GPON-EPON’s key technologies
DBA & T-CONT
No matter in R&D design, product selling, project integration or after-sales support area, there are multiple technical specifications and parameters appearing in GPON-EPON OLT and ONT/ONU equipment devices. It would be a great idea to let our friends and customers to know full list of those specifications & parameters.
FOT Blog is going to make a series of introductions and detail exhibitions on GPON-EPON products key technologies, in the following and coming articles/blog:
DBA: Dynamically Bandwidth Assignment/Allocation
DBA, Dynamic bandwidth allocation is a technique by which traffic bandwidth in a shared telecommunications medium can be allocated on demand and fairly between different users of that bandwidth.
This is a form of bandwidth management, and is essentially the same thing as statistical multiplexing. Where the sharing of a link adapts in some way to the instantaneous traffic demands of the nodes connected to the link. Dynamic bandwidth allocation takes advantage of several attributes of shared networks:
Why do we need DBA?
(1) all users are typically not connected to the network at one time.
(2) even when connected, users are not transmitting data (or voice or video) at all times.
(3) most traffic occurs in bursts.
There are gaps between packets of information that can be filled with other user traffic. Different network protocols implement dynamic bandwidth allocation in different ways. These methods are typically defined in standards developed by standards bodies such as the ITU, IEEE, FSAN, or IETF. One example is defined in the ITU G.983 specification for passive optical network (PON).
What is the Principle of DBA?
1)OLT’s internal DBA module will collect the related report information continuously and caculated,then dispatch results to ONU by “BW-Map” information.
2)Based on this BW-Map information, each ONU will send their own burst uplink data ,in the respective transmission time slot，thus the uplink bandwidth is occupied.
T-CONTs : Transmission Containers
T-CONT is used to improve the PON system upstream bandwidth allocation and transmission status,after receiving the OLT authorization dynamically.
- Is a bearer service cache.
- The ONU unit,mainly used to transmit uplink data.
- Is to solve the dynamic allocation of upstream bandwidth.
- According to each ONU actual hardware, T-CONT number will be different.
- T-CONT ID is used to identify the different cache (ONU).
- ALLOCATE ID is used to identify all the ONT T-CONTs from the same PON port (OLT).
As we know,bandwidth types can be divided into as following:
- FB: Fixed Bandwidth
- AB: Assured Bandwidth
- NAB: Non-assured Bandwidth
- BE: Best-Effort Bandwidth
Accordingly,there are 5 types of T-CONTs: Type1,Type2,Type3,Type4,Type5,more detail shown in the picture above.
Relationship between T-CONTs and Bandwidths
Form is a ideal tool to explain what is the relationship between T-CONTs and Bandwidth.
The next coming topic will be still focus on those key technologies inside GPON and EPON equipment,hoping you would like it.