In this article, we discuss a spectrum trading
mechanism implemented by the spectrum broker
in TV whitespaces. TVWS are spectrum frequency
bands unused by DTV, interleaved in
both frequency and space. Underutilization of
these bands results from the fact that the DTV
transmission systems now operational in the
spectrum from 470 to 790 MHz are multifrequency
systems employing high tower and high
power network geometries, and must be managed
for interference between transmitters. We
motivate the use of a spectrum broker, an entity
that manages the TVWS secondary spectrum
market. Such a TVWS broker’s responsibilities
include planning the possible broad uses of the
available spectrum in the TVWS; packaging the
spectrum for short-term disposal through trading
mechanisms; serving the broker’s customers,
with spectrum-leasing contracts; and acting as
the port of call to handle interference caused by
its customers to the primary DTV systems or
between its customers themselves. We discuss
the spectrum broker’s merchant and auction
modes for spectrum trading. In the merchant
mode, the base price is decided by the allocation
procedure, which considers various factors influencing
the value of TVWS in a given place. In
the auction mode, the customers’ demands and
bids decide the final price of the spectrum. We
discuss the auction design and show results of
the spectrum trading mechanisms, which have
been successfully applied in a real-world test scenario
in the area of Munich, Germany.