Photonic crystals in biology - NanoTR-VI

Poster Session, Thursday, June 17Theme F686 - N1123Defect Tolerance in Self-Assembled Networks with Mobile Nano-MachinesBirkan Polatoğlu*, Alper Rasim Çakır and Sema Oktuğİstanbul Technical University, Department of Computer Engineering, İstanbul 34469, TurkeyAbstract - We concentrated on network of finite number of nano-machines that are freely floating in their environment and that interact viamolecular communication. We improve the proposed defect tolerance mechanisms that are based on Reverse Path Forwarding routing algorithmin order to tolerate defects in self-assembled networks that contains mobile nano-machines. Our solution keeps the broadcast tree up-to-dateeffectively.Nanoelectronic devices are investigated as an alternativeto CMOS technologies recently. These devices are extremelysmall and thus need very low charge transfers to switch state[1]. The proposed properties of nanoelectronic devices providegreater device density and make them advantageous overCMOS. However the circuits using these devices aresusceptible to defects and faults because of these properties.Nano-machines can be interconnected to cooperate andshare information and overcome collaborative tasks.Communication between nano-machines can be performedthrough different technologies, such as electromagnetic,acoustic, nanomechanical or molecular. Molecularcommunication is the most promising technique in comparisonto other ones due to the size and natural domain of molecules.Molecular communication is inspired by the communicationamong living cells, and it is defined as the transmission ofinformation using molecules. Molecular communication takesplace in aqueous medium. Due to the organic and chemicalnature of the nano-machines and information molecules, thenanonetwork is highly sensitive to the environmentalconditions, such as temperature, humidity, medium viscosityand pH. The communication process can be negativelyaffected by sudden variations of these conditions [2].DNA self-assembly is a bottom-up fabrication techniquethat uses DNA as a scaffold material to attach electronicdevices. Self-assembly does not have control over theplacement of devices, so it is prone to higher defect rates thanthose produced by other techniques. Systems built usingbottom-up self-assembly of nanoelectronic devices will needto incorporate defect tolerance in their design in order tomaintain their advantage over CMOS [1].The presented defect tolerance mechanism in [1] does notrequire an external defect map, nor does it require redundancyof complex computational circuits. Reverse path forwardingalgorithm is used to map out defective nodes at startup and tocreate a broadcast tree of non-defective nodes. The interfacebetween the system and the micro-scale world are called via.The special broadcast packet is inserted into the network fromvias that are located one in each side center and one in thecenter of the NxN network. On receiving the special broadcastpacket, the node broadcasts it on its entire links, except thelink that it received the packet on [1].Nano-machines (nodes) in the proposed mechanism in [1]are immobile and each node is assumed to have fourtransceivers, so the maximum number of children of a node isfour. Transient and permanent faults during system operationare not handled as well. The broadcast tree is created in thebeginning by broadcasting the gradient packet and this tree isused for communication among the nodes. If one of the nodeson broadcast tree is deteriorated transiently or permanently,the links passing from this node will not be functional. Thechildren or the sub tree under the failed node or link areunreachable from vias and treated as defective nodes.Here, we concentrated on a system in which finite numberof nano-machines freely floating in their environment thatinteract via molecular communication. Each nano-machine inthe system is identified with a single-stranded DNA with thepurpose of unique addressing. Inspired from the living cells,nano-machine’s DNA is assumed as a database to store allsingle-stranded DNA sequences of the other nano-elements asa potential neighbor. In this nano-network environment it isassumed that all cells are taken from the same living creaturewhich will guarantee that all of the nano-elements have thesame DNA sequence or database. We propose new mechanismthat handles transient and permanent faults during systemoperation by improving the proposed framework on [1]. Wedefine a new state for the children of the failed nodes and callit ‘free non-defective’ state. In case of node failure inbroadcast tree, the nodes under the failed node change theirstatus from ‘non-defective’ to ‘free non-defective’. The nodesthat do not take packet from other nodes during specifictimeout interval set their status to ‘free non-defective’ as well.In molecular communication, after a certain time,information molecules disintegrate into other molecules andthey are not interpreted by receiver node. In their life time,molecules can travel by diffusion in average a certain maximaldistance called communication radius [3]. Each node cansend information molecule to the nodes in its communicationradius. The nodes in the communication radius of ‘free nondefectivenode’ will query the nodes around to find ‘free nondefective’ones. When a ‘free non-defective’ node identified,it is set as the child of the node sending the query and its stateis made ‘non-defective’. The broadcast tree that connects allreachable non-defective nodes is kept up-to-date by the help ofthis mechanism.In summary, our work introduces a new approach for thedefect tolerance in self-assembled networks that containmobile nano-machines by improving the mechanismsintroduced earlier in order to keep the broadcast tree up-todateeffectively. Currently, we are collecting data fromsimulation that we have improved for these enhancements.*Corresponding author: polatoglu@itu.edu.tr[1] J.P. Patwardhan, C. Dwyer, A. R. Lebeck, and D. J. Sorin, 2005.Evaluating the Connectivity of Self-Assembled Networks of NanoscaleProcessing Elements, NANOARCH '05.[2] I.F. Akyildiz, F. Brunetti, C. Blázquez, 2008. Nanonetworks: ANew Communication Paradigm, Elsevier Computer Networks 52.[3] J. Wiedermann, L. Petrů, 2008. Communicating Mobile Nano-Machines and Their Computational Power, Third International ICSTConference, NanoNet.6th Nanoscience and Nanotechnology Conference, zmir, 2010 686