PUSCH Configurations for RACH-Less Handover Latency
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Solution Overview
Problem
Current wireless communication systems face latency issues during handover procedures, particularly when involving random access channel (RACH) processes, leading to increased interruption times for user equipment (UE) as it transitions between base stations.
Innovation Solution
The implementation of physical uplink shared channel (PUSCH) configurations and occasions that allow for RACH-less handover procedures, where the UE receives a PUSCH configuration for transmitting a handover completion message, including waveform, numerology, and modulation scheme settings, enabling efficient handover without the need for RACH procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RACH procedures are used during handover, then the handover process is more reliable and robust, but the handover latency and interruption time increase
Solution Approach 1:
The patent extracts and removes the RACH procedure from the handover process, allowing the UE to directly transmit the handover completion message on PUSCH resources allocated by the target base station. This eliminates the time-consuming random access steps while maintaining connection reliability through pre-configured uplink resources.
Solution Approach 2:
The source base station pre-configures PUSCH resources and provides uplink grants to the UE before the handover is executed. The target base station also pre-allocates PUSCH occasions for the handover completion message. This preliminary setup eliminates the need for real-time resource negotiation during handover, reducing latency while ensuring reliable transmission.
2Reliability
If RACH procedures are performed during handover, then the random access process ensures proper synchronization and resource allocation, but the overall handover speed decreases
Solution Approach 1:
All necessary synchronization information and resource allocation details are provided to the UE in advance through the handover command message. The target base station pre-allocates PUSCH resources and provides uplink grants before the UE needs to transmit the handover completion message, eliminating the need for real-time RACH procedures.
Solution Approach 2:
The patent uses the existing PUSCH resource allocation mechanisms and uplink grant structures from normal scheduling, copying them for handover purposes. This allows the system to leverage already-tested and reliable resource allocation methods without introducing new procedures, maintaining reliability while improving speed.
3Reliability
If traditional handover procedures with multiple signaling steps are used, then the handover is more robust and error-resistant, but the communication interruption time increases
Solution Approach 1:
The patent extracts and removes unnecessary signaling steps from the traditional handover procedure. By eliminating the RACH preamble transmission, random access response, and contention resolution steps, the handover process is streamlined to only the essential operations, reducing interruption time while maintaining robustness through pre-configured resources.
Solution Approach 2:
The patent merges the handover execution and handover completion reporting into a single streamlined process. The UE transitions directly to the target cell and immediately uses pre-allocated PUSCH resources to send the completion message, combining multiple separate signaling operations into one efficient sequence that reduces overall interruption time.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may identify physical uplink shared channel (PUSCH) configuration parameters to send a handover completion message at the end of a handover. A source cell may notify the UE of a handover via a handover command and the UE may acquire system information, and in some cases, a downlink message, from a target cell. The UE may identify a waveform configuration, numerology configuration, and/or modulation scheme using information from the handover command message, the system information, and/or the downlink message. The UE may also determine occasions for transmitting a PUSCH. For example, each occasion may include a set of time-frequency resources on which the PUSCH may be transmitted. The UE may send the handover completion message to the target cell via the PUSCH, during the one or more identified occasions, using the identified configuration parameters.