  Our study provides a survey on how existing stablecoins-- cryptocurrencies
aiming at price stabilization-- peg their value to other assets, from the
perspective of Decentralized Payment Systems (DPSs). This attempt is important
because there has been no preceding surveys focusing on the stablecoin as DPSs,
i.e., the one aiming at not only price stabilization but also decentralization.
Specifically, we first classified existing stablecoins into four types
according to their collaterals (fiat, commodity, crypto, and
non-collateralized) and pointed out the high potential of non-collateralized
stablecoins as DPSs; then, we further classified existing non-collateralized
stablecoins into two types according to their intervention layers (protocol,
application) and confirmed details of their representative mechanisms.
Utilizing concepts such as Quantity Theory of Money (QTM), Tobin tax, and
speculative attack, our survey revealed the status quo where, despite the high
potential of non-collateralized stablecoins, they have no standard mechanism to
achieve the stablecoin for practical DPSs.
