Single Parity Check Product Code in MB-OFDM Ultra Wideband System Norulhusna Ahmad College of Science and Technology, Universiti Teknologi Malaysia, International Campus, KL, Malaysia. nhusna@ic.utm.my S. Kamilah S-Yusof, Norsheila Fisal Faculty of Electrical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia {kamilah,sheila}@fke.utm.my Abstract— In ultra wideband (UWB) system, multiband orthogonal frequency division multiplexing (MB-OFDM) has been proposed to provide high-speed transmission for short- range wireless links. In this paper, 2 dimensional (2D) single parity check product code (SPCPC) is investigated in MB-OFDM UWB communication for Rayleigh fading channel and additive white Gaussian noise (AWGN) channel in order to improve the error performance. The encoder and parallel decoder of the 2D- SPCPC are explained. It is shown that the proposed model may provide significantly better error performance compared to the conventional MB-OFDM at low SNR, but with complexity tradeoff. Keywords-MB-OFDM; turbo product code; ultra wideband I. INTRODUCTION The UWB communication system has become an emerging technology that offers great satisfaction for future short and medium range wireless communication networks. It also has a potential for providing high data rates at the same time has the robustness in multipath fading environment. Any wireless communication system with spectral occupancy more than 500 MHz or fractional bandwidth higher than 0.2 can be considered as UWB system. In 2002, Federal Communications Commission (FCC) regulation allowed UWB to be operated at 3.1 to 10.6 GHz band without license requirement. The approval comes with limited power signal in order to allow coexistence with traditional and protected wireless services to ensure a minor interference [1]. In order to provide a secure transmission, the power spectrum is embedded into the noise floor. There are two techniques that have been proposed in UWB technology which are impulse radio (IR) and multiband orthogonal frequency division multiplexing (MB-OFDM). MB- OFDM UWB transmits several lower rate streams using different carriers with minimum frequency band (above 500MHz) instead of using the entire UWB frequency band. In MB-OFDM UWB communication, the error correcting code proposed in IEEE 802.13a is using convolutional codes. However, turbo code has more robust performance compare to convolutional code as it close to the Shannon’s channel capacity theorem in AWGN channel. In turbo codes, it can be categorized into convolutional turbo code (CTC) and turbo product code (TPC) according to the type of constituent encoder [2]. CTC is built from a parallel concatenation of Recursive Systematic Convolutional (RSC) encoders separated by a pseudo random interleaver while TPC consist of the product of two systematic block codes separated by uniform interleaver [2]. The performance of turbo code is much affected by different parameters such as component codes, block size, interleaver design and weight spectrum [3], [4]. Component codes of TPC are chosen to give specific code parameters for instance code rate, error correcting capability and codeword length. Generally, the linear block code family that are used as a component codes are Reed-Solomon (RS) codes [5], Bose- Chaudri-Hochquenghem (BCH) codes [6], Hamming codes [7] and single parity check (SPC) product codes [8]. The main challenge in TPC application is to reduce the overhead as low as possible which is able to sustain the quality of transmission. SPC product code (SPCPC) provides the fewest parity bits with the highest code rate among the other codes [12]. In multidimensional SPCPC, maximum a posteriori (MAP) decoder was shown to have very good error performance [9]. In [10], the performance improvement depends on the dimensionality of the SPCPC. However, as the dimensionality increased, the code rate is decreased. Moreover, the block length is not flexible. In order to overcome the flexibility of the block length, [11] proposed the use of parallel decoder. Later, [12] proposed multiple serial and parallel concatenated SPC. It was found that parallel decoder can give better error performance at low and moderate signal to noise ratio (SNR) but with complexity trade-off. In the literature of MB-OFDM UWB, the application of turbo codes is very limited. For examples, concatenated Reed Solomon-convolutional codes (RS-CC) was explored in [13] under UWB channel and the performance is compared to convolutional coding and turbo coding. Even though the proposed coding outperforms turbo code and convolutional code, it occurs only at high SNR. In [14], the performance of turbo codes and repeat-accumulate (RA) codes as well as bit loading algorithm was studied. It is shown that using turbo coding, the power efficiency can be improves up to 5dB depending on data rates. Another type of turbo codes is low density parity check (LDPC) codes. It was studied in [15] using quasi-cyclic LDPC and the performance is compared with This work was supported through the scholarship of doctoral study by the Universiti Teknologi Malaysia and Ministry of Higher Education Malaysia 9781-4244-3941-6/09/$25.00 © 2009 IEEE Authorized licensed use limited to: UNIVERSITY TEKNOLOGI MALAYSIA. Downloaded on February 15,2010 at 23:21:41 EST from IEEE Xplore. Restrictions apply.