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    Effects of transmit-based and receive-based slot allocation strategies on energy efficiency in WSN MACs
    (Elsevier Science Bv, 2014) Karahan, Alper; Ertürk, İsmail; Atmaca, Sedat; Çakıcı, Süleyman
    In this work, the effects of time Slot Allocation Strategies (SASs) on node energy consumption for time slot assignment-based Medium Access Control (MAC) protocols, generally preferred in Wireless Sensor Networks (WSNs) for energy efficiency, are comparatively studied. As Wireless Nodes' (WNs) energy consumption in WSNs determines the lifetime of network, it is of critical importance for application designers to know the best SAS to apply. Energy efficiency in WSNs can be maximized by employing an appropriate MAC while (i) assigning wireless medium resources efficiently and fairly among the WNs, (ii) minimizing packet collisions and (iii) avoiding overhearing. This paper aims at presenting and comparing the energy efficiency of transmit-based and receive-based SASs for multi-hop topologies used in WSN MAC. We have developed, modeled and analyzed both transmit-based and receive-based strategies. Based upon analytical models, comparative performance evaluations are presented. Besides, a detailed simulation study is carried out in a sample networking scenario by utilizing the OPNET Modeler software in order to confirm the analytical results. The study concludes that the receive-based SAS is at least five times more energy efficient than the transmit-based strategy in multi-hop network topologies, which is highly beneficial information to the WSN MAC designers. (C) 2013 Elsevier B.V. All rights reserved.
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    Geniş Ölçekli Kablosuz Algılayıcı Ağlar İçin Enerji Verimli Melez OEK Protokolü
    (Ieee, 2015) Karahan, Alper; Ertürk, İsmail; Atmaca, Sedat; Çakıcı, Süleyman
    Bu bildiride sunulan çalışmada geniş ölçekli KAA (Kablosuz Algılayıcı Ağ) uygulamalarında kullanılmak üzere düğüm enerji tüketim verimliliğini esas alan melez bir OEK (Ortam Erişim Kontrol) protokolü geliştirilmiştir. Tasarlanan melez OEK protokolünde, CSMA (Carrier Sense Multiple Access) ve TDMA (Time Division Multiple Access) ortam erişim yöntemlerinin üstün yönleri bir arada kullanılmaktadır. Böylece geniş ölçekli KAA uygulamalarında her iki yöntemden de daha enerji verimli bir OEK protokolü hedeflenmiştir. Olaylara (events) hızlı tepki veren CSMA yöntemi ile çarpışma ve gereksiz dinlemeleri en aza indiren TDMA yöntemi alma tabanlı olarak bütünleştirilerek yüksek sistem başarımı ve düğüm enerji verimliliği elde edilmiştir.
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    An integrated approach for analytical modeling of WSNs
    (2009) Çakıcı, Süleyman; Ertürk, İsmail; Karahan, Alper; Atmaca, Sedat
    Nowadays, with the ever-increasing use of the Wireless Sensor Networks (WSNs) in parallel with developments in sensor and wireless communication technologies, modeling of these networks has also become essential. The analytical modeling is one of the basic approaches used for testing WSNs and verification of their abilities. The goal of this study is to build an analytical model for the performance metrics that allow making an integrated evaluation of a WSN application. The effects of the application layer components with the routing, MAC and security protocols on the performance metrics are obtained by using an analytical model based on an example WSN application scenario. The results obtained from the analytical models by using technical specifications of a common WSN node (MICAz) are presented and discussed. ©2009 IEEE.
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    A new Network Coordinator Node Design Selecting the Optimum Wireless Technology for Wireless Body Area Networks
    (Ksii-Kor Soc Internet Information, 2013) Çalhan, Ali; Atmaca, Sedat
    This paper proposes a new network coordinator node design to select the most suitable wireless technology for WBANs by using fuzzy logic. Its goal is to select a wireless communication technology available considering the user/application requirements and network conditions. A WBAN is composed of a set of sensors placed in, on, or around human body, which monitors the human body functions and the surrounding environment. In an effort to send sensor readings from human body to medical center or a station, a WBAN needs to stay connected to a local or a wide area network by using various wireless communication technologies. Nowadays, several wireless networking technologies may be utilized in WLANs and/or WANs each of which is capable of sending WBAN sensor readings to the desired destination. Therefore, choosing the best serving wireless communications technology has critical importance to provide quality of service support and cost efficient connections for WBAN users. In this work, we have developed, modeled, and simulated some networking scenarios utilizing our fuzzy logic-based NCN by using OPNET and MATLAB. Besides, we have compared our proposed fuzzy logic based algorithm with widely used RSSI-based AP selection algorithm. The results obtained from the simulations show that the proposed approach provides appropriate outcomes for both the WBAN users and the overall network.
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    A Novel Cross-layer Routing Protocol for Increasing Packet Transfer Reliability in Mobile Sensor Networks
    (Springer, 2014) Çakıcı, Süleyman; Ertürk, İsmail; Atmaca, Sedat; Karahan, Alper
    In mobile sensor networks (MSNs), sensor data is generally transferred via mobile sensor nodes by multi-hop fashion. Because of the mobility of the nodes in the network, the efficient routing protocols are needed to ensure end-to-end route reliability while incurring minimal power consumption and packet delay. In this study, we developed a new routing protocol to meet these requirements for MSNs based on a cross-layer interaction among five reference layers (application, transport, network, MAC and physical). The proposed protocol primarily exploits the idea of interaction among these five layers all-in-one protocol. Its primary goals are (i) to discover the most reliable route in network, (ii) to sustain the route reliability and (iii) to be energy efficient and delay aware. It has been designed, modeled and simulated by using OPNET Modeler simulation software. The simulation results of the proposed protocol have been compared to three well known routing protocols (i.e., AODV, Leach-Mobile, CBR-Mobile). According to the obtained results, the proposed protocol outperforms its counterparts in terms of route reliability and end-to-end delay performances.
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    A slotted ALOHA-based cognitive radio network under capture effect in Rayleigh fading channels
    (2016) Bayrakdar, Muhammed Enes; Atmaca, Sedat; Karahan, Alper
    In this paper, a slotted ALOHA-based cognitive radio (CR) network is proposed and the throughput performance of the proposed CR network model under Rayleigh fading channels is examined. Our CR network contains two special groups of users, primary users (PUs) and CR users (CRUs), and they are considered to be sharing a timeslotted-based common communication channel. While PUs can access the channel at any time owing to their legal right, CRUs can only access the channel when it is not occupied by the PUs. In the network model developed, PUs access the channel utilizing time division multiple access as a medium access control technique, and CRUs can access the channel by exploiting slotted ALOHA as a random access scheme when the channel is idle. In the proposed network model additive white Gaussian noise and Rayleigh channels is considered for comparison reasons. Taking capture effect into account in Rayleigh fading channels, we have obtained new equations for the throughput of the proposed CR network. We have also developed, modeled, and simulated a sample networking scenario by using MATLAB with the aim of validating the analytical throughput results. Simulation results of the proposed network model precisely match with the analytical results obtained under different network load conditions. Furthermore, it is shown that the overall channel exploitation is increased by utilizing the spectrum holes without interfering with the PUs transmissions.
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    A slotted ALOHA-based cognitive radio network under capture effect in Rayleigh fading channels
    (Tubitak Scientific & Technical Research Council Turkey, 2016) Bayrakdar, Muhammed Enes; Atmaca, Sedat; Karahan, Alper
    In this paper, a slotted ALOHA-based cognitive radio (CR) network is proposed and the throughput performance of the proposed CR network model under Rayleigh fading channels is examined. Our CR network contains two special groups of users, primary users (PUs) and CR users (CRUs), and they are considered to be sharing a time slotted-based common communication channel. While PUs can access the channel at any time owing to their legal right, CRUs can only access the channel when it is not occupied by the PUs. In the network model developed, PUs access the channel utilizing time division multiple access as a medium access control technique, and CRUs can access the channel by exploiting slotted ALOHA as a random access scheme when the channel is idle. In the proposed network model additive white Gaussian noise and Rayleigh channels is considered for comparison reasons. Taking capture effect into account in Rayleigh fading channels, we have obtained new equations for the throughput of the proposed CR network. We have also developed, modeled, and simulated a sample networking scenario by using MATLAB with the aim of validating the analytical throughput results. Simulation results of the proposed network model precisely match with the analytical results obtained under different network load conditions. Furthermore, it is shown that the overall channel exploitation is increased by utilizing the spectrum holes without interfering with the PUs' transmissions.