Opportunistic cooperation for infrastructure-to-relaying-vehicles over LTE-A networks

We extend vehicular cooperation into downlink LTE-A networks in what we call Infrastructure-to-Relaying-Vehicles (I2RV) cooperation. In I2RV, vehicles are used as relaying terminals between eNodeB/BS and a receiving user equipment located or mounted on another traveling vehicle, for the aim of extending coverage, improving performance, and attaining distributed transmission. Initial works on cooperative vehicular communications build upon the assumption of flat and quasi-static fading channels, this can be justified only for narrowband systems in very slow traffic flows such as in rush-hours. In this paper, we consider highway traffic with high-speed mobility resulting in doubly-selective (i.e., time- and frequency-selective) channels. To overcome the performance degradation, we make use of precoded cooperative transmission accompanied with an opportunistic best-relay selection technique to extract the rich underlying multipath-Doppler-spatial diversity gains. Our performance analysis through pairwise error probability (PEP) derivation shows that, through proper precoding, the proposed system is able to extract maximum available diversity in time, frequency and space. Furthermore, we derive a closed-form expressions for the outage probability as a bench-mark for future analysis for the proposed scheme. Through numerical analysis, we demonstrate that significant coverage advantage by extending the transmission distance targeting a specific error rate and using the same transmitting power can be achieved.