Energy-Efficient Pushing With Content Consumption Constraints: A Network Calculus Approach

Joint pushing and caching (JPC) holds the promise of achieving high spectral and energy efficiency in future networks, thereby attracting much attention most recently. However, few attention has been paid to the content consumption process that describes how a content item leaves the receiver buffer after the request time. Such a process bounds the amount of data that have arrived in the buffer, thereby constraining the content transmission. By taking content consumption processes into account, this paper aims to present optimal JPC policies that minimize the transmission energy under receiver buffer size and content consumption constraints. In particular, two common types of content consumption processes, instantaneous reading and sequential reading, along with two content transmission strategies, orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA), are respectively considered. Energy minimization problems are first formulated as variational problems based on the network calculus approach, and are then equivalently transformed into convex optimization problems in order to reduce the computational complexity. It is shown that JPC policies are capable of significantly reducing the energy consumption when receiver buffer sizes are large. Furthermore, the NOMA based JPC achieves higher energy efficiency than the OMA based JPC by effectively exploiting physical layer multicasting opportunities.