Distributed PON Bandwidth Control via Segmented Channels
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Solution Overview
Problem
Current passive optical network (PON) systems face low bandwidth utilization, high delay, and lack of quality of service due to centralized network access control, where ONUs must wait for OLT confirmation and share control channels with upstream data, leading to inefficient bandwidth allocation and potential collisions.
Innovation Solution
A distributed controlled PON system with a splitter and combiner architecture, where each ONU has separate Tx/Rx for data and control channels, allowing ONUs to execute a dynamic bandwidth allocation (DBA) algorithm independently, determining access without OLT involvement, using mini-slots for control signals and fixed slots for data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If centralized network access control is used where OLT polls ONUs or ONUs use piggyback to add backlog data, then bandwidth allocation can be controlled centrally, but the signaling time becomes several hundreds of microseconds to milliseconds, causing high delay and low bandwidth utilization
Solution Approach 1:
The patent segments the control function from the data transmission function by introducing a separate control channel. Control signals are transmitted independently from upstream data, allowing ONUs to exchange control information without waiting for OLT polling cycles. This segmentation eliminates the need for round-trip signaling to OLT for bandwidth allocation decisions, reducing delay from hundreds of microseconds to minimal propagation time.
Solution Approach 2:
The patent introduces a control channel as an intermediary mechanism between ONUs. Instead of direct OLT-ONU polling interaction, ONUs use the control channel to communicate bandwidth allocation information and coordination signals among themselves. This intermediary channel enables distributed control without requiring centralized OLT involvement in every bandwidth allocation decision, significantly reducing signaling delay.
2Device complexity
If control channel and upstream data share the same channel, then device complexity is reduced, but bandwidth utilization decreases and collisions may occur requiring waiting until all ONUs finish transmitting
Solution Approach 1:
The patent segments the communication medium into two distinct channels: a control channel for bandwidth allocation and coordination signals, and an upstream data channel for actual data transmission. This segmentation allows control signals to be transmitted without interfering with data traffic, eliminating collisions and enabling continuous bandwidth allocation updates without waiting for transmission cycles to complete.
Solution Approach 2:
By separating control and data channels, the patent enables continuous control signal transmission independent of data transmission cycles. ONUs can continuously exchange bandwidth allocation information on the control channel while data flows continuously on the upstream data channel, eliminating idle waiting periods and maximizing bandwidth utilization.
3Adaptability or versatility
If ONU switches off, then ONU can determine when to transmit independently, but other ONUs cannot hear the transmission and may keep waiting indefinitely, causing network-wide delay
Solution Approach 1:
The patent implements a feedback mechanism where ONUs monitor the control channel for status information from other ONUs. When an ONU switches off or stops transmitting, other ONUs detect this through the control channel feedback and update their transmission schedules accordingly. This feedback loop prevents other ONUs from waiting indefinitely, as they receive real-time status updates and can immediately adjust their transmission timing.
Solution Approach 2:
The patent replaces the mechanical listening-waiting-transmitting sequence with an information-based control system. Instead of ONUs physically listening for transmissions and waiting in silence, the control channel carries explicit status information about which ONUs are active and when they will transmit. This substitution transforms the collision avoidance mechanism from passive waiting to active information-driven coordination, eliminating unnecessary delays.
Data Source
AI summary
Disclosed is a distributed controlled passive optical network system and bandwidth control method thereof. The system comprises an optical line terminal (OLT), plural optical network units (ONUs) and a splitter with combiner. Each ONU has a first Tx/Rx for respectively transmitting and receiving data packets on an upstream data channel and a downstream data channel, and a second Tx/Rx for transmitting and receiving control signals/commands on a control channel. Upstream data of each ONU is carried by the upstream data channel and sent to the OLT through the splitter with combiner. Downstream data of the OLT is carried by the downstream data channel and sent to corresponding ONUs through the splitter with combiner. With the control signals/commands carried by the control channel, the required information of network status among the ONUs is provided.