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Öğe An autonomous packet transmission strategy for opportunistic wireless sensor networks(Sage Publications Inc, 2012) Soy, Hakkı; Özdemir, Özgür; Bayrak, MehmetWe consider a wireless sensor network that comprises a single hop between the sensor nodes and the central controller node with multiple antennas. In this system model, we concentrate on the single-beam opportunistic communication and propose two novel packet transmission schemes that can perform multiuser diversity gain based on the signal-to-noise ratio (SNR) and the normalized SNR (NSNR) measurements at the sensor nodes with single antenna. The main objective of the multiuser diversity is to increase the total throughput over the fast fading channels. Proposed schemes are based on the principle of cross-layer design that integrates with physical layer characteristics of wireless channel and medium access control (MAC) layer characteristics of network. In our design, we assume that the sensor nodes know only their own channels to the controller node and the packet transfer from the sensor nodes to the controller node is initiated when the channel quality of any node exceeds the predefined threshold at the current time slot. To determine the optimum threshold, we maximize the probability of successful packet transmission where only one sensor node transmits its packet in one time slot under the simplified collision model. Simulation results are demonstrated to compare the performance of the proposed schemes in terms of throughput, energy efficiency, and fairness. The obtained results show that the presented opportunistic strategy can be used to improve the network throughput.Öğe Decentralized multiuser diversity with opportunistic packet transmission in MIMO wireless sensor networks(Elsevier, 2013) Soy, Hakkı; Özdemir, Özgür; Bayrak, Mehmet; Hamila, Ridha; Al-Dhahir, NaofalIn this study, we consider a single-hop wireless sensor network where both the sensor nodes and the controller node have multiple antennas. We focus on single beam opportunistic communication and propose a threshold-based medium access control (MAC) scheme for uplink packet transmission which exploits multiuser diversity gain without feedback in a decentralized manner. Packet transfer from sensor nodes to the controller node is initiated when the channel quality of any node exceeds the predefined threshold based on the effective signal-to-noise ratio (ESNR) measurements at the sensor nodes through linear combining techniques. The optimum threshold is determined to maximize the probability of successful packet transmission where only one sensor node transmits its packet in one time-slot. The proposed scheme trades the successful packet rate to increase the SNR of the successful packets assuming Rayleigh fading and collision-based reception model. Computer simulations confirm that proposed scheme has higher successful packet SNR compared to the simple time division multiple access (TDMA)-based MAC scheme with round-robin fashion. The use of multiple antennas at the sensor nodes can also improve the throughput of proposed scheme compared with our previous scheme without implementing the spatial diversity at the SNs. (C) 2013 Elsevier GmbH. All rights reserved.Öğe Hassas Tarımda Kablosuz Algılayıcı Ağların Kullanımı ve Uygulama Alanlarının İncelenmesi(Iğdır Üniversitesi Fen Bilimleri Enstitüsü Dergisi, 2012) Dilay, Yusuf; Soy, Hakkı; Bayrak, MehmetTarımsal faaliyetlerde insan iş gücünün azaltılması, çiftçi refahını sağlarken, üretimin daha verimli ve kaliteli yapılmasını da sağlamaktadır. Özellikle bilgi ve iletişim teknolojilerindeki gelişmelerin tarım kesiminde kullanımı kaçınılmaz olmuştur. Kablosuz haberleşme sistemlerinde son yıllarda yaşanan hızlı gelişmeler kablosuz ağlar da dâhil olmak üzere pek çok alanda yeni teknolojilerin kullanılabilirliğini mümkün kılmıştır. Geleneksel kablosuz ağlardan farklı olarak kablosuz algılayıcı ağlar (KAA) fiziksel olguları gözetlemek üzere algıladığı veriyi işleyebilen ve birbirleri ile kablosuz ortamda haberleşebilen algılayıcı düğümlerden oluşur. KAA pek çok sivil ve askeri alanda olduğu gibi sulama, gübreleme, ilaçlama vb. tarımsal proseslerin yönetimi için hassas tarım alanında da görev yapabilirler. Bu şekilde KAA yardımıyla üretim miktarı ve ürün kalitesinin artırılması sağlanabilir. Bu çalışmada hassas tarım alanında KAA kullanımı incelenerek literatürde yer alan çeşitli tarımsal uygulamalar gözden geçirilmiştir.Öğe An improved opportunistic packet transmission scheme for wireless sensor networks(IEEE, 2010) Soy, Hakkı; Özdemir, Özgür; Bayrak, MehmetIn this paper, we consider a wireless sensor network in a single cell architecture, where a single hop between sensor nodes and central controller node exists. We propose a new medium access control (MAC) protocol and packet transmission scheme between sensor nodes with single antenna and central controller node with multiple antennas. Our scheme is an extension to previous work proposed by Coronel et al. [In Proceedings of the IEEE International Conference on Communications, Vol. 2, pp. 1082-1086, 2005] for wireless sensor networks. Unlike previous approach, enabling the use of the multi-user diversity based on normalized signal to noise ratio, we aim to increase throughput and energy efficiency in the system by increasing the received packets and reducing collisions. The throughput performance of the suggested scheme is compared through Monte Carlo simulations for frequency flat Rayleigh slow fading channel model.Öğe Intelligent control of agricultural irrigation system based on wireless sensor and actuator networks(Information Society, 2013) Soy, Hakkı; Dilay, Yusuf; Özkan, Adem; Aydın, Cevat; Bayrak, MehmetOptimizing water usage is the primary objective of intelligent and eco-friendly agricultural irrigation systems. In irrigation systems, the flow and pressure of water is usually regulated by controlling the position of the valve. The proportioning electronic actuator accepts a signal from the control system and moves the valve to allow the valve to partially open or close. Varying speed of pump motor can also control the usage of water. The integration of wireless sensor and actuator networks (WSANs) into irrigation management promises to overcome the excessive watering problem while providing additional functionality. This paper presents a case study on the use of WSAN for irrigation activities and investigates the application of fuzzy logic based valve aperture control. The results show that the proposed strategy can be effective in water flow control.Öğe Kablosuz Algılayıcı Ve Eyleyici Ağlar Yardımıyla Konya Ovasında Tarımsal Su Tüketiminin Azaltılması(Ulusal Kop Bölgesel Kalkınma Sempozyumu, 2013-11) Soy, Hakkı; Dilay, Yusuf; Aydın, Cevat; Bayrak, MehmetSu ve tarımsal üretim toplumların sosyo-ekonomik gelişim sürecinde kritik role sahiptir. Küresel ısınma tehdidi altındaki su kaynaklarının giderek artan dünya nüfusu karşısında talepleri karşılayamaması, suyun stratejik önemini gün geçtikçe artırmaktadır. Dünya genelinde pek çok yerde olduğu gibi ülkemizde de mevcut su kaynaklarının büyük bir kısmının tarımsal sulama için kullanılması, bu alanda tasarruf ve verimlilik artışı sağlamaya yönelik yenilikçi çalışmalara olan gereksinimi artırmıştır. Gelişmiş ülkelerde aşırı su tüketiminin azaltılması için faydalanılan hassas tarım teknolojilerinin başında, başarılı uygulamaları son yıllarda pek çok alanda giderek yaygınlaşan kablosuz algılayıcı ağlar gelmektedir. Geniş bir coğrafi bölge üzerinde dağınık algılama görevinin yerine getirilmesini mümkün kılan kablosuz algılayıcı ağlar yardımıyla saha üzerinde ilgilenilen fiziksel büyüklüklerin anlık değerleri uzaktaki bir yönetim merkezinden izlenebilir. Bu çalışmada Konya Ovasında tarımsal sulamanın daha verimli hale getirilmesi amacıyla yararlanılabilecek, temeli kablosuz algılayıcı ve eyleyici ağlara dayanan örnek bir sulama yönetim sistemi ana hatlarıyla incelenmiştir. Önerilen sistem modeliyle tarımsal su tüketiminin optimize edilmesi yanında, toprak ve meteorolojik koşullarla ilgili çevresel parametreler gerçek zamanlı olarak çiftçilerin bilgisine sunulmaktadırÖğe A threshold-based opportunistic MAC protocol for MIMO wireless sensor networks(IEEE, 2012) Soy, Hakkı; Özdemir, Özgür; Bayrak, Mehmet; Hamila, Ridha; Al-Dhahir, NaofalIn this paper, we consider a single-hop wireless sensor network where both the sensor nodes and the controller node have multiple antennas. We focus on single beam opportunistic communication and propose a threshold-based medium access control (MAC) scheme for uplink packet transmission which exploits multiuser diversity gain without feedback in a decentralized manner. Packet transfer from sensor nodes to the controller node is initiated when the channel quality of any node exceeds the predefined threshold based on the effective signal-to-noise ratio (ESNR) measurements at the sensor nodes through linear combining techniques. The optimum threshold is determined to maximize the probability of successful packet transmission where only one sensor node transmits its packet in one time-slot. Computer simulations confirm that the use of multiple antennas at the sensor nodes can improve the throughput of proposed scheme compared with our previous scheme without implementing the spatial diversity at the SNs assuming Rayleigh fading channel model.Öğe Throughput analysis of SNR and NSNR based opportunistic wireless sensor networks(2011) Soy, Hakkı; Özdemir, Ö.; Bayrak, MehmetWe previously proposed a threshold based medium access control (MAC) protocol that can perform multiuser diversity gain for star topology based wireless sensor network in a single cell architecture. The considered network model comprises a single hop between the sensor nodes and the controller node with multiple antennas. The optimum threshold was designed such that at a given time the probability that only one of the sensor nodes is above the threshold is being maximum. In this paper, the throughput performance of this MAC protocol is analyzed theoretically that has been based on the signal to noise ratio (SNR) and the normalized SNR (NSNR) estimation at the sensor nodes having a single antenna. Furthermore, the throughput and fairness performances of these are measured through Monte Carlo simulations for Rayleigh slow fading channel model. The obtained results shown that the tradeoff between the throughput and fairness can be adjusted by channel estimation metric..Öğe Wireless Sensor/Actuator Networks in Precision Agriculture: Recent Trends and Future Directions(Akademik Platform, 2014) Soy, Hakkı; Yusuf, Dilay; Özkan, Adem; Aydın, Cevat; Bayrak, MehmetAgricultural production and water has critical importance for socio-economic development of the societies. Unfortunately, the underground water level is slowly falling down and forests are being cut which reduces the rainfall as well. Technological advances on sensor technology and wireless communication are leading to the appearance of wireless sensor/actuator networks (WSANs) in a variety of commercial, industrial and military applications. There is no doubt merging wireless sensor technology into agricultural facilities will make farming activities much easier. In this paper, we look at the role of WSANs in agricultural production. We also investigate the communication architecture of WSAN based large scale irrigation management system and explain the key issues that are faced in the system design. Thanks to the easy installation and maintenance of WSANs, lots of water can be saved by giving timely feedback from field to improve the agricultural irrigation efficiency. This kind of solution can greatly help farmers to monitor the amount of water applied to a field
