Time delay instruction information allocation method, apparatus, and system

Abstract

Provided in the embodiments of the present invention is a time delay instruction information allocation method, which comprises: in a registration stage of a first SFU, an MFU acquires 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, the MFU acquires a round-trip delay RTD2 of an optical fiber line between the second SFU and the MFU; the MFU respectively specifies equalization delays EqD1 and EqD2 for the first SFU and the second SFU, wherein RTD1+EqD1=RTD2+EqD2, the difference value between the EqD1 and the EqD2 being not greater than 12 μs; and the MFU sends to the first SFU the EqD1 and sends to the second SFU the EqD2, and instructs the first SFU and the second SFU to delay sending a response message by the EqD1 and the EqD2 respectively. Also provided in the embodiments of the present invention are an apparatus and a system. By means of the embodiments of the present invention, MFUs can receive response messages more quickly, thereby improving the processing efficiency for back-and-forth interaction information between MFUs and SFUs.

Description

Method, device and system for allocating delay indication information

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on September 15, 2023, with application number 202311201796.2 and application name “A method, device and system for allocating delay indication information”, the entire contents of which are incorporated by reference into this application.

[0002] This application also claims priority to the Chinese patent application filed with the State Intellectual Property Office on September 28, 2023, with application number 202311282851.5 and application name “A method, device and system for allocating delay indication information”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] 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

[0004] 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 via optical fiber. The sub-gateway provides users with reliable wireless access points (APs), allowing wireless signals to cover every corner of the home. However, the traditional main gateway to sub-gateway connection generally uses the Passive Optical Network (PON) technology protocol. Because PON is a point-to-multipoint fiber optic transmission and access technology, the connecting optical fibers corresponding to different connection points are inconsistent in length, with the maximum difference being close to 20km. The resulting delay is relatively large and may not meet the needs of each AP in the FTTR scenario.

[0005] Summary of the Invention

[0006] 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.

[0007] 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 delay the EqD1 and the EqD2 respectively before sending the response message.

[0008] As an optional embodiment, the difference between EqD1 and EqD2 is further no greater than 39 us, or even no greater than 28 us.

[0009] 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 delay the EqD1 after starting to receive a data frame and then send a response message; 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 starts to send a first data frame to the first SFU at time T1; sr1 The first SFU starts receiving the first data frame at (T sr1 +EqD1) starts sending a response message; the MFU starts sending a response message at T mr1 The MFU receives the 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 .

[0010] 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.

[0011] 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.

[0012] As another optional embodiment, the first data frame may be a superframe.

[0013] 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 code, and the processor cooperates with the memory 602, the PON MAC chip and the transceiver to execute the above-mentioned MFU execution method.

[0014] An embodiment of the present invention further provides a signal transmission system, which includes the above-mentioned master fiber unit MFU and at least one slave fiber unit SFU.

[0015] 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

[0016] FIG1 is a schematic diagram of a PON system architecture provided by the prior art;

[0017] FIG2 is a schematic diagram of a distributed balanced delay provided by the prior art;

[0018] FIG3 is a schematic diagram of the system architecture of an FTTR according to an embodiment of the present invention;

[0019] FIG4 is a flow chart of a method for allocating delay indication information provided in an embodiment of the present invention;

[0020] FIG5 is a flow chart of a signal transmission method provided in an embodiment of the present invention;

[0021] FIG6 is a structural diagram of a network device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] Figure 1 is a schematic diagram of a PON system architecture. As shown in Figure 1, PON system 100 includes at least one OLT 110, at least one ODN 120, and multiple ONUs 130. Specifically, OLT 110 provides a network-side interface for PON system 100, while ONU 130 provides a user-side interface for PON system 100 and is connected to ODN 120. If ONU 130 directly provides user port functions, it is called an optical network terminal (ONT). For ease of description, the ONU 130 mentioned below refers collectively to both ONTs that can directly provide user port functions and ONUs that provide user-side interfaces. ODN 120 is a network composed of optical fibers and passive optical splitters, used to connect OLT 110 and ONU 130 devices and distribute or multiplex data signals between OLT 110 and ONU 130.

[0023] In this PON system 100, the direction from OLT 110 to ONU 130 is defined as the downstream direction, while the direction from ONU 130 to OLT 110 is defined as the upstream direction. In the downstream direction, OLT 110 uses time division multiplexing (TDM) to broadcast downstream data to the multiple ONUs 130 managed by OLT 110. Each ONU 130 only receives data carrying its own identifier. In the upstream direction, multiple ONUs 130 communicate with OLT 110 using time division multiple access (TDMA). Each ONU 130 transmits upstream data according to the time domain resources allocated by OLT 110. Using this mechanism, the downstream optical signal transmitted by OLT 110 is a continuous optical signal, while the upstream optical signal transmitted by ONU 130 is a burst optical signal.

[0024] From the OLT's perspective, the logical distances between each ONU and the OLT vary. The optical signal's transmission time on the fiber varies, and the time it arrives at each ONU varies. Furthermore, the round-trip delay (RTD) between the OLT and the ONU also varies with time and environmental factors. This RTD encompasses both the transmission delay on the line and the device's data processing delay (also known as response delay). To ensure that upstream data sent by each ONU to the OLT is inserted into a designated time slot after converging on the ODN fiber, without collisions or excessive gaps, the OLT must accurately measure the distance between each ONU and the OLT through ranging, thereby controlling the timing of each ONU's upstream data transmission.

[0025] The technical concept of ranging technology is to ensure that the time it takes for each ONU to reach the OLT is the same. Based on this concept, the GPON system uses a method to calculate the OLT-to-ONU delay, using the farthest ONU as a benchmark, and accurately calculate the distance between the two. For closer ONUs, a delay is added to synchronize their arrival time at the OLT with the farthest ONU. The purpose of this added delay is to ensure that the logical distance from all ONUs to the OLT is the same. In other words, from the OLT's perspective, all ONUs have the same transmission distance. This added delay is called equalization delay, and the entire process is called ranging.

[0026] When an ONU registers for the first time, the OLT initiates ranging, obtains the ONU's round-trip delay (RTD), calculates the physical distance of each ONU, and assigns appropriate equalization delay (EqD) parameters based on the ONU's physical distance. During this ranging process, the OLT creates a window, or quiet zone, to suspend the upstream transmission channels of other ONUs. By assigning EqDs to ONUs, the OLT synchronizes the data frames transmitted by each ONU, ensuring that no ONU data conflicts at the optical splitter. This effectively places all ONUs at the same logical distance and transmits data in the corresponding time slots, thus avoiding upstream signal collisions. When selecting the EqD, the OLT first determines the time Tedq between all ONUs reaching the OLT based on the distances to the nearest and farthest ONUs, as well as the ONU's maximum round-trip delay (RTD). The EqD for each line is then calculated using the formula 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 PON cycle.

[0027] GPON ranging is completed during the ONU registration phase. When the ONU receives the SN request message from the OLT, it waits for a certain period of time before returning an SN response message. After receiving and verifying the validity of this response message, the OLT assigns the ONU an ONU-ID. After receiving the assigned ONU-ID, the ONU enters the ranging state.

[0028] The principle of OLT calculation and allocation of balanced delay is shown in Figure 2. Assume that the OLT sends a ranging request to the ONU at time T1, and at the same time orders 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. 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. The zero-distance equivalent delay Teqd in Figure 1 is a value set by the OLT based on the longest optical fiber length, which is greater than or equal to the RTD of the ONU with the longest logical distance. In order 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:

[0029] EqD(i)=Teqd-RTD(i) (Formula 1)

[0030] After processing the OLT's request, 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.

[0031] Traditional PON systems are primarily used in fiber-to-the-home (FTTH) scenarios, where each household has only one optical network unit (ONU). Building on FTTH, to address poor home Wi-Fi coverage, fiber can be extended further into households' homes. Installing an ONU in each room reduces the distance between the user terminal and the ONU, improving signal quality. This application scenario is called fiber-to-the-room (FTTR).

[0032] Figure 3 is a schematic diagram of the FTTR system architecture. FTTR and FTTH networks can be considered two-tier PON systems. In the first-tier PON system (FTTH), the OLT is deployed in the central office, and the ONU is deployed in the home's information box. In the second-tier PON system (FTTR), the OLT can replace the ONU in the FTTH and be deployed in the home's information box. This OLT in the FTTR scenario performs similar functions to the OLT in the FTTH scenario, and it can also perform similar functions to the ONU in the FTTH scenario. In other words, the OLT in the FTTR serves as a network device that connects the FTTH and FTTR networks. The ONU in the FTTR can be deployed in each room of the home to connect to user terminals. These ONUs and FTTH ONUs are essentially the same type of network device. The difference is that in FTTH, the ONU is typically deployed in the information box and is usually separated from the user terminal by an access point (AP). In contrast, the ONU in the FTTR is located in every room and also functions as an AP, enabling direct Wi-Fi connections to user terminals. It should be noted that the OLT in the second-tier PON system (FTTR) can also be referred to as the "master gateway" or "master fiber unit" (MFU), and the ONU can also be referred to as the "slave gateway" or "slave fiber unit" (SFU). Moreover, since the SFU acts as an access point (AP) to provide Wi-Fi connections for STAs, it is also referred to as an AP. This application does not limit the specific names of the above devices.

[0033] Because the maximum transmission distance between the OLT and ONU in traditional PON systems is 20 km, the distance between different ONUs connected to the same OLT can vary by up to 20 km. However, in FTTR scenarios, the typical span of a home is tens of meters, with the largest span exceeding hundreds of meters. Due to the limitations of residential buildings, the maximum distance between multiple SFUs connected to a single MFU within a home is only a few hundred meters. The EqD selection rules used in traditional PON systems may not be applicable to FTTR scenarios.

[0034] Based on this, according to the following calculation formula:

[0035] For FTTR networks, L min The value is 0km, D max 1km,RspTime max The value is 36us. After calculation, T eqd The minimum value can be taken as 36us + 10us = 46us. That is, after the OLT starts sending a signal, it can start receiving the ONU's reply signal at least 46us later.

[0036] An embodiment of the present invention provides a method for distributing delay indication information, which is applied to an optical fiber network. As shown in FIG4 , the method includes:

[0037] 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;

[0038] 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;

[0039] Step 403: The MFU specifies equalization delays EqD1 and EqD2 for the first SFU and the second SFU, respectively, where RTD1 + EqD1 = RTD2 + EqD2, and the difference between EqD1 and EqD2 is no more than 12 μs.

[0040] Specifically, from RTD1+EqD1=RTD2+EqD2, we can see 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 multiple SFUs under an MFU and 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 kilometer, 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 thus the difference between EqD1 and EqD2 will not be greater than 12us;

[0041] 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 delaying the EqD1 after starting to receive the data frame 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 frame sent by the MFU.

[0042] 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 28 us and 39 us, respectively. Similarly, in step 403, it may be further required that the difference between EqD1 and EqD2 is no greater than 7 us, or no greater than 10 us.

[0043] Using this embodiment, after receiving the data frame sent by the MFU, the first and second SFUs within the MFU delay EqD1 and EqD2, respectively, before sending a response message. This ensures that EqD1 or EqD2 arrives at the MFU simultaneously, reducing the waiting delay for the first or second SFU. This allows the MFU to receive the response message more quickly, making the back-and-forth information processing between the MFU and SFU more efficient. The difference between EqD1 and EqD2 of no more than 12 μs reflects a specific analysis of the FTTR networking characteristics, identifying a technical point that can improve the processing efficiency of the fiber optic network. This addresses the demanding response time requirements for home Wi-Fi terminals or applications in FTTR networking.

[0044] An embodiment of the present invention provides a signal transmission method, which is applied to an optical fiber network. As shown in FIG5 , the method includes:

[0045] 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;

[0046] Step 502: The MFU starts sending a first data frame to the first SFU through the first optical fiber line at time T0;

[0047] 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, and the transmission duration of the superframe is fixed at 125 μs.

[0048] Step 503: The first SFU is in T sr1 The first data frame is received starting at time;

[0049] Specifically, the starting to receive the first data frame refers to receiving the first bit of the data frame;

[0050] Step 504: The first SFU is sr1 +EqD1) Start sending response messages;

[0051] Specifically, the (T sr1 Starting to send the response message at time +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.

[0052] Step 505: The MFU is in T mr1 Receive a response message sent by the first SFU at the moment;

[0053] Step 506: The MFU is in T f The first data frame is sent at time T f Greater than or equal to T mr1 .

[0054] 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 period of sending the first data frame, that is, during the period of T f The 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.

[0055] An embodiment of the present invention also provides a network device, which is the MFU shown in Figure 6. As shown in Figure 6, the network device 60 includes modules such as a processor 601, a memory 602, a PON medium access control (MAC) chip 603, and a transceiver 604. The processor 601 can adopt a general central processing unit (CPU), a microprocessor, an application-specific integrated circuit ASIC, or at least one integrated circuit to execute relevant programs. Specifically, the processor 601 calculates and obtains RTD1 and RTD2 as shown in Figure 3, and obtains EqD1 and EqD2 based on RTD1 and RTD2. Furthermore, the processor cooperates with the memory 602, the PON MAC chip 603, and the transceiver 604 to execute the method executed by the MFU shown in Figure 3 or Figure 4.

[0056] 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 solutions provided by the embodiments of the present invention are implemented using software or firmware, the program code for implementing the technical solutions provided by the embodiments of the present invention is stored in the memory 602 and executed by the processor 601.

[0057] 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.

[0058] 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.

[0059] The transceiver 604 may include an optical transmitter and / or an optical receiver. The optical transmitter may be used to transmit optical signals, and the optical receiver may be used to receive optical signals. The optical transmitter may be implemented using a light-emitting device, such as a gas laser, a solid-state laser, a liquid laser, a semiconductor laser, a directly modulated laser, or the like. The optical receiver may be implemented using a photodetector, such as a photodetector or a photodiode (e.g., an avalanche diode). 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 with the upstream OLT via the transceiver 604.

[0060] The present invention further provides an FTTR system, which includes the MFU described in FIG6 and at least one SFU. The connection relationship between the MFU and the SFU is shown in the FTTR network structure in FIG3 and will not be described in detail.

[0061] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments can be implemented 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, all or part of the processes or functions described in the embodiments of the present invention are generated. 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 one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that includes one or more available media. 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 (SSD)).

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 no 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 shown in claim 8 and at least one slave fiber unit SFU.

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