Flexible GMSK Modulation for Low-Power Cellular IoT

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Solution Overview

Problem

In cellular IoT systems, power-limited user equipment (UE) devices face significant challenges with high peak-to-average power ratio (PAPR) in modulation schemes, leading to increased power consumption and reduced range, especially in low-throughput applications where devices infrequently communicate small amounts of data.

Innovation Solution

Implementing flexible Gaussian minimum shift keying (GMSK) in combination with orthogonal frequency division multiple access (OFDMA) for downlink and single carrier frequency division multiple access (SC-FDMA) for uplink modulation, using a narrowband resource allocation that adjusts based on power limitations and channel conditions, and employing flexible bandwidth allocation to optimize power usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional modulation schemes are used in uplink transmissions, then data communication capability is maintained, but peak-to-average power ratio increases leading to high power consumption

Engineering Contradiction:

Improvepower consumptionVSAvoidcommunication reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent changes the modulation parameter from conventional schemes (QPSK, 16-QAM) to GMSK modulation, which inherently maintains a constant envelope and low PAPR. This parameter change allows the power amplifier to operate in a more efficient region, significantly reducing power consumption while maintaining reliable communication for MTC devices

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If narrowband resource allocation is implemented, then power consumption is reduced, but communication flexibility is limited

Engineering Contradiction:

Improvepower consumptionVSAvoidresource allocation flexibility

Core Design Contradiction:

Use of energy by moving objectVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic narrowband resource allocation where the base station can flexibly allocate narrowband resources (1, 2, or 4 physical resource blocks) based on real-time channel conditions and device requirements. This dynamic allocation maintains adaptability while keeping the bandwidth narrow to reduce power consumption

Inventive Principle:

Principle #15Dynamics

3Use of energy by moving object

If GMSK modulation with SC-FDMA is used, then peak-to-average power ratio is reduced, but device complexity increases

Engineering Contradiction:

Improvepower consumptionVSAvoidmodulation complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent replaces complex digital signal processing operations with simpler operations by using GMSK modulation which has a constant envelope property. This substitution reduces the complexity of the power amplifier and associated circuitry, as GMSK requires less linearization and filtering compared to conventional modulation schemes

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS9681446B2Flexible Gaussian minimum shift keying in a cellular internet of things system

Publication Date: 2017.06.13 QUALCOMM INC

AI summary

Methods, systems, and devices are described for wireless communication at a UE. A user equipment (UE) may utilize orthogonal frequency division multiple access (OFDMA) for demodulating downlink messages and a combination of Gaussian minimum shift keying (GMSK) and single carrier frequency division multiple access (SC-FDMA) for uplink modulation. The uplink modulation process may include generating a symbol vector with an M-point discrete Fourier transform (DFT), filtering the symbol vector with a frequency domain Gaussian filter, generating a sample vector from the filtered symbol vector utilizing an inverse DFT, and modulating the sample vector utilizing GMSK. In some cases, the uplink modulation may be based on a narrowband resource allocation received from a base station.