Guard Band Uplink Scheduling for LTE-NR Coexistence

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Solution Overview

Problem

The implementation of New Radio (NR) in mid bands using Time Division Duplex (TDD) faces challenges such as reduced uplink coverage and increased latency due to propagation losses and the need for complex scheduling coordination with existing LTE systems, particularly in scenarios where fast coordination and large frequency bands are not feasible.

Innovation Solution

Configuring a radio access system with a first carrier for frequency division duplex signalling, where the second carrier's frequency band overlaps with a third carrier's band, allowing uplink signals to be scheduled in physical resource blocks within the guard bands of the third carrier, thereby enhancing coverage and reducing latency without requiring intricate scheduling coordination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If TDD is used in mid bands for NR, then frequency resources are utilized, but uplink coverage is reduced and latency increases

Engineering Contradiction:

Improvefrequency resourcesVSAvoiduplink coverage

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent segments the frequency band usage by dividing the mid-band carrier into different functional parts: guard bands are allocated for uplink control signalling while the remaining bandwidth is used for data transmission. This segmentation allows independent optimization of coverage and capacity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from time-division duplexing (TDD) to frequency-division duplexing (FDD) by utilizing guard bands in the frequency domain for uplink control signalling. This dimensional change from time to frequency enables simultaneous uplink and downlink operations without waiting for TDD slots.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Quantity of substance

If TDD is used in mid bands, then frequency resources are allocated, but latency increases due to waiting for right time slots

Engineering Contradiction:

Improvefrequency resourcesVSAvoidlatency

Core Design Contradiction:

Quantity of substanceVSLoss of time

Solution Approach 1:

The patent moves uplink control signalling from the time domain (TDD slots) to the frequency domain by utilizing guard bands. This allows continuous uplink control transmission without waiting for periodic TDD uplink slots, thereby reducing latency.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent prepares the guard bands in advance for dual-purpose use: they serve as protection bands for the LTE system while simultaneously being allocated for NR uplink control signalling. This preliminary allocation eliminates the need for waiting for TDD slot opportunities.

Inventive Principle:

Principle #10Preliminary action

3Quantity of substance

If spectrum sharing on low band between LTE and NR is implemented, then resource efficiency improves, but fast scheduling coordination is required which increases system complexity

Engineering Contradiction:

Improvespectrum efficiencyVSAvoidscheduling coordination

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent extracts the scheduling coordination requirement by allocating specific frequency resources (guard bands) for exclusive NR uplink control signalling. This extraction eliminates the need for fast TTI-level coordination between LTE and NR schedulers, as the NR control signalling has dedicated frequency resources independent of LTE scheduling decisions.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The guard bands serve as an intermediary resource that mediates between LTE and NR systems. By allocating these intermediate frequency resources for NR control signalling, the patent avoids direct coordination complexity between the two systems while maintaining spectrum efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If Supplementary UL with low band NR carrier is used, then uplink coverage is improved, but large frequency bands are occupied requiring at least 5 MHz

Engineering Contradiction:

Improveuplink coverageVSAvoidfrequency band size

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent uses only the partial frequency resources within the guard bands for NR uplink control signalling, rather than allocating a complete separate carrier. This partial usage provides sufficient coverage improvement without requiring the minimum 5 MHz carrier bandwidth needed for full Supplementary UL carriers.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11540281B2Carrier configuring and signalling scheduling in co-existing radio access systems

Publication Date: 2022.12.27 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method for operating a radio access system comprises configuring a first carrier and a second carrier for use for radio access in a first radio access system. The second carrier is configured for frequency division duplex signalling. A useful frequency band of the second carrier is defined to, at least partially, overlap in frequency with a useful frequency band of a third carrier of a second radio access system. At least a part of the useful frequency band of the second carrier overlaps in frequency with guard bands of the third carrier. A method for signal scheduling comprises scheduling, in a first radio access system having a first carrier with a first carrier frequency band and a second carrier with a second carrier frequency band, uplink signals in the second carrier. Network nodes for carrying out the methods are also presented.