eMBMS Packet Transmission Delay Reduction via Sub-Scheduling
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Solution Overview
Problem
Legacy multimedia broadcast multicast services (MBMS) experience significant packet transmission delays, which hinder effective disaster safety communication, particularly in LTE-based systems where the minimum multicast channel scheduling period is 80 ms, leading to additional delays of 80 to 160 ms.
Innovation Solution
The proposed method involves assigning a time stamp to user packets by the broadcast/multicast service center (BM-SC) at intervals shorter than the MBMS scheduling period, allowing base stations to transmit packets immediately upon receipt, rather than waiting for the entire scheduling period, thereby reducing delay by up to 20 ms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the MBMS scheduling period is used for packet transmission, then radio resource utilization efficiency is improved through multi-cell transmission, but packet transmission delay increases by 80 to 160 ms
Solution Approach 1:
The patent segments the MBMS scheduling period into multiple transmission opportunities by introducing sub-scheduling intervals. Instead of transmitting packets only at the end of each 80 ms scheduling period, the system divides the period into smaller time segments (e.g., 20 ms intervals) allowing intermediate transmissions. This segmentation enables packets to be transmitted earlier within the scheduling period, reducing delay while preserving the multi-cell transmission efficiency of the original MBMS framework.
2Stability of the object's composition
If packets are transmitted only at the end of each MBMS scheduling period, then synchronization across multiple base stations is maintained, but transmission delay increases
Solution Approach 1:
The patent applies preliminary action by enabling base stations to transmit packets at intermediate time points within the scheduling period rather than waiting until the end. The system prepares and transmits packets at earlier opportunities (e.g., at 20 ms, 40 ms, 60 ms intervals) based on packet arrival timing, while still maintaining synchronization through coordinated transmission timing. This eliminates the need to wait for the full 80 ms period to elapse before transmission.
Solution Approach 2:
The patent introduces dynamic transmission timing within the MBMS framework. Instead of fixed end-of-period transmission, the system dynamically determines transmission moments based on packet arrival times and scheduling conditions. Base stations can adaptively transmit at various points within the scheduling period (20 ms, 40 ms, 60 ms, or 80 ms) while maintaining synchronization through coordinated dynamic timing adjustments across all cells.
3Loss of time
If the MBMS scheduling period is reduced to decrease delay, then packet transmission delay is reduced, but system complexity and compatibility requirements increase
Solution Approach 1:
The patent achieves universality by making the MBMS scheduling system multi-functional. The same MBMS infrastructure supports both traditional end-of-period transmission and the new intermediate transmission mode. The system can operate with flexible scheduling intervals (20 ms, 40 ms, 60 ms, or 80 ms) depending on traffic conditions, maintaining compatibility with existing MBMS protocols while enabling reduced delay transmission when needed. This multi-functionality avoids the need for separate systems for different transmission requirements.
Data Source
AI summary
A method and an apparatus for reducing delay in enhanced multimedia broadcast multicast services (eMBMS)-based group communication are provided. The method includes receiving the user packet, including information of a time stamp assigned by a broadcast/multicast service center (BM-SC), from the BM-SC, and transmitting the user packet to a terminal through a physical multicast channel based on information of the time stamp, wherein the time stamp is assigned at an interval set to a value less than a multimedia broadcast multicast services (MBMS) scheduling period.