Posts Tagged ‘802.11ac’

802.11ac ‘gigabit Wi-Fi’ starts to show potential, limits

Monday, October 7th, 2013

Vendor tests and very early 802.11ac customers provide a reality check on “gigabit Wi-Fi” but also confirm much of its promise.

Vendors have been testing their 11ac products for months, yielding data that show how 11ac performs and what variables can affect performance. Some of the tests are under ideal laboratory-style conditions; others involve actual or simulated production networks. Among the results: consistent 400M to 800Mbps throughput for 11ac clients in best-case situations, higher throughput as range increases compared to 11n, more clients serviced by each access point, and a boost in performance for existing 11n clients.

Wireless LAN vendors are stepping up product introductions, and all of them are coming out with products, among them Aerohive, Aruba Networks, Cisco (including its Meraki cloud-based offering), Meru, Motorola Solutions, Ruckus, Ubiquiti, and Xirrus.

The IEEE 802.11ac standard does several things to triple the throughput of 11n. It builds on some of the technologies introduced in 802.11n; makes mandatory some 11n options; offers several ways to dramatically boost Wi-Fi throughput; and works solely in the under-used 5GHz band.

It’s a potent combination. “We are seeing over 800Mbps on the new Apple 11ac-equipped Macbook Air laptops, and 400Mbps on the 11ac phones, such as the new Samsung Galaxy S4, that [currently] make up the bulk of 11ac devices on campus,” says Mike Davis, systems programmer, University of Delaware, Newark, Delaware.

A long-time Aruba Networks WLAN customer, the university has installed 3,700 of Aruba’s new 11ac access points on campus this summer, in a new engineering building, two new dorms, and some large auditoriums. Currently, there are on average about 80 11ac clients online with a peak of 100, out of some 24,000 Wi-Fi clients on campus.

The 11ac network seems to bear up under load. “In a limited test with an 11ac Macbook Air, I was able to sustain 400Mbps on an 11ac access point that was loaded with over 120 clients at the time,” says Davis. Not all of the clients were “data hungry,” but the results showed “that the new 11ac access points could still supply better-than-11n data rates while servicing more clients than before,” Davis says.

The maximum data rates for 11ac are highly dependent on several variables. One is whether the 11ac radios are using 80 Mhz-wide channels (11n got much of its throughput boost by being able to use 40 MHz channels). Another is whether the radios are able to use the 256 QAM modulation scheme, compared to the 64 QAM for 11n. Both of these depend on how close the 11ac clients are to the access point. Too far, and the radios “step down” to narrower channels and lower modulations.

Another variable is the number of “spatial streams,” a technology introduced with 11n, supported by the client and access point radios. Chart #1, “802.11ac performance based on spatial streams,” shows the download throughput performance.

802.11ac

In perfect conditions, close to the access point, a three-stream 11ac radio can achieve the maximum raw data rate of 1.3Gbps. But no users will actually realize that in terms of useable throughput.

“Typically, if the client is close to the access point, you can expect to lose about 40% of the overall raw bit rate due to protocol overhead – acknowledgements, setup, beaconing and so on,” says Mathew Gast, director of product management, for Aerohive Networks, which just announced its first 11ac products, the AP370 and AP390. Aerohive incorporates controller functions in a distributed access point architecture and provides a cloud-based management interface for IT groups.

“A single [11ac] client that’s very close to the access point in ideal conditions gets very good speed,” says Gast. “But that doesn’t reflect reality: you have electronic ‘noise,’ multiple contending clients, the presence of 11n clients. In some cases, the [11ac] speeds might not be much higher than 11n.”

A third key variable is the number of spatial streams, supported by both access points and clients. Most of the new 11ac access points will support three streams, usually with three transmit and three receive antennas. But clients will vary. At the University of Delaware, the new Macbook Air laptops support two streams; but the new Samsung Galaxy S4 and HTC One phones support one stream, via Broadcom’s BCM4335 11ac chipset.

Tests by Broadcom found that a single 11n data stream over a 40 MHz channel can deliver up to 60Mbps. By comparison, single-stream 11ac in an 80 MHz channels is “starting at well over 250Mbps,” says Chris Brown, director of business development for Broadcom’s wireless connectivity unit. Single-stream 11ac will max out at about 433Mbps.

There are some interesting results from these qualities. One is that the throughput at any given distance from the access point is much better in 11ac compared to 11n. “Even at 60 meters, single-stream 11ac outperforms all but the 2×2 11n at 40 MHz,” Brown says.

Another result is that 11ac access points can service a larger number of clients than 11n access points.

“We have replaced several dozen 11n APs with 11ac in a high-density lecture hall, with great success,” says University of Delaware’s Mike Davis. “While we are still restricting the maximum number of clients that can associate with the new APs, we are seeing them maintain client performance even as the client counts almost double from what the previous generation APs could service.”

Other features of 11ac help to sustain these capacity gains. Transmit beam forming (TBF), which was an optional feature in 11n is mandatory and standardized in 11ac. “TBR lets you ‘concentrate’ the RF signal in a specific direction, for a specific client,” says Mark Jordan, director, technical marketing engineering, Aruba Networks. “TBF changes the phasing slightly to allow the signals to propagate at a higher effective radio power level. The result is a vastly improved throughput-over-distance.”

A second feature is low density parity check (LDPC), which is a technique to improve the sensitivity of the receiving radio, in effect giving it better “hearing.”

The impact in Wi-Fi networks will be significant. Broadcom did extensive testing in a network set up in an office building, using both 11n and 11ac access points and clients. It specifically tested 11ac data rates and throughput with beam forming and low density parity check switched off and on, according to Brown.

Tests showed that 11ac connections with both TBR and LDPC turned on, increasingly and dramatically outperformed 11n – and even 11ac with both features turned off – as the distance between client and access point increased. For example, at one test point, an 11n client achieved 32Mbps. At the same point, the 11ac client with TBR and LDPC turned “off,” achieved about the same. But when both were turned “on,” the 11ac client soared to 102Mbps, more than three times the previous throughput.

Aruba found similar results. Its single-stream Galaxy S4 smartphone reached 238Mbps TCP downstream throughput at 15 feet, 235Mbps at 30 feet, and 193Mbps at 75 feet. At 120 feet, it was still 154Mbps. For the same distances upstream the throughput rates were: 235Mbps, 230M, 168M, and 87M.

“We rechecked that several times, to make sure we were doing it right, says Aruba’s Jordan. “We knew we couldn’t get the theoretical maximums. But now, we can support today’s clients with all the data they demand. And we can do it with the certainty of such high rates-at-range that we can come close to guaranteeing a high quality [user] experience.”

There are still other implications with 11ac. Because of the much higher up and down throughput, 11ac mobile devices get on and off the Wi-Fi channel much faster compared to 11n, drawing less power from the battery. The more efficient network use will mean less “energy per bit,” and better battery life.

A related implication is that because this all happens much faster with 11ac, there’s more time for other clients to access the channel. In other words, network capacity increases by up to six times, according to Broadcom’s Brown. “That frees up time for other clients to transmit and receive,” he says.

That improvement can be used to reduce the number of access points covering a given area: in the Broadcom office test area, four Cisco 11n access points provided connectivity. A single 11n access point could replace them, says Brown.

But more likely, IT groups will optimize 11ac networks for capacity, especially as the number of smartphones, tablets, laptops and other gear are outfitted with 11ac radios.

Even 11n clients will see improvement in 11ac networks, as University of Delaware has found.

“The performance of 11n clients on the 11ac APs has probably been the biggest, unexpected benefit,” says Mike Davis. “The 11n clients still make up 80% of the total number of clients and we’ve measured two times the performance of 11n clients on the new 11ac APs over the last generation [11n] APs.”

Wi-Fi uses Ethernet’s carrier sense multiple access with collision detection (CSMA/CD) which essentially checks to see if a channel is being used, and if so, backs off, waits and tries again. “If we’re spending less time on the net, then there’s more airtime available, and so more opportunities for devices to access the media,” says Brown. “More available airtime translates into fewer collisions and backoffs. If an overburdened 11n access point is replaced with an 11ac access point, it will increase the network’s capacity.”

In Aruba’s in-house testing, a Macbook Pro laptop with a three-stream 11n radio was connected to first to the 11n Aruba AP-135, and then to the 11ac AP-225. As shown in Chart #2, “11ac will boost throughput in 11n clients,” the laptop’s performance was vastly better on the 11ac access point, especially as the range increased.

802.11ac

These improvements are part of “wave 1” 11ac. In wave 2, starting perhaps later in 2014, new features will be added to 11ac radios: support four to eight data streams, explicit transmit beam forming, an option for 160 Mhz channels, and “multi-user MIMO,” which lets the access point talk to more than one 11ac client at the same time.

Source:  networkworld.com

Next up for WiFi

Thursday, August 22nd, 2013

Transitioning from the Wi-Fi-shy financial industry, Riverside Medical Center’s CSO Erik Devine remembers his shock at the healthcare industry’s wide embrace of the technology when he joined the hospital in 2011.

“In banking, Wi-Fi was almost a no-go because everything is so overly regulated. Wireless here is almost as critical as wired,” Devine still marvels. “It’s used for connectivity to heart pumps, defibrillators, nurse voice over IP call systems, surgery robots, remote stroke consultation systems, patient/guest access and more.”

To illustrate the level of dependence the organization has on Wi-Fi, Riverside Medical Center calls codes over the PA system — much like in medical emergencies — when the network goes down. “Wireless is such a multifaceted part of the network that it’s truly a big deal,” he says.

And getting bigger. Besides the fact that organizations are finding new ways to leverage Wi-Fi, workers have tasted the freedom of wireless, have benefited from the productivity boost, and are demanding increased range and better performance, particularly now that many are showing up with their own devices (the whole bring your own device thing). The industry is responding in kind, introducing new products and technologies, including gigabit Wi-Fi (see “Getting ready for gigabit Wi-Fi“), and it is up to IT to orchestrate this new mobile symphony.

“Traffic from wireless and mobile devices will exceed traffic from wired devices by 2017,” according to the Cisco Visual Networking Index. While only about a quarter of consumer IP traffic originated from non-PC devices in 2012, non-PC devices will account for almost half of consumer IP traffic by 2017, Cisco says.

Cisco Visual Networking IndexIT gets it, says Tony Hernandez, principal in Grant Thornton’s business consulting practice. Wi-Fi is no longer an afterthought in IT build-outs. “The average office worker still might have a wired connection, but they also have the capability to use Wi-Fi across the enterprise,” says Hernandez, noting the shift has happened fast.

“Five years ago, a lot of enterprises were looking at Wi-Fi for common areas such as lobbies and cafeterias and put that traffic on an isolated segment of the network,” Hernandez says. “If users wanted access to corporate resources from wireless, they’d have to use a VPN.”

Hernandez credits several advances for Wi-Fi’s improved stature: enterprise-grade security; sophisticated, software-based controllers; and integrated network management.

Also in the mix: pressure from users who want mobility and flexibility for their corporate machines as well as the ability to access the network from their own devices, including smartphones, tablets and laptops.

Where some businesses have only recently converted to 802.11n from the not-too-distant past of 802.11a/b/g, they now have to decide if their next Wi-Fi purchases will support 802.11ac, the draft IEEE standard that addresses the need for gigabit speed. “The landscape is still 50/50 between 802.11g and 802.11n,” Hernandez says. “There are many businesses with older infrastructure that haven’t refreshed their Wi-Fi networks yet.”

What will push enterprises to move to 802.11ac? Heavier reliance on mobile access to video such as videoconferencing and video streaming, he says.

Crash of the downloads

David Heckaman, vice president of technology development at luxury hospitality chain Mandarin Oriental Hotel Group, remembers the exact moment he knew Wi-Fi had gained an equal footing with wired infrastructure in his industry.A company had booked meeting room space at one of Mandarin Oriental’s 30 global properties to launch its new mobile app and answered all the hotel’s usual questions about anticipated network capacity demands. Not yet familiar with the impact of dense mobile usage, the IT team didn’t account for the fallout when the 200-plus crowd received free Apple iPads to immediately download and launch the new app. The network crashed. “It was a slap in the face: What was good enough before wouldn’t work. This was a whole new world,” Heckaman says.

Seven to eight years ago, Wi-Fi networks were designed to address coverage and capacity wasn’t given much thought. When Mandarin Oriental opened its New York City property in 2003, for example, IT installed two or three wireless access points in a closet on each floor and used a distributed antenna to extend coverage to the whole floor. At the time, wireless only made up 10% of total network usage. As the number climbed to 40%, capacity issues cropped up, forcing IT to rethink the entire architecture.

“We didn’t really know what capacity needs were until the Apple iPhone was released,” Heckaman says. Now, although a single access point could provide signal coverage for every five rooms, the hotel is putting access points in almost every room to connect back to an on-site controller.

Heckaman’s next plan involves adding centralized Wi-Fi control from headquarters for advanced reporting and policy management. Instead of simply reporting that on-site controllers delivered a certain number of sessions and supported X amount of overall bandwidth, he would be able to evaluate in real-time actual end-device performance. “We would be able to report on the quality of the connection and make adjustments accordingly,” he says.

Where he pinpoints service degradation, he’ll refresh access points with those that are 802.11ac-enabled. As guests bring more and more devices into their rooms and individually stream movies, play games or perform other bandwidth-intensive actions, he predicts the need for 802.11ac will come faster than anticipated.

“We have to make sure that the physical link out of the building, not the guest room access point, remains the weakest point and that the overall network is robust enough to handle it,” he says.

Getting schooled on wireless

Craig Canevit, IT administrator at the University of Tennessee at Knoxville, has had many aha! moments when it comes to Wi-Fi across the 27,000-student campus. For instance, when the team first engineered classrooms for wireless, it was difficult to predict demand. Certain professors would need higher capacity for their lectures than others, so IT would accommodate them. If those professors got reassigned to different rooms the next year, they would immediately notice performance issues.

“They had delays and interruption of service so we had to go back and redesign all classrooms with more access points and more capacity,” Canevit says.

The university also has struggled with the fact that students and faculty are now showing up with numerous devices. “We see at least three devices per person, including smartphones, tablets, gaming consoles, Apple TV and more,” he says. IT has the dual challenge of supporting the education enterprise during the day and residential demands at night.

The school’s primary issue has revolved around IP addresses, which the university found itself low on as device count skyrocketed. “Devices require IP addresses even when sitting in your pocket and we faced a terrible IP management issue,” he says. IT had to constantly scour the network for unused IP addresses to “feed the monster.”

Eventually the team came too close to capacity for comfort and had to act. Canevit didn’t think IPv6 was widely enough supported at the time, so the school went with Network Address Translation instead, hiding private IP addresses behind a single public address. A side effect of NAT is that mapping network and security issues to specific devices becomes more challenging, but Canevit says the effort is worth it.

Looking forward, the university faces the ongoing challenge of providing Wi-Fi coverage to every dorm room and classroom. That’s a bigger problem than capacity. “We only give 100Mbps on the wired network in residence halls and don’t come close to hitting capacity,” he says, so 802.11ac is really not on the drawing board. What’s more, 802.11ac would exacerbate his coverage problem. “To get 1Gbps, you’ll have to do channel bonding, which leaves fewer overlapping channels available and takes away from the density,” he says.

What he is intrigued by is software-defined networking. Students want to use their iPhone to control their Apple TV and other such devices, which is impossible currently because of subnets. “If you allowed this in a dorm, it would degrade quality for everyone,” he says. SDN could give wireless administrators a way around the problem by making it possible to add boatloads of virtual LANs. “Wireless will become more of a provisioning than an engineering issue,” Canevit predicts.

Hospital all-in with Wi-Fi

Armand Stansel, director of IT infrastructure at Houston’s The Methodist Hospital System, recalls a time when his biggest concern regarding Wi-Fi was making sure patient areas had access points. “That was in early 2000 when we were simply installing Internet hotspots for patients with laptops,” he says.

Today, the 1,600-bed, five-hospital system boasts 100% Wi-Fi coverage. Like Riverside Medical Center, The Methodist Hospital has integrated wireless deep into the clinical system to support medical devices such as IV pumps, portable imaging systems for radiology, physicians’ tablet-based consultations and more. The wireless network has 20,000 to 30,000 touches a day, which has doubled in the past few years, Stansel says.

And if IT has its way, that number will continue to ramp up. Stansel envisions a majority of employees working on the wireless network. He wants to transition back-office personnel to tablet-based docking systems when the devices are more “enterprise-ready” with better security and durability (battery life and the device itself).

Already he has been able to reduce wired capacity by more than half due to the rise of wireless. Patient rooms, which used to have numerous wired outlets, now only require a few for the wired patient phone and some telemetry devices.

When the hospital does a renovation or adds new space, Stansel spends as much time planning the wired plant as he does studying the implications for the Wi-Fi environment, looking at everything from what the walls are made of to possible sources of interference. And when it comes to even the simplest construction, such as moving a wall, he has to deploy a team to retest nearby access points. “Wireless does complicate things because you can’t leave access points static. But it’s such a necessity, we have to do it,” he says.

He also has to reassess his access point strategy on an ongoing basis, adding more or relocating others depending on demand and traffic patterns. “We always have to look at how the access point is interacting with devices. A smartphone connecting to Wi-Fi has different needs than a PC and we have to monitor that,” he says.

The Methodist Hospital takes advantage of a blend of 802.11b, .11g and .11n in the 2.4GHz and 5GHz spectrums. Channel bonding, he has found, poses challenges even for .11n, reducing the number of channels available for others. The higher the density, he says, the less likely he can take full advantage of .11n. He does use n for priority locations such as the ER, imaging, radiology and cardiology, where users require higher bandwidth.

Stansel is betting big that wireless will continue to grow. In fact, he believes that by 2015 it will surpass wired 3-to-1. “There may come a point where wired is unnecessary, but we’re just not there yet,” he says.

Turning on the ac

Stansel is, however, onboard with 802.11ac. The Methodist Hospital is an early adopter of Cisco’s 802.11ac wireless infrastructure. To start, he has targeted the same locations that receive 802.11n priority. If a patient has a cardiac catheterization procedure done, the physician who performed the procedure can interactively review the results with the patient and family while he is still in the recovery room, referencing dye images from a wireless device such as a tablet. Normally, physicians have to verbally brief patients just out of surgery, then do likewise with the family, and wait until later to go over high-definition images from a desktop.

Current wireless technologies have strained to support access to real-time 3D imaging (also referred to as 4D), ultrasounds and more. Stansel expects better performance as 802.11ac is slowly introduced.

Riverside Medical Center’s Devine is more cautious about deploying 802.11ac, saying he is still a bit skeptical. “Can we get broader coverage with fewer access points? Can we get greater range than with 802.11n? That’s what is important to us,” he says.

In the meantime, Devine plans to deploy 20% to 25% more access points to support triangulation for location of equipment. He’ll be able to replace RFID to stop high-value items such as Ascom wireless phones and heart pumps from walking out the door. “RFID is expensive and a whole other network to manage. If we can mimic what it does with Wi-Fi, we can streamline operations,” he says.

High-power access points currently are mounted in each hallway, but Devine wants to swap those out with low-power ones and put regular-strength access points in every room. If 802.11ac access points prove to be affordable, he’ll consider them, but won’t put off his immediate plans in favor of the technology.

The future of Wi-Fi

Enterprise Strategy Group Senior Analyst John Mazur says that Wi-Fi should be front and center in every IT executive’s plans. BYOD has tripled the number of Wi-Fi connected devices and new access points offer about five times the throughput and twice the range of legacy Wi-Fi access points. In other words, Mazur says, Wi-Fi is up to the bandwidth challenge.

He warns IT leaders not to be scared off by spending projections, which, according to ESG’s 2013 IT Spending Intentions Survey, will be at about 2012 levels and favor cost-cutting (like Devine’s plan to swap out RFID for Wi-Fi) rather than growth initiatives.

But now is the time, he says, to set the stage for 802.11ac, which is due to be ratified in 2014. “IT should require 802.11ac support from their vendors and get a commitment on the upgrade cost and terms before signing a deal. Chances are you won’t need 802.11ac’s additional bandwidth for a few years, but you shouldn’t be forced to do forklift upgrades/replacements of recent access points to get .11ac. It should be a relatively simple module or software upgrade to currently marketed access points.”

While 802.11ac isn’t even fully supported by wireless clients yet, Mazur recommends keeping your eye on the 802.11 sky. Another spec, 802.11ad, which operates in the 60GHz spectrum and is currently geared toward home entertainment connectivity and near-field HD video connectivity, could be — like other consumer Wi-Fi advances — entering the enterprise space sooner rather than later.

Source:  networkworld.com

Cheat sheet: What you need to know about 802.11ac

Friday, June 21st, 2013

Wi-Fi junkies, people addicted to streaming content, and Ethernet-cable haters are excited. There’s a new Wi-Fi protocol in town, and vendors are starting to push products based on the new standard out the door. It seems like a good time to meet 802.11ac, and see what all the excitement’s about.

What is 802.11ac?

802.11ac is a brand new, soon-to-be-ratified wireless networking standard under the IEEE 802.11 protocol. 802.11ac is the latest in a long line of protocols that started in 1999:

  • 802.11b provides up to 11 Mb/s per radio in the 2.4 GHz spectrum. (1999)
  • 802.11a provides up to 54 Mb/s per radio in the 5 GHz spectrum. (1999)
  • 802.11g provides up to 54 Mb/s per radio in the 2.4 GHz spectrum (2003).
  • 802.11n provides up to 600 Mb/s per radio in the 2.4 GHz and 5.0 GHz spectrum. (2009)
  • 802.11ac provides up to 1000 Mb/s (multi-station) or 500 Mb/s (single-station) in the 5.0 GHz spectrum. (2013?)

802.11ac is a significant jump in technology and data-carrying capabilities. The following slide compares specifications of the 802.11n (current protocol) specifications with the proposed specs for 802.11ac.

(Slide courtesy of Meru Networks)

What is new and improved with 802.11ac?

For those wanting to delve deeper into the inner workings of 802.11ac, this Cisco white paper should satisfy you. For those not so inclined, here’s a short description of each major improvement.

Larger bandwidth channels: Bandwidth channels are part and parcel to spread-spectrum technology. Larger channel sizes are beneficial, because they increase the rate at which data passes between two devices. 802.11n supports 20 MHz and 40 MHz channels. 802.11ac supports 20 MHz channels, 40 MHz channels, 80 MHz channels, and has optional support for 160 MHz channels.

(Slide courtesy of Cisco)

More spatial streams: Spatial streaming is the magic behind MIMO technology, allowing multiple signals to be transmitted simultaneously from one device using different antennas. 802.11n can handle up to four streams where 802.11ac bumps the number up to eight streams.

(Slide courtesy of Aruba)

MU-MIMO: Multi-user MIMO allows a single 802.11ac device to transmit independent data streams to multiple different stations at the same time.

(Slide courtesy of Aruba)

Beamforming: Beamforming is now standard. Nanotechnology allows the antennas and controlling circuitry to focus the transmitted RF signal only where it is needed, unlike the omnidirectional antennas people are used to.

(Slide courtesy of Altera.)

What’s to like?

It’s been four years since 802.11n was ratified; best guesses have 802.11ac being ratified by the end of 2013. Anticipated improvements are: better software, better radios, better antenna technology, and better packaging.

The improvement that has everyone charged up is the monstrous increase in data throughput. Theoretically, it puts Wi-Fi on par with gigabit wired connections. Even if it doesn’t, tested throughput is leaps and bounds above what 802.11b could muster back in 1999.

Another improvement that should be of interest is Multi-User MIMO. Before MU-MIMO, 802.11 radios could only talk to one client at a time. With MU-MIMO, two or more conversations can happen concurrently, reducing latency.

Source:  techrepublic.com

With faster 5G Wi-Fi coming, Wi-Fi Alliance kicks off certification program

Thursday, June 20th, 2013

Process ensures 802.11ac devices work well with older Wi-Fi products

Although faster fifth-generation Wi-Fi is already available in some new wireless routers and even the new MacBook Air laptops, a new Wi-Fi Certified ac program is being launched today to ensure the newest devices interoperate with other Wi-Fi products.

The Wi-Fi Alliance announced the certification program for 802.11ac Wi-Fi (also known as 5G Wi-Fi). Mobile devices, tablets, laptops, networking gear and other hardware will be available in the last half of 2013 with a Wi-Fi Certified label, ensuring that the devices have been tested to interoperate with other 802.11ac products and older Wi-Fi products.

“The certification program ensures that users can purchase the latest device and not worry if it will work with a device of two years or even 10 years ago,” said Kevin Robinson, senior marketing manager for the Wi-Fi Alliance in an interview.

The faster Wi-Fi allows two-to-three times faster speeds than existing 802.11n technology, Robinson said. It will enhance the speed of movie downloads and other user needs in a home or work place.

Robinson said that 802.11ac should allow a transfer of an HD movie to a tablet in under four minutes, and allow for multiple video streams inside a home at one time. “The average user will notice the difference,” he said, contrary to what some analysts have predicted.

Theoretical maximum speeds on 802.11ac can reach 1.3 Gbps, three times 802.11n’s speeds of 450 Mbps. Older 802.11g supports theoretical speeds of up to 54 Mbps. Actual speeds will be far lower, depending mainly on the number of users and the type of data being transferred.

Aside from faster speeds, 802.11ac allows for more network capacity so that more devices can be simultaneously connected to a network. Because of the added network capacity with 802.11ac, Robinson said that movies can be run without as much less compression, enhancing their overall visual quality. Wi-Fi over 802.11ac also reduces network latency, resulting in fewer delays in streaming music and gaming applications.

Wi-Fi Direct, which is technology to allow device-to-device interoperability with 802.11n, is not yet part of the 802.11ac certification program, Robinson said.

The Wi-Fi Alliance predicts that many of the new routers made with 802.11ac will operate on both the 5GHz and 2.4 GHz bands. That way, 802.11n traffic will be able to run over both bands, while 802.11ac traffic runs over 5GHz. Robinson said that 2.4 GHz will remain sufficient for carrying data for many apps and uses, such as Web browsing. Migrating to 5GHz allows wider spectrum channels with higher data throughputs, yielding higher performance. An advantage of 5 GHz is that various channel widths are supported — 20 MHz, 40 MHz and 80 MHz– while 2.4GHz allows only three 20 MHz channels.

The Wi-Fi Alliance said 11 chips and other components are being used to test new 802.11 ac devices. They are from Broadcom, Intel, Marvell, Mediatek, Qualcomm and Realtek. A list of Wi-Fi Certified ac products is available at www.wi-ficertifiedac.com.

As an indication of the fast industry adoption of 802.11ac, Aruba Networks on May 21 announced new Wi-Fi access points supporting the technology and said more recently that the University of Delaware is a beta customer. Aruba is working for Wi-Fi Certified AC certification of the new access points, a spokeswoman said.

Robinson predicted that many of the recently announced routers and other products will seek Wi-Fi 802.11ac certification.

Source:  computerworld.com

The 49ers’ plan to build the greatest stadium Wi-Fi network of all time

Tuesday, March 19th, 2013

When the San Francisco 49ers’ new stadium opens for the 2014 NFL season, it is quite likely to have the best publicly accessible Wi-Fi network a sports facility in this country has ever known.

The 49ers are defending NFC champions, so 68,500 fans will inevitably walk into the stadium for each game. And every single one of them will be able to connect to the wireless network, simultaneously, without any limits on uploads or downloads. Smartphones and tablets will run into the limits of their own hardware long before they hit the limits of the 49ers’ wireless network.

Jon Brodkin

Until now, stadium executives have said it’s pretty much impossible to build a network that lets every single fan connect at once. They’ve blamed this on limits in the amount of spectrum available to Wi-Fi, despite their big budgets and the extremely sophisticated networking equipment that largesse allows them to purchase. Even if you build the network perfectly, it would choke if every fan tried to get on at once—at least according to conventional wisdom.

But the people building the 49ers’ wireless network do not have conventional sports technology backgrounds. Senior IT Director Dan Williams and team CTO Kunal Malik hail from Facebook, where they spent five years building one of the world’s largest and most efficient networks for the website. The same sensibilities that power large Internet businesses and content providers permeate Williams’ and Malik’s plan for Santa Clara Stadium, the 49ers’ nearly half-finished new home.

“We see the stadium as a large data center,” Williams told me when I visited the team’s new digs in Santa Clara.

I had previously interviewed Williams and Malik over the phone, and they told me they planned to make Wi-Fi so ubiquitous throughout the stadium that everyone could get on at once. I had never heard of such an ambitious plan before—how could this be possible?

Today’s networks are impressive—but not unlimited

An expansive Wi-Fi network at this year’s Super Bowl in the New Orleans Superdome was installed to allow as many as 30,000 fans to get online at once. This offloaded traffic from congested cellular networks and gave fans the ability to view streaming video or do other bandwidth-intensive tasks meant to enhance the in-game experience. (Don’t scoff—as we’ve noted before, three-plus-hour NFL games contain only 11 minutes of actual game action, or a bit more if you include the time quarterbacks spend shouting directions at teammates at the line of scrimmage. There is plenty of time to fill up.)

Superdome officials felt a network allowing 30,000 simultaneous connections would be just fine, given that the previous year’s Super Bowl saw only 8,260 at its peak. They were generally right, as the network performed well, even for part of the game’s power outage.

The New England Patriots installed a full-stadium Wi-Fi network this past season as well. It was never used by more than 10,000 or so people simultaneously, or by more than 16,000 people over the course of a full game. “Can 70,000 people get on the network at once? The answer to that is no,” said John Brams, director of hospitality and venues at the Patriots’ network vendor, Enterasys. “If everyone tried to do it all at once, that’s probably not going to happen.”

But as more fans bring smart devices into stadiums, activities like viewing instant replays or live camera angles available only to ticket holders will become increasingly common. It’ll put more people on the network at once and require bigger wireless pipes. So if Williams and Malik have their way, every single 49ers ticket holder will enjoy a wireless connection faster than any wide receiver sprinting toward the end zone.

“Is it really possible to give Wi-Fi to 68,500 fans at once?” I asked. I expected some hemming and hawing about how the 49ers will do their best and that not everyone will ever try to use the network at once anyway.

“Yes. We can support all 68,500,” Williams said emphatically.

How?

“How not?” he answered.

Won’t you have to limit the capacity each fan can get?

Again, absolutely not. “Within the stadium itself, there will probably be a terabit of capacity. The 68,500 will not be able to penetrate that. Our intentions in terms of Wi-Fi are to be able to provide a similar experience that you would receive with LTE services, which today is anywhere from 20 to 40 megabits per second, per user.

“The goal is to provide you with enough bandwidth that you would saturate your device before you saturate the network,” Williams said. “That’s what we expect to do.”

Fans won’t be limited by what section they’re in, either. If the 49ers offer an app that allows fans to order food from their seats, or if they offer a live video streaming app, they’ll be available to all fans.

“The mobile experience should not be limited to, ‘Hey, because you sit in a club seat you can see a replay, but because you don’t sit in a club seat you can’t see a replay,'” Malik said. “That’s not our philosophy. Our philosophy is to provide enhancement of the game experience to every fan.” (The one exception would be mobile features designed specifically for physical features of luxury boxes or club seats that aren’t available elsewhere in the stadium.)

It’s the design that counts

Current stadium Wi-Fi designs, even with hundreds of wireless access points distributed throughout a stadium, often can support only a quarter to a half of fans at once. They also often limit bandwidth for each user to prevent network slowdowns.

The Patriots offer fans a live video and instant replay app, with enough bandwidth to access video streams, upload photos to social networks, and use the Internet in general. Enterasys confirmed to Ars that the Patriots do enforce a bandwidth cap to prevent individual users from overloading the network, but Enterasys would not say exactly how big the cap is. The network has generally been a success, but some users of the Patriots app have taken to the Android app store to complain about the stadium Wi-Fi’s performance.

According to Williams, most current stadium networks are limited by a fundamental problem: sub-optimal location of wireless access points.

“A typical layout is overhead, one [access point] in front of the section, one behind the section, and they point towards each other,” he said. “This overhead design is widely used and provides enough coverage for those using the design.”

Williams would not reveal the exact layout of the 49ers’ design, perhaps to prevent the competition from catching on. How many access points will there be? “Zero to 1,500,” he said in a good-natured attempt to be both informative and vague.

That potentially doubles or quadruples the typical amount of stadium access points—the Super Bowl had 700 and the Patriots have 375. But this number isn’t the most important thing. “The number of access points will not give you any hint on whether the Wi-Fi is going to be great or not,” Malik said. “Other factors control that.”

If the plan is to generate more signal strength, just adding more access points to the back and front of a section won’t do that.

The Santa Clara Stadium design “will be unique to football stadiums,” Williams said. “The access points will be “spread and distributed. It’s really the best way to put it. Having your antennas distributed evenly around fans.” The 49ers are testing designs in Candlestick Park and experimenting with different access points in a lab. The movement of fans and the impact of weather on Wi-Fi performance are among the factors under analysis.

“Think of a stadium where it’s an open bowl, its raining, people are yelling, standing, how do you replicate that in your testing to show that if people are jumping from their seats, how is Wi-Fi going to behave, what will happen to the mobile app?” Malik said. “There is a lot that goes on during a game that is hard to replicate in your conceptual simulation testing. That is one of the big challenges where we have to be very careful.”

“We will make great use of Candlestick over the next year as we continue to test,” Williams said. “We’re evaluating placement of APs and how that impacts RF absorption during the game with folks in their seats, with folks out of their seats.”

Wi-Fi will be available in the stands, in the suites, in the walkways, in the whole stadium. The team has not yet decided whether to make Wi-Fi available in outdoor areas such as concourses and parking lots.

The same could theoretically be done at the 53-year-old Candlestick Park, even though it was designed decades before Wi-Fi was invented. Although the stadium serves as a staging ground for some of the 49ers’ wireless network tests, public access is mainly limited to premium seating areas and the press box.

The reason Wi-Fi in Candlestick hasn’t been expanded is a practical one. With only one year left in the facility, the franchise has decided not to invest any more money in its network. But Williams said 100 percent Wi-Fi coverage with no bandwidth caps could be done in any type of stadium, no matter how old. He says the “spectrum shortage” in stadiums is just a myth.

With the new stadium still undergoing construction, it was too early for me to test anything resembling Santa Clara Stadium’s planned Wi-Fi network. For what it’s worth, I was able to connect to the 49ers’ guest Wi-Fi in their offices with no password, and no problems.

The 2.4GHz problem

There is one factor preventing better stadium Wi-Fi that even the 49ers may not be able to solve, however. Wi-Fi works on both the 2.4GHz and 5GHz bands. Generally, 5GHz is better because it offers more powerful signals, less crowded airwaves and more non-overlapping channels that can be devoted to Wi-Fi use.

The 2.4GHz band has 11 channels overall and only three that don’t overlap with each other. By using somewhat unconventionally small 20MHz channels in the 5GHz range, the 49ers will be able to use about eight non-overlapping channels. That’s despite building an outdoor stadium, which is more restricted than indoor stadiums due to federal requirements meant to prevent interference with systems like radar.

Each 49ers access point will be configured to offer service on one channel, and access points that are right next to each other would use different channels to prevent interference. So even if you’re surrounding fans with access points, as the 49ers plan to, they won’t interfere with each other.

But what if most users’ devices are only capable of connecting to the limited and crowded 2.4GHz band? Enterasys said 80 percent of Patriots fans connecting to Wi-Fi this past season did so from devices supporting only the 2.4GHz band, and not the 5GHz one.

“You have to solve 2.4 right now to have a successful high-density public Wi-Fi,” Brams said.

The iPhone 5 and newer Android phones and tablets do support both the 2.4GHz and 5GHz bands, however. Williams said by the time Santa Clara Stadium opens in 2014, he expects 5GHz-capable devices to be in much wider use.

When asked if the 49ers would be able to support 100 percent of fans if most of them can only connect to 2.4GHz, Williams showed a little less bravado.

“For those 2.4 users we will certainly design it so that there’s less interference,” he said. “It is a more dense environment if you are strictly constrained in 2.4, but we are not constrained in 2.4. We’re not trying to answer the 2.4 problem, because we have 5 available.”

“It’s 2013, we have another year and a half of iteration,” he also said. “We’ll probably be on, what, the iPhone 7 by then? The move to 5GHz really just makes us lucky. We’re doing this at the right time.”

Building a stadium in Facebook’s image

Williams and Malik both joined the 49ers last May. Malik was hired first, and then brought his old Facebook friend, Williams, on board. Malik had been the head of IT at Facebook, while Williams was the website’s first network engineer and later a director. They both left the site, basically because they felt there was nothing left to accomplish. Williams did some consulting, and Malik initially planned to take some time off.

Williams was a long-time 49ers season ticket holder, but that was far from the only thing that sold him on coming to the NFL.

“I had been looking for something challenging and fun again,” Williams said. “Once you go through an experience like Facebook, it’s really hard to find something that’s similar. When Kunal came to me, I remember it like it was yesterday. He said, ‘If you’re looking for something like Facebook you’re not going to find it. Here’s a challenge.'”

“This is an opportunity to change the way the world consumes live sports in a stadium,” Malik said. “The technology problems live sports has today are unsolved and no one has ever done what we are attempting to do here. That’s what gets me out of bed every day.”

Williams and Malik have built the 49ers’ network in Facebook’s image. That means each service—Wi-Fi, point-of-sale, IPTV, etc.—gets its own autonomous domain, a different physical switching system to provide it bandwidth. That way, problems or slowdowns in one service do not affect another one.

“It’s tribal knowledge that’s only developed within large content providers, your Facebooks, your Googles, your Microsofts,” Williams said. “You’ll see the likes of these large content providers build a different network that is based on building blocks, where you can scale vertically as well as horizontally with open protocols and not proprietary protocols.

“This design philosophy is common within the content provider space but has yet to be applied to stadiums or venues. We are taking a design we have used in the past, and we are applying it here, which makes sense because there is a ton of content. I would say stadium networks are 10 years behind. It’s fun for us to be able to apply what we learned [at Facebook].”

The 49ers are still evaluating what Wi-Fi equipment they will use. The products available today would suit them fine, but by late 2014 there will likely be stadium-class access points capable of using the brand-new 802.11ac protocol, which allows greater throughput in the 5GHz range than the widely used 802.11n. 11ac consumer devices are rare today, but the 49ers will use 802.11ac access points to future-proof the stadium if appropriate gear is available. 11ac is backwards compatible with 11n, so supporting the new protocol doesn’t leave anyone out—the 49ers also plan to support previous standards such as 11a, 11b, and 11g.

802.11ac won’t really become crucial until 802.11n’s 5GHz capabilities are exhausted, said Daren Dulac, director of business development and technology alliances at Enterasys.

“Once we get into 5GHz, there’s so much more capacity there that 11ac doesn’t even become relevant until we’ve reached capacity in the 5GHz range,” he said. “We really think planning for growth right now in 5GHz is acceptable practice for the next couple of years.”

Santa Clara Stadium network construction is expected to begin in Q1 2014. Many miles of cabling will support the “zero to 1,500” access points, which connect back to 48 server closets or mini-data centers in the stadium that in turn tie back to the main data center.

“Based on service type you plug into your specific switch,” Williams said. “If you’re IPTV, you’re in an IPTV switch, if you’re Wi-Fi you’re in a Wi-Fi switch. If you’re in POS [point-of-sale], you’re in a POS switch. It will come down to a Wi-Fi cluster, an IPTV cluster, a POS cluster, all autonomous domains that are then aggregated by a very large fabric, that allows them to communicate lots of bandwidth throughput, and allows them to communicate to the Internet.”

Whereas Candlestick Park’s network uses Layer 2 bridging—with all of the Wi-Fi nodes essentially on a single LAN— Santa Clara Stadium will rely on Layer 3 IP routing, turning the stadium itself into an Internet-like network. “We will be Layer 3 driven, which means we do not have the issue of bridge loops, spanning tree problems, etc.,” Williams said.

Keeping the network running smoothly

Wireless networks should be closely watched during games to identify interference from any unauthorized devices and identify usage trends that might result in changes to access points. At the Patriots’ Gillette Stadium, management tools show bandwidth usage, the number of fans connected to each access point, and even what types of devices they’re using (iPhone, Android, etc.) If an access point was overloaded by fans, network managers would get an alert. Altering radio power, changing antenna tilt, or adding radios may be required, but generally any major changes are made between games.

Enlarge / Dashboard view of Patriots’ in-game connectivity.
Enterasys

“In terms of real-time correction, it depends on what the event is,” said John Burke, a senior architect at Enterasys. “Realistically, some of these APs are overhead. If an access point legitimately went down and it’s on the catwalk above 300 [the balcony sections] you’re not going to fix that in the game. That’s something that would have to wait.”

So far, the Patriots’ capacity has been enough. Fans have yet to overwhelm a single access point. Even if they did, there is some overlap among access points, allowing fans to get on in case one AP is overloaded (or just broken).

The 49ers will use similar management tools to watch network usage and adjust access point settings in real time during games. “We expect to overbuild and actually play with things throughout,” Williams said. “Though we are building the environment to support 100 percent capacity, we do not expect 100 percent capacity to be used, so we believe we will be able to move resources around as needed [during each game].”

The same sorts of security protections in place in New England will be used in Santa Clara. Business systems will be password-protected and encrypted, and there will be encrypted tunnels between access points and the back-end network. While that level of protection won’t extend to the public network, fans shouldn’t be able to attack each other, because peer-to-peer connections will not be allowed.

What if the worst happens and the power goes out? During the Super Bowl’s infamous power outage, Wi-Fi did stay on for at least a while. Williams and Malik acknowledged that no system is perfect, but they said that they plan for Wi-Fi uptime even if power is lost.

“We have generators in place, and we’ll have UPS systems, so from a communications standpoint our plan is to keep all the communication infrastructure up and online [during outages],” Williams said. “But all of this stuff is man-made.”

A small team that does it all

Believe it or not, the 49ers have a tech team of less than 10 people, yet the organization is designing and building everything itself. Sports teams often outsource network building to carriers or equipment vendors, but not the 49ers. Besides building its own Wi-Fi network, the team will build a carrier-neutral distributed antenna system to boost cellular signals within the stadium.

“We are control freaks,” Williams said with a laugh. He explained that doing everything themselves makes it easier to track down problems, accept responsibility, and fix things. They also feel the need to take ownership of the project because none of the existing networks in the rest of the league approach what they want to achieve. There is a lot of low-hanging fruit just from solving the easy problems other franchises haven’t addressed, they think.Not all the hardware must be in-house, though. The 49ers will use cloud services like Amazon’s Elastic Compute Cloud when it makes sense.

“Let’s say we want to integrate a POS system with ordering,” Malik said. “If you have an app that lets you order food, and there’s a point of sale system, all the APIs and integration need to sit in the cloud. There’s no reason for it to sit in our data center.”

There are cases where the cloud is clearly not appropriate, though. Say the team captures video on site and distributes it to fans’ devices—pushing that video to a faraway cloud data center in the middle of that process would slow things down dramatically. And ultimately, the 49ers have a greater vision than just providing Wi-Fi to fans.

When I toured a preview center meant to show off the stadium experience to potential ticket buyers, a mockup luxury suite had an iPad embedded in the wall with a custom application for controlling a projector. That provides a hint of what the 49ers might provide.

“Our view is whatever you have at home you should have in your suite,” Williams said. “If that means there’s an iPad on the wall or an application you can use, hopefully that’s available. Your life should be much easier in this stadium.”

And whatever applications are built should be cross-platform. As Malik said, the 49ers are moving away from proprietary technologies to standards-based systems so they can provide nifty mobile features to fans regardless of what device they use.

Williams and Malik are already working long hours, and their jobs will get even more time-intensive when network construction actually begins. But they wouldn’t have it any other way—particularly the longtime season ticket holder Williams.

When work is “tied to something that you love deeply, which is sports, and tied to your favorite team in the world, that’s awesome,” Williams said. “I’m crazy about it, man. I get super passionate.”

Source:  arstechnica.com

Cisco accelerates Wi-Fi with Aironet 3600

Thursday, January 31st, 2013

Cisco (NASDAQ:CSCO) is updating its WLAN portfolio today with a new flagship Aironet access point. The Aironet 3600 is a three spatial stream device with a simultaneous 2.4 and 5 GHz, 4×4 antenna design. The total theoretical speed of the access point comes in at 900 Mbps.

Specified speed alone doesn’t define the true capabilities of any Wi-Fi access point as things such as reach and signal integrity often are more important to end-users in an enterprise deployment.

“The cool thing about the extra fourth antenna is that we have a degree for redundancy that lets us speed up the slower clients,” Sylvia Hooks, senior manager, wireless solutions at Cisco.”We’re able to speed mobile devices that need speeding up and there is no special software or standards required on the client side.”

Hooks explained that the Aironet 3600 has four transmit and receive antennas that allow for more consistent upload speeds. The need for more consistent speeds is important to help consumer-grade devices like tablets that don’t have strong transmit power capabilities.

“So even if the signal is weak from the mobile device, we’re able to compensate,” Hooks said. “On the reverse side, when we get a signal from a mobile client, we’re able to calculate its location and then send back to that exact location using beamforming.”

She added that with the power to get stronger signals out to individual mobile devices, the access point is able to serve even more users, increasing the overall system capacity.  Aironet 3600 users can also roam farther than before.  Users can go up to 130 feet away from the access point without dropping down to a slower speed.  The integrity of the signal is further protected with Cisco’s Clean Air technology that analyses the wireless spectrum for potential interference.  Clean Air was first deployed by Cisco in 2010 on the Aironet 3500 series access points.

With the Aironet 3600, Cisco is also introducing support for the IEEE 802.11r standard which specifies Fast Roaming for wireless clients.

“It’s a standard that defines how clients roam between access points on the same network, fast enough so there aren’t any delays or lost connections,” Hooks said.

Another standard that is likely of interest to enterprise buyers is the emerging 802.11ac standard for gigabit Wi-Fi. Currently 802.11ac chip technology is mostly at the consumer-level, according to Hooks. That said, she didn’t rule out the future possibility that the Aironet 3600 could get an upgrade.

“We haven’t defined additional modules yet to snap into this access point although it does have the ability to snap in a totally new radio,” Hooks said. “At this time, Cisco hasn’t formally announced any plans but the intention of the platform is that it is modular enough to accept new technologies.”

Source:  wi-fiplanet.com

The best 802.11ac routers featured at CES

Sunday, January 13th, 2013

If you’re in the market for a new [consumer grade] router, consider holding out for these new models.

At last year’s CES, 802.11ac was hardly prevalent on the show floor. Though other companies were still showing off their 802.11n capable routers, only Texas-based Buffalo had a prototype router set up at its booth for attendees to see. This year, the tables seemed to have turned, as the show floor was rampant with 802.11ac products, including varying routers from competing companies.

Interestingly enough, all of the routers featured here claim to be able to dial in a hearty 1300Mbps on their 5GHz band. Whether this is true or not remains to be seen—we haven’t used any of them just yet—but one thing is for sure: if you’re buying a new router this year, you may want to consider making the switch to 802.11ac after all. Fortunately, there were plenty of choices on display at CES, so here are a few of the models worth looking out for later this year.

http://cdn.arstechnica.net/wp-content/uploads/2013/01/buffalo-airstation-1750.jpgBuffalo AirStation AC1750 Gigabit Dual Band Wireless Router – WZR-1750DHP

The AirStation AC1750 Gigabit Dual Band Wireless Router (or, more simply, model WZR-1750DHP) will cost $179 and feature speeds up to 1300Mbps on the 5GHz band and 450Mbps on the 2.4GHz band. It also contains a dual-core chip for Buffalo’s Beamforming technology, which provides faster Wi-Fi speeds and longer ranges. Additionally, it will ship with four gigabit Ethernet ports, as well as USB 3.0 and USB 2.0 ports for NAS-like functionality and printer sharing. It’s expected to ship late this year.

http://cdn.arstechnica.net/wp-content/uploads/2013/01/D6200_HiRes-300x420.jpgNetgear D6200 Wi-Fi DSL Modem Router

Netgear announced a slew of products at its official CES 2013 press conference, one of which was the 802.11ac-compatible, dual-band gigabit D6200 Wi-Fi router. The router features built-in ADSL2+ model and Gigabit WAN with support for fiber-optic connections. It also comes with a proprietary featured dubbed Netgear ReadySHARE cloud that allows users to remotely access hard drives, printers, and flash drives that are tethered to the monitor. It will be available in April.

http://cdn.arstechnica.net/wp-content/uploads/2013/01/EA6700_top_reflection-300x253.jpgLinksys Smart Wi-Fi Router AC1750 HD Video Pro, EA6700

The Smart Wi-Fi Router AC1750 HD Video Pro, EA 6700 is one of the beefier router models the company showed off at CES. The dual-band EA 6700 supports up to 10 or more connected devices and can support streaming HD video, as well as Wi-Fi speeds of up to 1300Mbps on the 5GHz band and up to 450Mbps on the 2.4GHz band. As an added bonus, it also syncs up with Linksys’s iOS and Android apps and features SmartMap, which offers a virtual representation of every device connected within the network. No word yet on its availability.

D-link AC1750 Dual-Band Gigabit Cloud Router, DIR-868L

D-link debuted a couple of new 802.11ac routers on the show floor, one of which is the DIR-868L: a dual-band gigabit, cloud-capable router with the ability to control its settings via a mobile app or the Web. The cylindrical shaped router is a nice change of pace from the standard “skinny box” model and features a Broadcom-based processor inside to facilitate StreamBoost, which helps designate the appropriate amount of bandwidth for all of the devices connected to the router. The router should be available later this year.

Source:  arstechnica.com

Terahertz frequencies bring Japanese researchers 3Gbps in a WiFi prototype

Thursday, May 17th, 2012

The tiny wireless radio transmits on spectrum between 300GHz and 3THz

http://cdn.arstechnica.net/wp-content/uploads/2012/05/extremetech-rohm-wireless-chip-348x1961.jpg

A team of researchers at the Tokyo Institute of Technology have transmitted data on the terahertz range of spectrum using a wireless radio no bigger than a 10-yen coin (roughly the size of a penny). The tiny contraption can access spectrum between 300GHz and 3THz (otherwise known as T-Rays for terahertz), and was able to transfer data at a speed of 3Gbps. But this was only a test run—researchers suspect that using terahertz spectrum could get data transfer up to rates of 100 Gbps.

The newest WiFi standard available to consumers (but not yet ratified by the IEEE), 802.11 ac, transmits on a 5GHz band and can theoretically achieve 1.3Gbps. There’s an even-further-out standard in the works as well; 802.11ad (otherwise known as WiGig) will transmit on the 60 GHz rage for a theoretical 10 Gbps—although this will generally only be within a line-of-sight range.

A T-ray based WiFi is certainly far off, and the greatly increased frequency of the transmission will undoubtedly require devices using terahertz spectrum to be quite close to each other. As Extreme Tech points out, the short distance of transmission for this technology would be better for server farms than anything else, permitting servers to share data between each other wirelessly rather than through a web of wiring.

Aside from the potentially huge bandwidth of T-ray networking, there’s another reason the spectrum is so attractive. Terahertz waves are unregulated, and present an untouched frontier away from currently crowded bands of spectrum.

Source:  arstechnica.com

802.11ac boosts buzz more than bandwidth

Friday, January 27th, 2012

A great innovation, 802.11ac does more for 802.11n than it does to change the face of wireless networking

The buzz about 802.11ac is in full swing, but don’t believe everything you read.

The newest of Wi-Fi innovations, 802.11ac (still in draft form) looks like it will start making it into enterprise Wi-Fi products as early as 2013 and home products even earlier. It’s already being flaunted as Gigabit Wi-Fi. And for the largest Wi-Fi market, the home, it will be. But will it deliver gigabit speeds for the enterprise? Not a chance.

Defined for the capacity-rich 5GHz spectrum (495MHz) only, 802.11ac introduces a number of new techniques like advanced modulation and encoding, multi-user MIMO and channel bonding, that theoretically, if you’re talking to a vendor anyway, has the potential to dramatically increase Wi-Fi capacity. The question is, REALLY?

Make no mistake, 802.11ac is a great innovation. But like any great innovation, the devil is often in the details. So here are some details that should help demystify 802.11ac. Here are the key differences to understand:

* Eight spatial streams. One of the biggest Wi-Fi innovations came with 802.11n in the form of spatial multiplexing using a technique called MIMO (multiple input, multiple output). MIMO is the use of multiple antennas at both the transmitter and receiver to increase data throughput without additional bandwidth or increased transmit power. Basically it spreads the same total transmit power over multiple antennas to achieve more bits per second per hertz of bandwidth with the added benefit of greater reliability due to more antenna diversity.

In essence, MIMO lets an access point send multiple spatial streams to one client at a time to increase capacity. 802.11n specified up to four spatial streams.

Now in glorious one-upmanship, 802.11ac will support up to eight spatial streams. Historically it has taken chip manufacturers about two years to add an additional spatial stream (802.11n is only at three right now). While that will surely improve with 802.11ac, don’t look for it to ever get to eight. However it would be a funny sight to see. Just picture an AP with 12 omni-directional antennas (eight for 11ac in 5GHz and four for 11n in 2.4GHz) sticking out of it. Not a pretty picture.

* Multi-user MIMO. Another difference with 11ac is support for “multi-user MIMO” (MU-MIMO). With 802.11n, MIMO could only be used for a single client at any given time, while 802.11ac tries to improve on this by supporting multiple clients.

This allows an 802.11ac AP to transmit two (or more, depending on the number of radio chains) spatial streams to two or more client devices. This has the potential to be a good improvement but is optional. And it’s expected that the first 802.11ac chips out the door won’t support this. What’s more, there’s is a good chance that MU-MIMO won’t ever be supported due to the radio and MAC complexity required.

* 256 Quadrature Amplitude Modulation (QAM). QAM is a way to modulate radio waves to transmit data. 802.11n maxed out at 64QAM so the advent of 256QAM should deliver big improvements in maximum throughput. However, the more complex a modulation scheme, the more difficult it is to achieve. In realistic situations it is highly unlikely that any percentage of client devices would consistently achieve 256QAM. Ouch.

* 5GHz only. Due to how 11ac really achieves all this speed (channel bonding) it doesn’t make sense for 11ac to support 2.4GHz which only has three (of 11) non-overlapping channels. What this means is that devices that want to have 11ac (they all will) will be 5GHz capable. Right now it is a very low percentage that are capable of 5GHz and that is a real shame. Now they’ll be required to do it.

* Channel bonding. An easy and effective method to increase the speed of any radio link is to give it more frequency, or bandwidth. To get more bandwidth, 802.11n introduced us to channel bonding: the ability to take two 20MHz channels and make them work as one — basically a bigger Wi-Fi pipe. This effectively doubled throughput that could be achieved.

Now 802.11ac has mandated the support of 80MHz channels with options to bond eight channels for a total channel of 160MHz.

Even with 802.11n, channel bonding is a double-edged sword. In North America, the 2.4GHz band has 83.5MHz (three non-overlapping channels) of total bandwidth, while the 5GHz bands have a total of 495MHz. That means that 5GHz can carry almost six times the traffic of 2.4GHz plus the added benefit that (for now) the 5GHz band is a much cleaner spectrum.

But don’t count your bits quite yet. What most people don’t realize is that by enabling channel bonding you are actually reducing your overall capacity (see chart).

When designing and deploying a Wi-Fi network for high density, more channels are preferred to fewer, larger channels. Increasing the number of devices occupying one channel in a given area makes reduces the efficiency of Wi-Fi.

This is why people like wires. Because each device effectively has its own channel and there are no other devices occupying that channel (the copper or fiber). So we see staggering amounts of throughput.

If Wi-Fi could have hundreds of channels, and each client would get their own, this would be wireless nirvana. But, as you can see from that chart, we don’t have that many channels, and we sure don’t want to exacerbate the problem by bonding them together if it reduces the overall efficiency of the wireless LAN.

Using 802.11ac in the home is a different story. Bonding channels all the way to 160MHz is preferred given there are few devices trying to access a single AP.

The enterprise is just the opposite. Here, numerous APs are required to support hundreds or thousands of users. And, as much as is possible, those APs should be on different channels.

Ultimately, 802.11ac offers improvements for the Wi-Fi industry primarily because it forces clients to add support for the capacity-rich 5GHz spectrum. Current enterprise APs already support both bands.

Ironically, 802.11ac will prolong the viability of current 802.11n networks. As more and more clients become 5GHz capable, capacity and performance will increase without touching the infrastructure. This is the best news of all.

Source:  networkworld.com