Mohd Fadzli Mohd Salleh

Wavelet-based OFDM analysis: BER performance and PAPR profile for various wavelets

This paper presents the analysis of BER and PAPR performance of Wavelet-based OFDM (WOFDM) using different wavelets. We do intensive study on several wavelets from different wavelet families to find out the BER performance and PAPR characteristic of WOFDM system using Haar, Daubechies, Symlet, Coiflet and Discrete Meyer wavelets. Simulation results for the selected wavelets show improvement of 3 dB gain Eb/N0 at the BER of 10-4, and significant PAPR reduction as compared to the conventional OFDM.

Efficient Hardware-Based Image Compression Schemes for Wireless Sensor Networks: A Survey

Multidimensional sensors, such as digital camera sensors in the visual sensor networks VSNs generate a huge amount of information compared with the scalar sensors in the wireless sensor networks WSNs. Processing and transmitting such data from low power sensor nodes is a challenging issue through their limited computational and restricted bandwidth requirements in a hardware constrained environment. Source coding can be used to reduce the size of vision data collected by the sensor nodes before sending it to its destination. With image compression, a more efficient method of processing and transmission can be obtained by removing the redundant information from the captured image raw data. In this paper, a survey of the main types of the conventional state of the art image compression standards such as JPEG and JPEG2000 is provided. A literature review of their advantages and shortcomings of the application of these algorithms in the VSN hardware environment is specified. Moreover, the main factors influencing the design of compression algorithms in the context of VSN are presented. The selected compression algorithm may have some hardware-oriented properties such as; simplicity in coding, low memory need, low computational load, and high-compression rate. In this survey paper, an energy efficient hardware based image compression is highly requested to counter the severe hardware constraints in the WSNs.

Multiple Descriptions Coinciding Lattice Vector Quantizer for Wavelet Image Coding

Multiple description (MD) coding has been a popular choice for robust data transmission over the unreliable network channels. Lattice vector quantization provides lower computation for efficient data compression. In this paper, a new MD coinciding lattice vector quantizer (MDCLVQ) is presented. The design of the quantizer is based on coinciding 2-D hexagonal sublattices. The coinciding sublattices are geometrically similar sublattices, with the same index but generated by different generator matrices. A novel labeling algorithm based on the hexagonal coinciding sublattices is also developed. Performance results of the MDCLVQ scheme, together with the new labeling algorithm applied to standard test images, show improvements of the central and side decoders, as compared with the renowned techniques for several test images.

Reduced complexity optimum detector for Block Data Transmission Systems

Block Data Transmission Systems (BDTS) are used in high-speed wireless communication systems with time dispersive channel characteristics. In such systems, blocks of data are separated by zeros to mitigate the effect of Inter-Symbol-Interference (ISI) between the blocks. An optimal detection process employs the Maximum Likelihood Block Detection (MLBD) technique on each block individually in the presence of ISI and Gaussian noise based on the Euclidean distance as an objective function. The detection process is computationally expensive therefore Genetic Algorithms have been used to reduce the overall design complexity. In this work, three types of Genetic Algorithms have been incorporated in the detection process i.e. the conventional GA, Micro GA(µGA), and Hybrid µGA to reduce computational load. In particular, a novel training method for Hybrid µGA has been proposed. Simulation results at 10dB channel SNR for the BDTS with Hybrid µGA executes as low as 3,750 number of objective functions evaluation for a block size of 20. The Bit Error Rate (BER) performance of this system is relatively good i.e. around 1dB inferior to the BDTS using the Exhaustive Search method that requires as many as 220 number of objective functions evaluation.

Reduced complexity optimum detector for block data transmission systems using Lattice Sphere Decoding technique

The complexity of the exhaustive search decoding technique such as Maximum Likelihood Block Detection (MLBD) grows exponentially with the size of transmitted data. In this paper, a Lattice Sphere Decoding (LSD) technique is proposed for detection in block data transmission systems (BDTS). Simulation results at 10dB channel SNR of BDTS with LSD using block size of 20 performs are near Hybrid Micro Genetic Algorithm (HMGA) and slightly inferior than the exhaustive search technique using the channels with spectral nulls. In term of complexity, the proposed LSD technique requires only 460 and 126 objective functions evaluation using radius selection based on Babai Estimation (BE) and off-line observation respectively, while the HMGA and exhaustive search requires 3750 and 220 objective functions evaluation respectively.

Outage probability of coded cooperation for slow fading channel

This letter presents the outage probability of the Reed Solomon (RS) coded cooperation scheme. In this scheme, the codeword of the Users are partitioned into two frames and transmitted through two independent fading channels. The first frame is transmitted directly to the base station. The second frame is transmitted via a partner to the base station. The derived outage expressions confirm that full diversity is achieved by the RS coded cooperation scheme. The analytical outage probability comparisons under various inter-user and uplink channel conditions shed light on the relative virtues of the RS coded cooperation scheme as compared to the RCPC coded cooperation scheme with around 1.5 to 2.5dB gains.

Performance analysis of QAM-modulation parameters on wavelet packet transform (WPT) and FFT-OFDM system

In Orthogonal Frequency Division Multiplexing (OFDM) a cyclic prefix (CP) is appended to each symbol in order to mitigate the effect of Inter-Symbol-Interference (ISI). However this leads to spectral inefficiency. A perfect reconstruction using wavelet packet transmultiplexer in OFDM transceiver counters the degrading effect of ISI, and also conserves bandwidth. In this paper the BER performance comparison between the OFDM systems that utilise the conventional Discrete Fourier Transform (DFT) and Discrete Wavelet Packet Transform (DWPT) respectively is analyzed. The analysis is done for various number of modulation QAM constellation points (8 to 64), and simulated over AWGN channel. Simulation results show that the best BER performance exhibits by the WPT-OFDM system, when the number of modulation QAM is 8.

Multiple description lattice vector quantization using multiple A4 quantizers

This paper presents a new Multiple Description Lattice Vector Quantization (MDLVQ) based on A4 lattice quantizers for multiple description coding abbreviated as MDLVQ-A4. The Coinciding similar A4 sublattices are used to quantize the input stream for multiple description coding system. The use of multiple coinciding quantizers eliminates the labeling function of the traditional schemes. Experimental results of MDLVQ-A4 scheme for image coding show a higher performance in terms of PSNR of the side decoders as compared to the renowned techniques of image coding for several test images.

Lattice Sphere Decoding for Data Transmission Systems with Special Channel Matrices

This paper presents the effects of condition number (