Abstract: Signal to Noise Ratio (SNR) is an important index for wireless communications. There are many methods for increasing SNR. In CDMA systems, spreading sequences are used. To increase SNR, we have to improve spreading sequences. In classical approaches, the expression of SNR is not differentiable in terms of the parameter of the spreading sequences even in no fading situations. Thus, we express it as the differentiable form and construct the non-linear programing for maximizing SNR. In particular, we solve the problem of maximizing SNR numerically by obtaining spreading sequences whose SNR is guaranteed to be high. Also we use MATLAB programming for the same.
Keywords: MATLAB, Noise Ratio (SNR), CDMA, differentiable.
1. D. V. Sarwate,”Bounds on cross correlation and autocorrelation of sequences”, IEEE Transactions on Information Theory
2. L. R. Welch,”Lower bounds on the maximum cross correlation of signals,
3. R. Gold, ”Optimal binary sequences for spread spectrum multiplexing
4. G. Heidari-Bateni and C. D. McGillem. ”A chaotic direct-sequence spread-spectrum communication system.” IEEE Transactions on communications.
5. K.S. Halle, C.W. Wu, M. Itoh and L.O. Chua. ”Spread spectrum communication through modulation of chaos.” International Journal of Bifurcation and Chaos 3.02 (1993): 469-477
6. Y. Soobul, K. Chady and H. C.S. Rughooputh. ”Digital chaotic coding and modulation in CDMA.” Africon Conference in Africa, 2002. IEEE AFRICON. 6th. Vol. 2. IEEE, 2002.
Spreading sequences using periodic orbits of chaos for CDMA, Electronics Letters 35.7 (1999), 545-546.
7. C.C. Chen, K. Yao, K. Umeno and E. Biglieri, ”Design of spread spectrum sequences using chaotic dynamical systems and ergodic theory.” IEEE Transactions on Circuits and Systems I: Fundamental Theory
8. C. E. Shannon, ”A mathematical theory of communication,” Bell System Technical Journal, Volume 27, Issue 3, 379-423 (1948).
9. J. Proakis, ”Digital Communications. 1995”, McGraw-Hill, New York.  S. Verdu and S. Shamai, ”Spectral efficiency of CDMA with random spreading.” IEEE Transactions on Information theory 45.2 (1999): 622
10. T.S.Rappaport. Wireless Communications –principles and practices, 2nd Edition, (2002 by Prentice-Hall), Upper Saddle River, New Jersey. Ch.5. 2. H. Taub, D. L. Schilling and G. saha, ―Principles of communication systems‖, third edition,(2008 by Tata McGraw-Hill), ch.15. 3. `Mabula Martina Cheeli, ―CDMA network simulator for wireless
communication applications‖, Graduation Degree Thesis, Department of Electrical Engineering, University of Cape Town 2006.
11. Rpke, T. H. Christensen, and J. O. Jensen, “Information and communication technologies a new round of household electrification,” Energy Policy, vol. 38, no. 4, pp. 1764 – 1773, 2010.
12. Y. Park, J. Ha, S. Kuk, H. Kim, C. J. Liang, and J. Ko, “A feasibility study and development framework design for realizing smartphone based vehicular networking systems,” IEEE Transactions on Mobile Computing, vol. 13, no. 11, pp. 2431– 2444, Nov. 2014.
13. C. C. Huang, P. Y. Lee, and P. Y. Chen, “Implementation of a smartphone based portable doppler flowmeter,” in Proc. IEEE International Ultrasonics Symposium, Oct. 2011, pp. 1056–1059.
14. Rahmati and L. Zhong, “Studying smartphone usage: Lessons from a four-month field study,” IEEE Transactions on Mobile Computing, vol. 12, no. 7, pp. 1417–1427, July 2013.
15. M. Sauter, 3G, 4G and Beyond: Bringing Networks, Devices and the Web Together, Wiley, 2012.
16. J. Proakis and M. Salehi, Digital Communications, McGraw-Hill Education, 2007.
17. S. Dang, J. P. Coon, and D. Simmons, “Combined bulk/per-tone relay selection in two-hop OFDM systems,” Wireless Communications Letters, IEEE, 2015 (under review).
18. Z. Ma, A. Gholamzadeh, B. Tang, S. Dang, and S. Yang, “Matlab based simulation of the efficiency of the complex ofdm on power line communication technology,” in Proc. Fourth International Conference on Instrumentation and Measurement, Computer, Communication and Control, Sept. 2014, pp. 374–378.