Journal of Signal Processing Systems 52, 35–44, 2008 * 2007 Springer Science + Business Media, LLC. Manufactured in The United States. DOI: 10.1007/s11265-007-0071-8 Architectures for the Implementation of a OFDM-WLAN Viterbi Decoder F. ANGARITA, M. J. CANET, T. SANSALONI AND J. VALLS Department of Electronic Engineering, Polytechnic University of Valencia, 46730, Grao de Gandı´a, Valencia, Spain V. ALMENAR Department of Telecomunications, Polytechnic University of Valencia, 46730, Grao de Gandı´a, Valencia, Spain Received: 30 August 2006; Revised: 20 March 2007; Accepted: 20 March 2007 Abstract. This paper describes the design of a soft decision Viterbi Decoder for orthogonal frequency division multiplexing-based wireless local area networks and evaluates different architectural options by means of their field programmable gate-array (FPGA) implementation. A finite precision analysis has been performed to reduce the data-path widths under the specifications of IEEE 802.11a and Hiperlan/2 standards. Four implementation strategies (register exchange, trace back, trace back with double rate memory read and pointer trace back) for the survivor management unit have been evaluated together with two different normalization methods for the add–compare–select unit. The results of the implementation in FPGA have been given and it is shown that register exchange and pointer trace back architectures with pre-normalization in the add–compare–select unit achieve the best performance. Both architectures can decode 200 Mbps in a Virtex-4 device with lower latency that the conventional trace back one and pointer trace back exhibits the lowest power consumption, these characteristics make them suitable for future multiple-output multiple-input WLAN systems. Keywords: OFDM, viterbi, wireless LAN 1. Introduction A wireless local area network (WLAN) provides wideband wireless connectivity between electronic devices. The two standards for WLAN Hiperlan/2 [1] and IEEE 802.11a [2], defined by ETSI BRAN and IEEE respectively, support multiple transmission Fmodes_, providing data rates up to 54 Mbps in the 5 GHz band, depending on channel characteristics. Higher data rates are expected with the inclusion of multiple-output multiple-input (MIMO) techniques in IEEE 802.11n [3]. All these standards are based on orthogonal frequency division multiplexing (OFDM). In order to combat fading effects on OFDM sub-carriers, caused by frequency selective channels, they employ forward error correction (FEC) coding together with interleaving. The FEC coding used is based on an industry standard 1/2-rate convolutional code. Effective decoding of the convolutional code is an important aspect when designing receivers for WLAN. The optimal solution for decoding convolu- tional codes is a dynamic programming algorithm known as Viterbi Algorithm [4, 5]. This algorithm is an efficient implementation of the maximum-likeli- hood decoder; it searches all the possible code words of the convolutional code and detects the one that is the most likely to be the received sequence. In WLAN standards the convolutional code is described by generator polynomials G1=133 OCT and