Analyzing the performance of localization protocols for underwater acoustic sensor networks

Sualtı Duyarga Ağları (SDA) insan eliyle tehlikeli veya olanaksız sayılabilecek sualtı görevlerinde kullanılırlar. SDA’lar okyanusbiliminde, deprem ve tsunami tahmininde, askeri uygulamalarda, okyanus petrol platformlarının gözetlenmesinde ve çeşitli birçok alanda kullanılabilirler. Sualtı duyarga düğümleri sabit bir platforma tutturulmuş olabilir veya su içersinde serbest halde yüzebilir. Su yüzeyinden metrelerce aşağıda yüzen duyarga düğümler, gezgin sualtı duyarga ağını oluştururlar. Duyarga düğümler okyanuslardan sıcaklık, akıntı hızı, tuzluluk ve görüntü kaydı gibi veriler toplarlar. Gezgin bir SDA’da, duyarga düğümler su yüzeyinin altında, akıntıyla birlikte hareket eder ve belirli bir olayı izlerler. SDA’larda en ciddi sorunlardan biri konumlandırmadır. Konum bilgisine, veri etiketleme ve konum-tabanlı yönlendirme protokollerinde ihtiyaç duyulur. Geniş ölçekli, üç boyutlu SDA’lar için, literatürde az sayıda konumlandırma protokolü önerilmiştir. Bu makalede, İner-Çıkar düğümlerle Konumlandırma (İÇK) ve Vekil Konumlandırma (VK) yöntemlerini tanıtıp, sözkonusu yöntemlerin başarımını önceden önerilmiş olan bir başka yöntemle karşılaştırmaktayız. Bu yöntem, Geniş Ölçekli Konulmandırmadır (GÖK). Bu üç tekniğin avantaj ve dezavantajlarını gezgin bir SDA için göstermekteyiz. Benzetim sonuçlarımız GÖK’ün yüksek konumlandırma başarısına sahip olduğunu, ancak bu yöntemin beraberinde yüksek enerji tüketimi ve ek haberleşme yükü getirdiğini göstermektedir. İÇK ise, yüksek konumlandırma başarımı, yüksek kesinlik, düşük enerji tüketimi ve düşük haberleşme maliyetine sahiptir. VK ise, kabul edilebilir konumlandırma başarımı, düşük enerji tüketimi ve daha az ek yük getirmekte, buna karşılık diğerlerinden daha düşük kesinlik sağladığı görülmektedir.  Anahtar Kelimeler: Sualtı duyarga ağları, konumlandırma, duyarga ağlar.Underwater Sensor Networks (USNs) can improve naval defense, earthquake/tsunami forewarning, water pollution detection, ocean life monitoring systems, etc. Stationary Underwater Sensor Networks are ideal for securing or monitoring a fixed target region, e.g. monitoring oil drilling platforms for spill detection, harbor entrances for surveillance, ocean bottom for seismic activity observation, etc. On the other hand, mobile untethered Underwater Sensor Networks are flexible and better alternatives for short term exploration of moving targets. For instance, untethered, free-floating underwater sensors can track a chemical spill or a pollutant that may be dangerous to human health or sea life. In a sensor network, sensor nodes collect data from their surrounding and tag these data, in order to transmit them to a more powerful node for processing. Therefore, it is crucial to know the location of the sensor nodes. Location is required for data tagging, as well as, target detection, node tracking, etc. In addition, localization is essential for position-based routing algorithms which are powerful alternatives to classical routing approaches in Mobile Ad Hoc Networks (MANET). Localization is a well studied topic in terrestrial sensor networks. Nevertheless, in Underwater Sensor Networks, localization is still challenging due to several reasons: i) unavailability of the GPS; ii) low bandwidth, long delay and high bit error rate of the acoustic links; iii) necessity of high amount of sensor nodes to cover the three dimensional region. The use of GPS is limited to surface nodes because the GPS signal does not propagate through the water. In sensor networking literature, several GPS-less (GPS-free) positioning schemes have been proposed however they usually have high overhead. The underwater sensors use acoustic links and the bandwidth of those links is low even for very short distances. Moreover, acoustic communications has high propagation delay and high bit error rate. In Underwater Sensor Networks, localization protocols are expected to avoid excessive overhead and establish localization with the least possible messages. This is also enforced by the limited battery life of the underwater sensor nodes and the difficulty of recharging or replacing the batteries in an underwater application. Usually, an underwater application requires a large number of sensor nodes because the data rate of the acoustic links increases with decreasing distance and shorter ranges between nodes, means that more sensor nodes are needed to cover the three dimensional oceanographic zone. In addition, in a mobile Underwater Sensor Network localization should be repeated and stale location information should be cleared periodically. Considering all these challenges, it is essential to develop novel localization protocols tailored for mobile Underwater Sensor Networks. In this article, we introduce two distributed, scalable localization techniques; Dive and Rise Localization (DNRL) and Proxy Localization (PL). In DNRL, mobile beacons ascend and descend in the water to deliver their GPS driven coordinates. In PL, the already localized nodes act like beacons likewise multi-stage localization which is a preliminary version of PL (Erol et al., 2008). Unlike the previous work, in PL the non-localized nodes use a different metric to choose the best possible proxies among the candidates which enhances the performance of the protocol. Here, we compare the performance of PL, DNRL and Large-Scale Localization (LSL). LSL is a technique from the literature (Zhou et al., 2007). We evaluate the performance of these schemes in terms of localization success, accuracy, overhead and energy consumption. Since we compare the performance of the localization techniques for a mobile Underwater Sensor Network, a realistic underwater mobility model is essential. Recently, the works of Caruso et al. (2008) and Erol et al. (2008) have applied the real ocean current behavior to Underwater Sensor Networks. We use the "Meandering Current Mobility with Surface Effect" (MCM-SE) model to compare the performance of the three localization schemes for a mobile underwater sensor network. The main aim of the article is to provide a comparison between recently proposed localization schemes for Underwater Sensor Networks. Based on the simulation results, we compare and analyze the performance of three recent methods that are developed for distributed localization in large-scale Underwater Sensor Networks in terms of localization ratio, accuracy, protocol overhead and energy consumption.  Keywords: Sensor networks, underwater sensor networks, localization

Localization Algorithms of Underwater Wireless Sensor Networks: A Survey

In Underwater Wireless Sensor Networks (UWSNs), localization is one of most important technologies since it plays a critical role in many applications. Motivated by widespread adoption of localization, in this paper, we present a comprehensive survey of localization algorithms. First, we classify localization algorithms into three categories based on sensor nodes’ mobility: stationary localization algorithms, mobile localization algorithms and hybrid localization algorithms. Moreover, we compare the localization algorithms in detail and analyze future research directions of localization algorithms in UWSNs

A discovery process for initializing ad hoc underwater acoustic networks

Seaweb is an underwater acoustic wide-area network connecting autonomous, distributed nodes. Prior iterations of Seaweb relied on operator intervention to initialize and manually configure the network routes. This thesis implements a network discovery process that enables a field of spontaneously deployed, ad hoc nodes to auto-configure for networking purposes. Network routing is initialized as nodes in the network are discovered, with routes chosen according to comparative evaluation of a cost function for all candidate routes. The implemented network discovery process is tested using computer simulation and sea trial data. The resultant network routes obtained upon completion of the ad hoc network discovery process are compared with those derived from Dijkstra's algorithm. It is concluded that the network discovery process always produces a shortest-path route from a master node to any other discovered nodes in the network. Sensitivity studies on the route cost evaluation function are performed, and an alternative network discovery scheme is discussed.http://archive.org/details/adiscoveryproces109453774Republic of Singapore Navy author.Approved for public release; distribution is unlimited