Design of Truthful Auction Mechanism for Short-interval Secondary Spectrum Access Market
Date Issued
2015
Date
2015
Author(s)
Zhan, Shun-Cheng
Abstract
Demands for mobile broadband access have increased rapidly because of the developments of portable smart devices, wireless broadband access (WBA) technologies and many new applications. Global mobile traffic is expected to have more than tenfold growth over a few years. Deficiency of spectrum availability for wireless and mobile access emerges as a significant challenge to be conquered worldwide. However, various spectrum usage measurements have indicated that most of the licensed spectrums are lowly utilized or not fully utilized. Secondary spectrum markets that allow spectrum owners to share access rights is a promising approach to better utilize spectrum for wireless communications. In view of the development of dynamic spectrum access (DSA) and cognitive radio (CR) techniques, this dissertation proposes a short-interval secondary spectrum (SiSS) access market that allows primary license holders (PLHs) to rent out unused or lowly utilized spectrum units to a few competing Mobile Virtual Network Operators (MVNOs). The availability of spectrum units for renting ranges from tens of minutes to hours. This dissertation first introduces a design of SiSS market framework with brokerage services that improve market liquidity, mitigate information asymmetry and coordinate the sharing process. In view of the short-interval availability of spectrum, we study single-round and sealed bid auction for spectrum sharing between the PLHs and MVNOs and propose two truthful auction mechanisms. The first is a Vickrey-Clarke-Groves (VCG) auction-based unilateral truthful auction. Key innovations are cumulative bidding format (CBF) and a virtual bidder by the spectrum broker, whose bids are based on PLH’s specification of per-unit reserve price. CBF provides MVNOs with maximal bidding options and allows MVNOs to win part of demands. Introduction of virtual bidder exploits the truthfulness of VCG and further achieves individual rationality and budget balance. The second is a bilateral truthful auction that not only supports PLHs and MVNOs to contribute and purchase multiple spectrum units, but also considers the spatial and frequency heterogeneity of spectrum availability. To exploit spectrum availability in the spatial domain, grouping conflict-free MVNOs and allowing them to share one same spectrum unit is a popular approach for spectrum allocation. However, when MVNOs have diverse demand amounts, such an approach encounters a challenge of how to determine the group bid and make the auction truthful. Our designs have two innovations. The first is the formation of virtual bidding group (VBG) based on MVNO bids. A VBG represents a group of spatially-separated MVNOs bidding on one spectrum unit of a PLH and acts as an entity for bid selection. The second is discriminatory payments by MVNOs that obliges MVNOs in a winning VBG to share the VBG bid as payment. All winning PLHs receive a clearing price for each rented spectrum unit. Integration of the two innovations achieve desirable economic properties of individual rationality, budget balance, PLH truthfulness with respect to per-unit reserve price bid and MVNO truthfulness with respect to demand amount and per-unit bid price. In addition to proving the achievement of desirable economic properties, we provide extensive numerical experimentations for both of unilateral and bilateral auction designs. Numerical experimentations show that unilateral auction generates in average 31.3% higher per-unit revenue to the PLH than VCG. For MVNOs, the design with CBF rents as many spectrum units out as possible and keeps the sample standard deviation of winning quantity lower than 1.5. For a SiSS market of 200 MVNOs and 500 homogeneous spectrum units, computation time of clearing an auction is within 15 seconds, which justifies the feasibility of exploiting short-interval spectrum availability. For the bilateral auction, by enabling conflict-free MVNO to share same spectrum units, although spectrum rent-out ratio is below 0.6 in all test instances, the generated spectrum revenue is higher than the expected revenue by PLHs in about 40%. Comparative analysis between multiple unilateral auctions and one bilateral auction of the same set of available spectrum units and players show that, no matter from the perspective of PLHs or MVNOs, multiple unilateral auctions lead to a higher total utility than the bilateral auction. Compared with bilateral auction that has only 0.568 spectrum rent-out ratio, multi-unilateral auction has 0.936 spectrum rent-out ratio and can truly exploit short-interval spectrum availability, which raises PLHs’ willingness for sharing. For a SiSS market of 15 PLHs and 30 MVNOs, computation times of two designs are both less than one minute but the solution time of multiple unilateral auctions will be longer than the time of bilateral auction. Furthermore, this dissertation designs and implements an online auction platform for SiSS market using a solution stack of Windows-Apache-MySQL-PHP (WAMP). The platform consists of an Apache HTTP server that runs in the background and handles the communication over players, an open-source relational database management system, MySQL, and a server-side scripting language, PHP, to implement the auction algorithms. In addition to demonstration of practicality of our design for application, the online auction platform provides an experimental environment for the human decision.
Subjects
SiSS market
brokerage services
single-round and sealed bid auction
virtual bidder
truthfulness
individual rationality
budget balance
VBG
discriminatory settlement mechanism
online SiSS auction platform
Type
thesis
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