256QAM Soft Buffer Scaling for LTE UE Category Compatibility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current LTE systems face challenges in supporting 256 Quadrature Amplitude Modulation (256QAM) without increasing terminal complexity and cost, as existing UE categories are not optimized to handle the higher data rates and increased soft buffer sizes required by 256QAM, especially in scenarios where higher order modulation is sensitive to transmitter EVM and Rx impairments.
Innovation Solution
The solution involves using larger transport block sizes with existing soft buffer sizes, allowing UE devices to support 256QAM by maintaining the same number of soft channel bits for both 256QAM and lower order modulation schemes like 64QAM, thereby enabling cost-efficient implementation and backwards compatibility with existing UE categories.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If 256QAM modulation is implemented in existing UE categories, then data rates and system performance are improved, but terminal complexity and cost increase due to larger soft buffer size requirements
Solution Approach 1:
The patent changes the parameter of soft buffer size allocation by introducing a new parameter Kh (set to 4/3 for 256QAM) that scales the soft buffer size calculation. This allows the system to accommodate 256QAM's higher data rates while maintaining compatibility with existing UE category definitions and avoiding direct hardware buffer increases.
Solution Approach 2:
The patent introduces a new dimension to the soft buffer calculation by adding the Kh factor that depends on modulation order. This creates a layered approach where the base soft buffer size remains compatible with existing categories, while the Kh multiplier provides the additional capacity needed for 256QAM without requiring entirely new buffer architecture.
2Productivity
If 256QAM modulation is implemented, then spectral efficiency is improved, but device cost increases due to hardware requirements
Solution Approach 1:
The patent makes the soft buffer size calculation universal across different modulation schemes by introducing the Kh parameter that adapts to modulation order (1 for 64QAM and lower, 4/3 for 256QAM). This allows existing UE categories to support multiple modulation schemes including 256QAM without requiring separate hardware implementations for each modulation type.
Solution Approach 2:
The patent changes the soft buffer size parameter dynamically based on modulation order through the Kh factor. This allows the same hardware infrastructure to support both lower-order modulations (with Kh=1) and 256QAM (with Kh=4/3), avoiding the need for expensive dedicated 256QAM hardware while maintaining spectral efficiency benefits.
3Adaptability or versatility
If existing UE categories are used without modification, then backwards compatibility is maintained, but 256QAM support is limited due to insufficient soft buffer capacity
Solution Approach 1:
The patent makes the soft buffer size dynamic by introducing the Kh parameter that adjusts based on the configured modulation order. When 256QAM is configured, Kh becomes 4/3, automatically scaling the soft buffer size to accommodate the higher data rates. When lower-order modulations are used, Kh reverts to 1, maintaining original buffer allocations and backwards compatibility.
Solution Approach 2:
The patent creates a universal soft buffer calculation formula that works for both legacy and advanced UE categories. The Kh parameter serves as a compatibility layer that allows the same formula to correctly calculate buffer sizes for 64QAM (Kh=1) and 256QAM (Kh=4/3), enabling existing UE categories to support 256QAM through software/configuration rather than hardware modification.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
According to some embodiments, a method in a wireless network element of transmitting a transport block comprises determining a modulation coding scheme for a transmission of the transport block; determining a category type of a wireless device that will transmit or receive the transport block; determining, using the category type of the wireless device, an encoding soft buffer size (NJR) for the transport block; adjusting, using the modulation coding scheme, the encoding soft buffer size (!½) by a factor (¾); encoding the transport block, according to the determined modulation coding scheme and the adjusted encoding soft buffer size; and transmitting the transport block. In particular embodiments, the determined modulation coding scheme is 256 Quadrature Amplitude Modulation (256QAM) and the factor (¾) is 4/3.