TFC Selection for LTE Retransmission Adaptation

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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 structures and resource allocation, leading to suboptimal retransmissions in fading channels.

Innovation Solution

A method and apparatus for selecting a TFC that includes a TFC recovery and elimination unit to generate an allowed TFCS subset, a multiplexing and transmission sequence number setting unit to generate LTE MAC PDUs, and a TFC selection and padding unit to select and pad the TFC for initial and retransmission scenarios, adapting to new radio resources and channel conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the same TFC selection is used for retransmission as for initial transmission, then the system maintains consistency in resource allocation, but it cannot efficiently overcome fading channel effects and reduces retransmission success rate

Engineering Contradiction:

Improveretransmission success rateVSAvoidadaptability to channel conditions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic TFC selection where the transport format combination for retransmission is determined based on current channel conditions rather than being fixed. The system adapts the TFC by selecting different modulation and coding schemes according to the measured channel quality, allowing the retransmission parameters to dynamically adjust to overcome fading effects and improve reliability

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes key parameters of the TFC including modulation scheme and coding rate based on channel conditions. By modifying these parameters for retransmission compared to initial transmission, the system can adapt to varying channel quality and improve the probability of successful retransmission without being constrained by fixed parameter allocations

Inventive Principle:

Principle #35Parameter changes

2Productivity

If new TFC selection procedures are implemented to adapt to new radio resources and parameters, then retransmission efficiency improves, but the complexity of the selection process increases

Engineering Contradiction:

Improveretransmission efficiencyVSAvoidTFC selection process complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The system performs preliminary determination of the allowed TFCS subset by pre-identifying which transport format combinations are supported based on allocated radio resources and parameters before actual transmission. This preliminary action simplifies the subsequent TFC selection process by reducing the search space to only valid options, thereby improving efficiency without proportionally increasing complexity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The TFC selection process is segmented into distinct functional units: an allowed TFCS subset generating unit that identifies valid formats, a TFC selection unit that chooses from the allowed subset, and a padding unit that adjusts the data. This segmentation allows each unit to perform its specific function with optimized complexity, improving overall retransmission efficiency while managing system complexity through modular design

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If the number of subcarrier blocks and TTIs are considered as new radio resources for TFC selection, then resource allocation accuracy improves, but the complexity of resource management increases

Engineering Contradiction:

Improveresource allocation accuracyVSAvoidresource management complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The allowed TFCS subset generating unit serves multiple functions: it validates TFCs against resource constraints, determines supported modulation and coding schemes, and prepares the selection space for both initial transmission and retransmission. This multi-functionality reduces the need for separate complex management mechanisms for different resource types, achieving accurate resource allocation while managing complexity through unified processing

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP1961172B1Method and apparatus for selecting a transport format combination

Publication Date: 2010.10.27 INTERDIGITAL TECH CORP

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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.