Self-Contained TDD Subframe Structure for Low Latency
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Solution Overview
Problem
Current LTE systems experience longer Hybrid automatic repeat request (HARQ) acknowledgement (HARQ-ACK) transmission latency in Time-Division Duplex (TDD) configurations due to the unavailability of downlink (DL) or uplink (UL) subframes for HARQ-ACK transmission, leading to inefficiencies in spectrum usage and traffic adaptation.
Innovation Solution
The introduction of a self-contained time division duplex (TDD) subframe structure within 5G architecture, where an extended physical downlink shared channel (xPDSCH) and physical uplink shared channel (xPUSCH) are used, along with an extended physical downlink control channel (xPDCCH) and guard time, to facilitate simultaneous DL and UL data transmission, enabling subframe-level traffic adaptation and reducing latency through the insertion of spacing signals for additional processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional TDD subframe structure is used, then system compatibility with existing LTE standards is maintained, but HARQ-ACK transmission latency increases
Solution Approach 1:
The subframe is segmented into distinct DL and UL portions with a guard period inserted between them. This segmentation allows the DL subframe to be self-contained with its own HARQ-ACK feedback mechanism, reducing latency by enabling faster acknowledgment transmission without waiting for the next available UL subframe.
Solution Approach 2:
The patent introduces dynamic traffic adaptation at the subframe level, allowing the system to flexibly adjust between DL and UL traffic patterns. The self-contained structure enables independent configuration of DL and UL resources, providing dynamic adaptability to varying traffic conditions while maintaining low latency through the inserted guard period.
2Loss of time
If guard time is inserted for processing, then additional processing time is provided, but subframe duration increases
Solution Approach 1:
The guard period is inserted preliminarily within the DL subframe structure, before the UL transmission begins. This preliminary insertion of processing time allows the system to perform necessary signal processing and HARQ-ACK preparation without extending the overall subframe duration beyond the standardized timeline, as the guard period is efficiently utilized for multiple purposes.
Solution Approach 2:
The guard period serves multiple functions simultaneously: it provides processing time for HARQ-ACK generation, acts as a transition period between DL and UL transmissions, and enables frequency switching. This multi-functionality allows the system to gain processing time without proportionally increasing the subframe duration.
3Loss of time
If self-contained subframe structure is implemented, then HARQ-ACK latency is reduced, but system complexity increases
Solution Approach 1:
The self-contained structure is implemented locally within individual DL subframes, allowing each subframe to be independently configured and processed. This local implementation reduces the need for complex system-wide coordination and timing adjustments, as each subframe operates autonomously with its own guard period and HARQ-ACK feedback mechanism.
Solution Approach 2:
The patent applies periodic insertion of guard periods at regular intervals within the TDD frame structure. This periodic approach creates a predictable pattern that simplifies scheduling and resource allocation algorithms, reducing system complexity while maintaining the latency benefits of self-contained subframes throughout the transmission sequence.
Data Source
AI summary
Technology for an eNodeB to communicate with a user equipment (UE) using a self-contained time division duplex (TDD) subframe within a wireless communication network is disclosed. The eNodeB can process, for transmission to the UE, a DL self-contained time division duplex (TDD) subframe comprising an extended physical downlink shared channel (xPDSCH), an extended physical downlink control channel (xPDCCH), a downlink (DL) spacing signal, and a guard period, wherein the xPDSCH, the xPDCCH, the DL spacing signal, and the guard time are located within the DL self-contained TDD subframe prior to an extended physical uplink control channel (xPUCCH). The eNodeB can process, an uplink (UL) self-contained TDD subframe, received from the UE, having a UL spacing signal located after an extended physical uplink shared channel (xPUSCH).