IEEE VTS Workshop on Wireless Vehicular Communications, Halmstad, Nov 11, 2015

Transcription

1 On Multilink Shadowing Effects in Measured V2V Channels on Highway Mikael Nilsson Industrial Ph.D. student - Lund University / Volvo Cars Presented by: Carl Gustafson Post-Doc. - Lund University Mikael G. Nilsson¹, ², Dimitrios Vlastaras¹, Taimoor Abbas¹, Björn Bergqvist², and Fredrik Tufvesson¹ ¹Lund University, Dept. of Electrical and Information Technology, Box 118, SE Lund, Sweden ²Volvo Car Corporation, SE Göteborg, Sweden 1

2 outline Motivation & Contribution The test Results Path loss exponent Coherence time Sample reflective cross-correlation coefficient Summary and Conclusions 9th European Conference on Antennas and Propagation, Lisbon, Portugal, April

3 Motivation & contribution Motivation, Most of the studies by using ITS-G5 or DSRC communication have considered communication between one transmitter (TX) and one receiver (RX), i.e. the single link case. A few studies have considered communication between one TX and several RX or vice versa, i.e. the multilink case. In the multilink case, wireless communication system using multihop techniques, can overcome the issue with shadowed cars in V2V systems. Contribution, the results show that it is essential to consider the correlation of the large scale fading processes in the multilink case, as the correlation coefficients can have both large negative and large positive values. 3

4 The test 4

5 The test cars Test 5

6 The volvo s60 & antenna pattern Test 6

7 Test setup & parameters Test 7

8 Test scenario Test 8

9 results 9

10 path loss exponent estimation The path loss exponent for ordinary Least Squares (LS) estimation is Results But we can make use of the information that the distance to transmitting car is known even though the data packets is not received correctly. Therefore the Maximum Likelihood (ML) estimation was applied and the path loss exponent value is then C. Gustafson, T. Abbas, D. Bolin, and F. Tufvesson, Statistical modeling and estimation of censored path loss data, ArXiv e-prints, [Online]. Available: 10

11 coherence time The auto- and cross-correlation calculation is based on the sample reflective correlation coefficient, where the mean is not subtracted in the calculation of the correlation coefficient. Results As seen in the figure the coherence time for the multilink case in test scenario, Convoy A, can vary from a few seconds up to almost 2 minutes. 11

12 Large scale fading 12

13 cross-correlation 13

14 SUMMARY AND CONCLUSIONS Presented are, initial results of a measurement based analysis on multilink shadowing effects in a highway scenario using V2V communication at 5.9 GHz. Focus in the analysis, Coherence time of the large scale fading process. Sample reflective cross-correlation coefficient for the multilink case. The coherence time can vary from a few seconds up to almost 2 minutes when four cars are driving in a convoy on the highway. So even though that the transceivers transmit with a high repetition rate the receiving car can be shadowed in the range of minutes and will experience long periods with received power levels being much lower than predicted by the path loss model only. 14

15 SUMMARY AND CONCLUSIONS Analysis of the sample reflective cross-correlation coefficients between all links in our setup shows that there are simultaneous positively and negatively correlated links. By using links between cars that receives signals with high power the wireless communication system can overcome the issue with shadowed cars. Multihop techniques, which e.g. are implemented in the ITS-G5 standard, can overcome this issue by relaying the information via another car. The measurements give a clear indication that this approach can be successful. 15

16 Q&A 16