3com S7906E Manuel De Montage

 

1-5 

Once the extended OAM connection is established, downlink data transmission can begin. Uplink data 
transmission can begin only after uplink bandwidth is allocated.  

In bandwidth allocation, mainly two types of MPCP messages: GATE and REPORT, are used:  

 

A GATE message is sent by an OLT to assign a transmission timeslot to an ONU.  

 

A REPORT message is sent by an ONU to feed back the local status information, such as buffer 
occupancy, to the OLT, helping the OLT assign timeslots intelligently.  

An OLT allocates bandwidth to an ONU as follows:  

1)  The OLT sends a GATE message to notify the ONU of the timeslot for sending a REPORT 

message.  

2)  The ONU sends a REPORT message within the assigned timeslot to report its local status 

information to the OLT.  

3)  Upon receiving the REPORT message from the ONU, the OLT, based on the current bandwidth of 

the system, assigns the ONU a data transmission timeslot, which contains the start time and length 
for transmitting data by the ONU.  

4)  The ONU receives the GATE message and waits for the arrival of the start time contained in the 

GATE message. Once the start time is reached, data transmission begins.  

5)  The bandwidth allocation is complete.  

Downlink data is broadcast to the ONUs, with each ONU receiving only the packets destined to it and 
discarding other packets, as shown in 

Downlink data transmission in an EPON system   

 

 

As shown in 

, each ONU buffers the data frames received from users and sends the buffered 

data frames at the full wire-speed (1000 Mbps) once the timeslot for the ONU arrives.