Nextel to trial IPWireless 3G in Washington DC


Nextel will trial IPWireless’ UMTS TD-CDMA mobile broadband solution in Washington, DC and several surrounding areas, marking the first time a major US mobile operator has selected the 3G standard to deliver wireless broadband services. Nextel will deploy the technology in its 2.5 GHz spectrum to provide select users with always-on, multi-megabit wireless data connectivity. Interesting development given that Nextel had also worked with Flarion. This announcement tells me that Sextel will be looking to leverage its “spectrum assets” to big a player in the last mile connectivity.


Jesse Kopelman

Ed, don’t buy too heavily into the Flarion hype. Theoretical channel throughput is based on modulation which is in and off itself a factor of received signal strength vs. noise. According to their web site, IPWireless has a maximum modulation of 16QAM which yields 6 Mbps in a single 5 MHz channel. The Nextel figure of 1.5 Mbps is being conservative and realistic, as it is very hard to insure the link quality necessary for 16QAM. Also keep in mind that a simple bits/Hz type analysis using the best modulation for a single channel is a gross oversymplication of the overall system throughput, which is highly dependent on reuse schemes (note that IPWireless is CDMA vs. TDMA for Flarion which further complicates things). While I’d not be surprised to see Flash-OFDM outperform TD-UMTS in a real world build-out, I don’t think it would be as dramatic as you expect.

As for why you need a dual-mode terminal: I wouldn’t think they would want the networks to be as separate as you assume. The whole point in using TD-UMTS over some pre-WiMax is that TD-UMTS supports full mobility right now. If all Sprint/Nextel wanted was a fixed wireless network, there are far more cost effective options on the market. I’m imagining the concept is more like Verizon or Cingular where you use 800 MHz in some places, 1900 MHz in others, and both where you have the spectrum. Considering that you can run CDMA2000 and UMTS off of the same switches if they are 3GPP2 compliant, why not do it?

Ed Richards

I think that’s about the only advantage, if it’s even that big of a deal.

“IPWireless noted the trial will use a 10-megahertz spectrum channel with average throughput of 1.5 megabits per second on the downlink and 500 kilobits per second on the uplink.”

Given that Flarion can run at average throughput of 6 megabits per second vs. 1.5Mbps and does it with half the spectrum (5MHz channel vs. 10MHz) it looks like Nextel/Sprint will be wasting a lot of capacity to ensure network compatibility with an inferior service if they ultimately go this route.

Why dual mode anyway? They will probably use CDMA/EV-DO for voice and limited mobile data (think handsets) in 1.9 GHz spectrum, and use the 2.5GHz/MMDS for higher-speed cable/DSL replacement (think laptops/PCs). Since they will have nationwide coverage for both, they won’t need cross-network roaming for backfill of dead spots.

Jesse Kopelman

I would think the advantage of IPWIreless over Flarion is that a dual mode FD/TD-CDMA terminal seems pretty likely while a CDMA/Flash-OFDMA device does not.

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