Suri V S Lalithamadhuri, K. Ramadevi / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 4, Jul-Aug 2013, pp.2463-2467 2463 | P a g e Ofdm Implementation Using Self-Cancellation Techniques in Wireless Networks Suri V S Lalithamadhuri*, K. Ramadevi** *(Dept. of E.C.E, University college of Engineering, JNTUK,Kakinada, India. **(Dept. of E.C.E, University college of Engineering, JNTUK, Kakinada, India. ABSTRACT With the rapid growth of digital communication in recent years, the need for high speed data transmission is increased. Moreover, futureWirelessSystemsare expected to support a wide range of services which includes video, data and voice. OFDMis a promising candidate for achieving high data rates in mobile environment because of its multicarrier modulation technique and ability to convert a frequency selective fading channel into severalnearly flat fading channels. Now OFDM is being widely used in wireless communications standards, such as IEEE 802.11a, the multimedia mobile access communication (MMAC), and the HIPERLAN/2. However, one of the main disadvantages of OFDM is its sensitivity against carrier frequency offset and high PAPR which causes intercarrier interference (ICI). This paper deals with design of an OFDM mechanism in a wireless technology and implementation of double frequency hopping in CDMA to overcome inter channel interferences. Keywords- FHCDMA, HIPERLAN, ICI, MMAC, OFDM I. INTRODUTION This project investigates an efficient ICI cancellation method termed ICI self-cancellation scheme for combating the impact of ICI on OFDM systems. The ICI self-cancellation scheme is a techniqueinwhichredundantdatais transmitted onto adjacent sub-carriers such that the ICI between adjacent sub-carriers cancels out at the receiver. OFDM-Impact on Wireless Networks Orthogonal Frequency Division Multiplexing (OFDM) is a special form of multi carrier modulation technique which is used to generate waveforms that are mutually orthogonal. In an OFDM scheme, a large number of orthogonal, overlapping, narrow band sub-carriers are transmitted in parallel. These carriers divide the available transmission bandwidth. The separation of the sub- carriers is such that there is a very compact spectral utilization. With OFDM, it is possible to have overlapping sub channels in the frequency domain, thus increasing the transmission rate. In order to avoid a large number of modulators and filters at the transmitter and complementary filters and demodulators at the receiver, it is desirable to be able to use modern digital signal processing techniques, such as fast Fourier transform (FFT). After more than forty years of research and development carried out in different places, OFDM is now being widely implemented in high-speed digital communications. OFDM has been accepted as standard in several wire line and wireless applications. Due to the recent advancements in digital signal processing (DSP) and very large-scale integrated circuits (VLSI) technologies, the initial obstacles of OFDM implementations do not exist anymore. In a basic communication system, the data are modulated onto a single carrier frequency. The available bandwidth is then totally occupied by each symbol. This kind of system can lead to inter-symbol-interference (ISI) in case of frequency selective channel. The basicidea of OFDM is to divide the available spectrum into several orthogonal sub channels so that each narrowband sub channels experiences almost flat fading. Many research centers in the world have specialized teams working in the optimization of OFDM systems. The attraction of OFDM is mainly because of its way of handling the multipathinterference at the receiver.Multipath phenomenon generates two effects (a) Frequency selective fading and (b) interference (ISI). The "flatness” perceived by a narrowband channel overcomes the frequency selective fading. On the other hand, modulating symbols at a verylow rate makes the symbols much longer than channel impulse response and hence reduces the ISI. Use of suitable error correcting codes provides more robustness against frequency selective fading. The insertion of an extra guard interval between consecutive OFDM symbols can reduce the effects of ISI even more. Theuse of FFT technique to implement modulation and demodulation functions makes it computationally more efficient. OFDM systems have gained an increased interest during the last years. It is used in the European digital broadcast radio system, as well as in wired environment such as asymmetric digital subscriber lines (ADSL). This technique is used in digital subscriber lines (DSL) to provides high bit rate over a twisted-pair of wires. II. ADVANTAGES & APPLICATIONS OF OFDM