P2MP Network Unit Registration With Shortened Quiet Windows
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Solution Overview
Problem
Existing P2MP networks with TDM face significant latency issues during the activation of new distributed units due to the use of long quiet windows, which are necessary to avoid collisions but are unacceptable for latency-sensitive applications like mobile transport.
Innovation Solution
A two-part activation method is introduced, comprising a first 'noise window' where new and existing distributed units transmit simultaneously, allowing the central unit to detect and decode activation data superimposed on existing transmissions, followed by a second, shorter 'shortened quiet window' for exclusive transmission of the new unit's data, thereby reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a long quiet window is used to avoid collisions during new DU activation, then collision avoidance is improved, but transmission latency increases
Solution Approach 1:
The activation procedure is divided into two distinct phases: a first activation phase where the new DU transmits activation data during a first time window, and a second registration phase where the new DU transmits registration data during a second time window. This segmentation allows the system to separate collision-prone activation signaling from regular upstream data transmissions, enabling shorter quiet windows while maintaining reliability.
Solution Approach 2:
The new distributed unit transmits its activation data (including estimated round-trip time information) in advance during the first time window before the quiet window is opened. This preliminary transmission of activation information allows the central unit to prepare and open the quiet window at the appropriate time, reducing the overall activation latency while ensuring collision-free registration.
2Adaptability or versatility
If the quiet window is opened to cover maximum distance spread, then all DUs can be accommodated, but latency for latency-sensitive applications increases
Solution Approach 1:
The system changes the timing parameters dynamically based on the new DU's estimated round-trip time. The central unit opens the quiet window at a time calculated from the estimated RTT, rather than using a fixed maximum window duration. This parameter adjustment allows the system to accommodate DUs at various distances while minimizing the quiet window duration and associated latency for latency-sensitive applications.
3Loss of time
If an additional physical transmission channel is used for activation, then normal transmission is not delayed, but cost and complexity increase
Solution Approach 1:
The existing upstream transmission channel is used for multiple purposes: both for carrying activation data from new DUs and for carrying regular upstream data from active DUs. The central unit distinguishes between these different types of transmissions through timing and protocol mechanisms, eliminating the need for separate physical hardware channels while maintaining low latency activation.
4Loss of time
If an additional logical transmission channel is used with low-speed transmission, then quiet window duration is reduced, but detection time increases
Solution Approach 1:
The system uses brief, intensive transmission bursts for activation data rather than sustained low-speed transmission. The activation data is transmitted in concentrated time windows with higher signal characteristics, making it easier to detect quickly despite the overall reduced quiet window duration. This approach sacrifices neither detection reliability nor activation speed.
Data Source
AI summary
Various examples relate to a central unit and a corresponding method and computer program, to a distributed unit and a corresponding method and computer program, to an optical line terminal comprising a central unit, to an optical networking unit comprising a distributed unit, and to a system comprising a central unit and one or more distributed units. The central unit for a time-division multiplexed (TDM) point-to-multipoint (P2MP) network comprises circuitry configured to grant, during a first time window, a first distributed unit not yet registered to the TDM P2MP network to transmit first activation data to the central unit. The circuitry is configured to grant, during the first time window, at least one second distributed unit already registered to the TDM P2MP to transmit upstream data to the central unit. The central unit is configured to receive the first activation data during the first time window. The central unit is configured to determine an estimate for a round-trip time of the first distributed unit based on the first activation data and a length of a second time window based on the estimate for the round-trip time. The circuitry is configured to grant exclusively the first distributed unit to transmit second activation data to the central unit during the second time window. The circuitry is configured to register the first distributed unit to the TDM P2MP network based on the second activation data.