In this paper, a new Medium Access Control (MAC) protocol combining Transmit Power Control (TPC), Rate Adaptation (RA) and Cooperative Transmission (CT) is proposed, in the context of multi-rate ad hoc networks. The protocol aims to achieve energy efficiency of data transmission while increasing the overall network throughput. The key idea of the protocol is to allow each wireless node to create a table with the optimal power-rate combinations based only on the network interface card specifications. In the presence of low data-rate nodes the network throughput is greatly degraded. To mitigate this well-known “rate anomaly” problem we use CT to replace the direct low-rate links by relayed high-rate links. By exchanging control frames and looking up the power-rate table, the wireless node chooses the most suitable transmission strategy (which consists of selecting the most optimal power-rate combination) for each data-frame as well as the transmission scheme (direct or relayed). Results reveal an important improvement in the overall network throughput as well as in the energy consumption with the new protocol compared to the scheme without TPC and without cooperation. Furthermore, simulation results show that our scheme deliver more data per unit of energy consumption than the IEEE 802.11 scheme.

In this paper, we study the performance of millimeter wave (mmWave) vehicular communications (VCs) using non-orthogonal multiple access scheme (NOMA) at road intersections, since there areas are more prone to accidents. We study the case when the intersection involves two perpendicular lanes, we then extend the study to an intersection with several lanes. The transmission occurs between a source, and two destinations. The transmission experiences interference originated from a set of vehicles that are distributed as a Poisson point process (PPP). Our analysis includes the effects of blockage from buildings and vehicles at intersections. Closed form outage probability expressions are obtained. We show that as the nodes reach the intersection, the outage probability increases. Counter-intuitively, we show that the non line of sigh (NLOS) scenario has a better performance than the line of sigh (LOS) scenario. Finally, we compare the performance of mmWave NOMA with OMA, and we show that NOMA offers a significant improvement over OMA mmWave vehicular networks. The analysis is verified by Monte-Carlo simulation.

Vehicular safety communications (VSCs) are known to provide relevant contributions to avoid congestions and prevent road accidents, and more particularly at road intersections since these areas are more prone to accidents. In this context, one of the main impairments that affect the performance of VSCs are interference. In this paper, we develop a tractable framework to model cooperative transmissions in presence of interference for VSCs at intersections. We use tools from stochastic geometry, and model interferer vehicles locations as a Poisson point process. First, we calculate the outage probability (OP) for a direct transmission when the received node can be anywhere on the plan. Then, we analyze the OP performance of a cooperative transmission scheme. The analysis takes into account two dimensions: the decoding strategy at the receiver, and the vehicles mobility. We derive the optimal relay position, from analytical and simulation results, for different traffic densities and for different vehicles mobility models. We also show that the OP does not improve after the number of infrastructure relays reached a threshold value. Finally, we show that the OP performance of VSCs is higher at intersections than on highways. We validated our analytical results by Monte-Carlo simulations.

In this paper, we study vehicular communications (VCs) at intersections, in the presence of interference over Nakagami-m fading channels. The interference are originated from vehicles located on two perpendicular roads. We derive the outage probability, and closed forms are obtained. The outage probability is derived when the destination is on the road (vehicle, cyclist, pedestrian) or outside the road (base station, road side unit). We compare the performance of line of sight (LOS) scenarios and non-line of sight (NLOS) scenarios, and show that NLOS scenarios offer better performance than LOS scenarios. We also compare intersection scenarios with highway scenarios, and show that the performance of intersection scenarios are worst than highway scenarios as the destination moves toward the intersection. Finally, we investigate the performance of VCs in a realistic scenario involving several lanes. All the analytical results are validated by Monte-Carlo simulations.

In this paper, we study the impact and the improvement of using cooperative non-orthogonal multiple access scheme (NOMA) on a millimeter wave (mmWave) vehicular network at intersection roads. The intersections consists of two perpendicular roads. The transmission occurs between a source, and two destinations nodes with a help of a relay. We assume that the interference comes from as set of vehicles that are distributed as a one dimensional homogeneous Poisson point process (PPP). We derive closed form outage probability expressions for cooperative NOMA, and compare them with cooperative orthogonal multiple access (OMA). We show that, NOMA offers a significant improvement, especially for high data rates. However, there a condition imposed to the data rate, otherwise, the performance of NOMA will decreases dramatically. We show that as the nodes approach the intersection, the outage probability increases. Counter-intuitively, We show that, the non line of sigh (NLOS) scenario has a better performance than the line of sigh (LOS) scenario. The analysis is conducted using tools from stochastic geometry and is verified with Monte Carlo simulations.