Fallback DCI Sub-band Indication for Shared Spectrum
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Solution Overview
Problem
In wireless communications, existing fallback downlink control information (DCI) formats do not provide explicit sub-band indication for uplink transmissions in shared radio frequency spectrum bands, leading to ambiguity when sub-bands change, particularly in contention-based access scenarios, which can result in inefficient use of bandwidth and communication disruptions.
Innovation Solution
The implementation of fallback DCI formats that include a sub-band indication field to explicitly or implicitly indicate the sub-bands for uplink communications, maintaining a predetermined number of bits while providing sub-band information, allowing users to determine the correct sub-bands for transmission and ensuring consistent interpretation across different radio resource control configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fallback DCI formats are used without sub-band indication, then the DCI structure remains simple and backward compatible, but sub-band determination becomes ambiguous when sub-bands change in shared spectrum
Solution Approach 1:
The patent segments the DCI format into different types (first fallback DCI format with sub-band indication, second fallback DCI format without sub-band indication). This allows the system to selectively use the appropriate format based on whether sub-band indication is needed, resolving the contradiction between providing sub-band information and maintaining DCI simplicity.
Solution Approach 2:
The patent introduces dynamic adaptability by allowing the UE to determine the appropriate DCI format based on configured parameters. The system can dynamically switch between DCI formats with and without sub-band indication fields, enabling flexible adaptation to changing spectrum conditions while maintaining backward compatibility.
2Loss of information
If sub-band indication field is added to fallback DCI, then sub-band information is explicitly provided for uplink transmissions, but the DCI bit length increases from predetermined fixed length
Solution Approach 1:
The patent segments DCI formats into different versions based on whether they include sub-band indication fields. The first fallback DCI format includes sub-band indication for complete information, while the second fallback DCI format maintains the original fixed bit length for scenarios where sub-band information is not needed, thus resolving the contradiction between information completeness and fixed length requirement.
Solution Approach 2:
The patent changes the parameter of DCI bit length flexibility by introducing variable-length DCI formats. This allows the system to adjust the DCI bit length based on whether sub-band indication is required, enabling complete sub-band information transmission when needed while maintaining fixed length for scenarios where it is not necessary.
3Adaptability or versatility
If multiple DCI formats with different bit lengths are used, then sub-band information can be flexibly indicated, but processing complexity at the UE increases
Solution Approach 1:
The patent introduces dynamic adaptability by allowing the UE to determine the appropriate DCI format based on configured parameters. The system can dynamically switch between DCI formats with and without sub-band indication fields, enabling flexible adaptation to changing spectrum conditions while maintaining manageable processing complexity through parameter-based selection.
Solution Approach 2:
The patent applies preliminary action by pre-configuring the UE with information about which DCI formats to expect and how to interpret them. The UE is provided with configuration information that indicates whether sub-band indication is included, allowing the UE to process the appropriate format without increasing complexity through advance preparation.
4Reliability
If sub-band indication is provided in all fallback DCI, then unambiguous sub-band determination is achieved, but bandwidth efficiency decreases due to padding bits
Solution Approach 1:
The patent segments DCI formats into different versions based on whether they include sub-band indication fields. The first fallback DCI format includes sub-band indication for complete information, while the second fallback DCI format maintains the original fixed bit length for scenarios where sub-band information is not needed, thus resolving the contradiction between providing sub-band information and maintaining simplicity.
Solution Approach 2:
The patent applies partial action by providing sub-band indication only when necessary (in the first fallback DCI format) rather than in all DCI formats. This allows the system to achieve reliable sub-band determination when needed while avoiding unnecessary padding bits and maintaining bandwidth efficiency in scenarios where sub-band information is already known or not required.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described where a system bandwidth within a shared radio frequency spectrum band may be divided into multiple sub-bands. A base station may use a fallback downlink control information format to provide a resource grant to a user equipment, where the fallback downlink control information has a predetermined number of bits. To provide an indication of one or more of the sub-bands that are to be used for uplink communications when using fallback downlink control information, an explicit or implicit indication may be provided. Such sub-band indication may allow for the user equipment to use a particular sub-band that is available for transmissions in a shared radio frequency spectrum band. Indications of one or more sub-bands may be provided explicitly by a sub-band indication field in a fallback downlink control information, or implicitly by one or more downlink transmissions of a base station.