On Coexistence of Vehicular Overlay Network and H2H Terminals on PRACH in LTE

[Abstract] Vehicular ad hoc networks (VANETs) that use the IEEE 802.11p communication standard face a number of challenges, not least when it comes to safety messages on the VANET control channel (CCH) where short delay times and reliable delivery are of primary importance. In this paper we propose a vehicular machine⁃to⁃machine (VM2M) overlay network that uses Long Term Evolution (LTE) physical random access channel (PRACH) to emulate VANET CCH. The overlay network uses dedicated preambles to separate vehicular traffic from regular LTE traffic and a carrier sense multiple access with collision avoidance (CSMA⁃CA) layer similar to the one used in IEEE 802.15.4 to avoid the four step handshake and the overhead it incurs. The performance of the proposed overlay is evaluated under a wide range of PRACH parameters which conform to the scenarios with high vehicle velocities and large distances between roadside units (RSUs) that may be encountered in rural areas and on highways.

[Keywords] vehicular ad hoc networks (VANETs); VANET control channel (CCH); 3GPP long term evolution (LTE); physical random access channel (PRACH); IEEE 802.15.4; human⁃to⁃human (H2H) traffic