Hybrid Preamble for LAA-LTE Channel Sharing

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Solution Overview

Problem

In LAA-LTE operations, WLAN devices do not recognize LTE signals on unlicensed carriers, leading to interference and increased power consumption, as they treat LTE signals as unknown transmissions and continue monitoring, causing concurrent transmissions and crosstalk.

Innovation Solution

The implementation of hybrid preambles that indicate the length of LTE signals, compatible with both LTE and WLAN frame structures, allowing WLAN devices to detect LTE transmissions and power down, reducing interference and power consumption, while maintaining compatibility with LTE features like OFDMA and cross-carrier scheduling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If LTE signals are transmitted on unlicensed carriers, then spectrum utilization is improved, but WLAN devices cannot recognize these signals leading to interference and increased power consumption

Engineering Contradiction:

Improvespectrum utilizationVSAvoidinterference and power consumption

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

A hybrid preamble structure is introduced as an intermediary element that bridges LTE and WLAN systems. The preamble includes both LTE-specific signals (CRS, PSS, SSS) and WLAN-compatible signals (L-STF, L-LTF, L-SIG), allowing WLAN devices to detect and recognize LTE transmissions on unlicensed carriers while maintaining LTE functionality. This mediator enables coexistence by making LTE signals visible to WLAN devices in the form they can understand.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If WLAN devices continue monitoring unlicensed carriers for unknown transmissions, then detection sensitivity is maintained, but power consumption increases

Engineering Contradiction:

Improvedetection sensitivityVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The hybrid preamble enables WLAN devices to self-identify LTE transmissions through familiar WLAN-compatible signals (L-STF, L-LTF, L-SIG). When these signals are detected, WLAN devices can automatically determine that the channel is occupied by LTE and enter sleep mode, saving power while maintaining detection capability. The system serves itself by using the same detection mechanisms WLAN devices already possess.

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If hybrid preambles are implemented for WLAN compatibility, then coexistence with WLAN devices is improved, but system complexity increases

Engineering Contradiction:

Improvecoexistence capabilityVSAvoidpreamble structure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The hybrid preamble is segmented into distinct functional components: LTE synchronization signals (PSS, SSS), LTE reference signals (CRS), and WLAN-compatible signals (L-STF, L-LTF, L-SIG). Each segment serves a specific purpose and can be independently processed. This segmentation allows the system to manage complexity by handling different signal types separately while achieving overall compatibility with both LTE and WLAN standards.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentEP3202223B1Sharing channels in a licensed-assisted access in long term evolution operation

Publication Date: 2021.01.27 BLACKBERRY LTD

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AI summary

A channel sharing method includes determining a starting time for transmission on an LAA-LTE channel. A length of a hybrid preamble is determined based on the starting time and a predetermined transmission time boundary. Subsequent to determining the length of the hybrid preamble, the hybrid preamble having the determined length is transmitted. Subsequent to the hybrid preamble, a Long Term Evolution (LTE) signal is transmitted.