izpis_h1_title_alt

PROTOKOL ZA GRUČENJE VOZIL NA OSNOVI MEDSEBOJNE POVEZANOSTI V INTELIGENTNIH TRANSPORTNIH SISTEMIH
VODOPIVEC, SAMO (Author), Bešter, Janez (Mentor) More about this mentor... This link opens in a new window

.pdfPDF - Presentation file, Download (3,10 MB)

Abstract
Čas interneta stvari, del katerega bodo tudi pametna, povezana vozila, se nezadržno približuje. Slednje odpira vrata novim tehnologijam, ki bodo v prihodnosti imele pomembno vlogo pri zagotavljanju brezžičnih komunikacij med najrazličnejšimi napravami. V doktorski disertaciji je pozornost posvečena organizaciji in optimizaciji brezžičnih ad-hoc omrežij1 cestnih vozili v Inteligentnih transportnih sistemih. Velika dinamika vozil namreč predstavlja svojevrsten izziv za vzpostavitev zanesljivega, stabilnega, predvsem pa uporabnega komunikacijskega omrežja, ki zagotavlja ustrezno kakovost storitve. Za spoznavanje s področjem komunikacije med vozili smo opravili raziskave in pregled standardizacije tega področja. Ugotovili smo, da standardizacija še ni končana in poteka v smeri poenotenja svetovnih standardov. Zaradi nepovezanih raziskav in razvoja so v preteklosti različne regije vsaka po svoje standardizirale praktično iste storitve, kar pa se sedaj kaže kot slabost za hitro in finančno učinkovito implementacijo sistemov v praksi. ZDA, Evropa in Japonska se zato skupaj trudijo poenotiti standardizacijo, še preden pride do masovne uporabe, ter tako preprečiti nepotrebno segmentacijo. Pričakovati je, da bodo uporabi teh standardov pozneje sledile tudi druge države, čeprav trenutno ne sodelujejo pri njihovem nastajanju. Ker se standardizacija ne ukvarja z optimizacijo omrežja, temveč predpisuje zgolj robne pogoje kvalitete storitve, ki mora biti zagotovljena uporabnikom, smo raziskali še področje gručenja vozil. Gručenje je postopek, s katerim med seboj povežemo podobne si elemente, v našem primeru vozila, ter tako tvorimo gruče. Njihova uporabna vrednost je večja stabilnost omrežja, saj učinkovito odpravijo problem velike dinamike gibanja vozil. Tako smo tekom raziskav našli več kot 30 različnih algoritmov gručenja vozil v cestnem prometu. Njihove prednosti in slabosti smo upoštevali pri razvoju lastnega protokola gručenja. Velika večina protokolov za gručenje se pri identificiranju vozil s podobnimi vzorci gibanja zanaša na različne lokacijske storitve, predvsem satelitsko pozicioniranje. To predstavlja določeno tveganje za zanesljivo delovanje gručenja, saj lokacijske storitve niso dostopne povsod z enako natančnostjo in zanesljivostjo, kar lahko povzroči odpoved gručenja v npr. parkirnih hišah. V izogib tem težavam smo se pri zasnovi protokola zavestno odpovedali uporabi lokacijskih storitev in protokol zasnovali na metriki medsebojne povezanosti vozil, ki temelji izključno na komunikacijskih zmožnostih vozil. Metrika medsebojne povezanosti vozil, ki smo jo zasnovali, temelji na periodičnih svetilnih okvirjih, ki jih v omrežje oddajajo vsa vozila. Vozila skozi daljše časovno obdobje beležijo neprekinjen pravilen sprejem svetilnih okvirjev okoliških vozil in iz teh podatkov identificirajo tista, ki imajo podoben vzorec gibanja. Očitno je namreč, da lahko daljše časovno obdobje svetilne okvirje pravilno sprejemajo samo tista vozila, ki imajo med seboj podoben vzorec gibanja (pozicijo, smer in hitrost). Ob neuspešnem sprejemu svetilnih okvirjev pa algoritem ta vozila močno kaznuje in se tako odzove na spremembe, ki so posledica poslabšanja komunikacijskih zmožnosti med vozili. V doktorski disertaciji je predstavljen nov protokol gručenja, ki skuša doseči čim boljšo povezljivost vozil med seboj. Vsako vozilo zato stremi k temu, da je povezano z dvema glavama gruče, in ne samo z eno, kot je praksa pri večini drugih protokolov. Na tak način se izognemo večjim in daljšim izpadom povezav ob menjavanju glave gruče, saj je verjetnost hkratnega izpada obeh glav gruč manjša kot verjetnost izpada ene same. Njegova posebnost je tudi obraten način delovanja v primerjavi z vsemi drugimi protokoli, saj je začetna vloga vsakega vozila glava gruče namesto član gruče. Prehod iz člana gruče v glave gruče in obratno je lahko izveden hipno, saj metrika vedno odraža aktualno stanje v omrežju. Razvit protokol smo preizkusili v tandemu mrežnega simulatorja ns-3 in simulatorja gibanja vozil SUMO. Za potrebe testiranja smo razvili nov simulacijski scenarij gibanja vozil med Ljubljano in Medvodami, ki posnema dogajanje običajnega delovnega dne na tem odseku. Simulacije so bile izvedene tako v normalni kot tudi v povečani gostoti vozil, s čimer smo dobili vpogled v obnašanje metrike in protokola gručenja v različnih prometnih situacijah. Rezultati evalvacije razvitega protokola, posredno pa tudi nove metrike medsebojne povezanosti vozil, se kažejo kot zelo pozitivni. V primerjavi s protokolom gručenja MOBIC je povezljivost vozil med seboj opazno povečana, ustvarjene gruče pa bolj stabilne. Razvit protokol odlikuje tudi učinkovitost z vidika količine kontrolnega prometa, kar ga uvršča med bolj primerne za uporabo v urbanih okoljih. V okviru doktorske disertacije smo pokazali, da so pri gradnji gruč možni in učinkoviti tudi drugačni, neobičajni pristopi. Izkazalo se je, da je zelo preprosta metrika lahko zelo učinkovita in zaradi neodvisnosti od lokacijskih storitev uporabna v vseh primerih, uporabili smo več glav gruč za povečanje komunikacijskih sposobnosti brez poslabšanja stabilnosti omrežja, gruče pa gradimo po obrnjenem principu. Razvita metrika in protokol prav tako odpirata veliko novih izzivov za nadaljnje raziskave, razvoj in evalvacije.

Language:Slovenian
Keywords:Inteligentni transportni sistemi, protokol, gručenje, medsebojna povezanost vozil, VANET
Work type:Doctoral dissertation (mb31)
Organization:FE - Faculty of Electrical Engineering
Year:2015
Views:610
Downloads:185
Metadata:XML RDF-CHPDL DC-XML DC-RDF
 
Average score:(0 votes)
Your score:Voting is allowed only to logged in users.
:
Share: Bookmark and Share

Secondary language

Language:English
Title:VEHICLE INTERCONNECTION CLUSTERING PROTOCOL FOR INTELLIGENT TRANSPORTATION SYSTEMS
Abstract:
The era of Internet of things, which will include smart, connected vehicles, is rapidly approaching. It will open the door for new technologies that will have an important role in providing wireless connectivity between a wide variety of devices in the future. This doctoral thesis is focused on organisation and optimisation of wireless vehicular ad-hoc networks in emerging intelligent transportation systems. The nature of highly dynamical vehicle movements present a major challenge in designing a reliable, stable and useful communication network that provides the required quality of service. To become acquainted with the field of inter-vehicular communications, we researched this scientific area and reviewed the related standards. We concluded that the standardisation is not yet finished and is moving in the direction of a unified global standard. Due to different research and development cycles, different regions have standardised more or less the same services in a different manner, which is only now becoming apparent and presents a weakness for a quick and economical deployment. USA, Japan and Europe are now trying to unify the standards before mass deployment begins, and thus avoid unnecessary segmentation. It is expected that these standards will also be adopted by other countries that are not actively participating in the standardisation process. Since the standardization does not deal with network optimization, but merely prescribes the limits for quality of services that must be provided, we focused on the field of vehicle clustering. Clustering is the process of grouping together similar elements, in our case vehicles, to form a cluster. They effectively lower the high vehicle dynamics and stabilize the network. Our research revealed more than 30 different clustering algorithms for vehicle clustering. Their advantages and disadvantages were then taken into account during the development of a new clustering protocol. The vast majority of clustering protocols use location services, especially the satellite positioning system, to identify vehicles with similar movement patterns. This poses a risk for the clustering protocol reliability, because the location services are not available everywhere and their accuracy can vary significantly, e.g. in parking structures. To avoid these problems, we consciously decided against the use of location services and designed a vehicle interconnection metric that solely relies on the communication capabilities between vehicles. The vehicle interconnection metric that we designed is based solely on the periodic beacon frames transmitted by all the vehicles. Vehicles continuously monitor the reception of these beacon frames from other nearby vehicles and identify those with a similar movement pattern. It is evident that only vehicles with similar movement patterns (position, direction and speed) can keep in touch continuously for a longer period of time. In case of erroneous beacon frame reception, the algorithm reacts quickly and strictly, therein handling the communication degradation between vehicles. We designed a new vehicle clustering protocol that pursues the aim of improving the connectivity between vehicles. Each vehicle tends to associate with two cluster heads instead of just one, which is the common case with other clustering protocols. This way, longer connectivity losses are avoided during the reclustering phase, because the vehicle is quite probably connected to the other cluster head. The probability of full connectivity loss is lower if a vehicle is using two cluster heads instead of only one. The speciality of our clustering protocol is also the inverted working principle in which the default role of each vehicle is a cluster head, not a cluster member. The switch from one role to another can be done instantly because the vehicle interconnection metric always reflects the current state of the network. A new vehicle movement simulation scenario between Ljubljana and Medvode was developed, which mimics the vehicle movement on a typical work day on that stretch of the road. The new protocol was tested using this new scenario in the ns-3 network simulator and SUMO vehicle movement simulator tandem. The simulations were performed both in normal as well as in increased vehicle densities, thus providing the insight into the behaviour of the protocol in different traffic scenarios. The evaluation results of the new protocol, and indirectly also of the new vehicle interconnection metric, can be seen as very positive. In comparison with the clustering protocol MOBIC, connectivity between vehicles was increased and the formed clusters are more stable. The new protocol also has quite a low protocol overhead which makes it suitable for use in urban environments. In this thesis, we have shown that unusual, non-conventional clustering approaches are both possible and effective. It turned out that very simple location service independent metrics can be used in all usage scenarios. We also used two cluster heads instead of only one, without compromising the network stability, and an inverted clustering principle with cluster head in the default role. The designed vehicle interconnection metric and clustering protocol are opening new opportunities and challenges for novel scientific research in this field.

Keywords:Intelligent transportation systems, protocol, clustering, vehicle interconnection, VANET

Similar documents

Similar works from RUL:
Similar works from other Slovenian collections:

Comments

Leave comment

You have to log in to leave a comment.

Comments (0)
0 - 0 / 0
 
There are no comments!

Back