Real-time Communication in Vehicular Ad Hoc Networks (VANETs)

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Mobile stations, which have no allocated CFP slots, contend and negotiate an agreement on slot allocation in the CP and transmit data packets using the allocated slots in the CFP. The CFP and CP constitute a TBMAC cycle. In a TBMAC cycle, medium access in the CFP is similar to TDMA, while in the CP it is similar to CSMA. Unlike the PCF (Point Coordination Function) of the IEEE 802.11 standard, the TBMAC protocol is not dependent on a particular point coordinator. To ensure every station in a TBMAC cell comes to a consistent view of CFP slot assignments, a lightweight synchronous atomic broadcast protocol is exploited. The TBMAC protocol uses two data structures, Slot Owners and Slot Bitmap. Slot Owners stores mobile stations addresses and the corresponding allocated CFP slots. Slot Bitmap uses two bits to represent the four possible states for each slot: Owner, Other, Collision, Available. The Slot Bitmap, together with source and destination, current slot number, message type, protocol extensions and additional information, makes up the CFP header which is included in the packet a mobile host sends in its CFP slot. CFP slot management is composed of three parts: • Allocating a Slot • Deallocating a Slot • Inter-Cell Communication 12
Clock synchronisation is necessary for the TBMAC protocol to achieve slot management. GPS facilitates to establish clock synchronisation of all mobile stations in the network with microsecond-level precision. The TBMAC protocol handles slot allocation in these potential scenarios as follows: • One station enters or powers on in an active cell. • Two or more stations attempt to join an active cell at the same time. • One station enters or powers on in an empty cell. • Two or more stations attempt to join a cell nearly simultaneously. Roughly, when a joining station is in need of slot allocation, it will monitor the current state of the cell, then floods requests and negotiates an agreement on slot allocation in the CFP. On the other hand, a set of atomic broadcast metrics is utilized to deal with Slot Deallocation in the TBAMC protocol. If there is a demand for inter-cell communication between two mobile stations in adjoining cells, two particular inter-cell CFP slots will be allocated to the two cells respectively. In a new version of TBMAC protocol, an Inter-cell Communication Period (ICP) is proposed especially for message exchange between cells. Apart from the CFP and the CP, the new scheme of TBMAC assigns a time period especially for inter-cell message exchange. Once a mobile node attempts to send packets to another node in adjoining cell, it issues a request. 13
Page 1 and 2: Real-time Communication in Vehicula
Page 3 and 4: PERMISSION TO LEND AND/OR COPY I ag
Page 5 and 6: ABSTRACT Ad hoc networks in which n
Page 7 and 8: 3.4.1.1 Ns-2 . . . . . . . . . . .
Page 9 and 10: 5.3.3.1 Dynamic object . . . . . .
Page 11 and 12: LIST OF FIGURES Figure 2.1: Time Re
Page 13 and 14: Chapter 1 Introduction In this chap
Page 15 and 16: 1.3 Objective For this dissertation
Page 17 and 18: Chapter 2 Background In this chapte
Page 19 and 20: Figure 2.2 Backoff Process 2.2 MANE
Page 21 and 22: In VANETs scenarios there are three
Page 23: number of stations in the network [
Page 27 and 28: Chapter 3 Related Works In this cha
Page 29 and 30: 3.2 MAC Protocol The MAC layer is t
Page 31 and 32: Figure 3.1 Classification of MAC Pr
Page 33 and 34: 3.3.2 Source-driven Routing Protoco
Page 35 and 36: In VANETs, limited resource (e.g. b
Page 37 and 38: 3.4.1.3 TOSSIM / TOSSF TOSSIM [54]
Page 39 and 40: Chapter 4 DESIGN After covering muc
Page 41 and 42: 4.2.2 Individual Behaviour Differen
Page 43 and 44: learning about the system. In [34],
Page 45 and 46: is specified as an entity. An entit
Page 47 and 48: Object Oriented Programming differs
Page 49 and 50: 4.5.2 Roadway Layout As mentioned a
Page 51 and 52: 4.5.4.1 Intra-cell communication Ac
Page 53 and 54: 4.6 TBMAC Application Programming I
Page 55 and 56: 4.7.1.1 Clock synchronisation First
Page 57 and 58: When a vehicle is going to leave a
Page 59 and 60: 4.8 Summary In this chapter we firs
Page 61 and 62: To avoid the confusion from the den
Page 63 and 64: 5.3 Components 5.3.1 Roadway We app
Page 65 and 66: Through above steps, we can get a r
Page 67 and 68: 5.3.3 Vehicle 5.3.3.1 Dynamic objec
Page 69 and 70: For a driving vehicle A, if there i
Page 71 and 72: Thread to implement the enter() met
Page 73 and 74: In the end, we join the above appro
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Chapter 6 Evaluation This Chapter i
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many classes were put in the packet
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6.3.1 Vehicular Mobility Model Rand
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6.3.5 Software Usability The TBMAC
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Chapter 7 Conclusion 7.1 Summary In
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7.3 Lessons Learned In this project
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[7] Y.-B. Ko and N. H. Vaidya, “G
Page 89 and 90:
[19] M. Ergen, et al., “Wireless
Page 91 and 92:
[36] J. Misra, “Distributed discr
Page 93 and 94:
[51] “DSRC—Dedicated Short Rang
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Real-time Communication in Vehicular Ad Hoc Networks (VANETs)

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