The goal of this thesis work is to analyze how design elements and wireless attributes affect opportunistic routing, and in this context develop a new protocol. The algorithm developed aims to improve opportunistic elements in comparison to a well-known opportunistic protocol Simple Opportunistic Adaptive Routing (SOAR).

During the route discovery process, each node receiving the route request packet (RReq) will retransmit it exactly once. A distant neighbor may accidentally receive/loose the only RReq and use it to announce a new route, although that link is inferior/superior for route reply packets (RRep) or actual message routing. Overall, the constructed route may be far from the optimal. All existing route discovery schemes (including DSR/AODV) apply retransmission during route discovery exactly once (1R). Based on a realistic physical layer model, we propose two new route discovery schemes: n-retransmission (nR, retransmitting exactly n times) and n-retransmission c-reception (ncRR), retransmitting until we either reach a total of n own retransmissions or c copies from neighbors are heard. We compare our two new scheme with the traditional one, under otherwise identical conditions (same metric, same packet reception probability on each link) and the same choices about possibly retransmitting again upon discovering a better route (R+) or discarding it (R1), generating route reply packet for every received RRep (B*), or for first and better discovered routes only (B2), and retransmitting RRep exactly once (A1), up to a maximum of three times (A3), or optimally u times decided by link quality (Au). Experimental results show that the proposed ncRR scheme (for n=2 and c=3 or c=4) achieves the best tradeoff between quality of route, success rate and message overhead in the route discovery process, followed by the nR scheme, and both of them are superior to the existing traditional schemes.

Face routing is a simple method for routing in wireless ad-hoc networks. It only uses location information about nodes to do routing and it provably guarantees message delivery in static connected plane graphs. However, a static connected plane graph is often difficult to obtain in a real wireless network. This thesis extends face routing to more realistic models of wireless ad-hoc networks. We present a new version of face routing that generalizes and simplifies previous face routing protocols and develop techniques to apply face routing directly on general, non-planar network graphs. We also develop techniques for face routing to deal with changes to the graph that occur during routing. Using these techniques, we create a collection of face routing protocols for a series of increasingly more general graph models and prove the correctness of these protocols.

Face routing is a simple method for routing in wireless ad-hoc networks. It only uses location information about nodes to do routing and it provably guarantees message delivery in static connected plane graphs. However, a static connected plane graph is often difficult to obtain in a real wireless network. This thesis extends face routing to more realistic models of wireless ad-hoc networks. We present a new version of face routing that generalizes and simplifies previous face routing protocols and develop techniques to apply face routing directly on general, non-planar network graphs. We also develop techniques for face routing to deal with changes to the graph that occur during routing. Using these techniques, we create a collection of face routing protocols for a series of increasingly more general graph models and prove the correctness of these protocols.

Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2007-09-27 21:48:20.594 / Wireless networks are less reliable than wired networks because channels are “exposed” to the surrounding environment that is susceptible to interference and noise. To minimize losses of data due to collisions, wireless networks need a mechanism to regulate the access on the transmission medium. Medium Access Control (MAC) protocols control access to the shared communication medium so that it can be used efficiently. In this thesis, we first describe the collision-controlled Dual Prohibition Multiple Access (DPMA) protocol [45]. The main mechanisms implemented in DPMA, such as binary dual prohibition, power control, interference control, and support for differentiated services (DiffServ), are presented in detail. We conducted a thorough simulation study on DPMA protocol from several aspects. First, we conduct simulations to observe the effects of binary competition number (BCN), unit slot length and safe margin on the performance of DPMA. Secondly, the DiffServ capability of DPMA is demonstrated through simulation results. Finally, we compare the DPMA protocol with the CSMA/CA protocol and find that DPMA with optimal configuration has better performance than CSMA/CA under both low and high network density. / Master

During the route discovery process, each node receiving the route request packet (RReq) will retransmit it exactly once. A distant neighbor may accidentally receive/loose the only RReq and use it to announce a new route, although that link is inferior/superior for route reply packets (RRep) or actual message routing. Overall, the constructed route may be far from the optimal. All existing route discovery schemes (including DSR/AODV) apply retransmission during route discovery exactly once (1R). Based on a realistic physical layer model, we propose two new route discovery schemes: n-retransmission (nR, retransmitting exactly n times) and n-retransmission c-reception (ncRR), retransmitting until we either reach a total of n own retransmissions or c copies from neighbors are heard. We compare our two new scheme with the traditional one, under otherwise identical conditions (same metric, same packet reception probability on each link) and the same choices about possibly retransmitting again upon discovering a better route (R+) or discarding it (R1), generating route reply packet for every received RRep (B*), or for first and better discovered routes only (B2), and retransmitting RRep exactly once (A1), up to a maximum of three times (A3), or optimally u times decided by link quality (Au). Experimental results show that the proposed ncRR scheme (for n=2 and c=3 or c=4) achieves the best tradeoff between quality of route, success rate and message overhead in the route discovery process, followed by the nR scheme, and both of them are superior to the existing traditional schemes.

Syftet med studien var att analysera lärares synsätt på AD/HD. Studien bygger på sju intervjuer med lärare som arbetar i grundskolan. De teoretiska utgångspunkterna för denna studie var tre specialpedagogiska perspektiv - traditionellt, alternativt samt ett tredje perspektiv.Studien visar att lärarna är positiva till att diagnosen ställs då de menar att diagnosen är nyckeln till att få extra resurser inom skolan. Det framkommer i studien att de medicinsk/biologiska orsaksförklarningarna betonas och att den omgivande miljön påverkar. För att hjälpa barn med AD/HD i skolan menar lärarna att man bör se till den pedagogiska miljön, man skall anpassa undervisningen samt ge barnet de extra resurser som barnet behöver. Slutsatsen är bland annat att lärarna tenderar att vara mer orienterade mot det traditionella perspektivet som betonar individbundna brister. Men det går inte att utesluta att lärarna i vissa avseenden även överensstämmer med vad det alternativa perspektivet samt det tredje perspektivet står för.

Mitt examensarbete handlar om koncentrationssvårigheter. Att vara koncentrerad är inte det lättaste, under en hel dag måste eleven koncentrera sig på många olika saker. Eleven måste även lära sig att koppla bort vissa ljud och händelser för att kunna koncentrera sig på det den håller på med. Att hjälpa elever med koncentrationssvårigheter behöver inte vara komplicerat, det handlar om att göra undervisningen mer enkel och konkret. Koncentrationssvårigheter kan bero på många olika faktorer som till exempel miljön runt omkring eleven eller rent biologiska orsaker. För att komma fram till mitt resultat har jag intervjuat lärare och pedagoger samt observerat elever i olika åldrar på olika skolor. Det har givit mig en bra grund att stå på när jag sedan skrivit mitt arbete. I dagens skolor anser många lärare och pedagoger att det blir fler och fler elever som får koncentrationssvårigheter, frågan är om det verkligen är så? Är det en sådan ökning idag jämfört med hur det var förr eller är problemet bara mer uppmärksammat i dagens skola? Elever behöver inte få en diagnos för att ha koncentrationssvårigheter. För att få en diagnos krävs en viss problematik och detta uppfyller inte alla elever som har svårt att koncentrera sig. Alla elever har olika förutsättningar i skolan därför är det viktigt att vi som lärare och pedagoger kan ge dem den hjälp de behöver.

Mobile ad hoc networks consist of potentially moving, computing nodes that communicate via radio and do not have access to any fixed infrastructure. The knowl- edge about nearby nodes is a fundamental requirement and is part of many of the known solutions to problems in mobile and wireless networks including routing, broad- casting, distributed token circulation, etc. The existing solutions for this problem of knowing about neighbors are probabilistic. In this thesis, we give a first step towards a distributed, deterministic algorithm for finding out about the neighboring nodes. In particular, we focus on the problem of maintaining information about neighboring nodes in a one dimensional mobile and wireless ad hoc environment. Under some simplifying assumptions, we give an algorithm for the problem and a proof of correctness for the algorithm. We deal with efficiency in terms of both time and space. We prove a tight bound on the speed of propagation of the message when the nodes are sufficiently dense. We also consider the case when multiple clusters merge together. Our algorithm is space efficient in that the nodes do not include information about all the nodes they know in their broadcast message at all times. Nodes also store only the information about relevant nodes in their local store and purge information about nodes that have moved out of range. Our work shows that it is possible to solve the problem deterministically, and with reasonable values of the parameters, under some simplifying assumptions. Numerous interesting open questions remain in the area regarding how to relax the assumptions to make the approach more practical.

IEEE 802.11 MAC protocol uses two techniques to avoid interference ¡V physical carrier sensing and RTS/CTS handshake (virtual carrier sensing). Ideally, these two techniques can solve most of interference problem. But in normal situation a host cannot receive packet successfully unless the power of receiving signal is much higher than that of interference signal. This fact leads that other host can interfere the reception in farther distance than the distance between the transmitter and the receiver. When the distance between the transmitter and the receiver is larger than certain value, some hosts that are out of the range covered by RTS/CTS packet may still interfere the receiver. This problem can be solved by using a very large physical carrier sensing range, which is limited by antenna and will reduce the network throughput. So it¡¦s not suitable to avoid large interference problem. So far some schemes were proposed to solve or improve this problem, but most of them cause power waste at the same time. In this thesis, we will propose a scheme to look after both interference and power consumption. Simulation results verify that our scheme can solve most interference caused by large interference range with less power consumption.