Princy Pathak Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 8( Version 6), August 2014, pp.49-55 www.ijera.com 49 | Page A Novel Alamouti STBC Technique for MIMO System Using 16- QAM Modulation and Moving Average Filter Princy Pathak 1 , Prof. Rashmi Pandey 2 1 Research Scholar, M-Tech in Digital Communication, 2 HOD, Deptt. of Electronics & Communication, VIT Bhopal Abstract The wireless communication is the emerging field of research among communication researchers and they are continuously working towards the reduction if error occurred in the signal during transmission through wireless media. In this paper the wireless system is simulated with the application of Alamouti space time block codes (STBC) with MIMO and MISO configurations to compare the results. The modulation technique used here is 16-QAM which is giving better results than other counterparts and to enhance the performance of the system i.e. to reduce the effect of errors on data we have applied a moving average filter(MAF). The performance of the system is shown with the simulation results with variable data sizes and found that the proposed approach is better for the system. Keywords- Alamouti STBC, QAM, MIMO and MISO. I. INTRODUCTION Multiple-input multiple-output (MIMO) system is known to exploit the antenna diversity to develop the performances of wireless communication systems using multiple antenna elements at the transmitter and receiver ends. The main objective of MIMO technology is to improve bit error rate (BER) or the data rate of the communication by applying signal processing techniques at each side of the system. The capacity increases linearly with the number of antennas while using MIMO however it gradually saturates. MIMO system can obtain both multiplexing gain and diversity gain which can help significantly increase the system capacity. The earliest studies considering MIMO channels were carried out by Foschini [2] and Telatar [3]. MIMO can be divided into two main classes, spatial multiplexing (SM) and STC. In a wireless communication system the mobile transceiver has a limited power and also the device is so small in size that placing multiple antennas on it would lead to correlation at the antennas due to small separation between them. To avoid this, the better thing to do is to use multiple transmit antennas on the base station and the mobile will have only one. This setting is called as Multiple Input Single Output (MISO) transmit-diversity. A scheme with two transmit and one receive antenna is a special case and is known as Alamouti STBC. The Alamouti scheme is well known since it provides full transmit diversity. For coherent detection the perfect channel state information is available at the receiver with consideration. On the other hand, when there is high mobility and the channel conditions are fluctuating rapidly it may be difficult to obtain perfect or close to perfect estimates for the channel. To improve this problem another space-time block coding techniques known as DSTBC has been proposed in [4]. In this technique, two serial transmitted symbols are encoded into phase differences and the receiver recovers the transmitted information by comparing the phase of the current symbol with the previously received symbol. Two antennas are used, to send two OFDM symbols and their conjugate functions, in two time slots, which bring a diversity gain without having to compromise on the data rate. Through the open air media, the transmitted symbols will suffer from channel fading and at the receiver, their sum would be received. Here is the schematic diagram of an Alamouti wireless system in 2x2 MIMO mode. Fig. 1.1 A 2x2 MIMO wireless system using the Alamouti block code Space-Time Block Codes Space-time block codes (STBC) are a generalized version of Alamouti scheme. These codes have the same key features. That is, they are orthogonal and can achieve full transmit diversity specified by the number of transmit antennas. In other words, space-time block codes are a complex version of Alamouti’s space-time code, where the encoding and decoding schemes are the same as in RESEARCH ARTICLE OPEN ACCESS