The Future of Building Networks: Broadband PLC as the Communication Backbone

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As decarbonization efforts accelerate, Zero Emission Buildings (ZEBs) have become a key target in climate policy. Achieving ZEB status requires automation systems that can efficiently monitor and control major energy loads like HVAC and lighting.

While large buildings can absorb the cost of complex infrastructure, small-to-medium-sized buildings often struggle with the high expense of separate power and communication networks. A more integrated, cost-effective solution is needed.

Broadband Power Line Communication (PLC) offers a promising alternative. By using existing power lines for both data and energy transmission, PLC reduces wiring complexity and cost. When paired with wireless technologies, it supports a hybrid architecture that enables flexible, scalable control across a building.

With these capabilities, broadband PLC is emerging as a next-generation communication backbone for building automation.

 

Current Building Automation Architecture

Most building automation systems today rely on RS-485 communication. Although mature and widely used, RS-485 presents several limitations:

  • It requires separate wiring for communication and power, increasing material and labor costs.
  • Often, the communication and power networks have mismatched topologies, complicating installation and maintenance.
  • Its daisy-chain topology is fragile—failure of a single device can impact the entire network.
  • It is susceptible to common installation errors, such as flipped polarity, grounding issues, and missing end-of-line (EOL) resistors.

To meet safety regulations, RS-485 systems typically use low-voltage power lines (e.g., AC24V, DC24V, DC30V), which do not require licensed electricians for installation.

Alternatives to RS-485

Several alternatives to RS-485 are currently being explored:

– Wireless

Wireless systems eliminate the need for communication wiring and enable flexible device placement. However, they pose challenges in terms of reliability and interference:

  • Signal quality is highly sensitive to changes in the physical layout—partition walls, for example, can cause over 10 dB of attenuation.
  • Extending coverage often requires reducing bandwidth or increasing transmission power, both of which can cause interference with nearby systems.
  • Reliable operation demands advanced RF planning and detailed site surveys.

 

– 10Base-T1L with PoDL

10Base-T1L enables simultaneous transmission of data and power over a single twisted pair using Power over Data Line (PoDL) technology, supporting up to 60W of power. While this simplifies wiring, it has notable constraints:

  • It supports only point-to-point communication, requiring either:
    • A star topology with L2 switches, or
    • A daisy-chain topology with dual-port devices.
  • When PoDL is used, the number of daisy-chained nodes is limited by power distribution constraints.

Despite its high bandwidth and low latency, its rigid topological requirements can limit flexibility in real-world building layouts.

Broadband Power Line Communication (PLC)

Broadband PLC leverages existing power lines for data transmission, making it a compelling solution for building automation—especially over dedicated power lines like AC24V or DC24V. Its key advantages include:

  • Reduced wiring cost by eliminating separate communication lines.
  • Predictable network behavior—since only automation devices are connected, interference is limited and controllable.
  • Support for bus and free topology, aligning naturally with the structure of power line networks.

In addition to these benefits, broadband PLC also addresses several known limitations of RS-485.

RS-485 Limitation  Broadband PLC Advantage
Daisy-chain topology only Supports Free topology (bus, star, daisy, loop)
Flipped polarity Polarity-agnostic modulation schemes
Grounding problems Isolation via compact, low-cost transformers
EOL resistance requirement No EOL resistor required

 

 

– Technical Considerations

Even with dedicated lines, PLC must address certain technical issues:

  • X-capacitors in power supplies lower line impedance, attenuating communication signals.
  • Noise from switching devices can degrade signal quality.

To mitigate these issues:

  • Inductive impedance elements (e.g., coils) can be added to stabilize line impedance and suppress noise.
  • Multi-hop PLC protocols, such as Nessum, help maintain stable communication even over high attenuation or in noisy environments.

These features enable deterministic network behavior, simplifying system design. Nessum’s multi-hop capability supports up to 1,024 nodes, allowing the network to scale effectively—making it highly suitable for building automation applications.

 

 Extended Applications

By adopting the same architecture, even higher-voltage AC lines (e.g., AC110V or AC230V) can serve as reliable communication channels. This enables the use of PLC for power-hungry applications while maintaining the same benefits, making this approach a viable communication backbone for building automation—even in high-demand environments such as HVAC systems.
In this scenario, adding EMC filters at the origin of the power line further enhances signal stability.

 

Furthermore, by combining broadband PLC with wireless technology, a hybrid architecture can be realized: PLC serves as the backbone network, while wireless provides flexible access to end devices such as lighting fixtures and sensors. This approach enables centralized control over the two major sources of energy consumption in buildings—HVAC and lighting—through a cost-effective and scalable infrastructure.

 

 

Conclusion

Broadband Power Line Communication presents a practical, scalable, and cost-effective alternative to traditional wiring in building automation. By leveraging existing power lines and modern PLC technologies, it enables:

  • Simplified installation
  • Reduced material and labor costs
  • Resolution of legacy system issues such as RS-485
  • Deployment of robust, flexible networks—even in retrofit scenarios

Moreover, when combined with wireless technologies in a hybrid architecture, broadband PLC can act as a reliable communication backbone, enabling centralized control of both HVAC and lighting—the two primary sources of energy consumption in buildings. This integrated approach supports the development of smart, energy-efficient infrastructures and offers a viable path toward Zero Emission Buildings (ZEB), especially for small-to-medium-sized facilities seeking both sustainability and affordability.

 

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About the Author
Kengo Tamukai is a senior engineer specializing in wired and wireless communication technologies. With over 20 years of experience in LSI design, system architecture, and technical marketing, his expertise spans SoC design, OFDM-based technologies, and hybrid communication systems, driving innovation in modern digital networks.