LTE Subframe Microframe Structure for Low Latency
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Solution Overview
Problem
Current LTE subframe structures are inadequate for achieving low latency and high throughput required for 5G systems, especially when operating at higher frequencies and wider bandwidths, due to legacy design shortcomings and increased latency.
Innovation Solution
A new subframe structure is introduced, dividing each subframe into microframes, allowing for dynamic uplink-downlink configurations, explicit signaling of ACK/NAK, and optimized HARQ timing to reduce latency and overhead, enabling low latency and higher throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If legacy LTE subframe structure is used, then system compatibility is maintained, but latency is high and throughput is limited
Solution Approach 1:
The patent divides each 1ms subframe into multiple smaller microframes (e.g., 4 microframes of 0.25ms each), enabling finer-grained time resource allocation. This segmentation allows data transmission and acknowledgment to occur in shorter time intervals, reducing overall latency while maintaining compatibility with existing LTE subframe structures through the introduction of a new parameter 'k' that indicates the number of microframes per subframe.
2Adaptability or versatility
If dynamic uplink-downlink configuration is implemented, then adaptability to traffic patterns improves, but system complexity increases
Solution Approach 1:
The patent enables dynamic uplink-downlink configuration by allowing the number of downlink microframes (k) to vary across different subframes. The value of k can be signaled through RRC configuration or dynamic indication in DCI, allowing the system to adapt to changing traffic patterns. For example, k can be set to 4 for downlink-heavy traffic or 0 for uplink-heavy traffic, providing flexible adaptation without complex reconfiguration procedures.
3Productivity
If ACK/NAK timing is optimized for low latency, then throughput improves, but timing rule complexity increases
Solution Approach 1:
The patent introduces a new parameter 'k' representing the number of microframes per subframe, which fundamentally changes the timing relationship between data transmission and acknowledgment. Instead of fixed subframe-based timing, the acknowledgment timing is now determined by the microframe structure. For example, if k=4 and data is transmitted in the first downlink microframe, the acknowledgment can be sent in the first uplink microframe of the same subframe, achieving low latency with a systematic parameter-based approach rather than complex case-by-case timing rules.
4Productivity
If microframe-level resource allocation is implemented, then resource utilization efficiency improves, but control signaling overhead increases
Solution Approach 1:
The patent makes the existing LTE physical downlink control channel (PDCCH) and physical uplink control channel (PUCCH) multi-functional by enabling them to operate at both subframe and microframe levels. The same PDCCH structure can schedule multiple microframes within a subframe, and PUCCH can carry acknowledgments for specific microframes. This universal approach allows fine-grained resource allocation without requiring entirely new control channel structures, thereby limiting the increase in signaling overhead.
Data Source
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AI summary
System and method embodiments are provided for a subframe structure for wideband LTE. In an embodiment, a method in a communications controller for transmitting a packet to a wireless device includes signaling a UL/DL configuration to the wireless device, wherein the UL/DL configuration indicates a quantity of uplink microframes in a group of microframes, wherein each subframe includes a plurality of microframes, and wherein the group of microframes includes a consecutive sequence downlink microframes and a consecutive sequence of uplink microframes. The packet is transmitted to the wireless device in one downlink microframe. The method further includes receiving an acknowledgement of the packet in an uplink microframe, wherein the uplink microframe is determined in accordance with the one downlink microframe and the uplink-downlink configuration, and wherein the acknowledgement is received in a same subframe as a subframe utilized for transmitting the packet to the wireless device.