Volume 61 Issue 2 (2011) - Годишник на ТУ - София - Технически ...

PDA with WindowsMobile operating system - smallgeneral purpose pocket computer,on which specialized softwarefor navigation and processingof client requests. It implementsthe interface betweenthe driver and the system; Microphone and loudspeakers- used for verbal communicationbetween the driverand the dispatcher;Fig. 3 Vehicles with onboard computersBecause in today's fast developing technologically world the requirements for datatransmission and processing are constantly rising the functionality of the communicationmodule have to continuously be improved, depending on the current hardwareand software solutions on the market.3. Functional requirements for the design of thecommunication moduleThe communication module is responsible for transmission and processing of thedata, received from onboard computers and for processing the actions of the dispatchersin the system. The main requirement is that this module has to operate continuously.This requires the use of specialized hardware and software designed to workwith the least possible disruption in the service, even in the case of hardware failure.3.1. Hardware requirementsThe requirement for continuous operation of the system requires the use of HA (HighAvailability) hardware. The main feature of the HA hardware is the lack of singlepoint of failure, or SPOF. SPOF may be any device or software which will stop allwork in the event of failure. Common example of this is a single firewall that controlsthe access to the Internet (Figure 4). Commonly used high available hardware is theHA cluster (Figure 5). The main idea is to have a server with redundant components.The work can be transferred online to another identical component in the case ofhardware failure, avoiding the presence of single point of failure [1].3.2. System software requirementsThe system software must be able to manage the used specialized hardware. Thereforethere are requirements for: Virtualization - platform virtualization software may be used to facilitate themaintenance and future development of the system. Platform virtualization is a kindof system software which creates a virtual computer. The virtual computer is a softwarerepresentation of a computer. In the virtual environment, a single physical com-192