V2X Terminal MCS Mapping for 64 QAM Decodability
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Solution Overview
Problem
The existing V2X communication standards in LTE Release 14 face inefficiencies due to high coding rates that are not decodable, particularly for modulation orders and Transport Block Sizes (TBS) indices between 19 and 28, which hinders direct communication between Release 14 and Release 15 V2X terminals.
Innovation Solution
The introduction of two mappings between Modulation and Coding Scheme (MCS) indices and modulation orders/TBSs allows for selective application of these mappings, enabling higher modulation orders like 64 QAM while ensuring decodability by scaling down TBSs in non-overlapping portions and maintaining backward compatibility through an indicator for mapping selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Release 14 mapping is reused for 64 QAM, then backward compatibility is maintained, but coding rates become too high to be decodable
Solution Approach 1:
The patent segments the MCS index range into two portions: a first portion (MCS indices 0-20) that uses the Release 14 mapping for backward compatibility, and a second portion (MCS indices 21-28) that uses a new mapping for 64 QAM with decodable coding rates. This segmentation allows the system to maintain compatibility with legacy terminals while enabling efficient 64 QAM communication with newer terminals.
Solution Approach 2:
The patent introduces dynamic mapping selection based on the capability of the communicating terminals. The eNodeB selects which mapping to use (first or second) based on terminal capabilities indicated in capability information, allowing the system to adapt between Release 14 and Release 15 V2X communication modes as needed.
2Productivity
If higher modulation orders like 64 QAM are introduced, then spectral efficiency is improved, but compatibility with legacy terminals is reduced
Solution Approach 1:
The patent segments the MCS index range into two portions: a first portion (MCS indices 0-20) that uses the Release 14 mapping for backward compatibility, and a second portion (MCS indices 21-28) that uses a new mapping for 64 QAM with decodable coding rates. This segmentation allows the system to maintain compatibility with legacy terminals while enabling efficient 64 QAM communication with newer terminals.
Solution Approach 2:
The patent changes the mapping parameters between MCS indices and modulation orders/TBS for the second portion of MCS indices (21-28) to support 64 QAM. This parameter change enables higher spectral efficiency while the coexistence mechanism ensures compatibility with legacy terminals that only understand the first mapping portion.
3Productivity
If MCS indices 19-28 are used with Release 14 mapping, then higher data rates are attempted, but coding rates exceed the decodability threshold
Solution Approach 1:
The patent changes the mapping parameters between MCS indices and modulation orders/TBS for the second portion of MCS indices (21-28) to support 64 QAM. This parameter change enables higher spectral efficiency while the coexistence mechanism ensures compatibility with legacy terminals that only understand the first mapping portion.
Data Source
AI summary
A method in a first terminal device for facilitating direct communication with a second terminal device. The method comprises transmitting to the second terminal device a Modulation and Coding Scheme (MCS) index, based on which the second terminal device can obtain a modulation order and a Transport Block Size (TBS) in accordance with a first mapping or a second mapping between MCS indices on one hand and modulation orders and TBSs on the other. The MCS index is determined by the first terminal device by selectively applying the first or second mapping.