Rate Adaptation in Predictor Antenna Systems

Abstract

Predictor antenna (PA) system is referred to as a system with two sets of antennas on the roof of a vehicle, where the PAs positioned in the front of the vehicle are used to predict the channel state observed by the receive antennas (RAs) that are aligned behind the PAs. This letter studies the performance of PA systems in the presence of the mismatching problem, i.e., when the channel observed by the PA is not exactly the same as the channel experienced by the RA. Particularly, we study the effect of spatial mismatching on the accuracy of channel state information estimation and rate adaption. We derive closed-form expressions for instantaneous throughput, outage probability, and the throughput-optimized rate adaptation. Also, we take the temporal evolution of the channel into account and evaluate the system performance in temporally-correlated conditions. The simulation and analytical results show that, while PA-assisted adaptive rate adaptation leads to considerable performance improvement, the throughput and the outage probability are remarkably affected by the spatial mismatch and temporal correlations.

A Semi-Linear Approximation of the First-Order Marcum Q-Function With Application to Predictor Antenna Systems

“…Our paper is different from the state-of-the-art literature because the proposed semi-linear approximation of the firstorder Marcum Q-function and the derived closed-form expressions for the considered integrals, i.e., Theorems 1-4 and Corollaries 1-2, have not been presented by, e.g., [1], [3]- [7], [9]- [51]. Also, as opposed to [43]- [50], we perform analytical performance evaluation of PA systems with CSIT (T: at the transmitter)-based rate optimization to mitigate the effect of the spatial mismatch.…”

“…Moreover, the European project deliverables, e.g., [57,Chapter 2], [58, P. 107] and [59,Chapter 3], have well addressed the feasibility of the PA concept in network-level design. Finally, different works have analyzed the PA system in both frequency division duplex (FDD) [45], [46], [48] and time division duplex (TDD) [44], [49] systems, with some developments on addressing the system challenges such as antenna coupling [47], [50], spatial mismatch [50], [51], and spectrum underutilization [52], [53].…”

“…If the RA does not arrive in the same position as the PA, the actual channel for the RA would not be identical to the one experienced by the PA before. Such inaccurate channel state information (CSI) estimation will affect the system performance considerably at moderate/high speeds [44], [51]. One way to compensate for this mismatch problem is by interpolating channel samples at the base station (BS) [44], [45], [49].…”

Power Allocation in HARQ-Based Predictor Antenna Systems

“…We represent the probability density function (PDF) and cumulative density function (CDF) of a random variable A by f A (•) and F A (•), respectively. Due to spatial mismatch between the PA and the RA, assuming a semi-static propagation environment, i.e., assuming that the coherence time of the propagation environment is much larger than δ 1 , h 2 and h 1 are correlated according to [5,Eq. 5]…”

“…Let us initially concentrate on the RTD protocol. Then, combining (5) and (8), the expected total transmission power is given byP…”