VoIP and EV-DO Revision A

By: BY PAUL CALLAHAN, AIRVANA INC.
( 1 Mar 2007 )

VoIP has become mass-market technology through the widespread availability of always-on cable and DSL broadband Internet access. ButVoIP is about to arrive in the mobile broadband market. How?

Mobile VoIP phones—In 2007, a new class of mobile phones will arrive supporting VoIP instead of circuit technology. Mobile phones will offer IP-based push to talk, VoIP, andother integrated voice and multimedia applications.

Rev A is designed for VoIP—and multimedia applications with quality of service (QoS), high capacity reverse link, low latency air link, fast call setup, reduced packet overhead, and rapid handoff. In short, Rev A will be faster, higher quality, and lower-cost than any previous generation of mobilenetwork.

MOBILE VOIP—NEW APPLICATIONS & SERVICES
As Rev A networks roll out around the world, EV-DO will become an ideal platform to provide ubiquitous communications and entertainment experiences on the move—and on multiple IPenabled devices (cell phone, laptop, or PDA). Newmobile VoIP applications include:

Push to Talk (PTT)—Push-to-Talk with subsecond call setup and Push-to-Conference with fullduplex Push-to-Talk;

IM—Instant messaging with integrated voiceand video, application sharing, and file transfer;

Video Telephony—Simultaneous voice andvideo, mobile-to-mobile, with low delay.

The first widespread mobile VoIP application will be PTT. Sprint has chosen Rev A as the technology to migrate millions of iDEN subscribers to a more scalable version of PTT based on IP. Sprintʼs offering will use an optimized version of PTT, Qualcommʼs QCHAT, with very fast call set-up times. Coupled with QCHAT, Rev A will be the first cellular network to deliver sub-second call set-up for Push-to-Talk. Because PTT operates on an end-to-end basis, network-wide adoption of Rev A is required and will establish Rev A as the first proven network for scalable multimedia services. PTT and other IP-based services use a number of underlying capabilities which are only available via VoIP. One of them is context awareness. VoIP allows users to display their context. Users can choose to publish whether they are busy, off-line, not taking calls, have calls forwarded to another device, in a meeting, driving, only reachable by certain people, what device they are currently reachable on, their location, or who else is on a conference call (see Figure 1). This context awareness enables and enhances a whole class of emerging next generationof mobile applications.

HIGHER CAPACITY WITH MOBILE VOIP
Technology advances in CDMA now allow manufacturers to offer higher capacity Rev A modules at a unit cost that is roughly equivalent to older, lower capacity 1xRTT. In addition, VoIP overRev A offers:

Higher voice capacity than 1xRTT—Todayʼs circuit-based 1xRTT supports a practical maximum of 27 simultaneous voice users per sector (per 1.25MHz of channel) with an acceptable mouth-toear delay of 290ms. VoIP over Rev A supports 40 to 60 simultaneous users, a 48% to 120% increase invoice capacity over 1xRTT.

Higher quality than 1xRTT— Circuit-based 1xRTT delivers 290ms ear-to-mouth delay, but Rev A supports better quality overall under a variety of conditions. For example, with 27 simultaneous users—the equivalent of 1xRTTʼs maximum capacity—Rev A provides voice latency as low as215ms (see Table 1).

TIPPING THE BALANCE TO PACKET
As mobile VoIP handsets come to market, 1xRTT will become a less profitable means to offer voiceservices. Why?

Voice average revenue per user (ARPU) continues to drop—Operators continue to report the decline of voice revenue per user. For example, KDDI reports strong growth in data service ARPU, but a decline in voice. As a result, dollars invested in 1xRTT equipment will result in lower profit marginfor operators.

Voice minutes continue to climb—Flat-rate voice pricing plans are increasing mobile minutes of use (MoU) per month. Leap Wireless reports that 52% of their customers talk an average 1,500 MoU per month. And T-Mobile reports that their customers talked an average of 1,013 minutes permonth in Q1 2006.

Data is attracting higher ARPU customers— Newer, higher paying customers are attracted to broadband data. In the overall operator revenue mix, voice will increasingly give way to data. Verizon Wireless, for example, reports a relatively flat ARPU for combined voice and data, but rapidgrowth in data ARPU.

THE FUTURE—4G AND VOIP
Rev A will enable mobile networks to offer a wide range of multimedia applications and rapid service creation—all with the highest capacity and lowest cost. But the real issue for operators is the future ofmobile broadband.

Operators world-wide are considering moving their networks to 4G technologies such as Rev C, LTE, and WiMAX. All of these airlink technologies have a common problem. None of them will support traditional circuit-voice architectures. All of the 4G RANs under consideration will require VoIP to deliver voice. As CDMA operators roll out mobile VoIP on Rev A, they will likely derive a significant time and competitive advantage via their experiencewith VoIP applications and services.