Dual-mode: Two is better than one

Smart phones that switch between cellular and Wi-Fi could reduce telecom expenses

If Jack Bauer didn’t always have his trusty personal digital assistant at his side, the world would have blown up a long time ago. The action hero star of the TV spy show “24” uses his handheld communicator to speak with presidents and download missile schematics as he races from the halls of the Counter Terrorism Unit to Los Angeles’ freeways without ever losing a connection.

Government leaders are eyeing the same level of ubiquitous communications in real life, but with a twist: A new, always-connected capability might also help reduce telecommunications expenses. 

Emerging dual-mode wireless communications combine cell phone services with equally common 802.11 Wi-Fi wireless networks. Callers using special smart phones and PDAs can seamlessly switch to the network with the best performance at the lowest cost as they roam in hot pursuit of a shadowy terror suspect or a broken water main in a remote part of town. Dual-mode supports voice and data communications.

“I would love to implement this in Washington,” said Vivek Kundra, chief technology officer of the District of Columbia. Wi-Fi lets you push voice, video and data at high throughput rates, he said. It also enables real-time video conferences. “That’s where the future is, and that’s where we are headed.”

Dual-mode technology was still too immature to use when he investigated it at a previous job, Kundra said. But he’s in preliminary talks with vendors now to see how dual-mode capabilities have advanced.

Industry executives say Kundra and other technology managers might still need to wait for the dream of seamless dual-mode roaming to become reality.

“I’ll consider it successful when people with no sympathy for the technology use it, and it just works,” said Peter Thornycroft, technology advocate at Aruba Networks, a vendor of Wi-Fi access points and network controllers. “We’re on the edge of being there, but we’re not there yet.”

Full coverage

Dual-mode’s evolving status hasn’t dampened interest in the concept.
“It’s being driven by the desire to take advantage of the Wi-Fi infrastructure for more than just data and to reduce costs,” said Jim Freeze, senior vice president at BelAir Networks, a vendor of mobile broadband mesh networking products including one with an integrated cellular base station.

What will eventually separate dual-mode communications from existing voice-over-Wi-Fi applications will be the ability for someone speaking via a Wi-Fi connection to leave the hot spot’s range and have the call automatically switch to a wide-area cellular network.

“It’s about having agencies with facilities that are spread out — or an inspection agency with many field workers — connect pretty much everywhere within the community,” said Sally Cohen, an analyst at Forrester Research. Network administrators would configure handsets to use the strongest signal available.

Analysts foresee communications costs declining and performance improving when wireless calls use available no-cost Wi-Fi networks whenever callers are within range of an enterprise wireless local-area network or public hot spot.

Executives could avoid expensive cellular service roaming charges when they travel domestically or internationally by finding suitable Wi-Fi networks to use instead.

Dual-mode offers other advantages. Wi-Fi overcomes some of the physical stumbling blocks that frustrate cellular callers, including buildings with steel infrastructures.

“If there’s a Wi-Fi hot spot in the building, you will have connectivity with your [dual-mode] phone, while the guy sitting next to you with a traditional cell phone gets nothing,” said Paul DeBeasi, senior analyst at the Burton Group. “It’s another way of gaining connectivity.”

Another benefit is higher data rates. Evolution-Data Optimized cellular networks, for example, might send data at speeds of 500 kilobits/sec, and real-world 802.11g wireless throughput is 20 megabits/sec to 30 megabits/sec.

Building blocks
Agencies that want to create Wi-Fi/cellular communications will need an 802.11g Wi-Fi infrastructure that can reliably accommodate voice traffic. One of its components is an IP private branch exchange  (IP PBX) to accommodate voice-over-IP traffic.

In addition, organizations might need to expand the number of wireless access points they’re using to provide network coverage. Some organizations concentrate Wi-Fi services in conference rooms and select offices. Achieving satisfactory coverage for voice services requires more access points.

“You’ve got to light up the whole building,” said Ken Dulaney, vice president of mobile computing at technology research firm Gartner. “If you have coverage holes, you’ll have call dropouts.”

Dropouts frequently occur in overlooked areas such as elevators, where employees often try to make calls.

Network management tools are needed to give delay-sensitive voice traffic priority over other types of data and guarantee voice service free of distortions or delays, Cohen said.

Other items are necessary, too, such as handsets designed for cellular and Wi-Fi communications. Although the list is growing, users only recently have been able to purchase professional-quality devices, Cohen said. Early entrants were plagued by handoff problems and low battery life, she said.

Dual-mode smart phones from Motorola, Nokia, HTC, Samsung and others have overcome many of those problems, and analysts say additional vendors will offer more models in the coming year.

Agencies can install IP PBXes with dual-mode capabilities from vendors such as Avaya and Siemens or upgrade their IP PBXes with technology from Aruba, Cisco Systems, Devitas, Tango Networks and New Step Networks. Because handsets require client software that is compatible with back-end hardware, agencies might need to choose from a subset of phone models supported by the telephony equipment vendor.

A final piece of the dual-mode puzzle is connectivity from cellular service providers for fixed mobile convergence. That refers to the integration of wired and wireless communications. Although cell phones connect wirelessly to nearby towers, calls may travel over wires to other network equipment.

T-Mobile was among the first cellular services providers to offer a Wi-Fi option. Analysts say they expect others to follow suit. However, some companies have been slow to adopt Wi-Fi for fear it will cannibalize revenues from their primary services.

“The cellular providers are begrudgingly deploying Wi-Fi networks because many of them view it as competition,” DeBeasi said. “But I think they’re realizing that it’s a foregone conclusion, and they’d better embrace it rather than fight it.”

Dropped calls

In the meantime, vendors of dual-mode hardware and software must correct some problems inherent in the technology. Smooth handoffs from Wi-Fi to cellular continue to be elusive. Thornycroft said switchovers now work better under controlled, demonstration-friendly conditions than in the real world.

“I don’t know of anyone who can point to an installation where thousands of handoffs are happening seamlessly,” Thornycroft said. “There are still a number of rough edges.”

Municipalities face coverage challenges similar to those associated with Wi-Fi LANs within buildings, only on a much larger scale, DeBeasi said.

“Police, fire and anti-terrorist organizations all need coverage in every inch of the state — and perhaps into another state’s jurisdiction if they’re chasing a prisoner or terrorist suspect,” he said. “And that kind of coverage just doesn’t exist. We don’t have one provider like a Verizon or an AT&T that can give you 100 percent coverage all the time.”

Agencies considering dual-mode communications should also focus on a new set of security concerns. “Government agencies need to set standards for deployment, including how you secure the technology, the types of devices you’ll support, how you’ll manage access control, how you’ll track who is logging in, and where…they go,” DeBeasi said.

One of the security challenges is general: Smart phones’ expanding storage holds large amounts of potentially sensitive information and leaves them open to security breaches if devices are lost or stolen. Agencies can address that vulnerability with strong passwords and data encryption available from handset vendors and third parties.

For secure communications via Wi-Fi networks, agencies should adhere to the Defense Department’s 8100.2 policy for wireless devices, experts say. That policy specifies encryption that meets the 802.11i Wi-Fi Protected Access Version 2 guidelines and Federal Information Processing Standard 140-2 standards, said Stephen Orr, consulting systems engineer at Cisco.

Dulaney recommended that agencies install perimeter analysis tools to prevent potential data thieves from intercepting data traffic from outside a building. “If you now have a voice service that people are depending on,” he said, “you need a monitoring system to make sure that resource stays pristine.

Alan Joch is a business and technology writer based in New England. He can be reached at [email protected]
New Wi-Fi standard sweetens the dealThe prevailing wireless local-area networking standards — 802.11a, 802.11b and 802.11g — create a communications foundation for dual-mode calls via cellular networks. With data-intensive applications continuing to push performance limits, the industry is drafting next-generation specifications.

Within the next three years, analysts expect the Institute of Electrical and Electronics Engineers to ratify a follow-on specification, 802.11n. That standard would offer numerous enhancements, including longer range and data-transmission speeds potentially greater than 100 megabits/sec. In the meantime, competitive pressures are pushing networking vendors to ship products that adopt preliminary versions of 802.11n. However, buyers don’t have guarantees that the final specification will support those cutting-edge products.

To ease some fears, the industry consortium known as the Wi-Fi Alliance announced in May its 802.11n “Draft 2.0” certification, an interim standard that incorporates core 802.11n features for increased performance. It is meant to be a bridge to the final guidelines.

“The Wi-Fi Alliance agreed to make sure that the final specification includes support for the interim certification,” said Ken Dulaney, vice president of mobile computing at technology research firm Gartner. “If you put in [Draft 2.0] infrastructure now, it will still work in the future.”

Dulaney said most organizations should wait for the ratified standard and continue to use 802.11a/b/g products. Agencies should consider products that support the draft version only if they have special needs that require performance beyond what the current specifications offer.

— Alan Joch
Dual-mode checklistDeploying a dual-mode, wireless voice-and-data system that lets users switch seamlessly between a wide-area cellular and local-area Wi-Fi network requires several components. They include:
  • Enough 802.11g wireless access points for ubiquitous Wi-Fi coverage, including elevators and shielded areas.
  • An 802.11g Wi-Fi infrastructure able to reliably handle voice traffic.
  • Network management controllers configured to give voice traffic bandwidth priority.
  • Dual-mode IP private branch exchanges to handle voice traffic carried on the organization’s enterprise network.
  • Dual-mode smart phones and personal digital assistants.
  • Wi-Fi connectivity services from cellular providers.
— Alan Joch


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