TwinTimescale Radio Resource Management for UltraReliable and LowLatency Vehicular Networks To efficiently support safetyrelated vehicular applications, the ultrareliable and lowlatency communication (URLLC) concept has become an indispensable component of vehicular networks (VNETs). Due to the high mobility of VNETs, exchanging nearinstantaneous channel state information (CSI) and making reliable resource allocation decisions based on such shortterm CSI evaluations are not practical. In this paper, we consider the downlink of a vehicletoinfrastructure (V2I) system conceived for URLLC based on idealized perfect and realistic imperfect CSI. By exploiting the benefits of the massive MIMO concept, a twostage radio resource allocation problem is formulated based on a novel twintimescale perspective for avoiding the frequent exchange of nearinstantaneous CSI. Specifically, based on the prevalent roadtraffic density, Stage 1 is constructed for minimizing the worstcase transmission latency on a longterm timescale. In Stage 2, the base station allocates the total power at a shortterm timescale according to the largescale fading CSI encountered for minimizing the maximum transmission latency across all vehicular users. Then, a primary algorithm and a secondary algorithm are conceived for our V2I URLLC system to find the optimal solution of the twintimescale resource allocation problem, with special emphasis on the complexity imposed. Finally, our simulation results show that the proposed resource allocation scheme significantly reduces the maximum transmission latency, and it is not sensitive to the fluctuation of roadtraffic density.

Joint UplinkDownlink Resource Allocation under Outage Case in Vehicular Communications Vehicular communications are widely developed through three types of network structures including vehicletoinfrastructure (V2I), infrastructuretovehicle (I2V) and vehicletovehicle (V2V). The information transmission requirements of V2I and I2V links needs high capacity and V2V links are vulnerable to the outage cases caused by high mobility of vehicles. Aim to this, we propose a Joint UplinkDownlink Resource Allocation under Outage Case (RAOC) scheme based on both traceable slowvarying large scale fading information and the fastvarying small scale fading information substituted into outage probability. Importantly, the stability of large V2V links can be guaranteed with the tolerable reduction of the sum capacity of all V2I links and I2V links, which is considered as the optimization objective. The simulation results indicate that the proposed algorithm improves the stability performance of V2V links at the little sacrifice of the sum capacity compared with another algorithm.