The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
This paper analyzes the design and performance of hybrid automatic repeat request (HARQ) extensions to the multi- band orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) standard. It is shown how both Type-I and Type-III HARQ can significantly reduce the packet error rate (PER) in realistic frequency-selective channels. An exhaustive search is used to find an optimal low-complexity...
This paper investigates inter-piconet interference (IPI) in the multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) standard. IPI is caused when the time-frequency codes (TFCs) that delineate MB-OFDM piconets collide. An upper-bound on the severity of the IPI problem is obtained through a theoretical analysis of data-rate-speciflc punctured convolutional codes. Using...
This paper presents a study into different angles for the new spread matrix developed for BSOFDM. It varies the angles for the matrix to develop different constellation schemes which are useful in overcoming the frequency selective channels which are encountered in mobile communication systems. Previously it has been discussed that this new matrix (the rotation matrix) has some advantages over Hadamard...
This paper presents a new spreading matrix for block spread OFDM (BSOFDM) to improve the performance of the system by increasing the correlation between the symbols. This is achieved by rotating the modulation scheme used at the transmission, say QPSK, into a higher order modulation scheme, for example 16QAM. By this the correlation between the transmitted symbols is increased. The advantage of this...
A zero-pad can be used with orthogonal frequency division multiplexing (OFDM) for low-complexity robustness against multipath interference. In this paper, we use adaptive overlap-add (OLA) equalization for improvements of up to 1 dB when used with multi-band OFDM (MB-OFDM) ultra-wideband. A theoretical model that relates the size of OLA window to post-equalizer signal-to-noise ratio is derived. An...
In this paper we present extremely low-complexity adaptive infinite impulse response (IIR) filters that approximate minimum mean square error (MMSE) channel estimation in orthogonal frequency-division multiplexing (OFDM) systems. We show how the packet error rate (PER) can be significantly improved over conventional zero-forcing (ZF) estimation without incurring a significant increase in computational...
In this paper, we design complementary codesets that significantly improve the quality of channel estimation in orthogonal frequency division multiplexing (OFDM) communication systems, with a focus on the recent MB-OFDM ultra-wideband (UWB) standard. The proposed time-domain OFDM channel estimation technique incurs only a nominal increase in computational complexity and is able to be readily retrofitted...
The effect of direct current (DC) offset on orthogonal frequency division multiplexing (OFDM) system with zero-padded (ZP) suffix is analysed in this paper. It is found that the ZP appended OFDM system suffers more from DC offset than a cyclic prefix inserted OFDM system and even demonstrates bit error flooring if the DC power exceeds a maximum allowed threshold. Simple algorithms are also proposed...
A method for spectrum spreading in an orthogonal frequency division multiplexing (OFDM) system is proposed in this paper, resulting in a spread spectrum OFDM (SS-OFDM) system suitable for ultra-wideband (UWB) applications. By modifying the IFFT module in a conventional OFDM transmitter and interleaving the modulated signal samples within an OFDM symbol, the transmitted signal spectrum is spread greatly...
This paper presents extremely low-complexity boolean logic for the generation of coefficients suitable for filtering or correlation of scalable complete complementary sets of sequences (SCCSS). As the unique auto- and cross-correlation properties of SCCSS are of broad interest, the simplicity of the proposed coefficient generation technique allows arbitrarily long SCCSS to be used in resource constrained...
Wireless sensor networks have received a lot of attention in recent years both in the research community and in standards organizations. The emphasis of most sensor network research activities has been on the development of low cost and low power technologies for low bit rate applications. In this paper, we describe our work on ultra-wideband (UWB) sensor network technology targeted for video surveillance...
For pt.1 see ibid., p.2444-8 (2006).This second part of the paper presents the system design and performance simulation results of a novel ultra-wideband (UWB) system developed for low power, long range, mid to high data rate mesh networking applications. Firstly, the transceiver architecture is described, and the system parameters are selected and justified. Then, the physical layer (PHY) protocol...
This paper demonstrates and compares the complementary properties of two types of Hadamard matrices, i.e., the Walsh-Hadamard matrix and the Golay-paired Hadamard matrix. A simple process is also proposed to construct mutually orthogonal Walsh-Hadamard matrices and mutually orthogonal Golay-paired Hadamard matrices, which represent respectively a collection of mutually orthogonal complementary sets...
This paper presents a novel ultra-wideband (UWB) system for low power, long range, mid to high data rate mesh networking applications. Combined with the complementary code division multiplexing modulation and the multicode interleaved direct sequence spread spectrum techniques, the system aims to achieve interference resistance, coexistence with legacy systems, and robust performance in hostile multipath...
This paper presents a new method to improve on block spread OFDM by exploiting time diversity to ensure that the blocks are independent and uncorrelated in a multipath environment. While BSOFDM utilizes frequency diversity to significantly improve on OFDM in frequency selective channel, this did not improve during flat fading channel which does occur during transmission. Our work has also shown that...
The performance of impulse-train-modulated ultra-wideband (UWB) systems for the ideal additive white Gaussian noise channel is analyzed in this letter. The derived formulae are also used to optimize the modulation parameter of a Gaussian monocycle UWB impulse radio
A new electrochemical cell assembly with the combination of UV and amperometric detector (AD) based on their complementarity was described. A Nafion tubing junction was used to decouple the high voltage from the separation capillary in the rear of on-column UV detector. In this mode, the electroactive and inert compounds could be detected by UV and AD at the same time. Aromatic amines were determined...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.