Wireless transceivers support HomeRF spec
By Stephan Ohr
EE Times
(02/26/99, 12:17 p.m. EDT)
SAN JOSE, Calif. — New 2.4-GHz integrated transceivers announced at the Wireless Symposium this week show that manufacturers are eyeing the potentially explosive wireless home-networking consumer market. Offerings from Harris Semiconductor (Melbourne, Fla.), National Semiconductor (Santa Clara, Calif.) and Philips Semiconductors (Sunnyvale, Calif.) demonstrated an affinity for wireless consumer schemes, though they were not specifically intended for products based on an emerging HomeRF specification.
Meanwhile, officials of the HomeRF networking consortium conducted an introductory seminar in conjunction with the Wireless Symposium. The consortium reported that it was exploring multimedia extensions to its Shared Wireless Access Protocol-Cordless Access (SWAP-CA) spec, and predicted a possible race to market on the part of product developers. Indeed, it now seems clear that many manufacturers will have products out as early as June, said Ben Manny of Intel (Hillsboro, Ore.), who is chairman of the HomeRF consortium.
The consortium is attracting interest in wireless networking from unlikely sources. Those include the Mac Wireless Consortium, an Apple Macintosh group; the State of California's Public Utilities Commission, and a variety of toy makers who insist that a low-data-rate "HomeRF-Lite" specification should build systems with a $3 bill of materials.
Separately, VLSI Technology introduced this week a transceiver chip for the Bluetooth, a short-range wireless scheme that also operates in the 2.4-GHz ISM band. Like HomeRF, Bluetooth offers wireless connectivity among cell phones, portable PCs and peripherals. Bluetooth uses a simple binary FM modulation scheme and a 1-Mbit/second data rate to minimize transceiver complexity. HomeRF will support data rates up to 2 Mbits/s.
SiGe solution
The new transceiver chips-and interest in the 2.4-GHz ISM band in which HomeRF proposes to operate-were among the high points of the Wireless Symposium. Harris' Prism II chip set uses silicon germanium (SiGe) to bring the "antenna-to-bits" solution from eight chips to four, said Chris Henningsen, director of marketing for communications products. Besides cutting the power consumption of an IEEE 802.11 transceiver in half, the bill of materials cost of a transceiver card drops to $70, Harris said.
The Prism-II chip set includes a power amplifier/detector (the HFA3983), an RF/intermediate-frequency converter (the HFA3683), an IF Qmodem (the HFA3783)-all using SiGe-and a baseband processor (the HFA3861). A separate MAC is required, but Harris' recent acquisition of MAC supplier Choice Microsystems (San Antonio, Texas) should lower the cost of a Prism-compatible device.
The Prism-II LAN offers IEEE 802.11-compatible data rates up to 11 Mbits/s. Henningsen believes that simple process scaling and die shrinks can bring this up 30 Mbits/s. Harris participates in the HomeRF consortium, and believes the chip set can be adapted to the needs of consumer networks.
Because Harris' solution uses direct synthesis spread spectrum (DSSS), it may turn out to be pricey for HomeRF networks, which use frequency-hopping spread spectrum (FHSS). DSSS requires a highly linear transceiver to extract I & Q components, said Benno Ritter, communications product marketer at Philips Semiconductors. That requirement is eliminated with FHSS.
Using FHSS, the SWAP-CA specification allows digitized voice and data to be transmitted. Data will be handled by IEEE 802.11 protocols; voice by DECT protocols (the Digital European Cordless Telephony standard). Stung by criticisms that HomeRF depends too much on cordless telephony, Intel's Manny insisted that digital cordless telephony-especially DECT-provides the most accessible model for a home wireless network. The missing piece in the HomeRF spec, Manny acknowledged, was speech recognition. But once this capability is in place, the merits of using a cordless phone infrastructure like DECT would be obvious.
National's 2.4-GHz transceiver chip, in fact, builds on the company's experience in DECT. The LMX3162 can be coupled with an SC14402 for DECT handsets, or with an SC14422 integrated baseband processor to provide echo cancellation for DECT basestations. It will also support HomeRF and Bluetooth applications, said marketing director Malcolm Humphrey.
The device integrates a radio front end, 1.3-GHz PLL, 2.4-GHz frequency doubler, low-noise amplifier, high-frequency buffer, 2.4-GHz low-noise mixer, IF and high-gain-limiting amplifiers, frequency discriminator, received-signal-strength indicator and analog dc compensation loop. A GaAs transmitter, LNA and external ceramic filter would be needed to complete the transceiver.
Philips Semiconductors, a participant in the HomeRF working group, announced it is working on a BiCMOS solution for HomeRF. The goal is a direct-conversion architecture that eliminates the IF components, said Ritter. The new chip will probably be announced in May, and enter full production within a year. It will be fabricated in Philips' 0.5-micron 32-GHz Qubic3 BiCMOS process. Future implementations will incorporate FHSS modem and 802.11 MAC functions.
Ritter said that to be successful, HomeRF radio ICs will need to be priced under $10.
|
