Modern vehicles incorporate tens of sensors to provide vital sensor information such as temperature, air quality, tire pressure, distances to nearby objects, etc., for the electronic control units (ECUs). The ECUs in vehicles then utilize the sensor information for various control functions and applications. In the current architecture, the sensors in a vehicle are connected to the ECUs via physical wires. As the number of electronic components keeps increasing with the development of new features in the vehicles, the number of in-vehicle sensors could be more than a few hundred in the near future. Physical wires between the ECUs and the sensors could become problematic due to the following reasons: (i) Wires are expensive. Wires are usually shielded so that they are heat and interference resistant. The cost of the materials as well as the engineering efforts to design the layout of the wires will become more significant with the increase in the number of sensors; (ii) Wires are heavy. Wires and wiring harness are among the heaviest components in a vehicle and could have a large impact on fuel efficiency in the near future; and (iii) Wires are restrictive. There are several locations in the vehicle where sensors cannot be deployed with the current wired architecture; e.g., steering wheel, tires, and windshields. It is thus imperative to create a new open architecture to support communications between sensors and the ECUs for future vehicles. To address the aforementioned issues, we propose to create an intra-car wireless sensor network, which replaces physical connecting wires with wireless technology. In this thesis, we present the results of an extensive set of measurements which characterize the intra-car wireless channels in both time dispersion and time variation aspects as well as a set of IEEE 802.15.4 link measurements carried out in infra-car wireless sensor network testbeds. These measurement results provide insights into the design and the implementation of the intra-car wireless sensor networks. Based on the results, we also propose the use of code division multiple access (COMA) as the media access control (MAC) protocol for the intra-car wireless sensor networks. Numerical results based on the analytical model we developed show that COMA can outperform the conventional choice, time division multiple access (TDMA), in terms of network capacity, while the two protocols are comparable in terms of sensor node lifetime.
|School:||Carnegie Mellon University|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 71/06, Dissertation Abstracts International|
|Subjects:||Electrical engineering, Computer science|
|Keywords:||CDMA, Electronic control units, Intracar channels, Wireless sensor networks|
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