iosr-JCE   Volume-3 ~ Issue-2

Abstract: Orthogonal frequency division multiplexing (OFDM) is a form of multicarrier modulation technique with high spectral efficiency and immunity to interference. Despite of many advantages the main disadvantage of OFDM is that the time domain of OFDM signal which is a sum of subcarrier sinusoids leads to high Peak-to- Average power ratio (PAPR). A simple technique used to reduce the PAPR of OFDM signals is to clip the signal to a maximum allowed value, at the cost of bit error rate (BER) degradation and out-of-band radiation. The other method is Selective mapping method (SLM) technique which is a probabilistic technique for PAPR reduction with aim of reducing the occurrence of peaks in a signal. In this project partial transmit (PTS) scheme along with the threshold technique has been simulated using Matlab and the simulation results shows that the technique performs better. To compare the results SLM and clipping methods are also simulated.
Index Terms: Bit Error Rate (BER) Degradation, Inverse Discrete Fourier Transform (IDFT), Inverse Fast Fourier Transform (IFFT), Orthogonal Frequency Division Multiplexing (OFDM)), Partial Transmit Scheme
(PTS), Peak-to-Average power ratio (PAPR) and Selective Mapping Method (SLM).

[1] Xue Li,Vasu.D.Chakravarthy "Spreading Code Design of Adaptive Non-Contiguous SOFDM for Dynamic Spectrum Access", IEEE
Journal of Selected Topics in Signal Processing,vol.5,no.1,Jan. 2011.
[2] Henrik Schulze and Christian Luders. "Theory and Applications of OFDM and CDMA. Wideband Wireless Communications". Wiley, 2003.
[3] Y.Wu and W. Y. Zou, "Orthogonal frequency division multiplexing: A multi-carrier modulation scheme," IEEE Trans. Consumer
Electronics, vol. 41, no. 3, pp. 392–399, Aug. 1995.
[4] N. Dinur and D. Wulich, "Peak-to-average power ratio in high-order OFDM," IEEE Trans. Communications, vol. 49, no. 6, pp. 1063– 1072, Jun. 2001.
[5] Lingyin Wang and Ju Liu, Senio "PAPR Reduction of OFDM Signals by PTS With Grouping and Recursive Phase Weighting
Methods" IEEE Transactions on Broadcasting,vol.43,no.1,Jan. 2010.
[6] Jun Hou, Jianhua Ge, and Jing Li "Peak-to-Average Power Ratio Reduction of OFDM Signals Using PTS Scheme With Low
Computational Complexity" IEEE Transactions on Broadcasting, vol.57, no.1, March 2011
[7] Ms. V. B. Malode, Dr. B. P. Patil "PAPR Reduction Using Modified Selective Mapping Technique".Int. J. of Advanced Networking
and Applications, Volume:02, Issue: 02, Pages:626-630 (2010).
[8] G.Yue, X.Wang,M.Madihian "Peak-to-Average Power Ratio Reduction scheme with Threshold limited selection for orthogonal
frequency division multiplexing" IET Communications Vol. 2, No. 8, pp. 1034–1042,2008.
[9] Heung-Gyoon Ryu, Member, IEEE, Jae-Eun Lee and Jin-Soo Park, Member, IEEE "Dummy Sequence Insertion (DSI) for PAPR
Reduction in the OFDM Communication System" IEEE Transactions on Consumer Electronics, Vol. 94 50, No. 1, FEBRUARY 2004.
[10] Y. Zhou and T. Jiang, "A novelclipping integrated into ACE for PAPR reduction in OFDM systems," 2009 International Conference on Wireless Communications and Signal Processing, WCSP 2009, Mar.2009.

Abstract: In this paper, teletraffic data were collected from Airtel Nigeria Ltd. for a period of 18 months. Frequencies of occurrence of congestion in the network were derived from the teletraffic data using the Nigerian Communications Commission (NCC) benchmark. The dominant causes of congestion in the network were identified from the data and their value of occurrence was seen to be random in nature. A Poisson probability distribution model was therefore implemented for the prediction of congestion in the network. The identified four dominant causes of congestion and their percentage relative weights based on frequency of occurrence were: (i) X1: Faulty System (50.63%); (ii) X2: Faulty Trunk(s) (29.11%); (iii) X3: Power Failure (16.46%) and (iv) X4: Cable Cut (03.80%). MATLAB (M-file Data Acquisition Toolbox) programming environment was used to write a software program in C++ language that simulated the four dominant causes of congestion. Pearson Product Moment Correlation Coefficient formula was used to test the relationship between the measured and simulated congestion. The value r = 0.7487 was the correlation coefficient obtained between the measured and simulated results. This shows that the model is reasonably reliable.
Key words: Airtel, Congestion, Mobile network, Poisson, Probability.

[1] Webster‟s New World Dictionary, copyright © 2008 by Wiley publishing inc. indianapolic, Indiana.
[2] Dspace Vidyanidhi Digital Library, University of Mysore http://dspace.library.iitb.ac.in/jspui/handle/10054/426.html (current
March, 2009)
[3] K. Sriram: "Dynamic Bandwidth Allocation and Congestion Control Scheme for Voice and Data Multiplexing In Wide Band
Packet Technology". AT & T Bell Laboratories. Room 3H-607 Crawfords Comer Road Holmdel, New Jersey 07733. http://www.gap.upv.es/index/php.html (current April, 2009)
[4] David L. & Steven L: "Random Early Marking for Internet Congestion Control" T melbourne information technologies australia, Department of EEE. The University of Melbourne Carlton, Victoria, Australia 3053. http://www.kadhum.weebly.com/publibations.html (current April, 2009)
[5] Yong X., David H., Kishore R., Arvind V. & Shivkumar K.: "Accumulation-based Congestion Control" Department of Electrical, Electronics & Computer Studies EECS. University of California, Berkeley, CA 94720. http://www.arnetminer.org/viewpub.do.html (current April, 2009)
[6] Chandrayana K. & Kalyanaraman S. "Uncooperative Congestion Control" Rensselaer Polytechnic Institute, 110 Eight Street,
Troy, NY 12180. chandk@rpi.edu. http://www.jiti.com/v09/jiti.v9n2.091.106.pdf (current April, 2009)
[7] Journal on "Telecommunication Transmission Engineering", 3rd ed., Vol. 2, Bellcore, Piscataway, New Jersey, 1991. pp 21 - 38
[8] The Nigerian Communications Commission www.ncc.gov/index_e.htm (current, February, 2010)
[9] Dropped Call (TCH Drop-SDCCH Drop) – TCH Drop Analysis http://telefunda.blogspot.com/2010/10/dropped-calltch-dropsdcch- drop.html (current February, 2010)
[10] Airtel Nigerian Limited. A Technical Report Handbook For Operations Department Kaduna, Nigeria. 1991

Abstract:In this paper, improved algorithms for radix-8 FFT are presented. Various schemes have been proposed for computing FFT. It has Different target domains of applications and different tradeoffs between flexibility and performance. Typically, they need reconfigurable array of processing elements .The applications have been restricted to domains based on floating arithmetic. We introduce floating-point Arithmetic which is based on processing elements. After developing the FFT design we present a routing Algorithm and use topology to reduce power dissipation. These modified radix-8 algorithms provide savings of more than 33% in the number of twiddle factor evaluations

[1] H. Singh, M.-H. Lee, G. Lu, F. J. Kurdahi, N. Bagherzadeh, and E.M. C. Filho, "Morphosys: An integrated reconfigurable system
for dataparalleland computation-intensive applications," IEEE Trans. Comput.,vol. 49, no. 5, pp. 465–481, May 2000.
[2] PACT XPP Technologies [Online]. Available: http://www.pactxpp.com
[3] B. Mei, S. Vernalde, D. Verkest, H. D. Man, and R. Lauwereins,"ADRES: An architecture with tightly coupled VLIW processor
andcoarse-grained reconfigurable matrix," in Proc. FPLA, 2003, pp. 61–70.
[4] Chameleon Systems, Inc. [Online]. Available:http://www.chameleonsystems.com
[5] T. J. Callahan and J. Wawrzynek, "Instruction-level parallelism forreconfigurable computing," in Proc. IWFPL, 1998, pp. 248–257.
[6] W. Lee, R. Barua, M. Frank, D. Srikrishna, J. Babb, V. Sarkar, and S.P. Amarasinghe, "Space-time scheduling of instruction level
parallelismon a RAW machine," in Proc. ASPLOSV, 1998, pp. 46–57.
[7] B. Mei, S. Vernalde, D. Verkest, H. D. Man, and R. Lauwereins,"DRESC: A retargetable compiler for coarse -grained
reconfigurablearchitectures," in Proc. ICFPT, Dec. 2002, pp. 166–173.