Nearest With Forward Progress Research Articles

Latency and Reliability of mmWave Multi-Hop V2V Communications Under Relay Selections

Timely and reliable information sharing among autonomous vehicles (AVs) provides a promising approach for reducing traffic congestion and improving traffic efficiency in future intelligent transportation systems. In this paper, we consider millimeter-wave (mmWave) based multi-hop vehicle-to-vehicle (V2V) communications to facilitate ultra-reliable low-latency information sharing among AVs. We propose a novel framework for performance analysis and design of relay selection schemes in mmWave multi-hop V2V communications, while taking into account the mmWave signal propagation characteristics, road topology, and traffic conditions. In particular, considering the minimum tracking distance requirement of road traffic, the headway, i.e., the distance between adjacent AVs, is modeled as shifted-exponential distribution. Moreover, we model the communication path losses using the Manhattan distance metric in the taxicab geometry, which can more accurately capture the characteristics of mmWave signal propagation in urban grid roads than conventional Euclidean distance geometry. Based on the proposed model, we investigate the latency and reliability of mmWave multi-hop V2V communications for three widely adopted relay selection schemes, i.e., random with forward progress (RFP), most forward with fixed radius (MFR), and nearest with forward progress (NFP), respectively. Furthermore, we propose a novel relay selection scheme for joint optimization of the single-hop forward progress (FP) and single-hop latency according to the AVs' instantaneous locations and an estimate of the residual multi-hop latency. Simulation results show that, by balancing the current single-hop latency and the residual multi-hop latency for the multi-hop V2V network, the proposed relay selection scheme significantly outperforms the MFR, NFP and RFP in both multi-hop transmission latency and reliability of mmWave V2V communications.

A Stochastic Geometry Model for Multi-Hop Highway Vehicular Communication

Carrier sense multiple access (CSMA) protocol is standardized for vehicular communication to ensure a distributed and efficient communication between vehicles. However, several vehicular applications require efficient multi-hop information dissemination. This paper exploits stochastic geometry to develop a tractable and accurate modeling framework to characterize the multi-hop transmissions for vehicular networks in a multilane highway setup. In particular, we study the tradeoffs between per-hop packet forward progress, per-hop transmission success probability, and spatial frequency reuse (SFR) efficiency imposed by different packet forwarding schemes, namely, most forward with fixed radius (MFR), the nearest with forward progress (NFP), and the random with forward progress (RFP). We also define a new performance metric, denoted as the aggregate packet progress (APP), which is a dimensionless quantity that captures the aforementioned tradeoffs. To this end, the developed model reveals the interplay between the spectrum sensing threshold ( $\boldsymbol{\rho}_{\boldsymbol{th}}$ ) of the CSMA protocol and the packet forwarding scheme. Our results show that, contrary to ALOHA networks, which always favor NFP, MFR may achieve the highest APP in CSMA networks if $\boldsymbol{\rho}_{\boldsymbol{th}}$ is properly chosen.

Transmission Radius Control in Wireless Ad Hoc Networks with Smart Antennas

In this paper, we present a model to analyze the performance of three transmission strategies with smart antennas, i.e. directional antennas with adjustable transmission power. Generally, a larger transmission radius contributes a greater progress if a transmission is successful. However, it has a higher probability of collision with other concurrent transmissions. Smart antennas mitigate collisions with sectorized transmission ranges. They also extend the transmission radii. By modelling three transmission strategies, namely, Nearest with Forward Progress (NFP), Most Forward with Fixed Radius (MFR), and Most Forward with Variable Radius (MVR), our analysis illustrates that the use of smart antennas can greatly reduce the possibility of conflicts. The model considers the interference range and computes the interference probability for each transmission strategy. We have analyzed two Medium Access Control (MAC) protocols using our interference model, namely, the slotted ALOHA protocol and the slotted CSMA/CA-like protocol. The result shows that, for slotted ALOHA, NFP yields the best one-hop throughput, whereas MVR provides the best average forward progress. The overall performance is substantially improved with the slotted CSMA/CA-like protocol, and the network becomes more resilient.

Analyzing routing strategy NFP in multihop packet radio networks on a line

Presents a one-dimensional model to analyze routing strategy NFP (nearest with forward progress) for a multihop packet radio network. It is assumed that each station has adjustable transmission range to address target nodes, distributed on a line according to a nonhomogeneous Poisson process. NFP transmits to the nearest neighbor in the desired direction with transmission range as small as possible, to minimize the probability of collisions. This model is appropriate e.g. for road traffic information systems. The analysis is based on a complete mathematical description, the solution of certain differential equations is one of the key points to arrive at a closed form solution. Results are presented. Graphically, it turns out that NFP has uniformly largest throughput, while progress behaves comparably to other routing strategies proposed in the literature.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effect of Rayleigh fading in a multihop mobile packet radio network with capture

We study the effect of Rayleigh fading in a multihop mobile packet radio network (PRN) with capture. Four transmission strategies based on two previously proposed routing schemes, most forward with fixed range (MFR) and nearest with forward progress (NFP), and two new routing schemes, minimal angular deviation (MAD) and angular deviation to transmission range ratio (ARR), are studied. Results show that the transmission strategy based on the ARR routing scheme is generally superior to those based on the other three routing schemes. It is found that all four transmission strategies perform worse in the presence of Rayleigh fading. This is in contrast to single-hop systems in which Rayleigh fading generally does not result in poorer performance. >