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The paper studies two moving vehicles exchanging messages assisted by another vehicle which is used as a relay. All the vehicle-to-vehicle (V2V) links are modeled as flat double-Rayleigh fading. Based on this particular channel model, the OPA (optimal power allocation) solutions are derived through maximizing source-to-destination channel capacity on the assumptions of amplify-and-forward relaying strategy. Then, the outage probability is discussed and the lower bound on it is acquired. Simulation results manifest that the OPA method improves the average throughput of the IVC (inter-vehicular communication) system by about 2 dB at low SNR (signal-to-noise ratio) and has no less than 2 dB gains on outage probability at medium to high SNR over equal power allocation (EPA) scheme. They also show that the lower bound on outage probability approximates to the Monte Carlo numerical calculations at low to medium SNR region and, as the exact outage probability is not easy to obtain, it can be used to estimate the outage performance of the relay-assisted IVC system roughly.

This paper studies the inter-vehicular communication (IVC) system where a vehicle transmits information to another vehicle assisted by an access point (AP), which may be mounted along a street or on a rooftop. The paper first presents the double-Rayleigh fading vehicle-to-vehicle (V2V) channel model and the amplify-and-forward (AF) relaying system. And then the optimal power allocation (OPA) solutions are derived through maximizing source-to-destination channel capacity. Based on mathematic analysis, the closed-form expression on outage probability is concluded finally. Simulation results show that the OPA scheme improves the average throughput by about 2 dB at low to high SNR (signal-to-noise ratio) and has no less than 2 dB gains on outage probability at medium to high SNR over equal power allocation (EPA) method. They also manifest that the theoretical analysis on average outage probability coincides very well with the Monte Carlo numerical calculations. The diversity order can be achieved as large as 2.7 dB in the relay-assisted IVC system when the relay approaches to the source and under EPA solution.

This paper studies the relay-assisted inter-vehicular communications (IVCs) with double Rayleigh fading vehicle-to-vehicle links. The OPA (optimal power allocation) solution is derived through maximizing source-to-destination channel capacity assuming amplify-and-forward relaying. The outage performance is discussed and the lower bound on outage probability at medium to high SNR (signal-to-noise ratio) is presented. Simulation results manifest that the ergodic capacity can be improved by about 2 dB at low SNR through OPA method over EPA (equal power allocation) solution, whereas the outage probability decreases more than 2dB at high SNR compared to EPA. They also show that the lower bound on average outage probability approximates to the exact calculation result at medium to high SNR in the relay-assisted IVC system.

The paper explores the relay-assisted IVC (inter-vehicular communication) systems with double-Rayleigh fading V2V (vehicle-to-vehicle) links for both APA (access point assisted) and VA (vehicle assisted) schemes. The OPA (optimal power allocation) solutions are derived through maximizing source-to-destination channel capacity assuming amplify-and-forward relaying. Furthermore, the outage performance is discussed and the lower bounds on outage probabilities at medium to high SNRs (signal-to-noise ratios) are presented for both APA and VA systems. Simulations manifest that the outage performance can be improved about 2dB gains through OPA method over EPA (equal power allocation) solution and the lower bounds coincide with the exact outage probabilities well at medium SNRs. These bounds can be used to evaluate the outage performance of the cooperative IVC systems roughly.