An FPGA implementation of Alamouti's transmit diversity technique

Abstract

Wireless communications have grown tremendously over the last decade, wireless LAN and mobile telephones have been the main reasons for the growth. There is demand for ever faster wireless communications as this will allow for new applications such as wireless broadband Internet access. Multi-Antenna transmission schemes, using multiple antennas at the transmitter and/or receiver, and associated coding techniques have been proposed as a way to fulfill the demand for increased capacity and the performance of wireless communication systems. They are particularly attractive because they do not require any additional transmission bandwidth, and unlike traditional systems use multipath interference to their benefit. However, there are limits to growth, and the radio spectrum used for wireless communications is a finite resource. Therefore considerable effort has been invested in making more efficient use of it. Using the spectrum more efficiently caters for the ever increasing demand for faster communications since more bits per second can be transmitted using the same bandwidth. This project aims to present the Xilinx/Altera FPGA implementation of a multiple antenna wireless communications system based on Alamouti’s transmit diversity scheme [1]. Alamouti’s transmit diversity scheme is a space-time block code with support for two transmit antennas and an arbitrary number of receive antennas. The implementation demonstrates this space-time code in a baseband system with two transmit and just one antenna at the receiver with the encoding and decoding algorithms using Verilog Hardware Description Language (HDL), which is modeled to establish an end-to-end link over real wireless channels to form a complete multiple antenna wireless communications system.