International Journal of Futuristic Trends in Engineering and Technology ISSN: 2348-5264 (Print), ISSN: 2348-4071 (Online) Vol. 1 (05), 2014 Akshar Publication © 2014 http://www.ijftet.wix.com/research 40 Detection of Time Reversed Space Time Block Codes in Wireless Fading Environment (Paper ID: 50300620148) Devendra Kumar Rajesh P Vansdadiya Nandkishor S Vansdadiya Electronics and Communication Engineering Dept. Electronics and Communication Engineering Dept. Electronics and Communication Engineering Dept. Thapar University, Patiala Atmiya Institute of Technology and Science, Rajkot Thapar University, Patiala Abstract: Two transmit and one receive antenna design was presented by Alamouti in [5], where channel coefficients at adjacent time intervals are assumed to be same. When the channel suffers from intersymbol interference (ISI) due to large delay spread, Time Reversal Space Time Block Codes (TR-STBC) achieves better performance [8]. In frequency selective Multiple Input Multiple Output (MIMO) channel environment, loss of ‘quasi static’ assumption produce the ISI in TR-STBC. In this paper, a low complexity receiver is evaluated to mitigate the effect of inter symbol interference caused due to ‘quasi static’ assumption in TR-STBC in Nakagami-m fading channel. Keywords: Space time block codes (STBC), Time Reversal Space Time Block Codes (TR-STBC), Intersymbol interference (ISI), Multiple Input Multiple Output (MIMO),fast fading, Nakagami channel, Orthogonal frequency time division multiplexing (OFDM). I. INTRODUCTION Wireless communications has emerged as one of the fastest growing sectors of the communications industry.Wireless networks widely used today comprise: Wireless Local Area Networks, cellular networks, personal area networks and wireless sensor networks. Use ofWireless communication for data application such as internet and multimedia access is increased. So demand for reliable high-data-rate services is elevated quickly. However, it is hard to achieve reliable wireless transmission due to time varying multipath fading of wireless channel. Also, The range and data rate of wireless networks is limited. To enhance the data rates and the quality, multiple antennas can be used at the receiver to obtain the diversity. By utilizing multiple antennas at transmitter and receiver, significant capacity advantages can be obtained in wireless system. In a Multiple Input Multiple Output (MIMO) system, multiple transmit and receive antennas, can elevate the capacity of the transmission link. This extra capacity can be utilized to enlarge the diversity gain of the system. This results in development of Lucent’s “Bell-Labs layered space-time” (BLAST) architecture [1]-[4] and space time block codes (STBCs) [5]–[7] to attain some of this capacity. Spacetimecoding has utilized diversity and coding gains to achieve high data rate transmission. STBC gained popularity because of their capability to provide simple linear processing for maximum likelihood decoding at the receiver. II. TIME REVERSAL SPACE TIME BLOCK CODES (TR STBC) STBC scheme presented by Alamouti in [5] is a transmit diversity scheme, where two transmit and one receive antenna was used. The scheme was proposed for flat fading channel where the fading is assumed to be constant over two consecutive symbols. But further same scheme approach was applied to the frequency selective channels. Particularly, methods such as time reversal [8], OFDM [9], [10], and single-carrier Frequency domain equalization [11]–[13] have gained attention. But both OFDM and SC-FDE schemes, depends on transmission of cyclic prefix, which makes the channel matrix circulant. This characteristic diagonalizes the matrices by FFT and permits effective equalization in the frequency domain. In contrast, TR-STBC applies the Alamouti’s scheme on blocks instead of symbols in the time domain. At the receiver, spatiotemporal matched filter is used for transforming the received signal into block decoding and permits the perfect decoupling between the blocks [8], [13]. III. TR STBC SYSTEM MODEL TR STBC expands transmission of Alamouti’s scheme for frequency selective channels. It encodes normally arranged and time reversed blocks of symbols together [8], [14]. The data stream y is divided into two separate streams, 1 y and 2 y Then these two streams are transmitted from first antenna and second antenna in (alternating) time intervals. At first time interval, 1 y is transmitted form antenna 1 and 2 y is transmitted from antenna 2. So the corresponding received signal at the transmitter end is 1, 1, 1, 2, 2. 1, + t t t t t t r hy h y n   (1) where 1,t h is the channel between transmit antenna 1 and the receive antenna and 1,t n is the noise sample at the t time interval.