Real Time Image Transmission using FPGA on WARP test Bed

Abstract

he main aim of an effective wireless communication system is to provide a reliable link between the transmitter and the receiver. The wireless link is affected by many factors such as multipath fading, attenuation and shadowing. Due to these reasons a severely attenuated and distorted transmitted signal may arrive at the receiver. This results in a poor signal to noise ratio (SNR), which in turn yields a high bit error rate (BER) at the receiver. There are many solutions to deal with these problems. One solution is the use of channel coding techniques. But this technique involves complex processing and redundancy and hence requires more bandwidth. As a result, channel coding is used with some restrictions. Recent research on Multiple Input and Multiple Output (MIMO) systems shows that STBC is effective to reduce the fading effect in the wireless channel by providing diversity [41], [42] and this improves BER in receiver. Space–time block coding is a technique used in wireless communications to transmit multiple copies of a data stream across a number of antennas and to exploit the various received versions of the data to improve the reliability of data-transfer. Alamouti’s transmitter diversity scheme is a simplest space time block code technique with support of two transmit antennas and an arbitrary number of receive antennas. The simplest case of Alamouti’s Scheme utilizes two transmit antennas and one receive antenna. Alamouti’s transmit diversity scheme was the first example of a space-time code which requires only linear pre processing at receiver. The scheme has been implemented in many research papers but most of the results are presented through simulations. In this thesis the Alamouti scheme has been implemented on a WARP test board. The proposed system of Alamouti STBC transmits grey scale image through wireless channel in real time scenario on a WARP test bed. WARP is Wireless Access Research Platform. In this thesis we have implemented a MIMO communication system on WARP test bed which has a FPGA (VIRTEX IV) processor. We are using FPGA because it gives faster output than DSP processor. So if we are implementing receiver which has more complexity than Transmitter on FPGA then it will give results faster than DSP. We have implemented Alamouti STBC for different modulation schemes and with different number of transmitting and receiving antennas. Also using Alamouti STBC for different number of transmitting and receiving antennas Real time transmission of Grey Scale image has also been done using WARP board and different performance metrics are calculated and compared. The WARP board is equipped with four radio cards which are responsible for processing of signal to be transmitted and received. The signal is modulated by different modulation techniques for their transmission and Bit Error Performance (BER) of these techniques are compared to show best modulation technique amongst all. It can be seen that BER for Binary Phase Shift Keying (BPSK) modulation technique is least but increases as the order of modulation increases.