Practical Challenges in CACC Communication: ITS G5, LTE Uu, and LTE Sidelink PC5

The focus of this study is the performance evaluation of Cooperative adaptive cruise control (CACC) achieved with three different wireless technologies for vehicle-to-vehicle (V2V) communications, i.e., intelligent transport system (ITS) G5 based on 802.11p and mobile long term evolution (LTE). For communications with LTE we will consider both the regular air interface LTE Uu and the device-to-device PC5, which is based on LTE sidelink. CACC employs inter-vehicle wireless communications to safely drive at short inter-vehicle distances, which improves road throughput. The underlying technical requirement to achieve this benefit is formulated by the notion of string stability, requiring the attenuation of the effects of disturbances in upstream direction. This work analyzes the relation between the communication performance and the string stable performance of a CACC string. Field experiments were carried out in Lelystad, The Netherlands, with two CACC-equipped vehicles. Results show that the latency of ITS G5 network is smaller than LTE Uu and PC5. However, since the majority latency of LTE Uu and PC5 is limited by the string stability requirement in the current test setting, string stability can still be guaranteed. The packet error with LTE PC5 and ITS G5 is observed. However, the packet error rate is small that does not significantly affect the CACC application performance.