WiGig Alliance Reveals Ultrafast Wireless Specification
The Wireless Gigabit (WiGig) Alliance published the initial specification for an ultrafast networking technology and, simultaneously, announced an agreement to interoperate with Wi-Fi. The specification covers low-power devices such as handhelds with a power budget of 500 milliwatt to 1 W.
The technology will operate in unlicensed frequencies in the 60-GHz spectrum and promises theoretical maximum data rates of 7 gigabits per second (Gbps) over a distance up to 10 meters. WiGig Alliance members include Agilent, Atheros, Broadcom, Dell, Intel, and Nokia. Ali Sadri, its chair and president as well as director of wireless personal area networking (WPAN) and 60-GHz standards at Intel, believes that WiGig will become the dominant standard for ultrafast communications over short distances.
"Our idea is to have one radio that’s capable of addressing multiple applications and uses," said Sadri. "Clearly, multi-Gbps networking, connectivity, and wireless display mark the sweet spot of WiGig technology."
The group is developing three separate specifications to work over the core physical layer: one for IP networking, one for I/O, and a third for A/V transmission. The first specification is complete. WiGig has submitted it to IEEE as a proposed specification for IEEE 802.11ad. IEEE has confirmed the specification, which means it will take a 75 percent vote to make any changes. The second two specifications are still in development and expected to be finalized over the next year.
The sequence for the first WiGig specification represents a change, said Craig Mathias, an analyst with the Farpoint Group. Traditionally, a specification is defined according to a standard. In this case, an industry trade group defined the specification with plans to build interoperable products before the standard’s release. "It used to be that standards came first, and now it's an afterthought," Mathias said. "Now people believe they can make money well in advance of the standard."
Dawn of 60 GHz
WiGig technology will operate between 57 and 64 GHz. Mathias thinks it won't have the range of 5- or 2.4-GHz transmissions, but it will be able to go through a few walls. The biggest issue is that the air's oxygen absorbs the radio waves, which reduces the signal by up to 25 dB compared with 2.4-GHz transmission. Intersatellite communications have used traditional 60-GHz radio transmission over longer ranges because the upper atmosphere has little oxygen to absorb it. Some point-to-point terrestrial 60-GHz applications can go up to 1 kilometer with highly directional antennas.
Another challenge with the 60-GHz band has been its requirement for expensive gallium-arsenide chip-manufacturing techniques. However, lower-cost CMOS manufacturing techniques that leverage advances in microprocessor production are making 60-GHz applications more economical.
For example, SiBeam is using technology developed at the University of California, Berkeley, to mass-produce CMOS-based 60-GHz chips for transmitting high-definition video over WirelessHD. It recently announced combination WiGig/WirelessHD chip sets for system designers.
Wi-Fi on Steroids
The WiGig specification augments Wi-Fi networking with an ultrafast connection over short ranges. Existing Wi-Fi networks support IEEE 802.11a, 802.11b, and 802.11n in the 2.4- and 5-GHz bands. Wi-Fi currently maxes out at 600 Mbps, and the IEEE 802.11ac proposal on the table supports up to 1 Gbps at 5 GHz. WiGig's agreement with the Wi-Fi Alliance is designed to ensure that devices can seamlessly fall back to the other frequencies if they lose a signal in the 60-GHz band.
In contrast to existing Wi-Fi standards, "WiGig operates in the 60-GHz band with large, 2-GHz-bandwidth channels and high-allowable output power, so simpler modulation schemes can get to the lowest energy per bit of transfer," said Craig Ochikubo, Broadcom's vice president and general manager of WPAN. "Even the 5-GHz band is expected to get congested in the future, so operating in the 60-GHz band, with WiGig's inherently limited range, offers a congestion-free high-bandwidth RF link."
WiGig is also being proposed as an alternative to ultrafast I/O as a wireless replacement to USB and PCI. In this role, it would let users connect hard drives, cameras, and smart phones to a PC over a short range.
The third version of WiGig will support the transmission of HD video and audio over short ranges. Broad industry support makes the WiGig option a significant competitor to the WirelessHD specification, which also operates in the 60-GHz band, and to the Wireless Home Digital Interface (WHDI) specification, which operates in the 2.4-GHz band.
Sadri said that WiGig is likely to be more successful than WirelessHD for A/V applications, because it can leverage the economies of scale and broad industry support behind Wi-Fi. Wi-Fi is already built into billions of devices, he said, including PCs, hard drives, printers, and even Secure Digital cards. WiGig is likely to leverage this momentum to quickly become the dominant 60-GHz standard.
But don't rule out WirelessHD just yet, cautions John LeMonchek, president and CEO of SiBeam, one of the founders of the WirelessHD Consortium. WirelessHD is already shipping, and the prices have rapidly dropped over the past year from US$500 initially to about $300 for a pair of connectors. The technology is also built into TV sets from Visio sold at discount stores such as Wal-Mart and Costco. SiBeam, which has developed 60-GHz CMOS chips for both WiGig and WirelessHD, expects to leverage the economies of scale across both technologies.
The IEEE has already standardized the physical layer protocol underlying WirelessHD as IEEE 802.15.3c, and products are shipping. Furthermore, it's likely to offer an advantage in terms of transmission because of the differences between A/V communications and IP networking.
"The philosophy of IP networking is 'Better late than never,'" said LeMonchek. "But in the video world, 'Better never than late' provides a more satisfactory experience." In other words, consumers are happier to suffer a little bit of static than to have the whole TV show pause as the network tries to catch up with the transmission.
Furthermore, WirelessHD promises to scale up to even faster data rates from 7 Gbps today to 28 Gbps in the future by bonding multiple channels together and using more sophisticated encoding methods such as orthogonal frequency division multiplexing. With these improvements, entertainment equipment can scale up to support 4,000 lines of resolution at 480 Hz, compared with 1,080 lines at 60 Hz today.
However, these higher speeds come at an increased power cost for WirelessHD. Experts differ in their estimates: on the order of 1-2 W, according to LeMonchek, and 15-20 W, according to Sadri. LeMonchek said that this power cost will limit WirelessHD’s use to stationary devices, although advances in antenna and transmitter technology might eventually let it work in mobile devices as well. “I think that it’s tough to make one communications standard that’s good for everything,” he said, noting the separate Ethernet and USB jacks on a PC.
Both WiGig and WirelessHD approaches must compete with WHDI, which is compatible with the existing physical layer used in 2.4- and 5-GHz Wi-Fi and has taken 70 percent of the wireless A/V market, according to Les Chard, WHDI chair. Chard noted that future chips will be able to leverage the existing Wi-Fi radios, while WiGig will require a separate radio chip to support the novel 60-GHz radio.
WiGig proponents expect the technology to find its first and larger market in devices such as printers, hard drives, and laptops. Mathias sees WiGig playing an auxiliary role to the more robust, longer-range capabilities of IEEE 802.11n, which is likely to be the business workhorse, he said.
Sadri sees the WiGig specification leveraging the momentum of Wi-Fi to become the dominant low-cost, high-speed technology across networking, I/O, and A/V applications. The economies of scale will drive the cost of 60-GHz WiGig chips below $10, making them cost effective to put into hundreds of millions of devices within 4 to 5 years.
George Lawton is a freelance technology writer based in Guerneville, California. Contact him at firstname.lastname@example.org.