Small Cell RACH Beacon Wake-Up for Low Power Detection

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Solution Overview

Problem

In heterogeneous wireless communication networks, small cells often remain in power-save mode for extended periods, limiting detection and communication with mobile devices when they reenter the coverage area, as existing solutions require continuous beacon transmission by small cells, which is inefficient.

Innovation Solution

The method involves exchanging beacon parameters with user equipment (UE) in high power mode, entering low power mode, and activating a listening component to receive beacons in a random access channel (RACH) preamble, triggering a power mode change to high power and association with the UE upon detection, while neighboring cells can also assist in power mode changes via notifications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the small cell transmits continuous beacons to enable mobile device detection, then detection reliability is improved, but power consumption increases

Engineering Contradiction:

Improvedetection reliabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The small cell alternates between sleep mode and active detection mode in periodic cycles. During sleep mode, the small cell consumes minimal power. When a UE enters the coverage area and transmits a RACH beacon, the small cell wakes up to detect the beacon and establish communication. This periodic activation pattern reduces overall power consumption while maintaining detection capability when needed.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The UE performs self-service by actively transmitting beacons in RACH preambles when it detects the small cell's coverage area. This allows the UE to initiate the detection process rather than relying on the small cell to continuously transmit beacons, enabling the small cell to remain in low-power mode while still achieving reliable detection when UEs are present.

Inventive Principle:

Principle #25Self-service

2Use of energy by moving object

If the small cell remains in power-save mode for extended periods, then power consumption is reduced, but detection capability deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoiddetection capability

Core Design Contradiction:

Use of energy by moving objectVSDifficulty of detecting and measuring

Solution Approach 1:

Instead of the small cell actively transmitting beacons to announce its presence, the invention inverts the approach: the small cell remains silent in power-save mode, and UEs actively transmit beacons in RACH preambles to announce their presence. The small cell wakes up only to detect these UE-initiated beacons, thereby maintaining detection capability while minimizing power consumption.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The RACH beacon serves as an intermediary signal that bridges the gap between the UE and the sleeping small cell. The UE transmits the beacon containing small cell information, which acts as a wake-up call and identification signal, enabling the small cell to detect the UE's presence and initiate communication without continuous beacon transmission.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the small cell wakes up upon receiving a beacon to establish communication, then communication reliability is improved, but latency increases

Engineering Contradiction:

Improvecommunication reliabilityVSAvoidcommunication latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The UE performs preliminary actions by detecting the small cell's coverage area and preparing the RACH beacon with necessary small cell information before the small cell wakes up. When the small cell receives this pre-prepared beacon, it can quickly authenticate and establish communication without requiring extensive setup time, thereby reducing overall latency while maintaining reliability.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP2941924B1UE beaconing using RACH transmissions for small cells

Publication Date: 2018.06.06 QUALCOMM INC

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AI summary

A method of beacon detection performed by a small cell device includes: exchanging beacon parameters with a user equipment (UE); entering a low power mode after exchanging the beacon parameters with the UE; receiving, from the UE, a beacon in a random access channel (RACH) preamble containing the beacon parameters while in the low power mode; entering a high power mode in response to receiving the beacon; and associating with the UE while in the high power mode. The method of beacon detection allows a small cell device to transition from a low power mode to a high power mode in an efficient manner. The transmission may be triggered by a user equipment that is entering a service area of the small cell device.