HARQ Indicator Channel Design for Coverage and Power Trade-offs
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Solution Overview
Problem
In wireless communication systems, especially in 3GPP and LTE, UEs in challenging environments like basements or buildings with metalized insulation experience significant penetration losses, requiring repeated transmissions with varying repetition numbers to improve power consumption and coverage, but existing mechanisms lack efficient feedback mechanisms for ACK/NACK in such scenarios.
Innovation Solution
A new HARQ mechanism is introduced, using an enhanced PHICH (EPHICH) channel to provide UE-specific, group-specific, or cell-specific HARQ indicators for ACK/NACK feedback, allowing UEs to determine acknowledgement status and adjust repetition numbers for efficient retransmissions based on detected signals and predefined rules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If repeated transmissions are used to bridge penetration losses in challenging environments, then coverage and reliability are improved, but power consumption increases and system resources are depleted faster
Solution Approach 1:
The patent implements dynamic adjustment of repetition numbers based on channel conditions and UE power status. The network can configure different repetition numbers (e.g., first repetition number for initial transmission, second repetition number for retransmission) and the UE adapts its transmission strategy accordingly, allowing flexible optimization between coverage reliability and power consumption rather than using fixed repetition patterns
Solution Approach 2:
The patent introduces enhanced feedback mechanisms including uplink HARQ feedback and downlink HARQ-ACK indicators to provide real-time transmission status information. This feedback enables the network and UE to make informed decisions about whether repeated transmissions are necessary, avoiding unnecessary retransmissions that would consume additional power while maintaining reliability when needed
2Reliability
If more resources and power are allocated to support repeated transmissions, then coverage for UEs in extreme scenarios is improved, but system resource efficiency decreases
Solution Approach 1:
The system dynamically configures repetition numbers and resource allocation based on actual channel conditions and UE requirements. Different UEs can be assigned different repetition numbers (e.g., Aggregation Level 4 for some UEs, Aggregation Level 8 for others) and the network adjusts resource allocation adaptively, preventing wasteful allocation of resources to UEs that don't need repeated transmissions while ensuring adequate resources for UEs in challenging environments
Solution Approach 2:
The patent applies different transmission parameters and resource allocation strategies to different UEs based on their specific channel conditions and coverage requirements. Instead of uniformly allocating resources to all UEs, the system tailors the repetition number and resource block allocation to each UE's local needs, optimizing overall system resource efficiency while maintaining coverage for extreme scenarios
3Loss of information
If single-state HARQ indicators are used instead of traditional two-state indicators, then feedback overhead is reduced, but information completeness for ACK/NACK determination may be compromised
Solution Approach 1:
The patent inverts the traditional HARQ indicator approach by using a single-state indicator where the presence of a detected signal indicates NACK (negative acknowledgment) and the absence indicates ACK (positive acknowledgment). This inversion, combined with the use of UE-specific reference signals and scrambling sequences, allows the system to convey reliable ACK/NACK information with reduced feedback overhead, as the detection of the indicator itself carries the complete information needed for determination
Data Source
AI summary
Apparatus and methods are provided to enhance HARQ mechanism. In one novel aspect, the UE decodes resource blocks in a HARQ indicator channel and detects a single-state HARQ indicator encoded with a UE ID of the UE. The UE determines a HARQ acknowledgment status for the data transmission based on the HARQ indicator. In one embodiment, the HARQ indicator channel is either a UE-specific channel, a group-specific channel or a cell-specific channel. In another novel aspect, the UE increases a HARQ count upon decoding the HARQ indicator channel. The UE retransmits the data transmission if the HARQ count is smaller than a predefined maximum HARQ count and the HARQ acknowledgement status is determined to be negative. Otherwise, the UE stops the data transmission. In another embodiment, the UE terminates the data transmission is the total repetition number is greater than a predefined maximum data transmission number.