ACK/NACK Feedback Overhead Reduction in LTE Component Carriers
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Solution Overview
Problem
In LTE radio communication systems, the existing methods for feeding back ACK/NACK information in HARQ transmissions face challenges such as increased Cubic Measurement (CM) values and reduced uplink signal coverage due to the occupation of multiple ACK/NACK channels, which affects data transmission efficiency and coverage.
Innovation Solution
A method is introduced where a mobile terminal calculates and feeds back the number of ACKs for each Component Carrier (CC), allowing ACK/NACK information to be transmitted on at most two channels, using spatial bundling and multiple-to-one mapping to reduce overhead and maintain single-carrier characteristics, thereby controlling CM values and enhancing uplink coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple ACK/NACK channels are occupied for transmitting ACK/NACK information of multiple Component Carriers, then the coverage of ACK/NACK transmission is improved, but the Cubic Measurement (CM) value increases and uplink signal coverage is reduced
Solution Approach 1:
The patent combines ACK/NACK information from multiple Component Carriers into a single uplink sub-frame transmission. Instead of occupying multiple ACK/NACK channels simultaneously, the mobile terminal aggregates ACK/NACK feedback for multiple CCs and transmits them together on one channel, thereby reducing CM values and maintaining uplink signal coverage while ensuring reliable ACK/NACK transmission.
Solution Approach 2:
The patent enables a single ACK/NACK channel to serve multiple Component Carriers simultaneously. The uplink control information structure is designed to accommodate ACK/NACK feedback from multiple CCs within one channel, making the channel multi-functional and eliminating the need for separate dedicated channels for each CC, thus reducing overall system CM values.
2Productivity
If ACK/NACK information of multiple downlink sub-frames is transmitted on one uplink sub-frame, then the feedback efficiency is improved, but the complexity of determining ACK/NACK channel increases
Solution Approach 1:
The patent applies spatial bundling and multiple-to-one mapping in advance to consolidate ACK/NACK information from multiple downlink sub-frames and multiple Component Carriers into a unified feedback structure before transmission. This preliminary consolidation simplifies the channel determination process by pre-organizing the feedback data, allowing the mobile terminal to determine the appropriate ACK/NACK channel more easily despite the multi-sub-frame, multi-CC scenario.
Data Source
AI summary
Embodiments of the present invention provide a method for feeding back ACK/NACK for downlink data transmission in a radio communication system. The method is applied on a mobile terminal and includes the following steps: receiving downlink data, calculating, with respect to each Component Carrier (CC), a number of ACKs of ACK/NACK information of downlink data sub-frames of the CC, and feeding back numbers of ACKs of the ACK/NACK information of the downlink data sub-frames of CCs.