Anomaly Detection Techniques for Wireless Sensor Networks – A Survey

Abstract: Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation scheme, which is frequently used in various wireless communication systems. There are several kinds of challenges in front of the wireless communication system. The OFDM performs these tasks very well by carrying multicarrier into one single channel but there are problems in the implementation of the OFDM completely. One of the major problems in OFDM system is PEAK TO AVERAGE POWER RATIO (PAPR). High PAPR results from large envelope fluctuations in OFDM signal which requires a highly linear power amplifier (PA).This paper focuses on the reduction of the PAPR using a definite change in the phase shift which occurs in the previous works done. A new phase has been introduced into the contrast reducing the main phase by one degree of computation. Previous researchers have put three phase changes for the co ordination of N=128 and N=256 where as per the new approach in this paper, there would be four phase changes as defined earlier. The phase shift has been performed along with two techniques and their combination namely SLM, CLIPPING and HYBRID (SLM+CLIPPING) TECHNIQUE

Keywords: OFDM, PAPR, Power Amplifier, SLM, Clipping.