LTE Burst Transmission for Unlicensed Spectrum Efficiency
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Solution Overview
Problem
The existing LTE waveform structure is inefficient in unlicensed frequency bands, particularly at low-to-medium traffic loads, leading to poor resource utilization and sub-optimal performance due to its fixed 1 ms subframe duration, which can prevent devices from accessing the medium and result in inefficiencies compared to more agile technologies like Wi-Fi.
Innovation Solution
Modifying the LTE frame structure to allow for burst transmissions that occupy only a fraction of a subframe, minimizing time usage and maximizing spectral efficiency by adjusting subcarrier spacing and signaling burst duration, enabling efficient coexistence with Wi-Fi in unlicensed spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LTE uses fixed 1 ms subframe structure for transmission, then transmission reliability is ensured, but spectral efficiency deteriorates in unlicensed bands at low-to-medium traffic loads
Solution Approach 1:
The patent segments the fixed 1 ms subframe into variable-length transmission bursts. Instead of transmitting full subframes, the system divides transmissions into shorter bursts that can be dynamically adjusted in length (e.g., 2, 4, 7, 10 symbols) based on traffic load, thereby improving spectral efficiency while maintaining reliable transmission through controlled segmentation
Solution Approach 2:
The patent introduces dynamic adjustment of transmission parameters including subcarrier spacing (15 kHz or 30 kHz) and burst duration based on traffic conditions. The system dynamically selects between different subframe configurations (full subframe, partial subframe, or burst) to adapt to varying traffic loads, transforming the static LTE structure into a dynamic one that optimizes spectral efficiency
2Reliability
If LTE transmits full 1 ms subframes, then complete data communication is ensured, but medium access efficiency deteriorates compared to agile technologies like Wi-Fi
Solution Approach 1:
The patent applies partial action by transmitting only the necessary portion of data in each burst rather than always transmitting full subframes. The system determines the minimum required transmission duration based on traffic load and transmits accordingly (e.g., 2-7 symbols for low load, full 10 symbols for high load), avoiding excessive medium occupation while ensuring complete data communication through multiple bursts if needed
Solution Approach 2:
The patent implements periodic transmission bursts separated by idle periods or listening intervals. Instead of continuous 1 ms subframe transmissions, the system uses periodic bursts with configurable durations and intervals, allowing other technologies like Wi-Fi to access the medium during idle periods, thereby improving overall medium access efficiency while maintaining data communication completeness
3Use of energy by moving object
If LTE uses frequency sparse transmissions at low traffic loads, then energy consumption is reduced, but resource utilization deteriorates in unlicensed spectrum
Solution Approach 1:
The patent changes key transmission parameters including subcarrier spacing (between 15 kHz and 30 kHz) and cyclic prefix length based on traffic load and channel conditions. At low traffic loads, the system uses wider subcarrier spacing with shorter bursts to reduce energy consumption while maintaining adequate resource utilization. At higher loads, it transitions to narrower spacing with full subframes to maximize resource utilization, thereby dynamically optimizing both energy efficiency and spectral efficiency
Data Source
AI summary
Modifications to frame/subframe structure are presented herein so that a wireless device can transmit its data within a fraction of a subframe. The device obtains data to be transmitted in an unlicensed spectrum and determines whether an entire subframe is required to completely communicate the data. If the data is small enough to not require the entire subframe, then the device generates a burst transmission to minimize the time period of the subframe used to communicate the data. The device transmits the burst transmission and a parameter indicating the duration of the burst transmission.