An upstream GPON frame has a fixed length of 125 μs. Each upstream frame contains the content carried by one or more T-CONTs. All Huawei ONUs connected to a GPON port share the upstream bandwidth
- All ONUs connected to a GPON port send their data upstream at their own timeslots according to bandwidth map (BWmap) requirements.
- Each ONU reports the status of data to be sent to Huawei OLT using upstream frames. Then, the OLT uses DBA to allocate upstream timeslots to ONUs and sends updates in each frame.
A downstream GPON frame has a fixed length of 125 μs and comprises physical control block downstream (PCBd) and payload. PCBd mainly consists of the GTC header and BWmap. The OLT broadcasts PCBd to all ONUs. Then, the ONUs receive the PCBd and perform operations based on the information contained in PCBd.
- The GTC header is used for frame delimitation, synchronization, and forward error correction (FEC).
- The BWMap field notifies every ONU of upstream bandwidth allocation. It specifies the start and end upstream timeslots for the T-CONTs of each ONU, ensuring that all ONUs send data using the timeslots specified by the OLT like Huawei MA5600T to prevent data conflict.
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