Content Retrieval Delay Research Articles

D2D-Aware Device Caching in mmWave-Cellular Networks

In this paper, we propose a novel policy for device caching that facilitates popular content exchange through high-rate device-to-device (D2D) millimeter-wave (mmWave) communication. The D2D-aware caching policy splits the cacheable content into two content groups and distributes it randomly to the user equipment devices, with the goal to enable D2D connections. By exploiting the high bandwidth availability and directionality of mmWaves, we ensure high rates for the D2D transmissions, while mitigating the co-channel interference that limits the throughput gains of the D2D communication in the sub-6-GHz bands. Furthermore, based on a stochastic-geometry modeling of the network topology, we analytically derive the offloading gain that is achieved by the proposed policy and the distribution of the content retrieval delay considering both half- and full-duplex modes for the D2D communication. The accuracy of the proposed analytical framework is validated through Monte Carlo simulations. In addition, for a wide range of a content popularity indicator, the results show that the proposed policy achieves higher offloading and lower content-retrieval delays than existing state-of-the-art approaches.

Optimal Device-Aware Caching

Caches in Content-Centric Networks (CCN) are increasingly adopting flash memory based storage. The current flash cache technology stores all files with the largest possible “expiry date,” i.e., the files are written in the memory so that they are retained for as long as possible. This, however, does not leverage the CCN data characteristics where content is typically short-lived and has a distinct popularity profile. Writing files in a cache using the longest retention time damages the memory device thus reducing its lifetime. However, writing using a small retention time can increase the content retrieval delay, since, at the time a file is requested, the file may already have been expired from the memory. This motivates us to consider a joint optimization wherein we obtain optimal policies for jointly minimizing the content retrieval delay (which is a network-centric objective) and the flash damage (which is a device-centric objective). Caching decisions now not only involve what to cache but also for how long to cache each file. We design provably optimal policies and numerically compare them against prior policies.

A novel hybrid forwarding strategy for content delivery in wireless information-centric networks

Information-centric networking (ICN) is a promising solution for content delivery in multi-hop wireless networks. In these environments, the ICN forwarding strategies typically rely on broadcasting, which facilitates content distribution by taking advantage of the shared medium, but brings about undesirable side effects. To avoid the broadcast-related issues of packet redundancy and unreliability due its unacknowledged mode, a few recent proposals advocated unicasting as the communication mode to resort to, once the content provider has been discovered. However, unicasting may suffer from connectivity breakages due to node mobility and harsh propagation conditions, and, generally, limits the data sharing capability of the wireless medium.In this paper, we design a robust ICN-based forwarding strategy, called Ad Hoc Dynamic Unicast (ADU), that wisely harnesses unicast and broadcast primitives on top of IEEE 802.11-based wireless networks. ADU relies on unicasting for content dissemination after the provider discovery, and promptly falls back to broadcast to find a new content provider in case of a link failure notified by the Medium Access Control (MAC) layer. Extensive simulations in two different multi-hop wireless scenarios, i.e., mobile and vehicular ad hoc networks, under different load settings, assess the ADU performance against benchmark ICN forwarding schemes, representative of broadcast-based and unicast-based solutions. Results show that ADU outperforms them in all circumstances, proving its better responsiveness to link failures, which guarantees a shorter content retrieval delay and a lower message overhead and energy consumption.