Smarter Than Your Average Antenna
February 18, 2004
The future of Wi-Fi might not be dominated so much by fancy new specifications as it will be clever antenna technology that pushes signals past their limits.
Smart antennas, if they work half as well and deliver half the benefits vendors claim, could be the making of Wi-Fi in the next phase of the industry's evolution.
The popular vision for that next phase is ubiquitous Wi-Fi coverage, indoors and out, public and private. However, given the range, coverage and capacity characteristics of existing technology, it will be difficult to build business cases for realizing it -- no matter how low access point prices go.
With proliferation of Wi-Fi systems will come overcrowding and interference in the unlicensed bands 802.11 uses. This will make it difficult for service providers and network managers to maintain performance and service levels without adding more and more access points.
Smart antennas may be at least part of the solution.
By increasing the range of Wi-Fi systems and reducing interference between networks and within networks, smart antennas promise to reduce the number of access points needed for a given coverage area and capacity - changing the economics of deployment.
We talked recently to two purveyors of smart antenna technology.
Vivato uses its phased array antenna technology in finished Wi-Fi infrastructure products. They include a Wi-Fi Bridge/Router and a Wi-Fi Switch that integrates multiple access points, patented controller technology and a 128-element antenna array.
The switch has been on the market since last spring and has already been deployed by over 50 customers, mostly in large outdoor networks.
Motia is a fabless semiconductor company with chip-level adaptive antenna array technology. The company claims its sub-$10 Javelin "applique" product can be added to existing access point and Wi-Fi network interface card designs without significant re-engineering.
It could also be used to build after-market plug-in antenna products for Wi-Fi access points.Motia expects to have samples of the chipset by February and be shipping in volume before the end of the second quarter of 2004. Motorola <QUOTE NYSE:MOT> has already announced it plans to incorporate the Javelin product in future wireless broadband products.
Phased or adaptive array antennas of the kind used by both Vivato and Motia have been employed in radar since World War II and are also used in cellular networks. The technology aims radio signals in a long narrow beam at a specific receiver, in this case the Wi-Fi client.
It does this through electronic movement of the entire array structure, without moving any mechanical parts. In a process Vivato calls PacketSteering, its products do it on a packet-by-packet basis.
Because the beams are so narrow, they are less visible to radiating interference. They are also only powered when needed -- when a packet is being sent in a given direction -- which further reduces the likelihood of interference.
Vivato CEO Donald Stalter says deploying his company's antenna technology typically reduces the requirement for access points to cover a given area by a factor of 3:1.
"In hotels where we use the bridge-router, what we're finding is that on a typical floor with thirty rooms, we're essentially able to provide coverage with one access point versus three of a well known competitor's," Stalter says. The Vivato products are also less expensive than some conventional access points, he notes.
In outdoor settings, where the switch technology makes most sense, the performance improvement is even more dramatic, increasing range from hundreds of meters to kilometers. It also provides more even coverage with fewer dead spots.
In a somewhat artificial test, in an open flat area, the phased array antenna was able to increase the coverage area over a conventional omni-directional antenna from 20 million to 119 million square meters, Stalter says.
The economic benefit Vivato claims for the switch in particular comes partly from the efficiencies of putting multiple access points in one array.
In the case of a cargo port of over four million square feet, the customer came down to a choice between a single tower with a Vivato switch or 19 towers with conventional access points.
"The difference in cost was $692,000 versus $92,000 with our [product]," says Stalter. "And most of that $92,000 was the tower for the infrastructure."