A Measurement Study of Time-Scaled 802.11a Waveforms Over The Mobile-to-Mobile Vehicular Channel at 5.9 GHz
ABSTRACT We have studied the effects of the mobile vehicle-to-vehicle (V2V) channel on scaled versions of the current IEEE 802.11 a standard to investigate how readily they can be applied to vehicular networks. In particular, measured parameters for the V2V channel at 5.9 GHz in suburban, highway, and rural environments are studied in the context of critical parameters for OFDM. Actual performance of scaled OFDM waveforms with bandwidths of 20 MHz (bandwidth of IEEE 802.11 a), 10 MHz (bandwidth of the draft IEEE 802.11 p), and 5 MHz (halved bandwidth of IEEE 802.11 p) are described and interpreted in light of the channel parameters. At 20 MHz the guard interval is not long enough, while at 5 MHz errors increase from lack of channel stationarity over the packet duration. For these choices of the scaled 802.11 a OFDM waveform, 10 MHz appears to be the best choice.
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ABSTRACT: This paper presents an analytical performance analysis of a car-to-car visible light communications system under different communication geometries during the daytime. A market-weighted headlamp beam-pattern model, measured dirt effects on light distribution, and the road-surface reflection model are employed. We consider both the line-of-sight and non-line-of-sight links and outline the relationship between the communication range and the system bit error rate (BER) performance. Results show that the wet road surface can help to increase the received optical power and improve the BER performance above a certain distance, and the communications coverage range can reach up to 70 m at a data rate of 50 Mbps when a photodetector is mounted on the car at a height of 0–0.2 m above the road surface.Applied Optics 03/2015; 54(7-7):1696-1706. DOI:10.1364/AO.54.001696 · 1.69 Impact Factor
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ABSTRACT: The article reports vehicular channel measurements in the frequency band of 5.8 GHz for IEEE 802.11p standard. Experiments for both intra-vehicle and out-of-vehicle environments were carried out. It was observed that the large-scale variations (LSVs) of the power delay profiles (PDPs) can be best described through a two-term exponential decay model, in contrast to the linear models which are suitable for popular ultra-wideband (UWB) systems operating in the 3- to 11-GHz band. The small-scale variations (SSVs) are separated from the PDP by subtracting the LSV and characterized utilizing logistic, generalized extreme value (GEV), and normal distributions. Two sample KolmogorovSmirnov (K-S) tests validated that the logistic distribution is optimal for in-car, whereas the GEV distribution serves better for out-of-car measurements. For each measurement, the LSV trend was used to construct the respective channel impulse response (CIR), i.e., tap gains at different delays. Next, the CIR information is fed to an 802.11p simulation testbed to evaluate the bit error rate (BER) performance, following a Rician model. The BER results strongly vouch for the suitability of the protocol for in-car as well as out-of-car wireless applications in stationary environments.EURASIP Journal on Wireless Communications and Networking 12/2015; 2015(1). DOI:10.1186/s13638-015-0273-x · 0.81 Impact Factor
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ABSTRACT: In this paper, we study the performance of hybrid automatic repeat request (HARQ) with incremental redundancy over double Rayleigh channels, a common model for the fading amplitude of vehicle-to-vehicle communication systems. We investigate the performance of HARQ from an information theoretic perspective. Analytical expressions are derived for the e-outage capacity, the average number of transmissions, and the average transmission rate of HARQ with incremental redundancy assuming a maximum number of HARQ rounds. Moreover, we evaluate the delay experienced by Poisson arriving packets for HARQ with incremental redundancy. We provide analytical expressions for the expected waiting time, the packet's sojourn time in the queue, the average consumed power, and the energy efficiency. In our study, the communication rate per HARQ round is adjusted to the average signal-to-noise ratio (SNR) such that a target outage probability is not exceeded. This setting conforms with communication systems in which a quality of service is expected regardless of the channel conditions. Our analysis underscores the importance of HARQ in improving the spectral efficiency and reliability of communication systems. We demonstrate as well that the explored HARQ scheme achieves full diversity. Additionally, we investigate the tradeoff between energy efficiency and spectral efficiency.IEEE Transactions on Wireless Communications 11/2014; 13(11). DOI:10.1109/TWC.2014.2348561 · 2.76 Impact Factor