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OFDM-based, powerline communication modem debuts

Posted: 28 May 2008 ?? ?Print Version ?Bookmark and Share

Keywords:OFDM? power-line communication? PLC modem?

ISL9301

Maxim Integrated Products has introduced the MAX2990 OFDM-based, power-line communication (PLC) modem. This device employs advanced broadband communication techniques to deliver cost-effective, two-way data communication over AC and DC powerlines at speeds up to 100Kbit/s. By using existing powerlines, it reduces the need for external cables to interconnect between network nodes.

Supporting a wide, 10kHz to 490kHz frequency range, the MAX2990 complies with international power-line signaling regulations, including CENELEC, FCC and ARIB. This highly integrated SoC is suited for applications requiring high data rates over long distances, such as automatic meter reading (AMR); energy management and load control; lighting control; and building, industrial, and home automation.

The powerline network is by far the largest network in the world. While the idea of using power lines 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.

Powerlines are hostile environments. The lower, 10kHz to 500kHz 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.

OFDM data communication
Maxim has solved the problems inherent to PLC by applying advanced, broadband communication techniques. The MAX2990 uses OFDM technology with DBPSK modulation and forward error correction (FEC) to provide robust data communication in the presence of narrowband interferers, group delays, jammer signals, impulsive noise, and frequency-selective attenuations. Consequently, the MAX2990 is said to be the industry's only broadband PLC chip that transfers data at the 10kHz to 490kHz frequency range.

Advanced networking techniques ensure a reliable, highly secure communications network. Specifically, a CSMA/CA scheme controls the data traffic flow in multiple-nodes distributed networks, and an automatic repeat request (ARQ) function ensures the delivery and receipt of incoming packets. The MAX2990 also integrates a fast DES encryption/decryption coprocessor to enhance data security.

When evaluating a modem, one of the most significant values to consider is the BER at a given SNR.

Whereas a typical FSK system has a BER of ~104 at 12dB SNR with a data rate of ~2Kbit/s, the MAX2990 achieves the same BER at ~4dB SNR with data rates of ~32Kbit/s in Cenelec bands between 10kHz and 95kHz. Thus, using OFDM technology with error-correction techniques enables an ~8dB improvement in performance at much higher data rates.

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.

The MAX2990 combines the PHY and media access control (MAC) layers in a single chip that also integrates Maxim's 16bit RISC MAXQ MCU. The MAX2990 includes 32Kbyte of flash memory to run the MAC code and user-defined custom applications, plus 8Kbyte of SRAM for data memory. Additionally, the MAX2990 supports UART, SPI and I?C serial interfaces for glueless communication between the powerline and other devices on the network.

The MAX2990 is available in a 64-pin LQFP package and is fully specified over the -40C to 85C extended temperature range. Pricing starts at $8.50 (1,000-up).





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