MAC CE HARQ Control for High-Latency Satellite Links
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Solution Overview
Problem
The existing HARQ technology in LTE and NR systems is inefficient for satellite communication scenarios due to the limited number of HARQ processes supported by the 3GPP protocol, leading to unnecessary delays and ineffective retransmissions, and lacks flexibility in enabling or disabling the HARQ function based on service type or channel quality.
Innovation Solution
A communication method and apparatus that utilize MAC control elements (CE) in MAC PDUs to dynamically control the enabling or disabling of HARQ processes, allowing for flexible configuration based on channel quality or service type, using fixed or variable-length MAC CEs with reserved LCIDs to indicate specific HARQ processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the 3GPP protocol's default HARQ process limit (8-16 processes) is used, then device complexity is reduced and ease of operation is maintained, but productivity is severely limited in satellite scenarios requiring 500+ HARQ processes
Solution Approach 1:
The patent implements dynamic HARQ process management by introducing MAC CE signaling that allows the network to dynamically indicate the number of HARQ processes to be used. This enables the system to adapt the HARQ process count based on satellite round-trip delay characteristics and service requirements, transitioning from a static 8-16 process limit to a dynamic configuration that can support 500+ processes when needed for satellite communications.
2Reliability
If the HARQ function is always enabled, then reliability is improved through error correction and retransmission, but loss of time increases due to stop-and-wait delays in high-latency satellite scenarios
Solution Approach 1:
The patent enables dynamic enabling and disabling of the HARQ function through MAC CE signaling. The network can indicate whether HARQ should be enabled or disabled based on current channel conditions, service type, and latency requirements. This allows the system to disable HARQ for time-sensitive services in satellite scenarios where the stop-and-wait mechanism would cause excessive delays, while still providing HARQ protection when reliability is the priority.
Solution Approach 2:
The patent changes the operational state parameter of the HARQ function from a fixed enabled state to a dynamically controllable state. Through MAC CE signaling, the network can adjust the HARQ enable/disable status and the number of HARQ processes based on varying channel quality and service requirements, optimizing the balance between reliability and transmission delay.
3Adaptability or versatility
If HARQ processes are dynamically controlled based on service type and channel quality, then adaptability is improved, but device complexity increases due to additional control signaling requirements
Solution Approach 1:
The patent utilizes existing MAC CE structures and signaling mechanisms to implement HARQ dynamic control, making the solution compatible with current LTE and NR systems. The same MAC CE framework used for other control functions is leveraged to convey HARQ process count and enable/disable indications, avoiding the need for entirely new signaling protocols and reducing the impact on device complexity.
Data Source
AI summary
A media access control element (MAC CE) indicates a terminal device to enable or disable at least one hybrid automatic repeat request (HARQ) process, or the MAC CE requests a network device to enable or disable the at least one HARQ process. This provides a solution for dynamically controlling a HARQ function.