Choi Joo-Young, Jo Han-Shin, Mun Cheol, Yook Jong-Gwan
Department of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Korea.
Department of Electronics and Control Engineering, Hanbat National University, Daejeon 34158, Korea.
Sensors (Basel). 2019 Jul 5;19(13):2971. doi: 10.3390/s19132971.
Recently, research into autonomous driving and traffic safety has been drawing a great deal of attention. To realize autonomous driving and solve traffic safety problems, wireless access in vehicular environments (WAVE) technology has been developed, and IEEE 802.11p defines the physical (PHY) layer and medium access control (MAC) layer in the WAVE standard. However, the IEEE 802.11p frame structure, which has low pilot density, makes it difficult to predict the properties of wireless channels in a vehicular environment with high vehicle speeds; thus, the performance of the system is degraded in realistic vehicular environments. The motivation for this paper is to improve the channel estimation and tracking performance without changing the IEEE 802.11p frame structure. Therefore, we propose a channel estimation technique that can perform well over the entire SNR range of values by changing the method of channel estimation accordingly. The proposed scheme selectively uses two channel estimation schemes, each with outstanding performance for either high-SNR or low-SNR signals. To implement this, an adaptation algorithm based on a preamble is proposed. The preamble is a signal known to the transmitter-receiver, so that the receiver can obtain channel estimates without demapping errors, evaluating performance of the channel estimation schemes. Simulation results comparing the proposed method to other schemes demonstrate that the proposed scheme can selectively switch between the two schemes to improve overall performance.
近年来，自动驾驶与交通安全方面的研究备受关注。为实现自动驾驶并解决交通安全问题，车载环境无线接入（WAVE）技术得以发展，且IEEE 802.11p定义了WAVE标准中的物理（PHY）层和介质访问控制（MAC）层。然而，IEEE 802.11p帧结构的导频密度较低，使得在车辆高速行驶的车载环境中难以预测无线信道的特性；因此，在实际车载环境中系统性能会下降。本文的目的是在不改变IEEE 802.11p帧结构的情况下提高信道估计和跟踪性能。为此，我们提出一种信道估计技术，通过相应地改变信道估计方法，使其在整个信噪比范围内都能有良好表现。所提方案选择性地使用两种信道估计方案，每种方案对高信噪比或低信噪比信号都有出色性能。为实现这一点，提出了一种基于前导码的自适应算法。前导码是收发器已知的信号，这样接收器就能在不产生解映射错误的情况下获得信道估计，评估信道估计方案的性能。将所提方法与其他方案进行比较的仿真结果表明，所提方案能够在两种方案之间进行选择性切换以提高整体性能。
