Amid 60 GHz debate, ST ponders WirelessHD
In a morning ISSCC session, SiBeam gave more technical details about its latest chip set, a hybrid supporting both WirelessHD and the rival WiGig Alliance’s 60 GHz spec. An evening session gave an update on competition between WirelessHD, WiGig, the IEEE 802.11ac effort and other options in the labs.
For its part, STMicro was the silent partner in an ISSCC paper that described an integrated 60 GHz transceiver implementing in a single chip the full four channels of the WirelessHD spec. The 65-nm part was a development vehicle co-designed by the CEA-LETI research institute in France.
LETI is testing several WirelessHD modules produced for ST, said Alexandre Siligaris, a LETI researcher and author of the ISSCC paper. The paper described one module measuring about 114mm2 that delivered 3.8 Gbits/s over a meter while consuming about 1.3 W.
An ST engineer would not say whether the company is considering a commercial offering, but it does own the intellectual property from the LETI work.
In another paper, SiBeam co-founder Chinh Doan described a two-chip set the company announced in May supporting WirelessHD and WiGig. It implements two 1.76 Gbit/s WirelessHD channels and has a maximum power consumption of about 2 W in transmit mode when sending 3.8 Gbits/s of data up to about 10 meters.
The chips measure about 72 and 77 mm2, use up to 32 miniature antennas and are not yet in production.
In a separate paper, Maryam Tabesh of the University of California at Berkeley described a way to lower the power of 60 GHz chips using baseband phase shifting. Doan said the approach would not be practical for SiBeam which uses a fast shifting technique to quickly and flexibly handle beam forming.
What’s beyond Wi-Fi?
In an evening session SiBeam and WiGig executives argued the relative merits of their competing technologies. Both aim to pave a path from today’s Wi-Fi to a multi-gigabit future based on 60 GHz signaling.
Jeff Gilbert, CTO of SiBeam, argued that Wi-Fi is running out of gas while 60 GHz is inherently more energy efficient. While conceding the WiGig approach is a viable Gbit version of Wi-Fi, he said WirelessHD is as good or superior in all other user scenarios.
He also took on criticisms the WirelessHD approach could not reduce power enough for use in handheld devices. He said WirelessHD products could be made today using just four antennas to deliver a single Gbit/s of data about three meters with line-of-sight while consuming about 250 milliwatts.
Ali Sadri, president of the 50-member WiGig Alliance, said the group’s 60 GHz technology is superior on several fronts.
Unlike WirelessHD and even Wi-Fi, WiGig aims to charge no royalties. It will have a Wi-Fi fallback mechanism and protocol abstraction layers supporting HDMI, DisplayPort and other interfaces.
A third option is in the works at the IEEE 802.11ac group. It is developing a 5 GHz spec using 80 and 160 MHz channels, up to 8×8 MIMO, 256 QAM and other techniques to deliver 867 Mbits/s to up to an aggregate of 6.9 Gbits/s across several devices depending on the implementation, said Rolf De Vegt, a Qualcomm engineer involved in the effort.
The 802.11ac technology could extend the familiar Wi-Fi experience far into the future, said De Vegt. It will leverage consumer hotspots and support software as well as the understanding of 5 GHz networking among Wi-Fi chip and system makers, he said.
The 802.11ac group is expected to finish its spec by the end of the year. The first compliant chips and an interoperability certification process could be in place at about the same time.
SiBeam’s Gilbert suggested 802.11ac would be power hungry and its use of 80 and 160 MHz channels could be problematic. De Vegt himself admitted China currently has no 80 MHz channels available at 5 GHz, making the technology a non-starter there.
Jri Lee, an electronic engineering professor at National Taiwan University, called for simpler, lower cost options based on proprietary line of sight techniques aiming at distances of less than two meters.
He pointed to academic papers, some at ISSCC, describing such 60 GHz systems using relatively simple antenna designs and modulation schemes such as OOK, FSK and BPSK. Such designs could deliver 2-3 Gbits/s at less than 200 milliwatts, he said.