Urban Vehicular Network Performance Optimization

Abstract

In urban vehicular ad hoc network (VANET) design, it is always a problem to guarantee the quality of peer node communication for moving nodes. The reason is two-fold, namely the dynamic nature of an ad hoc network, and the complexity of an urban environment. Firstly, communication links between neighboring nodes are constantly established and torn down in an ad hoc network. This momentary phenomenon results in highly unpredictable network behavior, and it degrades the signal transmission performance severely. The second factor, complexity of the urban environment also affects network transmission: a wireless signal may travel across different buildings and materials with different fading qualities; before it finally reaches its destination, the quality of transmitted data becomes unforeseeable. In this paper, we propose a novel wireless sensor network (WSN) to assist VANET transmission in urban areas. Sensors are placed along streets and junctions to assist wireless signal transmission. Then we propose a novel algorithm called the Smart Routing Algorithm (SRA) to control the sensor network. It will search for communication links which guarantee bit error rates (BER) using a genetic algorithm optimization tool. Finally we verify SRA's performance by comparing its quality to the mainstream ad hoc network routing protocol Ad hoc On-demand Distance Vector routing (AODV), using the US city of Boston as an example environment. Simulation shows that SRA can optimize signal quality from 10 -2 to 10 -3 within 10 epochs of optimization rounds, and can optimize links ranging from distances of 100m to 1km. It also can locate links with the minimum number of sensors, for energy conservation purposes. Compared with AODV, SRA is a more efficient and feasible option for path routing optimization. IntroductionIn the past decade, ad hoc networks have been studied by many researchers due to their widespread application in daily life. However, much of the work has been carried out in the free-space environment and assumed that signal propagation follows a simple line of sight (LOS) transmission model [1], [2]. There was thus a dearth of research were executed in the real urban area environment, where wireless signals need to transmit through buildings and across concrete walls before reaching their destinations. This situation lasted until the 2000s, when a transportation based system, the Vehicular Ad hoc Network (VANET) was introduced and investigated in several industrial projects [3], [4], [5]. As described in the subsequent reports and surveys, a VANET is a mobile ad hoc network (MANET) where vehicles act as nodes which are restricted to move along city streets[6], [7]. The VANET is clearly a more realistic modeling of urban ad hoc networks. Unfortunately, previous routing algorithms, such as Ad hoc On-demand Distance Vector routing (AODV) [8] and GPSR [9] were reported to have unsatisfactory performance within the VANET environment [10]. This is because signal transmission in VANETs does not follow the LOS propagation model, a...