COLORADO SPRINGS, Colo. — When the IEEE first pondered antenna diversity for its 802.11n wireless LAN standard, the multiple-input/multiple-output antenna topology was seen as a general tool for increasing Internet data access to 500 Mbits/second--some 50 times that of 802.11b. But as draft silicon of 802.1n networks sampled in 2006, the focus had changed to a singular concentration on Internet Protocol TV (IPTV) and high-definition television video streams.
In a sense, the metamorphosis of 802.11n mirrors that of a shorter-range wireless technology, ultrawideband radio. After the IEEE 802.15.3a task group on UWB split up in acrimony last January, the promotional WiMedia Alliance group narrowed its focus to applications in which ultrawideband is a wireless replacement for the Universal Serial Bus. But more recently, "Certified Wireless USB" has taken a back seat to chip sets exploiting ultrawideband for in-home video distribution.
The two technologies are complementary. Since 802.11n must serve first duty as an access technology to broadband pipes, its hub-and-spoke LAN structure is designed for networking first. UWB, except when in the multipoint WiNet topology, is a serial file-sharing PAN with shorter range, but with data rates that can approach and sometimes exceed 1 Gbit/s. Both local- and personal-area networks are being optimized for video distribution in the home.
Some WLAN chip set developers even hope to repurpose OFDM media-access control and physical-layer chips, along with 4 x 5 antenna solutions, as a direct High Definition Multimedia Interface (HDMI) cable replacement. Amimon Inc. will demonstrate prototypes of this solution at next week's Consumer Electronics Show. Metalink has taken a slightly more conventional approach, using its WLANPlus chip set with enhanced quality-of-service (QoS) as a vehicle to improving HDTV distribution in the home, though not necessarily as an HDMI substitute.
For HDTV networks based on MIMO antennas, even the lower-speed 802.11b/g plays a role. In late 2005, Ruckus Networks Inc. went public with a MIMO-based access point that used 802.11b/g for video distribution in the home. In 2006, Ruckus extended its work with a residential gateway, and intends to upgrade its antenna diversity architecture for 802.11n support.
Ruckus' two proprietary concepts indicate where newcomer OEMs can add functionality with the first generation of 802.11n chips. Instead of relying solely on antenna spatial diversity, Ruckus adds beam-forming algorithms to adaptively choose the best RF paths in the home. It then adds routing-layer multicasting diversity, dubbed SmartCast, to make the best use of IPTV multicasting. In theory, combining MIMO and routing concepts in a new generation of 802.11n gateways will allow fast Internet Group Membership Protocol add and join operations, essential for fast "channel changing" in IPTV.
Broadcom Corp. and Atheros Communications Inc. raised eyebrows last January when they offered "draft" silicon for 802.11n, even though by year's end the IEEE working group had yet to finalize this standard. Almost as surprising as the early silicon for 802.11n was the fact that they emphasized consumer, rather than enterprise, applications on their Web sites.
