Grant-Free Uplink Reference Signal Allocation for Wireless Contention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless communication systems, the grant-free based uplink data transmission method faces challenges with signal contention among multiple UEs using the same resource, leading to decoding failures and increased latency, especially when channel status and data size changes occur.
Innovation Solution
The proposed method involves semi-static allocation of grant-free UL resources, using orthogonal reference signals for initial and retransmission, and dynamic allocation of resources based on UE-specific and UE-common channels to minimize contention and ensure reliable data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple UEs transmit uplink data through the same grant-free UL resource, then resource utilization is improved and latency is reduced, but signal contention occurs leading to decoding failures
Solution Approach 1:
The patent applies local quality by assigning different reference signal characteristics to different UEs or transmission instances. Specifically, different UEs are allocated different cyclic shifts or orthogonal cover codes for their reference signals, creating local differentiation within the common grant-free resource. This allows the system to maintain common resource usage while providing UE-specific identification, thereby resolving the contention issue without sacrificing resource utilization efficiency.
2Loss of time
If grant-free UL transmission is used for faster data transmission, then latency is reduced, but contention among UEs increases causing transmission failures
Solution Approach 1:
The patent implements dynamics by enabling flexible switching between grant-free transmission and grant-based retransmission. When contention is detected (through decoding failures), the system dynamically transitions to grant-based mode for retransmission, while maintaining grant-free mode for initial transmissions. This dynamic adaptation allows the system to optimize for low latency when conditions permit while ensuring reliability when contention occurs.
3Device complexity
If UE-common resources are allocated for grant-free transmission, then resource allocation efficiency is improved, but contention likelihood increases due to synchronous transmission from multiple UEs
Solution Approach 1:
The patent applies segmentation by dividing the reference signal resource space into multiple orthogonal segments that can be assigned to different UEs. Through cyclic shifts, orthogonal cover codes, or other orthogonalization techniques, the reference signals are segmented in a way that maintains orthogonality even when multiple UEs transmit simultaneously on the same grant-free resource. This segmentation approach reduces contention likelihood while maintaining the simplicity of UE-common resource allocation.
Data Source
AI summary
Provided are a method and an apparatus for transmitting grant-free based uplink data in a wireless communication system. Specifically, a terminal receives, from a base station, allocation information for a grant-free uplink resource that is semi-statically allocated. The terminal receives, from the base station, allocation information for a first reference signal used for initial transmission of uplink data and allocation information for a second reference signal used for retransmission of the uplink data. The terminal transmits the uplink data through the grant-free uplink resource by using the first reference signal. If decoding of the uplink data fails, the terminal receives, from the base station, an uplink grant corresponding to the second reference signal. The terminal retransmits the uplink data by using the second reference signal on the basis of the uplink grant. The first reference signal is commonly allocated to the terminal, and the second reference signal is specifically allocated to the terminal.