Wireless HDMI: Explaining the Different Options
By Adrienne Maxwell
A couple of years ago, wireless HDMI seemed poised to be the hot, new technology that would sweep quickly through the A/V industry. A number of technologies emerged that allowed for the wireless transmission of a high-definition video signal from source to display, eliminating the need for a physical HDMI cable. Adoption of this technology has been slower than expected, perhaps due to the price premium it has demanded thus far; nevertheless, wireless HDMI is slowly making its presence felt, appearing last year in a number of higher-end TVs and a few standalone adapter products. At this stage in the game, the field has narrowed to three wireless HD technologies: Ultra-wideband (UWB), WirelessHD (WiHD), and Wireless High Definition Interface (WHDI). Each technology operates in a different frequency band, and each is capable of a different data rate, which affects its handling of high-definition video (namely, whether or not compression is involved).
It's important to distinguish wireless HDMI from wireless video streaming. Several TV manufacturers are starting to incorporate 802.11n WiFi capability into their TVs, which allows you to stream HD video content wirelessly from network/Web sources to the TV. However, in this article, we're talking specifically about the wireless transmission of the HDMI video signal from source to display. This requires a transmitter unit that connects to the HDMI output on your source components and a receiver unit that is either integrated into the TV chassis or packaged as an add-on adapter that connects to the TV's HDMI input.
Ultra-wideband (UWB)
UWB is an RF technology in which bursts of information are sent over a wider frequency range, from 3.1 to 10.6 GHz. Because the transmission is not limited to a specific or narrow frequency band, the signal is less susceptible to interference. Ultra-wideband technology is a short-range, in-room solution: It's best suited for line-of-sight communication between the transmitter and receiver at a distance of around 30 feet. The technology is theoretically capable of speeds up to 480 Mbps, which is still not fast enough to accommodate high-definition video signals that require 1.3 Gbps or higher; therefore, UWB demands the use of compression in order to accommodate a video signal from 720p up to 1080p.
Early on, UWB appeared to have advantage and momentum in the wireless HDMI race, but it has lost steam with major A/V manufacturers, due to the emergence of technologies that don't require compression. Gefen is one of the few companies that's currently selling standalone wireless HDMI products, one of which is based on UWB technology: The Wireless for HDMI UWB Extender (EXT-WHDMI) supports video signals up to 1080p/30, as well as multichannel audio. UWB also has application in the computer and mobile electronics fields. At CES 2010, Alereon showed off its NoWire Laptop to HDTV Extender technology, which lets you transmit 720p video and audio wirelessly to your HDTV via a USB dongle. Atlona offers a similar wireless PC-to-TV kit, the AT-HDAIR.
WirelessHD (WiHD)
Another technology designed for short-range, in-room solutions, WirelessHD can transmit uncompressed HD video at a distance of about 30 feet, using smart-antenna technology to improve reliability and lessen the need for line-of-sight between transmitter and receiver. Developed by a company called SiBEAM, WirelessHD operates in the 60GHz band and offers a data rate up to 4 Gbps in its current form, which allows for the transmission of HD resolutions up to 1080p/60. The recently updated WirelessHD spec supports a data rate from 10 to 28 Gbps, allowing for the wireless transmission of 3D content and sources with a 4K resolution.
Panasonic's current Z1 Series of plasma HDTVs uses WirelessHD, as do LG's LH85 and LHX models. At CES 2010, Panasonic, Vizio, and Toshiba showed off new 3D-capable HDTVs that employ WirelessHD, and Gefen recently released a Wireless for HDMI 60Hz adapter kit (GTV-WIRELESSHD) that supports 1080p/60 and eight-channel 24/192 audio signals.
Wireless High Definition Interface (WHDI)
WHDI, which was developed by a company called Amimon, operates in the 5GHz frequency band and has a data rate of up to 3 Gbps in a 40-MHz channel. Obviously, the potential data rate is not as high as that of WirelessHD, but it is high enough to support uncompressed 1080p/60 video and multichannel audio. While WHDI does not employ compression, it does prioritize the signal information and apply better encoding to more important bits, as opposed to treating all bits equally. Perhaps WHDI's strongest attribute is its range: The technology works through walls and other boundaries up to about 100 feet, which makes it the only option for wireless multiroom video distribution.
There are a couple of products currently on the market that use WHDI. Sony's DMX-WL1 BRAVIA Wireless Link Module, designed for use with compatible Sony HDTVs, is based on WHDI, but it only supports up to a 1080i resolution and is no longer sold through Sony's website. Once again, Gefen offers a model based on WHDI technology; the Wireless for HDMI 5GHz kit (GTW-WHDMI) is a good multiroom solution, but it only transmits up to 1080p/30, so it's not a great fit for older HDTVs and first-generation Blu-ray players that only support 1080p at 60 frames per second. At CES, LG announced that many of its 2010 TVs will be wireless-ready, with optional transmitter/receiver kits that use WHDI technology and support a full 1080p/60 resolution.
