Bidding in a government auction of airwaves to be used for mobile broadband has exploded, reaching $34 billion as of Friday afternoon in a sign that companies expect smartphone Internet demands to continue to grow in the coming years.

The bidding has far exceeded presale estimates and become the biggest auction in Federal Communications Commission history, and there is still more bidding to come, according to the New York Times.

Companies are vying for six blocks of airwaves that total 65 megahertz on the electromagnetic spectrum. The FCC put a $10.5 billion reserve price on the sale, but bidders have already more than tripled that total. The auction has no definite end and could last for weeks, meaning the price could rise far higher still. The previous record was for $18.9 billion in 2008.

However, that bidding was for lower frequency waves that were considered more ideal for phones than the current batch. So why has bidding exploded like it has?

It appears to come down to a simple case of supply and demand. In 2008, the iPhone was brand new and demand for mobile broadband was just starting to grow. Today, demand has exploded worldwide. Despite complaints from mobile companies about President Obama’s call for strong net neutrality rules and arguments that they would be less likely to make new investments, the bidding shows that companies do indeed see the need to invest in expansion.

The FCC will use $7 billion from the sale to finance a nationwide public-safety communications network called FirstNet. The rest will go to the Treasury.

Formerly, government agencies including the military used the airwaves, and they were not happy about giving them up or sharing them.

The reason why higher-frequency waves are less desirable for mobile users is that they have difficulty passing through buildings. However, they have the ability to carry lots of data, an increasingly important aspect for smartphones.

The next scheduled auction is in 2016 and will involve lower frequencies. Because that auction has already been delayed twice, it is possible that companies are bidding buy on these frequencies over concerns that the 2016 auction will be delayed again.