1,790 research outputs found
Energy Efficient Beamforming Design for MISO Non-Orthogonal Multiple Access Systems
When considering the future generation wireless networks, non-orthogonal
multiple access (NOMA) represents a viable multiple access technique for
improving the spectral efficiency. The basic performance of NOMA is often
enhanced using downlink beamforming and power allocation techniques. Although
downlink beamforming has been previously studied with different performance
criteria, such as sum-rate and max-min rate, it has not been studied in the
multiuser, multiple-input single-output (MISO) case, particularly with the
energy efficiency criteria. In this paper, we investigate the design of an
energy efficient beamforming technique for downlink transmission in the context
of a multiuser MISO-NOMA system. In particular, this beamforming design is
formulated as a global energy efficiency (GEE) maximization problem with
minimum user rate requirements and transmit power constraints. By using the
sequential convex approximation (SCA) technique and the Dinkelbach's algorithm
to handle the non-convex nature of the GEE-Max problem, we propose two novel
algorithms for solving the downlink beamforming problem for the MISO-NOMA
system. Our evaluation of the proposed algorithms shows that they offer similar
optimal designs and are effective in offering substantial energy efficiencies
compared to the designs based on conventional methods.Comment: Accepted at IEEE Transaction on Communicatio
Energy-efficiency for MISO-OFDMA based user-relay assisted cellular networks
The concept of improving energy-efficiency (EE) without sacrificing the service quality has become important nowadays. The combination of orthogonal frequency-division multiple-access (OFDMA) multi-antenna transmission technology and relaying is one of the key technologies to deliver the promise of reliable and high-data-rate coverage in the most cost-effective manner. In this paper, EE is studied for the downlink multiple-input single-output (MISO)-OFDMA based user-relay assisted cellular networks. EE maximization is formulated for decode and forward (DF) relaying scheme with the consideration of both transmit and circuit power consumption as well as the data rate requirements for the mobile users. The quality of-service (QoS)-constrained EE maximization, which is defined for multi-carrier, multi-user, multi-relay and multi-antenna networks, is a non-convex and combinatorial problem so it is hard to tackle. To solve this difficult problem, a radio resource management (RRM) algorithm that solves the subcarrier allocation, mode selection and power allocation separately is proposed. The efficiency of the proposed algorithm is demonstrated by numerical results for different system parameter
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