Multi-unit Budget Feasible Mechanisms for Cellular Traffic Offloading

Cellular traffic offloading is nowadays an important problem in mobile networking. Since the offloading resource owners (agents) are self-interested and have private costs, it is highly challenging to design procurement mechanisms that motivate agents to reveal their true costs and achieve guaranteed performance under the constraint of a strict budget. In this paper, we model cellular traffic offloading as a multi-unit budget feasible procurement auction design problem with diminishing return valuations. We design a novel greedy-based randomized mechanism, and prove it is budget-feasible, truthful, individually rational and a $(3+2ln N)$-approximation, where N is the total number of available resource units. We also propose a deterministic mechanism which achieves $(2+ln N + \sqrt2+3ln N +ln^2N )$ - approximation. We prove no budget-feasible and truthful mechanism can do better than $ln N$-approximation in our setting, thus our mechanism approaches the optimal to a constant factor. In addition to solving the cellular traffic offloading problem, our work successfully extends solvable valuation class of greedy-based multi-unit budget-feasible mechanism with performance guarantees from the concave-additive valuations to more general local diminishing return valuations.