Data scheduling method used in EPON terminal system and based on absolute priority

Abstract

The invention relates to a data scheduling method used in an EPON terminal system and based on absolute priority. The EPON terminal system is a point-to-multipoint network system, comprises three parts: an end OLT, a terminal ONU and a passive optical divider, and is characterized in that: a. FIFOs used for data caching are added in the terminal ONU, and the number of the FIFOs is determined by the current priority number for data discrimination; b. address spaces are allocated in an external memory according to the priority; c. the terminal ONU transmits data to the end OLT, a transmission time slot for report frames used for bandwidth application is reserved at the tail part of a transmission time slot, and the number of data remained in the current system and to be transmitted can be accurately calculated when every time slot transmission is ended; d. when a higher priority comes, the current transmitted data is confirmed to be consistent with the data applied to be transmitted; and e. when end OLT allocates bandwidth more than the applied bandwidth to the terminal ONU, absolute priority scheduling can be selected or round-robin scheduling is selected to equally allocate the excessive bandwidth. Through practical operation and testing, the invention has the advantages that the effect is good, the bandwidth utilization ratio is high and the data transmission requirement of the EPON system is satisfied.

Description

technical field [0001] The invention relates to a data scheduling method applied to an EPON terminal system (ONU), in particular to the absolute priority used when utilizing external memory, including SDRAM, DDR-SDRAM and DDRII-SDRAM, for data buffering and distinguishing different data service levels level scheduling method. Background technique [0002] The EPON system is a point-to-multipoint network system, which mainly includes three parts: central office OLT, terminal (user end) ONU and passive optical splitter, as attached figure 1 shown. In the downstream direction, the Ethernet data packets sent by the OLT are transmitted to each ONU through a 1xN passive optical splitter in a broadcast manner, and the ONUs selectively extract the data packets; Due to the directional characteristics of the splitter, the data packets sent by any ONU can only reach the OLT, but not the ONU, that is, the data of all ONUs are transmitted to the same OLT, thus constructing the point-to...

AI Technical Summary

Problems solved by technology

[0005] First of all, after the ONU obtains the sending time slot to read data from the external memory, there will be a certain time delay due to the read operation of the memory, that is, a certain time delay will be generated when sending data to the OLT, resulting in a waste of bandwidth; at the same time The external memory itself needs a refresh operation to keep the data, and the refresh operation takes a certain amount of time to complete, and the external memory cannot be accessed during this period, which further increases the waste of data bandwidth;

[0006] Secondly, due to the uncertainty of the data arrival time, when the ONU obtains a time slot to send data to the OLT, it is possible that data with a higher priority will arrive at the ONU at this time. In the general absolute priority scheduling algorithm, the ONU will schedule The data with the highest priority, at this time, there will be inconsistencies between the data sent by the ONU to the OLT and the data actually sent. Although this inconsistency will not cause system confusion and errors, it will cause some difficulties in the allocation of time slots for the OLT. The data statistics for the OLT will also bring confusion, and what is more serious is the waste of bandwidth;

[0007] Finally, when the ONU applies for data bandwidth from the OLT, the OLT may allocate more than the requested data bandwidth to the ONU, resulting in the problem of remaining bandwidth

In the general absolute priority scheduling algorithm, the ONU will schedule the highest priority data. At this time, the low priority data cannot get bandwidth for a long time, and it is easy to "starve to death".

Images