PDCP Sequence Initialization for Mid-Session MBS Reception
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Solution Overview
Problem
Existing mobile communication systems face challenges in providing seamless multicast broadcast services, particularly for user equipment joining a session mid-stream, due to issues with header compression and PDCP variable configuration, leading to unsuccessful packet reception and operation.
Innovation Solution
The proposed solution involves transmitting header information separately from compressed multicast broadcast service packets and configuring PDCP variables based on the sequence number of the first received packet, allowing user equipment to successfully receive and process multicast data by establishing initial values for PDCP variables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If header compression is applied to multicast broadcast service packets, then transmission efficiency is improved, but user equipment joining mid-session cannot successfully receive and process packets due to missing initial header information
Solution Approach 1:
The patent applies preliminary action by transmitting initial header information to user equipment before compressed multicast packets arrive. This ensures that when UE joins mid-session, it already possesses the necessary header context (including PDCP configuration and initial sequence numbers) to successfully decompress and process subsequent compressed packets, thereby resolving the reliability issue while maintaining transmission efficiency
2Ease of operation
If PDCP variables are initialized to default values, then processing is simplified, but packet reception fails when UE joins a session in progress due to sequence number mismatch
Solution Approach 1:
The patent applies local quality by differentiating the initialization approach based on UE joining timing. For early-joining UE, default initialization suffices, but for mid-session joiners, the patent locally adapts by transmitting the actual initial PDCP variables (especially sequence numbers) from the network, ensuring each UE group receives appropriate initialization tailored to their joining context
Solution Approach 2:
The patent implements feedback mechanisms where the network monitors UE joining status and dynamically adjusts header information transmission. When mid-session joining is detected, the network provides feedback by transmitting the current initial sequence numbers and PDCP variables, enabling synchronized state alignment between network and UE
3Adaptability or versatility
If mid-session joining is supported, then service accessibility is improved, but header decompression and PDCP operations fail due to uninitialized variables
Solution Approach 1:
The patent introduces an intermediary mechanism in the form of explicit initial header information transmission. This intermediary step bridges the gap between compressed packet transmission and mid-session UE capabilities, by inserting a preparatory phase where initial PDCP variables and header templates are transmitted, enabling subsequent successful decompression and processing
Data Source
AI summary
A communication control method used in a mobile communication system, the mobile communication system providing a multicast broadcast service (MBS) from a network node to a user equipment. The communication control method comprises receiving, by the user equipment, an MBS packet from the network node; and configuring, by a Packet Data Convergence Protocol (PDCP) entity of the user equipment, based on a PDCP sequence number included in the MBS packet received first from the network node, an initial value of a PDCP variable. The PDCP variable is at least one of a first variable and a second variable. The first variable includes a sequence number of next PDCP SDU expected to be received. The second variable includes a sequence number of the oldest of PDCP SDUs awaiting being received and not yet provided to the higher layer.