[SureshKumar, 2(5): May, 2013] ISSN: 2277-9655 http: // www.ijesrt.com (C) International Journal of Engineering Sciences & Research Technology [1318-1323] IJESRT INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH TECHNOLOGY Reduction of Roughness in FIR-SR Filter to DESIGN the Higher Order QAM Communication System R.Sureshkumar *1 , C.Elayaraja2 *1,2 Dhaanish Ahmed College of Engineering, India Suresh.abirakshan@gmail.com Abstract This paper presents a method of designing hybrid analog/asymmetrical square-root (SR) FIR filters. In addition to the conventional frequency domain constraints, the proposed method considers time-domain constraints as well, including the inter-symbol interference (ISI) and the opening of the eye pattern at the receiver output. Newly conceived parameter, the “roughness” of the analog/FIR-SR filter impulse response, is taken into account. The error-performance of a system employing a matched SR filter pair, in the presence of receiver timing jitter, is more strongly related to how well the roughness parameter is minimized, than it is to the maximizing of the eye width caused by the Nyquist pulse. QAM conveys a higher information bit rate (bits per second) than a BPSK or QPSK signal. With the hybrid analog/SR FIR filter co-design, examples show that using the proposed method can result in a more robust ISI performance & reduction in PAPR in the presence of the receiver clock jitter. Keywords: Beamforming , Multiple Input Multiple Output (MIMO), OFDM, receiver clock jitter, square-root filter. Introduction Finite impulse response (FIR) filter is a filter whose impulse response (or response to any finite length input) is of finite duration, because it settles to zero in finite time. The square-root (SR) filters[1] are conventionally designed by directly designing the zero-phase Nyquist filter[3] with a nonnegative frequency response, then getting the matched SR transmitter and receiver filters via a spectral factorization of the Nyquist filter polynomial.In this way, the SR filters obtained usually have asymmetric coefficients. The use of symmetric SR filters has been explored and their linear-phase character permitting approximately half as many tap multipliers in relation to filter length makes their use attractive. A. Existing system A well-known drawback of OFDM is that the amplitude of the resulting time domain signal varies with the transmitted symbols in the frequency domain. If the maximum amplitude of the time domain signal is large, it may push the amplifier into the non-linear region which breaks the orthogonality of the sub-carriers and will result in a substantial increase in the error rate. PAPR reduction techniques are associated with costs in terms of bandwidth or/and transmit power. Also, most of them require modifications in both transmitter and receiver which makes it non-compliant to the existing communication standards. Multiple signal representation methods, such as partial transmit sequence (PTS) and selected mapping (SLM) are well-known techniques which reduce the peak amplitude of the OFDM signal by manipulating the phase of subcarriers. The phase weights are sent asa side information to the receiver to recover the original symbols[1]. A new Precoding PAPR reduction technique is proposed in [2], based on grouping the OFDM subcarriers in clusters and changing the phase of clusters in a manner similar to the PTS method but without the drawback of sending explicit side information. The proposed technique neither requires additional bandwidth nor power. B. Proposed System In this paper we consider PAPR reduction techniques for multiple transmit antennas with Space Time Block Codes (STBC) in EM mode, which is the case for both WiMAX and LTE standards. Simulation result shows the