Downlink Small Data Transmission in Inactive RRC State
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Solution Overview
Problem
Current wireless communication systems face inefficiencies in downlink small data transmission for wireless transmit/receive units (WTRUs) in inactive radio resource control (RRC) states, leading to high power consumption and significant signaling overhead due to frequent state transitions and blind decoding of control channels.
Innovation Solution
Implementing procedures for downlink small data transmission that allow WTRUs to remain in an inactive RRC state while decoding and responding to downlink small data transmissions without transitioning to a connected state, using techniques such as DL SDT capability indication, dynamic configuration of PDSCH resources, and multiplexing HARQ feedback with RACH preambles, to reduce power consumption and signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If WTRUs transition to connected state for downlink data reception, then data transmission reliability is improved, but power consumption increases and signaling overhead increases
Solution Approach 1:
The patent segments the traditional connected-state data reception process into two parts: (1) remain in inactive state for small downlink data reception using wake-up signals and pre-configured resources, and (2) transition to connected state only when necessary for larger data transmissions. This segmentation allows the system to maintain reliability for small data while reducing power consumption by avoiding unnecessary state transitions.
Solution Approach 2:
The patent implements preliminary configuration of downlink data reception parameters (such as PDSCH resources, HARQ processes, and uplink feedback resources) while the WTRU is still in inactive state. The network pre-allocates these resources and the WTRU stores the configuration, enabling immediate data reception without transitioning to connected state, thus reducing power consumption while maintaining transmission reliability.
2Reliability
If WTRUs transition to connected state for downlink data reception, then data transmission reliability is improved, but signaling overhead increases
Solution Approach 1:
The patent segments the signaling process by separating wake-up indication signaling from full data transmission signaling. The network sends a compact wake-up signal (e.g., 1-bit indication) to trigger small data reception, avoiding the need for extensive RRC signaling that would occur with a full connected state transition. This reduces signaling overhead while maintaining reliable data delivery.
Solution Approach 2:
The network performs preliminary signaling to configure downlink data reception parameters while the WTRU is in inactive state. Configuration messages containing PDSCH resource allocations, HARQ process IDs, and uplink feedback resource indications are sent in advance and stored by the WTRU. When small data needs to be transmitted, the network simply activates pre-configured resources rather than establishing new connections, significantly reducing signaling overhead.
3Ease of operation
If WTRUs decode control channels frequently, then data reception capability is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic wake-up signals that the network transmits at predetermined intervals to indicate the presence of downlink small data. Instead of requiring continuous control channel monitoring, the WTRU only needs to wake up periodically to check for these compact wake-up signals. This periodic action maintains data reception capability while dramatically reducing power consumption compared to continuous monitoring.
Solution Approach 2:
The patent extracts the essential function of data reception indication from the complex control channel decoding process. Instead of requiring full PDCCH decoding with multiple blind decoding attempts, the system uses simplified wake-up signals that can be detected with minimal processing. This extraction of the core indication function reduces the computational burden and power consumption while maintaining the ability to receive data.
4Use of energy by moving object
If WTRUs remain in inactive state for downlink data reception, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The network performs preliminary configuration of all necessary data reception parameters (PDSCH resources, HARQ processes, uplink feedback resources, modulation schemes) while the WTRU is in inactive state. These configurations are stored in the WTRU's memory and automatically activated when a wake-up signal is received. This preliminary action eliminates the need for complex real-time decision-making and resource allocation during data reception, keeping device complexity manageable while enabling power-efficient inactive state operation.
Solution Approach 2:
The WTRU uses pre-configured parameters and automatic activation mechanisms to handle downlink data reception independently while in inactive state. Upon receiving a wake-up signal, the WTRU automatically activates the stored configuration and begins data reception without needing to establish a full RRC connection or engage in complex signaling exchanges. This self-service capability reduces device complexity by eliminating the need for complex state transition logic while maintaining power efficiency.
Data Source
AI summary
Procedures, methods, architectures, apparatuses, systems, devices, and computer program products are disclosed that may be implemented in a wireless transmit/receive unit (WTRU), such as where the WTRU is in an inactive and/or idle (e.g., RRC) state. In one representative method, the WTRU may receive a downlink (DL) small data transmission (SDT) indication with respect to a paging occasion. The WTRU may receive the indicated DL SDT payload which may be multiplexed with a paging record for the paging occasion and/or with one or more configured DL SDT PDSCH resources. Hybrid automatic repeat request (HARQ) feedback information for the DL SDT payload may be transmitted using configured PUCCH resources and/or may be multiplexed with a random access channel (RACH) procedure. The DL SDT payload may be received by the WTRU without transitioning to a connected (e.g., RRC) state.