Abstract
In recent years, intelligent transport system (ITS) applications with unmanned ground vehicles (UGV) have increased dramatically to improve the safety, efficiency, and unique services in low- to medium-range communication deployment. Orthogonal frequency division multiplexing (OFDM) is adopted as a modulation scheme for this communication system to combat fading. Unfortunately, because of possible high UGV speed, the orthogonality between subcarriers in OFDM signals is prone to intercarrier interference (ICI) caused by the Doppler spread. This paper discusses ICI suppression analysis using Universal Software Radio Peripheral (USRP) N210 under several Harbor transmission scenarios. Such communication links may contain line of sight (LoS) components in transmission. The channel is thus modeled as the well-known fast time varying path loss model. Furthermore, this paper derives the signal to interference ratio (SIR) and evaluates this parameter for several types of fading and Doppler spread shapes in UGV channels. Additionally, the paper presents a practical method for calculating the spectral efficiency of OFDM systems, with an example for actual implementation in UGV systems. Eventually, the testbed results indicate that the SIR will decrease if the maximum Doppler spread expands. In the Rician channel, it can be seen that the SIR depends on the maximum Doppler speed, the angle of arrival (AoA), and even the Rician element of the LoS component.
Highlights
In recent years, applications for unmanned ground vehicles (UGVs) in transport, public safety and many other commercial sectors have attracted both academic researchers and industry [1]
In the V2I channel, the vehicle moving with velocity v causes a maximum Doppler shift fd and the effect of the line of sight (LoS) component is modeled as the first term in Eq (9)
We further introduce the energy efficiency of our considered process as where ρis the hardware circuit used for the Fourier computation
Summary
Applications for unmanned ground vehicles (UGVs) in transport, public safety and many other commercial sectors have attracted both academic researchers and industry [1]. In the studies mentioned above, there is still a lack of ICI analysis in OFDM systems for Rician fading channels with different Doppler shapes. MOTIVATIONS AND CONTRIBUTIONS The first motivation of this paper is to analyze the effect of ICI on OFDM systems over both Rayleigh and Rician fading channel with several types of fading and Doppler spread shape. Concerning the problem of implementing ICI cancellation methods on Testbed, we use real time fading channels instead of taking aforementioned Doppler spread models, which cannot be reproduced in an actual transmission environment. We analyze the effects of ICI in the OFDM systems over both Rayleigh and Rician fading channels with four Doppler spread models: two-path, at (uniform), round and classic U-shape. Orthogonality of subcarriers is destroyed, and the quality of the link decreases with the Rician factor in some cases
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