Soft Buffer Size Determination for 4-Layer Spatial Multiplexing
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Solution Overview
Problem
In LTE mobile communication systems, user apparatuses configured with transmission modes TM3 or TM4 face limitations in determining soft buffer size and RI bit width, leading to potential quality deterioration and inability to perform 4-layer spatial multiplexing, especially for UE categories 6 and above.
Innovation Solution
A user apparatus is configured to transmit category information to a base station, receiving parameters for downlink spatial multiplexing, and determining a soft buffer size using the total number of soft channel bits corresponding to the UE category, and determining RI bit width based on the number of MIMO layers supported, enabling proper soft buffer size and RI bit width determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the user apparatus uses the conventional determination method for soft buffer size when configured with TM3 or TM4, then the determination is based on Rel-8 UE category specifications, but the soft buffer size is insufficient for UE categories 6 and above, leading to quality deterioration
Solution Approach 1:
The patent changes the parameter used for soft buffer size determination from Rel-8 UE category to Rel-10 UE category when the apparatus is configured with TM3 or TM4. This parameter change allows UE categories 6 and above to access their appropriate soft buffer sizes, resolving the insufficiency issue while maintaining backward compatibility with older specifications.
2Adaptability or versatility
If the user apparatus reports UE category 6 or above using Rel-10 parameters, then the apparatus supports 4-layer spatial multiplexing capability, but the conventional method incorrectly applies Rel-8 category limitations when TM3 or TM4 is configured
Solution Approach 1:
The patent introduces dynamic selection logic that adapts the soft buffer determination method based on the configured transmission mode. When TM3 or TM4 is configured, the system dynamically switches to use Rel-10 UE category for buffer size determination, allowing the apparatus to flexibly adapt its buffer management to match its actual spatial multiplexing capabilities.
3Measurement precision
If the conventional specification is used for determining RI bit width, then the bit width is limited by Rel-8 category definitions, but the apparatus cannot properly support 4-layer spatial multiplexing for UE categories 6 and above
Solution Approach 1:
The patent changes the basis for RI bit width determination from Rel-8 UE category specifications to Rel-10 UE category specifications when TM3 or TM4 is configured. This allows the RI bit width to properly reflect the 4-layer spatial multiplexing capability of UE categories 6 and above, enabling accurate rank indication feedback.
Data Source
AI summary
A user apparatus configured to perform communication with a base station in a mobile communication system that supports downlink spatial multiplexing such that the user apparatus includes a transmitter that transmits category information of the user apparatus to the base station and a receiver that receives configuration information from the base station. If the category information is a value equal to or greater than a predetermined value and if a parameter indicating a transmission mode corresponding to the downlink spatial multiplexing and predetermined additional information are received as the configuration information, a processor determines a soft buffer size used for downlink data reception processing in the user apparatus by using the total number of soft channel bits corresponding to the category information.