Overview
What is WHDI™?
WHDI™ (Wireless Home Digital Interface) sets a new standard for wireless high-definition video connectivity. It provides a high-quality, uncompressed wireless link which can support delivery of equivalent video data rates of up to 3Gbps (including uncompressed 1080p) in a 40MHz channel in the 5GHz unlicensed band, conforming to worldwide 5GHz spectrum regulations. Range is beyond 100 feet, through walls, and latency is less than one millisecond.
WHDI enables new opportunities for consumers to connect their A/V devices and to consume content. With a range that spans the whole home, WHDI allows users to connect any source in the home to any display. With WHDI, the TV in the living room can show movies from the Blu-Ray player in the bedroom, the kitchen TV can display the contents of the PC in the home office, and a game can be enjoyed on the basement projector without moving the gaming console from the kids' bedroom. This is the first standard to enable universal, codec-independent, multi-room HD video connectivity through the delivery of uncompressed HD video using a revolutionary video modem approach that supports whole home coverage.
WHDI specifies the transmission of HD video as well as audio and control. A comprehensive WHDI control protocol will allow users to control their A/V devices from any point in the home. With practically no latency, users can play video games using the WHDI link and route the video and audio separately without the risk of encountering lip-sync issues.
Support for Uncompressed Video
WHDI enables a wireless video link that offers the same functionality, cost and quality as a wired link. Practically all of the hundreds of millions of wired connections between video sources and displays today are based on delivery of uncompressed video. In order to provide a similar user experience as with wired connections, the wireless interface needs to be uncompressed as well.
Solutions that are based on delivery of compressed video do not solve the problem of providing a universal wireless video link that can connect between any source and any display. Although most of the digital sources are distributed to the home in compressed format, compressed video is rarely provided at the output of most video sources such as DVD players and set-top-boxes. One reason for this is copy-protection: compressed outputs are more susceptible and more sensitive to theft. Another reason is that interoperability on the compressed level is extremely challenging due to the multitude of video codecs, and displays cannot be expected to support all of them. Moreover, there are many sources that are generated uncompressed, such as gaming consoles and PCs.
Previous solutions tried to overcome this constraint by applying real-time compression to the uncompressed outputs of sources. However, this significantly reduces quality, adds latency, and is expensive.
Revolutionary Video-Modem Technology
Enabling the wireless delivery of such high video rates is a radically different approach to transmission. WHDI is based on a revolutionary video-modem technology invented by AMIMON in which the video coding and modulation are jointly optimized to enable capabilities far beyond those of traditional wireless modems that have been optimized for data.
Traditional wireless video approaches have failed to provide an adequate solution to the problem of wireless HDTV connectivity because they treat the problem as a special case of data delivery. In a wireless data modem (e.g. 802.11n, MBOA-UWB) all bits are treated equally - they all get the same level of protection from channel impairments. However, in video, different bits have different levels of importance, and the effect of an error greatly depends on which bit was corrupted.
For example: A typical uncompressed stream is represented by a stream of 8 or 10 bit numbers, each representing the primary color value of a given pixel. Clearly, the most significant bit (MSB) of each of these numbers has greater visual importance than the least significant bit (LSB). If an error occurs on the MSB, that pixel gets an entirely different (and unwanted) value. However, an error in the LSB will result in a minor change in the pixel's value. Wireless data-modems ignore this characteristic of video. They provide the same level of protection to the MSB and LSB, which means they either protect the LSB too much, resulting in inefficient use of channel capacity, or protect the MSB too little, resulting is a low quality video link; or a combination of both. WHDI provides a different level of protection to the different bits, enabling the delivery of very high video rates with very high quality.
WHDI takes the uncompressed HD video stream and breaks it into elements of importance. The various elements are then mapped onto the wireless channel in a way that give elements with more visual importance a greater share of the channel resources, i.e. they are transmitted in a more robust manner. Elements that have less visual importance are allocated fewer channel resources, and therefore are transmitted in a less robust way. Allocation of channel resources can include, for example, setting power levels, spectrum allocation and coding parameters.
The result of this unique video-modem approach is that any errors in the wireless channel are not noticed as they only affect the less important bits. Very high rates of video information can be transmitted because the human eye can tolerate the errors that fall on the less important bits.
