Adaptive Uplink HARQ for MTC Coverage and Complexity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current LTE systems face challenges in efficiently supporting Machine-Type Communications (MTC) due to high costs and limited coverage for Low Complexity/Low Cost User Equipments (LC UEs), which require adaptive and flexible retransmission techniques to manage bursty transmissions and small data packets effectively.
Innovation Solution
The implementation of adaptive uplink retransmissions in LTE systems using a physical downlink control channel for machine-type communications, allowing for varying modulation and coding rates, frequency resources, and repetition levels, as signaled by the network node, enabling flexible retransmission formats and timing adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time repetition techniques are used to achieve coverage enhancement for MTC UEs, then coverage and reliability are improved, but device complexity and power consumption increase due to continuous monitoring and transmission requirements
Solution Approach 1:
The patent implements dynamic HARQ process management where the network node can configure different numbers of HARQ processes based on UE capability and coverage requirements. LC UEs can be configured with fewer HARQ processes (e.g., 1-4 processes) compared to normal UEs, dynamically adapting the system complexity to match the actual needs of low-complexity devices while maintaining coverage enhancement through appropriate repetition schemes.
Solution Approach 2:
The patent changes key parameters including the number of HARQ processes, subframe bundling configurations, and repetition factors based on UE category. By dynamically adjusting these parameters, the system achieves coverage enhancement for MTC UEs while preventing excessive complexity accumulation in LC UEs that would otherwise need to handle the full complement of HARQ processes.
2Ease of manufacture
If reduced UE bandwidth of 1.4 MHz is introduced for low-cost UEs, then device cost is reduced, but system bandwidth utilization and data transmission capacity are limited
Solution Approach 1:
The patent segments the system into different UE categories (LC UEs and normal UEs) with differentiated resource allocation. LC UEs operate on reduced 1.4 MHz bandwidth with simplified processing, while normal UEs utilize the full system bandwidth. This segmentation allows low-cost devices to be manufactured with reduced capabilities while the overall system maintains high productivity through full-bandwidth utilization by other UEs.
Solution Approach 2:
The patent creates a universal HARQ framework that serves multiple UE types simultaneously. The same HARQ infrastructure supports both LC UEs with reduced bandwidth and normal UEs with full bandwidth, allowing the system to accommodate diverse device capabilities without requiring separate systems. This multi-functionality enables cost reduction for LC UEs while preserving overall system productivity.
3Device complexity
If synchronous non-adaptive HARQ is used for uplink retransmissions, then device complexity is reduced, but adaptability to varying channel conditions and optimization of resource usage are limited
Solution Approach 1:
The patent implements dynamic HARQ process management where the network node can configure different numbers of HARQ processes based on UE capability and coverage requirements. LC UEs can be configured with fewer HARQ processes (e.g., 1-4 processes) compared to normal UEs, dynamically adapting the system complexity to match the actual needs of low-complexity devices while maintaining coverage enhancement through appropriate repetition schemes.
Solution Approach 2:
The patent employs periodic subframe bundling where multiple subframes are grouped together for transmission. This periodic structure provides a balance between simplicity and adaptability by creating regular transmission patterns that reduce UE complexity while still allowing the network to optimize resource allocation across the bundled subframes based on channel conditions.
Data Source
AI summary
The solution presented herein introduces variable repetition levels for control and data transmissions via a physical downlink control channel for machine-type communications, e.g., the M-PDDCH. When a wireless terminal detects and correctly decodes a message carried by physical downlink control channel for machine-type communications that requests retransmissions, the wireless terminal performs adaptive uplink retransmissions according to a retransmission format defined by the message. The retransmission format defines at least one of a modulation and coding rate for the retransmissions, a frequency resource for the retransmissions, and a number of repetitions.