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Proprietary wireless hi-fi tech beats Wi-Fi, Bluetooth

Posted: 24 Oct 2007 ?? ?Print Version ?Bookmark and Share

Keywords:wireless hi-fi? Bluetooth? Wi-Fi?

Through pairing wireless and hi-fi audio, fabless chip vendor Avnera Corp. touts chipsets for wireless audio connections in the 2.4GHz band that outperform data-oriented wireless connections in range, freedom from interference, automatic network configuration and full CD-quality sound. The proprietary approach, however, means the chipsets are not interoperable with other brands.

The company has spent the past three years in R&D mode, perfecting "chipsets that provide a wireless audio connection that rivals wired connections in both quality and ease-of-use. You can't do that using a standard designed for data transfers," said Avnera CEO Manpreet Khaira.

Khaira earlier was CEO of Mobilian, the first company to put Bluetooth and Wi-Fi (IEEE 802.11) on the same chipset. Intel bought the company in 2003. "At Mobilian, we'd tried everything we could think of to ease the user experience with complex network setups," said Khaira. "But we were constrained by the Wi-Fi and Bluetooth standards."

Network configuration
High-fidelity audio is a one-way street: Data moves from the music player to the speakers. But Wi-Fi and Bluetooth are both designed to transmit data packets using a two-way transceiver and thus require complex network configuration settings for the twin channels. Because the data-based standards require that handshaking signals be transmitted back to the sender, their chips sets' radio section is twice as complicated as Avnera's one-way connection, according to Khaira.

The need for arcane network configuration coding compounds the headaches for users of the data-oriented wireless approaches. Even Bluetooth forces users to "pair" each receiver manually to each transmitter by shuttling between the devices and keying in matching codes. Avnera's approach, Khaira said, "automates network configuration."

To deal with interference problems, meanwhile, Bluetooth and Wi-Fi use built-in packet retransmission protocols. When a corrupted data packet arrives, a handshaking fault signal is returned to the sender, forcing the network to retransmit the corrupted data packet out of order with the rest of the data stream. To avoid clicks and pops, audio connections must use memory buffers to reshuffle the out-of-order packets.

Avnera claims to have solved those problems in a transparent manner with a technology that does not retransmit data to correct errors and thus requires no memory buffering.

The startup has also perfected "wireless error correction by extending the kind of algorithms that CD players use to mask errors from scratches, plus they have added a few new twists," said Will Strauss, senior analyst at Forward Concepts.

The approach promises a fixed end-to-end latency of about 30ms, with built-in echo cancellation, by performing error correction on corrupted data packets in real-time. Using a CDMA architecture, Avnera first adds a forward error correction packet repair algorithm that makes use of extra bits transmitted with each 16-bit sample value to correct corruption from short bursts of interference.

For longer interference bursts, a concealment algorithm uses time dispersion to "hide" the errors from the user. Each packet contains some bits from the previous sample value and some from the next sample value, enabling intelligent guesses as to the values of corrupted bits.

To deal with corrupted data values too long to be corrected by intelligent concealment, the radio in Avnera's transmitter can switch among up to 40 channelseach only about 2MHz wideacross the entire 2.4GHz band, compared with about one-third of the band for Wi-Fi. The small Avnera channels automatically organize themselves around the other users of the 2.4GHz band. In the lab, Avnera has had up to 24 channels simultaneously self-organize around larger Wi-Fi channels. Switching channels takes about 16ms. For times when even channel switching cannot avoid interference, the approach supports two separate antennas.

Avnera chips also dynamically modulate the power of their transmitters. For mobile users wearing cordless headphones or VoIP headsets, the power of the radio transmitter will vary as the user moves about, compensating for the changes in distance from the basestation and for the varying density of the media through which the signal travels. The company says its transmitters offer just under 50 feet of range for signals traveling through typical walls, but hundreds of feet of range when signals are traveling through air.

- R. Colin Johnson
EE Times




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