User Terminal TBS Index Modification for LTE Decoding
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Solution Overview
Problem
In existing LTE systems, the determination of Transport Block Size (TBS) for the downlink shared channel based on adaptively controlled modulation schemes can result in code rates exceeding one, leading to challenges in appropriate reception and decoding by user terminals, especially under specific transmission schemes like 4×4 MIMO and transmission mode 9.
Innovation Solution
A user terminal and radio base station system that modifies the TBS index value associated with a predetermined transmission scheme and MCS index value to obtain a smaller TBS, ensuring the code rate remains less than one, by using a TBS table or correction table that defines alternative TBS values for specific conditions, such as transmission mode 9 and 4×4 MIMO.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the TBS is determined based on adaptively controlled modulation schemes using existing LTE methods, then higher data rates and spectrum efficiency are achieved, but the code rate may exceed one leading to decoding errors
Solution Approach 1:
The patent modifies the TBS determination process by introducing a correction step that adjusts the calculated TBS when the code rate would exceed one. This parameter change ensures that the TBS is reduced to maintain a valid code rate, thereby preventing decoding errors while still achieving high data rates through adaptive modulation and coding.
Solution Approach 2:
The patent applies preliminary anti-action by calculating the code rate before finalizing the TBS determination. When the calculated code rate exceeds one, the system proactively adjusts the TBS downward to prevent the invalid condition, rather than dealing with decoding errors after they occur. This preliminary correction maintains reliability while preserving spectral efficiency.
2Reliability
If the TBS index value is modified to reduce TBS for specific transmission schemes, then code rate remains less than one preventing decoding errors, but the data rate is reduced
Solution Approach 1:
The patent applies local quality by modifying the TBS determination only for specific transmission schemes (e.g., transmission mode 9 and 4x4 MIMO) where the code rate would otherwise exceed one. For other transmission schemes, the standard TBS determination method is used, preserving high data rates. This localized correction maintains reliability only where needed while minimizing impact on overall productivity.
Solution Approach 2:
The patent uses partial action by applying the TBS modification only under specific conditions (certain transmission schemes and MCS index values) rather than universally. This selective approach ensures that the code rate remains valid only when necessary, while allowing maximum data rates to be achieved in other scenarios, thus balancing reliability and productivity.
3Reliability
If the TBS is reduced to maintain code rate less than one, then decoding errors are prevented, but spectrum efficiency is reduced
Solution Approach 1:
The patent modifies the TBS parameter dynamically based on the transmission scheme and channel conditions. By changing the TBS only when necessary (when code rate would exceed one), the system maintains decoding accuracy while minimizing the impact on spectrum efficiency. The modification is applied selectively rather than continuously, preserving energy efficiency in normal operating conditions.
Solution Approach 2:
The patent applies the TBS reduction partially, only in specific scenarios where transmission mode 9 or 4x4 MIMO is used with certain MCS index values. In all other cases, the full TBS is utilized, maintaining optimal spectrum efficiency. This partial application minimizes the loss of spectrum efficiency while still preventing decoding errors in the problematic scenarios.
Data Source
AI summary
A user terminal includes a receiver that receives a downlink shared channel and a processor that obtains a transport block size (TBS) used for the downlink shared channel based on: a TBS index value that is associated with a modulation and coding scheme (MCS) index value used for the downlink shared channel; and a number of resource blocks (RBs) that are allocated to the downlink shared channel. When the downlink shared channel is transmitted by a predetermined transmission scheme and the MCS index value is a predetermined value, the processor modifies the TBS index value associated with the predetermined value and obtains the TBS based on the modified TBS index value and the number of RBs.