Dynamic TFC Selection for Wireless Retransmission Efficiency
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Solution Overview
Problem
Current wireless communication standards, particularly in LTE and HSPA+, face inefficiencies in transport format combination (TFC) selection due to changes in physical layer structure and resource allocation, leading to suboptimal retransmissions in fading channels.
Innovation Solution
A method and apparatus for selecting a TFC that generates an allowed transport format combination set by recovering supported TFCs, eliminating unsupported ones, and dynamically adjusting modulation and coding schemes for retransmissions based on new radio resources and channel conditions, incorporating a TFC recovery and elimination unit, multiplexing and transmission sequence number setting unit, and TFC selection and padding unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same TFC selection is used for retransmission as for initial transmission, then implementation complexity is reduced, but transmission reliability deteriorates in fading channels
Solution Approach 1:
The patent implements dynamic TFC selection where the system adapts the transport format combination based on current channel conditions. The TFC selection is no longer static but dynamically adjusted according to fading channel characteristics, allowing the system to optimize transmission parameters in real-time while managing complexity through structured selection procedures.
Solution Approach 2:
The patent changes key transmission parameters including MCS (modulation and coding scheme), transport block size, and TFC configuration between initial transmission and retransmission. By modifying these parameters based on channel feedback and conditions, the system improves reliability without requiring complete redesign of the TFC selection mechanism.
2Adaptability or versatility
If new radio resources and parameters are allocated for retransmission, then transmission adaptability is improved, but resource allocation complexity increases
Solution Approach 1:
The patent segments the resource allocation process into distinct components: TFC selection, MCS determination, and radio resource allocation. Each component can be independently optimized and managed, reducing overall complexity while maintaining adaptability. The TFC selection unit operates separately from the resource allocation mechanism, allowing modular design.
Solution Approach 2:
The system performs preliminary TFC selection and parameter determination before actual transmission and retransmission. By pre-configuring allowed TFC subsets and establishing selection criteria in advance, the system reduces real-time complexity during retransmission while maintaining adaptability to channel conditions.
3Device complexity
If TFC selection does not adapt to channel conditions, then implementation simplicity is maintained, but retransmission efficiency deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where channel conditions are monitored and used to inform TFC selection decisions. The system receives feedback about channel quality and adjusts the selected TFC accordingly, improving retransmission efficiency by avoiding inappropriate format selections while maintaining manageable complexity through structured feedback processing.
Solution Approach 2:
The system dynamically changes TFC parameters including modulation order, coding rate, and transport block size based on observed channel conditions. This adaptive parameter adjustment improves retransmission efficiency by matching transmission parameters to actual channel capabilities without requiring complex real-time optimization algorithms.
Data Source
AI summary
A method and apparatus for selecting a transport format combination (TFC) are disclosed. A TFC recovery and elimination unit generates an allowed transport format combination set (TFCS) subset by recovering supported TFCs and eliminating not supported TFCs based on allocated radio resources and parameters that are new. A multiplexing and transmission sequence number (TSN) setting unit generates a medium access control (MAC) protocol data unit (PDU) by multiplexing at least one higher layer PDU within a maximum supported MAC PDU size. A TFC selection and padding unit selects a TFC for the MAC PDU from the allowed TFCS subset and performs padding of the MAC PDU, if necessary, so that the MAC PDU fits into the selected TFC. For retransmission, a new allowed TFCS subset may be generated based on new radio resources and parameters and the MAC PDU may be fragmented.