| To satisfy consumer demand for high rate ubiquitous access, research on next-generation cellular networks mostly focused on capacity and coverage. This focus and the resulting advanced technologies, however, bring along a staggering increase in the energy consumption, creating a pressing shift to energy-efficient designs. Within this perspective, relaying has been considered as a promising and cost-efficient technique, and algorithms for optimal relay deployment have attracted significant attention. To date, analysis for relaying energy consumption is mostly based on suboptimal coding schemes or schemes optimized for rate. In this manuscript-based thesis, we investigate the various advantages provided by energy-optimized coding schemes, notably in terms of efficient relay deployment.;To satisfy consumer demand for high rate ubiquitous access, research on next-generation cellular networks mostly focused on capacity and coverage. This focus and the resulting advanced technologies, however, bring along a staggering increase in the energy consumption, creating a pressing shift to energy-efficient designs. Within this perspective, relaying has been considered as a promising and cost-efficient technique, and algorithms for optimal relay deployment have attracted significant attention. To date, analysis for relaying energy consumption is mostly based on suboptimal coding schemes or schemes optimized for rate. In this manuscript-based thesis, we investigate the various advantages provided by energy-optimized coding schemes, notably in terms of efficient relay deployment.;In the first part, we characterize the minimal energy consumption that can be expected from decode-forward relaying. To this end, we design a novel practical half-duplex relaying coding scheme and propose several optimal power allocations to minimize its energy consumption. From a theoretical aspect, an important result is that minimizing the network energy consumption is not equivalent to maximizing the network capacity as often believed. Furthermore, such energy efficiency approach has a certain benefit over the classical maximum-rate approach since it leads to the closed-form solution of the optimal power allocation and allows a comprehensive description of the optimal coding.;In the second part, we explore energy-efficient relay deployment and analyze how the propagation environment, user transmission rate and relay coding scheme affect the choice of relay location and the network performance. We highlight new trade-offs which balance coverage extension, energy consumption and deployment flexibility. We then show that advanced coding schemes can easily overcome harsh radio environments due to suboptimal location, and thus provide a much needed flexibility to the relay deployment.;In the third part, we investigate the maximum energy gain provided by relay stations in shadowing environments, accounting for the relay-generated interference and additional circuitry energy consumption. We propose easily-computable models for the energy-optimized cell area served by relays and define a new performance metric that jointly captures both aspects of energy and interference. We then highlight a trade-off between the relaying energy efficiency and the resulted interference and show that, despite its increased circuitry consumption, the use of partial decode-forward instead of the simple two-hop relaying not only alleviates the interference issue, but also leads to a reduction in the number of relays necessary to reach same performance. |
