Vehicle safety communications project final report

According to [ 21 , 22 ], there may be increased collision numbers as well as a reduction in the successful delivery of data packets if more nodes in a network attempt to send data simultaneously to their shared medium. Because of this, we need to choose the number of OBUs i. When a collision occurs, we discard the received message. In this paper, we consider an approximate packet collision probability model as proposed in [ 21 ]. The motivation of using this model was the availability of a closed-form expression for the collision probability, which allowed us to develop a tractable optimization scenario.

However, this collision model is applicable to a saturation scenario i. Thus, the model is independent of the message rate.

It is well known that multiple data items can be broadcast in a broadcast tick in encoded form using network coding, which results in a boost in the throughput. However, instead of performing networking coding between a pair of randomly selected vehicles, we propose the following selection and broadcasting procedure. Without loss of generality, we consider an intersection of two streets, such as the intersection shown in Figure 1 , which is symmetrical in four directions.

For a given street, first the RSU sorts the vehicles in that street according to their distances from the intersection center.

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Then the RSU broadcasts a network-coded message by performing X-OR between the messages of two vehicles of different streets provided that those vehicles are the furthest vehicles in their corresponding streets. After this, the RSU broadcasts a network-coded message of the two second-furthest vehicles of different streets, and so on. To show the delivery ratio, we consider the following notation:.

For example, x 1 is the index of the furthest vehicle in street 1, and y 2 is the index of the second-furthest vehicle in street 2. For the proposed network-coded relaying scheme, the delivery ratio of the entire system is given in the previous page see Equation The second line inside the curly bracket is associated to the proposed network-coded broadcasting performed by the RSU. A simulation was performed in MATLAB to verify the effectiveness of the proposed relaying algorithm at an intersection.

We assumed there were N vehicles at an intersection of two streets each with six lanes. This intersection was symmetrical in four directions, as shown in Figure 1. The other parameters are listed in Table 1. We performed the simulation while distributing the vehicles around the intersection randomly. The delivery-ratio performance was then calculated on the basis of the distance from the transmitter and the receiver to the intersection center. The whole process was iterated over times, and then the average delivery ratio was calculated.

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This paper considers the safety application mode. The path-loss model in [ 8 ] has been validated from real-world measurements. Both the experiments and the path-loss model were used to draw the heat map. In the experiments, we measured the packet error performance of the OBU, which is the packet error rate versus the received power.

The combination of the above factors was used to predict the PDR for any location in the heat map.

In the area close to the center, the delivery ratio was close to 1. In this case, the relaying for vehicles in a NLOS environment is necessary. The performances of the proposed schemes are shown in Figure 4 in terms of the delivery ratio versus the number of transmissions from the RSU. In the simulation, collision-free communication was assumed. A significant improvement about As expected, when the number of transmissions from the RSU increased, the delivery ratio increased and reached the maximum of 1.


In Figure 4 , we also show the delivery ratio when the RSU performed transmissions of messages of randomly selected vehicles. From the performance comparison, we observe that our proposed schemes completely outperformed the randomly selected schemes. Another example of the performances for a system with 60 vehicles is illustrated in Figure 5. Figure 6 shows the probability of collision in the V2X communication network when the number of transmissions from the RSU increased.

The results for the probability of collision for contention window sizes of 32, 64, and are presented. We note that in the IEEE When the contention window size is small, the waiting time for each OBU node before attempting to transmit is short, and the probability of collision in the network is high. When the contention window size increases, the waiting time is longer, and correspondingly, the probability of collision decreases.

Vehicle safety communications project: final report

However, if the waiting time is too long, the safety message may expire, because the transmission rate is 10 Hz and the transmission time is only ms. The probability of collision for a system with 60 vehicles is illustrated in Figure 7. The characteristics of the cost functions obtained from Equations 11 and 13 are shown in Figure 8 , where the performances are shown in the presence of collisions with different K , W.

For both proposed schemes, the cost function increased as the number of transmissions from the RSU increased. After it reached the peak value, it started to decrease as K kept increasing. This was because the benefit of relaying was more than compensated for by the penalty of additional collisions caused by retransmission.

For different W , the optimal number of relayed messages achieved by the search algorithm is depicted in the figures. In this paper, we analyze the performance of safety-message delivery between vehicles at intersections under LOS or NLOS communication scenarios.

For both scenarios, we present experimental results on the drop rate of safety messages, for which the experiments were conducted using a commercial DSRC transceiver. In order to improve the transmission reliability in the NLOS communication scenario, we propose two relaying schemes simple relaying and network-coded relaying using a RSU at the intersection as a relay node to retransmit some safety messages.

Vehicle Safety Communications - Vehicle Safety Communications - Wiley Online Library

Also, C-V2X provides a migration path to 5G based systems and services, which implies incompatibility and higher costs compared to 4G based solutions. In this case, the communication with the base station is not required. In system architectural level, proximity service ProSe is the feature that specifies the architecture of the direct communication between UEs. The motivation of the mission-critical communication was to allow law enforcement agencies or emergency rescue to use the LTE communication even when the infrastructure is not available, such as natural disaster scenario.

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In release 14 onwards, the use of PC5 interface has been expanded to meet various market needs, such as communication involving wearable devices such as smartwatch. The Cellular V2X mode 4 communication relies on a distributed resource allocation scheme, namely sensing-based semipersistent scheduling which schedules radio resources in a stand-alone fashion in each user equipment UE [9].

In addition to the direct communication over PC5, C-V2X also allows the C-V2X device to use the cellular network connection in the traditional manner over Uu interface. Uu refers to the logical interface between the UE and the base station. This is generally referred to as vehicle-to-network V2N. V2N is a unique use case to C-V2X and does not exist in Through its instant communication V2X allows road safety applications such as non-exhaustive list :.

In the medium term V2X is perceived as a key enabler for autonomous driving, assuming it would be allowed to intervene into the actual driving. In that case vehicles would be able to join platoons, the way HGVs do. The ASTM E series of standards looks at wireless communication for high-speed information exchange between vehicles themselves as well as road infrastructure.

The first standard of this series was published Their initial standard for wireless communication for vehicles is known as IEEE Later on in IEEE Around when IEEE All these standards are based on IEEE It is based on LTE as the underlying technology. Specifications were published in Specifications are published in as Release 15 comes to completion.

WISAFECAR - Vehicle to Vehicle Communication

Either case, C-V2X is the generic terminology that refers to the V2X technology using the cellular technology irrespective of the specific generation of technology. The work is currently in progress. In this way, C-V2X is inherently future-proof by supporting migration path to 5G. Cellular-based V2X solution also leads to the possibility of further protecting other types of road users e. Vehicle-to-person V2P includes Vulnerable Road User VRU scenarios to detect pedestrians and cyclists to avoid accident and injuries involving those road users.

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