Anti Collision Research Articles

Dynamic Grouping Frame-Slotted Aloha

be adjusted exactly to the number of tags to be identified. In this paper, we proposed a new Aloha based anti-collision algorithm which divides the tags and adjusts the frame sizes in such a manner as to always keep the system efficiency optimal. The algorithm is also designed in order to reduce the identification time for identifying the total number of tags. As a result the proposed algorithm uses minimum number of slots to read the tags with minimum identification time. Simulation results show that the algorithm gives maximum slot efficiency with every frame maintaining the system efficiency close or equal to 36.8% compared to other anti collision algorithms.

A novel architecture for multihops routing ad hoc underwater acoustic sensor networking

Underwater acoustic communication networks are an innovative issue, which faces difficult medium problems, such as long propagation time and dynamic network topology. In addition, due to high error probabilities typical for this channel it is preferred to use anti collision network mechanism. Because of the long propagation time, methods such as CTS/RTS, requiring transmissions of pre‐messages, achieve relatively low network efficiency. Moreover, TDMA methods do not utilize the network resources allowing reuse in the code domain (using CDMA) and in the spatial domain in case of nonhomogenic network topology which includes obstructions in the acoustic line of sight. In this paper we introduce a network concept based on the CDMA method confronting the acoustic underwater network challenges, such as the “near‐far” problem, fast time varying topology, multihops routing and message distribution protection. Using this concept, a sea trial including broadcast, multicast and unicast transmissions of SMS and navigation control messages was carried out in various scenarios including multihops near the shores of Israel. We present results from this sea trial demonstrating the efficacy of the proposed networking scheme.

The comparison of assessment of pigeon semen motility and sperm concentration by conventional methods and the CASA system (HTM IVOS)

The aim of these experiments was to compare conventional, microscopic methods of evaluating pigeon sperm motility and concentration to those measured by computer-assisted sperm analysis (CASA system). Semen was collected twice a week from two groups of pigeons, each of 40 males (group I: meat-type breed; group II: fancy pigeon) using the lumbo-sacral and cloacal region massage method. Ejaculates collected in each group were diluted 1:100 in BPSE solution and divided into two equal samples. One sample was examined subjectively by microscope and the second one was analysed using CASA system. The sperm concentration was measured by CASA using the anti-collision (AC) system and fluorescent staining (IDENT). There were not any significant differences between the methods of evaluation of sperm concentration. High positive correlations in both groups were observed between the sperm concentration estimated by Thom counting chamber and AC (r=0.87 and r=0.91, respectively), and between the sperm concentration evaluated by Thom counting chamber and IDENT (r=0.85 and r=0.90, respectively). The mean values for CASA measurement of proportion of motile spermatozoa (MOT) and progressive movement (PMOT) were significantly lower than the values estimated subjectively in both groups of pigeons (p< or =0.05 and p< or =0.01, respectively). Positive correlations in MOT and PMOT were noted between both methods of evaluation. The CASA system is very rapid, objective and sensitive method in detecting subtle motility characteristics as well as sperm concentration and is recommended for future research into pigeon semen.

Anti collision system proreta — The way to the crash avoiding vehicle

Thanks to the increasing distribution of active and passive safety systems in motor vehicles, the amount of fatal road casualties has been reduced in recent years continuously. The basis of the anti collision system Proreta was presented in the first part of this article. This driver assistance system for emergency braking and emergency evasion was developed at TU Darmstadt in cooperation with Continental AG. In this second part of the article the results of the ergonomic study and then the results from driving tests are presented.

Anti collision system proreta — On the way to the collision avoiding vehicle

Thanks to the increasing application of active and passive safety systems in motor vehicles, the amount of fatal road casualties has been reduced in recent years continuously. Having the project Proreta in process the goal was followed to further contribute to this trend by creating an advanced driver assistance system for collision avoidance. The system was developed at Technische Universitat Darmstadt in cooperation with Continental AG. The basics of this system are explained in the first part of a two-part article in the following. Subsequently, in the second part conclusions of an ergonomic study included in the project are presented and results from driving tests are illustrated.