Out-of-Coverage UE Relay Handover via Uplink Signal Measurement
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Solution Overview
Problem
In LTE communication systems, out-of-coverage devices face challenges in handover processes when switching from one in-coverage relay node to another, as they lack continuous downlink signals for measurement comparisons, differing from traditional handovers between base stations.
Innovation Solution
The implementation of device-to-device (D2D) communication techniques allows out-of-coverage UE to select and connect with a new in-coverage UE as a relay node by triggering handover discovery beacons and measuring signal strength, enabling autonomous reselection or network-directed handover processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional handover procedures between base stations are used, then network control and management are simplified, but out-of-coverage devices cannot perform handover due to lack of continuous downlink signals for measurement
Solution Approach 1:
The out-of-coverage UE autonomously performs handover by independently measuring uplink signals from candidate relay UEs and selecting the best relay without requiring continuous downlink signals or traditional network-controlled handover procedures. The device serves itself by making handover decisions based on uplink measurements rather than relying on network-provided downlink measurement signals.
Solution Approach 2:
Instead of using the traditional downlink-based measurement approach where the network provides downlink signals for UEs to measure, this invention inverts the approach by having UEs measure uplink signals from candidate relay nodes. This reversal enables out-of-coverage devices to perform handover measurements without requiring downlink coverage from the network.
2Reliability
If device-to-device communication is implemented for relay selection, then handover can be performed without continuous downlink signals, but signaling overhead and measurement complexity increase
Solution Approach 1:
The UE autonomously measures uplink signals from multiple candidate relay UEs and independently selects the best relay for handover without requiring complex network-coordinated measurement procedures. This self-service approach reduces signaling overhead compared to traditional network-controlled relay selection while maintaining reliable continuous communication.
3Productivity
If autonomous reselection is enabled, then signaling overhead is reduced, but handover control and network management become more difficult
Solution Approach 1:
The out-of-coverage UE autonomously performs relay selection and handover by independently measuring uplink signals and making selection decisions, which reduces signaling overhead and improves handover efficiency. The network does not need to provide continuous control signals, allowing the device to self-manage the handover process while maintaining network connectivity through the selected relay.
Data Source
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AI summary
A communications device configured to transmit signals representing data to a first in-coverage communications device acting as source relay node for the communications device, the first in-coverage communications device being able to transmit signals to the infrastructure equipment of the mobile communications network, and to receive signals representing the data from the first in-coverage communications device acting as the source relay node. The source relay node is within a coverage area of the infrastructure equipment of the mobile communications network, the source relay node being configured to transmit the signals representing the data received from the communications device to the infrastructure equipment and to transmit the signals representing the data to the communications device which are received from the infrastructure equipment. Subject to predetermined conditions, the controller is configured to receive one or more beacon signals from one or more other in-coverage communications devices which can act as a relay node for the communications device when out-of-coverage so that the receiver cannot receive the signals from the infrastructure equipment or transmit the signals to the infrastructure equipment, or to transmit a beacon signal to the one or more other in-coverage communications devices which can act as a relay node for the communications device when out-of-coverage, and to transmit the signals representing the data to one of the other in-coverage communications devices to act as a target relay node for transmitting the data to the infrastructure equipment, or to receive the signals representing the data from one of the other in-coverage communications devices acting as a target relay node which have been received from the infrastructure equipment. Accordingly, an out-of-coverage communications device, which is using an in-coverage communications device to act as a relay node to communicate data to and/or from an infrastructure equipment can change affiliation from one in-coverage communications device to another.