Soft Buffer Control for TDD-FDD Carrier Aggregation
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Solution Overview
Problem
In wireless communication systems, particularly with TDD-FDD carrier aggregation, the soft buffer management for Hybrid Automatic Repeat Request (HARQ) processes is inadequate, leading to insufficient space for storing soft channel bits, which hampers the execution of HARQ processes when frequency resources are scarce and multiple carriers are involved.
Innovation Solution
A method and apparatus for controlling the soft buffer in user equipment (UE) by establishing an RRC connection with a base station, receiving CA configuration information, determining the maximum number of DL HARQ processes based on specific TDD UL-DL configurations, and storing soft channel bits accordingly to optimize soft buffer utilization across multiple carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If TDD-FDD carrier aggregation is configured with multiple component carriers, then the data transmission rate is improved, but the soft buffer space becomes insufficient for storing HARQ processes
Solution Approach 1:
The soft buffer is segmented into multiple separate buffer regions, with each region dedicated to storing soft channel bits for HARQ processes on a specific component carrier. This segmentation allows the limited total buffer space to be efficiently distributed across multiple carriers, enabling the system to support TDD-FDD carrier aggregation with multiple component carriers while maintaining adequate storage capacity for HARQ processes on each carrier.
2Adaptability or versatility
If the number of DL HARQ processes is increased to support multiple carriers, then the HARQ operation capability is improved, but the soft buffer utilization becomes inadequate
Solution Approach 1:
Each component carrier is assigned a dedicated soft buffer region with storage capacity tailored to its specific HARQ process requirements. This local quality approach ensures that each carrier receives adequate buffer space proportional to its data transmission needs, rather than distributing buffer space uniformly. The UE determines the maximum number of DL HARQ processes for each carrier based on its TDD UL-DL configuration, and allocates buffer space accordingly, ensuring reliable HARQ operation on each carrier while optimizing overall buffer utilization.
Data Source
AI summary
Disclosed is a method of performing a Hybrid Automatic Repeat reQuest (HARQ) operation by a user equipment (UE), including: establishing a Radio Resource Control (RRC) connection with a base station through a first serving cell, the first serving cell supporting a Time Division Duplex (TDD) mode; receiving an RRC message from the base station through the first serving cell, the RRC message including carrier aggregation (CA) configuration information, the CA configuration information including information of a second serving cell supporting a Frequency Division Duplex (FDD) mode, and the first serving cell and the second serving cell being aggregated by a TDD-FDD CA scheme; and determining a maximum number of DL HARQ processes for the second serving cell based on a uplink (UL)/downlink (DL) configuration of the first serving cell when the second serving cell is a secondary serving cell (SCell) associated with the first serving cell through the TDD-FDD CA scheme.