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Why a Verizon iPhone will probably not bring the network down

August 13, 2010

There is a lot of talk about Verizon getting the iPhone at the end of 2010 or early 2011.  It is a periodic rumor that has been repeated a number of times during the last couple of years but this time round it seems to have a bit more credibility.

One thing that some commentators keep wondering about is whether the Verizon network would be able to withstand a million iPhone users. This is due to the fact that the biggest complaint about the iPhone has centered around the poor performance of the iPhone on ATT’s network. Indeed this has also been reported in O2’s network in the UK. This has been attributed to the massive amount of data usage that iPhones trigger.

But I believe this is unlikely to be seen in any Verizon iPhone (if it becomes available) because of a fundamental difference in the technology used by the Verizon network (CDMA) compared with ATT (UMTS).

The following is a very simplified explanation of this. To transmit and receive calls from cellular towers all wireless phones use wireless spectrum. In the case of CDMA – the spectrum is cut into 1.25MHz slices, while UMTS uses 5MHz slices. The key difference is that in UMTS, both voice and data signals are sent over the same slice.  In contrast CDMA uses different slices for data and voice.  In addition, similar to the wireless spectrum, the wireless network equipment used is also divided between voice and data in CDMA networks, while in UMTS networks there is a lot of equipment used in common.

So what does this mean ? The main consequence is that in UMTS networks, if a lot of users use data they can potentially overwhelm the usable spectrum and equipment. Effectively “locking out” voice callers or causing them problems in general. On the other hand, in CDMA networks even if there is a huge surge in the data network usage, this will only effect the data users. So while data users may see degraded performance and lower throughput etc. the voice users will not be effected. The end result is that on Verizon’s network the user’s voice calls will in most cases not get effected by users overloading the data side of the wireless network. The data users may see somewhat slower performance but that will not be as noticeable.

(NOTE : The above is an extremely simplified explanation. I can go into them if you contact me.)

There of course many other issues that may also be behind the poor performance of the networks such as O2 in UK and ATT in the US. These include

  • lack of backhaul bandwidth
  • lack of spectrum
  • iPhone phone software issues

As far as I know all operators are addressing the first two as quickly as possible.  So I can’t say if Verizon would be in a better position than ATT with respect to these issues.

Regarding the last possible cause – if there is a fundamental issue with the software on the iPhone phone software than you may see the same issues even on a Verizon network as you see on the ATT network. Indeed, there are many reports that other phones on the ATT networks do not see the dropped calls and poor call quality that is seen by iPhone users.  So there may be something in this.

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