Showing papers by "S. M. Riazul Islam published in 2010"

Energy Saving Mechanisms for MAC Protocols in Wireless Sensor Networks

Abstract: Energy efficiency is a primary requirement in a wireless sensor network (WSN). This is a major design parameter in medium access control (MAC) protocols for WSN due to limited resources in sensor nodes that include low battery power. Hence a proposed MAC protocol must be energy efficient by reducing the potential energy wastes. Developing such a MAC protocol has been a hot research area in WSN. To avoid wasting the limited energy, various energy saving mechanisms are proposed for MAC protocols. These mechanisms have a common design objective—to save energy to maximize the network lifetime. This paper presents a survey on various energy saving mechanisms that are proposed for MAC protocols in WSN. We present a detailed discussion of these mechanisms and discuss their strengths and weaknesses. We also discuss MAC protocols that use these energy saving mechanisms.

A Study of Medium Access Control Protocols for Wireless Body Area Networks

Abstract: The seamless integration of low-power, miniaturised, invasive/non-invasive lightweight sensor nodes have contributed to the development of a proactive and unobtrusive Wireless Body Area Network (WBAN). A WBAN provides long-term health monitoring of a patient without any constraint on his/her normal dailylife activities. This monitoring requires low-power operation of invasive/non-invasive sensor nodes. In other words, a power-efficient Medium Access Control (MAC) protocol is required to satisfy the stringent WBAN requirements including low-power consumption. In this paper, we first outline the WBAN requirements that are important for the design of a low-power MAC protocol. Then we study low-power MAC protocols proposed/investigated for WBAN with emphasis on their strengths and weaknesses. We also review different power-efficient mechanisms for WBAN. In addition, useful suggestions are given to help the MAC designers to develop a low-power MAC protocol that will satisfy the stringent WBAN requirements.

On Channel Estimation in MB-OFDM UWB Systems with Time Varying Dispersive Fading Channel

Abstract: New channel estimation technique is proposed for multiband orthogonal frequecny division multiplexing (MB-OFDM) ultra wideband (UWB) systems in multipath time varying wireless channels. Two-stages approch has been used to achieve this purpose. In first stage, Winner-Hopf filtration has been employed for the interpolation of unknown channel state information (CSI) using comb-type known pilots. In second stage, interpolated channel statistics are then modeled as autoregressive (AR) process and fed into kalman filter. Moreover, inorder to suppress intercarrier interference (ICI), an ICI mitigation filter does joinly work with kalman filter. A mathematical framework is given for the ralization of our proposed system. Link level simulation (LLS) urgs that this new tecnique shows exact channel tarcking and provides better symbol error rate (SER) performance.

Winner-hopf interpolation aided kalman filter-based channel estimation for MB-OFDM UWB systems in time varying dispersive fading channel

Abstract: New channel estimation technique is proposed for multiband orthogonal frequecny division multiplexing (MBOFDM) ultra wideband (UWB) systems in multipath time varying wireless channels. Two-stage approch has been used to achieve this purpose. In first stage, Winner-Hopf filtration has been employed for the interpolation of unknown channel state information (CSI) using comb-type known pilots. In second stage, interpolated channel statistics are then modeled as autoregressive (AR) process and fed into kalman filter. Moreover, inorder to suppress intercarrier interference (ICI), an ICI mitigation filter does joinly work with kalman filter. A mathematical framework is given for the ralization of our proposed system. Link level simulation (LLS) urgs that this new tecnique shows exact channel tarcking and provides better symbol error rate (SER) performance.

A Study of Medium Access Control Protocols for Wireless Body Area Networks

Abstract: The seamless integration of low-power, miniaturised, invasive/non-invasive lightweight sensor nodes have contributed to the development of a proactive and unobtrusive Wireless Body Area Network (WBAN). A WBAN provides long-term health monitoring of a patient without any constraint on his/her normal dailylife activities. This monitoring requires low-power operation of invasive/non-invasive sensor nodes. In other words, a power-efficient Medium Access Control (MAC) protocol is required to satisfy the stringent WBAN requirements including low-power consumption. In this paper, we first outline the WBAN requirements that are important for the design of a low-power MAC protocol. Then we study low-power MAC protocols proposed/investigated for WBAN with emphasis on their strengths and weaknesses. We also review different power-efficient mechanisms for WBAN. In addition, useful suggestions are given to help the MAC designers to develop a low-power MAC protocol that will satisfy the stringent WBAN requirements.

Energy-efficient channel estimation for MB-OFDM UWB system in presence of interferences

Abstract: Interference reduces the performance of a correct data signal detection and decoding. This problem becomes severe when interferences exist during the period of channel estimation. This will destroy the accuracy of channel estimation and, will eventually result severe degradation in the performance of signal detection and decoding in the entire data packet/frame. In this article, we propose an improved channel estimation technique for multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) system in presence of interferences. In particular, we work towards a preamble-based channel estimation technique in multi-access and narrowband interfering environments. We construct two preamble symbols with opposite, both in amplitude and phase, sequences in frequency-domain. Time-domain redundancy is introduced into these preamble symbols before transmission. Based on this time-domain redundancy property, we eliminate multi-access interference (MAI) through an adaptive select and replace (ASR) scheme. We show that the use of opposite sequences in preambles leads a simple addition, subtraction and compare (ASC) scheme to cancel narrowband interference (NBI). In addition, we apply a frequency-domain filter, driven by channel's power delay profile (PDP), to get a further enhancement in the estimation accuracy. Simulation results urge that our proposed technique outperforms the conventional channel estimation methods.

Joint Channel Estimation and Interference Suppressions for MB-OFDM UWB Systems

Abstract: New channel estimation technique is proposed for multiband orthogonal frequecny division multiplexing (MB-OFDM) ultra-wideband (UWB) systems. Several steps have been carried out to achieve this purpose. In first step, refined least square (LS) channel estimation is found out by using subspace-based narrowband interference (NBI) estimation method with prilimonary LS channel. In second step, low rank least square minimum mean squared error (LMMSE) channel estimation is performed using this refined LS channel estimation. Finally, Blackman windowing is applied on low rank LMMSE channel to reduce the spectral leakage and hence to increase the channel estimation accuracy. Before starting the actual channel estimation, an ICI mitigation filter is used to minimize the reduction of signal-to-interference ratio (SIR) due to imperfect frequency synchronization. Link level simulation (LLS) urges that our proposed technique has improved performance.

Minimum mean square error-ordered successive interference cancellation (MMSEOSIC) in UWB-MIMO systems

Abstract: Developing of low complex and high performance detection algorithms are challenging. In this paper, we introduce the ordered successive interference cancellation (OSIC) scheme with MMSE in UWB-MIMO system. Especially we use MMSE, OSIC, RAKE combination to evaluate the performance of UWB-MIMO system in multipath environment. We compare the performance result based on the number of multipath and number of antennas.

Energy-efficient channel estimation for multiband UWB systems in presence of interferences

Abstract: Interference reduces the performance of a correct data signal detection and decoding. This problem becomes severe when interferences exist during the period of channel estimation. This will destroy the accuracy of channel estimation, and will eventually result to severe degradation in the performance of signal detection and decoding in the entire data packet/frame. In this article, we propose an improved channel estimation technique for multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) system in presence of interferences. In particular, we work towards a preamble-based channel estimation technique in multi-access and narrowband interfering environments. We construct two preamble symbols with opposite, both in amplitude and phase, sequences in frequency-domain. Time-domain redundancy is introduced into these preamble symbols before transmission. Based on this time-domain redundancy property, we eliminate multi-access interference (MAI) through an adaptive select and replace (ASR) scheme. We show that the use of opposite sequences in preambles leads a simple addition, subtraction and compare (ASC) scheme to cancel narrowband interference (NBI). In addition, we apply a frequency-domain filter, driven by channel’s power delay profile (PDP), to get a further enhancement in the estimation accuracy. Simulation results urge that our proposed technique outperforms the conventional channel estimation methods. Key words: Ultra-wideband, channel estimation, channel impulse response (CIR), multiband orthogonal frequency division multiplexing, wireless personal area network (WPAN), narrowband interference, multi-access interference, and ECMA-368.