Volume 12, Issue 1, January 2012

Generalized parallel concatenated block codes based on BCH and RS codes: construction and Iterative decoding [Full Text]

A. Farchane, M. Belkasmi and S. Nouh

Abstract—
In this paper, a generalization of parallel concatenated block (GPCB) codes based on BCH and RS codes is presented. On the sender side two systematic encoders are used and separated by an interleaver. In the receiver side, the Chase-Pyndiah algorithm is utilized as component decoder in an iterative process. The effect of various component codes, interleaver sizes and patterns, and the number of iterations are investigated using simulations. The simulation results show that the slope of curves and coding gain are improved by increasing the number of iterations and/or the interleaver size. From the simulations we observe that the performance GPCB based on RS become worse when increasing the length of the component codes. This is differing with the knowledge that increasing the codes’ length leads to better performance.The comparison between GPCB based on BCH only, RS only or BCH and RS codes shows that the performance of the GPCB based on BCH codes are the best and the ones based on BCH and RS codes fall in between the two other GPCB codes.

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T-H Differential Pseudo-Random Pulse: A New UWB System for LR-WPAN Applications [Full Text]

N. Rebhi, A. Kachouri, M. Samet and D. Fournier Prunaret

Abstract—
Ultra Wide Band is a new technology that has received much attention for its peculiar advantages: high-bandwidth, extremely low power spectral density, propagation robust to fades, ability to penetrate materials, possibility to coexist in the same spectrum with other modulation schemes. UWB Impulse Radio systems are particularly promising for short-range and low bit rate wireless communications as they combine reduced complexity with multipath and multiuser capabilities. One of the most important applications of UWB is Wireless Personal Area Networks (WPAN). Moreover a standard for such systems was established by the IEEE802.15.4a group. In this paper, a new ultra-wide-band modulation scheme so-called Time-Hoping Differential Pseudo Random Pulse (TH-DPRP) is presented, and evaluated on various IEEE 802.15.4a standard channels models. Results show that TH-DPRP experience little degradation under multipath environments due to the simple transceiver, the detection principle, and the different technical choice combined in this system.

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New efficient decoder for product and concatenated block codes [Full Text]

Abderazzak Farchane and Mostafa Belkasmi

Abstract—In this paper a new decoder for product and concatenated codes is introduced. The proposed decoding algorithm outperforms the one of Chase-Pyndiah by 1dB for Parallel concatenated codes and 0.4dB for product codes. As regards, the performances of serially concatenated codes are similar for the two decoders. The proposed decoder use predetermined scaling factor, which must be re-optimized whenever we change the decoder circumstances. To overcome this problem, we have adapted this parameter to the circumstances of the channel, the codes and modulation scheme. Moreover, our decoder does not need to normalize the extrinsic information at each decoding stage. So, this reduces the complexity of the proposed decoder.

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Effect of Carrier Frequency Offset on SER of OFDM System [Full Text]

Ms Bhagyashri A. Warhade, Dr B P Patil and Prof. Prabha Kasliwal

Abstract—
Orthogonal Frequency Division Multiplexing (OFDM) is a key modulation technique for achieving high data rates and spectral efficiency requirements for wireless communication systems. But OFDM is very sensitive to carrier frequency offset (CFO) which destroy the orthogonality of the subcarriers and it gives rise to inter-carrier interference (ICI). This ICI degrades the performance of OFDM systems significantly. The most important performance evolution metrics are Bit Error Rate (BER) and the symbol error rate (SER) which characterizes the associated degradation more accurately. In this paper, the expression for SER using QPSK modulation under AWGN channel is studied and simulation results are provided. The effect of carrier frequency offset on SER is shown in simulation results.