1. Introduction

Spectrums are indispensable resources for wireless communication. Propelled by the rapid development of smart devices and 4G technology, the demand for wireless traffic increases exponentially. In 2010, users worldwide downloaded 5 billion mobile applications, 15 times more than the figure (300 million) in 2009. In the U.S., the number of subscribers to mobile services increased by 20 million in 2011 alone, amounting to 294 million. Such a demand will surpass the capacity of allocated wireless spectrums for mobile broadband services by as soon as 2013. To deal with this problem, on the one hand, the regulators are releasing more spectrums for commercial use; on the other hand, secondary spectrum markets emerge where incumbent spectrum licensees lease their spectrums to other service providers. In 2010, the Federal Communications Commission (FCC) in the U.S. decided to make 500 MHz of new wireless spectrum available within ten years. In July 2012, the President’s Council of Advisors on Science and Technology (PCAST) of the U.S. further proposed to identify 1000 MHz of federal spectrum for commercial use. In 2010, the FCC introduced the idea of incentive auction to encourage incumbent spectrum licensees to voluntarily give up their license and get part of the revenue from re-selling their spectrums. Company Spectrum\(^{\textregistered}\) Bridge has launched an online platform called SpecEx for spectrum owners to sell their unused spectrums to potential buyers. Spectrum auction can be an efficient way to reallocate these spectrums, either from the regulators to the wireless service providers or from incumbent spectrum licensees to secondary service providers.