Browsing by Subject "Heterogeneous networks"

Now showing 1 - 7 of 7

Open Access
Activity management algorithm for improving energy efficiency of small cell base stations in 5G heterogeneous networks
(2014) Aykın, Irmak
Heterogeneous networks (HetNets) are proposed in order to meet the increasing demand for next generation cellular wireless networks, but they also increase the energy consumption of the base stations. In this thesis, an activity management algorithm for improving the energy efficiency of HetNets is proposed. A smart sleep strategy is employed for the operator deployed pico base stations to enter sleep and active modes. According to that strategy, when the number of users exceeds the turn on threshold, the pico node becomes active and when the number of users drop below the turn off threshold, it goes into sleep mode. Mobile users dynamically enter and leave the cells, triggering the activation and deactivation of pico base stations. The performance of the system is examined for three different cellular network architectures: cell on edge (COE), uniformly distributed cells (UDC) and macro cell only network (MoNet). Two different user distributions are considered: uniform and hotspot. The effects of number of hotspot users and sleep energies of pico nodes on the energy efficiency are also investigated. The proposed activity management algorithm increases the energy efficiency, measured in bits/J, by 20%. The average bit rates achieved by HetNet users increase by 29% compared with the MoNet architecture. Thus, the proposed activity control algorithm increases the spectral efficiency of the network while consuming the energy more efficiently.
Open Access
Application-specific heterogeneous network-on-chip design
(Oxford University Press, 2014) Demirbas, D.; Akturk, I.; Ozturk, O.; Güdükbay, Uğur
As a result of increasing communication demands, application-specific and scalable Network-on-Chips (NoCs) have emerged to connect processing cores and subsystems in Multiprocessor System-on-Chips. A challenge in application-specific NoC design is to find the right balance among different tradeoffs, such as communication latency, power consumption and chip area. We propose a novel approach that generates latency-aware heterogeneous NoC topology. Experimental results show that our approach improves the total communication latency up to 27% with modest power consumption. © 2013 The Author 2013. Published by Oxford University Press on behalf of The British Computer Society.
Open Access
Distributed power-source-aware routing in wireless sensor networks
(Springer New York LLC, 2016) Tekkalmaz, M.; Korpeoglu, I.
Although many applications use battery-powered sensor nodes, in some applications battery- and mains-powered nodes coexist. In this paper, we present a distributed algorithm that considers using mains-powered devices to increase the lifetime of wireless sensor networks for such heterogeneous deployment scenarios. In the proposed algorithm, a backbone routing structure composed of mains-powered nodes, sink, and battery-powered nodes if required, is constructed to relay data packets to one or more sinks. The algorithm is fully distributed and can handle dynamic changes in the network, such as node additions and removals, as well as link failures. Our extensive ns-2 simulation results show that the proposed method is able to increase the network lifetime up to 40 % compared to the case in which battery- and mains-powered nodes are not differentiated. © 2015, Springer Science+Business Media New York.
Open Access
Downlink data rate, energy and spectral efficiency distribution in heterogeneous networks with cell-edge located small cells
(Springer, 2020) Yenihayat, Güven; Karaşan, Ezhan
In this paper, the probability distributions of per user downlink data rate, spectral efficiency (SE) and energy efficiency (EE) are analytically derived for a heterogeneous network model with cell-edge located small cells. The high accuracies of analytically derived cumulative distribution functions (CDF) are verified using distributions obtained via simulations. CDF expressions are then used in order to optimize key performance indicators (KPI) which are selected here as 10th percentile downlink data rate (R10), spectral efficiency (SE10) and energy efficiency (EE10). In addition to optimizing KPIs separately, we also investigate the variation of the KPIs with respect to each other employing the analytically derived distributions. The results show that the resource allocation parameter values maximizing R10 are very close to the values that maximize EE10. However, the values that are optimal for EE10 and R10 are not optimal for SE10, which demonstrates the EE and SE trade-off in HetNets.
Open Access
Exact algorithms for a task assignment problem
(World Scientific Publishing Company, 2009) Kaya, Kamer; Uçar, B.
We consider the following task assignment problem. Communicating tasks are to be assigned to heterogeneous processors interconnected with a heterogeneous network. The objective is to minimize the total sum of the execution and communication costs. The problem is NP-hard. We present an exact algorithm based on the well-known A* search. We report simulation results over a wide range of parameters where the largest solved instance contains about three hundred tasks to be assigned to eight processors. © World Scientific Publishing Company.
Open Access
Heterogeneous network-on-chip design through evolutionary computing
(Taylor & Francis, 2010) Ozturk, O.; Demirbas, D.
This article explores the use of biologically inspired evolutionary computational techniques for designing and optimising heterogeneous network-on-chip (NoC) architectures, where the nodes of the NoC-based chip multiprocessor exhibit different properties such as performance, energy, temperature, area and communication bandwidth. Focusing primarily on array-dominated applications and heterogeneous execution environments, the proposed approach tries to optimise the distribution of the nodes for a given NoC area under the constraints present in the environment. This article is the first one, to our knowledge, that explores the possibility of employing evolutionary computational techniques for optimally placing the heterogeneous nodes in an NoC. We also compare our approach with an optimal integer linear programming (ILP) approach using a commercial ILP tool. The results collected so far are very encouraging and indicate that the proposed approach generates close results to the ILP-based approach with minimal execution latencies. © 2010 Taylor & Francis.
Open Access
Voltage island based heterogeneous NoC design through constraint programming
(Pergamon Press, 2014) Demiriz, A.; Bagherzadeh, N.; Ozturk, O.
This paper discusses heterogeneous Network-on-Chip (NoC) design from a Constraint Programming (CP) perspective and extends the formulation to solving Voltage-Frequency Island (VFI) problem. In general, VFI is a superior design alternative in terms of thermal constraints, power consumption as well as performance considerations. Given a Communication Task Graph (CTG) and subsequent task assignments for cores, cores are allocated to the best possible places on the chip in the first stage to minimize the overall communication cost among cores. We then solve the application scheduling problem to determine the optimum core types from a list of technological alternatives and to minimize the makespan. Moreover, an elegant CP model is proposed to solve VFI problem by mapping and grouping cores at the same time with scheduling the computation tasks as a limited capacity resource allocation model. The paper reports results based on real benchmark datasets from the literature.