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Publications by Type: Undergrad Theses (Bachelor, Diplom, and Master Theses) and Study Projects

Realizing Scheduled Medium Access with CSMA in Wireless Sensor Networks
Citation key T-RSMACWSN-12
Author Torres, Virginia
Year 2012
Address Berlin, Germany
Month April
School Technische Universit├Ąt Berlin
Abstract Everything is becoming wireless, from the mobile phone everybody has to the future refrigerator at home that can be controlled remotely. We observe every day more and more devices are using this relatively new form of communication. The increasing density of wireless-enabled devices, and their increasing communication demands urges a reliable and efficient -not only effective- under layer to assure that all demands from all services/applications used by a user are satisfied. This under layer is called the MAC layer, corresponding to a sub-layer at the datalink level from the OSI Reference Model, and in this layer, a device controls its access to the medium - the channel. There exists several protocols that mediate channel access such as TDMA and CSMA, which are the main topics of interest of this thesis TDMA Protocol (Time Division Multiple Access) is a very well known protocol that aims to make the channel allocation fair to all participants. TDMA divides time into slots where every network node knows when to transmit based on an already-known schedule. Due to its high cost in message passing and clock synchronization, many researchers try to find another way of accomplishing the same objective in a more inexpensive way. This is the motivation behind the self-synchronizing wireless CSMA algorithm which is implemented in this thesis. CSMA (Carrier Sense Multiple Access) is a protocol in which the node, before transmitting, checks if the channel is clear, and if it is, it starts the transmission. in the case that the channel is busy, the node waits for a random period of time, till the channel gets free, and only then it starts to transmit. This is the property used by the self-synchronizing wireless CSMA algorithm proposed by [9], in which every participant of the network follows a schedule. As in TDMA the schedule is known in advance, and a node decides when to transmit just by overhearing its direct neighbours. In my thesis, I implement the proposed algorithm in a wireless multi-hop sensor network and test if such an algorithm is realizable under real world settings with real sensor nodes. I identified the assumptions that do not hold in practice and proposed solutions that help mitigate these problems.
Bibtex Type of Publication Bachelor Thesis
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