01.12.2016 | Research | Ausgabe 1/2016 Open Access

# Evaluation of efficient vehicular ad hoc networks based on a maximum distance routing algorithm

## 1 Introduction

_{ f }) and communication lifetime (CLT

_{ f }) factors have been defined to determine the optimal next hop node. Dist

_{ f }is computed to select the closest node toward the destination, and CLT

_{ f }represents the duration for which a node remains in the radio range of the forwarder.

## 2 Related woks

### 2.1 Topology-based routing protocols

### 2.2 Position-based routing protocols

## 3 MDORA

### 3.1 Assumption

### 3.2 Description of MDORA

#### 3.2.1 Ad hoc region discovery phase

_{ f }) in finding the next hop neighbor vehicle is presented in Fig. 5. Line segment SD joining the source and the destination is drawn to project vehicles n

_{1}and n

_{2}. The shortest distance between the source and destination vehicles is denoted by DC whereas d and d′ denote the distances from intermediate vehicles (n

_{1}and n

_{2}) to the source and the destination, respectively. Dn

_{ 1 }and Dn

_{ 2 }are the distances that measure the progress of vehicles n

_{1}and n

_{2}from the source vehicle toward the destination vehicle, and this distance can be calculated from the formula below, which is defined as follows:

_{ f }) toward the destination will be selected as the next hop. Figure 5 shows that according to the distance factor selection, vehicle n

_{2}should be preferred to vehicle n

_{1}.

_{ f }) defines the duration for which a vehicle remains in the radio range of the forwarder. Thus, while selecting the next hop, based on the communication lifetime factor, a vehicle predicts the communication link expiration time with its neighbors. It is assumed that two vehicles, i and j, are within each other’s transmission range denoted by r, coordinates (x

_{i}, y

_{i}) and (x

_{j}, y

_{j}). Also, let v

_{i}and v

_{j}be the velocities of vehicles i and j, respectively. CLT

_{ f }between two vehicles will be computed as follows:

_{i}−v

_{j}, b = x

_{i}−x

_{j}, and c = y

_{i}−y

_{j}

_{i}= v

_{j}, the communication lifetime CLT

_{ f }becomes infinity.

_{ f }and CLT

_{ f }factors for each neighbor vehicle, the source vehicle initiates a neighbor table (Neighbor_table) comprising of Neig_ID, Dist

_{ f }, and CLT

_{ f }. Then, the source vehicle sorts the Neighbor_table according to the Dist

_{ f }factor, which is the highest Dist

_{ f }, first (algorithm 1—lines 15 to 18).

#### 3.2.2 Route establishment and data transmission phase

_{ f }and computed as in Eq. (2). From Neighbor_table, MDORA checks the CLT

_{ f }of the next hop vehicle to be sure that this vehicle remains in the communication range of the forwarder. Hence, one metric is defined as the communication lifetime threshold (C

_{LT}_Threshold), which is the minimum time needed for the data transmission process. It is used to evaluate the communication lifetime of the next hop vehicle. If CLT

_{ f }of the next hop vehicle is greater or equal to C

_{LT}_Threshold, then the current vehicle starts forwarding the packet to the next hop vehicle, as shown in algorithm 2—lines 5 and 6. Otherwise, if that condition is false, then the vehicle entry is removed from the Neighbor_table, a new head of the Neighbor_table is set as the next hop vehicle, and the verification condition of CLT

_{ f }is repeated. Finally, the algorithm compares the destination vehicle identifier (D_ID) with Neig_ID of the next hop vehicle. If the identifiers are identical, then the algorithm is terminated. Otherwise, if the identifiers are not identical, then the next hop vehicle broadcasts Hello_msg and starts the ad hoc region discovery phase. This procedure will continue until the destination vehicle is reached as shown in Fig. 6. Algorithm 2 presents the detail of the route establishment and data transmission phase in MDORA.

## 4 Performance evaluations

### 4.1 Scenario implementation

### 4.2 Result analysis

Parameter | Value |
---|---|

Simulation area | 3 km * 5 km |

Number of lanes | 2 Bidirectional |

Number of vehicles | 1000 |

Velocity | (40–80) km/h |

Communication radius | 100 m |

MAC protocol | IEEE 802.11p |

Peak time | (6:00–8:00) a.m. and (2:00–4:00) p.m. |

Normal time | 08:00 a.m.–02:00 p.m. |

Transmission rate | 5 packet/s |

Transmit power | 23 dBm |

Path loss model | Log-distance |

Control message size | 64 bytes |

Packet size | 512 bytes |

Simulation time | 300 s |