Abstract
Position is a vital element for ITS applications. Its accuracy helps to deliver services quickly to drivers to increase their satisfaction. GPS is a well-known position system but it suffers from multipath effect and non-line of sight in tunnel environments. Relative Position or sometimes called cooperative localization is an alternative position estimation. It utilizes different forms of v2x communication to exchange position, distance, direction, and velocity parameters. It will benefit in collecting a large amount of data to increase the accuracy of position estimation. However, the dependency of radio range communication methods has drawbacks such as poor-received signal, multipath, lose packets, delay, and overhead communication that will have inverse impact on position accuracy. In addition, safety applications require fewer seconds to make quick response. This chapter provides the latest related papers, the state art of radio range, the well-known localization algorithms, and current challenges and future direction.
TopIntroduction:
By increasing the development in car manufacturing and increasing the number of vehicles. There is a necessary need to feel drivers more comfortable and provide more services during driving tour. Intelligent transportation systems (ITS) depend more on vehicle position to provide more services like warning system and driver assistance. As a result, localization accuracy is the main challenge especially in urban and tunnel environment (Mrunmayi S Sahasrabudhe et al, 2014). Global position system (GPS) is a well-known absolute position system. Its accuracy is limited to 10m: 30m (K. Golestan et al, 2015). It requires line of sight condition and suffers from multipath. Differential GPS (DGPS) is an extension of GPS (Rainer Mautz, 2012). It consists a set of stationary nodes or roadside units (RSU)and vehicle nodes. Roadside units are placed at known position in advance. In addition, they calculate the correction rates (i.e. localization error) and send them to nearby mobile vehicles. Unknown vehicle uses these corrections to fix its position calculation. DGPS achieves accuracy level about ten of centimeters. The drawbacks of DGPS are (A. Benslimane, 2005):
- 1.
Both mobile and stationary nodes must be within coverage area of each other. Otherwise, vehicles cannot use correction rate.
- 2.
Large number of roadside units represents high cost deployment.
- 3.
The local error of pseudo range measurement still exists.
Key Terms in this Chapter
Localization Error: is the difference between true position and estimated position.
Relative Position: is an alternative name of cooperative localization. It means that determined position with the help of nearby vehicle or roadside units.
Time of Arrival: The distance is measured as the time of the received signal.
Round Trip Time: is a sum of signal travelling time t1 from transmitter to a receiver and received signal time t2 from receiver to transmitter.
Angle of Arrival: The receiver node senses the direction of the received signal.
Absolute Position: position is determined by GPS or inertial navigation system.
Time Difference of Arrival: The distance is the difference time of received two different signals.