CN117201976B - Bandwidth allocation method and system for cascade passive optical network - Google Patents

Abstract

The present invention relates to a bandwidth allocation method and system for a cascade passive optical network, the method comprising: step S1: in a centralized cascade PON, calculating the available upstream bandwidth of each home PON, and optimizing the upstream bandwidth calculation process of each home PON; step S2: allocating the calculated available upstream bandwidth of each home PON to the T-CONT of each home PON, completing the allocation of the upstream bandwidth, step S3: in the centralized cascade PON, calculating the available downstream bandwidth of each home PON, optimizing the downstream bandwidth calculation process of each home PON, and completing the allocation of the downstream bandwidth. The present invention can allocate bandwidth for both east-west (EW) traffic and north-south (NS) traffic in the centralized cascade PON, and optimize the process of allocating bandwidth, achieving higher bandwidth utilization and higher efficiency.

Description

A bandwidth allocation method and system for cascaded passive optical networks

Technical Field

The present invention relates to the technical field of bandwidth allocation of passive optical networks, and in particular to a bandwidth allocation method and system for cascaded passive optical networks.

Background Art

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 centralized cascade PON architecture has attracted much attention, that is, the home network function is moved up and the data transmission of each home node is directly controlled by the optical line terminal (OLT) in the access network. This architecture reduces the deployment cost by simplifying the functions of the home PON network, and solves the problem of large-scale deployment of FTTR.

In the cascade PON, the PON that carries the FTTH function is called the access network PON, and the PON that carries the FTTR 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. Similarly, the OLT and ONU in the home PON are called the home OLT and home ONU. The home gateway is composed of the access network ONU and the corresponding home OLT. In addition, in the cascade PON, data traffic is divided into two types, namely North-south (NS) traffic and East-west (EW) traffic. The former refers to the traffic between the access network OLT and the home ONU, and the latter refers to the traffic forwarded between each home ONU in a home PON. Considering that home data involves privacy, EW traffic is only forwarded within the home PON and will not be uploaded to the access network.

Compared with the traditional cascade PON, the characteristics of the centralized cascade PON are mainly reflected in the following two points: first, the access network OLT centrally controls the resource scheduling of each home ONU in the home PON; second, the home OLT in the gateway is responsible for following the instructions of the access network OLT to complete forwarding, storage, and filtering traffic. In order to realize resource scheduling in PON, the dynamic bandwidth allocation (DBA) mechanism is indispensable. The realization of centralized cascade PON requires a DBA mechanism that combines home PON and access network PON, which has not been studied yet.

In traditional time division multiplexing PON (TDM-PON), transport containers (T-CONTs) are used as entities to carry traffic, and they are divided into four types, namely T-CONT 1 (T1), T-CONT 2 (T2), T-CONT 3 (T3), and T-CONT 4 (T4). Each type of T-CONT is responsible for carrying traffic of different priorities, and the priorities correspond to T1 to T4 from high to low. The upstream bandwidth is allocated to these T-CONTs through the DBA mechanism. In centralized cascade PON, in order to allocate bandwidth to NS and EW traffic respectively, home ONUs need to store these two types of traffic in different T-CONTs. These T-CONTs are called NS T-CONTs and EW T-CONTs, and they each contain four priorities. However, the current DBA algorithm can only allocate bandwidth for traditional NS traffic, and does not consider the bandwidth allocation of EW traffic.

In addition, most of the existing DBA algorithms designed for single-stage PONs are based on a single polling allocation mechanism, that is, a maximum number of allocated bytes (AB) is pre-calculated and bandwidth is allocated to each T-CONT once within a fixed time interval (SI). Assume that the kth T-CONT of the jth type (j∈{1,2,3,4}) has a bandwidth request The corresponding AB is AB _k . In this case, the bandwidth allocated to the T-CONT Calculated by:

Each T-CONT has only one chance to obtain bandwidth in a polling cycle. However, in a centralized cascade PON system with many home ONU nodes, this allocation strategy may cause some T-CONTs in the ONU to fail to obtain sufficient bandwidth, while the bandwidth allocated to other T-CONTs is wasted. Therefore, an efficient DBA method suitable for centralized cascade PON architecture is urgently needed.

The existing DBA mechanisms designed for traditional PON architectures are not applicable to centralized cascaded PONs because they only allocate bandwidth for the four T-CONT types that carry NS traffic, without considering EW traffic. Existing DBA algorithms are only applicable to single-layer PONs and cannot be applied to centralized cascaded PON systems with access network PONs and multiple home PONs. In addition, traditional DBA algorithms have low bandwidth utilization in FTTR scenarios and their performance cannot meet home business needs.

Summary of the invention

Therefore, the technical problem to be solved by the present invention is to overcome the problem that the DBA bandwidth allocation mechanism of the passive optical network in the prior art only considers the NS traffic and ignores the EW traffic, and the allocation efficiency is low.

In order to solve the above technical problems, the present invention provides a bandwidth allocation method for a cascaded passive optical network, comprising:

Step S1: in a centralized cascade PON, calculating the available upstream bandwidth of each home PON, and optimizing the upstream bandwidth calculation process of each home PON, wherein the centralized cascade PON includes an access network PON and several home PONs, the access network PON includes an access network OLT and several access network ONUs, each of the home PONs includes several home OLTs with the same number as the access network ONUs, each of the home OLTs includes several home ONUs, the access network OLT is connected to several access network ONUs, each of the access network ONUs is connected to a corresponding home OLT, and each home OLT is connected to several home ONUs;

Step S2: Allocate the calculated available upstream bandwidth of each home PON to the T-CONT of each home PON to complete the allocation of upstream bandwidth, wherein the T-CONT is a transmission container set in each home ONU for carrying traffic;

Step S3: in the centralized cascade PON, the available downstream bandwidth of each home PON is calculated, the downstream bandwidth calculation process of each home PON is optimized, and the downstream bandwidth allocation is completed.

In one embodiment of the present invention, the method for calculating the available upstream bandwidth of each home PON in step S1 includes:

First, according to the ratio of NS traffic to EW traffic, the total bandwidth in an uplink frame is divided into the available bandwidth for NS traffic and available bandwidth for EW traffic The NS traffic is the traffic between the access network OLT and the home ONU, and the EW traffic is the traffic forwarded between each home ONU in a home PON. In the i-th home PON, the available bandwidth for the NS traffic is The available bandwidth for EW traffic The formulas are:

in, represents the upstream capacity of the ith home PON, γ _i represents the proportion of NS traffic in the total traffic, 1-γ _i represents the proportion of EW traffic in the total traffic, and T1 represents the maximum length of an upstream frame.

In one embodiment of the present invention, the process of calculating the available upstream bandwidth of each home PON in step S1 is optimized, and the method includes:

Available bandwidth for NS traffic based on the capacity of access network PON and home PON The formula is restricted and expressed as:

Wherein, UC _A represents the uplink capacity of the access network PON, β _i represents the bandwidth weight that determines the available bandwidth of each home PON, and the formula of β _i is:

in, It is a collection of home PON indexes in a centralized cascade PON;

Since EW traffic does not need to be uploaded to the access network PON, the available bandwidth of NS traffic is calculated. After that, the available bandwidth for EW traffic is the remaining bandwidth in the home PON, and the formula is:

In one embodiment of the present invention, the T-CONT in step S2 includes NS T-CONT and EW T-CONT, and each of the NS T-CONT and the EW T-CONT includes four types, and the four types correspond to four different priorities.

In one embodiment of the present invention, in step S2, the calculated available uplink bandwidth of each home PON is allocated to the T-CONT of each home PON, and the method includes:

For the upstream bandwidth, TCONT bytes TB are used as the service parameters for each type of T-CONT. TB represents the total available bandwidth of a certain type of T-CONT within a fixed time interval SI. For the jth type of NS T-CONT or EW T-CONT, the formula for TCONT bytes TB ^i,j in the i-th home PON is:

TB ^i,j =(FB ⁱ −O _i )·ω _j

Where O _i represents the frame overhead of the NS burst or EW burst sent by the i-th home PON, ω _j represents the bandwidth weight of the j-th type of NS T-CONT or EW T-CONT, which depends on the priority of the NS T-CONT or EW T-CONT;

Based on TB ^i,j , different bandwidths are allocated to NS T-CONTs or EW T-CONTs of different priorities in each home PON.

In one embodiment of the present invention, based on TB ^i,j , different bandwidths are allocated to NS T-CONTs or EW T-CONTs of different priorities in each home PON. Specifically, bandwidth is allocated multiple times to each T-CONT in a polling cycle. The method includes:

For the upstream bandwidth, the access network OLT allocates available upstream bandwidth TB ^i,j to the NS T-CONT and EW T-CONT in each home PON in order of priority; the bandwidth of T-CONTs with the same priority will be allocated uniformly, and the available upstream bandwidth TB ^i,j will be evenly allocated to these T-CONTs; if there is a T-CONT whose bandwidth demand is still not met, the remaining bandwidth in the allocated upstream bandwidth TB ^i,j will be evenly allocated again to the T-CONT whose bandwidth demand is not met, and multiple iterations will be performed until the remaining bandwidth is exhausted or the bandwidth demands of all T-CONTs are met.

In one embodiment of the present invention, the method for calculating the available downstream bandwidth of each home PON in step S3 and optimizing the downstream bandwidth calculation process of each home PON includes:

Calculate the available bandwidth of downstream NS frames in each home PON When the access network OLT is set to 1, the access network OLT should reserve an EW transmission window to ensure that the EW burst sent to the home OLT in the previous polling cycle is transmitted in time. The EW burst is the upstream frame containing EW traffic previously uploaded by the home ONU. The downstream NS frame bandwidth formula of the i-th home PON is:

in, represents the downstream capacity of the ith home PON, DC _A represents the downstream capacity of the access network PON, T2 represents the maximum length of the downstream frame, is the set of EW bursts stored in the home OLT buffer, represents the size of the jth EW burst in the i-th home PON, _δi is the bandwidth weight calculated based on the downstream capacity of the i-th home PON, and the formula is:

The access network OLT calculates the available downstream bandwidth DF _A for NS traffic of the access network PON, and the formula is:

The access network OLT calculates the available downstream bandwidth for EW traffic of each home PON. The formula is:

in, represents the downstream capacity of the ith home PON.

In order to solve the above technical problems, the present invention provides a bandwidth allocation system for a cascaded passive optical network, comprising:

Uplink calculation and optimization module: used to calculate the available uplink bandwidth of each home PON in a centralized cascade PON, and optimize the uplink bandwidth calculation process of each home PON, wherein the centralized cascade PON includes an access network PON and several home PONs, the access network PON includes an access network OLT and several access network ONUs, each of the home PONs includes several home OLTs with the same number as the access network ONUs, each of the home OLTs includes several home ONUs, the access network OLT is connected to several access network ONUs, each of the access network ONUs is connected to the corresponding home OLT, and each home OLT is connected to several home ONUs;

Uplink allocation module: used to allocate the calculated available uplink bandwidth of each home PON to the T-CONT of each home PON, so as to complete the allocation of uplink bandwidth, wherein the T-CONT is a transmission container set in each home ONU for carrying traffic;

Downstream calculation and allocation module: used to calculate the available downstream bandwidth of each home PON in a centralized cascade PON, optimize the downstream bandwidth calculation process of each home PON, and complete the allocation of downstream bandwidth.

To solve the above technical problems, the present invention provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the bandwidth allocation method for a cascaded passive optical network are implemented.

To solve the above technical problem, the present invention provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the bandwidth allocation method for a cascaded passive optical network are implemented.

The above technical solution of the present invention has the following advantages compared with the prior art:

The joint DBA algorithm based on the centralized cascade PON proposed in the present invention enables the access network OLT to uniformly allocate upstream bandwidth and downstream bandwidth for the access network PON and the home PON at the same time; the joint DBA algorithm of the present invention also supports bandwidth allocation for both EW and NS traffic;

The present invention can significantly improve bandwidth utilization in FTTR scenarios and effectively reduce packet loss and delay.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

Fig. 1 is a flow chart of the method of the present invention;

FIG. 2( a ) is a schematic diagram of uplink bandwidth allocation using a joint DBA algorithm according to an embodiment of the present invention;

FIG2( b ) is a schematic diagram of downlink bandwidth allocation using a joint DBA algorithm according to an embodiment of the present invention;

FIG3 is a schematic diagram of a centralized cascade PON structure according to an embodiment of the present invention;

FIG4 is a comparison diagram of packet loss rates between a traditional DBA algorithm and a joint DBA algorithm according to an embodiment of the present invention;

5 is a schematic diagram of bandwidth utilization in an access network according to an embodiment of the present invention;

6(a) and 6(b) are schematic diagrams of average upstream delay of NS traffic in a home PON and an access network PON under different conditions in an embodiment of the present invention;

6(c) and 6(d) are schematic diagrams of average downstream delay of EW traffic in access network PON and home PON under different conditions in an embodiment of the present invention;

FIG6(e) and FIG6(f) are schematic diagrams of average delays of uplink and downlink EW traffic under different conditions in an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

Embodiment 1

1, the present invention relates to a bandwidth allocation method for a cascaded passive optical network, comprising:

Step S1: in a centralized cascade PON, the available upstream bandwidth of each home PON is calculated, and the upstream bandwidth calculation process of each home PON is optimized, wherein the centralized cascade PON includes an access network PON and several home PONs, the access network PON includes an access network OLT and several access network ONUs, each of the home PONs includes several home OLTs with the same number as the access network ONUs, each of the home OLTs includes several home ONUs, the access network OLT is connected to several access network ONUs, each of the access network ONUs is connected to a corresponding home OLT, and each home OLT is connected to several home ONUs, see FIG3 for details;

Step S2: Allocate the calculated available upstream bandwidth of each home PON to the T-CONT of each home PON to complete the allocation of upstream bandwidth, wherein the T-CONT is a transmission container set in each home ONU for carrying traffic;

Step S3: in the centralized cascade PON, the available downstream bandwidth of each home PON is calculated, the downstream bandwidth calculation process of each home PON is optimized, and the downstream bandwidth allocation is completed;

Among them, the upstream bandwidth includes the time slot resources occupied by the EW traffic in the home ONU flowing to the home OLT (the EW traffic between different home ONUs is forwarded through the home OLT to which they belong), and the time slot resources occupied by the NS traffic in the home ONU flowing to the access network OLT; the downstream bandwidth is the time slot resources occupied by the NS traffic in the access network OLT and the EW traffic of the home OLT flowing to the home PON.

The following is a detailed introduction to this embodiment:

1. Uplink Bandwidth Calculation Method

The joint DBA algorithm scheme designed in this embodiment is as follows: when calculating the upstream bandwidth of the centralized cascade PON, firstly, the total bandwidth in an upstream frame is divided into NS traffic bandwidth according to the ratio of NS and EW traffic. and EW traffic bandwidth Two parts. represents the upstream capacity of the ith home PON, and γ _i represents the proportion of NS traffic in the total traffic. Then in the ith home PON, the upstream available bandwidth of NS T-CONT is It can be calculated as follows:

Similarly, the available bandwidth for EW traffic We can replace γ _i in formula (2) with (1-γ _i ) to obtain

T1 represents the maximum length of an uplink frame, which is 125 microseconds.

However, the sum of the upstream capacities of each home PON may not match the upstream capacity of the access network PON. This mismatch may cause the total NS traffic uploaded from the home PON to exceed the capacity of the access network PON, causing the NS upstream burst frames to queue in the buffer of the access network ONU, thereby causing congestion or packet loss. In order to avoid potential congestion at the access network PON, this embodiment requires a capacity comparison based on the access network PON and the home PON. Considering that the upstream capacity of each home PON may be different, the upstream capacity of each home PON in the centralized cascade PON system It can be further written as follows:

Wherein, UC _A represents the uplink capacity of the access network PON, and β _i represents the bandwidth weight that determines the available bandwidth of each home PON. _{β i} can be calculated as follows:

in, It is a collection of home PON indexes in a centralized cascade PON. Since EW traffic does not need to be uploaded to the access network, after calculating the bandwidth of NS traffic, the available bandwidth for EW traffic uplink is This is the remaining bandwidth in the home PON, which can be obtained by the following formula:

2. Downlink Bandwidth Calculation Method

In downstream transmission, EW traffic shares the same channel with the downstream NS traffic in each home PON. However, since the bandwidth of EW traffic is determined by the NS downstream frames in the home PON, especially when the downstream load is high, EWburst means that the upstream frames containing EW traffic previously uploaded by the home ONU may not be transmitted in time within the EW transmission window (i.e., the gaps between downstream NS frames in the home PON). To ensure the transmission efficiency of EW burst, it is necessary to limit the bandwidth allocated to the downstream NS frames in each home PON. Therefore, when calculating the downstream NS frames in each home PON, the bandwidth of the downstream NS frames in each home PON must be limited. When the access network OLT is 1, the access network OLT should reserve an EW transmission window (i.e., the gap between downstream NS frames in the home PON) to ensure that the EW burst sent to the home OLT in the previous polling cycle can be transmitted in time. In this case, it is calculated as follows:

in, represents the downstream capacity of the ith home PON, DC _A represents the downstream capacity of the access network PON, and T2 represents the maximum length of a downstream frame. is the set of EW bursts stored in the home OLT buffer, represents the size of the jth EW burst in the i-th home PON. _δi is the bandwidth weight calculated based on the downstream capacity of the i-th home PON, which can be obtained as follows:

Then, the access network OLT calculates the available downstream bandwidth (DF _A ) of the NS traffic of the access network PON by the following formula:

Downstream available bandwidth for EW traffic in each home PON Calculated by:

in, represents the downstream capacity of the ith home PON.

It should be noted that when calculating the downstream bandwidth, the access network OLT gives priority to the bandwidth of the NS downstream traffic. The above formulas 6-7 are used to calculate the available bandwidth of the NS traffic of each home PON, and formula 8 is used to calculate the available bandwidth of the NS traffic of the access network PON (that is, the sum of the available bandwidth of the NS traffic of each home PON). After calculating the bandwidth of the NS traffic, the remaining downstream bandwidth in each home PON is the available downstream bandwidth of the EW traffic in the home PON (that is, the downstream capacity of each home PON is used). Subtract each household PON get).

It should be noted that during the data uplink process, NS traffic starts from the home ONU and is uploaded to the access network OLT, and EW traffic starts from the home ONU and is only uploaded to the home OLT in the current home PON. During the data downlink process, NS traffic (needs to be recalculated) is transmitted from the access network OLT to the home ONU, and when it reaches the home OLT during the transmission process, it is combined with the EW traffic that reaches the home OLT during the uplink process and transmitted to the home ONU.

3. Bandwidth Allocation Method

The available upstream bandwidth needs to be stored in the T-CONT of each home ONU before bandwidth allocation, while the downstream bandwidth is directly allocated because it is broadcast.

After calculating the available upstream bandwidth of each home PON, they are allocated to the T-CONTs of their respective home ONUs. In order to improve bandwidth utilization, an effective method is to reallocate bandwidth according to the needs of the T-CONTs in each home PON. To achieve this goal, the joint DBA algorithm proposed in this embodiment introduces a maximum-minimum fair allocation strategy to allocate bandwidth to each T-CONT multiple times within a polling cycle.

Compared with the traditional DBA algorithm, the joint DBA algorithm of this embodiment uses TCONT bytes (TB) as the service parameter of each type of T-CONT instead of using AB. TB represents the total available bandwidth of a certain T-CONT type within SI. For the jth type of NS or EW T-CONT, the TCONT bytes (TB ^i,j ) in the i-th home PON can be calculated as follows:

TB ^i,j = (FB ⁱ -O _i )·ω _j #(10)

Where O _i represents the frame overhead of the NS or EW burst sent by the i-th home PON, including the frame header, frame tail, DBRu (report information) and guard time. ω _j represents the bandwidth weight of the j-th type of NS or EW T-CONT, which depends on the priority of the NS or EW T-CONT. In this way, different bandwidths can be allocated to NS T-CONTs or EW T-CONTs of different priorities in each home PON.

FIG2 shows the flow chart of the joint DBA algorithm, which includes two parts: the uplink bandwidth (FIG2(a)) and the downlink bandwidth (FIG2(b)) allocation process.

For Figure 2(a), the upstream process starts with allocating available upstream bandwidth for NS and EW traffic to each home PON. Start (Formula 3-5). Next, the access network OLT calculates the bandwidth (TB ^i,j ) allocated to each T-CONT priority (Formula 10). Then, after identifying the traffic type, the access network OLT allocates upstream bandwidth to the NS and EW T-CONTs in each home PON in order of priority. The bandwidth of T-CONTs with the same priority will be allocated uniformly, and the available bandwidth BL will be evenly distributed to these T-CONTs. If the needs of some T-CONTs are still not met, the remaining bandwidth will be evenly allocated again, and the process will go through multiple iterations until the remaining bandwidth is exhausted or the bandwidth needs of all T-CONTs are met. In this way, the problem of bandwidth utilization caused by bandwidth inequality will disappear. After the process is completed, the access network OLT will check the remaining bandwidth BL of TB ^i,j and add it to the available bandwidth of the next priority T-CONT. It should be noted that the remaining bandwidth of a NS T-CONT of a certain priority can only be inherited by a NS T-CONT with a lower priority, but not by an EWT-CONT. The same is true for EW T-CONT. After that, the access network OLT allocates bandwidth to the NS and EW T-CONTs in each home PON (i.e. and ) generates their own BWmap fields (Home BWmap) to authorize bandwidth for EW and NS traffic of each home PON, and then allocates NS upstream bandwidth to the access network PON To generate the BWmap field (Access BWmap) of the access network PON, which is used for the NS traffic authorized bandwidth of the access network PON.

For Figure 2(b), the downstream bandwidth allocation process also includes bandwidth calculations for EW and NS traffic. First, use Formula 6-7 to calculate the available downstream bandwidth for NS traffic in the current home PON: At the same time, the length of the EW transmission window Set to the remaining bandwidth in the downstream frame of the current home PON. Then, determine the size of the first EW burst in the home OLT buffer Whether the transmission window size is exceeded If not, allocate it to the EW downlink bandwidth And update the remaining transmission window size Then, the above operation is performed for the next EW burst until the size of the EW burst exceeds the length of the EW transmission window. That is, the EW downstream bandwidth of the current home PON. After the downstream bandwidth allocation of each home PON is completed, the bandwidth allocated to the NS traffic in the access network PON (DF _A ) is obtained by formula (8), thereby completing the downstream bandwidth allocation of the access network PON. In addition, the output Will be distributed with the upstream output as well as Used together to generate Access BWmap fields.

Experimental analysis

In order to verify the performance of the method of this embodiment, this embodiment uses matlab software for simulation testing. In the simulation, this embodiment simulates 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), wherein the physical distance between the access network OLT and the access network ONU is set to 20 kilometers, and the distance between the home ONU and the home OLT in each home PON is 200 meters. In addition, the generated NS and EW flows are Poisson flows. The SDU frame size is between 64 bytes and 1518 bytes. This embodiment assumes that the home ONUs in all home PONs have the same arrival rate, and the ratio of NS traffic to EW traffic arriving in any home ONU is 1:1. In addition, the load of the downstream traffic is consistent with the upstream load in the simulation. In addition, this embodiment considers 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.

In the simulation, the traditional ITU-T PON DBA algorithm is used as a benchmark for comparison with the joint DBA algorithm. The DBA algorithm adopts a single allocation strategy, which allocates bandwidth to each T-CONT once in each polling cycle according to pre-set parameters. Both algorithms are adapted to the scheduling mechanism of centralized cascade PON and can allocate bandwidth for EW and NS traffic. The key difference between them is the strategy adopted by the joint DBA to improve bandwidth utilization.

Since the total upstream capacity of the home PON exceeds the upstream capacity of the access network PON, this may cause congestion of NS traffic in the access network PON. Therefore, first, this embodiment evaluates the packet loss rate (PLR) of NS traffic, that is, the ratio of the number of lost packets to the total number of generated packets. Figure 4 shows the PLR of NS traffic in the home PON and the access network PON. Since the bandwidth of the home PON is limited, traffic congestion in the access network PON is avoided. Therefore, as the load increases, both the joint DBA and traditional DBA schemes will experience packet loss. Compared with the traditional DBA scheme, the joint DBA shows a lower PLR in the home PON, which is due to the improvement of bandwidth utilization by the joint DBA algorithm, as shown in Figure 5. For NS traffic in the access network PON, due to the limitation of the bandwidth allocated by the home PON, there is no packet loss in both schemes. In addition, it should be noted that there is no packet loss of EW traffic in both the joint DBA and traditional DBA schemes, because EW traffic in the home PON has sufficient bandwidth, thereby ensuring that the EW burst can be transmitted to the home OLT in time.

On the other hand, the higher bandwidth utilization in joint DBA also leads to better latency performance compared to the traditional DBA scheme. The upstream end-to-end latency of NS traffic consists of two parts: the latency in the home PON and the access network PON. In the home PON, as shown in Figure 6(a), as the NS traffic load increases, the average latency of T2 in both schemes can be kept below 1 ms, but joint DBA shows better performance. When the NS load in each home PON reaches 310 Mbps (i.e., when the access network PON is fully loaded), the latency of joint DBA is reduced by about 300 microseconds compared to the traditional DBA scheme. In addition, the performance improvements of T3 and T4 are particularly significant. For T3, when the load exceeds 275 Mbps, the latency in the traditional DBA scheme exceeds 1 ms, while the latency in joint DBA is almost stable at about 0.44 ms. For T4, the latency in the traditional DBA scheme exceeds 1 ms regardless of the provided load, and reaches 100 ms after the load exceeds 125 Mbps. In contrast, joint DBA can keep the latency below 1 ms until the load exceeds 275 Mbps. These improvements are due to the fact that in the joint DBA algorithm, the bandwidth allocated to different NS T-CONTs is fully utilized according to the maximum-minimum fair allocation strategy. In addition, it can be seen that when the load is low (i.e., when the NS load is less than 250Mbps), there is almost no difference in the delay of the three types of T-CONTs. This is because all three types of T-CONTs can be allocated sufficient bandwidth. Therefore, compared with the traditional DBA scheme, the proposed joint DBA algorithm greatly improves the delay performance of NS traffic in home PON.

In the access network PON, the upstream delays of the three types of NS T-CONTs in both schemes are almost the same, ranging from 150 microseconds to 200 microseconds. This is because the bandwidth allocated to NS traffic by the home PON is limited. In this case, the overall throughput of the home PON does not exceed the capacity of the access network PON, so the bandwidth requirements of all NS T-CONTs in both schemes can be met, resulting in the delay performance shown in the figure.

In the downstream direction, NS traffic is broadcast to all home ONUs, and the type of NS traffic is not distinguished during the scheduling process. Therefore, this embodiment only shows the average delay of NS downstream traffic in the access network PON and the home PON, as shown in Figures 6(c) and (d). In the access network PON, when the load is less than 9 Gbps, the delays of the two schemes are close, and both rise slowly as the load increases. Thereafter, the delay of the two schemes rises sharply to about 59 milliseconds. However, the NS traffic delay in the home PON remains below 100 microseconds when the load is high, as shown in Figure 6(d). This is because the downstream bandwidth of NS traffic in each home PON is more sufficient than that of the access network PON.

Regarding EW traffic, Figures 6(e) and (f) show the average delay versus load in the upstream and downstream directions. As shown in Figure 6(e), regardless of the load, the upstream delay of T2 and T3 in both schemes remains within 400 microseconds. For T4, both schemes can ensure that the delay is within 1 millisecond, but the joint DBA still reduces the delay by about 96 microseconds compared to the traditional DBA scheme. In addition, in downstream transmission, the performance of the two schemes is also similar, and the average delay of all EW T-CONTs remains within 250 microseconds. This is because the NS downstream frames in the home PON do not occupy the bandwidth allocated for the EW burst, ensuring that all EWbursts can be sent to the corresponding home ONUs within two polling cycles after being uploaded to the home OLT.

In summary, simulation results show that UDBA achieves higher bandwidth utilization compared to the conventional DBA algorithm, thereby reducing upstream packet delay and packet loss rate without adversely affecting the downstream performance of NS and EW traffic.

Embodiment 2

This embodiment provides a bandwidth allocation system for a cascaded passive optical network, including:

Uplink calculation and optimization module: used to calculate the available uplink bandwidth of each home PON in a centralized cascade PON, and optimize the uplink bandwidth calculation process of each home PON, wherein the centralized cascade PON includes an access network PON and several home PONs, the access network PON includes an access network OLT and several access network ONUs, each of the home PONs includes several home OLTs with the same number as the access network ONUs, each of the home OLTs includes several home ONUs, the access network OLT is connected to several access network ONUs, each of the access network ONUs is connected to the corresponding home OLT, and each home OLT is connected to several home ONUs;

Uplink allocation module: used to allocate the calculated available uplink bandwidth of each home PON to the T-CONT of each home PON, so as to complete the allocation of uplink bandwidth, wherein the T-CONT is a transmission container set in each home ONU for carrying traffic;

Downstream calculation and allocation module: used to calculate the available downstream bandwidth of each home PON in a centralized cascade PON, optimize the downstream bandwidth calculation process of each home PON, and complete the allocation of downstream bandwidth.

Embodiment 3

This embodiment provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the bandwidth allocation method for a cascaded passive optical network described in Embodiment 1 are implemented.

Embodiment 4

This embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the bandwidth allocation method for a cascaded passive optical network described in the first embodiment are implemented.

Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiment, complete software embodiment, or the embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiment of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal translation scripting language JavaScript, etc.

The present application is described with reference to the flowchart and/or block diagram of the method, device (system) and computer program product according to the embodiment of the present application. It should be understood that each process and/or box in the flowchart and/or block diagram, and the combination of the process and/or box in the flowchart and/or block diagram can be realized 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 produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for realizing the function specified in one process or multiple processes in the flowchart and/or one box or multiple boxes in the block diagram.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

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 (4)

1. A bandwidth allocation method for a cascade passive optical network is characterized in that: comprising the following steps:

Step S1: in a centralized cascading PON, calculating an available uplink bandwidth of each home PON, and optimizing an uplink bandwidth calculation process of each home PON, wherein the centralized cascading PON comprises an access network PON and a plurality of home PONs, the access network PON comprises an access network OLT and a plurality of access network ONUs, each home PON comprises a plurality of home OLTs which are the same as the access network ONUs in number, each home OLT comprises a plurality of home ONUs, the access network OLT is connected with the plurality of access network ONUs, each access network ONU is connected with the corresponding home OLT, and each home OLT is connected with the plurality of home ONUs;

Step S2: distributing the calculated uplink bandwidth available to each home PON to a T-CONT of each home PON, and completing the distribution of the uplink bandwidth, wherein the T-CONT is a transmission container which is arranged in each home ONU and used for carrying traffic;

Step S3: in the centralized cascading PON, calculating the available downlink bandwidth of each home PON, optimizing the downlink bandwidth calculation process of each home PON, and completing the allocation of the downlink bandwidth;

in the step S1, the method calculates the uplink bandwidth available to each home PON, including:

Firstly, dividing the total bandwidth in an uplink frame into NS traffic available bandwidths according to the ratio of NS traffic to EW traffic And EW traffic available bandwidthThe NS traffic is the traffic between the access network OLT and the home ONU, and the EW traffic is the traffic forwarded between each home ONU in one home PON, and in the ith home PON, the NS traffic has available bandwidthThe EW traffic available bandwidthThe formulas of (a) are respectively as follows:

Wherein, The uplink capacity of the ith home PON is represented, γ _i represents the proportion of NS traffic in the total traffic, 1- γ _i represents the proportion of EW traffic in the total traffic, and T1 represents the maximum length of one uplink frame;

In the step S1, the uplink bandwidth calculation process available to each home PON is optimized, and the method includes:

Capacity to NS traffic available bandwidth based on access network PON and home PON Is limited by the formula of (c), expressed as:

Where UC _A represents the upstream capacity of the access network PON, β _i represents the bandwidth weight determining the available bandwidth of each home PON and β _i is expressed as:

Wherein, Is a collection of home PON indexes in a centralized tandem PON;

since the EW traffic does not need to be uploaded to the access network PON, the bandwidth available for the NS traffic is calculated After that, the EW traffic can use the bandwidthFor the remaining bandwidth in the home PON, the formula is:

The T-CONT in the step S2 comprises an NS T-CONT and an EW T-CONT, and the NS T-CONT and the EW T-CONT respectively comprise four types, and the four types correspond to four different priorities;

in the step S2, the calculated uplink bandwidth available to each home PON is allocated to the T-CONT of the respective home PON, and the method includes:

For upstream bandwidth, using TCONT byte TB as a service parameter of each type of T-CONT, TB represents the total available bandwidth of a certain T-CONT type within a fixed time interval SI, and for the jth type of NS T-CONT or EW T-CONT, the formula of TCONT byte TB ^i,j in the ith home PON is:

TB^i,j＝(FBⁱ-O_i)·ω_j

wherein O _i represents a frame overhead of NS burst or EW burst transmitted by the ith home PON, omega _j represents a bandwidth weight of the jth type NS T-CONT or EW T-CONT, depending on the priority of the NS T-CONT or EW T-CONT;

Based on TB ^i,j, different bandwidths are allocated to NS T-CONT or EW T-CONT of each priority in each home PON respectively;

Based on TB ^i,j, different bandwidths are allocated to NS T-CONT or EW T-CONT of each priority in each home PON respectively, specifically: the method for allocating bandwidth for each T-CONT multiple times in one polling period comprises the following steps:

For uplink bandwidth, the access network OLT respectively distributes available uplink bandwidth TB ^i,j for NS T-CONT and EW T-CONT in each home PON according to the priority order; the bandwidths of the T-CONTs belonging to the same priority are uniformly allocated, and the available uplink bandwidth TB ^i,j is uniformly allocated to the T-CONTs; if the bandwidth requirement of the T-CONT is still not satisfied, the residual bandwidth in the allocated uplink bandwidth TB ^i,j is equally allocated to the T-CONT with the unsatisfied bandwidth requirement again, and the iteration is carried out for a plurality of times until the residual bandwidth is used up or the bandwidth requirements of all the T-CONT are satisfied;

In the step S3, the available downlink bandwidth of each home PON is calculated, and the downlink bandwidth calculation process of each home PON is optimized, where the method includes:

Calculating the available bandwidth of downlink NS frames in each home PON When the access network OLT should reserve an EW transmission window to ensure that the EW burst sent to the home OLT in the previous polling period is timely transmitted, where the EW burst is an uplink frame including the EW traffic uploaded by the home ONU, and the bandwidth formula of the downlink frame of the ith home PON is:

Wherein, Indicating the downstream capacity of the i-th home PON, DC _A indicating the downstream capacity of the access network PON, T2 indicating the maximum length of one downstream frame,Is a collection of EW bursts stored in the home OLT buffers,The size of the jth EW burst in the ith home PON is represented, δ _i is a bandwidth weight calculated according to the downlink capacity of the ith home PON, where the formula is:

the access network OLT calculates a downlink available bandwidth DF _A of the access network PON about NS traffic, and the formula is:

the access network OLT calculates the downlink available bandwidth of each home PON about EW flow The formula is:

Wherein, The downstream capacity of the i-th home PON is shown.

2. A bandwidth distribution system for cascade passive optical network is characterized in that: comprising the following steps:

And an uplink calculation and optimization module: the method comprises the steps that in a centralized cascading PON, the available uplink bandwidth of each home PON is calculated, and the uplink bandwidth calculation process of each home PON is optimized, wherein the centralized cascading PON comprises an access network PON and a plurality of home PONs, the access network PON comprises an access network OLT and a plurality of access network ONUs, each home PON comprises a plurality of home OLTs which are the same as the access network ONUs in number, each home OLT comprises a plurality of home ONUs, the access network OLT is connected with the plurality of access network ONUs, each access network ONU is connected with the corresponding home OLT, and each home OLT is connected with the plurality of home ONUs;

And an uplink allocation module: the method comprises the steps of distributing calculated uplink bandwidth available to each home PON to T-CONT of each home PON, and completing distribution of the uplink bandwidth, wherein the T-CONT is a transmission container which is arranged in each home ONU and used for carrying traffic;

And the downlink calculation and distribution module is used for: the method is used for calculating the available downlink bandwidth of each home PON in the centralized cascade PON, optimizing the downlink bandwidth calculation process of each home PON and completing the allocation of the downlink bandwidth;

The uplink bandwidth available for each home PON is calculated in the uplink calculation and optimization module, including:

Firstly, dividing the total bandwidth in an uplink frame into NS traffic available bandwidths according to the ratio of NS traffic to EW traffic And EW traffic available bandwidthThe NS traffic is the traffic between the access network OLT and the home ONU, and the EW traffic is the traffic forwarded between each home ONU in one home PON, and in the ith home PON, the NS traffic has available bandwidthThe EW traffic available bandwidthThe formulas of (a) are respectively as follows:

Wherein, The uplink capacity of the ith home PON is represented, γ _i represents the proportion of NS traffic in the total traffic, 1- γ _i represents the proportion of EW traffic in the total traffic, and T1 represents the maximum length of one uplink frame;

the uplink bandwidth calculation process available to each home PON is optimized in the uplink calculation and optimization module, including:

Capacity to NS traffic available bandwidth based on access network PON and home PON Is limited by the formula of (c), expressed as:

Where UC _A represents the upstream capacity of the access network PON, β _i represents the bandwidth weight determining the available bandwidth of each home PON and β _i is expressed as:

Wherein, Is a collection of home PON indexes in a centralized tandem PON;

since the EW traffic does not need to be uploaded to the access network PON, the bandwidth available for the NS traffic is calculated After that, the EW traffic can use the bandwidthFor the remaining bandwidth in the home PON, the formula is:

The T-CONT in the uplink distribution module comprises an NS T-CONT and an EW T-CONT, and the NS T-CONT and the EW T-CONT respectively comprise four types, and the four types correspond to four different priorities;

the uplink allocation module allocates the calculated uplink bandwidth available for each home PON to the T-CONT of the respective home PON, including:

For upstream bandwidth, using TCONT byte TB as a service parameter for each type of T-CONT, TB represents the total available bandwidth for a certain T-CONT type within a fixed time interval SI, and for the jth type of NS T-CONT or EW T-CONT, the formula of TCONT byte TBi ^,j in the ith home PON is:

TB^i,j＝(FBⁱ-O_i)·ω_j

wherein O _i represents a frame overhead of NS burst or EW burst transmitted by the ith home PON, omega _j represents a bandwidth weight of the jth type NS T-CONT or EW T-CONT, depending on the priority of the NS T-CONT or EW T-CONT;

Based on TB ^i,j, different bandwidths are allocated to NS T-CONT or EW T-CONT of each priority in each home PON respectively;

Based on TB ^i,j, different bandwidths are allocated to NS T-CONT or EW T-CONT of each priority in each home PON respectively, specifically: the method for allocating bandwidth for each T-CONT multiple times in one polling period comprises the following steps:

For uplink bandwidth, the access network OLT respectively distributes available uplink bandwidth TB ^i,j for NS T-CONT and EW T-CONT in each home PON according to the priority order; the bandwidths of the T-CONTs belonging to the same priority are uniformly allocated, and the available uplink bandwidth TB ^i,j is uniformly allocated to the T-CONTs; if the bandwidth requirement of the T-CONT is still not satisfied, the residual bandwidth in the allocated uplink bandwidth TB ^i,j is equally allocated to the T-CONT with the unsatisfied bandwidth requirement again, and the iteration is carried out for a plurality of times until the residual bandwidth is used up or the bandwidth requirements of all the T-CONT are satisfied;

the downlink bandwidth available to each home PON is calculated in the downlink calculation and allocation module, and the downlink bandwidth calculation process of each home PON is optimized, including:

Calculating the available bandwidth of downlink NS frames in each home PON When the access network OLT should reserve an EW transmission window to ensure that the EW burst sent to the home OLT in the previous polling period is timely transmitted, where the EW burst is an uplink frame including the EW traffic uploaded by the home ONU, and the bandwidth formula of the downlink frame of the ith home PON is:

Wherein, Indicating the downstream capacity of the i-th home PON, DC _A indicating the downstream capacity of the access network PON, T2 indicating the maximum length of one downstream frame,Is a collection of EW bursts stored in the home OLT buffers,The size of the jth EW burst in the ith home PON is represented, δ _i is a bandwidth weight calculated according to the downlink capacity of the ith home PON, where the formula is:

the access network OLT calculates a downlink available bandwidth DF _A of the access network PON about NS traffic, and the formula is:

the access network OLT calculates the downlink available bandwidth of each home PON about EW flow The formula is:

Wherein, The downstream capacity of the i-th home PON is shown.

3. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized by: the processor, when executing the computer program, implements the steps of the bandwidth allocation method for a tandem-type passive optical network according to claim 1.

4. A computer-readable storage medium having stored thereon a computer program, characterized by: the computer program, when executed by a processor, implements the steps of the bandwidth allocation method for a tandem-type passive optical network according to claim 1.