A Fig. 1. The overall picture of IoT emphasizing the vertical markets and the horizontal integration between them. Remarks:The architectures that borrow their layers and concepts from network stacks (like the three-layer model) do not conform to real IoT environments since, e.g., the ‗Network Layer' does not cover all underlying technologies that transfer data to an IoT platform. In addition, these models have been designed to address specific types of communication media such as WSNs. More importantly, the layers are supposed to be run on resource-constrained devices while having a layer like ‗Service Composition' in SOA-based architecture takes rather a big fraction of the time and energy of the device to communicate with other devices and integrate the required services.

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Caching at the base stations brings the contents closer to the users, reduces the traffic through the backhaul links, and reduces the delay experienced by the cellular users. The cellular network operator may charge the content providers for caching their contents. Moreover, content providers may lose their users if the users are not getting their desired quality of service, such as maximum tolerable delay in Video on Demand services. In this paper, we study the collaborative caching problem for a multicell-coordinated system from the point of view of minimizing the total cost paid by the content providers. We formulate the problem as an Integer Linear Program and prove its NP-completeness. We also provide an online caching algorithm that does not require any knowledge about the contents popularities. We prove that the online algorithm achieves a competitive ratio of O(log(n)), and we show that the best competitive ratio that any online algorithm can achieve is Ω( log(n) log log(n) ). Therefore, our proposed caching algorithm is provably efficient. Through simulations, we show that our online algorithm performs very close to the optimal offline collaborative scheme, and can outperform it when contents popularities are not properly estimated.

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Visible light communication (VLC) has wide unlicensed bandwidth, enables communication in radiofrequency-sensitive environments, realizes energy-efficient data transmission, and has the potential to boost the capacity of wireless access networks through spatial reuse. On the other hand, WiFi provides more coverage than VLC and does not suffer from the likelihood of blockage due to the line-of-sight requirement of VLC. In order to take the advantages of both WiFi and VLC, we propose and implement two heterogeneous systems with Internet access. One is the hybrid WiFi-VLC system, utilizing a unidirectional VLC channel as the downlink and reserving the WiFi backchannel as the uplink. The asymmetric solution resolves the optical uplink challenges and benefits from the full-duplex communication based on VLC. To further enhance the robustness and increase throughput, the other system is presented, in which we aggregate WiFi and VLC in parallel by leveraging the bonding technique in the Linux operating system. We also theoretically prove the superiority of the aggregated system in terms of average system delay. Online experiment results reveal that the hybrid system outperforms the conventional WiFi for crowded environments in terms of throughput and Web page loading time, and also demonstrate the further improved performance of the aggregated system when considering the blocking duration and the distance between the access point and the user device.