Timothy J. Talty

Performance evaluation of safety applications over DSRC vehicular ad hoc networks

In this paper we conduct a feasibility study of delay-critical safety applications over vehicular ad hoc networks based on the emerging dedicated short range communications (DSRC) standard. In particular, we quantify the bit error rate, throughput and latency associated with vehicle collision avoidance applications running on top of mobile ad hoc networks employing the physical and MAC layers of DSRC. Towards this objective, the study goes through two phases. First, we conduct a detailed simulation study of the DSRC physical layer in order to judge the link bit error rate performance under a wide variety of vehicles speeds and multi-path delay spreads. We observe that the physical layer is highly immune to large delay spreads that might arise in the highway environment whereas performance degrades considerably at high speeds in a multi-path environment. Second, we develop a simulation testbed for a DSRC vehicular ad hoc network executing vehicle collision avoidance applications in an attempt to gauge the level of support the DSRC standard provides for this type of applications. Initial results reveal that DSRC achieves promising latency performance, yet, the throughput performance needs further improvement.

Zigbee-based intra-car wireless sensor networks: a case study

There is a growing interest in eliminating the wires connecting sensors to the microprocessors in cars due to an increasing number of sensors deployed in modern cars. One option for implementing an intra-car wireless sensor network is the use of ZigBee technology. In this article we report the results of a ZigBee-based case study conducted in a vehicle. Overall, the results of the experiments and measurements show that ZigBee is a viable and promising technology for implementing an intra-car wireless sensor network.

Potential for Intra-Vehicle Wireless Automotive Sensor Networks

We propose using a wireless network to facilitate communications between sensors/switches and control units located within a vehicle. In a typical modern vehicle, the most demanding sensor will require a latency of approximately less than 1 msec with throughput of 12 kbps. Further, the network will need to support about 15 sensors with this requirement. The least demanding sensor will require a latency of approximately 50 msec with data throughput rate of 5 bps and will need to support about 20 of these types of devices. Initial part of this paper gives an overview of the issues spanning several layers of the protocol stack. Then, we focus on the Medium access control (MAC) layer and derive necessary design parameters based on given network requirements. We evaluate the IEEE 802.15.4 standard with respect to its suitability for use in a prospective intra-vehicle wireless sensor network.

Feasibility of In-car Wireless Sensor Networks: A Statistical Evaluation

Statistical characterization of in-car wireless communication channels has recently gained significance, mainly due to the possibility of deploying a wireless sensor network in the vehicle. In this paper, we report different aspects of a statistical analysis of four representative in- car wireless channels based on the received power data collected from a binary phase shift keying (BPSK) transmission experiment. It is shown that the communication channel between the base station and a sensor placed under the engine compartment is the worst in terms of stability, average fade duration, and fade proportion, while the channel between the base station and a sensor placed in the trunk and the channel between the base station and a sensor placed on the hood are the best. We also show that the 4 representative in-car wireless channels can satisfy the maximum packet delay requirement of less than 500 ms and the trunk channel and the in-the-engine-compartment channels can satisfy the requirement of up to 98% packet reception rate. These statistical characteristics of the in- car wireless channels provide important guidelines for the designer of an in-car sensor system.

On the potential of bluetooth low energy technology for vehicular applications

With the increasing number of sensors in modern vehicles, using an intra-vehicular wireless sensor network (IVWSN) is a possible solution for the automotive industry for addressing the potential issues that arise from additional wiring harness. Such a solution could help car manufacturers develop vehicles that have better fuel economy and performance, in addition to supporting new applications. However, which wireless technology should be used for maximizing the benefits of IVWSNs is still an open issue. In this article we propose to use a new wireless technology known as Bluetooth Low Energy (BLE) and outline a new architecture for IVWSN. Based on a comprehensive study that encompasses an example application, it is shown that BLE is an excellent option that can be used in IVWSNs for certain applications mainly due to its good performance and low-power, lowcomplexity, and low-cost attributes.

ZigBee-based Intra-car Wireless Sensor Network

Due to an increasing number of sensors deployed in cars, recently there is a growing interest in implementing a wireless sensor network within a car. In this paper, we report the results of packet transmission experiments using ZigBee sensor nodes within a car under various scenarios. The results of the experiments suggest that both Received Signal Strength Indicator (RSSI) and Link Quality Indicator (LQI) can only be used as a threshold-based indicator to evaluate the link quality - indicating poor link quality when dropping below a certain threshold. Preliminary experimental results show that a detection algorithm developed by the authors based on RSSI/LQI/error patterns and an adaptive strategy might increase the goodput performance of the link while improving power consumption of the radio.

Intra-vehicular Wireless Networks

Automotive wiring harnesses that provide the wiring infrastructure for electrical and electronic sub-systems inside vehicles have grown in size over the years. Significant engineering challenges are posed due to increased weight/decreased fuel economy, increase in production steps, increased cost and labor in harness manufacturing and installation, increased design complexity, etc. wireless communications provides an intriguing alternative to wiring. This paper investigates the issues around replacing the current wired data links between electrical control units (ECU) and sensors/switches in a vehicle, with wireless links. We present a wide range of engineering issues and discuss potential solutions. We also provide recommendations with regard to future wireless intra- vehicular networks. Specifically, we provide a discussion on limitations and opportunities, based on simulation results, for network operations over an IEEE 802.15.4 stack protocol.

Channel Characterization for Ultra-Wideband Intra-Vehicle Sensor Networks

This paper presents an ultra-wideband (UWB) testbed and its application to characterize channels for intra-vehicle automotive sensor networks. A received pulse width of 300 ps is achieved both in laboratory environment and outdoor over 60 m. Channel characteristics are thoroughly measured for a car. Different settings are investigated, including UWB signal propagation from rear wheels to the engine compartment area, within the engine compartment, and from within the engine compartment to the passenger compartment. The study found: (a) communications between a transceiver at the bottom of the engine compartment and rear wheel speed sensors can be achieved at 330 mega-pulses per second using UWB technology without inter-symbol interference; (b) When the hood is shut, UWB communications within the engine compartment can achieve 476 mega-pulses per second when there is a line-of-sight, or 50 mega pulses per second when there is no line-of-sight; (c) The received signals for UWB communications within the vehicle are very stable, and have negligible fading. Pulses traveled through different paths are distinct in the received signals. This means that the UWB technology has resolved multipath. Therefore, UWB can provide sufficiently high data rate for hundreds of wireless sensors in future automotive vehicles. The negligible fading in the received signals makes it much easier to design transceivers with low cost and low complexity

Intra-Vehicle UWB Channel Measurements and Statistical Analysis

Ultra-wideband (UWB) technique attracts attention from automotive manufacturers as a potential way to construct intra-vehicle wireless sensor network. This paper reports our preliminary effort in measuring and modeling the UWB propagation in the commercial vehicle environment. Two cases of time domain channel measurement results are reported. In one case, the antennas are inside the engine compartment. In the other case, both antennas are beneath the chassis. It is observed that clustering phenomenon exists in the former case but not in the latter one. Different channel models are used to describe UWB propagation in the two cases and model parameters are found by statistically analyzing the impulse responses.

Ultra-wideband channel modeling for intravehicle environment

With its fine immunity to multipath fading, ultra-wideband (UWB) is considered to be a potential technique in constructing intravehicle wireless sensor networks. In the UWB literature, extensive measuring and modeling work have been done for indoor or outdoor propagation, but very few measurements were performed in intravehicle environments. This paper reports our effort in measuring and modeling the UWB propagation channel in commercial vehicle environment. In our experiment, channel sounding is performed in time domain for two environments. In one environment, the transmitting and the receiving antennas are put beneath the chassis. In another environment, both antennas are located inside the engine compartment. It is observed that paths arrive in clusters in the latter environment but such clustering phenomenon does not exist in the former case. Different multipath models are used to describe the two different propagation channels. For the engine compartment environment, we describe the multipath propagation with the classical S-V model. And for the chassis environment, the channel impulse response is just represented as the sum of multiple paths. Observation reveals that the power delay profile (PDP) in this environment does not start with a sharp maximum but has a rising edge. A modified S-V PDP model is used to account for this rising edge. Based on the analysis of the measured data, channel model parameters are extracted for both environments.