5G/NR  -  ISAC  

 

 

 

ISAC(Integrated Sensing and Communication)

Integrated Sensing and Communication (ISAC) is an emerging technology that seeks to seamlessly unify wireless sensing and communication functionalities within a single system, thereby optimizing the use of both spectrum and hardware resources in a highly efficient manner. This innovative integration is widely anticipated to serve as a foundational cornerstone of future wireless networks, playing an especially pivotal role in the development and evolution of sixth-generation (6G) systems, which are expected to redefine connectivity and interaction with the physical world by the turn of the next decade. By merging these dual capabilities, ISAC aims to enable networks that not only transmit data with unprecedented speed and reliability but also actively perceive and interpret their surroundings, paving the way for advanced applications ranging from ultra-precise localization and environmental monitoring to intelligent automation and immersive human-machine interfaces, all while making smarter use of the increasingly crowded electromagnetic spectrum and reducing the reliance on separate, dedicated systems for sensing and communication tasks

Image Source : Integrated Sensing and Communications (ISAC)

ISAC Scenario

ISAC integrates sensing (e.g., radar-like capabilities to detect objects, motion, or environmental changes) and communication (data transmission) into a single system, sharing resources like spectrum, hardware, and signals. In IoT scenarios, this dual functionality is transformative because IoT devices often need to both perceive their environment (sensing) and share data with other devices or networks (communication). A typical scenario would emphasizes IoT as a key area where ISAC can shine, supporting smart cities, smart homes, and industrial automation.

Leveraging ISAC to Equip IoT Devices with “Perceive and Connect” Capabilities

This aspect focuses on how ISAC enables IoT devices to simultaneously sense their environment and establish connectivity, enhancing the efficiency and capability of IoT ecosystems.

Key Points:

  • Dual Functionality ("Perceive and Connect"):
    • Sensing: IoT devices can detect environmental data such as temperature, motion, or proximity using ISAC’s sensing capabilities. For example, a smart home sensor might detect a person’s presence while also measuring room temperature.
    • Communication: The same device can then transmit this sensory data to other devices or a central network, enabling seamless data sharing and decision-making. For instance, the smart home sensor could alert a thermostat to adjust the temperature.
    • Example :  Applications like indoor localization and human activity recognition, where IoT devices in smart homes use ISAC to sense (e.g., detect motion) and communicate (e.g., send alerts).
  • Resilient Sensing via Distributed IoT Nodes:
    • In a networked IoT system, multiple distributed nodes (e.g., sensors spread across a smart city) can collaboratively sense the environment. ISAC enhances this by allowing each node to both sense and communicate, improving the overall sensing performance.
    • Example: In a smart city, distributed sensors on streetlights can detect traffic patterns (sensing) and share this data with a central traffic management system (communication) to optimize signal timings.
  • Decentralized Transmission and Processing:
    • ISAC enables flexible deployment of IoT nodes, where sensing tasks can be distributed across devices. Each node processes local sensory data and shares findings with others, reducing reliance on a central hub.
    • Benefit: This decentralization enhances scalability and reduces latency in large-scale IoT networks.
    • Coordination among nodes (like IoT devices) is key to efficient sensing and communication.
  • Multiple-Source Data Fusion:
    • By combining sensory data from multiple IoT nodes, ISAC reduces inaccuracies in sensing. For example, fusing data from several sensors can provide a more accurate picture of a smart home’s occupancy.
  • “Sensing-with-Communication” Paradigm:
    • Unlike traditional IoT systems that follow a “communication-after-sensing” approach (where sensing happens first, followed by separate data transmission), ISAC allows simultaneous sensing and communication. This reduces delays and processing overhead.
    • Example: A smart factory sensor can detect a machine’s vibration (sensing) and instantly transmit this data to a control system (communication) using the same signal, enabling real-time adjustments.

Scenario Example:

  • Smart Home: An ISAC-enabled smart home device (e.g., a router) can sense a person’s movement (e.g., entering a room) and immediately communicate this to other devices (e.g., turning on lights or adjusting the thermostat). The distributed sensors in the home collaborate to improve accuracy (e.g., confirming the person’s location) and share findings to make coordinated decisions.

Utilizing ISAC to Meet Diverse Demands of IoT Scenarios in Future Networks

This aspect focuses on how ISAC supports the complex requirements of future IoT networks, particularly in vertical industries (e.g., manufacturing, healthcare), by tightly coupling the physical and digital worlds.

Key Points:

  • Supporting Vertical Industries:
    • Future networks (e.g., 6G) will support industries like manufacturing, healthcare, and transportation, where IoT devices such as sensors and robots are ubiquitous.
    • These devices require precise sensing (e.g., for positioning or environmental monitoring) and reliable communication (e.g., for control commands) to enable intelligent operations.
    • Example: In a smart factory, robots use ISAC to sense their positions relative to other machines while receiving real-time instructions from a control system.
  • Large-Scale Connected Sensing Architecture:
    • In large-scale IoT networks, ISAC allows devices to sense physical environment data (e.g., temperature, motion) and integrate this with digital information (e.g., historical data, AI models) for better decision-making.
    • Challenge with Traditional Systems: Conventional wireless sensor networks (WSNs) often struggle to integrate physical and digital data efficiently due to separate sensing and communication pipelines.
    • ISAC Solution: ISAC unifies these functions, enabling a tighter coupling between the physical world (sensed data) and the digital world (processed data).
  • “Sensing-with-Communication” Efficiency:
    • ISAC-enabled IoT devices reduce data-exchange delays and processing costs by performing sensing and communication simultaneously. This is a significant improvement over the traditional “communication-after-sensing” approach, where sensing data is collected first and then transmitted separately.
    • Benefit: This efficiency is crucial for large-scale IoT scenarios with many devices, where latency and resource constraints are major concerns.
    • Example: In a smart city, traffic sensors can sense congestion and immediately share this data with nearby vehicles, reducing reaction time compared to traditional WSNs.
  • Tight Coupling of Physical and Digital Realms:
    • ISAC allows IoT nodes to seamlessly bridge the physical environment (via sensing) and the digital network (via communication), enabling more intelligent and responsive systems.
    • Example: In healthcare, an ISAC-enabled wearable can sense a patient’s heart rate (physical) and integrate this data with a digital health record system (digital) for real-time monitoring and alerts.

Scenario Example:

  • Smart Factory: In an industrial IoT setting, ISAC-enabled sensors and robots sense the factory floor (e.g., detecting a malfunctioning machine) and communicate this data to a central system for immediate action. The unified signals ensure low latency, and the integration of sensory data with digital models (e.g., predictive maintenance algorithms) enables intelligent operations, surpassing the limitations of traditional WSNs.

Use Cases

Integrated Sensing and Communication (ISAC) is an emerging paradigm in wireless systems where sensing (e.g., radar-like detection of objects, distance, or motion) and communication (data transmission) are performed simultaneously using shared resources like spectrum, hardware, and signal processing. It’s particularly relevant in the context of 5G, 6G, and sub-THz/THz technologies.  

The typical use cases of ISAC span transportation (V2X), smart cities, indoor sensing, industrial automation, drones, healthcare, and security. These applications leverage ISAC’s ability to unify sensing and communication, reducing hardware complexity, spectrum congestion, and costs while meeting the demands of next-generation wireless systems like 6G. The article underscores these as key drivers, particularly in high-frequency regimes where technologies like sub-THz lens antennas shine.

Vehicular Networks (V2X - Vehicle-to-Everything)

ISAC enables vehicles to simultaneously communicate with other vehicles, infrastructure, or pedestrians (V2V, V2I, V2P) while sensing their environment (e.g., detecting obstacles, road conditions, or other vehicles).

  • How It Works: A single waveform (e.g., millimeter-wave or sub-THz) is used for both radar-like sensing (to measure distance/speed) and data exchange (e.g., traffic updates). ISAC improves spectrum efficiency and reduces latency in autonomous driving by integrating radar and communication functions (e.g., using mmWave bands like 24 GHz or 77 GHz).
  • Example: A car uses ISAC to detect a nearby vehicle’s position and velocity while sharing real-time navigation data with it..

Smart Cities and Infrastructure Monitoring

ISAC supports urban applications like traffic management, structural health monitoring, and crowd sensing while enabling high-speed communication networks.

  • How It Works: Base stations or IoT devices use ISAC to monitor environmental parameters (e.g., bridge vibrations, air quality) while providing connectivity to users. ISAC leverages shared spectrum (e.g., sub-6 GHz or mmWave) to reduce hardware costs and improve urban efficiency.
  • Example: A 6G base station tracks pedestrian movement in a busy area (sensing) while delivering ultra-fast internet to smartphones (communication).

Indoor Localization and Human Activity Recognition

ISAC enables precise indoor positioning and activity detection (e.g., gestures, breathing rates) alongside data communication, useful in homes, offices, or healthcare settings.

  • How It Works: High-frequency signals (e.g., sub-THz) reflect off objects or people, allowing sensing of their position or motion, while the same signals carry data. ISAC at THz frequencies enhances resolution for human sensing due to shorter wavelengths, with applications in elderly care (e.g., fall detection).
  • Example: A smart home router tracks a person’s location for lighting control while streaming video to their device.

Industrial IoT and Automation

In factories, ISAC supports real-time monitoring of machinery or robots (sensing) while enabling low-latency communication for control and coordination.

  • How It Works: A single system uses shared waveforms to detect equipment status (e.g., vibration, position) and transmit control signals.
  • Example: A robotic arm in a factory senses its surroundings to avoid collisions while receiving instructions over the same wireless link.

Aerial and Drone Communications

ISAC equips drones or UAVs (unmanned aerial vehicles) to perform environmental sensing (e.g., mapping terrain, detecting obstacles) while maintaining communication with ground stations or other drones.

  • How It Works: Sub-THz or mmWave signals enable high-resolution sensing and high-data-rate links, critical for real-time navigation and coordination. ISAC reduces payload weight by integrating radar and communication hardware.
  • Example: A drone maps a disaster area (sensing) while streaming live video to rescue teams (communication).

Healthcare and Biomedical Sensing

ISAC enables non-invasive monitoring of vital signs (e.g., heart rate, breathing) while supporting data transmission for telemedicine or patient monitoring systems.

  • How It Works: THz or sub-THz waves penetrate clothing but reflect off skin, allowing sensing, while also carrying medical data. ISAC’s high resolution at THz frequencies can detect subtle physiological changes.
  • Example: A wearable device tracks a patient’s respiration rate and sends it to a doctor in real time.

Security and Surveillance

ISAC supports perimeter monitoring, motion detection, or imaging while enabling secure communication links for coordination.

  • How It Works: A single system uses reflected signals to detect intruders or objects and transmits alerts or video feeds. ISAC’s dual functionality enhances efficiency in security applications, leveraging high-directivity beams (e.g., via lens antennas).
  • Example: An airport security system scans for hidden objects on passengers (sensing) while relaying data to control rooms (communication).

Challenges

The challenges of Integrated Sensing and Communication (ISAC) are multifaceted, spanning technical, operational, and practical domains. ISAC aims to combine sensing (e.g., radar-like functionality) and communication (data transmission) into a unified system using shared resources like spectrum and hardware. While this offers significant benefits, it introduces complexities that must be addressed for effective deployment.

The challenges of ISAC include balancing sensing and communication performance, managing interference, overcoming hardware limitations, handling complex signal processing, navigating spectrum regulations, addressing propagation issues, achieving standardization, and ensuring security/privacy. The referenced article underscores many of these, particularly the technical trade-offs

Image Source : Integrated Sensing and Communications: Recent Advances and Ten Open Challenges

Trade-off Between Sensing and Communication Performance

Sensing and communication have different objectives—sensing requires high resolution and accuracy (e.g., for target detection), while communication prioritizes data rate and reliability. Optimizing for one often degrades the other.

Designing a waveform that serves both purposes effectively is difficult. For example, radar prefers long, continuous waveforms for range resolution, while communication favors short, modulated signals for high throughput.

We would need to consider the "sensing-communication trade-off," noting that joint waveform design must balance parameters like signal-to-noise ratio (SNR) for communication and Cramer-Rao Lower Bound (CRLB) for sensing accuracy. Orthogonal frequency-division multiplexing (OFDM), commonly used in communication, may not be ideal for sensing without modifications.

Example: In vehicular ISAC, a waveform optimized for high-speed data (e.g., 6G) might fail to detect small obstacles accurately.

Interference Management

Since ISAC systems share spectrum for sensing and communication, self-interference (e.g., communication signals disrupting sensing) and mutual interference (between multiple ISAC nodes) are significant issues.

Isolating or mitigating interference while maintaining performance is complex, especially in dense environments like urban areas or multi-user networks.

This challenges would be particularly serious in multi-user ISAC scenarios. We would need advanced signal processing (e.g., interference cancellation) and resource allocation (e.g., time/frequency division) as potential solutions, but these increase system complexity.

Example: In a smart city, multiple ISAC-enabled base stations might interfere, degrading both traffic sensing and data links.

Hardware Constraints

ISAC requires hardware that can handle dual functionalities, often at high frequencies (e.g., mmWave or sub-THz), where components like antennas, transceivers, and amplifiers face efficiency and precision limits.

Designing compact, cost-effective, and power-efficient hardware that supports both high-gain sensing and wide-bandwidth communication is tough. Sub-THz systems, for instance, suffer from low power amplifier efficiency and high fabrication costs.

These hardware challenges would arise at particularly at higher frequencies (e.g., THz bands), where lens antennas help but require precise alignment and integration with photoconductive sources or detectors.

Example: A sub-THz ISAC device might need a lens antenna for beamforming, but misalignment or material losses could degrade performance.

Signal Processing Complexity

Extracting sensing information (e.g., range, velocity) and decoding communication data from the same signal demands sophisticated algorithms, increasing computational overhead.

Real-time processing is essential for applications like autonomous driving, but joint sensing-communication algorithms (e.g., matrix factorization, deep learning) are resource-intensive and latency-sensitive.

We would  need  "low-complexity algorithms" to handle tasks like target detection and channel estimation simultaneously. We may think of Machine learning as a promising but computationally heavy approach.

Example: In a drone ISAC system, distinguishing a faint echo (sensing) from a noisy data stream (communication) in real time is computationally demanding.

Spectrum Allocation and Regulatory Issues

ISAC relies on shared spectrum, but regulatory frameworks often separate sensing (e.g., radar bands) and communication (e.g., cellular bands), complicating deployment.

Convincing regulators to allow flexible spectrum use and managing coexistence with legacy systems (e.g., traditional radar or Wi-Fi) is a hurdle. Higher bands like sub-THz are less regulated but face propagation challenges.

We may propose spectrum sharing as a motivation for ISAC, implying regulatory adaptation as an implicit challenge.

Example: Deploying ISAC in the 77 GHz automotive radar band might conflict with existing radar-only systems unless regulators adjust rules.

Propagation and Environmental Limitations

At higher frequencies (e.g., mmWave, sub-THz) used in ISAC, signals suffer from high path loss, atmospheric absorption (e.g., by water vapor), and sensitivity to blockages, limiting range and reliability.

Sensing and communication both require line-of-sight (LOS) or strong reflections, but urban or indoor environments with obstacles (walls, trees) degrade performance.

THz frequencies, while offering high resolution for sensing, face "severe propagation losses," necessitating advanced beamforming (e.g., via lens antennas) and relay strategies.

Example: A sub-THz ISAC system for indoor healthcare might fail to sense breathing through a wall while also dropping data connectivity.

Standardization and Interoperability

ISAC is a nascent field lacking unified standards, making it hard to ensure compatibility across devices, vendors, or applications.

Without agreed-upon protocols for waveforms, hardware, or performance metrics, scaling ISAC (e.g., in 6G networks) is slow and fragmented.

Example: Two ISAC-enabled cars from different manufacturers might not coordinate effectively without a common framework.

Security and Privacy Concerns

ISAC’s dual role means it collects environmental data (sensing) while transmitting user data (communication), raising risks of eavesdropping, spoofing, or unintended data leakage.

Securing both functions simultaneously is tricky—sensing signals could reveal sensitive information (e.g., a person’s location), while communication channels must resist jamming or interception.

Example: An ISAC surveillance system might inadvertently expose a user’s activity patterns to attackers.

Reference :

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