Intra-Vehicular Wireless Sensor Networks Research Articles

MmWave channel model for intra-vehicular wireless sensor networks

Intra-vehicular wireless sensor networks (IVWSNs) have significant potential to reduce part, manufacturing and repair costs, facilitate the integration of new nodes and provide more freedom for the sensor placement in previously impossible locations by obviating the need for wiring harness. mmWave stands up as a promising candidate to fulfill the high reliability, security and low latency requirements of IVWSNs, exploiting the availability of large bandwidth at high frequencies and high nominal gains with directional antennas while attenuating through the car body significantly. This work focuses on building a mmWave channel model for IVWSNs. The model is built for the engine compartment, passenger compartment and beneath the chassis of a vehicle by conducting vast number of measurements for 14 × 14, 13 × 13 and 15 × 15 transmitter and receiver links in a Fiat Linea, respectively. The path loss exponent is approximately 3, showing almost no variation within different compartments. The power variation around the path loss model has a Generalized Extreme Value (GEV) distribution with zero mean for all compartments and 5 dB standard deviation for the engine compartment and approximately 7.6 dB standard deviation for the other two compartments. A modified Saleh–Valenzuela (SV) model is used to represent the clustering of power delay profiles (PDPs). Log-normal distribution is used to model the inter-arrival times of clusters, while the dependencies of cluster amplitude and ray decay rate on the cluster arrival times are represented by a dual slope linear fit model with breakpoints 1.2 ns and 5.6 ns for engine compartment, respectively, and 1.6 ns and 2.6 ns for the other two compartments, respectively. The experimental PDPs vary around the SV model and these variations are represented by a normal distribution with zero mean and 5.8 dB standard deviation, which is independent of both the delay bins and the compartment of the vehicle. All these findings are used to build a simulation model for each compartment of the vehicle. The simulation model is validated by comparing the distributions of the received powers and Root Mean Square (RMS) delay spreads of the experimental and simulated PDPs.

Empirical Feasibility Analysis for Energy Harvesting Intravehicular Wireless Sensor Networks

Vehicle systems currently utilize wired networks for power delivery and communication between nodes. Wired networks cannot practically accommodate nodes in moving parts and with the increasing functional complexity in vehicles, they require kilometer-long harnesses, significantly increasing fuel consumption, manufacturing, and design costs. Alternatively, energy harvesting intravehicular wireless sensor networks (IVWSNs) can accommodate nodes in all locations and they obviate the need for wiring, significantly lowering costs. This article empirically analyzes the feasibility of such an IVWSN framework via extensive in-vehicle measurements for communications at 2.4 GHz, ultrawideband (UWB), and millimeter-wave (mmWave) together with radio frequency (RF), thermal, and vibration energy harvesting. Our analyses indicate mmWave performs best for short Line-of-Sight (LoS) links in the engine compartment with performance close to UWB for LoS links in the chassis and passenger compartments considering worst case signal-to-interference-and-noise ratio (SINR). For non-LoS links, which appear mostly in the engine compartment and chassis, UWB provides the highest security and reliability. 2.4 GHz suffers heavily from interference in all compartments while UWB utilizes narrowband suppression techniques at the cost of lower bandwidth; mmWave inherently experiences very low interference due to its propagation characteristics. On the other hand, RF energy harvesting provides up to 1 mW of power in all compartments. Vibration and thermal energy harvesters can supply nodes consuming <; 10 mW in the engine compartment and <; 5 mW nodes in the chassis. In the passenger compartment, thermal harvesting is not available due to low temperature gradients, but vibration and RF sources can supply <; 1 mW nodes.

A scalable hybrid MAC strategy for traffic-differentiated IoT-enabled intra-vehicular networks

The increasing popularity of Internet of Things-enabled Intra-Vehicular Wireless Sensor Networks (IoT-IVWSNs) relying on IEEE 802.15.4 standard has generated a massive amount of wireless data traffic and put a great pressure in the network functionalities. Along this trend, the existing medium-access control (MAC) protocol struggles to keep up with the unprecedented demand of vehicle monitoring sensors simultaneously emitting data, which can lead to packet collisions, severe network congestion and lost of time-critical data, due to the inflexible characteristics of the protocol. In order to mitigate these issues, this work proposes an enhanced MAC scheme that is scalable to account for diverse sensor-traffic quality of services. The hybrid scheme aims to effectively combine two procedures, namely history- and priority-based MAC, to allocate appropriate network resources for smooth transmission flow from multiple sensors. History-based MAC exploits historical contention data to optimize a near-future contention window that aims to minimize packet collision and expedite the average data delivery. Priority-based MAC assigns priority based on the time-criticality of the sensing data, which is subsequently being used to schedules network resources. Numerical results show the desirable performance of the hybrid scheme for IoT-IVWSNs in comparison to the existing MAC and sole history-based or priority-based strategies in the context of packet delivery ratio and transmission delay.

Use of UWB Impulse Radio Technology in In-Car Communications: Power Limits and Optimization

In-car wireless data communications systems require a short-range unlicensed radio communications technology that causes a very low level of interference in the other, already deployed radio links and networks, offers low and medium data rate, can reuse the already occupied radio-frequency (RF) bands, and assures low probability of message collisions. Ultrawide band (UWB) impulse radio employs RF pulses with very short duration to carry the information; consequently, it is an optimal candidate for the in-car wireless communications and intravehicular wireless sensor networks. Data rate and shape of RF carrier pulse determine the performance of a UWB radio link. To limit the interference caused, the maximum power radiated by an UWB device is restricted by the Federal Communications Commission (FCC) in the U.S. Introducing a new mathematical model and starting from the FCC regulations, analytical expressions for the calculation of FCC power limits are derived here. It is shown that the low- and high-rate UWB impulse radio systems are peak and average power limited, respectively. The relationship between the mathematical model and the parameters of an UWB carrier pulse used in a built UWB radio is established. The performances of RF carrier pulses known from the literature are evaluated and compared. All expressions derived are verified by measurements.

A performance investigation on IoT enabled intra-vehicular wireless sensor networks

The concept of Internet of Things (IoT) can be utilised in vehicles, since the number of sensor nodes in vehicles is rising tremendously because of the uplifting demand of applications for security, safety and convenience. In order to establish the communication among these nodes inside a vehicle, a controller area network with wired architecture provides a prominent solution. However, this solution is not flexible because of the architectural complexity and the demand for a large number of sensors inside the vehicle; hence wired architectures are replaced by wireless ones. Moreover, scalability will be an important issue while introducing the IoT concept in Intra-Vehicular Wireless Sensor Networks (IVWSNs). In this paper, a comprehensive performance investigation on the IoT enabled IVWSNs (IoT-IVWSNs) to be carried out in order to address this issue. The overview of the IoT-IVWSNs with a comparative study of the existing technologies and the design challenges for such network are provided. The link design between an end-device and the control unit is analysed, and the performance of the network has been investigated and some open research issues are addressed. It reveals that the delay in packet transmission increases due to higher traffic loads and the number of end-devices. This result demonstrates that the existing MAC protocol works well for a small network (i.e., a network with a maximum number of 50 nodes) but is not suitable for a large network (i.e., a network with more than 50 nodes). The outcome of this research helps to design a smart car system.

A Blind Zone Alert System Based on Intra-Vehicular Wireless Sensor Networks

Due to the increasing number of sensors deployed in modern vehicles, intra-vehicular wireless sensor networks (IVWSNs) have recently received a lot of attention in the automotive industry, as they can reduce the amount of wiring harness inside a vehicle. By removing the wires, car manufacturers can reduce the weight of a vehicle and improve engine performance, fuel economy, and reliability. In addition to these direct benefits, an IVWSN is a versatile platform that can support other vehicular applications as well. An example application, known as a side blind zone alert (SBZA) system, which monitors the blind zone of the vehicle and alerts the driver in a timely manner to prevent collisions, is discussed in this paper. The performance of the IVWSN-based SBZA system is evaluated via real experiments conducted on two test vehicles. Our results show that the proposed system can achieve approximately 95%-99% detection rate with less than 15% false alarm rate. Compared with commercial systems using radars or cameras, the main benefit of the IVWSN-based SBZA is substantially lower cost.

Engine Compartment UWB Channel Model for Intravehicular Wireless Sensor Networks

Intravehicular wireless sensor network (IVWSN) is a cutting edge research topic that delivers cost reduction, assembly, and maintenance efficiency by removing the wiring harnesses within the vehicle and enables the integration of new sensors into the locations inside a vehicle where cable connection is not possible. Providing energy efficiency through the low-duty-cycle operation and high reliability by exploiting the large bandwidth, ultrawideband (UWB) has been determined to be the most appropriate technology for IVWSNs. We investigate the UWB channel model for IVWSNs within the engine compartment of a vehicle by collecting an extensive amount of data for 19 × 19 links for different types and conditions of the vehicle. These include a Fiat Linea with engine off, Fiat Linea with engine on, and Peugeot Bipper with engine off. The path-loss exponent is estimated to be around 3.5 without exhibiting much variation when the engine is turned on and for different types of vehicles. The power variation around the expected path loss has lognormal distribution with zero mean and standard deviation in the range of [5.5, 6.3] dB for different types of vehicles with almost no variation when the engine of the same vehicle is turned on. The clustering phenomenon in the power delay profile (PDP) is well represented by a modified Saleh-Valenzuela (SV) model. The interarrival times of the clusters are modeled using a Weibull distribution. The cluster-amplitude and ray-amplitude decay functions are represented with a dual-slope linear model with breakpoint around 26.6 and 5.5 ns, respectively. The parameters of the Weibull distribution and these dual-slope linear models do not vary significantly for different types and conditions of the vehicle. The variations of the observed PDPs around the SV model is well modeled by independent normal random variables with zero mean and with a variance independent of the delay bin, and the type and condition of the vehicle. We propose a simulation model for the UWB channel within the engine compartment based on these findings and validate it by comparing the received energy and root mean square (RMS) delay spread of the generated and observed PDPs.

Ultra-wideband Channel Model for Intra-vehicular Wireless Sensor Networks Beneath the Chassis: From Statistical Model to Simulations

Intra-vehicular wireless sensor networks (IVWSNs) are a promising new research area that can provide part cost, assembly, maintenance savings, and fuel efficiency through the elimination of the wires, and enable new sensor technologies to be integrated into vehicles, which would otherwise be impossible using wired means, such as intelligent tires. The most suitable technology that can meet the high reliability requirement of vehicle control systems and the strict energy efficiency requirement of the sensor nodes in such harsh environment containing a large number of metal reflectors at short distance is the ultra-wideband (UWB). However, there are currently no detailed models describing the UWB channel for IVWSNs, making it difficult to design a suitable communication system. We analyze the small-scale and large-scale statistics of the UWB channel beneath the chassis of a vehicle by collecting data at various locations with 81 measurement points per transmitter-receiver pair for different types of vehicles, including the scenarios of turning the engine on and movement on the road. Collecting multiple measurements allows us to both improve the accuracy of the large-scale fading representation and model small-scale fading characteristics. The path-loss exponent around the tires and other locations beneath the chassis are found to be very different, requiring separate models. The power variation around the path loss has lognormal distribution. The clustering phenomenon observed in the averaged power delay profile (PDP) is well characterized by the Saleh-Valenzuela (SV) model. The cluster amplitude and decay rate are formulated as a function of the cluster arrival times using dual-slope linear models. Cluster interarrival times are modeled using Weibull distribution, providing a better fit than the commonly used exponential distribution in the literature, mainly due to the nonrandomness of the local structure of the vehicle. The variations of local PDPs around the small-scale averaged (SSA) PDPs, in decibels, at each delay bin are modeled by Gaussian distribution with variance independent of the value of the delay and distance between the transmitter and the receiver. The analysis of the model parameters for different vehicles and different scenarios demonstrates the robustness of our modeling approach exhibiting small variance in channel parameters for different vehicle types. Finally, the algorithm for generating the channel model is given. The generated PDPs are in good agreement with the experimental profiles, validating our model.

Optimal Power Control, Rate Adaptation, and Scheduling for UWB-Based Intravehicular Wireless Sensor Networks

The intravehicular wireless sensor network (IVWSN) is a promising new research area that can provide part cost, assembly, maintenance savings, and fuel efficiency through the elimination of the wires and enables new sensor technologies to be integrated into vehicles, which would otherwise be impossible using wired means such as Intelligent Tire. The close interaction of communication with control systems, strict reliability, energy efficiency, and delay requirements in such a harsh environment that contains a large number of reflectors that operate at extreme temperatures are distinguishing properties of this network. In this paper, we investigate optimal power control, rate adaptation, and scheduling for an ultrawideband-based IVWSN for one-electronic-control-unit (ECU) and multiple-ECU cases. For the one-ECU case, we show that the optimal rate and power allocation is independent of the optimal scheduling algorithm. We prove the NP-hardness of the scheduling problem and formulate the optimal solution as a mixed-integer linear programming (MILP) problem. We then propose a 2-approximation algorithm, which is the smallest period into the shortest subframe first (SSF) algorithm. For the multiple-ECU case, where the concurrent transmission of links is possible, we formulate the optimal power control as a geometric-programming problem and optimal scheduling problem as an MILP problem where the number of variables is exponential in the number of links. We then propose a heuristic algorithm - the maximum-utility-based concurrency allowance algorithm - based on the idea of significantly improving the performance of the SSF algorithm in the existence of multiple ECUs by determining the sets of maximum utility.