Microsoft takes on Google's Motorola Mobility unit this week in the second of two landmark trials over the patents behind smartphones. The jury trial aims to resolve whether Motorola breached its contract with Microsoft to license standard essential patents, covering wireless and video tech used in the Xbox.

It follows a complex trial last November that decided what the appropriate fee for Microsoft's use of Motorola-patented technology should be. US District Judge James Robart came down heavily in Microsoft's favor, saying it owed only a fraction of the royalties Motorola had claimed. More than Microsoft thought, but much less Motorola's bill for as much as $4 billion a year.

Motorola cannot appeal that ruling until after the jury decides the second phase of the case. In this case Microsoft said that it had offered to pay Motorola $6.8 million in past royalties, based on its application of Robart's order. However, Motorola said no.

Microsoft will argue that Motorola's initial demand was exorbitant and a clear breach of its agreement to charge reasonable and non-discriminatory terms - commonly referred to as 'RAND' - for technology that is an industry standard.