Group Communication Synchronization During Unicast Multicast Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In LTE group communication systems, RTP packets received by UE on different data transmission paths before and after switching from unicast to multicast or vice versa become out of order and out of synchronization, leading to packet loss or repeated reception due to differing transmission delays.
Innovation Solution
A method where the GCS AS measures and calculates the time difference in RTP packet reception timestamps before and after switching, adjusting the transmission timing in the unicast manner to synchronize packets, and the UE reports measurement results using a quality of experience metric to facilitate delay compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the GCS AS transmits RTP packets using unicast manner, then the transmission delay is 40 ms, but when switching to multicast manner with 160 ms delay, the packets become out of synchronization and out of order
Solution Approach 1:
The system performs preliminary measurement of transmission delays for both unicast and multicast paths before switching occurs. The GCS AS sends measurement packets through both paths and records the time differences, so that when switching is needed, the pre-calculated delay compensation values can be immediately applied to maintain synchronization without causing packet disorder.
2Adaptability or versatility
If the UE switches between unicast and multicast transmission paths, then the system adapts to different coverage conditions, but the different transmission delays cause packets to be out of order and potentially lost or duplicated
Solution Approach 1:
The UE continuously measures the reception time of RTP packets from both unicast and multicast paths and reports these timing measurements back to the GCS AS. Based on this feedback, the GCS AS dynamically calculates the delay difference between the two paths and adjusts the transmission timing accordingly, ensuring that packets arrive in order regardless of which path is used.
Solution Approach 2:
The system changes the timing parameter of RTP packet transmission based on the measured delay difference between unicast and multicast paths. When switching between transmission modes, the GCS AS applies the calculated delay compensation to adjust the transmission timing, transforming the fixed delay characteristics into adaptive timing that maintains synchronization across different transmission paths.
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The present invention discloses a group communication method, apparatus, and device. The method includes: when a Real-Time Transport Protocol RTP packet receiving manner of user equipment UE is switched, obtaining, by a group communication service application server GCS AS, a time difference between a time at which the UE receives a first RTP packet before the switching and a time at which the UE receives a second RTP packet after the switching, where the receiving manner includes a unicast transmission manner and a multicast transmission manner; calculating, by the GCS AS according to the time difference, a delay difference of transmitting an RTP packet in different transmission manners; and adjusting, according to the delay difference, a time at which the RTP packet is transmitted in the unicast transmission manner. Therefore, the following problem is resolved: RTP packets received by the UE on different data transmission paths that are used before and after the switching are out of order and out of synchronization (for example, a packet may be lost or repeatedly received).