Due to the huge connectivity and ever-growing demands of diverse services and high data rate applications, more effective radio access techniques are required for the next generation wireless systems. Non-orthogonal multiple access (NOMA) is a promising candidate which has been recognized as an effective multiple access technique that notably improves the spectral efficiency (SE). In addition to SE, energy efficiency (EE) is also attracting too much interest nowadays due to the limited power of end users (EU) and internet of things (IoT) devices, and the strict environmental concerns related to global carbon dioxide (CO2) emission of communication devices. However, in fact there is a trade-off relationship between SE and EE. In this paper, the SE-EE trade-off relationship in NOMA-based systems is mathematically modeled and analyzed. On the other hand, in order to attain an elastic SE-EE trade-off relationship, the problem is formulated as an optimization problem with an objective of maximizing the EE under the constraint of satisfying a minimum SE demand. Simulation results confirmed the theoretical findings of this study and further asserted the validation of the proposed power allocation scheme which aims to achieve a more flexible trad-off relationship between SE and EE.
In this paper, a cloud-radio access networks based (C-RANs) radio-over-fiber (RoF) system have been reported with the optical generation of 28 GHz and 57 GHz millimeter-wave using phase modulation and stimulated Brillouin scattering effect in optical fibers. As a result, a cost-effective system with improved performance is achieved by the proposed method. Based on the proposed scheme, a 28 GHz (licensed band) and 57 GHz (Un-licensed band) optical millimeter-waves are generated by simulation only using 14 GHz and 16 GHz radio frequency (RF) respectively. Because the performance of any optical transmission system is limited by the Q factor and the bit error rate (BER) and any input power of the laser into the fiber needs to be less than the Brillouin threshold in order to avoid the sharp degradation of the Q factor. Also, the Brillouin threshold for this study setup is determined which is around 6 dBm in the case of licensed band and 2 dBm in the case of unlicensed band. The simulation results show that the proposed scheme can provide 100 km single-mode fiber for 28 GHz and 25 km for 57 GHz with transmission rates of 10 Gbps for both of them. In addition, a stable millimeter-wave RoF link, high quality carriers, and a reduction in nonlinearity effects are achieved with the proposed scheme.
The Internet has led to the creation of a digital society, where most of things is connected to it. However, in spite of their popular adoption, current internet networks are complex and very difficult to manage. With the increasing complexity of traditional IP networks, Software Defined Networking (SDN) has been emergent as a new norm of networking that can solve many of current internet network management problems. Introducing the concepts of SDN into the network architecture brought the idea of physical separation of these two planes, pushing up the control planes to the centralized controller of the architecture and leaving the data planes remained on the network elements. This paper is to investigate that if the control plane is physically moved away from the data plane, what impact does this have on the performance as seen by users of the network. Also, the effect of this physical distance resulted from the separation of these two planes on the most famous protocol (OpenFlow protocol) performance is conducted.
ABSTRACTin the curricula of higher education faculties, computer networking is a main topic in computer Science courses. Previous methods of teaching a subject like Computer Networks has consisted of a face to face proposal, high cost labs and static and complex configuration of real networking devices restricted by in location attendance for experiment purposes and in lab work.With computer networks virtualization, Students and researchers are allowed to do tests on real world networking configuration scenarios and to configure various and complex network scenarios by configuring virtualized equipments, such as routers and switches, through virtual consoles and Network virtualization and simulation tools .In this paper an evaluation of the concept of computer networks virtualization and Software Defined Networks is conducted which can be used by the students to improve the learning process of computer networks subject in engineering studies. Emulating the same physical networks as in the laboratory, at home or remotely from anywhere with more flexibility and lower cost, all that through emulation tools installed on students computers.
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