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Demo Cases

6G-REFERENCE aims at centimetre-wave integrated sensing and communication (ISAC) solutions, serving many users per area with a dense network of cell-free distributed radio units (RUs).

Three demos will be developed on Communications, ISAC and Synchronisation test cases in factory-hall and urban-square scenarios:

  • Low latency Communications leveraging Full Duplex (COM)
  • Integrated Sensing and Communication: Passive vs Active Sensing (ISAC)
  • Over-the-Air accurate Frequency and Time Synchronisation (SYNC)

How? Distributed MIMO

Leveraging distributed multiple-input and multiple-output (MIMO) allows for reduced interference, enhanced coverage and reliability, higher data rates, and improved power efficiency. However, fibre access for RUs cannot be taken for granted everywhere, and certainly not in dense deployment scenarios, such as urban areas and factory halls. This makes fast high-capacity wireless data communication  and over the air wireless synchronisation key challenges.

Distributed MIMO can enable the service to numerous equipment devices capable of wireless communication exploiting cooperative RUs, where true coherent communication is the holy grail. 6G-REFERENCE explores techniques to push synchronisation accuracy along with data capacity, while also offering ISAC radar-like sensing capabilities.

The project assumes a scenario where only one RU has fibre access focusing on integrated circuit (IC) and antenna hardware with low complexity, cost, and power consumption to explore the use of 14.8-15.35 GHz cm-wave spectrum for COM, ISAC and SYNC.

As low latency communication, accurate time synchronisation and radar sensing functionality is especially useful in the context of Industry 4.0/Manufacturing, for a 100m x 100m factory, at 6G-REFERENCE we have planned a 25m hexagonal grid of RUs scenario for system design calculations, where only one Central Unit has fibre access to the midhaul network. Our demos will focus on the RU rather than user equipment hardware, and on one or two RU-RU radio-links, demonstrating feasibility and evaluating Key Performance Indicators  of the radio hardware.
Demo Case #1 – Low latency Communications leveraging Full Duplex (COM)
Full Duplex communication can ideally offer doubling of the data capacity of a given radio channel and low latency, because it supports simultaneous bi-directional communication. Current 5G new radio systems typically use time division duplexing, which does not offer this capability, as the radio channel is shared for uplink and downlink communication in different time slots. As one-way communication either in uplink or downlink occurs, this inherently brings delays. Moreover, flexibility in scheduling of uplink and downlink time slots is often limited because of interference concerns, thus coordination is required to schedule simultaneous downlink and uplink slots for neighbouring RUs to avoid mutual interference. The same holds for communication between RUs, if they cooperate in a D-MIMO network, to support joint transmission of data to a user equipment. Full duplex communication allows for simultaneous bi-directional communication, reducing latency and improving data capacity. Time Sensitive Networking (TSN) targets well-defined maximum time-delay in communication, such as deterministic communication over Ethernet and wireless networks. This is crucial for industrial automation, robotics, and real-time control. It requires communication hardware and radio links that offer a low bounded latency and high radio link reliability. Full duplex communication can potentially address these issues too. 6G-REFERENCE wants to demonstrate the feasibility of a full-duplex link budget, focusing on the hardware of one full duplex RU. As self-interference is the main challenge for full-duplex communication hardware, and we focus on antenna array and RF-IC transceiver hardware, we aim to characterise the self-interference rejection of the hardware and software that developed in the project. This will combine an antenna array with full duplex ICs and adaptive signal processing hardware to reduce self-interference.

Cross-section of a part of the Printed Circuit Board (PCB) with with patch antennas on top and Radio Frequency Integrated Circuits at the bottom

Demo Case #2 – Integrated Sensing and Communication: Passive vs Active Sensing (ISAC)

This scenario relates to Industry 4.0/Manufacturing to provide accurate sensing and localisation integrated with communications. The required user data rates and area capacity are typically much lower than in an urban square scenario, so more resources can be devoted to providing accurate sensing. In this low Technology Readiness Level (TRL) hardware-oriented use case, we aim to demonstrate:

  • Reuse of communication hardware for ISAC to assess feasibility and performance of passive radar-like sensing exploiting orthogonal frequency-division multiplexing waveforms.

The goal is to evaluate radar sensitivity and relevant hardware limitations focusing on the antenna and RF transceiver hardware. We will also leverage Time Modulated Array techniques to simultaneously transmit and/or receive sensing signals from multiple directions to simplify hardware and reduce power. 

  • Localisation exploiting frequency modulated array (FMA) techniques in the RU-hardware.

This involves two radio transceivers, such as localisation based on “active sensing” rather than passive reflections of radar radio-waves.

Demo Case #3 – Over-the-Air accurate Frequency and Time Synchronisation (SYNC)
Cooperative distributed MIMO requires accurate synchronisation in frequency and time between RUs. Such synchronisation is also relevant for TSN. The 6G-REFERENCE project targets full duplex wireless communication as well as accurate synchronisation and hence aligns well with TSN demands. KPIs include latency, frequency, phase synchronisation error and absolute time stamping accuracy.

Schematic representation of the wireless Distributed MIMO Radio Units  and the associated over-the-air synchronization and data-fronthaul links to the 6G-network

For the factory hall scenario, 6G-REFERENCE proposes channel impulse response simulations serving as a basis for analysing communication and synchronisation performance. This allows the estimate of the effect on multi-path reflections on the accuracy of time-synchronisation and explores the potential of new algorithms. The project is planning a Proof of Concept for different aspects of synchronisation, such as frequency and time synchronisation with different KPIs for short term accuracy (phase noise and jitter) and long-term variations (Allan variance).

Factory hall used for Channel Impulse Response simulations to get multi-path data for the 14.8-15.35 GHz band for time synchronization simulations preparing for physical demos

Impact of the 6G-REFERENCE Demo Cases

The 6G-REFERENCE demos aim at TRL4, enabling systems providing communication services to workers and “intelligent industrial agents”, such as automated cranes, machines, robots and vehicles with low latency and more data capacity due to full duplex hardware capabilities. Our demo cases will:

  • Provide fundamental accurate sensing services reusing the communication hardware for radar sensing (ISAC) and/or active localisation based on FMA

Complex scenarios mixing automated machines and human workers requires security measures to avoid collisions between machines and vehicles or accidents with workers. Therefore, sensing and localisation services here include detecting and tracking workers and mobile agents as well as predicting and avoiding collisions. 

  • Use sensing and localisation to monitor and control pathways and intersections shared by automated and human-driven vehicles and to assist the operation of robots with a high level of autonomy

Accurate synchronisation is key both for TSN, high data rate communication as well as accurate sensing.

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