Performance Analysis of MIMO-HARQ Assisted V2V Communications With Keyhole Effect

Abstract

Vehicle-to-vehicle (V2V) communications under dense urban environments usually experience severe keyhole fading effect especially for multi-input multi-output (MIMO) channels, which degrades the capacity and outage performance due to the rank deficiency. To avoid these, the integration of MIMO and hybrid automatic repeat request (HARQ) is proposed to assist V2V communications in this paper.By using the methods of integral transforms, the outage probabilities are derived in closed-form for different HARQ-assisted schemes, including Type I-HARQ, HARQ with chase combining (HARQ-CC), and HARQ with incremental redundancy (HARQ-IR). With the results, meaningful insights are gained by conducting the asymptotic outage analysis. Specifically, it is revealed that full time diversity order can be achieved, while full spatial diversity order is unreachable as compared to MIMO-HARQ systems without keyhole effect. Moreover, we prove that the asymptotic outage probability is a monotonically increasing and convex function of the transmission rate. More importantly, although HARQ-IR performs better than HARQ-CC owing to its higher coding complexity, this advantage becomes negligible in the large-scale array regime. Finally, the numerical results are verified by Monte-Carlo simulations along with some in-depth discussions.

Post-Cancellation-Based LLR Refining for MIMO Multiple ARQ Systems

“…When HARQ is employed to multiple-input multiple-output (MIMO) systems, various applications are possible by using the natures of HARQ retransmissions and MIMO transmission/reception. Thus, many studies have been conducted on MIMO systems with HARQ in recent years [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], e.g., the transmission efficiently analysis [16], utilization of the acknowledgment/non-acknowledgment (ACK/NACK) feedback bundling [17], modulation design considering a MIMO-coordinated multi-point scenario [18], optimization of the energy efficiency for a point-to-point massive MIMO system [19], adaptive modulation and coding design [20], integration for vehicle-to-vehicle communications [21], etc.…”

Alamouti Space-Time Coding for Vehicular Communications in the Presence of Channel Estimation Errors

“…The main challenge is the severe fading channel effects limiting the channel capacity. The channel effects become much more challenging in V2X systems as the receivers and transmitters are almost always in motion [10][11]. In addition, the presence of tall buildings and structures in urban areas or natural elevations and tall trees in rural areas cause shading effects.…”