Cross-Carrier HARQ Feedback Mapping for TDD Uplink-Downlink Mismatch
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Solution Overview
Problem
In Time Division Duplex (TDD) communication systems, the feedback performance of Hybrid Automatic Repeat Request (HARQ) information is poor due to the differing quantities of uplink and downlink subframes, which affects system throughput.
Innovation Solution
Establishing a correspondence between uplink subframes on a Frequency Division Duplex (FDD) carrier and downlink subframes on a TDD carrier, allowing for one-to-one mapping and improved resource allocation for HARQ information feedback, including determining UL/DL configuration modes and resource parameters for efficient HARQ transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If binding or multiplexing manner is used to feed back HARQ information in TDD system, then feedback can be implemented despite different quantities of uplink and downlink subframes, but feedback performance is relatively poor
Solution Approach 1:
The patent introduces FDD carrier uplink subframes as an additional dimension for HARQ feedback transmission. Instead of only using TDD carrier uplink subframes (which are limited in number), the patent maps downlink subframes on TDD carrier to uplink subframes on FDD carrier, creating a new feedback path that bypasses the uplink-downlink subframe quantity mismatch problem in TDD systems.
Solution Approach 2:
The patent uses FDD carrier uplink subframes as an intermediary resource for transmitting HARQ feedback. The base station configures the UE to map HARQ-ACK information from TDD downlink subframes to FDD uplink subframes through cross-carrier feedback, where the FDD carrier acts as a mediator that resolves the subframe quantity mismatch between uplink and downlink in TDD mode.
2Ease of operation
If multiple downlink subframes are bound or multiplexed to one uplink subframe, then feedback can be transmitted in TDD system, but feedback performance deteriorates
Solution Approach 1:
The patent segments the HARQ feedback transmission by establishing one-to-one correspondence between downlink subframes on TDD carrier and uplink subframes on FDD carrier. Instead of multiplexing multiple downlink subframes into one uplink subframe (which causes performance degradation), each downlink subframe gets its own dedicated uplink subframe on the FDD carrier for feedback transmission.
Solution Approach 2:
The FDD carrier uplink subframes serve multiple functions: they provide HARQ feedback for TDD downlink subframes while maintaining their own FDD uplink-downlink communication capabilities. This multi-functionality allows the system to leverage FDD carrier resources to solve TDD feedback performance issues without compromising FDD operation.
3Adaptability or versatility
If uplink and downlink subframes are differently configured in TDD system, then TDD operation is enabled, but direct one-to-one HARQ feedback mapping becomes difficult
Solution Approach 1:
The base station acts as an intermediary that configures and manages the cross-carrier feedback mapping. It provides signaling to the UE to establish the correspondence between TDD downlink subframes and FDD uplink subframes, thereby simplifying the complexity that would otherwise exist in the UE for determining the mapping relationship.
Solution Approach 2:
The patent changes the feedback transmission parameter by switching from same-carrier feedback (TDD uplink subframes) to cross-carrier feedback (FDD uplink subframes). This parameter change enables one-to-one mapping despite the different uplink-downlink configurations in TDD mode, as the FDD carrier provides sufficient uplink subframes regardless of TDD configuration.
Data Source
AI summary
A communication method includes: determining a correspondence between Y uplink subframes and X downlink subframes, where the Y uplink subframes are used to respectively transmit HARQ information that is corresponding to the X downlink subframes, at least one uplink subframe of the Y uplink subframes is an uplink subframe on an FDD carrier, and the X downlink subframes are downlink subframes in one radio frame on a TDD carrier; and communicating with UE according to the correspondence.