A PIPELINED IMPLEMENTATION OF OFDM TRANSMISSION ON RECONFIGURABLE PLATFORMS Ahmad Sghaier, Shawki Areibi and Bob Dony School of Engineering, University of Guelph, Guelph, ON, Canada, N1G 2W1 Emails: sghaiera@uoguelph.ca, sareibi@uoguelph.ca, rdony@uoguelph.ca ABSTRACT The principles of orthogonal frequency division multiplexing (OFDM) modulation have been around since 1960s. However, recently, the attention toward OFDM has grown dramatically in the field of wireless and wired communication systems. This is reflected by the adoption of this technique in applications such as digital audio/video broadcast (DAB/DVB), wireless LAN (802.11a and HiperLAN2), broadband wireless (802.16) and xDSL. In parallel, Field Programmable Gate Arrays (FPGAs) are also emerging as a fundamental paradigm in the implementation of these standards. This is due to their increased capabilities (speed and resources). Moreover, the FPGA's programmability make them a preferable choice for evolving standards in comparison with ASIC fixed designs. In this work, a pure VHDL design, integrated with some intellectual property (IP) blocks, is employed to implement an OFDM transmitter according to the IEEE 802.11a WLAN standard. The proposed design has been mapped and tested on Xilinx Virtex-II Pro (XC2VP30-7ff896) FPGA, and approximately 25% of the total available fabric was occupied. Index Terms— FPGA, VHDL, OFDM, 802.11a 1. INTRODUCTION Wireless communications standards and digital subscriber lines technology, in addition to other communication technologies, are utilizing the widely adopted Orthogonal Frequency Division Multiplex (OFDM) technique. This is due to the genuine advantage of OFDM over single carrier system in multi-path fading channels. Among the standards that are based on OFDM are the IEEE 802.11a&g for Wireless Local Area Networks (WLANs), WiFi, and the growing IEEE802.16 for Metropolitan Access, Worldwide Interoperability for Microwave Access (WiMAX). The fast growth of these standards has paved the way for OFDM to be among the widely adopted standards and to be as a fundamental candidate for the construction of the next generation telecommunication networks. The aim of this work is to implement the digital baseband part of the physical layer of an OFDM transmitter that conforms to the 802.11a standard. The objective is to show FPGA's capability to accommodate such standards, and to emphasize on their programmability feature. The implementation is performed by utilizing VHDL (VHSIC Hardware Description Language), and targeting Xilinx Field Programmable Gate Arrays (FPGA). In this work, the developed IP cores, available on-line [8], could be easily extended to design other OFDM-based systems, for example fixed and mobile WiMAX. The paper is organized into six sections. Section 2 discusses the basics of OFDM. In section 3, the main parameters of the IEEE 802.11a standard is introduced, while section 4 presents the proposed architecture and design environment. Section 5 demonstrates the correctness of the design and the simulation and implementation results. Finally, the paper is concluded in section 6. 2. PRINCIPLES OF OFDM Orthogonal Frequency Division Multiplexing (OFDM) is a parallel transmission scheme; the scheme was firstly employed in the Digital Audio Broadcasting (DAB) standard in 1995. Later, the wireless field has adopted OFDM for the benefits it has provided over (Frequency division Multiplexing) FDM. In 1999, the IEEE 802.11a standard was released based on OFDM [1], and later in 2004 the IEEE 802.16-2004 standard for fixed broadband wireless access was released [6]. The wide adoption continued when the IEEE 802.16e standard for mobile wireless access was released. This increased growth in OFDM popularity was due to the advantages embedded, such as high data rates and immunity to multipath fading channels. OFDM has attained the high data rate by splitting the data stream into a number of low-rate sub-carriers (SC) instead of utilizing one carrier at a high rate. To improve the bandwidth utilization, the SCs are selected such that they are orthogonal, where this orthogonality allows the SCs to overlap without interference. Therefore, the spectrum is saved, resulting in higher bandwidth utilization over a traditional Frequency Division Multiplexing (FDM) [5].