Norulhusna Ahmad

IR-HARQ scheme on Bit-Interleaved Coded Modulation

This paper proposes an error control mechanism for data transmission defined as simple Hybrid Automatic Repeat-reQuest (ARQ) utilizing Bit-Interleaved Coded Modulation (BICM). The study investigates the Bit Error Rate (BER) performance of wireless communications using high rate Hybrid ARQ enabled by the proposed Bit-Interleaved Coded Modulation with Iterative Decoding (BICM-ID) option. The Incremental Redundancy Hybrid ARQ (IR-HARQ) technique generates the same frame during retransmission and the frame is discarded with limited retransmissions. This study investigates the BER performance of different techniques which are combination of BICM-HARQ without iterative decoding, the independent BICM and BICM-ID in half rate recursive systematic code. The system with HARQ scheme shows good improvement compared to independent case.

Analysis of recursive systematic convolutional turbo codes in MB-OFDM UWB with channel estimation

Ultra wideband (UWB) system requires high data rate transmission for a short wireless link application. The application of turbo codes in the system will improve the bit error rate (BER) performance. In this paper, the analysis of recursive systematic convolutional (RSC) turbo codes in the multiband orthogonal frequency division multiplexing (MB-OFDM) will be investigated in UWB channel with channel estimation. There are two types of channel estimation considered in the analysis which are Least Square (LS) estimation and Discrete Fourier Transform (DFT) based channel estimation. The effect of choosing an appropriate generator will be discussed as well as the effect of channel interleaver on the system in these two different channel estimation. The simulation result shows better error performance in the system using UWB channel interleaver compare to random interleaver using DFT based channel estimation.

PAPR Reduction Techniques in Generalized Inverse Discrete Fourier Transform Non-Orthogonal Frequency Division Multiplexing System

With the rapid growth of communications via the Internet, the need for an effective firewall system which has not badly affect the overall network performances has been increased. In this paper, a Field Programmable Gate Array (FPGA) -based firewall system with high performance has been implemented using Network FPGA (NetFPGA) with Xilinx Kintex-7 XC7K325T FPGA. Based on NetFPGA reference router project, a NetFPGA-based firewall system was implemented. The hardware module performs rule matching operation using content addressable memory (CAM) for higher speed data processing. To evaluate system performance, throughput, latency, and memory utilization were measured for different cases using different tools, also the number of rules that an incoming packet is subjected to was varied to get more readings using both software and hardware features. The results showed that the designed firewall system provides better performance than traditional firewalls. System throughput was doubled times of the one with Linux-Iptables firewalls.

Joint clipping and amplifying techniques for PAPR reduction in OFDM systems

Multicarrier system such as orthogonal frequency division multiplexing (OFDM) are significantly affected by peak-to-average-power ratio (PAPR). Many researchers introduce different techniques to reduce PAPR with tradeoffs of data rate loss and computations of approach. In some cases, the techniques of reduction may lead to increase average power of transmitted signal and degrades the BER performance at the receiver. Hence, proper design of PAPR reduction technique needs to be considered. In this paper, a combination of Clipping Peak and Amplifying Bottom (CPAB) is proposed. The peak of signal is clipped at a threshold A, while the bottom values of signal are amplified to threshold B. The clipping technique was widely accepted method to improve the PAPR statistics. Therefore, joint clipping with amplifying in CPAB will develop PAPR reduction. In addition, PAPR value depends on clipping and amplifying thresholds. The result shows that the clipping factor affected the complementary cumulative distribution function (CCDF) performance more than the amplifying factor in CPAB technique. Thus, by properly select the threshold of A and B, better OFDM system performance is achieved with lower PAPR.

Low complexity technique exploiting 2D source correlation using single parity check codes

This paper proposes a low complexity joint source-channel coding (JSCC) technique that can well exploit two-dimensional (2D) source correlation using turbo single parity check (SPC) codes. Based on similar structure of the product accumulate code, a rate-1 inner code is serially concatenated to the turbo SPC code structure in order to overcome the high error floor issue of turbo SPC codes. The 2D source correlation, horizontal and vertical directions of the source are exploited during the decoding process. In order to exploit the source statistics (i.e. transition probabilities), a decoding algorithm based on modified check operation is proposed. This modified check operation has significantly lower computational complexity than the previous technique that based on modified Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm. Simulation results reveal that the proposed technique that based on modified check operation achieves about 4.5 times lower computational complexity than the technique that based on modified BCJR algorithm. In addition to the lower computational complexity, the proposed JSCC technique can achieve optimal performance, similar with the technique that based on modified BCJR algorithm. The interesting features of low computational complexity and high performance of the proposed technique is important in designing JSCC system exploiting higher dimensional source correlation.