LTE TDD Uplink ACK/NACK Feedback Configuration
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Solution Overview
Problem
In Long Term Evolution (LTE) wireless communication systems using time division duplex (TDD), there is a challenge in efficiently transmitting uplink acknowledgment/non-acknowledgment (ACK/NACK) messages, particularly when there are fewer uplink subframes than downlink subframes, leading to coverage issues and potential mismatches between user equipment and eNode B expectations due to missed scheduling assignments.
Innovation Solution
The method involves selecting between bundled feedback and multiple feedback configurations for ACK/NACK transmission, using one uplink subframe to acknowledge multiple downlink subframes, and employing different bit configurations and channel quality indicator transmissions to ensure accurate ACK/NACK resource indication, tied to the lowest control channel element index or subframe group, to optimize ACK/NACK resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ACK/NACK bundling is used to transmit a single acknowledgment, then coverage of the physical uplink control channel is significantly increased, but the ability to maximize system throughput in good coverage areas is compromised
Solution Approach 1:
The system dynamically selects between bundled feedback and multiple feedback configurations based on coverage conditions. User equipment in coverage-limited situations uses bundled feedback (single ACK/NACK) to ensure reliable transmission, while user equipment in good coverage areas uses multiple feedback configurations to maximize throughput. This dynamic adaptation resolves the contradiction by allowing each user equipment to operate in the optimal mode for its specific coverage condition.
Solution Approach 2:
The patent changes the feedback configuration parameter based on coverage conditions. The network can configure user equipment to use either bundled feedback (reducing feedback to a single acknowledgment) or multiple feedback configurations (transmitting multiple ACK/NACK bits). This parameter change allows the system to adapt feedback granularity to coverage requirements, improving reliability when needed and maintaining throughput capability when coverage is sufficient.
2Productivity
If multiple ACK/NACK bits are transmitted to maximize system throughput, then coverage of the physical uplink control channel deteriorates
Solution Approach 1:
The system dynamically adjusts the number of ACK/NACK bits transmitted based on user equipment coverage conditions. In good coverage areas, multiple ACK/NACK bits are transmitted to maintain high system throughput. In coverage-limited situations, the system transitions to bundled feedback mode, transmitting a single acknowledgment to ensure reliable delivery. This dynamic adjustment resolves the contradiction by matching feedback complexity to coverage capability.
Solution Approach 2:
The patent implements parameter changes in the feedback configuration, allowing the network to specify whether user equipment should transmit bundled feedback (single bit) or multiple feedback configurations (multiple bits). This parameter control enables the system to optimize the balance between throughput and coverage by adjusting feedback granularity according to actual channel conditions and user equipment location.
3Reliability
If user equipment schedules data reception using multiple subframes in coverage-limited situations, then the complexity of ACK/NACK transmission increases due to potential missed scheduling assignments
Solution Approach 1:
The patent extracts the complexity of tracking multiple scheduling assignments by implementing bundled feedback, which consolidates multiple ACK/NACK responses into a single transmission. This extraction simplifies the feedback mechanism for coverage-limited user equipment, removing the burden of managing complex multiple-assignment tracking while maintaining reliable coverage through the robust bundled feedback approach.
Solution Approach 2:
The patent segments user equipment into different categories based on coverage conditions, with coverage-limited user equipment using bundled feedback and well-covered user equipment using multiple feedback configurations. This segmentation allows each group to use the appropriate complexity level, reducing overall system complexity for coverage-limited devices while maintaining high performance for devices in good coverage areas.
Data Source
AI summary
A method for uplink ACK/NACK for LTE TDD. The method includes receiving a frame having multiple subframes wherein a plurality of subframes being downlink subframes and at least one subframe being an uplink subframe. One uplink subframe can contain an acknowledgment/non-acknowledgment (ACK/NACK) corresponding to at least one of the plurality of downlink subframes. To transmit ACK/NACKs, one uplink subframe for ACK/NACK is used in response to one of the plurality of downlink subframes. In addition, ACK/NACK responses can be bundled into one uplink subframe for at least two of the plurality of downlink subframes. In an embodiment, multiple ACK/NACK responses can be used in one uplink subframe that corresponds to at least two of the plurality of downlink subframes in a multiple feedback configuration. One uplink subframe for ACK/NACK responses and bundling multiple ACK/NACK responses is for a bundled feedback configuration.