Abstract
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.
Highlights
In recent years, traffic congestion and accidents have become important global issues caused by road traffic [1]
In [31], we have proposed an adaptive channel estimation scheme that selectively uses two channel estimation schemes to improve the error performance for the entire signal-to-noise ratio (SNR) range of interest, and have investigated that the channel estimation performance can be improved by selectively using the better estimation scheme between schemes spectral temporal averaging (STA) and minimum MSE (MMSE)
802.11p link level simulator, bit error rate (BER) and packet error rate (PER) simulations have been performed on LS, STA, TRFI, MMSE, SNR-assisted MCDP (SAMCDP), and two versions of the proposed scheme, i.e., switching between STA and MMSE or between STA and TRFI
Summary
Traffic congestion and accidents have become important global issues caused by road traffic [1]. In WAVE, the physical (PHY) and medium-access control (MAC) layers are defined using the IEEE 802.11p and IEEE 802.11p/IEEE 1609.4 standards, respectively [9,10] This system has the potential to significantly increase road safety, and it is expected to solve many traffic issues. Except for the bandwidth and carrier frequency, the 802.11p PHY has the same structure as 802.11a; 802.11p uses four pilot subcarriers in each symbol portion of the packet. These pilot subcarriers are insufficient for tracking the channel variations in vehicular environments [12,13]. Robust and accurate channel estimation is necessary to obtain excellent communication performance
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