CN1156098C - Bandwidth compensating method for ranging ATM passive optical network - Google Patents

Abstract

The invention discloses a method for realizing bandwidth compensation during distance measurement of an ATM passive optical network. Some fixed bandwidth calculates the size of the bandwidth loss due to the opening of the ranging window; b. the optical line terminal (OLT) adds the lost bandwidth application to the dynamic bandwidth application queue of the optical network unit (ONU); c. During secondary allocation, the optical line terminal (OLT) re-allocates the idle bandwidth to the optical network unit (ONU) that lost the bandwidth. Applying this method to the APON system can guarantee the service QOS to the greatest extent and protect the interests of users at the same time.

Description

Realization Method of Bandwidth Compensation in ATM Passive Optical Network Ranging

The present invention relates to the bandwidth compensation technology when ATM passive optical network is measured, especially refers to a kind of can be in ATM passive optical network optical line terminal (OLT) and optical network unit (ONU) while measuring distance, compensate due to ranging method of causing bandwidth loss.

Due to the advent of the network era, various communication networks with increasingly powerful functions are developing rapidly to meet the increasing needs of people. ATM Passive Optical Network (APON) is one of them. It can not only flexibly provide broadband multimedia services, but also allow access Multiple users in the incoming network share the entire bandwidth.

In the APON system, due to the different logical distances between the ONUs at the user end and the OLT at the central office, the phases of data arriving at the OLT from different ONUs may be different, resulting in data conflicts between ONUs arriving at the OLT, resulting in data loss. In order to ensure that each ONU maintains the same logical distance, so that each user's data can be connected to the central office according to a certain phase without conflict, the distance measurement method is used to measure and adjust the logical distance between the OLT and the ONU.

During the ranging process, the OLT needs to open a ranging window of a certain size. The ranging window is actually to shield a certain segment of the bandwidth of the line, so that the measured ONU sends the ranging physical layer operation management and maintenance (PLOAM) to the OLT. Cells can appear in this shielded section without being affected by other data. After the TC layer of the OLT captures the required cells, the distance measurement will be completed, and then the distance between the ONU and the OLT will be calculated by delay. and make adjustments. That is to say, a part of the fixed bandwidth will be occupied for a period of time during the ranging process, which will affect those services that are sensitive to delay and jitter. Moreover, if the fixed bandwidth of an ONU is larger, the fixed bandwidth loss caused by ranging will be more, so in the case of frequent ranging, it will have a certain impact on the business and damage the quality of service (QOS) .

In view of this, the main purpose of the present invention is to provide a method for realizing bandwidth compensation during ATM passive optical network ranging, so that the service QOS damage caused by ranging is reduced to the minimum, thereby ensuring the service QOS to the greatest extent, while also protecting User Benefits.

In order to achieve the above object, technical solution of the present invention is achieved in that way:

A method for realizing bandwidth compensation during ATM passive optical network ranging, the key is that the method at least includes the following steps:

a. The optical line terminal (OLT) calculates the size of the bandwidth lost due to the opening of the ranging window according to the fixed bandwidth that should be allocated during the bandwidth allocation of the optical network unit (ONU) in normal operation;

b. the optical line terminal (OLT) adds the lost bandwidth application to the dynamic bandwidth application queue of the optical network unit (ONU);

c. When the bandwidth is re-allocated, the optical line terminal (OLT) re-allocates the idle bandwidth to the optical network unit (ONU) that has lost the bandwidth.

Wherein, the dynamic bandwidth application queue is the highest priority constant bit rate (CBR) service dynamic bandwidth application queue.

The calculation of the loss bandwidth is firstly to count the number of data licenses submerged by opening the ranging window by the optical line terminal (OLT), and then calculate the loss bandwidth according to the fixed bandwidth occupied by each license during bandwidth allocation.

It can be seen from the above scheme that the implementation method of bandwidth compensation during ATM passive optical network distance measurement provided by the present invention adds bandwidth compensation processing in the distance measurement realization process. Since the ranging process will lose a certain fixed bandwidth due to the opening of the ranging window, the present invention inserts the data submerged in the ranging window into the highest priority queue of the dynamic bandwidth application, and re-allocates it when the bandwidth is allocated twice. Bandwidth, so that these data have the opportunity to send, so as to reduce the impact of the ranging process on the business, so as to minimize the damage to the business QOS, so as to achieve the purpose of improving the quality of business services and protecting the interests of users.

The detailed description and technical content of the present invention are as follows in conjunction with the accompanying drawings:

Fig. 1 is the ONU fixed bandwidth distribution schematic diagram when not carrying out bandwidth compensation;

Figure 2 is a schematic diagram of a fixed bandwidth compensation scheme;

FIG. 3 is a schematic diagram of a bandwidth compensation operation in the present invention;

FIG. 4 is a flow chart of the implementation of the bandwidth compensation method of the present invention;

FIG. 5 is a schematic diagram of ONU fixed bandwidth distribution after bandwidth compensation.

In the APON system, due to system expansion, that is, the cold ONU joins the system; and the offline ONU rejoins the system, that is, the hot ONU joins the system. In both cases, the APON system needs to measure the distance of the ONU, so the distance measurement is not possible. Avoided. The ranging of any ONU will affect the fixed bandwidth of other normal ONUs, because as long as the ranging is performed, a corresponding ranging window will appear on the line, and other normal ONUs will lose their fixed bandwidth within the ranging window. As shown in Figure 1, when the ONU is in a normal working state, its fixed bandwidth will not change unless the system modifies it, that is to say, it is a constant. But due to the impact of ranging, the ONU's fixed bandwidth will be lost during the window, and if there is no compensation, the bandwidth gap shown in Figure 1 will appear. This bandwidth gap causes the user's fixed bandwidth to be lost instantaneously. In this way, on the one hand, it will directly affect the instantaneous reduction of the user's fixed bandwidth; Issue any data permission, so that the ONU cannot access data to the OLT within this period of time.

For this reason, the present invention proposes a kind of bandwidth compensation method to solve the above-mentioned problem, and its basic idea is exactly: carry out statistics on the bandwidth loss that causes because of ranging, and put the bandwidth of loss into the highest priority of the dynamic bandwidth application of this ONU In the queue, this part of the lost bandwidth is compensated by means of dynamic bandwidth allocation. As shown in Fig. 2, Fig. 2 is a schematic diagram of a fixed bandwidth compensation method for an ONU in normal operation, which shows the process of counting bandwidth loss and counting the lost bandwidth into a dynamic application queue. If there are multiple normal operating ONUs in the APON system, similarly, the fixed bandwidth loss caused by ranging of all normal operating ONUs can be counted and placed in the corresponding ONU highest-level dynamic application queue.

Taking a specific transmission frame as an example, the implementation process of the fixed bandwidth compensation method can be further described in detail with reference to FIG. 3 . Since the dynamic bandwidth allocation in the APON system is to allocate bandwidth twice, the so-called twice bandwidth allocation means that the OLT first allocates the bandwidth to the ONU according to the reference bandwidth, and if there is a free licensed position at this time, then apply for the free licensed position according to the bandwidth. Queue priorities are assigned to the corresponding ONUs in order from high to low, and the details of the secondary allocation of bandwidth have been applied for separately. Therefore, the present invention can compensate the fixed bandwidth lost in ranging by utilizing the second opportunity of bandwidth allocation. As shown in Figure 3, the time slots with filling lines in the uplink frame 10 are the fixed bandwidth occupied by opening the ranging window, and the OLT calculates the size of this part of the fixed bandwidth lost, and when the bandwidth is re-allocated, the part The bandwidth is added to the CBR service dynamic bandwidth application queue with the highest priority, and the OLT re-allocates the idle bandwidth to this part of the ONU, so that the ONU can transmit its data. Such bandwidth compensation can reduce the damage of service QOS caused by ranging Reduce to the minimum, so as to ensure the service QOS to the greatest extent, and at the same time protect the interests of users.

In summary, the specific implementation of the method of the present invention at least includes the following steps, as shown in Figure 4:

1) First, the OLT calculates the size of the lost bandwidth. The OLT finds out how many downlink data licenses are submerged by the ranging window during the ranging process, and can calculate the fixed bandwidth loss caused by the normal operation of the ONU due to the opening of the ranging window. Because the bandwidth of the ONU is reflected in the form of the ONU data license, the number of data licenses flooded due to the opening of the ranging window is simply counted, and the amount of bandwidth loss can be known immediately. As shown in Figure 2, the shaded part is the ranging window, and the three Data in it are the submerged data permits, and the OLT will add the number of submerged data permits to the priority queue of the highest dynamic bandwidth of the ONU. In this way, the OLT can obtain the accurate data of the bandwidth loss by counting the number of flooded data permits of a normal operating ONU within the ranging window. The method can simply and accurately obtain the bandwidth loss caused by distance measurement of each normally operating ONU, and is convenient for implementation.

2) The OLT adds the lost bandwidth application to the CBR service dynamic bandwidth application queue with the highest priority in the ONU. As shown in Figure 3, if three data permits are submerged by the ranging window, they are inserted into the highest priority queue of the ONU's dynamic bandwidth application—the CBR service dynamic bandwidth application queue. The general APON system supports four priority services: real-time variable bit rate (rt-VBR), non-real-time variable bit rate (nrt-VBR), unspecified bit rate (UBR) and CBR services. It has high performance requirements, so it has the highest priority. Putting the applications for lost bandwidth into this queue can make up for the lost bandwidth as soon as possible.

3) When the bandwidth is re-allocated, the OLT re-allocates the idle bandwidth to the ONU that has lost the bandwidth, so that the ONU can transmit its data, so that the bandwidth can be compensated.

Figure 5 shows the fixed bandwidth distribution of the ONU after bandwidth compensation. It can be seen from Figure 5 that after bandwidth compensation, the fixed bandwidth loss caused by ranging is compensated in the form of dynamic bandwidth. In an average sense, there is no loss in the fixed bandwidth of the ONU, but there is a certain fluctuation, which is caused by ranging and is inevitable.

In general, the fixed bandwidth of the ONU is to meet the needs of services with high real-time requirements such as CBR, and these services also have high requirements for QoS. The degree of bandwidth satisfaction is an important reason that affects service QoS. On the other hand, fixed bandwidth is usually purchased by users at a certain cost. No matter whether users have business needs or not, from the perspective of protecting users' interests, the fixed bandwidth needs of users should be met.

Therefore, the method of the present invention enables the OLT side to compensate the lost fixed bandwidth according to the actual bandwidth occupancy and the dynamic bandwidth allocation algorithm, which not only reduces or eliminates the damage caused by distance measurement to service QoS, but also protects the interests of users.

Claims (3)

1, the realization method of bandwidth compensation when a kind of ATM passive optical network ranging, is characterized in that the method comprises the following steps at least: a. The optical line terminal (OLT) calculates the size of the bandwidth lost due to the opening of the ranging window according to the fixed bandwidth that should be allocated during the bandwidth allocation of the optical network unit (ONU) in normal operation; b. the optical line terminal (OLT) adds the lost bandwidth application to the dynamic bandwidth application queue of the optical network unit (ONU); c. When the bandwidth is re-allocated, the optical line terminal (OLT) re-allocates the idle bandwidth to the optical network unit (ONU) that has lost the bandwidth. 2. The implementation method according to claim 1, characterized in that: said dynamic bandwidth application queue is a constant bit rate (CBR) service dynamic bandwidth application queue with the highest priority. 3. The implementation method according to claim 1, characterized in that the calculation of the loss bandwidth further comprises the following steps: a1. Firstly, the optical line terminal (OLT) counts the number of data licenses submerged due to the opening of the ranging window; a2. Then calculate the bandwidth loss based on the fixed bandwidth occupied by each license during bandwidth allocation.

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