The increasing traffic demand in cellular networks has recently led to the investigation of new strategies to save precious resources like spectrum and energy. A possible solution employs direct device-to-device (D2D) communications, which is particularly promising when the two terminals involved in the communications are located in close proximity. The D2D communications should coexist with other transmissions, so they must be careful scheduled in order to avoid harmful interference impacts. In this paper, we analyze how a distributed context-awareness, obtained by observing few local channel and topology parameters, can be used to adaptively exploit D2D communications. We develop a rigorous theoretical analysis to quantify the balance between the gain offered by a D2D transmission, and its impact on the other network communications. Based on this analysis, we derive two theorems that define the optimal strategy to be employed, in terms of throughput maximization, when a single or multiple transmit power levels are available for the D2D communications. We compare this strategy to the state-of-the-art in the same network scenario, showing how context awareness can be exploited to achieve a higher sum throughput and an improved fairness.
Conversely, we create a distributed situational awareness by proper observations of some channel parameters, and exploit it through our analytical results to choose when and how a D2D connection can be established. We have already investigated the concept of situational awareness in a multi-cell scenario in @cite_19 . In that work, however, context awareness is based on statistical information, and decisions are taken based on the output of properly designed Bayesian Networks, without seeking to find the optimal solution.
@cite_19
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Device-to-device (D2D) communication is one of the most promising solutions to the dramatic increase of wireless networks traffic load. In D2D communications, mobile nodes can communicate in a semi-autonomous way, with minimal or no control by the base station (BS). In this context, we address the problem of the coexistence of cellular and D2D tiers in the uplink frequencies, where a D2D source is allowed to transmit without direct control of its scheduling by the base station (BS). In order to limit the interference, we add a punishment mechanism triggered by the BS to limit the activity of disturbing terminals. We propose a context- aware channel access mechanism for a D2D source, where the context-awareness is obtained by 1) observing the topology and the wireless transmissions in the proximity of the D2D source, and 2) exploiting the past knowledge learned thanks to a Bayesian network approach. To design the channel access mechanism, we study the tradeoff between maximizing the end-to-end throughput and minimizing the interference to the cellular tier. We then evaluate the performance improvement of the proposed solution, showing the effectiveness of the learning mechanism and the advantages of context awareness.