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EasyBid: Enabling Cellular Offloading via Small Players. Zhixue Lu 1 , Prasun Sinha 1 and R. Srikant 2. 1 The Ohio State University 2 Univ . of Illinois at Urbana-Champaign. Cellular Data Keeps Increasing. Mobile Data Increases more than 60% Annually
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EasyBid: Enabling Cellular Offloading via Small Players Zhixue Lu1, Prasun Sinha1 and R. Srikant2 1The Ohio State University 2Univ. of Illinois at Urbana-Champaign
Cellular Data Keeps Increasing • Mobile Data Increases more than 60% Annually • Small Cells (Femtocells) Increase Spectrum Reuse
Femtocells: the Concept • Small in-home Cellular Base Station • connects to the service provider’s network through owner’s broadband network Femtocell Internet Femtocell Gateway Broadband Router Core Network
Femtocells: the Facts • To Deploy Cellular Base Stations • Site, Backbone and Power Supply • Costly to deploy • 7.9 Million Femtocells Deployed by 2013 • Almost all are residential and enterprise (small owners) Femtocells • Acquiring Access to these Femtocells is Important
Proposed Incentive Mechanism: Auction • Why Auction? : Fair and Efficient • Two Types of Auctions • Forward Auction: buyers bid • Reverse Auction: sellers bid • Consider a Reverse Auction Model • Buyer: the wireless service provider (WSP) • Sellers: the femtocell owners • Reason: most owners have only one femtocell
Background • Desired Properties of Auctions • Truthfulness: bidders cannot get higher utility by lying • Individual Rationality: utility of any bidder ≥0 • Common Auction Mechanisms • Secondary price auction • Reserve price based secondary auction
Imprecise Valuation: an Ignored Problem • Existing Works Assume Precise Valuations • Valuations of Femtocell Owners Depend On: • Cost of extra broadband traffic, electricity usage • Degree of overload/delay tolerance • Wiliness to provide service • May vary over time • Hard to Precisely Estimate = ? + + No Delay!
Assumptions • Sellers Can Estimate With Bounded Errors • : True Valuation of f, Hidden Value • : Perceived Valuation of f, Exposed Value • Distribution of is known • Truthful Auctions: Sellers Submit Perceived Valuations Truthfully
Basic Form of Auctions in the Paper • Consider Reserve-Price based Secondary Auction • Secondary auction: truthful with precise valuations • Reserve price: eliminate errors (uncertainties) in payments • How It Works • Consider one seller a time • WSP sets a reserve price x • The Femtocell owner places its bid • Auction succeeds and pay x to the owner if the bid ≤ x • Utility of WSP is G-x, G: the savings of the WSP on each unit of data offloading
Negative Utility of Femtocells • Femtocell Owners: Negative Utility when < Payment < • G=14,Uniform in [0,10] ,=2 • Reserve Price: x=$7 • : $8, : $6 • Negative utility: 7-8 = -1 • Individual Rationality Violated 6 10 4 2 0 8
Address Negative Utility Issue (Naïve) • The WSP sets a reserve price $6, payment $8 • Seller f wins and receives $8 if its bid ≤ 6 • Expected Utility of WSP: 3.6 • =3.6 Reserve Price 4 Worst-case IR Payment 6 10 0 8 2 =2
New Issue (Naïve): Imprecision Loss • For Femtocell Owners: • , No loss even if • , Loss if > 6 • , Loss if > 6 No Imprecision Loss Imprecision Loss No Imprecision Loss 4 6 10 0 8 2 Reserve Price Payment • Imprecision Loss(IL): Percentage of utility loss Due to Imprecision: 100%
Problem Definition • M sellers, distribution of valuations known Problem: maximize Subject to: Sellers are comfortable to submit imprecise valuations No Imprecision Loss Imprecision Loss 1. The Worst-case Utility of any seller ≥0 2. Partial Truthfulness: percent do not lose any potential utility by submitting imprecise valuations 3. Imprecision Loss: The expected utility loss for each user (in red) is bounded () No Imprecision Loss 4 6 10 0 8 2 Reserve Price Payment
Solution: Multiple Reserve Prices • Example: 2-reserve-price Approach: Segments: Si S1 S2 10 0 4 • if bid ∈ [0,4), approve and pay $8 • if bid ∈ [4,10], approve with probability 2/3 and pay $10 if it is approved • Truthful and IR with Precise Valuations Approval Ratios: Ri Payments: Pi
Multiple Reserve Prices In Imprecise Valuation Auction • Two Reserve Prices No Imprecision Loss Imprecision Loss No Imprecision Loss S1 S2 0 4 10 6
Algorithm Sketch • Input • (Saving of WSP) • (Estimation Error) • Distribution of • (Constraints) • Output • $N$ Reserve Prices (Si,Ri, Pi, ) • Dynamic Programming based Algorithm: Pseudo-polynomial Time Complexity
Example Seller #2 Seller #4 S1 S2 $6 A $3 C D B $1 0 4 10 E 6 $8 Seller #1 Seller #3
Simulation Result • Precise Valuation • Near Optimal • Imprecise Valuation • Increasing Decreases • DDecreases
Summary • EasyBid: A Reverse Auction Mechanism for Acquiring Access to Femtocells • Introduce the notion of Perceived Valuation, Partial Truthfulness, and Imprecision Loss to characterize the quality of auctions with imprecise valuations. • Present heuristic algorithms to maximize the WSP’s utility while satisfying given constraints on partial truthfulness and imprecision loss.