Expanding Robust Communication to Twisted-Pair & Any Wire Networks
Originally designed for reliable data transmission over noisy power lines, Nessum (formerly HD-PLC) is now evolving to support a broader range of communication infrastructures, including twisted-pair networks.
Challenges in Power Line Communication
Communicating over power lines presents several major challenges:
- Noise Interference – Electrical devices generate various types of noise that can disrupt communication.
- Signal Reflection – The flexibility of power line connections causes complex signal reflections, leading to frequency-selective fading.
- High Attenuation – Power circuits have very low impedance, often just a few ohms, resulting in over 10 dB of signal loss.
Without advanced modulation and error correction, reliable communication under these conditions would be nearly impossible.
Nessum’s Advanced Solutions
To address these challenges, Nessum integrates state-of-the-art technologies that ensure exceptional robustness in harsh environments.
The following figure shows the block diagram of the Nessum SoC.
- Transmission (TX): The sending packet is queued in the Nessum MAC, which manages retries, data concatenation, QoS, and other functionalities. The packet is then transferred to the Nessum PHY, where it undergoes LDPC-CC encoding, bit loading according to the tone map, and modulation via inverse OFDM. The modulated digital data is converted to analog by the ADC in the AFE and transmitted to the network.
- Reception (RX): The received signal is amplified and converted to digital data by the DAC in the AFE. The digital data is then demodulated via an OFDM demodulator, equalized, and error-corrected by FEC. Based on the error correction result, the Nessum MAC sends either an ACK or NACK and reconstructs the packet.
– LDPC-CC Forward Error Correction (FEC) and Retry Mechanism
This powerful FEC method effectively corrects errors caused by noise. Additionally, a MAC-layer retry mechanism enhances data recovery when FEC alone is insufficient. Together, these features ensure robust communication, even in environments with severe electromagnetic interference (EMI), such as electric fast transients (EFT) and surges.
The following figure illustrates this mechanism. If only a small number of data bits are corrupted, FEC can correct the errors, and an ACK is sent. However, if many data bits are corrupted, FEC cannot correct them, prompting a NACK to request a retry.
– OFDM for Reflection Management
Orthogonal Frequency-Division Multiplexing (OFDM) effectively mitigates the impact of frequency-selective fading by dynamically allocating data to high CINR (Carrier-to-Interference-plus-Noise Ratio) carriers. This allocation is continuously updated as network conditions change, ensuring optimal performance and enabling flexible, free-topology network configurations.
The following figure provides an example.
When using 32PAM, each carrier can load 5 bits of data.
However, if reflections occur, not all carriers can maintain a good CINR, leading to potential errors when loading the maximum data bits.
To minimize errors, more bits are allocated to carriers with good CINR, while fewer bits are assigned to carriers with poor CINR.
– State-of-the-Art Analog Front-End
With a high dynamic range exceeding 100 dB, Nessum’s advanced analog front-end technology effectively counters severe signal attenuation caused by low impedance. This high dynamic range enables point-to-point communication over distances exceeding 1 km. It also ensures stable communication over several hundred meters, even in the presence of cable and split losses.
The following figure illustrates this concept. When there is a 1 km cable between Nessum devices, the typical cable loss with a 10 MHz band is about 0.5–1.5 dB/m. If a 0.1 dB/m cable is used, the total cable loss is approximately 100 dB (0.1 dB/m × 1,000 m).
Beyond Power Lines: A New Era of Connectivity
By applying these innovations to twisted-pair and other wire-based networks, Nessum extends its robust, interference-resistant communication technology beyond traditional power line systems. As industries seek greater flexibility and reliability, Nessum is paving the way for the next generation of high-performance networking solutions.
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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.
