By Amitav Mukherjee, CEO & Saeede Enayati, Principal Engineer, Tiami Networks

Imagine trying to build a digital twin of an entire city where the objective is to monitor the environment and track the flows of pedestrians, commuters, vehicles in real time. A city-scale digital twin that uses real-time data and AI to optimise energy usage in buildings, transportation systems, and city infrastructure will be a critical tool for achieving net-zero emission targets by 2040. However, deploying brand-new sensor infrastructure or hundreds of thousands of new surveillance cameras for this purpose is both prohibitively expensive and a logistical nightmare.

Here’s a revolutionary approach to this problem: take an existing pervasive communications network – the global 5G mobile network – and transform it into the world’s largest distributed radar network! This is the essence of the Integrated Sensing and Communication paradigm, which has been designated as one of the fundamental pillars of 6G by IMT 2030.

Integrated sensing and communication (ISAC) refers to wireless systems that can simultaneously sense the environment and communicate with other devices using the same radio frequency spectrum. This convergence of sensing and communications holds the promise of devices that can not only access data and voice networks but also actively probe, interact with, and map their local surroundings.

ISAC applications are numerous ranging from civil security applications, health and public safety, and environmental monitoring to industrial and infrastructure applications and automotive and navigation assistance. Below are some specific examples of use-cases:

1. Intruder detection and perimeter security: Surveillance cameras dominate the physical security market today, but monitoring performance is degraded by poor lighting, inclement weather, and blockage by obstacles. ISAC leverages existing wireless infrastructure to detect the presence of people and even UAVs in unauthorized areas.
2. Physiological monitoring: Without the need for a wearable device, ISAC provides vital signs and sleep monitoring functionality leveraging micro-doppler shift effects resulting from the subtle vibrations caused by breathing.
3. Traffic classification: 5G networks are already pervasive in urban areas, implying that traffic patterns and pedestrian/vehicle traffic volumes can be tracked on a city-wide scale in real time for smart city and mobility optimization applications.
4. Rainfall monitoring: With widespread 5G base stations, timely and cost-effective rainfall monitoring for environmental management becomes feasible across much larger coverage areas, compared to dedicated rainfall sensors.
5. AGV Detection and tracking in factories: The coexistence of human workers and automated guided vehicles (AGVs) has significantly increased in factories where AGVs are typically employed for transporting heavy loads. Unlocking sensing capabilities of private 5G, AGVs can now be tracked and their proximity to human workers can be detected and announced to the workers through safety applications.

Key Benefits of ISAC

There are several reasons why integrated sensing and communication systems are garnering so much interest in the 5G-Advanced and 6G research community:

1. Efficiency – Sharing hardware and spectrum between sensing and communications allows for greater efficiency. Using a single system means lower cost, weight, power draw, and complexity.

2. Versatility – Joint communication and radar/sensing systems can dynamically optimise based on current needs and conditions. Bandwidth and resources can be shifted fluidly between different modes.

3. Resolution – Integrated sensing systems could enable very high-resolution sensing and positioning far beyond what GPS or network triangulation can provide today. Compared to standard video cameras, ISAC sensors are less affected by poor lighting or inclement weather, are privacy-preserving by definition, do not require high-bandwidth cable or fiber backhaul, and can sense through walls and around obstacles.

4. Intelligence – On-device real-time environmental sensing enables devices and objects to be far more aware and autonomous, interacting intelligently with users and surroundings.

These benefits come from converging what have traditionally been very separate sensor/radar and communications systems under the same framework using advanced joint transmission schemes and signal processing. Research so far has shown great promise in developing systems that can simultaneously transmit and receive radar and communications waveforms without interference.

From a monetisation point of view, ISAC allows mobile network operators to create an entirely new revenue stream from real-time sensing data that leverages their existing network infrastructure and licensed spectrum holdings.

Standards Roadmap

The new 3GPP Rel-19 Study Item (SI) for ISAC is focused on channel modeling aspects to support object detection and/or tracking and distinguishing target objects from non-target objects within a primary frequency range of interest from 0.5 GHz to 52.6 GHz. Specific use cases of interest are:

• UAVs
• Humans indoors and outdoors
• Automotive vehicles (at least outdoors)
• Automated guided vehicles (e.g. in indoor factories)
• Objects creating hazards on roads/railways, with a minimum size dependent on frequency.

The technical specifications for 5G-Advanced ISAC are expected to be completed in Rel-20 by 2026. However, the telecom industry does not need to wait until Rel-20 or 6G for ISAC.

At MWC Barcelona 2024 we will showcase two 5G-based ISAC demonstrations where we present human target sensing capabilities using the over-the-air 5G signals. We will illustrate how the received reflected signals can be used to identify different human gestures using deep learning algorithms. For example, one can be identified as waving his hand or clapping. We will also present a person-counting demo with real-time occupancy tracking based on reflections of the 5G signal.

The Killer App for 6G

We believe ISAC represents the “killer app” that could drive entirely new revenue streams and use cases for future 6G networks. Without applications like ISAC, 6G will just be a capacity upgrade to handle more cellular traffic than 5G. As the applications become compelling, it will drive users and businesses to upgrade devices and infrastructure.

Technical Challenges

There are still significant research problems around developing advanced integrated communication and radar systems before the 6G vision can become reality. ISAC-specific channel modeling is a key technical challenge. As sensing is completely dependent on the reflected signals from the objects, it is essential to include object characteristics in the channel models. To provide suitable channel models for sensing, one approach is to use ray tracing (RT) in various scenarios. However, this approach requires a significant amount of computational capacity. Less computationally intensive approaches, such as stochastic models, attempt to incorporate object characteristics in existing channel models. For example, it is crucial to account for the radar cross-section (RCS) of targets in the channel modeling to include the further signal attenuation by the objects.

ISAC faces other challenges besides channel modeling, including:

• Tradeoff between communication and sensing: Achieving a balance between the communication and sensing requirements is crucial for each application.
• Hardware imperfections: Proper design of integrated RF architecture and self-interference cancellation in an ISAC system are key technical problems that need to be addressed.
• Security and privacy concerns: With the widespread sensing capability and sensing data traveling through the network the risk of users’ privacy leakage in different levels increases, which needs to be taken seriously.

It is still early days for 6G integrated sensing and communication networks – we likely won’t see standardisation and commercial implementation until the end of this decade. However, all signs point to ISAC becoming a crown jewel of the 6G value proposition given the transformational use cases it could enable. From there, we may see capabilities that even 6G researchers can just scratch the surface of conceiving today.