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Wireless Systems (wireless + system)

Distribution by Scientific Domains

Engineering	76%
Information Science and Computing	19%

Selected Abstracts

Hopfield neural-network-based dynamic resource allocation scheme for non-real-time traffic in wireless networks

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2009
José F. Monserrat
Abstract Dynamic resource allocation (DRA) plays a fundamental role in current and future wireless networks, including 3G systems. In this paper, a scheduling DRA scheme for non-real-time (NRT) packet services in wireless system is proposed based on the use of Hopfield neural networks (HNN). The scheme exploits the fast response time of HNN for solving NP optimization problems and has been particularized for the downlink transmission in a UMTS system, although it could be easily extended to any other radio access technology. The new DRA scheme follows a delay-centric approach, since it maximizes the overall system resource utilization while minimizing the packet delay. Simulation results confirm that the proposed HNN-based DRA scheme is effective in supporting different types of NRT services, while achieving efficient utilization of radio resources. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Adaptive joint beamforming and B-MMSE detection for CDMA signal reception under multipath interference

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2004
Hsiao-Hwa Chen
Abstract The combination of antenna array beamforming with multiuser detection can effectively improve the detection efficiency of a wireless system under multipath interference, especially in a fast-fading channel. This paper studies the performance of an adaptive beamformer incorporated with a block-wise minimum mean square error(B-MMSE) detector, which works on a unique signal frame characterized by training sequence preamble and data blocks segmented by zero-bits. Both beam-former weights updating and B-MMSE detection are carried out by either least mean square (LMS) or recursive least square (RLS) algorithm. The comparison of the two adaptive algorithms applied to both beamformer and B-MMSE detector will be made in terms of convergence behaviour and estimation mean square error. Various multipath patterns are considered to test the receiver's responding rapidity to changing multipath interference. The performance of the adaptive B-MMSE detector is also compared with that of non-adaptive version (i.e. through direct matrix inversion). The final performance in error probability simulation reveals that the RLS/B-MMSE scheme outperforms non-adaptive B-MMSE by 1,5 dB, depending on the multipath channel delay profiles of concern. The obtained results also suggest that adaptive beamformer should use RLS algorithm for its fast and robust convergence property; while the B-MMSE filter can choose either LMS or RLS algorithm depending on antenna array size, multipath severity and implementation complexity. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Wireless video streaming with TCP and simultaneous MAC packet transmission (SMPT),

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 5 2004
Frank H. P. Fitzek
Abstract Video streaming is expected to account for a large portion of the traffic in future networks, including wireless networks. It is widely accepted that the user datagram protocol (UDP) is the preferred transport protocol for video streaming and that the transmission control protocol (TCP) is unsuitable for streaming. The widespread use of UDP, however, has a number of drawbacks, such as unfairness and possible congestion collapse, which are avoided by TCP. In this paper we investigate the use of TCP as the transport layer protocol for streaming video in a multi-code CDMA cellular wireless system. Our approach is to stabilize the TCP throughput over the wireless links by employing a recently developed simultaneous MAC packet transmission (SMPT) approach at the link layer. We study the capacity, i.e. the number of customers per cell, and the quality of service for streaming video in the uplink direction. Our extensive simulations indicate that streaming over TCP in conjunction with SMPT gives good performance for video encoded in a closed loop, i.e. with rate control. We have also found that TCP is unsuitable (even in conjunction with SMPT) for streaming the more variable open-loop encoded video. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Nonlinear simulation of mixers for assessing system-level performance

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2005
Nuno B. Carvalho
Abstract This article deals with nonlinear simulation methods intended to evaluate the impact of mixer nonidealities on the performance of a wireless system. Behavioral models capable of accurately describing the mixer's nonlinear dynamic features at the system level are currently unavailable. The possibility of using alternative circuit analysis techniques to reach this goal is discussed. After a brief review of existing mixer analysis methods, the focus is directed to the techniques amenable to efficiently handling periodic carriers modulated by complex stochastic signals. In particular, it is shown how multi-envelope transient methods coupled with a three-dimensional harmonic-balance engine can model a nonlinear dynamic mixer excited by a modulated RF signal accompanied by a strong adjacent channel interferer and with a local oscillator corrupted by phase noise. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source]

Visible light communication systems for optical video transmission

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2010
J. Rufo
Abstract This article describes an optical wireless system based on visible light communication (VLC), which allows a video broadcasting to reach a bit rate of 1 Mbps, although this system can also be used for low-speed sensor interconnections. The main advantages of this technology are the robustness against EM interference, safety for human eye, and security against undesired network access. In this article, we present the electronic structure of a low-cost VLC transceiver, the modulation process and the Ethernet interface that has been implemented in each AP (access point). Finally, some conclusions are drawn. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1572,1576, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25236 [source]

A wideband 8-element omnidirectional array for wireless system

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2007
Dakui Wu
Abstract A smart broad-band planar antenna for wireless system is presented. The simple modeling of this antenna and design method based on equivalent circuits has been developed. An eight-element planar array has been designed, fabricated and measured. Measured results exhibit good performance of the return loss and horizontal plane radiation pattern. The measured 10-dB return loss bandwidth of the broad-band planar array is demonstrated to be 62.5% and the un-roundness of its horizontal plane pattern is less than 4.5 dB. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2944,2946, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22925 [source]

Cancellation of local oscillator phase-noise in 60-GHz high-data-rate wireless systems

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2004
C. Loyez
Abstract A cancellation device of phase-noise is implemented in a wireless system at 60 GHz. By using only MMIC VCOs to perform frequency conversions, such a system effectively transmits signals with a QPSK-modulation scheme. For a 50 Mb/s data-rate, performances are similar to that of an ideal conventional system. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 268,272, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20274 [source]

A compact multilayer diplexer in LTCC substrate using LPF with multiple attenuation poles and wideband BPF

ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 5 2010
Shimpei Oshima
Abstract Recently, compact wideband BPFs for a UWB system have been studied actively. In this paper we propose a compact diplexer built into an LTCC substrate for a UWB system and 2.4-GHz wireless systems. First, a wideband BPF for a UWB system and an LPF with multiple attenuation poles for 2.4-GHz wireless systems are described. Second, we design matching circuits of a common port to retain the basic performance of both the BPF and the LPF. Third, in accordance with the results of the study, we design a compact diplexer built into an LTCC substrate. Finally, we verify the effectiveness of the proposed method by experiments. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(5): 24,32, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10210 [source]

Joint packet scheduling and dynamic base station assignment for CDMA data networks

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2008
Christian Makaya
Abstract In current code division multiple access (CDMA) based wireless systems, a base station (BS) schedules packets independently of its neighbours, which may lead to resource wastage and the degradation of the system's performance. In wireless networks, in order to achieve an efficient packet scheduling, there are two conflicting performance metrics that have to be optimized: throughput and fairness. Their maximization is a key goal, particularly in next-generation wireless networks. This paper proposes joint packet scheduling and BS assignment schemes for a cluster of interdependent neighbouring BSs in CDMA-based wireless networks, in order to enhance the system performance through dynamic load balancing. The proposed schemes are based on sector subdivision in terms of average required resource per mobile station and utility function approach. The fairness is achieved by minimizing the variance of the delay for the remaining head-of-queue packets. Inter-cell and intra-cell interferences from scheduled packets are also minimized in order to increase the system capacity and performance. The simulation results show that our proposed schemes perform better than existing schemes available in the open literature. Copyright © 2007 John Wiley & Sons, Ltd. [source]

A novel fair random access scheme with throughput optimization using fuzzy controller for wireless systems

INTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 4 2009
M. R. M. Rizk
Good backoff algorithms should be able to achieve high channel throughput while maintaining fairness among active nodes. In this paper, we propose a novel backoff algorithm to improve the fairness of random access channels, while maximizing channel throughput. The mechanism of the proposed backoff algorithm uses backoff delay (retransmission delay) and channel-offered traffic to dynamically control the backoff interval, so that each active node increases its backoff interval in the case of collision by a factor which exponentially decreases as the backoff delay increases, and decreases its backoff interval in the case of successful transmission by a factor which exponentially decreases as the backoff delay of previous retransmission attempts increases. Also, the backoff interval is controlled according to the channel offered, traffic using a fuzzy controller to maximize channel throughput. Furthermore, the operation of the proposed backoff algorithm does not depend on knowledge of the number of active nodes. A computer simulation is developed using MATLAB to evaluate the performance of the proposed backoff algorithm and compare it with the binary exponential backoff (BEB) scheme, which is widely used owing to its high channel throughput, while its fairness is relatively poor. It is shown that the proposed backoff algorithm significantly outperforms the BEB scheme in terms of improving the performance of fairness, and converges to the ideal performance as the minimum backoff interval increases, while achieving high channel throughput. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Satellite rural communications: telephony and narrowband networks

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 5 2005
Roberto Conte
Abstract Rural communications are important for large and developing countries, and telecommunications systems have been implemented depending upon the available technology at the time. Rural users do not generate the same amount of revenue as urban users do, thus lowering incentives for rural telecommunications investment with service to those regions delayed as long as possible. Voice and data communications are essential to the economic development of a region, and it has been shown that traffic increases rapidly as soon as the service is available. Satellite-based digital networks provide efficient long-distance service to rural communities at lower cost than similar land-based wired networks with acceptable quality. Small earth stations along with Wireless Local Loops can provide both local and long-distance service efficiently and at low cost, offering digital multimedia services on a global scale. This paper focuses on the description of different narrowband technologies used to service rural communities, namely basic telephone and low-bit-rate data (<64 kbps) applications through the use of satellite and terrestrial wireless systems. A basic network economic planning description is presented, and important parameters such as satellite network size, topology and multiple access are identified in order to improve the process of effective and cost-efficient rural communications network design. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Design aspects of satellite,cellular hybrid wireless systems

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2002
Tamer ElBatt
Abstract In this paper we investigate various issues related to the design of satellite,cellular hybrid systems. First, we review the fundamental problems of channel partitioning and call admission/assignment. Second, we study the impact of different frequency reuse constraints, in both layers, on the optimum channel partitioning. Third, we investigate, analytically and via simulation, the effect of reducing the cell size. We emphasize the blocking-forced termination probabilities trade-off for pure cellular and satellite,cellular hybrid systems. Accordingly, an optimization problem with respect to the cell size is formulated. Finally, we search for the optimum dynamic call re-assignment policy that improves the system capacity at the expense of the complexity associated with tearing down a connection in one system and setting-up an alternative one in the other system. For a small hybrid system, we characterized the optimum re-assignment policies that minimize the blocking probability, dropping probability, and a weighted cost function of these probabilities. Copyright © 2002 John Wiley & Sons, Ltd. [source]

A new balance-fed disc-slit monopole antenna for modern wireless systems

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2010
Cheng-Nan Chiu
Abstract This article proposes a novel balance-fed disc-slit monopole antenna for modern wireless systems. The compact antenna is realized by merging a single-ended disc-slit monopole antenna with a defected-ground balun. The resulting antenna has the special merits of high immunity against electromagnetic interference from nearby circuits and less sensitivity to size variation of the corresponding ground plane. A prototype was created and examined, and the results obtained demonstrate the promising performance of the newly proposed antenna. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1239,1240, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25182 [source]

Investigating the performance of MIMO systems from an electromagnetic perspective

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2006
Marek E. Bialkowski
Abstract Multiple input multiple output (MIMO) wireless systems use multiple element antennas (MEAs) at the transmitter (TX) and the receiver (RX) in order to offer improved information rates (capacity) over conventional single antenna systems in rich scattering environments. In this paper, an example of a simple MIMO system is considered in which both antennas and scattering objects are formed by wire dipoles. Such a system can be analyzed in the strict electromagnetic (EM) sense and its capacity can be determined for varying array size, interelement spacing, and distributions of scatterers. The EM model of this MIMO system can be used to assess the validity of single- or double-bounce scattering models for mixed line of sight (LOS) and non-line of sight (NLOS) signal-propagation conditions. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1233,1238, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21664 [source]

Cancellation of local oscillator phase-noise in 60-GHz high-data-rate wireless systems

Magnetoimpedance (MI) in amorphous wires: new materials and applications

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2009
Larissa V. Panina
Abstract The discovery of the magnetoimpedance (MI) effect in 1994 had a strong impact on the development of magnetic sensors. Along with traditional areas of sensing applications (data storage, bio-medical electronics, robotics and security), the MI elements have a high potential for applications in smart sensory systems (self-sensing composites) operating at microwave frequencies owing to still very large MI ratios of 50,100% in Co-rich amorphous wires at GHz frequencies. Here we introduce two types of MI wire composites: 2D-arrays and mixtures of wire pieces. In such materials the effective permittivity has strong dispersion in a frequency band determined by a plasma frequency or a dipole resonance, respectively. If MI wires are used as constituent elements, this dispersion may be very sensitive to the magnetic properties of wires since the wire impedance determines the relaxation parameter of the effective permittivity. For example, increasing the wire impedance by establishing the magnetisation along the axis with an external magnetic field broadens the resonance band, decreases the reflection amplitude and may open a bandpass. Depending on the magnetic anisotropy in wires, tuning can be realized with both magnetic field and stress. It is foreseen that MI-wire composite materials could be suitable for large scale applications, in particular, for free space filters in secure wireless systems and for microwave nondestructive testing and control in civil engineering. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Performance assessment of next-generation wireless mobile systems

BELL LABS TECHNICAL JOURNAL, Issue 4 2009
Krishna Balachandran
The deployment of third generation (3G) systems such as Universal Mobile Telecommunications System (UMTS) and code division multiple access (CDMA) 1X is now ubiquitous. Furthermore, several operators have already deployed evolved 3G systems such as high speed packet access (HSPA) and 1× evolution data optimized (1× EV-DO). These 3G and evolved 3G systems are based on spread spectrum technologies. Now the industry has begun to focus on next-generation wireless systems based on orthogonal frequency division multiplexing (OFDM) technology, flat-Internet Protocol (IP) architectures, and advanced multiple input-multiple output (MIMO) capabilities. These next-generation technologies, primarily are: 3rd Generation Partnership Project (3GPP)-based evolved UMTS terrestrial radio access network (EUTRAN), also called Long Term Evolution (LTE); 3rd Generation Partnership Project 2 (3GPP2)-based Ultra Mobile Broadband (UMB); and Institute of Electrical and Electronics Engineers (IEEE) 802. 16e-based Worldwide Interoperability for Microwave Access (WiMAX). These technologies are in the final specifications to initial deployment phases in selected markets. This paper provides an overview and performance analysis of these next-generation technologies based on their initial releases. Additionally, a comparative performance analysis of these technologies is also presented. © 2009 Alcatel-Lucent. [source]

Design and analysis of an IEEE 802.16e-based OFDMA communication system

BELL LABS TECHNICAL JOURNAL, Issue 4 2007
Krishna Balachandran
IEEE 802.16e has emerged as a strong candidate standard for future wireless systems primarily because it offers the potential for high spectral efficiency, flexible spectrum options (e.g., 2,6 GHz), scalable carrier bandwidth options (e.g., from 1.25 MHz to 20 MHz), multiple duplexing options (time and frequency division duplex), various subchannelization options, and, unlike its IEEE 802.16 predecessors, mobility. Because of the recent emergence of IEEE 802.16e and the complexity it poses in system analysis, there is little published work in the literature regarding the actual system capacity/ throughput performance of IEEE 802.16e for high data rate services. In this paper, we investigate the link and system level performance on the downlink of an IEEE 802.16e-based orthogonal frequency division multiple access (OFDMA) communication system and provide recommendations on high performance IEEE 802.16e system design and deployment configurations. We also propose dynamic resource allocation methods that may be used in OFDMA systems and investigate their performance. @ 2007 Alcatel-Lucent. [source]

User-level QoS and traffic engineering for 3G wireless 1xEV-DO systems

BELL LABS TECHNICAL JOURNAL, Issue 2 2003
Simon C. Borst
Third-generation (3G) wireless systems such as 3G1X, 1xEV-DO, and 1xEV-DV provide support for a variety of high-speed data applications. The success of these services critically relies on the capability to ensure an adequate quality of service (QoS) experience to users at an affordable price. With wireless bandwidth at a premium, traffic engineering and network planning play a vital role in addressing these challenges. We present models and techniques that we have developed for quantifying the QoS perception of 1xEV-DO users generating file transfer protocol (FTP) or Web browsing sessions. We show how user-level QoS measures may be evaluated by means of a Processor-Sharing model that explicitly accounts for the throughput gains from multi-user scheduling. The model provides simple analytical formulas for key performance metrics such as response times, blocking probabilities, and throughput. Analytical models are especially useful for network deployment and in-service tuning purposes due to the intrinsic difficulties associated with simulation-based optimization approaches. © 2003 Lucent Technologies Inc. [source]