Abstract-Fog computing is a promising architecture to provide economic and low latency data services for future Internet of things (IoT)-based network systems. It relies on a set of lowpower fog nodes that are close to the end users to offload the services originally targeting at cloud data centers. In this paper, we consider a specific fog computing network consisting of a set of data service operators (DSOs) each of which controls a set of fog nodes to provide the required data service to a set of data service subscribers (DSSs). How to allocate the limited computing resources of fog nodes (FNs) to all the DSSs to achieve an optimal and stable performance is an important problem. In this paper, we propose a joint optimization framework for all FNs, DSOs and DSSs to achieve the optimal resource allocation schemes in a distributed fashion. In the framework, we first formulate a Stackelberg game to analyze the pricing problem for the DSOs as well as the resource allocation problem for the DSSs. Under the scenarios that the DSOs can know the expected amount of resource purchased by the DSSs, a many-to-many matching game is applied to investigate the pairing problem between DSOs and FNs. Finally, within the same DSO, we apply another layer of many-to-many matching between each of the paired FNs and serving DSSs to solve the FN-DSS pairing problem. Simulation results show that our proposed framework can significantly improve the performance of the IoT-based network systems.

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Ambient backscatter communication technology has been introduced recently, and is then quickly becoming a promising choice for self-sustainable communication systems as an external power supply or a dedicated carrier emitter is not required. By leveraging existing RF signal resources, ambient backscatter technology can support sustainable and independent communications and consequently open up a whole new set of applications that facilitate Internetof-Things (IoT). In this article, we study an integration of ambient backscatter with wireless powered communication networks (WPCNs). We first present an overview of backscatter communication systems with an emphasis on the emerging ambient backscatter technology. Then we propose a novel hybrid transmitter design by combining the advantages of both ambient backscatter and wireless powered communications. Furthermore, in the cognitive radio environment, we introduce a multiple access scheme to coordinate the hybrid data transmissions. The performance evaluation shows that the hybrid transmitter outperforms traditional designs. In addition, we discuss some open issues related to the ambient backscatter networking. Index TermsAmbient backscatter communications, modulated backscatter, RF energy harvesting, self-sustainable communications, wireless powered communications, Internet-of-Things. I. INTRODUCTIONInformation transmission based on modulated backscatter of incident signals from external RF sources has emerged as a promising solution for low-power wireless communications. The power consumption of a typical backscatter transmitter is less than 1 µW [1], which renders excessively long lifetime, e.g., 10 years, for an on-chip battery. This low power consumption well matches the harvestable wireless energy from RF sources, e.g., typically from 1 µW to tens of µW [2], [3]. This additionally renders RF energy harvesting to be an alternative to power backscatter transmitters. Furthermore, backscatter communications Dong In Kim is the corresponding author 2 can be embedded into small gadgets and objects, e.g., a radio frequency identification (RFID) and passive sensor. Therefore, backscatter communications is also envisioned as the last hop in the Internet-of-Things (IoT) [4], which requires low cost and ubiquitous deployment of small-sized devices [5].Due to recent dramatic increases in application demands, the requirement for backscatter communications has gone beyond the conventional RFID towards a more data-intensive way. This strongly raises the need for re-engineering backscatter transmitters for better reliability, higher data rates, and longer interrogation/transmission range. However, traditional backscatter communication techniques, e.g., RFID, are hindered by three major shortcomings: 1) The activation of backscatter transmitters relies on an external power supply such as an active interrogator (also called a reader or carrier emitter) which is costly and bulky.2) A backscatter transmitter passively responds only when inquired by a reader. The communication link ...

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We consider the spectrum sharing problem between a set of device-to-device (D2D) links and multiple co-located cellular networks. Each cellular network is controlled by an operator which can provide service to a number of subscribers. Each D2D link can either access a sub-band occupied by a cellular subscriber or obtain an empty sub-band for its exclusive use. We introduce a new spectrum sharing mode for D2D communications in cellular networks by allowing two or more D2D links with exclusive use of sub-bands to share their sub-bands with each other without consulting the operators. We establish a new game theoretic model called Bayesian non-transferable utility overlapping coalition formation (BOCF) game. We show that our proposed game can be used to model and analyze the above spectrum sharing problem. However, we observe that the core of the BOCF game can be empty, and we derive a sufficient condition for which the core is non-empty. We propose a hierarchical matching algorithm which can detect whether the sufficient condition is satisfied and, if it is satisfied, achieve a stable and unique matching structure which coincides with the overlapping coalition agreement profile in the core of the BOCF game. .sg) L. A. DaSilva is with CTVR, Trinity College Dublin, Ireland (e-mail: dasilval@tcd.ie). L. A. DaSilva is also with Virginia Tech, VA, USA.infrastructure (e.g., base station) even when the sources and destinations are close to each other. This not only increases communication delay and energy consumption but also reduces the reliability of the networks. For example, in cellular networks, failure of a base station can lead to mobile service outage for the entire coverage area of the corresponding cell. Device-to-device (D2D) communication without relying on the base station to forward the traffic provides an efficient way to increase the network capacity and reliability. Another issue is that the traditional exclusive spectrum ownership model used in existing cellular networks has resulted in inefficient spectrum utilization for a significant portion of the time [2], [3]. One technique that promises to address this problem is spectrum sharing, which allows under-utilized licensed spectrum to be shared by unlicensed devices. Allowing both D2D communication and spectrum sharing in cellular networks can improve network capacity, reliability and spectrum utilization efficiency. However, D2D links are generally established autonomously and cannot be fully controlled by the base station. In addition, choosing the wrong spectrum sharing pair of D2D links and cellular subscribers can result in high cross-interference, which may adversely affect both D2D links and cellular subscribers.This motivates the work in this paper, where we investigate the joint optimization of spectrum sharing approaches and sub-band allocation problem for a set of D2D links in an area with multiple co-located cellular networks. Each cellular network is controlled by an operator. We propose a general analytical framework in which each D2D link...