A Monetary Mechanism for Stabilizing Cooperative Data Exchange with Selfish Users.
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In this research, we address the stability issues in Cooperative Data Exchange (CDE), one of the central problems in wireless network coding. We consider a setting in which the users are selfish, i.e., would like to maximize their own utility. More specifically, we consider a setting where each user has a subset of packets in the ground set X, and wants all other packets in X. The users can exchange data by broadcasting coded or uncoded packets over a lossless channel, and monetary transactions are allowed between any pair of users. We define the utility of each user as the sum of two sub-utility functions: (i) the difference between the total payment received by the user and the total transmission rate of the user, and (ii) the difference between the total number of required packets by the user and the total payment made by the user. A rate-vector and payment-matrix pair (r, p) is said to stabilize the grand coalition (i.e., the set of all users) if (r, p) is Paretooptimal over all minor coalitions (i.e., all proper subsets of users who collectively know all packets in X). Our goal is to design algorithms that compute a stabilizing ratepayment pair with minimum total sum-rate and minimum total sum-payment for any given instance of the problem. In this work, we propose two algorithms that maximize the sum of utility of all users (over all solutions), and one of the algorithms also maximizes the minimum utility among all users (over all solutions). The second algorithm requires a broker, where each user has to trust the broker and use the broker to exchange payments, whereas in the first algorithm there is no such requirement. In the first algorithm, the users directly compensate user broadcasting the packet in that particular round. Our scheme minimizes the total number of transmitted packets, as well as the total amount of payments. We also perform an extensive simulation study to evaluate the performance of our scheme in practical setting.