EVALUATING MEDIUM ACCESS CONTROL PROTOCOLS FOR WIRELESS SENSOR NETWORKS, ACTA UNIVERSITATIS OULUENSIS C Technica 350
|Kustantaja:||Oulun yliopisto|| |
|Oppiaine:||Tekniikka, matematiikka|| |
|Sijainti:||Print Tietotalo|| |
|Tekijät:||HAAPOLA JUSSI|| |
Wireless sensor networks (WSNs) offer us a potential for greater awareness of our surroundings,collecting, measuring, and aggregating parameters beyond our current abilities, and provide anopportunity to enrich our experience through context-awareness. As a typical sensor node is smallwith limited processing power, memory, and energy resources, in particular, these WSNs must bevery energy-efficient for practical deployment. Medium access control (MAC) protocols arecentral to the energy-efficiency objective of WSNs, as they directly control the most energyconsuming part of a sensor node: communications over the shared medium.
This thesis focuses on evaluating MAC protocols within the WSN domain by, firstly,surveying a representative number of MAC protocols and their features. Secondly, three novelMAC protocols are proposed, one for layered contention-based access, one for layered scheduledaccess, and one for cross-layer contention-based access. Thirdly, a novel energy consumptionmodel is proposed, and fourthly, a holistic MAC protocol evaluation model is proposed that takesinto account application emphasis on performance metrics. The MAC protocols are evaluatedanalytically. In addition, the layered contention-based MAC protocol has been implemented andmeasured, and the cross-layer contention-based protocol operating over an impulse radio-ultrawideband (IR-UWB) physical layer has been verified by simulations with relevant physical layercharacteristics. The energy consumption evaluation model proposed is straightforward to modifyfor evaluating delay, and it can reuse state transition probabilities derived from throughputanalysis. The holistic application-driven MAC protocol evaluation model uses a novel singlecompound metric that represents a MAC protocol's relative performance in a given applicationscenario.
The evaluations have revealed several significant flaws in sensor MAC protocols that areadapted to sensor networking from ad hoc networks. Furthermore, it has been shown that, whentaking sufficient details into account, single hop communications can outperform multi-hopcommunications in the energy perspective within the feasible transmission ranges provided bysensor nodes. The impulse radio physical layer introduces characteristics to MAC protocols thatinvalidate traditional techniques which model the physical layer in terms of simple collisions.Hence, these physical layer characteristics have been modelled and included in the analysis, whichimproves the level of agreements with simulated results.