A number of factors will determine when (and which) mobile operators invest in ‘4G’ or OFDM-based wireless technology, whether it is LTE or WiMAX. One of those factors is how far 3G and 3.5G network capacity has been chewed up through increased volumes of data traffic. And if mobile operators are facing a capacity crunch, they will need to have more spectrum at their disposal in order to pursue any 4G business model ambitions they might have.

But how many mobile operators can tick these two boxes: the near-prospect of a 3G/3.5G capacity crunch and access to more spectrum?

Not many. Maybe Verizon and AT&T (if you count their 700MHz spectrum assets as being suitable for rolling out mobile broadband in urban areas). And, of course, there is Sprint Nextel. The mobile operator continues to notch up strong data growth over its 1x EV-DO network and it has ample spectrum assets at 2.5GHz to pursue a Mobile WiMAX strategy via its Xohm business unit.

There is the argument that some mobile operators may not be as spectrally-challenged as they first appear, particularly if they can re-farm their 900MHz spectrum assets for 4G (which would most likely be used for LTE as there is no standardisation work at 900MHz work currently being undertaken by the WiMAX Forum).

But it is still very much open to debate whether mobile operators have a sufficient amount of contiguous spectrum at 900MHz to offer turbo-charged ‘4G’ mobile broadband, particularly in densely-populated areas. The same might be said about 700MHz in the US, although the lower frequencies have cost benefits for rolling out wide area coverage (fewer base stations required).

If the majority of mobile operators would rather try and get an ROI on their HSPA networks over the next few years before splashing out on a spanking new 4G network, which seems a reasonable assumption (unless there are competitive pressures to do otherwise) where is most of the commercial OFDM action going to come from in the near term (the 2008-2011 period)?

This is where the WiMAX camp sees it has an advantage. New market entrants (courtesy of broadband wireless access licence awards), as well as existing wireless licence holders, can disrupt the mobile broadband market now by using OFDM technology that is commercially available now.

This argument will no doubt become stronger if Xohm gains market traction quickly and cautious investors, in the time of an unprecedented global credit crunch, can be enthused. All eyes are on Baltimore.