Employing advanced broadband-communication techniques to deliver cost-effective, two-way data communication over AC and DC powerlines at speeds up to 100 kbps, Maxim Integrated Products has developed an OFDM-based, PLC modem. By using existing powerlines, this highly integrated SoC reduces the need for external cables to interconnect between network nodes. Supporting a wide, 10 kHz to 490 kHz frequency range, the MAX2990 complies with international power-line signaling regulations, including CENELEC, FCC, and ARIB.

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While the idea of using powerlines for communication goes back to the 1920s, the number of communication devices installed on dedicated wires far exceeds the number installed on AC powerlines today. However, powerlines are hostile environments. The lower, 10 kHz to 500 kHz frequency region is especially susceptible to interference, background noise, impulsive noise, and group delays. To overcome these challenges, many companies have tried different modulation techniques such as spread spectrum and other narrowband schemes. None of these solutions achieved high data rates reliably over the long distances required by today's demanding applications, according to Maxim.

However, Maxim claims to have solved the problems inherent to PLC by applying advanced, broadband communication techniques. As a result, the MAX2990 uses OFDM technology with DBPSK modulation and FEC to provide robust data communication in the presence of narrowband interferers, group delays, jammer signals, impulsive noise, and frequency-selective attenuations. In addition, the PLC modem also integrates a fast DES encryption/decryption coprocessor to enhance data security.

Whereas a typical FSK system has a BER of ~10^4 at 12 dB SNR with a data rate of ~2 kbps, the MAX2990 achieves the same BER at ~4 dB SNR with data rates of ~32 kbps in CENELEC bands between 10 kHz and 95 kHz. Thus, using OFDM technology with error-correction techniques enables an ~8dB improvement in performance at much higher data rates, stated Maxim.

To further improve performance, the MAX2990 automatically switches to robust mode when input-signal variations exceed predefined thresholds, such as SNR levels, input-fluctuation levels, and potential in-band tone reductions. As a result, this mode achieves ~5dB improvement in SNR, but at lower data rates, added Maxim.

The MAX2990 combines the PHY and MAC layers in a single chip that also integrates its 16-bit RISC microcontroller. The MAX2990 includes 32 kB of flash memory to run the MAC code and user-defined custom applications, plus 8 kB of SRAM for data memory. Additionally, it also supports UART, SPI, and I2C serial interfaces for glueless communication between the powerline and other devices on the network.

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