Adaptive Pilot Patterns for CA-OFDM Systems in Nonstationary Wireless Channels

TL;DR

This paper proposes an adaptive pilot pattern scheme for CA-OFDM systems that dynamically adjusts pilot spacing and power based on channel conditions, significantly improving performance in nonstationary wireless channels.

Contribution

It introduces a codebook-based adaptive pilot scheme with a heuristic algorithm for optimal pilot configuration, reducing overhead and enhancing system efficiency in nonstationary environments.

Findings

Significant performance gains with adaptive pilot patterns

Reduced pilot overhead in good channel conditions

Improved robustness in nonstationary wireless channels

Abstract

In this paper, we investigate the performance gains of adapting pilot spacing and power for Carrier Aggregation (CA)-OFDM systems in nonstationary wireless channels. In current multi-band CA-OFDM wireless networks, all component carriers use the same pilot density, which is designed for poor channel environments. This leads to unnecessary pilot overhead in good channel conditions and performance degradation in the worst channel conditions. We propose adaptation of pilot spacing and power using a codebook-based approach, where the transmitter and receiver exchange information about the fading characteristics of the channel over a short period of time, which are stored as entries in a channel profile codebook. We present a heuristic algorithm that maximizes the achievable rate by finding the optimal pilot spacing and power, from a set of candidate pilot configurations. We also analyze the computational complexity of our proposed algorithm and the feedback overhead. We describe methods to minimize the computation and feedback requirements for our algorithm in multi-band CA scenarios and present simulation results in typical terrestrial and air-to-ground/air-to-air nonstationary channels. Our results show that significant performance gains can be achieved when adopting adaptive pilot spacing and power allocation in nonstationary channels. We also discuss important practical considerations and provide guidelines to implement adaptive pilot spacing in CA-OFDM systems.