Cooperating User Equipments

Description

Cooperating UEs is a concept introduced in 3GPP Release 20, defined in specification 22.870, which describes a group of User Equipments (UEs) that have associated subscriptions enabling them to cooperate with each other when they are in proximity. This cooperation is coordinated by the network and aims to improve energy efficiency and user experience. The concept is part of the broader study on energy efficiency and service aspects for 5G and beyond, where device-to-device (D2D) and proximity-based services (ProSe) are leveraged to enable new forms of collaboration.

The core idea is that UEs can form a cooperating group based on their subscriptions, which may include specific service agreements or permissions that allow them to share resources, relay traffic, or coordinate their transmission and reception. When these UEs are in proximity (e.g., within direct communication range), the network can coordinate their cooperation to achieve benefits such as reduced power consumption, improved coverage, or enhanced data rates. For example, UEs could cooperate to relay data for each other, aggregate their antennas for joint transmission/reception, or share computational resources for energy-intensive tasks.

The cooperation is managed by the network, which maintains awareness of the UEs' proximity, subscription profiles, and capabilities. The network can initiate, modify, or terminate cooperation based on factors like traffic load, energy saving goals, and user preferences. The cooperation may involve direct UE-to-UE links (e.g., sidelink) or network-assisted coordination. The subscriptions associated with the UEs are crucial because they define the permissions and policies for cooperation, ensuring that only authorized UEs can participate and that security and privacy are maintained.

From an architectural perspective, cooperating UEs can be seen as an extension of ProSe and sidelink communication, but with a focus on energy efficiency and user experience. The network elements involved include the UE, the Radio Access Network (RAN), and core network functions such as the ProSe Function, Unified Data Management (UDM), and Policy Control Function (PCF). The UDM stores subscription data that indicates whether a UE is allowed to cooperate, and the PCF provides policies for cooperation. The RAN coordinates the radio resources for cooperation, potentially using sidelink or other direct communication technologies.

The benefits of cooperating UEs are manifold. Energy efficiency can be improved by allowing UEs to share resources, reducing the need for each UE to transmit at high power. User experience can be enhanced through better coverage, higher throughput, or lower latency. For example, a group of UEs in a cell edge area could cooperate to relay data to a UE with poor channel conditions, effectively extending coverage. Alternatively, UEs could cooperate to perform distributed computing, offloading tasks from a single UE to reduce its energy consumption.

However, there are challenges. Cooperation requires trust and security among UEs, which is addressed by the subscription-based authorization. It also requires coordination and synchronization, which the network provides. The concept is still in the study phase in Release 20, and detailed procedures and protocols are expected to be defined in future releases. The introduction of cooperating UEs reflects the ongoing trend towards more intelligent, collaborative, and energy-efficient wireless networks.

Purpose & Motivation

Cooperating UEs were introduced to address the growing demand for energy efficiency and enhanced user experience in 5G and future networks. As mobile devices become more powerful and applications more demanding, energy consumption is a critical concern. Traditional approaches to energy saving focus on the network side (e.g., base station sleep modes), but device-side energy saving is equally important. Cooperating UEs enable devices to work together to reduce their individual energy consumption, leveraging proximity and subscription-based permissions.

The concept also aims to improve user experience by enabling new services that require collaboration among devices. For example, in scenarios like public safety or gaming, UEs can cooperate to share data or compute resources, providing better performance than each device could achieve alone. The network-coordinated aspect ensures that cooperation is efficient and does not cause interference or unfair resource usage.

Prior to Release 20, device cooperation was limited to ad-hoc solutions or specific use cases like ProSe, which focused on discovery and direct communication but not necessarily on energy efficiency or coordinated cooperation. The introduction of cooperating UEs provides a standardized framework that integrates with network management and policy control, making cooperation a first-class feature of the network. This is a step towards a more collaborative and sustainable wireless ecosystem.