Ericsson claims Apple is infringing on as many as 41 patents. According to the Bloomberg report:

Together, the complaints accuse Apple of infringing as many as 41 patents for some of the fundamental ways mobile devices communicate and for related technology such as user interfaces, battery saving and the operating system.

Ericsson states they offered a license, which was turned down by Apple. With the court battle kicking off last month, Ericsson has opted to take the dispute to another level to put pressure on Apple, seeking assistance from the ITC to block products from being sold in the region.

Apple had been paying royalties to Stockholm-based Ericsson before a license expired in mid-January. When talks over renewal failed, the companies sued each other, seeking court rulings on whether Ericsson's royalty demands on fundamental technology were fair and reasonable.

The issue around patents covering fundamental technology has caused a split between companies who created and developed basic ways mobile phones operate and parties who utilize said tech in more complex hardware. We'll have to hold off until the courts and ITC come to a conclusion on the matter.

Source: Bloomberg