Research Of APTS Wireless Ad Hoc Network

APTS (Advanced Public Transportation System) is an advanced public transportation management system which sets intelligent scheduling, electronic toll collection, information services, network communication in one. Its goal is to achieve information and intelligence of public transportion scheduling, operation and management, to provide convenient public transportion services. It can effectively solve urban traffic problems through attracting bus trips.APTS based on LR-WPAN (Low-Rate wireless Personal Area Network) protocol standard IEEE 802.15.4 makes use of RF communication technology, embedded technology, GPS positioning technology and other technologies to construct APTS wireless ad hoc network along the urban lines, through which public transportation operational information can be collected and transmitted. Compared with those systems which use CDMA, GPRS or CDPD for wireless data transmitting, our system costs lower, does not require network usage charges, and can easily be expanded. IEEE 802.15.4 standard provides the physical layer and the media access control layer specifications, but does not address specifications above the network layer. In order to ensure real-time transmission and distribution of the public transportion operational information, the routing protocol must be achieved to guide information transmission, which increases technical difficulty of the system implementation.In this paper, the multi-hop network scheme of APTS wireless ad hoc network is designed on analysis of the real urban bus lines and sites distribution. Next, according to the characteristics and requirements of APTS wireless ad hoc network, routing protocols for APTS wireless ad hoc network are designed on study of a variety of wireless ad hoc network routing protocols, and the network layer based on IEEE 802.15.4 is implemented. Finally, simulation experiments of routing protocols using NS2 are made. The simulation results show that, the proposed routing protocol can not only achieve complete self-organization of site nodes to establish route, but also meet the reliability and real-time requirements of all kinds of data transmission in APTS wireless ad hoc networks.