Migration from distributed to centralized radio access networks (C-RANs) can be expensive in terms of capital expenditures due to the initial investment while it has lower operational expenditures due to pooling baseband processing into the cloud and reduced power consumption. Partial centralization can be also an option by employing network function splitting and keeping lower physical layer functions co-located with the radio units. This increases the power consumption but relaxes the high capacity requirement in the fronthaul. It is not intuitive which migration strategy is more cost effective. In this paper, we formulate a pool placement optimization problem as an integer linear programming (ILP), which minimizes the total cost of ownership (TCO), and evaluate the migration cost to C-RAN with both full centralization of network functions, and partial centralization by using function splitting. We define a network upgrade optimization problem, by adding new cells to the network, as a revisited version of the original optimization problem to evaluate the upgradability of the architectures. We solve the problem with both ILP for optimality, and genetic algorithm for scalability. Simulation results show that partial centralization results in optimal TCO with lower crossover time compared to C-RAN with full centralization. Index Terms-Total cost of ownership, functional splitting, C-RAN, integer linear programming, genetic algorithm.
IoT networks with grant-free radio access, like SigFox and LoRa, offer low-cost durable communications over unlicensed band. These networks are becoming more and more popular due to the ever-increasing need for ultra durable, in terms of battery lifetime, IoT networks. Most studies evaluate the system performance assuming single radio access technology deployment. In this paper, we study the impact of coexisting competing radio access technologies on the system performance. Considering K technologies, defined by time and frequency activity factors, bandwidth, and power, which share a set of radio resources, we derive closed-form expressions for the successful transmission probability, expected battery lifetime, and experienced delay as a function of distance to the serving access point. Our analytical model, which is validated by simulation results, provides a tool to evaluate the coexistence scenarios and analyze how introduction of a new coexisting technology may degrade the system performance in terms of success probability and battery lifetime. We further investigate solutions in which this destructive effect could be compensated, e.g., by densifying the network to a certain extent and utilizing joint reception.
In this paper, we study an energy efficiency maximization problem in uplink for device-to-device (D2D) communications underlaid with cellular networks on multiple bands. Utilizing stochastic geometry, we derive closed-form expressions for the average sum rate, successful transmission probability, and energy efficiency of cellular and D2D users. Then, we formulate an optimization problem to jointly maximize the energy efficiency of D2D and cellular users and obtain optimum transmission power of both D2D and cellular users. In the optimization problem, we guarantee the quality-of-service of users by taking into account the success transmission probability on each link. To solve the problem, first we convert the problem into canonical convex form. Afterwards, we solve the problem in two phases: energy efficiency maximization of devices and energy efficiency maximization of cellular users. In the first phase, we maximize the energy efficiency of D2D users and feed the solution to the second phase where we maximize the energy efficiency of cellular users. Simulation results reveal that significant energy efficiency can be attained, eg, 10% energy efficiency improvement compared to fix transmission power in a high-density scenario.Trans Emerging Tel Tech. 2019;30:e3768.wileyonlinelibrary.com/journal/ett of D2D communications while diminishing the performance degradation of the cellular system due to new sources of interference. In particular, power control is one of the promising approaches that mitigates interference. 5 In the work of Elsawy et al, 6 a power control scheme is proposed to manage the cross-tier interference between cellular and D2D users. Zhang et al 7 proposed an interference-aware algorithm for power control in D2D communications underlaying cellular networks. In the work of Memmi et al, 8 a single-cell D2D underlay cellular network is considered. Centralized and distributed algorithms are proposed to find the users' optimal power transmission. Dynamic power control for a D2D communication underlaying uplink multicell network is investigated in the work of Jiang et al, 9 considering interference mitigation. However, power control is a key technique to manage the interference; both the EE and quality-of-service (QoS) are still influenced by the interference in the network.EE is a metric quantifying the efficiency of resource utilization. In fact, EE not only brings considerable economic benefits into the network but also can be interpreted as concerning about the environment. 10 Extensive research studies have been devoted to the EE of the system. EE maximization in the D2D communication underlaying cellular network in the cloud radio access network is studied by Zhou et al. 1 A closed-form expression for EE is derived in the work of Altman et al 11 by utilizing stochastic geometry tool. In this study, EE is maximized by optimizing the transmit power and density of the BS in cellular networks. An energy-efficient power control algorithm is proposed in the work of Wu et al 12 to share resources among th...
In this paper, the authors deal with secure transmission in two-hop amplify-and-forward network with untrusted relays. To prevent the untrusted relays from intercepting the source message and to achieve positive secrecy rate, the destination-based cooperative jamming technique is used. The authors propose joint secure best relay selection (BRS) and optimal power allocation (OPA) for uplink transmission of a cellular network when the base station is equipped with very large-scale antenna arrays. Then, the common performance metrics such as ergodic secrecy rate (ESR) and secrecy outage probability are evaluated for the optimised network. Moreover, the diversity order and diversitymultiplexing tradeoff of the system are examined. The authors obtain that the diversity order of joint BRS and OPA scenario is equal to number of relays. Finally, some numerical and simulation results are presented to validate the theoretical analysis and to show the advantages offered by the presented systems. They reveal interesting results that, by increasing number of untrusted relay nodes, the system performance improves. For example, for target ESR 2 bits/ s/Hz and ten untrusted relay nodes, the optimised network saves about 5 dB for uplink transmission, in comparison with the system applying the BRS and equal power allocation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.