Multicast Sync Ruler Reliability via NACK Feedback
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Solution Overview
Problem
In multicast and broadcast service (MBS) zones, existing synchronization methods face challenges in ensuring reliable frame-level and macro-diversity level synchronization across multiple base stations, particularly in maintaining consistent content transmission and waveform synchronization without efficient retransmission mechanisms.
Innovation Solution
The proposed solution involves dividing the MBS zone into retransmission zones with a selected leader SE in each zone, where the sync controller multicasts a sync ruler, and leader SEs or member SEs request retransmissions using NACK messages to ensure all SEs receive the sync ruler, employing an automatic repeat request (ARQ) procedure and election algorithms to update leader SE information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multicast transmission is used to distribute sync ruler to all SEs, then transmission efficiency is improved, but reliability of synchronization is worsened due to potential packet loss
Solution Approach 1:
The patent implements a feedback mechanism where SEs send NACK (Negative Acknowledgment) messages to the sync controller when they fail to receive the sync ruler. The sync controller monitors these NACK messages and triggers retransmission of the sync ruler to ensure all SEs receive the synchronization information, thereby maintaining reliability while using efficient multicast transmission.
Solution Approach 2:
The patent establishes a recovery period before the sync ruler transmission that allows the sync controller to prepare retransmission resources in advance. This preliminary action ensures that if packet loss occurs during multicast transmission, the sync controller can immediately retransmit the sync ruler without delay, maintaining synchronization reliability.
2Reliability
If retransmission mechanism is implemented to ensure reliable sync ruler delivery, then synchronization reliability is improved, but system complexity is worsened
Solution Approach 1:
The patent introduces a leader SE as an intermediary between individual SEs and the sync controller. The leader SE collects NACK messages from member SEs and communicates with the sync controller, simplifying the retransmission control logic. This intermediary approach reduces the complexity burden on each individual SE while maintaining reliable synchronization through coordinated retransmission.
3Productivity
If leader SE mechanism is implemented to coordinate retransmission, then retransmission effectiveness is improved, but device complexity is worsened due to election algorithms
Solution Approach 1:
The patent implements a leader SE mechanism where one SE is elected to coordinate retransmission requests from other SEs. The leader SE receives NACK messages from member SEs and communicates with the sync controller, centralizing the retransmission control function. This copying approach consolidates complexity in a single entity (the leader) rather than distributing it across all SEs, improving retransmission effectiveness while managing device complexity.
Data Source
AI summary
A reliable synchronization apparatus and method within a multicast and broadcast service (MBS) zone having m sync executers (SEs) belonging to n retransmission zones is provided. Each retransmission zone has a selected leader SE and other member SEs. The apparatus comprises a sync controller and the n selected leader SEs. When the Sync controller multicasts a sync ruler to all SEs in a retransmission zone, the leader SE that loses the Sync ruler sends a NACK message to request the sync controller to retransmit the sync ruler. An election is triggered for updating leader information and announcing election to all SEs. The member SE that loses the sync ruler sends a NACK message to request its leader or the Sync controller to retransmit the sync ruler.