TDD Transmission Frame Symbol Segmentation for Low Latency
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Solution Overview
Problem
Time Division Duplex (TDD) communication systems face significant round trip delays due to the inability to simultaneously transmit and receive, affecting error control mechanisms like ACK/NACK messages, which is problematic for low-latency services, especially in frequency bands below 6GHz and under regulatory restrictions on uplink-downlink configurations.
Innovation Solution
The method involves splitting each radio frame or sub-frame into transmission symbols, allowing a fraction of the bandwidth for reverse-direction communication within the same time frame, with guard bands to prevent interference, enabling fast ACK/NACK transmission and simultaneous uplink and downlink operations using Orthogonal Frequency Division Multiplexing (OFDM) and appropriate Resource Block allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If TDD operation is used to operate on unpaired spectrum, then spectrum efficiency is improved, but round trip delay increases significantly
Solution Approach 1:
The patent segments the transmission time frame into multiple transmission symbols, allowing the system to switch direction multiple times within a single frame. This segmentation enables more frequent uplink-downlink switching, reducing the round trip delay while maintaining TDD spectrum efficiency.
Solution Approach 2:
The patent introduces dynamic switching between uplink and downlink directions at the transmission symbol level, rather than fixed sub-frame level switching. This dynamic approach allows the system to adaptively reduce latency by increasing switching frequency when low-latency services are detected, while maintaining overall spectrum efficiency.
2Stability of the object's composition
If fixed uplink-downlink configuration is used to ensure regulatory compliance, then system stability is improved, but latency reduction capability deteriorates
Solution Approach 1:
The patent enables dynamic adjustment of uplink-downlink configuration at the transmission symbol level while maintaining compliance with regulatory minimum/maximum ratios. The system can dynamically switch directions within the constraints of fixed regulatory configurations, reducing latency without violating stability requirements.
Solution Approach 2:
The patent prepares multiple pre-configured transmission symbol patterns that comply with regulatory requirements in advance. When low-latency services are needed, the system can quickly switch between these pre-prepared patterns without violating regulatory constraints, reducing the time needed for configuration changes.
3Device complexity
If transmission time frame is split into sub-frames with fixed switching points, then system complexity is reduced, but switching flexibility deteriorates
Solution Approach 1:
The patent segments the transmission frame into transmission symbols with finer granularity than traditional sub-frames. This segmentation provides more switching opportunities without significantly increasing system complexity, as the underlying frame structure remains similar but with additional switching points.
Solution Approach 2:
The patent maintains periodic transmission symbol structures for regular traffic while introducing flexible switching points for low-latency services. This periodic approach keeps system complexity manageable while providing versatility when needed through selective activation of flexible switching points.
4Reliability
If guard bands are added to prevent interference between opposite direction transmissions, then transmission reliability is improved, but spectral efficiency deteriorates
Solution Approach 1:
The patent segments the frequency bandwidth into multiple resource blocks within each transmission symbol. This allows guard bands to be placed only between opposite direction transmissions within the same frame, rather than across the entire spectrum continuously, reducing the total spectral overhead while maintaining interference protection.
Solution Approach 2:
The patent uses periodic guard band placement only when direction switching occurs within a frame, rather than continuous guard bands. This periodic approach maintains reliability by providing interference protection at switching points while improving spectral efficiency by eliminating unnecessary guard bands during same-direction transmissions.
Data Source
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AI summary
A structure of a transmission time frame for Time Division Duplex (TDD) two-way communication over a frequency bandwidth is provided. The transmission time frame is assigned for a first direction of communication and is temporally divided into a plurality of transmission symbols. A fraction of the frequency bandwidth for a selected transmission symbol from the plurality of transmission symbols is assigned to a second direction of communication, the second direction being opposite to the first direction.