A Vehicle-Approach Alert System Based on the Neighbor Discovery Protocol for Pedestrian Safety

An RSSI-Based Low-Power Vehicle-Approach Detection Technique to Alert a Pedestrian

“…The final goal of this study is to suitably design system parameters ∆T, τ, N and α 0 to accommodate typical values of d 1 and v. This section shows numerical results on several scenarios of d 1 and v. Figure 5 shows the relationship between the detection error rate and the detection delay T delay for both passive and ND-based methods with any combinations of system parameters ∆T = 0.2, 0.5 and 1 s and α 0 = 0.5, 0.25 and 0.1. Each figure includes the results for the vehicle velocities v = 40, 20 and −40 km/h with d 1 = 100 m. These parameters stem from the legal speeds for vehicles in residential areas and the communication range of beacons [18]. The parameters related to the propagation model are set as κ = 1 × 10 −3 and λ = 2.35, and the response lag τ in the ND-based method is set as τ = 0.1 s. The simulation values are obtained by a Monte Carlo method, in which RSSI samples are generated randomly according to the PDF (5).…”

“…Although the global positioning system (GPS) would be helpful to implement the functions mentioned above, the devices would be more costly, and the obtained precision would get low under building shadow. Moreover, the system employing a GPS tend to consume battery energy more quickly; the current consumption by a typical GPS module is about 14.4 mA, and thus the battery life of the device becomes only about 15 h if we employ a coin battery with the capacity of 220 mAh [18]. RSSI-based detection with the proposed ND-based method overcomes the issue of battery exhaustion, which will be described in Section 7.…”

“…where the denominator N − 2 stems from the reduction of degrees of freedom due to the conditions in (18). By replacing σ 2 in (17) with s 2 , we can obtain the sample variance ofβ 2 , and thus the sample standard deviation can also be calculated as…”

“…The ND-based method also has the advantage of prolonging the battery life of the pedestrian's device compared to the passive method. According to [18], instantaneous current consumption per beacon transmission is about 94.4×10 −3 mAsec while the reception process continuously consumes 5.4 mA, which is more dominant than that of the transmission process if the reception process lasts long. In the ND-based method, the device can open the receiver window only while it waits for an alert beacon such that we can limit the duration time of the reception process.…”

“…As a consequence, the battery life of the ND-based method is seven times longer than that of the passive method. A more detailed analysis of the power consumption can be seen in [18]. Although the ND-based method has a secondary advantage that we can also alert the driver side about the approaching pedestrian, this topic is beyond the scope of this paper.…”