TDD-FDC Cross-Carrier Scheduling DCI Adaptation

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Solution Overview

Problem

In the LTE TDD-FDD joint system, conflicts arise between the payload size of TDD uplink-scheduling DCI and FDD downlink-scheduling DCI, leading to redundancy issues when FDD carriers are used as Primary Carrier Components (PCC) and TDD carriers are used as Secondary Carrier Components (SCC), necessitating a special timing design for cross-carrier scheduling.

Innovation Solution

The proposed solution involves a transmission method where the FDD carrier's uplink-scheduling DCI is received on a subframe n, and uplink data is transmitted on a TDD carrier in subframe n+k, with the uplink scheduling delay aligned to the TDD uplink reference frame configuration. This method ensures that downlink scheduling complies with FDD timing and uplink scheduling complies with TDD timing, eliminating the need for DAI bits and reducing DCI redundancy by adding padding bits as necessary to match bit numbers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If FDD carrier is used as PCC and TDD carrier is used as SCC for cross-carrier scheduling, then scheduling flexibility and peak rate are improved, but DCI payload size conflict and redundancy occur

Engineering Contradiction:

Improvescheduling flexibilityVSAvoidDCI redundancy

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by making the DCI format adaptive to the scheduled carrier type: when scheduling TDD carrier, TDD-specific fields (UL index, DAI) are included; when scheduling FDD carrier, these fields are omitted. This localized adaptation eliminates unnecessary redundancy while maintaining compatibility with both TDD and FDD scheduling requirements.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The DCI format dynamically adjusts its structure based on the scheduled carrier's duplex mode. The patent introduces a dynamic field selection mechanism where the presence of TDD-specific fields (ul-index, dAI) is determined by the carrier type being scheduled, allowing the DCI payload to adapt its composition rather than always including all possible fields.

Inventive Principle:

Principle #15Dynamics

2Measurement precision

If TDD-specific fields are always included in DCI for cross-carrier scheduling, then TDD scheduling accuracy is improved, but DCI overhead increases

Engineering Contradiction:

Improvescheduling accuracyVSAvoidDCI overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies partial action by including only the necessary TDD-specific fields when scheduling TDD carriers, rather than always including all possible fields. The DCI format includes exactly what is needed for the scheduled carrier type, avoiding excessive overhead while maintaining full functionality for TDD scheduling.

Inventive Principle:

Principle #16Partial or excessive action

3Adaptability or versatility

If different timing schemes are used for FDD and TDD carriers, then system compatibility is improved, but cross-carrier scheduling complexity increases

Engineering Contradiction:

Improvesystem compatibilityVSAvoidscheduling complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies segmentation by separating the timing handling into distinct domains: FDD timing relationships are applied to FDD carriers, while TDD timing relationships are applied to TDD carriers. The network device independently configures timing parameters for each carrier type, allowing each to operate according to its own timing rules without interfering with the other, thus managing complexity through structured separation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies universality by creating a unified cross-carrier scheduling framework that can handle both FDD and TDD carriers simultaneously. The same PDCCH on FDD carrier can schedule both FDD and TDD PDSCH/PUSCH, with the timing determination automatically adapting to the scheduled carrier type through configured timing relationships.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP3537814B1Transmission methods and apparatuses in a TDD-FDD joint system

Publication Date: 2021.08.04 SISVEL INT

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Figure 3~4

AI summary

The present invention provides a transmission method and apparatus in a TDD-FDD joint system. In an embodiment of cross-carrier scheduling, an HARQ time sequence of a PUSCH on a scheduled CC complies with a time sequence of a TDD system, and an HARQ time sequence of a PDSCH on the scheduled CC complies with a time sequence of an FDD system; if an uplink reference frame structure on the scheduled CC is #0, uplink-scheduling DCI of the scheduled CC comprises ULI/DAI bits; and if the uplink reference frame structure on the scheduled CC is one of #1 to #6, the uplink-scheduling DCI of the scheduled CC does not comprise the ULI/DAI bits. By using the technical solutions provided in the present invention, redundant overheads of the DCI are reduced, the coverage of the DCI is enlarged, and meanwhile, the compatibility with an existing system is kept to the greatest degree in the present invention.