OFDM technology creates novel powerline modem
Maxim Integrated Products
MAX2990
The MAX2990 uses OFDM technology with DBPSK modulation and forward error correction to provide robust datacommunications in the presence of narrowband interference.
New from Maxim Integrated Products, the MAX2990 is an OFDM-based powerline communication (PLC) modem that uses advanced broadband-communication techniques to deliver cost-effective two-way datacommunications 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, 10 to 490kHz frequency range, the MAX2990 complies with international powerline signalling regulations, including Cenelec, FCC and ARIB.
This highly integrated SoC is ideal for applications requiring high datarates 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.
Although 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, 10 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 datarates reliably over the long distances required by today's demanding applications.
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 datacommunications in the presence of narrowband interference, group delays, jammer signals, impulsive noise and frequency-selective attenuations.
Consequently, the MAX2990 is the industry's only broadband PLC chip that transfers data over the 10 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.
The high number of tones available from OFDM systems enables the MAX2990 to implement data-recovery schemes such as Reed Solomon and convolutional encoding.
These advanced channel-coding techniques provide error-correction bits that can be transmitted with the data on different tones to maximise data recovery.
This OFDM capability makes the MAX2990 the industry's most robust PLC modem.
When evaluating a modem, one of the most significant values to consider is the bit-error rate (BER) at a given signal-to-noise ratio (SNR).
The BER is the ratio of the lost bits to the transmitted bits at a certain noise level.
Whereas a typical FSK system has a BER of around 100ppm at 12dB SNR with a datarate of around 2Kbit/s, the MAX2990 achieves the same BER at around 4dB SNR with datarates around 32Kbit/s in Cenelec bands between 10 and 95kHz.
Thus, using OFDM technology with error-correction techniques enables around an 8dB improvement in performance at much higher datarates.
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 around 5dB improvement in SNR, but at lower datarates.
The MAX2990 combines the physical (PHY) and media access control (MAC) layers in a single chip that also integrates Maxim's 16bit RISC MAXQ microcontroller.
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 I2C 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 -40 to +85C extended temperature range.
Pricing starts at US $8.50 (1000-up).
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