The WiGig Alliance is moving full steam ahead with its plan to enable devices to communicate wirelessly at mulit-gigabit speeds using unlicensed 60GHz spectrum. WiGig Alliance President and Chairman Dr. Ali Sadri sat down with Ars at CES to explain where WiGig fits among various wireless standards, and when we can expect the technology to become widely implemented.
The WiGig MAC specification was published in June 2011, and the standard is currently in draft stage with the IEEE as 802.11ad. WiGig operates on unlicensed 60GHz spectrum; it won't propagate through walls and has a range of about 10 meters. As such, isn't necessarily meant as a replacement for 2.4GHz or 5GHz WiFi. However, operating at 60GHz offers advantages in terms of power consumption and data rates, particularly for mobile devices.
"The wavelength at 60GHz is about 5mm, and antenna elements are half a wavelength, so we're talking roughly 2.5mm," Dr. Sadri told Ars. "When you compare antenna elements for Wi-Fi, those are 5cm versus 2.5mm. So I can actually, in the same device, put multiple 2.5mm antenna elements for the same one antenna for Wi-Fi. I can get a lot of gain from the 60GHz antenna, which allows me to do beam forming—I can direct transmission in a specific direction," he explained.
WiGig also uses time division multiplexing, so a device can transmit multiple data streams to different devices, each in a specific direction using a specific time slot. To get an idea of how this works, imagine a WiGig-enabled smartphone sends a video stream to three WiGig-enabled displays in the same room. In the first time slot, it sends a chunk of the video stream to the first display. In the second time slot, it sends a chunk of the video stream to the second display. Then, in the third time slot, a chunk is sent to the third display. The next slot will transmit more video data to display 1, then next to display 2, then display 3, etc.
The combination of TDMA and directional transmission offers significant power savings, particularly important for mobile devices. WiGig has 2GHz of bandwidth per channel, which allows simpler modulation techniques, which in turn saves power. WiGig's multiple antennas also have significant gain, requiring fewer radio elements and conserving more power.
"If Wi-Fi wants to get to 2Gbps, you need at least 3x3 antennas, and much wider bandwidth, maybe consuming 3 watts," Sadri said. "2Gbps using WiGig in a handheld device will consume about 500 to 600 milliwatts. That's five times the efficiency of Wi-Fi."
Trying to shoehorn such a configuration into a handheld device would also be physically limiting. "You cannot imagine in handheld devices having three or four 5cm antennas; maximum one, or maybe two if you are lucky," Sadri explained. "But you could certainly have multiple arrays of 2.5mm 60GHz antennas, giving you 2Gbps."
WiGig also presents a protocol-agnostic transport layer to send data between devices. So USB, HDMI, DisplayPort, PCI Express protocols can be used to communicate with various peripherals. One scenario where this could be useful is completely wireless "docking" between a tablet and an external display, keyboard, and mouse. Imagine having a tablet that, while at home, operates like a traditional desktop. On the go, however, it works like a touchscreen tablet. Take it to work, and you could again "dock" the device with peripherals in your office.
