International Journal of Electronics and Electrical Engineering ISSN : 2277-7040 Volume 2 Issue 3 (March 2012) http://www.ijecee.com/ https://sites.google.com/site/ijeceejournal/ 1 BER PERFORMANCE OF OFDM SYSTEM WITH 16-QAM AND VARYING LENGTH OF GUARD INTERVAL Dr. Amandeep Singh Sappal , Parneet Kaur Punjabi university, Patiala India. sappal73as@yahoo.co.in , Parneet3001@gmail.com Abstract. Orthogonal frequency division multiplexing scheme being spectrally efficient is used in modern communication systems. To achieve error free communication guard interval is inserted using cyclic prefix and zero padding. The Bit Error Rate (BER) performance for orthogonal frequency division multiplexing (OFDM) system with 16-QAM and varying length of guard interval (GI) is presented. Keywords: BER, Cyclic prefix, Intersymbol interference, Virtual carriers, Zero padding 1 Introduction An OFDM signal may incur out-of-band radiation, which causes non-negligible adjacent channel interference (ACI). It is clearly seen from Figure 1 that the first side lobe is not so small as compared to the main lobe in the spectra. Therefore, OFDM scheme places a guard band at outer subcarriers, called virtual carriers (VCs), around the frequency band to reduce the out-of band radiation. [3] The OFDM scheme also inserts a guard interval in the time domain, called cyclic prefix (CP), which mitigates the inter-symbol interference (ISI) between OFDM symbols [1]