In this paper, we investigate the aggregated model quality maximization problem in hierarchical federated learning, the decision problem of which is proved NP-complete. We develop the mechanism MaxQ to maximize the sum of local model quality, which consists of two stages. In the first stage, an algorithm based on matching game theory is proposed to associate mobile devices with edge servers, which is proved able to achieve the stability and 1 2 -approximation ratio. In the second stage, we design an incentive mechanism based on contract theory to maximize the quality of models submitted by mobile devices to edge servers. Through thorough experiments, we analyse the performance of MaxQ and compare it with the existing mechanisms FAIR and EHFL, under different deep learning models ResNet18, ResNet50 and AlexNet, individually. It is found that the model quality can be improved by 8.20% and 7.81%, 10.47% and 11.87%, 10.98% and 11.97% under different models, respectively.
Computation offloading is a hot research topic in mobile edge computing (MEC). Computation offloading among multiedge nodes in heterogeneous networks can help reduce offloading cost. In addition, the unmanned aerial vehicles (UAVs) play a key role in MEC, where UAVs in the air communicate with ground base stations to improve the network performance. However, limited channel resources can lead to the increase of transmission delay and the decline of communication quality. Effective channel selection mechanisms can help address those issues by improving transmission rate and ensuring communication quality. In this paper, we study channel selection during communication between multiple UAVs and base stations in an MEC system with heterogeneous networks. To maximize the transmission rate of each UAV user, we formulate a channel selection problem and model it as a noncooperative game. Then, we prove the existence of Nash equilibrium (NE). In addition, we design a multiple UAV-enabled transmission channel selection (UTCS) algorithm to obtain the equilibrium strategy profile of all the UAV users. Experimental results validate that UTCS algorithm can converge after a finite number of iterations and it outperforms random transmission algorithm (RTA) and sequential transmission algorithm (STA).
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