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A multievent congestion control protocol for wireless sensor networks

Wireless sensor networks are application-dependent networks. An application may require general event region information, per-node event region information, or prioritized event information in case of multiple events. All event flows are subject to congestion in wireless sensor networks. This is due to the sudden impulse of information flow from a number of event nodes to a single destination. Congestion degrades system throughput and results in energy loss of nodes. In this paper, we present a multievent congestion control protocol (MCCP) for wireless sensor networks. MCCP supports multiple event reporting modes, that is, general event reporting, per-node fair event reporting, and prioritized multiple event reporting. MCCP efficiently mitigates congestion and provides output according to selected event reporting mode. MCCP uses hop-by-hop packet delivery time and buffer size as the basic metrics for congestion detection. Moreover, we introduce a schedule-based scheme at the transport layer for rate assignment and ordered delivery of event packets to underlying routing layer. This helps to avoid packet collisions and increases the packet delivery ratio even in high densities. Detailed simulation analysis confirms that MCCP decreases packet drops and provides high packet delivery ratio (above 90%) for multiple event reporting modes.

Turkish word n-gram analyzing algorithms for a large scale Turkish corpus - TurCo

To calculate some statistical properties of a language, first you need to take some samples of that language. That sample is called a corpus. An unbalanced large scale Turkish text corpus (TurCo) having /spl sim/362 MB capacity and more than 50 million words was prepared by using 12 different resources including Web sites and novels in Turkish language. Different algorithms were tested to obtain the n-gram (1/spl les/n/spl les/5) values. Efficiencies of different algorithms have been examined by applying them onto the each piece of the corpus one by one. Only detailed results of the two algorithms created without using database tables are given, because all the other algorithms need to run more than one day which makes those tests inefficient.

Zipf's law and mandelbrot's constants for turkish language using turkish corpus (turco)

Zipfs Law is a common law applied for different kinds of observations. Many investigations were carried out to find the correspondences between Zipfs Law and different languages. This study deals with the correspondence of Turkish with Zipfs Law and finding Mandelbrot constants (c and B ) by using a large scale Turkish corpus (TurCo). In order to determine these constants, coefficient of determination was used, and different c and B values were examined. As both languages show agglutinative characteristics, the most suitable B value was found smaller than 1 for Turkish like Korean, and c value was found as 0.27.

Many-to-one congestion control scheme for densely populated WSNs

Many-to-one transport results in congestion in wireless sensor networks. This is due to the sudden impulse of information flow to a single destination. Greater the number of event reporting nodes greater will be the degree of congestion; considering fixed transmission power for nodes. Therefore an important factor in the design of a congestion control scheme is the density of the network. In this paper we present a new congestion control scheme based on hop-by-hop packet delivery time and buffer size. The new congestion control scheme is at the transport layer and uses a TDMA-like mechanism to optimally adjust the reporting rate of events. Detailed simulation analysis confirm that the proposed congestion control scheme decreases packet drops and provide high packet delivery ratio (above 90%) from even very dense event reporting regions.

A 300 MB Turkish Corpus and Word Analysis

In order to determine some properties of a language, a corpus of that language should be created. To analyze Turkish language, at first, a Turkish corpus having ∼300 MB capacity and more than 44 million words was prepared by using 10 different web sites having Turkish content. Most frequently used word statistics of Turkish were calculated by using this corpus. Frequencies of most frequently used first 7 words were compared with their equivalent in English, and it was found out that most frequently used words are not nouns in natural languages Most frequently used words having 1 to 5 letters were determined and they were applied onto a randomly selected text in order to test the validity of the process.

Turkish spelling error detection and correction by using word n-grams

N-grams can be used for spelling check and correction processes. The first step to use n-grams is to find the language specific n-grams by using a corpus. But a corpus cannot be big enough to contain all the possible word n-grams. Back-off smoothing technique is one of the techniques to estimate the frequency of the unknown n-grams in a corpus. By using Back-off technique and the Minimum Edit Distance (MED) algorithm, a program was developed to check spelling errors and suggest corrections in a sentence typed in Turkish. The results were compared with the results of Microsoft Word 2003 proofing tools, and found to be much better.

Power management for Wireless Sensor Networks in underground mining

Due to the challenging working conditions in the underground mining, some difficulties are being experienced in sensing and monitoring of important physical environmental parameters. The requirement for a Wireless Sensor Network has gained significant importance in recent years for the measurement and transmission of various data from different areas of an underground operation to a central monitoring station. The sensor nodes in Wireless Sensor Network, capable of microcontroller controlled wireless data transferring, could work with electricity in the main roads of the underground mine, however, the necessity of using sensor nodes using batteries in various fields like production and abandoned areas emerges. The working life of each sensor nodes depends on the efficiently managed battery lifespan. The battery life depends on the battery type selection, the standby and active mode power consumption of microcontrollers, wireless transmitters and receivers, sensors and miscellaneous electronic circuits. In this study, applicable methods to reduce the battery consumption for Wireless Sensor Networks in underground mining are examined.

Event Reporting with Fairness in Wireless Sensor Networks

Fairness in wireless sensor networks demands event nodes to have an equal share in the overall throughput of the system. Fairness is difficult to achieve in sensor networks due to multiple hop packet forwarding to a single destination that results in congestion. Moreover, greater the density of event region greater is the level of interference and greater is the number of packet drops. In this paper, we present a mechanism for fair event reporting that is implemented at the transport layer. The solution encompasses congestion control and fair rate adjustment schemes based on hop-by-hop packet delivery and buffer size. Moreover, a schedule based packet forwarding policy is used at the transport layer for ordered delivery of packets to the underlying layer; instead of commonly used jittered forwarding. The simulation results of our scheme shows high per node fair throughput from multiple event nodes to a single sink. Also, the use of our schedule-based packet forwarding policy helps to avoid packet collisions and increases the packet delivery ratio even from densely populated event regions.

A unified event reporting solution for wireless sensor networks

Wireless sensor networks are deployed to observe a variety of events from the sensor field. Each event can have different constraints in terms of reporting rate, fairness, priorities and real-time information delivery. A number of event reporting, transport, congestion and rate control schemes have been proposed in the existing literature. However, these solutions have been proposed for different applications, spanning on different layers of protocol stack with contradicting basic assumptions. Therefore, due to the architectural and operational differences of these solutions, existing protocols are not appropriate to operate in a unified manner at the transport layer of sensor networks. This work presents a unified scalable, energy-aware and flexible event reporting solution for wireless sensor networks. The proposed event reporting solution provides different modes for event reporting like simple, fair, prioritized and real-time. Simulation study proves that the proposed event reporting solution provides maximum throughput, high packet delivery ratio, low energy consumption and achieves different event reporting mode requirements.

Surface gravity vectors: an approach for open pit mine optimisation

Abstract Extraction sequence optimisation is highly complex with thousands of ore and waste blocks to be sequenced with respect to the net present value criterion. The aim of this study is to explain the surface gravity vectors approach, which is proposed to be used in open pit mine optimisation process. This approach uses an analogy between the universal gravity law and open pit mining. The economic values of the ore blocks are assumed as their mass and the extraction sequence is determined by the total gravity vector between the shovels and ore blocks.