Downlink Transmission Preemption Handling for Legacy UE
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Solution Overview
Problem
In mobile networks, the coexistence of new UEs with shorter TTIs and legacy UEs leads to increased delay due to preempting frequency domain resources, causing incorrect receiving and high retransmission delays for legacy UEs during low-delay video services.
Innovation Solution
A downlink transmission method where the base station preempts OFDM symbols from legacy UEs, sends indication information in downlink control signals to the terminal, and retransmits data in subsequent subframes, allowing the terminal to discard incorrect data and perform joint decoding, thereby reducing retransmission delay and improving receiving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the base station preempts frequency domain resources of legacy UE for low-delay video service, then the bandwidth and delay requirements of video service are met, but the receiving performance of legacy UE deteriorates due to incorrect data reception
Solution Approach 1:
The base station segments the downlink data by identifying and separating the preempted resource elements (REs) from the original legacy UE data. The indication information divides the frequency domain resources into preempted and non-preempted portions, allowing the terminal to process them differently. This segmentation enables the terminal to discard only the preempted REs while retaining and correctly decoding the non-preempted REs, thus maintaining receiving performance while supporting resource preemption for video services.
Solution Approach 2:
The indication information acts as an intermediary between the base station and the terminal. It carries the location information of preempted REs, enabling the terminal to identify and discard the correct portions of data without affecting the reception of valid data. This intermediary mechanism resolves the conflict between resource preemption and receiving performance by providing the terminal with the necessary information to distinguish between preempted and non-preempted data.
2Productivity
If the base station preempts resource elements of legacy UE, then high-bandwidth low-delay video service is ensured, but retransmission delay increases to 8 subframes due to incorrect receiving feedback
Solution Approach 1:
The base station performs preliminary action by sending the indication information about preempted REs to the terminal before the terminal attempts to decode the data. This advance notification allows the terminal to proactively discard the preempted REs and avoid incorrect reception, preventing the need for retransmission. By taking this preliminary action, the system eliminates the 8-subframe retransmission delay that would otherwise occur due to HARQ feedback.
3Speed
If new UE with shorter TTI coexists with legacy UE, then low-delay video service is supported, but frequency domain resource allocation becomes inefficient when legacy UE occupies large resources
Solution Approach 1:
The system implements dynamic resource allocation where the base station can flexibly preempt frequency domain resources from legacy UE when low-delay video services require additional bandwidth. The indication information enables dynamic identification of preempted REs, allowing the system to adapt resource allocation in real-time based on service requirements. This dynamic approach ensures that frequency domain resources are efficiently utilized for high-priority video services while maintaining compatibility with legacy UE operations.
Data Source
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AI summary
A downlink transmission method and a corresponding base station and terminal are provided, to improve receiving performance of the terminal. In some feasible implementations, a base station sends downlink control information to a terminal in a subframe n+k, where the downlink control information includes indication information and a HARQ process identification, the indication information is used to indicate a location of at least one OFDM symbol in data that is sent by the base station to the terminal in a subframe n, the HARQ process identification in the downlink control information is the same as a HARQ process identification in the subframe n, and n is a natural number; and the base station transmits, in the subframe n+k, at least data that is sent to the terminal and that is on the at least one OFDM symbol that is in the subframe n and that is indicated by the indication information.