San Diego-based Qualcomm, the biggest maker of chips used in mobile phones, said on Tuesday its current structure offered unique strategic benefits that cannot be replicated. Qualcomm, whose earnings have slumped by more than 40 percent in each of the last three quarters, said it expected earnings per share for the current quarter to be at or modestly above the high end of its previously forecast range. Qualcomm’s shares, which have lost almost 40 percent of their value this year, were up 2.3 percent in premarket trading.