A cascaded passive optical network system, device and medium for FTTR scenarios

Abstract

The present invention provides a cascaded passive optical network system for FTTR scenarios, and relates to the technical field of passive optical networks. The system is composed of an access network PON and n home PONs; the access network PON includes an access network OLT and n access network ONUs, and each access network ONU is connected to a home OLT and m home ONUs; the access network PON and the home PON both adopt the protocol stack of the TDM-PON of the ITU-T standard, including the SDU layer, the TC layer and the PMD layer; the FS sublayer containing the dynamic bandwidth allocation function in the home OLT and the higher SA sublayer and SDU layer are all transferred to the service data unit layer of the access network OLT. The present invention facilitates later maintenance and greatly reduces the cost of deployment. When the uplink and downlink data pass through the gateway, the data will not undergo a cumbersome decapsulation and encapsulation process, which also facilitates centralized resource scheduling and management; based on the present invention, operators can flexibly customize global management and control solutions according to their own requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of passive optical networks, and in particular to a cascaded passive optical network system, device and medium for FTTR scenarios. Background Art

[0002] As the scale of home network services continues to expand, the single-layer passive optical network (PON) access solution based on fiber-to-the-home (FTTH) is gradually unable to meet the needs of home users for bandwidth and service quality. As the fiber-to-the-room (FTTR) scenario as an extension of FTTH is proposed, a two-layer cascaded PON system that combines FTTR and FTTH scenarios has emerged. This system can provide users with a stable and high-speed network experience and richer network services, but it increases the deployment cost of the home network. Therefore, a centralized cascaded PON concept is proposed, which is to move the home network function upward and directly control the data transmission of each home node through the optical line terminal (OLT) in the access network. This concept reduces costs by simplifying the functions of the home PON network, and thereby solves the problem of large-scale deployment of FTTR.

[0003] Due to the high cost of OLT, the existing cascade PON solution is unaffordable for cost-sensitive home networks. On this basis, some people have proposed to cut and move some functions of the transmission convergence layer (TC layer) originally belonging to the home OLT to the access network OLT. This solution is beneficial to both operators and users: on the one hand, due to the upward migration of functions, operators do not need to frequently dispatch maintenance personnel to users' homes, which saves a lot of labor costs; on the other hand, the simplification of home OLT functions can also reduce the complexity of the equipment, thereby reducing the failure rate and reducing equipment costs. We call this solution a centralized cascade PON solution.

[0004] In the protocol stack of time-division multiplexing PON (TDM-PON) based on the ITU-T protocol, the TC layer of OLT and optical network unit (ONU) is divided into three sublayers: service adaptation sublayer (SA sublayer), framing sublayer (FS sublayer) and PHY adaptation sublayer (PHY adaptation sublayer). Since the cascaded PON is based on TDM-PON, the upward migration of functions should be selected among the three sublayers. However, the industry has not reached a unified understanding on the choice of home OLT function division, nor has there been a specific feasible solution. Summary of the invention

[0005] To this end, the embodiments of the present invention provide a cascaded passive optical network system, device and medium for FTTR scenarios, which are used to solve the problems in the prior art that the cascaded PON system is too expensive, the centralized cascaded PON is still in the conceptual stage, and there is a lack of specific functional segmentation solutions and protocol stack structure design.

[0006] In order to solve the above problems, an embodiment of the present invention provides a cascaded passive optical network system for FTTR scenarios, including:

[0007] The system consists of an access network PON and n home PONs, where PON stands for Passive Optical Network;

[0008] The access network PON includes an access network OLT and n access network ONUs, each access network ONU is connected to a home OLT and m home ONUs, where OLT stands for optical line terminal and ONU stands for optical network unit;

[0009] The access network PON and the home PON both adopt the TDM-PON protocol stack of the ITU-T standard, including an SDU layer, a TC layer and a PMD layer, wherein the SDU layer represents a service data unit layer, the TC layer represents a transmission convergence layer, and the PMD layer represents a physical medium dependent layer;

[0010] The FS sublayer containing the dynamic bandwidth allocation function in the home OLT and the higher SA sublayer and SDU layer are all transferred to the service data unit layer of the access network OLT, where the FS sublayer represents the framing sublayer and the SA sublayer represents the service adaptation sublayer;

[0011] Among them, the PON that carries the fiber-to-the-home function is called the access network PON, the PON that carries the fiber-to-the-room function is called the home PON, the OLT and ONU in the access network PON are called the access network OLT and access network ONU respectively, the OLT and ONU in the home PON are called the home OLT and home ONU, and the access network ONU and the corresponding home OLT together constitute the home gateway.

[0012] Preferably, the SDU layer includes a user data function and an ONU management and control interface, wherein the user data function is responsible for encapsulating data frames into SDU frames, and the ONU management and control interface is responsible for generating OMCI messages.

[0013] Preferably, the TC layer includes an SA sublayer, a FS sublayer and a PHY sublayer, wherein the PHY sublayer stands for a physical interface adaptation sublayer.

[0014] Preferably, the data encapsulation process in the protocol stack specifically includes:

[0015] In the upstream transmission, at the SDU layer of the home ONU, the user data function is responsible for encapsulating data frames into SDU frames, while the ONU management and control interface is responsible for generating OMCI messages for the OLT to establish cross-ONU connections and perform control and management functions;

[0016] When the SDU frames and OMCI messages enter the TC layer, they are first encapsulated into XGEM frames by the SA sublayer; then when the SDU frames and OMCI messages pass through the FS sublayer, the XGEM frames from each home ONU are aggregated into a FS burst frame, called the home FS burst;

[0017] Then the home FS burst is forward error corrected and scrambled in the PHY sublayer, and the home FS burst is encapsulated into a PHY burst. After the PHY burst that reaches the home OLT is decoded in the PHY sublayer, the home OLT determines whether the traffic carried by the PHY burst is NS traffic, OMCI message, or EW traffic;

[0018] Among them, the PHY sublayer stands for the physical interface adaptation sublayer, NS traffic refers to the traffic between the access network OLT and the home ONU, and EW traffic refers to the traffic forwarded between each home ONU in a home PON;

[0019] Finally, relying on the functions that are moved up to the SDU layer, the access network OLT performs secondary unpacking of the home FS burst to obtain the original home XGEM frame.

[0020] Preferably, the data encapsulation process in the protocol stack specifically includes:

[0021] In the downstream transmission, NS traffic is encapsulated twice in the access network OLT and decapsulated in the access network ONU and home ONU respectively. For the EW traffic that has been uploaded to the buffer of the home OLT, they will be forwarded to the corresponding home ONU in the time slot allocated by the access network OLT in the form of FS burst.

[0022] Preferably, in a centralized bandwidth scheduling mechanism, when the report message is uploaded to the access network OLT for the first time, the DBA module will allocate upstream bandwidth for the home PON and the access network PON at the same time, and send these authorization messages to the access network ONU and the home PON in the same cycle; when the NS traffic reaches the access network ONU, the access network ONU directly uploads it according to the authorization message in the BW-map field without the need for a secondary report; wherein, the NS traffic refers to the traffic between the access network OLT and the home ONU.

[0023] Preferably, the BW-map field in the downlink frame is modified, specifically including:

[0024] The BWmap field of the home ONU is called the Home BWmap field, and the BWmap field of the access network ONU is called the AccessBWmap field. The Home BWmap field contains N H allocation structure, N H Indicates the number of home ONUs in the home PON. Each allocation structure corresponds to one home ONU. In the Access BWmap field, each allocation structure corresponds to one home PON.

[0025] Preferably, in the Access BWmap field, the allocation structure includes the start time NS-ST, EW-ST, and length NS-GS, EW-GS of the burst of the two types of traffic forwarded from the home ONU to the home OLT; wherein the ST and GS fields include not only the authorization message of the traffic forwarded by the gateway, i.e., Access NS / EW-ST and Access NS / EW-GS, but also the authorization information of the traffic received from the home ONU, i.e., Home NS / EW-ST and Home NS / EW-GS.

[0026] An embodiment of the present invention also provides an electronic device, which includes a processor, a memory and a bus system, wherein the processor and the memory are connected through the bus system, the memory is used to store instructions, and the processor is used to execute the instructions stored in the memory to implement any of the above-mentioned cascaded passive optical network systems for FTTR scenarios.

[0027] An embodiment of the present invention further provides a computer storage medium storing a computer software product. The computer software product includes several instructions for enabling a computer device to execute the above-mentioned cascaded passive optical network system for FTTR scenarios.

[0028] It can be seen from the above technical solutions that the present invention has the following advantages:

[0029] The embodiments of the present invention provide a cascaded passive optical network system, device and medium for FTTR scenarios. The functions of the home OLT of the system of the present invention are greatly simplified, which reduces the deployment cost and the failure rate of the OLT, making it convenient for later maintenance. At the same time, the protocol stacks of the deployed access network ONU and home ONU are not changed, so the access network ONU does not need to be replaced, which can also greatly reduce the deployment cost. In addition, when the uplink and downlink data pass through the gateway, the data will not undergo cumbersome decapsulation and encapsulation processes, which also facilitates centralized resource scheduling and management. Finally, based on this system, operators can flexibly customize global management and control solutions according to their own requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the implementation cases of the present invention or the technical solutions in the prior art, the following is a brief description of the drawings required for use in the embodiments. By referring to the drawings, the features and advantages of the present invention will be more clearly understood. The drawings are schematic and should not be understood as limiting the present invention in any way. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0031] Figure 1 A block diagram of a cascaded passive optical network system for FTTR scenarios provided in an embodiment;

[0032] Figure 2 Schematic diagram of the uplink centralized bandwidth scheduling mechanism in the embodiment;

[0033] Figure 3 Schematic diagram of a downlink centralized bandwidth scheduling mechanism in an embodiment;

[0034] Figure 4 This is a schematic diagram of the structure of a downlink frame BW-map in the embodiment;

[0035] Figure 5 It is a schematic diagram of simulation results in the embodiment, Figure 5 (a) is the average delay of upstream NS traffic in the access network PON, Figure 5 (b) Average downlink delay of EW traffic. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Embodiment 1

[0038] like Figure 1 As shown, an embodiment of the present invention proposes a cascaded passive optical network system for FTTR scenarios, the system comprising:

[0039] The system consists of an access network PON and n home PONs, where PON stands for Passive Optical Network;

[0040] The access network PON includes an access network OLT and n access network ONUs, each access network ONU is connected to a home OLT and m home ONUs, where OLT stands for optical line terminal and ONU stands for optical network unit;

[0041] The access network PON and the home PON both adopt the TDM-PON protocol stack of the ITU-T standard, including an SDU layer, a TC layer and a PMD layer, wherein the SDU layer represents a service data unit layer, the TC layer represents a transmission convergence layer, and the PMD layer represents a physical medium dependent layer;

[0042] The FS sublayer containing the dynamic bandwidth allocation function in the home OLT and the higher SA sublayer and SDU layer are all transferred to the service data unit layer of the access network OLT, where the FS sublayer represents the framing sublayer and the SA sublayer represents the service adaptation sublayer;

[0043] Among them, the PON that carries the fiber-to-the-home function is called the access network PON, the PON that carries the fiber-to-the-room function is called the home PON, the OLT and ONU in the access network PON are called the access network OLT and access network ONU respectively, the OLT and ONU in the home PON are called the home OLT and home ONU, and the access network ONU and the corresponding home OLT together constitute the home gateway.

[0044] It can be seen from the above technical solution that the present invention proposes a cascaded passive optical network system for FTTR scenarios. The functions of the home OLT of the present invention are greatly simplified, which reduces the deployment cost and the failure rate of the OLT, making it convenient for later maintenance. At the same time, the protocol stacks of the deployed access network ONU and home ONU are not changed, so the access network ONU does not need to be replaced, which can also greatly reduce the deployment cost; in addition, when the uplink and downlink data pass through the gateway, the data will not undergo cumbersome decapsulation and encapsulation processes, which also facilitates centralized resource scheduling and management; finally, based on this system, operators can flexibly customize global management and control solutions according to their own requirements.

[0045] The following is a detailed description of the data encapsulation process in the protocol stack. Taking uplink transmission as an example, at the SDU layer of the home ONU, the user data function is responsible for encapsulating data frames into SDU frames, while the ONU management and control interface (OMCI) is responsible for generating OMCI messages for the OLT to establish cross-ONU connections and perform control and management functions.

[0046] When SDU frames and OMCI messages enter the TC layer, they are first encapsulated into XGEM frames by the Service Adaptation (SA) sublayer. When they pass through the FS sublayer, the XGEM frames from each home ONU are aggregated into a FS burst frame, called the home FS burst.

[0047] After that, the home FS burst is forward error corrected (FEC) encoded and scrambled in the PHY adaptation sublayer, and the FS burst is encapsulated into a PHY burst. This step is to prepare for data transmission to the home OLT through the PMD layer. After the PHY burst arriving at the home OLT is decoded in the PHY adaptation sublayer, the home OLT will determine whether the traffic carried by the PHY burst is NS traffic (or OMCI message) or EW traffic. The PHY burst containing NS traffic and OMCI message is uploaded to the access network ONU by its related home OLT. Since the FS and SA sublayer functions are removed from the TC layer of the home OLT, the PHY burst is only decoded into a FS burst in the home OLT without further processing. In the access network ONU, the FS burst is treated as an SDU frame for secondary encapsulation, and then a new FS burst is formed. For distinction, this burst is called the access network FS burst of NS traffic. After passing through the TC layer of the access network OLT, the access network FS burst is decoded into each home FS burst.

[0048] Finally, relying on the functions that are moved up to the SDU layer, the access network OLT performs secondary unpacking of the home FS burst to obtain the original home XGEM frame. For EW traffic that is only forwarded within the home PON, the home OLT will temporarily store it in its own buffer.

[0049] In the downstream transmission, NS traffic is encapsulated twice in the access network OLT and decapsulated in the access network ONU and home ONU respectively. For the EW traffic (in the form of FS burst) that has been uploaded to the buffer of the home OLT, they will be forwarded to the corresponding home ONU in the time slot allocated by the access network OLT.

[0050] In traditional TDM-PON based on ITU-T protocol, the downstream frame of OLT is periodically broadcast to all ONUs every 125 microseconds, which contains a BW-map field for allocating bandwidth to ONUs. The BW-map field provides the start time and length of each ONU's time slot to ensure that the bursts they send do not conflict. In response, the upstream burst uploaded from the ONU to the OLT contains a DBRu field, which contains information about the current ONU buffer occupancy. The OLT then calculates the new BW-map for upstream transmission in the next cycle based on these DBRu fields. The above mechanism is called the status report (SR) mechanism, which is a key component of the upstream scheduling mechanism. It is similar to traditional PON.

[0051] The bandwidth of the access network PON and home PON in the centralized cascade PON system is also scheduled in this way. In the upstream direction, based on the report message previously received from the home ONU, the access network OLT calculates the bandwidth allocated to each home ONU in the DBA module and stores it in the BW-map field of the downstream frame sent every 125 microseconds. Subsequently, the BW-map is broadcast to the home ONU along with the downstream frame and finally received by the home ONU.

[0052] In order to facilitate the separation of NS traffic and EW traffic in the home OLT, the home ONU will upload the bursts of NS and EW traffic separately. Since the TC layer function of the home OLT is simplified, a TDM switch is required in the home OLT to achieve separate transmission. When an upstream polling cycle begins, the switch first opens the path to the access network, and at the same time, the NS bursts of all home ONUs are uploaded and stored in the buffer of the access network ONU. After that, the NS burst will be uploaded to the access network OLT after secondary packaging at the time specified by the BW-map. Once all NS bursts are uploaded, the switch is closed. Then, the EW burst uploaded by the home ONU will be stored in the buffer of the home OLT and forwarded inside the home PON.

[0053] Although cascaded PONs still use the SR mechanism, there are still significant differences between distributed and centralized bandwidth scheduling mechanisms. If a distributed bandwidth scheduling mechanism is adopted, the DBA module at the TC layer that schedules the bandwidth of the access network PON cannot predict the buffer occupancy of the access network ONU in advance. Therefore, after transmitting NS traffic from the home PON to the access network ONU, the access network ONU needs to first upload a report message (ie, the DBRu field), and only after receiving the next authorization message (ie, the BW-map field) from the access network OLT can it upload NS traffic.

[0054] In contrast, in a centralized bandwidth scheduling mechanism, such as Figure 2 As shown in the figure, when the report message is first uploaded to the access network OLT, the DBA module will allocate upstream bandwidth for the home PON and the access network PON at the same time, and send these authorization messages to the access network ONU and the home PON in the same cycle. When the NS traffic reaches the access network ONU, the access network ONU can directly upload according to the authorization message in the BW-map without the need for a second report. Therefore, compared with the distributed bandwidth scheduling mechanism, the centralized bandwidth scheduling mechanism can reduce the NS traffic delay by at least one cycle.

[0055] Figure 3 The centralized bandwidth scheduling mechanism for downstream is shown. During downstream transmission, NS traffic from the same home PON is encapsulated before entering the TC layer of the access network OLT, and is re-encapsulated into FS frames. In the residential gateway, when the access network ONU receives data belonging to its home PON, the home OLT generates a new downstream frame and broadcasts it to all associated home ONUs. As for EW traffic, if a distributed bandwidth scheduling mechanism is adopted, the DBA module of the access network PON cannot predict the downstream transmission time of the EW burst, and the home OLT has no scheduling capability, so the EW burst may conflict with the regularly sent NS downstream frames. Therefore, the home OLT needs to temporarily store the EW burst after receiving it. In the home PON, there is a blank time slot between two NS downstream frames, which can be used to forward the EW burst, which we call the EW transmission window. It should be noted that if the transmission window is not enough to transmit the next EW burst, it is necessary to wait for the new EW transmission window to appear before transmitting the burst. If a centralized scheduling mechanism is adopted, the above functions can be easily realized.

[0056] In order to adapt to the centralized bandwidth scheduling mechanism, this scheme also modifies some frame structures based on the ITU-T protocol. In the home PON, the only difference between the frame structures of the NS burst and the EW burst is the DBRu field. Since the home OLT cannot process the report message, the report message of the EW traffic should be uploaded to the access network OLT. Therefore, the DBRu field of the NS burst contains the report messages from both NS and EW traffic, while the DBRu field of the EW burst is removed. In addition, since the report message is already included in the home FS burst of the home ONU, the access network ONU that is only responsible for forwarding NS traffic does not require additional bandwidth requests. Therefore, during the encapsulation process of the access network ONU, the DBRu field is not added to the access FS burst of NS traffic.

[0057] For the downstream frames of NS traffic, the OLT will add different BW-map fields in the two frame sublayer encapsulation processes. Since the downstream frame only undergoes decapsulation once when passing through the gateway, the access network ONU and the home ONU will each receive a BW-map field and encapsulate them in different TC layers. Therefore, the design of the content in the two BW-map fields is crucial to the implementation of the centralized bandwidth scheduling mechanism. If both BW-map fields contain all the authorization messages for the burst from the home PON to the access network PON, the redundant messages will increase unnecessary frame overhead. Therefore, we modified the BW-map field in the downstream frame, and its content is as follows: Figure 4 shown.

[0058] The BWmap field of the home ONU is called the Home BWmap field, and the BWmap field of the access network ONU is called the AccessBWmap field. The Home BWmap field contains N H Allocation Structure (AS), N H Indicates the number of home ONUs in the home PON, and each AS corresponds to one home ONU. Since the AS contains the start time (NS-ST, EW-ST) and length (NS-GS, EW-GS) of the burst of two types of traffic forwarded from the home ONU to the home OLT, the home ONU can upload the data authorized by the access network OLT at the specified time.

[0059] In the Access BWmap field, each AS corresponds to a home PON. Since the gateway needs to control the TDM switch in the home OLT to separate the two types of traffic, the StartTime (ST) and GrantSize (GS) fields contain not only the authorization information of the traffic forwarded by the gateway (i.e., Access NS / EW-ST and Access NS / EW-GS), but also the authorization information of the traffic received from the home ONU (i.e., Home NS / EW-ST and Home NS / EW-GS), as shown in Figure 2. Figure 4 After decoding the AccessBWmap field in the gateway, the home OLT can control the TDM switch to filter the received traffic according to the authorization information it contains.

[0060] In order to verify the efficiency of the proposed system using a centralized bandwidth scheduling mechanism, we used matlab software to perform simulation tests. In the simulation, we simulated a centralized cascade PON network, which includes an XGS-PON as an access network PON (upstream and downstream rates are 10Gb / s) and 32 G-PONs as home PONs (upstream and downstream rates are 1.25Gb / s and 2.5Gb / s, respectively). The physical distance between the access network OLT and the access network ONU is set to 20 kilometers, and in each home PON, the distance between the home ONU and the home OLT is 200 meters. The SDU frame size ranges from 64 bytes to 1518 bytes. In addition, we chose Poisson flow as the arrival model for NS and EW traffic.

[0061] We assume that all home ONUs in the home PON have the same arrival rate, resulting in a 1:1 ratio of NS traffic to EW traffic. In addition, the load of downstream traffic is consistent with the upstream load in the simulation.

[0062] In the simulation, we considered four types of T-CONTs. Since T-CONT 1 receives a fixed bandwidth, it is not controlled by the DBA during bandwidth allocation, so its performance is not analyzed. The bandwidth ratio of the other three T-CONTs is 1:1:0.8.

[0063] The simulation results are as follows Figure 5 As shown, from Figure 5 (a) It can be seen that the NS uplink traffic of the three types of T-CONTs has a delay of about 100 to 200 microseconds in the access network. Considering the data transmission delay of 100 microseconds (calculated at 5 microseconds per kilometer) and the processing delay (35 microseconds), the NS traffic should be uploaded in one uplink cycle in the access network without any additional waiting time or congestion. It can be seen that the centralized bandwidth scheduling mechanism can reduce the waiting delay of NS traffic. Figure 5(b) It can be seen that the latency of the EW downstream traffic of the three T-CONTs is approximately between 190 and 240 microseconds. Considering that there is a time difference (no more than 125 microseconds) and a processing delay (35 microseconds) between the downstream EW window and the upstream frame, the waiting delay of the data is within one cycle. Therefore, this result proves that the EW traffic of the home OLT in each cycle can be forwarded to the corresponding home ONU in time within the EW window of the next cycle.

[0064] Embodiment 2

[0065] The embodiment of the present invention further provides an electronic device, the electronic device comprising a processor, a memory and a bus system, the processor and the memory are connected via the bus system, the memory is used to store instructions, and the processor is used to execute the instructions stored in the memory to implement the above-mentioned cascaded passive optical network system for FTTR scenarios. To avoid redundancy, it will not be repeated here.

[0066] Embodiment 3

[0067] An embodiment of the present invention further provides a computer storage medium storing a computer software product. The computer software product includes several instructions for enabling a computer device to execute the above-mentioned cascaded passive optical network system for FTTR scenarios.

[0068] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0069] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0070] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0071] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A cascaded passive optical network system for FTTR scenarios, characterized in that: include: The system consists of an access network PON and n home PONs, where PON stands for Passive Optical Network; The access network PON includes an access network OLT and n access network ONUs, each access network ONU is connected to a home OLT and m home ONUs, where OLT stands for optical line terminal and ONU stands for optical network unit; The access network PON and the home PON both adopt the TDM-PON protocol stack of the ITU-T standard, including an SDU layer, a TC layer and a PMD layer, wherein the SDU layer represents a service data unit layer, the TC layer represents a transmission convergence layer, and the PMD layer represents a physical medium dependent layer; The FS sublayer containing the dynamic bandwidth allocation function in the home OLT and the higher SA sublayer and SDU layer are all transferred to the service data unit layer of the access network OLT, where the FS sublayer represents the framing sublayer and the SA sublayer represents the service adaptation sublayer; Among them, the PON that carries the fiber-to-the-home function is called the access network PON, the PON that carries the fiber-to-the-room function is called the home PON, the OLT and ONU in the access network PON are called the access network OLT and access network ONU respectively, the OLT and ONU in the home PON are called the home OLT and home ONU, and the access network ONU and the corresponding home OLT together constitute the home gateway.

2. The cascaded passive optical network system for FTTR scenarios according to claim 1, characterized in that: The SDU layer includes a user data function and an ONU management and control interface. The user data function is responsible for encapsulating data frames into SDU frames, and the ONU management and control interface is responsible for generating OMCI messages.

3. The cascaded passive optical network system for FTTR scenarios according to claim 1, characterized in that: The TC layer includes an SA sublayer, a FS sublayer and a PHY sublayer, wherein the PHY sublayer stands for a physical interface adaptation sublayer.

4. The cascaded passive optical network system for FTTR scenarios according to claim 1, characterized in that: The data encapsulation process in the protocol stack specifically includes: In the upstream transmission, at the SDU layer of the home ONU, the user data function is responsible for encapsulating data frames into SDU frames, while the ONU management and control interface is responsible for generating OMCI messages for the OLT to establish cross-ONU connections and perform control and management functions; When the SDU frames and OMCI messages enter the TC layer, they are first encapsulated into XGEM frames by the SA sublayer; then when the SDU frames and OMCI messages pass through the FS sublayer, the XGEM frames from each home ONU are aggregated into a FS burst frame, called home FSburst; Then the home FS burst is forward error corrected and scrambled in the PHY sublayer, and the home FS burst is encapsulated into a PHYburst. After the PHY burst that reaches the home OLT is decoded in the PHY sublayer, the home OLT determines whether the traffic carried by the PHY burst is NS traffic, OMCI message, or EW traffic; Among them, the PHY sublayer stands for the physical interface adaptation sublayer, NS traffic refers to the traffic between the access network OLT and the home ONU, and EW traffic refers to the traffic forwarded between each home ONU in a home PON; Finally, relying on the functions that are moved up to the SDU layer, the access network OLT performs secondary unpacking of the home FS burst to obtain the original home XGEM frame.

5. The cascaded passive optical network system for FTTR scenarios according to claim 1, characterized in that: The data encapsulation process in the protocol stack specifically includes: In the downstream transmission, NS traffic is encapsulated twice in the access network OLT and decapsulated in the access network ONU and home ONU respectively. For the EW traffic that has been uploaded to the buffer of the home OLT, they will be forwarded to the corresponding home ONU in the time slot allocated by the access network OLT in the form of FS burst.

6. The cascaded passive optical network system for FTTR scenarios according to claim 1, characterized in that: In the centralized bandwidth scheduling mechanism, when the report message is uploaded to the access network OLT for the first time, the DBA module will allocate upstream bandwidth for the home PON and the access network PON at the same time, and send these authorization messages to the access network ONU and the home PON in the same cycle; when the NS traffic reaches the access network ONU, the access network ONU directly uploads it according to the authorization message in the BW-map field without the need for a second report; among them, NS traffic refers to the traffic between the access network OLT and the home ONU.

7. The cascaded passive optical network system for FTTR scenarios according to claim 1, characterized in that: Modify the BW-map field in the downlink frame, including: The BWmap field of the home ONU is called the Home BWmap field, and the BWmap field of the access network ONU is called the AccessBWmap field. The Home BWmap field contains N H allocation structure, N H Indicates the number of home ONUs in the home PON. Each allocation structure corresponds to one home ONU. In the Access BWmap field, each allocation structure corresponds to one home PON.

8. The cascaded passive optical network system for FTTR scenarios according to claim 7, characterized in that: In the Access BWmap field, the allocation structure includes the start time NS-ST, EW-ST, and length NS-GS, EW-GS of the burst of the two types of traffic forwarded from the home ONU to the home OLT; the ST and GS fields include not only the authorization information of the traffic forwarded by the gateway, namely Access NS / EW-ST and Access NS / EW-GS, but also the authorization information of the traffic received from the home ONU, namely Home NS / EW-ST and Home NS / EW-GS.

9. An electronic device, characterized in that: The electronic device includes a processor, a memory and a bus system, the processor and the memory are connected through the bus system, the memory is used to store instructions, and the processor is used to execute the instructions stored in the memory to implement the cascaded passive optical network system for FTTR scenarios as described in any one of claims 1 to 8.

10. A computer storage medium, characterized in that: The computer storage medium stores a computer software product, and the computer software product includes several instructions for enabling a computer device to execute the cascaded passive optical network system for FTTR scenarios as described in any one of claims 1 to 8.

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