15JUNE 2009

Industry trends

Published by the IEEE Computer Society0018-9162/09/$25.00 © 2009 IEEE

M obile voice over IP (mVoIP) is a tempting prospect for many com-panies. After all, sending wireless phone calls over

IP networks is considerably less expen-sive than sending them over cellular voice networks.

mVoIP travels over IP networks with no dependency on the underlying com-munications infrastructure. Companies are already paying for their IP services, so that adds no more cost to the process. And if an organization uses Wi-fi for its mVoIP calls and already owns a Wi-fi network, that connection is free.

mVoIP can even work over a cellular network’s data channel, instead of its expensive voice channel. Because some cellular carriers offer either unlimited data services or low-cost charges based on the amount of data transmitted, the cost is minimal.

Nonetheless, mVoIP hasn’t taken off in the enterprise for several reasons. For example, the current technology doesn’t yet dependably offer enough perfor-mance, capabilities, call quality, security, or robustness.

Faster wireless-networking tech-nologies and more powerful mobile telephones promise to help solve these problems. With this in mind, provid-ers are working on mVoIP services designed for companies. Meanwhile, some businesses are beginning to con-sider using the technology for their mobile employees.

However, these efforts face several important challenges.

THE ENTERPRISE AND MOBILE VoIP

By 2004, wireline VoIP had become a mainstream technology with a place in the enterprise, said Matthias Machowinski, Infonetics Research’s directing analyst for enterprise voice and data.

Wireline VoIP packetizes voice com-munications, compresses them, and sends the transmissions over an IP network and eventually the public telephone system.

mVoIP uses both VoIP and wireless-networking technologies, each of which businesses are already investing in. This and mVoIP’s potential cost savings make the technology a natural for many businesses, according to Wi-fi Alliance executive director Edgar Figueroa.

“In the current global financial crisis, cost savings is one of the major reasons for using mVoIP,” said Tzahi Efrati, head mobile engineer with mVoIP provider Jajah.

The major mVoIP providers include 8 × 8 Inc. with its Packet8 Mobile Talk, Fring, Jajah with its Jajah.Mobile Web, Mobivox, Rebtel, Skype with its Skype Mobile, TerraSip with its TerraSip VoIP, Truphone, Vyke with its Mobile VoIP, and Yeigo.

Under the hoodmVoIP functions as an application that

runs over any wireless network technology that provides data access to the Internet.

As Figure 1 shows, these include Wi-fi, WiMax, and cellular approaches includ-ing those based on the Global System for Mobile Communications (GSM) and code division multiple access (CDMA) tech-nologies, according to Fring cofounder and chief architect Boaz Zilberman.

Running mVoIP over Wi-fi or WiMax—a straightforward process of sending packets from phones acting as nodes over the networks via access points—is less expensive overall because the technology’s infrastructure is less costly to build.

They also operate in unlicensed spec-trum. Carriers thus don’t have to spend money to buy spectrum licenses. In addi-tion, some companies save money because they run their own Wi-fi infrastructures.

However, the ability to work with cel-lular technologies lets mVoIP operate in areas where Wi-fi is unavailable.

mVoIP providers typically require users to download connection-management soft-ware onto their mobile device to access their service and let phones automatically roam between networks as necessary.

mVoIP handsets must have radio chips for each wireless-network type—such as Wi-fi or cellular—they will use for IP connections.

For quality of service, mVoIP via Wi-fi can rely on the IEEE 802.11e stan-dard for error correction and the tagging by handsets of voice packets as high priority, noted Dave LeClair, director of unified communications for enterprise-communications vendor Avaya.

David Geer

The Future of Mobile VoIP in the Enterprise

Industry trends

compUtEr 16

Figure 1. A Fring mVoIP handset, at the top center, contacts a standard cell or wireline phone via a Fring VoIP gateway server, as well as terminal servers for the traditional phone network. The gateway and terminal servers manage the calls and translate the mVoIP data into the codecs that cell and wireline technologies work with. The Fring API server translates protocols and other events related to data connectivity for use with Internet-based applications, shown in the lower right, such as Facebook and instant messaging. Fring handsets can contact each other directly without going through servers.

Fring handset Fring VoIP gateway and wireless phone system

termination servers

Fring handset

GSM orwireless phone

VoIP over data(3G, EDGE, and Wi-�)

VoIP over data(3G, EDGE, Wi-�, and GPRS)

Fring API server

Internet-based applications

IP

IP (VoIP)XML/HTTP

Source: Fring

Direct connection

Internetwork handoffs. GSM provid-ers, working through their 3rd Generation Partnership Project (3GPP), created the Unlicensed Mobile Access-Generic Access Network in 2004. With UMA, a gateway in the corporate network hands off calls between the GSM network and the unli-censed Wi-fi and WiMax networks.

This lets users of dual-mode GSM/Wi-fi phones save money by utilizing mVoIP over Wi-fi or WiMax when in range of those network types.

UMA operators include Cincinnati Bell, Fido Solutions, Orange, Rogers Communications, and T-Mobile.

Companies like Kyocera, Nortel Networks, PCTEL, and Qualcomm are working on proprietary approaches to let phones hand off calls between CDMA and either Wi-fi or WiMax networks, noted Irwin Lazar, vice president of communi-cations research for Nemertes Research, a market analysis firm.

IMS. CDMA and GSM operators are slowly transitioning to the IP Multimedia Subsystem, a framework for delivering IP-based multimedia services.

IMS, using open interfaces, serves as its own underlying network platform for

routing communications based on various networking protocols, including SIP.

IMS lets providers easily integrate multiple services on a single IP-based network, thereby leveraging existing network components to offer revenue-generating multimedia services.

Proprietary protocols. Some mVoIP providers—such as Skype, whose ser-vice can work with SIP, according to Nicholas Babaian, the company’s senior manager for mobile products—also use their own proprietary protocols for han-dling sessions.

SecurityTo protect mVoIP over cellular sys-

tems, providers use security techniques such as access control, packet filtering, and encryption.

The IEEE 802.11i standard provides security for Wi-fi-based mVoIP via approaches such as authentication and encryption.

In addition, mVoIP uses the same secu-rity approaches as wireline VoIP, such as the IETF’s Remote Authentication Dial-In User Service protocol. RADIUS provides centralized authentication, authorization,

mVoIP via cellular services achieves QoS by prioritizing voice packets over those used for data and other traffic types.

CellularmVoIP calls can run over cellular net-

works’ data channels. mVoIP providers, rather than cellular carriers, offer this service.

SIP. When mVoIP runs over GSM- or CDMA-based networks, it can use the Internet Engineering Task Force’s (IETF’s) Session Initiation Protocol. SIP establishes, manages, modifies, and ter-minates interactive voice, video, chat, and data sessions on any wireless IP network, including those used for fixed and mobile VoIP.

The process starts when a client requests to open a session with an SIP server and another SIP client, which responds affir-matively if it wants to participate.

Participants need an authentication server to authorize them as valid users and set up their SIP uniform resource identifier, explained LeClair. The URI functions as a link for contacting a phone number via mVoIP.

17JUNE 2009

and jitter, and thus their quality isn’t always good enough for mission-critical business communication.

Skype’s Babaian said that congestion, coverage limitations, and network poli-cies that give priority to circuit-switched calls over those made via mVoIP can cause problems.

Zilberman noted that radio-based communications, such as those used in cellular or Wi-fi technologies, can be affected by wind, rain, and other weather-related issues.

According to Jayanth Angl, senior research analyst for the Info-Tech Research Group, the unlicensed 2.4- and 5-GHz frequency ranges in which Wi-fi operates commonly experience signal interference because they are heavily used.

Balancing cost and performance

High-bandwidth services from mobile operators using fast cellular technologies offer better audio quality and a bigger coverage area than those using Wi-fi, but they can also cost more.

Wi-fi can be less expensive, but the call quality isn’t as good and service is available only within an access point’s relatively small coverage area, which is 100 meters with the IEEE 802.11g stan-dard and will be 250 meters with the upcoming IEEE 802.11n standard.

“Wi-fi connectivity is prevalent but not pervasive,” said Angl.

Thus, organizations must balance per-formance and cost when deciding which mVoIP approach to use.

FUTURE PROSPECTSEducation will be necessary to

encourage mVoIP adoption, said Chanse Harrington, Nokia’s services sales man-ager for North America.

Providers must demonstrate where,

especially in these difficult economic times, mVoIP can save companies money or provide other benefits, he explained.

Added Schatt, “Interoperability will improve and give enterprises more choices to make mVoIP work.”

Currently, he noted, there is limited interoperability between different ven-dors’ Wi-fi-based mVoIP equipment. With greater interoperability, he said, companies could buy whichever phones, access points, and PBX equipment they want.

For mVoIP to succeed, users will need simpler tools, particularly those for automatically recognizing and handing off calls between differing types of net-works without interrupting the session.

More bandwidthmVoIP will need more bandwidth

to provide the performance necessary for it to become more popular in the enterprise.

IEEE 802.11n. In the near future, mVoIP providers hope to use the upcom-ing, fastest Wi-fi version—the proposed IEEE 802.11n standard, slated for approval next year but already available in prestandard products.

The technology’s theoretical maxi-mum data rate is 248 megabits per second and its theoretical maximum outdoor transmission range is 250 meters.

However, the technology would cause devices’ radios to use considerable power, requiring batteries with longer life.

According to Rod Nelson, princi-pal of the Nelson Technology Partners consultancy, service providers and manu-facturers such as Digium and Polycom are now building Wi-fi networks and equip-ment that feature higher bandwidth and more-efficient packet routing.

WiMax. Carriers may use mobile WiMax for more bandwidth in the

and accounting management for devices using network services.

The technology also uses the IETF’s secure Real-Time Transport Protocol and Transport Layer Security standards, according to Jajah’s Efrati.

Some providers, such as Fring and Skype, encrypt all data involved in mVoIP calls.

HOLDING BACK ADOPTIONSeveral factors have held back cor-

porate mVoIP adoption and threaten to continue doing so.

For example, in-office or in-home mVoIP approaches generally aren’t mature enough to include support for more complicated applications such as conference calling, noted ABI Research analyst Stan Schatt.

Also, said Avaya’s LeClair, businesses that run mVoIP through a service provid-er’s servers, rather than their own, can’t keep the detailed call-tracking records that some government regulations require for business-expense-verification and other purposes.

According to Fring’s Zilberman, because mVoIP runs over the public Inter-net, it doesn’t always provide predictable call connectivity or quality.

Schatt said mVoIP encryption keeps call theft from being a major problem. However, he noted, the disruption of calls by bombarding the network with denial-of-service traffic is a concern.

Tole Hart, analyst with market research firm Gartner Inc., said cellular providers fear the effect that low-cost mVoIP could have on their telephony business. In some cases, they have tried to block mVoIP transmissions over their networks.

Call qualityA concern is whether Wi-fi- and

WiMax-based mVoIP will be able to ensure that voice packets get priority over data packets to ensure low latency and minimal packet loss, said Jeff Bak, direc-tor of marketing for mobile and enterprise voice services for network-services pro-vider Tata Communications.

When this doesn’t occur, Wi-fi-based mVoIP calls can experience signal latency

mVoIP promises cost savings and thus is an appealing prospect for many companies.

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compUtEr 18

Industry trends

order, according to Adam Charles Powers, Vyke’s head of business development.

“Mobile VoIP will definitely account for less than 5 percent of all mobile voice traffic through 2012,” said Hart. “But 50 percent of all wireless traffic will be mVoIP by 2019.”

However, he added, market success will depend on whether people want to communicate this way, how easy mVoIP is to use, and whether the user experience is something that people like.

David Geer is a freelance technology writer based in Ashtabula, Ohio. Con-tact him at david@geercom.com

of throughput and 10 miles of transmis-sion range.

However, the GSM-based LTE won’t be fully deployed for five to eight years, according to Gartner’s Hart. LTE will only begin rolling out in 2010, he said.

M obile VoIP may become an important service in the coming years as device manufacturers exploit more-powerful

processors and cheaper memory. Faster processors and cheaper memory will enable conference calls, voice encryp-tion, the use of compressed codecs, and video calls, assuming there are also fast networks, explained Jajan’s Efrati.

Faster processors allow better real-time compression, encryption, and transmission of voice streams. Increased memory allows a larger buffer to com-pensate for voice packets that arrive out of

future. The point-to-multipoint tech-nology works with multiple receivers, generally based in add-on cards, and multiple transmission towers.

The technology offers a theoretical maximum throughput of 75 megabits per second, with the next version promising up to 1 Gbps, and a theoretical maximum range of 50 kilometers for fixed imple-mentations and 15 kilometers for mobile uses. Utilizing higher data rates shortens the transmission range.

WiMax services are commercially available now from carriers such as Clearwire and Sprint Nextel in the US, and Sumitomo in Japan, said Nemertes Research president Johna Till Johnson.

Currently, though, the technology is only minimally deployed, noted Scott Bell, chief technology officer of Alianza, a provider of hosted voice-over-WiMax services.

LTE. Cellular carriers also may look to Long-Term Evolution, which promises a theoretical maximum of up to 326 Mbps

Editor: Lee Garber, Computer, l.garber@computer.org