Bikramaditya Das

Interference Cancellation Schemes in UWB Systems Used in Wireless Personal Area Network based on Wavelet based Pulse Spectral shaping and Transmitted Reference UWB using AWGN Channel Model

For high data rate ultra wideband communication system, performance study of mutual interference such as suppression of interference signal by performing pulse shaping from UWB to other narrowband system using wavelet technique and reduction of interference from other narrowband system to UWB system in conjunction with Transmitted-Reference (TR-UWB) signaling scheme with adaptive receivers is attempted in this paper. The TRUWB signal using wavelet is based on multi-resolution technique to avoid its interference to other wireless systems. Ultra Wideband (UWB) wireless systems supposed to coexist with other spectrally overlapping wireless systems such as narrowband interference (NBI), multiple NBI and wideband interference allocated from 3.1GHz to 10.6GHz. So suppression of UWB from other system can be performed by using Eigen value decomposition using wavelet technique. Mutual interference degrades the performance of the TRUWB system using auto-correlation receivers (AcR). In this paper adaptive receiver (using notch filter) is used for detection and suppression of mutual interference (narrowband and wideband signal) which do not require modification of the narrowband system. The bit error rate performances are investigated using MATLAB simulation under AWGN channel model. At 10-2 BER floor, TRUWB using adaptive receiver with NBI simulations under AWGN provides a more than of 6 dB SNR improvement than that of TR using AcR receiver with NBI. The performance degrades when coexistence of multiple NBI and wideband interference wireless system with UWB system is applied using the same receiver. KeywordsTR-UWB, AWGN Channel Model, NBI, multiple NBI , wideband interference ,Bit Error Rate .

Efficacy of Multiband OFDM Approach in High Data Rate Ultra WideBand WPAN Physical Layer Standard using Realistic Channel Models

Multiband Orthogonal Frequency Division Multiplexing (MBOFDM) approach using UWB signals with short duration of pulses provide unique advantages in short-range high data rate wireless applications which include easy penetration through obstacles, high precision ranging and low processing power. In this paper a performance study on MB-OFDM is attempted for high data rate ultra wideband (UWB) WPAN physical layer standard according to modulation techniques such as QPSK, 16-QAM, 64-QAM etc. Different multipath components in the UWB channels are characterized by different delays and attenuation. The channel models chosen in simulation of MB-OFDM UWB communication system are different from standard UWB channels considering realistic multipath resolution and operating frequencies. In this research different amplitude fading statistics for UWB channel (IEEE 802.15.3a) are analysed. The BER performance of MB-OFDM UWB on modified UWB channel models are investigated through simulation study. It is observed that QPSK modulation for the MB-OFDM UWB system performs better than 16-QAM and 64-QAM in the CM3 (NLOS) and CM4 (NLOS) channel environment. We show that, at low data rate (55 Mbps) the MB-OFDM system performs better in the CM4 channel environment than in the CM3, CM2 and CM1 channel model due to its inherent frequency diversity. In high data rate (480 Mbps), the BER performance in CM1 channel model is found to be better than in CM2, CM3, CM4 channel model.

Performance Study of Discrete Wavelet Packet Based MB-OFDM System for Short Range Indoor Wireless Environment

Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) approach using UWB signals with short duration of pulses provide unique advantages in short-range high data rate wireless applications which include easy penetration through obstacles, high precision ranging and low processing power. A perfect reconstruction using discrete wavelet packet transmultiplexer in MB-OFDM transceiver counters the degrading effect of ISI, and also conserves bandwidth. In comparison to conventional FFT MB-OFDM, Discrete Wavelet Packet Modulation (DWPM) offers much lower side lobes in the transmitted signal, which reduces inter carrier interference (ICI) and narrowband interference (NBI). In this paper a detail study on conventional MB-OFDM and Discrete Wavelet Packet Transform (DWPT) MB-OFDM is attempted for high data rate ultra wideband (UWB) WPAN physical layer standard. Different multipath components in the UWB channels are characterized by different delays and attenuation. BER performances of MB-OFDM UWB on IEEE 802.15.3a channel models are investigated through simulation study. We show that, at low data rate (55 Mbps) the DWPT MB-OFDM system performs better in the CM4 channel environment than in the CM3 channel due to its inherent frequency diversity. In high data rate (480 Mbps), the BER performance in CM3 channel model is found to be better than in CM4 channel model. DWPT MB-OFDM outperforms than the conventional FFT MB-OFDM for high data rate applications.

Co-operative control of a team of autonomous underwater vehicles in an obstacle-rich environment

ABSTRACT This paper presents the cooperative control of a team of autonomous underwater vehicles (AUVs) in the presence of obstacles under environmental disturbance. A leader–follower formation control based on optimisation algorithms using communication topology is designed to navigate towards the target in the presence of obstacles. CLONAL selection optimisation algorithm may be employed as team controller by providing the optimal position to hierarchical control strategy for each AUV incorporating learning, memory and affinity. But unfortunately CLONAL selection optimisation algorithm fails to avoid obstacles because some of the lymphocytes become memory cells of the system. The above prematurity may be overcome by using artificial potential fields and ant colony optimisation technique combined with CLONAL selection optimisation algorithm. The efficacy of the proposed optimisation is verified through MATLAB simulation and the result confirmed the robustness and proficiency of proposed technique over CLONAL selection optimisation algorithm.

Interference mitigation techniques in transmitted reference UWB system used in WPANs NLOS channel environment

In this paper, studies are performed and techniques are proposed for interference mitigation in Transmitted Reference ultra wideband (TR-UWB) system. The best method for suppressing and reducing the mutual interference is without modifying interfering systems. The coexistence of multisystem is given by: (a) Interference reduction from UWB systems to other narrowband (single and multiple) and wideband systems. (b) Interference reduction from other narrowband (single and multiple) and wideband systems to UWB systems. The TR-UWB signal using AcR based multi-resolution technique is used to avoid its interference to other wireless systems. By using a notch filter the reverse interference is alleviated at frontend of UWB receiver which is having much smaller bandwidth as Gaussian pulse-shaped multi-resolution environment. The BER performance of AcR receiver and modified TR-UWB receiver are investigated on AWGN and IEEE 802.15.3a UWB channel models. We show that for a modified TR-UWB receiver operating at low to medium SNRs, the system performance increases as the single NBI are perfectly suppressed, while at high SNRs the system still performs satisfactorily in presence of multiple narrowband and wideband interference using modified receiver structure in NLOS channel environment.

Time Domain Equalization Technique Using RAKE-MMSE Receivers for High Data Rate UWB Communication System

For high data rate ultra wideband communication system, performance study rake-mmse time domain equalization (both LE and DFE) is attempted in these paper. We focus our attention on the effects of the number of Rake fingers and equalizer taps on the error performance. The proposed receiver combats inter-symbol interference by taking advantage of the Rake and equalizer structure. The receiver performance is investigated using a semi analytical approach and Monte-Carlo simulation on IEEE 802.15.3a UWB channel models. We show that for a MMSE equalizer operating at low to medium SNR’s, the number of Rake fingers is the dominant factor to improve system performance, while at high SNR’s the number of equalizer taps plays a more significant role in reducing error rates.

RAKE-MMSE Time Domain Equalizer for High Data Rate UWB Communication System

Study on RAKE-MMSE time domain equalizers are attempted for high data rate ultra wideband communication system. We have taken into account of impact of all the parameters such as the effect of the number of Rake fingers and equalizer taps on the error performance. The proposed receiver combats inter-symbol interference by taking advantage of the Rake and equalizer structure. A semi analytical approach and Monte-Carlo simulation are used to investigate the BER performance of RAKE-MMSEreceiver on IEEE 802.15.3a UWB channel models. We show that for a MMSE equalizer operating at low to medium SNR’s, the number of Rake fingers is the dominant factor to improve system performance, while at high SNR’s the number of equalizer taps plays a more significant role in reducing error rates.

Performance evaluation of MB-OFDM UWB WPAN system based on channel estimation technique using realistic channel models

Under the condition of indoor short-range wireless transmission, the UWB systems can provide very high data rate whereas the power consumption is very low, which makes it a promising candidate for wireless personal area networks (WPAN) where the data rate is greater than 110Mbps and the range is shorter than 10 meters in general. Moreover, UWB is also introduced into the underlying transport mechanism of wireless USB and wireless 1394 for even higher throughput up to 480Mbps within 2 meters [1]. The UWB systems based on MB-OFDM divide the whole assigned spectrum into several smaller sub-bands and each sub-band into a few subcarriers to transmit the information, which leads to lower design complexity as well as better spectral efficiency and fl exibility than the DS-UWB systems [1–3].

Performance Analysis of Ultra Wideband Receivers for High Data Rate Wireless Personal Area Network System

For high data rate ultra wideband communication system, performance comparison of Rake, MMSE and Rake-MMSE receivers is attempted in this paper. Further a detail study on Rake-MMSE time domain equalizers is carried out taking into account all the important parameters such as the effect of the number of Rake fingers and equalizer taps on the error rate performance. This receiver combats inter-symbol interference by taking advantages of both the Rake and equalizer structure. The bit error rate performances are investigated using MATLAB simulation on IEEE 802.15.3a defined UWB channel models. Simulation results show that the bit error rate probability of Rake-MMSE receiver is much better than Rake receiver and MMSE equalizer. Study on non-line of sight indoor channel models illustrates that bit error rate performance of Rake-MMSE (both LE and DFE) improves for CM3 model with smaller spread compared to CM4 channel model. It is indicated that for a MMSE equalizer operating at low to medium SNR values, the number of Rake fingers is the dominant factor to improve system performance, while at high SNR values the number of equalizer taps plays a more significant role in reducing the error rate.

A Comparison Study of Receiver Performances on Ultrawide Band Indoor Wireless Channel Model

For high data rate ultra wideband communication system, performance comparison of Rake, MMSE and Rake-MMSE receivers is attempted in this paper. The effect of the number of Rake fingers and equalizer taps on the error performance by combating ISI are the major focus of our research. The bit error rate performances are investigated using semi analytical approach and Monte-Carlo simulation on IEEE 802.15.3a UWB channel models. Simulation results show that the bit error rate probability of rake-mmse receiver is better than individual Rake and MMSE receiver. The simulation results are illustrated using non-line of sight indoor wireless channel model (CM3 and CM4). It was observed that RAKE-MMSE receiver structure gives superior performance in CM3 channel model with small delay spread compared to CM4 channel model.