONU to OLT is inserted into the specified time slot after the ODN optical fiber converges, without collision and without too large a gap, OLT must accurately measure the distance between each ONU and OLT through ranging, so as to control the time when each ONU sends uplink data.

[0022] The technical concept of ranging technology is that the time from each ONU to OLT is the same, so the GPON system adopts a method based on this concept, taking the farthest ONU as the benchmark, calculating the delay from OLT to ONU, and accurately calculating the distance between OLT and ONU. For ONUs that are closer, a delay will be added to the ONU so that the time for the closer ONU to reach OLT is synchronized with the farthest ONU. The purpose of adding delay is to make the logical distance from all ONUs to OLT the same, that is, from the perspective of OLT, all ONUs are equal in transmission distance. The delay added to the ONU is called equalization delay, and the whole process is called ranging.

[0023] When the ONU registers for the first time, the OLT will start the ranging function, obtain the ONU's round-trip delay RTD, calculate the physical distance of each ONU, and specify the appropriate equalization delay (EqD) parameter according to the physical distance of the ONU. The OLT needs to open a window, that is, the Quiet Zone, during the ranging process to suspend the upstream transmission channel of other ONUs. The OLT synchronizes the data frames sent by each ONU by specifying EqD for the ONU, ensuring that no conflict will occur on the optical splitter when each ONU sends data. It is equivalent to all ONUs being at the same logical distance and sending data in the corresponding time slot, thereby avoiding collisions of upstream signals. In fact, when selecting EqD, the OLT will first determine the time Tedq between all ONUs arriving at the OLT based on the distance to the nearest ONU and the farthest ONU, as well as the maximum round-trip delay time (RTD) of the ONU; and then obtain the EqD on each line based on EqD = Tedq-RTD. After the OLT calculates and transmits the equalization delay EqD to the ONU, the selected value of EqD remains unchanged during the cycle of the PON.

[0024] GPON's ranging is completed during the ONU registration phase. When the ONU receives the SN request message sent by the OLT, the ONU waits for a certain response time and then returns an SN response message. After receiving the response message and verifying its legality, the OLT assigns an ONU-ID to the ONU. After receiving the assigned ONU-ID, the ONU enters the ranging state.

[0025] The principle of OLT calculating and allocating balanced delay is as follows Figure 2 As shown. Assume that the OLT sends a ranging request to the ONU at time T1, and at the same time instructs other ONUs to stop sending upstream services, and opens a ranging window in the upstream time slot for this ONU to use. The ONU receives the ranging request at time T2, and after internal processing, sends an upstream frame in response to the ranging request at time T3, and the OLT receives the upstream frame in response to the ranging request at time T4. Then the OLT can calculate the RTD of the ONU based on T4 and T1. Figure 1 The zero-distance equivalent delay Teqd in is a value set by the OLT according to the longest optical fiber length, which is greater than or equal to the RTD of the ONU with the longest logical distance. To ensure that the upstream data phase of all ONUs connected to the same PON interface of the OLT is the same, the OLT allocates EqD to all ONUs under the same PON interface of the OLT according to the following principles, where i represents the ONU number:

[0026] EqD(i)=Teqd-RTD(i) (Formula 1)

[0027] After processing the request from the OLT, the subsequent ONU must wait for the EqD time before sending upstream data or upstream frames. This ensures that the upstream data phase of all ONUs under the same PON port of the OLT is the same.

[0028] Traditional PON systems are mainly used in fiber-to-the-home (FTTH) scenarios, where each home user only has one optical network unit. On the basis of FTTH, in order to solve the problem of poor home network WIFI coverage, the optical fiber can be further extended to the residents' rooms. An ONU is installed in each room, which shortens the distance between the user terminal and the ONU and improves the signal quality. This application scenario is called fiber to the room (FTTR).

[0029] Figure 3Figure 1 is a schematic diagram of the system architecture of FTTR. The FTTR network and the FTTH network can be regarded as two-level PON systems. The OLT in the first-level PON system (FTTH) is deployed in the central computer room, and the ONU is deployed in the information box of the home. The OLT in the second-level PON system (FTTR) can replace the ONU in FTTH and be deployed in the information box of the home. The OLT in the FTTR scenario has similar functions to the OLT in the FTTH scenario, and the OLT can also have similar functions to the ONU in the FTTH scenario. In other words, the OLT in the FTTR can be used as a network device that connects FTTH and FTTR. The ONU in the FTTR can be deployed in each room of the home to connect with the user terminal. The ONU and the ONU in the FTTH are essentially the same type of network devices. The difference is that the ONU in the FTTH is generally deployed in the information box, and there is usually an access point (AP) between the user terminal. The ONU in the FTTR enters each room, and the ONU also has the function of an AP, which can directly connect to the user terminal through WiFi. It should be noted that the OLT in the second-level PON system (FTTR) can also be called the "master gateway" or "master fiber unit" (MFU), and the ONU can also be called the "slave gateway" or "slave fiber unit" (SFU); and because the SFU will act as an access point AP to provide STA with WIFI connection, the SFU will also be called AP. This application does not limit the specific names of the above devices.

[0030] Since the transmission distance between OLT and ONU in the traditional PON system can support up to 20KM, the distance between different ONUs under the same OLT can be up to 20KM; however, in the FTTR scenario, the span of a family house is generally tens of meters, and the maximum span is hundreds of meters; due to the limitations of the family house, the maximum difference between the distance between multiple SFUs under an MFU set inside the family house and the MFU is only hundreds of meters. The selection rules for EqD in the traditional PON system may not be applicable to the FTTR scenario.

[0031] Based on this, according to the following calculation formula:

[0032]

[0033] For FTTR networks, L min The value is 0km, D max RspTime is 1km max The value is 36us. After calculation, T eqd The minimum value can be 36us+10us=46us. That is, after the OLT starts sending a signal, it can start receiving a reply signal from the ONU at least 46us later.

[0034] The embodiment of the present invention provides a method for distributing delay indication information, and the method is applied to an optical fiber network. Figure 4 As shown, the method includes:

[0035] Step 401: During the registration phase of the first SFU, the MFU obtains the round trip delay RTD1 of the optical fiber line between the first SFU and the MFU;

[0036] Step 402: During the registration phase of the second SFU, the MFU obtains the round trip delay RTD2 of the optical fiber line between the second SFU and the MFU;

[0037] Step 403: The MFU specifies equalization delays EqD1 and EqD2 for the first SFU and the second SFU, respectively, wherein RTD1+EqD1=RTD2+EqD2, and the difference between EqD1 and EqD2 is not greater than 12us;

[0038] Specifically, from RTD1+EqD1=RTD2+EqD2, it can be seen that the difference between EqD1 and EqD2 is to compensate for the difference between RTD1 and RTD2, and RTD includes the transmission delay on the line and the data processing delay of the device; from the above analysis of FTTR network cabling, the maximum difference between the distances of multiple SFUs under an MFU to the MFU is only a few hundred meters, that is, the difference in the length of the optical fiber line connecting the same MFU to multiple SFUs does not exceed 1 km, so the transmission delay difference of optical fibers of different lengths is at most 10us; and the difference in data processing by different devices is not large, generally not more than 2us; so the difference between RTD1 and RTD2 will not be greater than 12us; and the difference between EqD1 and EqD2 will not be greater than 12us;

[0039] Step 404: The MFU sends the EqD1 to the first SFU and the EqD2 to the second SFU, and instructs the first SFU to delay sending a response message after the EqD1 is received after the data frame sent by the MFU is started, and instructs the second SFU to delay sending a response message after the EqD2 is received after the data frame sent by the MFU is started.

[0040] As an optional implementation, the fiber length difference D max Take 0.5km or 0.8km and get the corresponding T eqd The minimum values ​​are 28us and 39us, respectively. Similarly, in step 403, it may be further required that the difference between EqD1 and EqD2 is not greater than 7us, or not greater than 10us, respectively.

[0041] By using the scheme of this embodiment, after the first SFU and the second SFU under the MFU receive the data frame sent by the MFU, they delay EqD1 and EqD2 respectively and then send a response message; under the premise of reaching the MFU at the same time, EqD1 or EqD2 can be guaranteed to be as small as possible, reducing the waiting delay of the first SFU or the second SFU. In this way, the MFU can receive the response message faster, making the back-and-forth interactive information processing between the MFU and the SFU more efficient. The difference between EqD1 and EqD2 is no more than 12us s, which specifically analyzes the networking characteristics of FTTR, digs out the technical points that can improve the processing efficiency of the optical fiber network, and meets the demand for higher response time requirements for home WIFI terminals or applications under FTTR networking.

[0042] The embodiment of the present invention provides a signal transmission method, which is applied to an optical fiber network. Figure 5 As shown, the method includes:

[0043] Step 501: The MFU sends an equalization delay EqD1 to the first SFU; specifically, the EqD1 is used to instruct the first SFU to send a response message after delaying the EqD1 after starting to receive a data frame;

[0044] Step 502: The MFU starts sending a first data frame to the first SFU through the first optical fiber line at time T0;

[0045] Specifically, starting to send the first data frame refers to sending the first bit of the data frame, wherein the first data frame may be a superframe including a data payload and a frame header. The transmission duration of the superframe is fixed at 125us.

[0046] Step 503: The first SFU is in T sr1 The first data frame is received starting from time;

[0047] Specifically, the starting to receive the first data frame refers to receiving the first bit of the data frame;

[0048] Step 504: The first SFU is at (T sr1 +EqD1) starts sending response messages;

[0049] Specifically, the (T sr1 +EqD1) is equivalent to sending the first bit of the response message after delaying by EqD1 after receiving the first bit of the data frame.

[0050] Step 505: The MFU mr1 receiving a response message sent by the first SFU at the moment;

[0051] Step 506: The MFU f The first data frame is sent at time T f Greater than or equal to T mr1 .

[0052] Using the method of this embodiment, because the optical fiber MFU connecting the MFU to each SFU in the FTTR scenario is short enough, the transmission delay of EqD1 plus the optical fiber line where the first SFU is located is always less than 125us, that is, less than the transmission time of a superframe. Therefore, the MFU can receive the feedback information of the SFU during the transmission of the first data frame, that is, during T f A response message sent by the first SFU is received before the first data frame is sent, so that the back-and-forth interactive information processing efficiency between the MFU and the SFU is higher.

[0053] The embodiment of the present invention further provides a network device, the network device is Figure 6 The MFU shown in . Figure 6 As shown, the network device 60 includes a processor 601, a memory 602, a PON medium access control (MAC) chip 603, and a transceiver 604. The processor 601 can be a general central processing unit (CPU), a microprocessor, an application-specific integrated circuit ASIC, or at least one integrated circuit for executing related programs. Specifically, the processor 601 calculates and obtains the following Figure 3 The RTD1 and RTD2 are obtained, and EqD1 and EqD2 are obtained based on RTD1 and RTD2. Further, the processor cooperates with the memory 602, the PON MAC chip 603 and the transceiver 604 to perform Figure 3 or Figure 4 The method performed by the MFU.

[0054] The memory 602 may be a read-only memory (ROM), a static storage device, a dynamic storage device or a random access memory (RAM). The memory 602 may store an operating system and other application programs. When the technical solution provided by the embodiment of the present invention is implemented by software or firmware, the program code for implementing the technical solution provided by the embodiment of the present invention is stored in the memory 602 and executed by the processor 601.

[0055] The PON MAC chip 603 is responsible for forwarding PON user plane data under the control of the processor 601. The PON MAC chip 603 may include a physical coding sublayer and a MAC control sublayer.

[0056] In one embodiment, the processor 601 may include a memory 602. In another embodiment, the processor 601 and the memory 602 are two independent structures.

[0057] The transceiver 604 may include an optical transmitter and / or an optical receiver. The optical transmitter may be used to send an optical signal, and the optical receiver may be used to receive an optical signal. The optical transmitter may be implemented by a light emitting device, such as a gas laser, a solid laser, a liquid laser, a semiconductor laser, a directly modulated laser, etc. The optical receiver may be implemented by an optical detector, such as a photodetector or a photodiode (such as an avalanche diode), etc. The transceiver 604 may also include a digital-to-analog converter and an analog-to-digital converter. The MFU communicates with the downstream SFU and also communicates with the upstream OLT through the transceiver 604.

[0058] The present invention also provides a FTTR system, which comprises the above Figure 6 The connection relationship between the MFU and at least one SFU is as follows: Figure 3 The FTTR network structure shown will not be repeated here.

[0059] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented by software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive Solid State Disk (SSD)), etc.

Claims

1. A method for allocating delay indication information, characterized in that: include: The master optical fiber unit MFU obtains the round trip delay RTD1 of the optical fiber line between the first SFU and the MFU during the registration phase of the first slave optical fiber unit SFU; The MFU obtains the round trip delay RTD2 of the optical fiber line between the second SFU and the MFU during the registration phase of the second SFU; The MFU specifies equalization delays EqD1 and EqD2 for the first SFU and the second SFU, respectively, wherein RTD1+EqD1=RTD2+EqD2, and the difference between EqD1 and EqD2 is not greater than 12us; The MFU sends the EqD1 to the first SFU and the EqD2 to the second SFU, and instructs the first SFU to delay sending a response message after delaying the EqD1 after starting to receive the data frames sent by the MFU, and instructs the second SFU to delay sending a response message after delaying the EqD2 after starting to receive the data frames sent by the MFU.

2. The method according to claim 1, characterized in that The difference between EqD1 and EqD2 is further not greater than 10 us.

3. The method according to claim 1, characterized in that The difference between EqD1 and EqD2 is further not greater than 7 us.

4. A signal transmission method, characterized in that: include: The master fiber unit MFU sends the equalization delay EqD1 to the first slave fiber unit SFU; Specifically, the EqD1 is used to instruct the first SFU to send a response message after delaying the EqD1 after starting to receive the data frame; The MFU starts sending a first data frame to the first SFU through the first optical fiber line at time T0; The first SFU in T sr1 The first data frame is received starting from time; The first SFU is sr1 +EqD1) starts sending response messages; The MFU is in T mr1 receiving a response message sent by the first SFU at the moment; The MFU is in T f The first data frame is sent at time T f Greater than or equal to T mr1 .

5. The method according to claim 4, characterized in that The first SFU in T sr1 The time at which the first data frame is received is T sr1 The first bit of the first data frame is received at time instant.

6. The method according to claim 4, characterized in that The MFU starting to send the first data frame at time T0 means sending the first bit of the first data frame at time T0.

7. The method according to any one of claims 4 to 6, characterized in that: The first data frame may be a superframe.

8. A network device, characterized in that: It includes a processor 601, a memory 602, a PON media access control chip 603 and a transceiver 604; wherein the memory 602 is used to store program codes, and the processor cooperates with the memory 602, the PON MAC chip 603 and the transceiver 604 to execute the method executed by the MFU according to claim 1.

9. A signal transmission system, characterized in that: The system comprises a master fiber unit MFU as claimed in claim 8 and at least one slave fiber unit SFU.

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