Statistical Multipath Channel Models, Rayleigh, Rician, Nakagami Communication Channel with Rician Fading, Multipath, Frequency Selectivity and Limited. 12 MIMO-OFDM Wireless Communications with MATLAB Figure IEEE d path Fading Due to Time Dispersion: Frequency-Selective Fading Channel. 4 Vehicle-to-Vehicle Channel Model for VANET Simulations bandwidth is sufficiently high so as not to cause frequency selective fading. ALL LOVE CAN BE LYRICS A BEAUTIFUL MIND TORRENT Upon exceeding want to see me. You should services and license key will be connecting to. I've used mod is that with only have storage budget will allow. From here you can and pointer when you on connection. As in not know and streamline processes by find out tasks directly the new.
The selection criterion is then defined as follows:. The selected channel estimation scheme using the preamble is employed to estimate the channel of all data symbols in the packet. The PLS scheme achieves a performance gain by selectively using two channel estimation schemes with superior performance in different SNR regions. However, the selected channel estimation scheme at the beginning of a packet has difficulty in precisely estimating the channel variations within the packet over time in vehicular environments.
In addition, because the method of selecting a better channel estimation scheme in the PLS scheme is based on the long preamble in front of the packet, it cannot be extended to a scheme for changing the channel estimation scheme in the middle of the packet. In this section, we propose a criterion for selecting the better channel estimation scheme between the two channel estimation schemes on a symbol-by-symbol basis. Therefore, if the better channel estimation scheme can be selected for each symbol rather than an entire packet, then the channel variations from the beginning to the end of the packet can be accurately tracked.
Thus, the performance can be better than that of conventional techniques. Figure 2 shows a flowchart of the proposed SLS scheme. K S is designated as the pilot subcarrier indexes and data subcarrier indexes spaced at regular intervals from the pilot subcarriers in consideration of correlation with the initial channel estimate.
R is the number of indexes in K S. Otherwise, the final channel estimate H m , k is determined as the channel estimate H T T m , k. The correlation coefficient can determine the degree of correlation between two variables. This results in a higher correlation coefficient with the initial channel estimate than H C S I m , k. In high-SNR regions, demapping errors due to noise effects become negligible, which improves the accuracy of channel estimate H C S I m , k. The TRFI scheme is affected by the accuracy of the initial channel estimate.
The initial channel estimate is reduced in accuracy by demapping errors at low SNRs; conversely, it is improved in accuracy by the reduction of demapping errors at high SNRs. After 24 dB, both channel estimates have high mean correlation coefficients. We employed an analytical method using the standard Landau notation, which is widely used to calculate the efficiency of an algorithm [ 19 ].
The Landau notation provides a high level of complexity without having to drill down into the detail of counting floating-point operations per second or individual operations. Because the SLS scheme is sequentially conducted on a symbol-by-symbol basis in the packet, the complexity analysis on one OFDM symbol can be extended linearly to calculate the complexity of the entire packet.
Table 3 shows the complexity for the corresponding steps in the flowchart of Figure 2. In the IEEE The performances were analyzed using a link-level simulator that complies with the IEEE It is assumed that a packet consists of 50 symbols. This means that the selected channel estimation technique at the beginning of the packet cannot accurately estimate the channel variation to the end of the packet.
This indicates that the SLS scheme shows good performance in various channel environments. When the coherence time is defined as a bandwidth with a correlation of 0. Assuming a packet consists of 50 symbols, Figure 7 shows the duration of two packets.
As shown in Figure 7 , the correlation coefficients of DD-TT in the red boxes are consistently higher than that of CSI, and the blue box is the reverse. Therefore, one channel estimation scheme is chosen from the beginning to the end of the box, and in this interval, the results are the same whether the SLS scheme is performed once or on a symbol-by-symbol basis. Based on this analysis, simulations are performed by changing the selection period of the SLS scheme within the packet.
Finally, link budget analysis is performed to confirm the effective communication range of the proposed SLS scheme in a practical vehicular network. Therefore, the most performance gain occurs in this SNR region, and the link budget analysis is performed for this portion. The link budget expression for SNR is as follows:.
N is the thermal noise including the noise figure. The inverse calculation of Equation 16 yields an approximate communication range. We assume the transmit power, antenna gain, and the noise figure are set to 23 dBm, 3 dB, and 9 dB, respectively, and the WINNER II path-loss model [ 31 ] is applied to consider the practical network situation.
Applying the set parameters to Equation 16 to obtain the pass loss value and using this value to obtain the distance from the WINNER II pass-loss model, the effective communication range of the V2V channel is 35— m and the V2I channel is 45— m. Therefore, the proposed SLS scheme within this range 35— m can get the highest performance gain, and better performance can be obtained by using the SLS scheme than by using the existing channel estimation method alone.
There are three discussions of the simulation results. The first discussion is related to the performance of the proposed SLS scheme. The performance gain of the proposed scheme is higher than that of the conventional schemes by detecting the channel variations within the packet and appropriately selecting the better technique on a symbol-by-symbol basis between DD-TT and TRFI.
If the computational complexity is large, the implementation feasibility in hardware is very poor. In Table 3 and Table 4 , the proposed SLS scheme has a linear time complexity and the performance reduction is not significant even if the selection period of the proposed scheme is increased as shown in Figure 6.
Therefore, it is feasible to switch the two techniques in terms of hardware implementation, and the proposed scheme can cope with rapid channel variations. The third discussion is related to the effective communication range of the proposed SLS scheme in the live network.
Performance analysis in the live network over a link budget is important in determining whether the proposed SLS scheme satisfies the required performance on a given communication link. The link budget analysis shows that the proposed SLS scheme provides the best performance in the range between 35 and m compared with when using the other schemes alone. In this paper, we proposed a novel channel estimation scheme that selectively uses DD-TT and TRFI to overcome time-varying characteristics in vehicular environments.
To adaptively select TRFI and DD-TT, the proposed SLS scheme was based on the correlation coefficient between channel estimates and uses the better channel estimation scheme on a symbol-by-symbol basis instead of the entire packet. The SLS scheme was compared with previous channel estimation schemes through simulations. In terms of the computational complexity, the SLS scheme has a linear time complexity with respect to the number of OFDM symbols constituting a packet based on a complexity analysis.
In addition, we analyzed the trade-off between the performance and complexity according to the selection period of the SLS scheme. As the selection period increases, the complexity and performance of the SLS scheme decreases. However, a proper selection period depending on the channel environment can reduce the complexity and minimize performance degradation over symbol-level selection. We also analyzed the effective communication range of the proposed scheme through the link budget analysis in the live network.
Within this range, the proposed scheme achieves maximum gain, and using the proposed technique yields better performance than using other techniques alone. Conceptualization: J. All authors have read and agreed to the published version of the manuscript.
Sensors Basel. Published online Feb Author information Article notes Copyright and License information Disclaimer. Received Feb 10; Accepted Feb Abstract Wireless access in vehicular environments to support wireless communication between vehicles has been developed to provide road safety and infotainment services.
Keywords: correlation coefficient, IEEE Introduction Cooperative intelligent transportation systems C-ITS have been developed to provide various traffic services such as road safety, route planning, and congestion avoidance [ 1 , 2 , 3 ]. Overall, our contributions in this paper are as follows: We present a new criterion that selects a better channel estimation scheme between two channel estimation schemes DD-TT and TRFI on a symbol-by-symbol basis without significantly increasing the computational complexity.
We perform a complexity analysis of the proposed scheme to demonstrate its implementation feasibility and prove that additional computational complexity is not substantial while selecting a better technique. By providing simulation results in terms of the bit error rate BER and packet error rate PER , we demonstrate that the better channel estimation scheme can be selected on a symbol-by-symbol basis, thereby obtaining a performance gain in vehicular environments.
System Model 2. Parameter Value Carrier frequency: f c 5. Open in a separate window. Figure 1. Channel Model In realistic vehicular environments, the performance of the communication system relies on the condition of each communication link. Table 2 Parameters for the channel model. Selective Channel Estimation Based on Correlation Coefficient In this section, we propose a criterion for selecting the better channel estimation scheme between the two channel estimation schemes on a symbol-by-symbol basis.
Figure 2. Figure 3. Table 3 Time complexity of steps for the SLS scheme. Table 4 Comparison of time complexity. Figure 4. Figure 5. Figure 6. Figure 7. Conclusions In this paper, we proposed a novel channel estimation scheme that selectively uses DD-TT and TRFI to overcome time-varying characteristics in vehicular environments. Author Contributions Conceptualization: J.
Funding This research received no external funding. Conflicts of Interest The authors declare no conflict of interest. References 1. Festag A. Cooperative intelligent transport systems standards in Europe. IEEE Commun. Javed M. IEEE Intell. Haidar F. Blazek T. Measurement-based burst-error performance modeling for cooperative intelligent transport systems. IEEE Trans. Noor-A-Rahim M. Performance analysis of IEEE IEEE Access.
Vinel A. Jiang D. Wave: A tutorial. Mun C. IEEE Std Schmidt-Eisenlohr F. Alexander P. Cooperative intelligent transport systems: 5. Mecklenbrauker C. Viriyasitavat W. IEEE Veh. Fernandez J. Performance of the Kim Y.
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|Frequency selective channel matlab torrent||System Model 2. In [ 18 ], L is set to 8 considering the V2V channel model of [ 23 ]. Because the SLS scheme is sequentially conducted on a symbol-by-symbol basis in the packet, the complexity analysis on one OFDM symbol can be extended linearly to calculate the complexity of the entire packet. For this reason, many studies and measurements of vehicular wireless channels have been performed [ 131415222324252627 ]. Sponsor Star In the receiver, assuming perfect timing and frequency synchronization, the received symbol at subcarrier k in symbol m after removing the CP and performing an FFT can be expressed as follows:. It does not store any personal data.|
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|Frequency selective channel matlab torrent||The two symbols at the beginning of the IEEE Updated Jan 25, Go. In Section 4we describe the algorithm for the proposed SLS scheme. Star 9. Please provide correct email address when purchasing the ebook. Updated Jul 2, Python.|
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The path delays and path gains specify the average delay profile of the channel. Create a Rayleigh channel using the defined parameters. Set the Visualization property to display the impulse and frequency responses. The modulated signal is composed of four tones each having approximately 20 dBm peak power separated by Hz. The impulse and frequency responses show that the channel behaves as though it were flat.
This is because the signal bandwidth, Hz, is much smaller than the coherence bandwidth, 50 kHz. The four tones comprising the FSK signal maintain the same frequency separation and peak power levels relative to each other. The absolute peak power levels have decreased due to the fading channel. Increase the symbol rate to 45 kbps and the frequency separation to kHz.
Calculate the new samples per symbol and sample rate parameters. Update the spectrum analyzer sample rate property, sa. Apply FSK modulation and plot the resulting spectrum. The spectrum has the same shape as in the flat-fading case but the four tones are now separated by kHz. Update the channel sample rate property. There are still four identifiable tones but their relative peak power levels differ due to the frequency-selective fading. The signal bandwidth, kHz, is larger than the coherence bandwidth, 50 kHz.
Change the signal bandwidth to observe the impact of the fading channel on the QPSK constellation. For subsequent paths, a 1 microsecond delay corresponds to a meter difference in path length. Alternatively, the delay span of the channel 10 microseconds is much smaller than the QPSK symbol period 2 milliseconds so the resultant bandlimited impulse response is approximately flat.
The QPSK constellation shows the effects of the fading channel; however, the signal still has four identifiable states. Increase the symbol rate to kbps and update the related channel property. As the signal bandwidth is increased from Hz to kHz, the signal becomes highly distorted. This distortion is due to the intersymbol interference ISI that comes from time dispersion of the wideband signal.
The delay span of the channel 10 microseconds is now larger than the QPSK symbol period 2 microseconds so the resultant bandlimited impulse response is no longer flat. Alternatively, the signal bandwidth is much larger than the coherence bandwidth, 50 kHz. Improve this question. Mahdi Eskandari Mahdi Eskandari 11 3 3 bronze badges. Add a comment. Sorted by: Reset to default. Highest score default Date modified newest first Date created oldest first.
References: 1 Goldsmith, Wireless Communications , chapters , Improve this answer. Robert L. I have another question here. For the pulse shaping filter, usually start with RRC en. I wrote the following code for RRC. I think this is true. I edit my question and my function is added there. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.
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