LTE Unlicensed Subframe Termination Point Indication
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Solution Overview
Problem
In LTE Licensed-Assisted Access, data transmissions in unlicensed spectrum are restricted to terminate at subframe boundaries, leading to underutilization of transmission time due to the lack of a mechanism to indicate any other termination point, violating regulations and reducing spectral efficiency.
Innovation Solution
A method and apparatus that allow data transmission to terminate part way through a subframe by transmitting downlink control information with a termination point indication, enabling the receiving device to demodulate data correctly, using a symbol index indicator and tables for size derivation, and including a postamble signal for precise termination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If data transmission terminates at subframe boundaries, then transmission timing is simplified and synchronized, but transmission time utilization decreases due to inability to terminate mid-subframe
Solution Approach 1:
The subframe is segmented into multiple possible termination points (e.g., after different numbers of OFDM symbols). The termination point indication field specifies which segment boundary should be used, allowing flexible termination within the subframe rather than only at the end. This segmentation enables the system to maintain simple subframe-based scheduling while achieving finer-grained transmission control.
Solution Approach 2:
The termination point is made dynamic through the termination point indication field, which can take different values to specify different termination positions within the subframe. This dynamic adjustment allows the transmission to adapt to varying channel conditions and regulatory requirements while maintaining the overall subframe structure for synchronization.
2Reliability
If data transmission must terminate at the last subframe boundary before 4 ms, then transmission compliance with maximum length restriction is ensured, but up to 25% of available transmission time remains unused
Solution Approach 1:
By segmenting the subframe into multiple possible termination points and using the termination point indication to select the appropriate segment boundary, the system can terminate transmission precisely at the 4 ms mark or any earlier point, eliminating the wasted time that occurs when termination must wait for the next subframe boundary.
Solution Approach 2:
The termination point parameter is changed from a fixed subframe boundary to a configurable position within the subframe (specified by the termination point indication field). This parameter change allows the system to adjust the termination point to maximize utilization while complying with the maximum transmission length restriction.
3Productivity
If termination point indication is added to downlink control information, then transmission time utilization improves, but downlink control information complexity increases
Solution Approach 1:
The termination point indication is added as a localized field within the downlink control information structure, affecting only the specific aspect of transmission timing without redesigning the entire control information framework. This localized addition minimizes the impact on overall system complexity while achieving the desired functionality.
Solution Approach 2:
The termination point indication field serves multiple functions: it specifies the termination position, enables compliance with maximum transmission length restrictions, and allows adaptation to different channel conditions and regulatory requirements. This multi-functionality justifies the added complexity by providing versatile control capabilities.
Data Source
AI summary
A method is provided for assisting data transmission on a first carrier by indicating a termination point of data transmission in a transmitting device and apparatus thereof, wherein the method comprises the steps of: A. transmitting data on the carrier to a receiving device in a first subframe; and B. transmitting downlink control information to the receiving device; wherein the downlink control information includes a termination point indication for indicating a termination point of the data in the first subframe. The method and apparatus could improve the utilization of subframe and transmission capacity, and enable LTE to satisfy the regulations for unlicensed operation with high spectral efficiency.