Sobia Baig

Performance Comparison of DFT, Discrete Wavelet Packet and Wavelet Transforms, in an OFDM Transceiver for Multipath Fading Channel

Multi-carrier modulation (MCM) schemes divide the broadband frequency-selective channel into parallel, flat-fading subchannels of equal bandwidth and interspacing. A cyclic prefix is appended to each symbol, in order to mitigate inter-symbol interference (ISI), however it leads to spectral inefficiency. Moreover, OFDM transceivers suffer from poor frequency characteristics. Perfect reconstruction wavelet packet transmultiplexer in an OFDM transceiver counters the degrading effects of ISI, and also conserves bandwidth. In this paper we give the performance comparison of conventional discrete Fourier transform (DFT) with discrete wavelet packet transform (DWPT) in an OFDM transceiver. Two of the most popular wavelets, namely Haar and Daubechies wavelets are used for DWPT in a multipath flat-fading and frequency selective-fading channel. A comparison between wavelets and wavelet packets is also given and it is shown that wavelet packets outperform wavelets

A discrete multitone transceiver at the heart of the PHY layer of an in-home power line communication local-area network

A networked home is a micro-version of the Internet, connecting home appliances, PCs, and other smart devices not only to one another but also to a globally connected world through the Internet. For consumers to embrace home networking, a solution that utilizes the existing infrastructure within the home, such as electrical wiring, is significant. However, the use of power lines as a home networking platform presents quite a troublesome and noisy environment that fluctuates with varying load impedance and time, and is also plagued by impulse noise. The latest developments in VLSI and DSP technologies have enabled power line communication (PLC) networks to compensate for the impairments of the environment. This article discusses the use of discrete multitone technology at the PHY layer of an in-home PLC network, particularly with reference to bit-loading techniques.

Performance Comparison of DFT-OFDM and Wavelet-OFDM with Zero-Forcing Equalizer for FIR Channel Equalization

In conventional DFT based orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP) is used to avoid the inter symbol interference (ISI) caused by a time dispersive channel. A solution has been proposed in literature, which involves replacing DFT with wavelet packet transform (WPT) in communication systems. WPT does not require CP and has the attraction of having much lower side lobes. However, in wavelet based multicarrier systems, channel equalization remains an open research area. In this article, a time-domain zero-forcing equalizer (ZFE) for wavelet packet based OFDM (WOFDM) is proposed. The performance comparison of DFT-OFDM and WOFDM is given for an arbitrary FIR channel with different types of wavelet packets. Simulation results show improvement in bit error rate (BER) performance for WOFDM.

Multirate signal processing techniques for high-speed communication over power lines

With the widespread use of Internet and multimedia applications, there is renewed interest in utilizing the electric power lines for transmission of high data rate communication signals. Power lines offer a convenient and pervasive communication medium that does not require new cable installation. However, power lines are classified as a noisy and unpredictable communication channel. Advanced signal processing techniques, such as wavelet filter banks and multirate systems, can be utilized to improve the quality of communication over power lines. In this article an overview of the diverse applications of wavelet filter banks in power line communications is presented with particular reference to wavelet-based multicarrier modulation techniques. Moreover, some suggestions are given regarding the future applications of multirate signal processing techniques in PLC.

Performance comparison of Wavelet Packet Modulation and OFDM for multipath wireless channel

In comparison to Orthogonal Frequency Division Multiplexing (OFDM), Wavelet Packet Modulation (WPM) offers much lower side lobes in transmitted signal, which reduces inter-carrier interference (ICI) and narrowband interference (NBI). It is also spectrally efficient since it does not utilize cyclic prefix (CP), nevertheless, it requires an efficient equalization technique to counter the inter symbol interference (ISI) and ICI created by the channel. In this paper, performance comparison of OFDM and WPM for several multipath wireless channels is presented. We propose a novel application of zero-forcing (ZF) and minimum mean square error (MMSE) algorithms as time-domain channel equalization techniques for WPM systems. It is shown that, for a multipath wireless channel, WPM using MMSE-equalizer has a better bit error rate (BER) performance as compared to ZF-equalizer in WPM, as well as OFDM system.

Modified incremental bit allocation algorithm for PowerLine communication in Smart Grids

Smart Grids (SG) may be the most significant technological change in the history of electric grids, that can help curb the looming energy crisis worldwide, with intelligent generation, transmission and distribution of energy using a robust communication network. Power lines are a very promising solution for carrying data to serve as broadband access network in the context of SG, along with the wireless communication techniques. This paper investigates the design and simulation of a digital communication system optimized for Power Line Communication (PLC) in Smart Grids. For the proposed PLC transceiver, we consider Discrete Multitone (DMT) modulation based on a modified bit loading technique for the subcarriers. Our results reveal that the proposed incremental bit loading algorithm enhances data rate, and reduces computation time, as compared to the originally proposed incremental bit loading algorithm for PLC.

Wavelet OFDM-A solution for reliable communication in a frequency selective Rayleigh fading channel

Wavelet transform based modulation techniques have been recently proposed in literature, with the motivation of offering more robustness, interference suppression, and providing greater bandwidth efficiency, compared to the Fourier transform based conventional modulation techniques. Wavelet Packet based Orthogonal Frequency Division Multiplexing (WOFDM) technique is a multicarrier modulation technique that has been compared to the conventional OFDM technique in various channel and noise conditions. This paper analyses the performance of WOFDM in a Rayleigh fading wireless communication channel, taking into consideration the Doppler shift in the presence of additive white Gaussian noise. It is shown through bit error rate performance that WOFDM system outperforms the conventional OFDM system with various Doppler shifts, and with interleaving and channel coding the system performance is further enhanced.

A Frequency Domain Equalizer in Discrete Wavelet Packet Multitone Transceiver for In-Home PLC Lans

Reliable and high speed communication over power-lines requires a robust modulation scheme, such as discrete multitone (DMT). A novel transceiver based on the discrete wavelet multitone (DWMT) modulation technique is proposed, in order to improve the data communication over the noisy in-home PLC network. DWMT transceiver utilizes discrete wavelet packet transform (DWPT) for basis functions. A frequency domain equalizer for the DWMT transceiver employing cyclic prefix, is also suggested. The time and frequency localization property of the wavelet packet transform helps mitigate narrowband and heavy impulse noise in the PLC channel, and gives improved performance over its conventional counterpart, the DMT transceiver.

Performance Analysis of a Non-Uniform DMT Transceiver in Digital Subscriber Line

A Non‐Uniform Discrete Multitone (DMT) transceiver employing an octave spaced quadrature mirror filter (QMF) bank, can be used to overcome the problem of channel noise enhancement in the zero‐ forcing (ZF) equalization technique. In this letter, performance of the Non‐Uniform DMT system is analyzed. A study of the crosstalk between sub‐channels due to non‐ideal filter banks is also presented. Crosstalk analysis is based upon the bit error rate (BER) performance versus the QMF order in a standadard ADSL channel. Performance comparison of the Non‐Uniform DMT transceiver and a conventional DMT system is given, and it is shown that the Non‐Uniform DMT transceiver displays slight improvement over the conventional DMT system for the filters of higher order.

Channel modeling of NB-PLC for Smart Grid

Future electricity power network must be restructured to improve its efficiency in order to provide all the consumers with flexible, cost effective, reliable and accessible power delivery. Recent research focuses on the conversion of typical power grid to Smart Grid (SG) where energy generation is decentralized. In this regard Power Line Communications (PLC) is a vital part of Information and Communication Technologies (ICT) within the SG. This paper presents the analysis and modeling of different channels i.e., Low Voltage (LV), Medium Voltage (MV) and High Voltage (HV) transmission lines for Narrowband Power Line Communications (NB-PLC) using transmission line theory. Most of the literature regarding power line channel modeling deals with the statistical approaches which are relatively inaccurate as they provide a partial analysis of power line channel models which includes solely multipath effects. A comprehensive investigation has been carried out by evaluating and comparing the behaviors of LV, MV and HV channel models. A consequence for the validity of this research is to facilitate the International standardization process of various power line transfer functions especially in Asian countries where a lot more research is needed in the area of power line communications. Moreover characteristics of constant and frequency selective impedances of various channel models have been evaluated.