It’s almost impossible to keep up with the twists and turns in the wireless home network market, and particularly the fight to achieve a universal standard for high speed, short range connections geared to multimedia and HDTV. With the original frontrunner, UltraWideBand-based WiMedia, now consigned to Wireless USB, other UWB solutions have fallen out of favor, at least for now. This has left three main contenders ‘ WiGig and WHDI, both based, at least loosely, on Wi-Fi; and WirelessHD, which uses technology from SiBeam and the 60GHz band. There is also the wild card of the recently ratified IEEE 802.15.3c standard, also for 60GHz and also using SiBeam designs, though focused on different applications to WirelessHD. Last month, WHDI looked to be going the same way as WiMedia, as Sony defected to WirelessHD, but undeterred, the WHDI Consortium has completed its specifications and claims it still has a strong chance of gaining support among the consumer electronics and mobile communities.
When Sony dropped WHDI for new products in favor of WirelessHD, the main technology supplier in the platform, Amimon, decided to supplement its business by focusing on the sale of its IP to Wi-Fi companies. This seemed to be just another indicator that Wi-Fi was winning the home network war ‘ and indeed, WHDI itself builds heavily on a 5GHz 802.11 base. Although 5GHz supports commoditized chips and devices, and longer ranges, it is somewhat out of fashion, with the WPAN world heavily focused for now on 60GHz. The emergence of chip technologies that enable low cost devices for this band has focused intense interest on, with WiGig as well as WirelessHD working here.
Despite swimming against the tide, the WHDI Consortium has completed its specs for wireless video over Amimon’s Wi-Fi like technology. These promise to carry high definition video at 1080p resolution, 60Hz refresh rates and 12-bit color depth, over distances of up to 100 feet and through multiple walls, with peak data rates of 3Gbps in wide 40MHz channels. These specs go beyond the original Amimon platform, which was limited to 720p video, and WHDI now supports release 2.0 of the High Bandwidth Digital Content Protection (HDCP) standard, as well as enhancing multiroom operation with support for the Consumer Electronics Control protocol, part of the HDMI platform. This shows WHDI coming closer to WirelessHD in functionality ‘ the main focus for the rival standard, which has greater support among CE vendors so far, is wireless HDMI, while other technologies like 802.15.3c and even WiGig are likely to push down into mobile devices too.
The latest WHDI specs are available only to consortium members, which still include Sony, along with LG, Hitachi, Sharp, Motorola and Samsung. The group aims to have an interoperability test suite and certification lab in place by next fall. “We’re not expecting first products using the technology until the third quarter or so,’ said a spokesperson, looking on the bright side of a year-long delay in releasing a set of specs that was originally expected at the end of 2008. The consortium was formed in July 2008, promising to build on some of the advances made to Wi-Fi in the 802.11n high speed standard, notably MIMO antenna arrays and 40MHz channels. It also drew on more unusual features of the Amimon approach, including a system that begins with barely compressed video, using a lossless compression standard that halves the signal requirement for wireless transmission, when compared to uncompressed video. It then divides the data stream between those bits that are more important for quality video rendering, and those which are less important. WHDI’s Joint Source-Channel Coding technique first prioritizes video components, then applies two separate error correction schemes to the outcome, encoding the most significant bits within the important video components using better error correcting code.
All this makes WHDI more robust and efficient for video than vanilla Wi-Fi or even, its supporters claim, WiGig, which runs Wi-Fi at very high throughput in 60GHz. However, the common features between WHDI and 802.11n suggest that the system may survive by working more closely with the mainstream Wi-Fi community in 5GHz, to put the two technologies through similar channels, rather than antagonizing it. This could lead to a stand-off between 5GHz and 60GHz approaches, which is partly an issue of range versus data rate and may depend on the type of device and application involved. Craig Mathias, principal of research group Farpoint Group, told EETimes that it will become more acceptable to compress video running between devices in the home, given that cable TV is already heavily compressed, and this could reduce WHDI’s appeal. “I think it will come down to whether compression is undesirable or not and therefore is straight Wi-Fi enough?’ he commented. Several companies are working on adapting standard 802.11n for HD video, usually with clever use of 4×4 MIMO and compression ‘ these include Quantenna and Qualcomm, which announced its N-Stream 4×4 chipset for this market in June, leveraging technology it acquired three years ago with Airgo. Atheros is also pushing further into this space using MIMO.