Vivato claims their PacketSteering technology will… “change the ‘physics’ and economics of wireless networking.”
The Wi-Fi compatible product uses phased-array antennas for a reported range of 2,000 feet inside, and about four miles outdoors. Unwiring a college campus might require putting “hot spots” into every building and cost several hundred thousand dollars.
Vivato could provide the same coverage with two or three “switches”.
The Bay Area Wireless User Group held their meeting at Vivato headquarters and have a video of the meeting here.
Vivato’s innovative “Wi-Fi Switch” is making waves. The indoor (model 2310) unit sounds like it will cost something like $5K-10K. The array, about the size of a plasma flat screen, has about 20 omnis. Each has their own rf front end. The unit starts with an 8dB gain and a 110 degree field of view. Wi-Fi beams to ordinary 802.11b clients up to 4 miles away. I gather a Texas Instruments DSP chip takes the rf field and effects a delay in the antenna feeds, which create the scanning beam that can “lock” on a moving target. A beam scans through the field and can handle multiple users. Additional beams (the first units have 3), can handle more simultaneous users.
The DP 2330 outdoor switch will sell for $50,000 and deliver 100Mbps to a community. Prices and products won’t be firmed up until Q1, 2003. Both switches can utilize any of the three common Wi-Fi standards a client is likely to have; 802.11b, 802.11a, or 802.11g. The Spokesman-Review has a backgrounder on the people and the company.
Combining gigabit Ethernet switching, Wi-Fi and smart antenna design, Vivato’s Wi-Fi switches send and receive multiple transmissions simultaneously. The phased-array radio antennas create highly directed, narrow beams, created on a packet-by-packet basis. Vivato calls this technology PacketSteering.
“We have a scanning function that tracks the clients in the area, keeping track of where they are, and then we point beams at each client,” says Phil Berlanger, VP of marketing. “You essentially have multiple parallel Wi-Fi networks operating through the same switch.”
Vivato claims their PacketSteering will reduce the cost of campus-wide Wi-Fi networks. In a recent demo, Vivato employees demonstrated working wireless coverage inside a five-story building in San Francisco from a single base station across the street. SlashDot has more while Paul Boutin, the “Wired” writer, adds that Vivato’s focus is on maximal coverage from a single base station, not long-distance wireless. Free space losses and timeouts limit the distance over which a Wi-Fi connection will work.
“I took my own iPaq with a Cisco Aironet card, stood on the top floor of the Marriot in San Francisco, about 20 feet back from the window, and connected and downloaded my e-mail and their panel was a mile away,” said Gary Berzack, CEO of Tribeca Technologies in New York.
Wi-Fi switching is said to be an attractive option for last-mile broadband delivery in metropolitan or suburban areas. Inside an enterprise, a single Wi-Fi switch can cover an entire floor or, if deployed outside, one switch can cover an entire building or campus. As compared to the tens of conventional access points it would take to cover the same area, Wi-Fi switches simplify deployment and management and lower total cost of ownership.
| How a phased array antenna works | |
Case 1: no time delay: El1 < ) ) | El2 < ) ) | El3 < ) ) | ----------> El4 < ) ) | beam direction El5 < ) ) |The wave front is in parallel to the array face. | Case 2: with time delay (Element 5 transmits first): El5 < ) ) El4 < ) ) ) El3 <) ) ) / El2 < ) ) / El1 < ) ) / ) /The wave front is at an angle to the array face. |
How do they do it? Smart antennas first monitor signals received from the subscriber unit to determine the characteristics of the environment and then generate a complementary signal.
Vivato’s switches include a planar phased array antennas built into a flat panel with integrated management and security. Three levels of security will be provided: state of the art Wi-Fi encryption and authentication, virtual private networks and a unique rogue access point detector.
Developing a low-cost phased array has long been the holy grail of antenna designers because of its small size and its ability to focus energy on the strongest signal without physically repositioning the antenna.
E-tenna’s embedded 2.4GHz WLAN antennas are on chips (right) and use an RF mirror artificial magnetic conductor that “helps better control RF energy and isolate antennas from nearby influences”. Their ClearLink 5800, provides tri-band coverage of 2.4 GHz band (with Bluetooth and 802.11b), as well as the 5.2 through 5.8 GHz band.
E-tenna’s FlexScan, which Vivato may (or may not) be utilizing, features a variable delay line (VDL) to a feed forward amplifier that causes the beam to shift. A range of broadband wireless applications below 10 GHz, from WISP 802.11 systems and Multichannel Multipoint Distribution Service (MMDS) to licensed broadband and satellite wireless systems can use them.
These phased array systems have been testing in the field for some time. The difference is that Vivato is trying to use the unlicensed band to “beam” Wi-Fi to standard IEEE 802.11 client cards. It has the potential of lowering costs if unlicensed 2.4 & 5 GHz Wi-Fi radios can be used. A big if. Will 802.16a incorporate phased array antenna options for metropolitan area wireless networks? Whether Vivato will be compatible with the 802.16a standard remains to be seen.
Compatibilty with 802.11a/b/g has got to be considered the brass ring for metro-wide wireless. And phased arrays seem like the way to go.
Cellular carriers might prefer low-range Wi-Fi. E-tenna and Ashvattha’s family of RF chips can combine 2.5/3G with Wi-Fi in cellular/PDA handset. Roam with cellular, surf with Wi-Fi. Put off the expense of 3G. Cellular companies can’t conceive that any unlicensed or MMDS could provide legitimate competition. They are misinformed.
Smart Antennas are nothing new. Annie Lindstrom has the definitive article on Phased Array Antennas used in Wireless Broadband. They’re everywhere in the latest proposed “4G” systems. They can be incorporated in the transmitter, receiver or both. They are different from ordinary diversity antennas seen on many access points.
“A diversity antenna system can be compared to a switch that selects one antenna or another, never both at the same time. The radio in receive mode will continually switch between antennas listening for a valid radio packet. After the beginning sync of a valid packet is heard, the radio will evaluate the sync signal of the packet, on one antenna, then switch to the other antenna and evaluate. Then the radio will select the best antenna, and use only that antenna for the remaining portion of that packet.
“On transmit, the radio will select the same antenna it used the last time it communicated to that given radio. If a packet fails, it will switch to the other antenna and retry the packet.
Paratek’s DRWiN (right), is an electronically scanning WLAN antenna for indoor or outdoor Wi-Fi (and GSM) applications. Skycross has a line of innovative, low-profile antennas that work in both cell phones and Wi-Fi devices.
Perhaps the most innovative are Fractal Antennas, like those made by Fractal Antenna Systems. They are said to be 25 percent more efficient than the rubbery “stubby” found on most phones. In addition, they are cheaper to manufacture, operate on multiple bands–allowing, for example, a Global Positioning System receiver to be built into the phone–and can be tucked inside the phone body.
“4G” systems that incorporate phased array antennas include ArrayComm, Beam Reach, Flarion and Navini.
“The hype said that UMTS would give users 2Mbps channels, but the truth is that it has 1.1Mbps channels, which must be shared by people to be economic. It also needs a reasonable number of base stations. In practice users will get about 80kbps, at a much greater cost than GPRS, which currently gives 50 to 60kbps.”
3G representives, told ZDNet UK, that 3G would improve with time, but did not dispute the figures Cooper quoted.
Arraycomm uses “smart” antennas that offer users higher bandwidths than 3G by reusing the same frequencies in a manner that appears to be similar to Vivato.
|
Parameter
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Broadband CDMA
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Switched Beam Antenna
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MIMO
|
|
|
System Capacity
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Highest
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Lowest
|
Medium
|
Medium
|
|
Spectral Efficiency |
>10 bits/s/Hz/cell
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<0.7 bits/s/Hz/cell
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2-4 bits/s/Hz/cell
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2-4 bits/s/Hz/cell
|
|
Cell Size
|
Large
|
Small
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Medium
|
Medium
|
|
Indoor Customer Install
|
Yes
|
Yes
|
No
|
No
|
It’s tempting to plug new business models into community wireless networks. Imagine a fiber ring feeding Switchpoint Network hubs. They connect 100 Mbps direct to homes or to “smart arrays” on utility poles for mobility. Wireless 10 MBps can deliver movies on demand. Cable can’t.
Alan Reiter says Sprint will likely be entering the Wi-Fi “hot spot” business. They have an investment in Boingo Wireless. But how will those Boingo boxes be fed? Sprint, which has MMDS licenses throughout the United States, has been testing both Navini Networks, a proprietary CDMA system and IP Wireless, Time Division MMDS/PCS system similar to 3G UMTS (using a single channel rather than duplex). But Sprint might find competitive advantage if they could deliver 802.11 direct to the end user.
Phased Arrays in 802.16a
Iospan’s multiple antenna enhancements of the OFDM modulation technique are being standardized in the IEEE 802.16 Working Group on Broadband Wireless Access Standards. The company is aiming the price of customer premises equipment at less than $500, and has begun trial deployments with partners in the United States. Designing MIMO systems for non-LOS wireless broadband may be key to competitive broadband. A 2 x 3 (MIMO) (2 antennas at the Tx, three at Rx), enjoys a 17 dB multipath fade margin advantage compared with SISO and a 10 dB multipath fade margin advantage compared with 1 x 2 antennas. A 15 dB boost more than quadruples the coverage area. BeamReach teamed up with Proxim for localized 802.11 products; Filanet for advanced security; and Mediatrix for voice over IP (VOIP) solutions.
Time will tell how Sprint and the rest of the cellular carriers will get into Wi-Fi hot spots. But jump they will. Nearly ALL laptops and PDAs are soon going to have built-in Wi-Fi. Cellular carriers WILL loose market share without a Wi-Fi connection.
Mesh networking is another approach to increase the range of Wi-Fi networks. Users communicate through neighboring nodes when a direct internet link is impossible. Localized mesh networking might be combined with fixed wireless backbones like Aperto Networks, BreezeNET, IO Span and Wavesat. Local mesh networks include Nokia Rooftop, Locustworld, SkyPilot and Mesh Networks. Mesh networking routes the signal along the next best “hot spot” of opportunity. Several relay “hops” can be made to route the signal to a landline conection.
Roam AD, in Auckland New Zealand is “unwiring” the downtown core, using a “meshed star” approach. They use wireless for the backhaul. Connections are handed from one radio point to another for continuous coverage. It’s fully compatible with 802.11b and is said to be 5% of the cost of a 3G network.
The company has deployed a three-square kilometre demonstration network in Auckland with a metro-wide, 100 square kilometre, planned. Field testing will show how far they can run with it.
The advantage of phased arrays is coverage can extend further from a single “hot spot” because energy is focused. Roaming and handoff are significantly reduced. That’s a BIG feature. Wi-Fi’s limited 300 foot range make handoff overhead a costly problem.
Wi-Fi repeaters, on the other hand, are simpler. They just re-amplify and mirror a weak signal. They can effectively double “hot spot” range (although the throughput is effective halved).
Off-the-shelf directional flat panels can extend Wi-Fi range - but they can’t dynamically change their coverage pattern.
A satellite alternative might be available from an autonomous aircraft like SkyTower. Flying in 2,000-foot-wide circles and using solar power, each Helios plane might deliver broadband to anyone inside a 50-mile radius. A 60 GHz backhaul might link to the ground network. Too bad it was designed to fly at 60,000 feet.
Maybe a $100 client phased array…
