RACH Preamble Feedback for Idle-State Wireless Multicast
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Solution Overview
Problem
Existing wireless communication systems face challenges in supporting efficient wireless feedback, such as HARQ-ACK and CSI feedback, in idle or inactive states due to the lack of time/frequency resources for devices in RRC_IDLE or RRC_INACTIVE modes, which affects the performance of multicast and broadcast services.
Innovation Solution
The proposed techniques utilize 4-step random access channels and procedures to enable HARQ-ACK and CSI feedback in RRC_IDLE or RRC_INACTIVE states by employing separate and joint coding schemes for preambles, allowing simultaneous or sequential transmission of feedback and random access, and optimizing resource allocation through frequency, time, and code division multiplexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate coding schemes for preambles are employed to enable HARQ-ACK and CSI feedback in idle/inactive states, then feedback performance is improved, but device complexity increases
Solution Approach 1:
The patent segments the feedback mechanism by introducing separate coding schemes for different feedback types (HARQ-ACK and CSI). Different preamble sequences are assigned to different feedback scenarios, allowing the system to handle multiple feedback requirements through structured segmentation of code resources rather than a unified complex coding approach.
Solution Approach 2:
The random access preamble structure is designed to serve multiple functions simultaneously. The same preamble transmission mechanism is used for both traditional random access and for conveying HARQ-ACK and CSI feedback, enabling the system to achieve multi-functionality without adding separate dedicated feedback channels for idle/inactive devices.
2Productivity
If simultaneous transmission of feedback and random access is enabled, then resource utilization is improved, but interference management becomes more difficult
Solution Approach 1:
The patent merges the feedback transmission with the random access procedure by allowing HARQ-ACK and CSI feedback to be conveyed through the random access preamble itself. This combining approach enables simultaneous transmission of feedback and random access signaling in the same time-frequency resources, improving resource utilization while managing interference through unified sequence design.
Solution Approach 2:
Different local qualities (preamble sequences with distinct correlation properties) are assigned to different feedback types and scenarios. The system employs locally optimized preamble sequences that maintain good correlation properties even when multiple devices transmit simultaneously, thereby managing interference through localized sequence design rather than global resource allocation.
3Productivity
If RACH occasions are optimized for feedback transmission, then feedback efficiency is improved, but random access performance may deteriorate
Solution Approach 1:
The patent resolves the conflict by introducing another dimension (code domain) for resource allocation. Instead of competing for the same time-frequency resources, different preamble sequences are allocated in the code domain, allowing feedback transmission and random access to coexist in the same time-frequency resources without mutual interference, thus maintaining both feedback efficiency and random access performance.
Data Source
AI summary
Techniques are described for performing feedback by a communication device. An example wireless communication method includes receiving, by a communication device, X shared channels from a network device, where the X shared channels are located in between a first random access channel (RACH) instance and a second RACH instance in time domain, where the second RACH instance includes Y RACH occasions in time domain, where X and Y are integers, and where Y is greater than or equal to X; and transmitting, by the communication device, a preamble in at least one RACH occasion from the Y RACH occasions, where the preamble indicates exactly one of: (1) a feedback associated with a shared channel from the X shared channels, or (2) a random access.