Random Transmit Power Control for DSRC and its Application to Cooperative Safety

Abstract

Cooperative safety applications require Dedicated Short-Range Communications (DSRC) to provide position-awareness of neighboring vehicles at a specific level of reliability, i.e. awareness-quality, up to a given distance, i.e. awareness-range. However, heavy communication loads negatively impact such awareness requirements due to communication impairments, ranging from strict capacity limitations of DSRC channels to correlated packet collisions due to periodic communication patterns. Transmission control strategies may adapt power or rate to control such impairments but risk missing the requirements of cooperative safety applications. In this paper, we design a new awareness control strategy by implementing a spatial awareness framework. Specifically, we adapt the distribution of the awareness-quality as a function of the awareness-range. Therefore, we first propose Random Transmit Power Control (RTPC), which manages to provide different levels of awareness-quality at different ranges, while mitigating correlated packet collisions by randomizing them in space. As RTPC is able to reduce the channel load, we secondly propose to combine RTPC with Transmit Rate Control (TRC) and to benefit from the gained channel resources by subsequently increasing the update-rate and by implication, the quality of position-awareness. The spatial awareness control capability of RTPC+TRC has been evaluated through simulations. We discuss the influence of RTPC+TRC on cooperative safety applications exemplarily for the Forward Collision Warning (FCW) application.

Congestion Control in V2V Safety Communication: Problem, Analysis, Approaches

“…It is a measure for the channel load perceived by a vehicle, and depends on the number of vehicles in its transmission range and their individual message generation rates. Many congestion control algorithms, such as periodically updated load sensitive adaptive rate control (PULSAR) [15], random transmit power control (RTPC) [30], distributed fair transmit power adjustment (D-FPAV) [25], distributed network utility maximization (D-NUM) [31], packet-count based decentralized data-rate congestion control algorithm (PDR-DCC) [32] use CBR/CBT as one of the metrics to analyze the communication benefit of the algorithms. CBR has been shown to be a suitable metric to increase packet delivery performance [33].…”

“…Packet error rate is used in [38]. Packet collision rate, which is defined as the number of packet collisions normalized in time and space, is used in [30]. Reception probability is used in [21,25].…”

“…Both PLR and IPD are important metrics for VANET, as they both give a measure of the level of awareness of surrounding vehicles. As such, both metrics have been widely used in performance evaluation of V2V communication protocols [21,25,30,[37][38][39][40]. Although both PLR and IPD provide information on vehicular awareness, they give different perspectives on awareness.…”

“…In [27] the probability of successful reception of beacon message is used with respect to the distance to assess the algorithm's effectiveness and the average channel access time (CAT) for claiming fairness. Update delay is defined in [30] as the elapsed time between two consecutive CAMs/BSMs successfully received from the same transmitter, which aims to assess the awareness of vehicle from a communication perspective. In [26] a 95% Euclidean cut-off error (in meters) is defined and a 95% Tracking Error in [23] is used to represent the tracking accuracy of the communication policy, which possesses a statistical sense similar to a confidence interval (CI).…”

Contention Intensity Based Distributed Coordination for V2V Safety Message Broadcast

“…In the V2V communications for CV applications, a particularly, if not the most, important component is the broadcast of safety messages. Such broadcast corresponds to the Basic Safety Message (BSM) in the SAE J2735 standard in the US or the Cooperative Awareness Message (CAM) in the ITS standard of European Telecommunications Standards Institute [4]. The safety messages are single-hop, periodical (i.e., time-driven as opposed to event-driven), and carry safety-related status information of vehicles such as their speed, acceleration, position, and direction.…”