"If you're up into the 2100MHz or higher frequencies, which some of them still are with their systems, you're going to be affected by things like buildings and you're not going to get the same outcomes if you were previously on 1800MHz," Gregory says.

"There's frequency reshuffling going on because they're going to want to use as much of the 1800MHz band as possible for the 4G until they can get their hands on the 700MHz."

Optus, Telstra and Vodafone have all taken different approaches when it comes to 4G frequencies.

"Telstra has access to more bands -- more frequency bands -- than others like Optus, so Optus is really desperate to get its hands on 700MHz because it's really giving Telstra a free run," Gregory says.

With the 700MHz spectrum not expected to be operational until 2015, following the Digital Dividend auction in April next year, some telcos are shifting network frequencies, according to Gregory.