Friday, August 11, 2006

EV-DO Expands In The Face of WiMAX

Third generation or 3G wireless is about to see a 4G or fourth generation technology moving into it's territory. So is it time for a changing of the guard in mobile technology? Yes and No.

The "yes" part is Sprint's commitment to deploy a nationwide WiMAX broadband network with service starting by the end of 2007. WiMAX is the "big daddy" wireless data technology spec'd with a range of up to 31 miles and bandwidth up to 70 Mbps. In practice, many users are expected to experience speeds more on the order of 2 to 4 Mbps, especially in high speed mobile applications.

Now compare that with the current most popular 3G service called EV-DO. Developed by Qualcomm and adopted as a standard for CDMA cellular transmission systems, EV-DO has come to mean "EVolution - Data Optimized." It's a data transmission network that uses cellular phone channels to provide Internet access and video on demand along side traditional cellular voice service. The two big U.S. carriers deploying EV-DO are Verizon which calls their service BroadbandAccess for Internet and VCAST for music and video, and Sprint which calls their service Amp'd Mobile offers EV-DO based entertainment services using the Verizon Wireless network.

EV-DO can rightfully be called broadband. It has a peak forward or download speed of 2.4 Mbps and a reverse or upload speed of 153 Kbps. That compares favorably with other broadband services such as DSL, Cable, and Satellite Internet. In practice, users are likely to see 400 to 700 Kbps download speeds. That's still enough to support text and multimedia messaging, email, Web browsing, and video & audio downloads.

The EVolution part of EV-DO represents a migration from an earlier standard called 1xRTT, which offers typical download speeds of 60 to 80 Kbps. That's better than dial-up Internet service, but not a big pipe for bandwidth hungry applications like video or even streaming audio. The evolutionary concept is vital because 1xRTT is really the only data service available on the entire CDMA networks. EV-DO is still in deployment, with major cities and airports well covered and lower population areas still waiting for service.

Now along comes an upgrade called EV-DO Rev A. This revision is backwards compatible with the baseline release of EV-DO but offers lots of improvements. First is a peak bandwidth expansion from 2.4 to 3.1 Mbps on the forward channel. Even more significant is the peak bandwidth expansion on the reverse channel from 153 Kbps to 1.8 Mbps, a full order of magnitude.

EV-DO Rev A also introduces QoS or Quality of Service support that will reduce latency for delay sensitive applications such as push-to-talk, instant messaging, two-way multimedia and VoIP. VoIP is mentioned as a possible application by Qualcomm, although both Verizon and Sprint have been thumbs-down on use of their current unlimited EV-DO plans for IP telephony. That's understandable, since they also sell the lucrative cellular voice services. Perhaps the QoS features will be useful for something like full motion video conferencing.

Both Sprint and Verizon are busy upgrading their systems to EV-DO Rev A. Meanwhile, the next upgrade, EV-DO Rev B has been approved and is scheduled for commercialization starting next year. Rev B further improves the performance of each 1.25 MHz carrier or cellular channel to a peak forward transmission speed of 4.9 Mbps. Up to 15 carriers can be assigned to work in parallel with Rev B to create a peak forward bandwidth of 73.5 Mbps and a reverse link bandwidth of 27 Mbps. Best of all, Rev B is also backwards compatible with devices designed for Rev A or Rev 0, the EV-DO baseline.

Now, just a second. That 73.5 Mbps seems very similar to the 70 Mbps offered by WiMAX. Is 3G evolving to become 4G? In a way, yes. When the dust settles in a few years, Verizon, Sprint and other CDMA carriers may be faced with a wealth of high bandwidth networks. That's especially good news for Verizon, who doesn't have the same licenses as Sprint Nextel to deploy a separate WiMAX network. It's also very, very good news for wireless applications that are currently constrained from reaching their potential by too-small airlink channels.

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