Question: what happens if a PC has both WiMAX and 3G/LTE?

This post is a question, rather than an opinion.

There seem to be two clear trends:

- An increasing % of PCs will have 3G radios, either with internal modules or external dongles
- A small number of PCs now have integral WiMAX and there are also dongles emerging. This will also increase, although it's certainly a lagging trend at present.

We know that vendors like Ericsson, Qualcomm, Huawei and peers are continuing to be aggressive on both 3G module and dongle pricing, as are mobile operators.

And based on past history, we can be fairly confident that Intel is going to price its combined WiFi/WiMAX modules at a level to encourage uptake versus plain WiFi, especially when bundled with its processors. When Intel first launched Centrino in 2003, the extra cost of WiFi was $20 above the standalone processor price. Its initial WiMAX+WiFi modules are $24 more than standalone (802.11n) WiFi. WiMAX dongles will probably fall rapidly in cost too.

In other words, it's seems quite possible that we'll see PCs with WiFi, WiMAX, HSPA and (with Qualcomm Gobi) possibly EVDO as well.

At present, 3G and WiMAX operate in different bands - WiMAX at 2.5GHz (or occasionally 2.3GHz or 3.5GHz), with 3G at 850/900/1900/2100MHz.

At some point, we'll also see 2.5GHz bands for LTE and HSPA, and possibly also other mixed "technology neutral" bands thanks to various ongoing regulatory efforts by the likes of Ofcom and CEPT. But for now, I think we can be safe that we won't get dual radios in the same band.

What's really opaque to me are a few issues:

• Will 2.5GHz TDD WiMAX and 2.1GHz FDD 3G interfere significantly if both radios are on simultaneously? (Possible with 2.4GHz WiFi and Bluetooth too).
• Are there any connection managers that can handle all of these, or will such "dual WWAN" PCs end up with multiple bits of software? Early reports suggest the current software experience on Xohm is a bit clunky.
• Are there any technical or commercial reasons (apart from outright cost) to stop OEMs putting both WiFi/WiMAX and 3G modules in the same notebook? Does it need more complex antennas?
• What happens if you have an embedded-3G notebook with a WiMAX dongle, or vice versa?
• Is it possible to create a combined HSPA/WiFi module which *doesn't* need a SIM card inserted for authenticating the WiFi?

(Before anyone else mentions it, yes I know that having 4 radios on simultaneously is a great way to kill the battery, irrespective of anything else).

If people are prepared to pay the extra $50-100 for a 3G module today... and if it's going to fall to $30 or more in a couple of years' time.... then presumably a fair proportion will then be willing to pay an extra $15 (say) to have WiMAX too, especially if they expect to travel to places where there are competing networks.