Showing papers in "IEEE Circuits and Systems Magazine in 2006"
TL;DR: Conditions under which ensemble based systems may be more beneficial than their single classifier counterparts are reviewed, algorithms for generating individual components of the ensemble systems, and various procedures through which the individual classifiers can be combined are reviewed.
Abstract: In matters of great importance that have financial, medical, social, or other implications, we often seek a second opinion before making a decision, sometimes a third, and sometimes many more. In doing so, we weigh the individual opinions, and combine them through some thought process to reach a final decision that is presumably the most informed one. The process of consulting "several experts" before making a final decision is perhaps second nature to us; yet, the extensive benefits of such a process in automated decision making applications have only recently been discovered by computational intelligence community. Also known under various other names, such as multiple classifier systems, committee of classifiers, or mixture of experts, ensemble based systems have shown to produce favorable results compared to those of single-expert systems for a broad range of applications and under a variety of scenarios. Design, implementation and application of such systems are the main topics of this article. Specifically, this paper reviews conditions under which ensemble based systems may be more beneficial than their single classifier counterparts, algorithms for generating individual components of the ensemble systems, and various procedures through which the individual classifiers can be combined. We discuss popular ensemble based algorithms, such as bagging, boosting, AdaBoost, stacked generalization, and hierarchical mixture of experts; as well as commonly used combination rules, including algebraic combination of outputs, voting based techniques, behavior knowledge space, and decision templates. Finally, we look at current and future research directions for novel applications of ensemble systems. Such applications include incremental learning, data fusion, feature selection, learning with missing features, confidence estimation, and error correcting output codes; all areas in which ensemble systems have shown great promise
2,628 citations
TL;DR: A major shift in radio design is now just beginning which attempts to share spectrum in a fundamentally new way, and two methods that are being investigated are the use of ultra wideband transmission and cognitive techniques.
Abstract: A major shift in radio design is now just beginning which attempts to share spectrum in a fundamentally new way. These radios are addressing the fact that spectrum is actually poorly utilized in many bands, in spite of the increasing demand for wireless connectivity. The new approaches to spectrum sharing make use of the advances in technology to implement new wireless systems that can share previously allocated spectra in such a way that the primary users of these spectra are not affected. Additionally, the allowed use of this band is on an unlicensed basis. Two methods that are being investigated to accomplish this task are the use of ultra wideband transmission and cognitive techniques. Ultra wideband transmission relies on the fact that if the bandwidth is increased, that reliable data transmission can occur even at power levels so low that primary radios in the same spectral bands are not affected. On the other hand the cognitive approach does not necessarily limit the transmission power, but rather attempts to share the spectra through a dynamic avoidance strategy. The opportunities and challenges of this new era in radio design are described along with the open questions in their implementation
255 citations
TL;DR: A multi-standard simulator has been developed to validate the architectural and design choices in terms of error rates at bit or packet level and the ideas behind the key RF blocks and some details of circuit implementation are described.
Abstract: The availability of multi-standard terminals will be key to provide location independent connections able to take advantage of any possible infrastructure. This paper addresses both the architecture and the circuits for the RF front-end of a terminal with cellular (GSM, EDGE and UMTS), LAN (IEEE802.11a/b/g) and Bluetooth radio interfaces. A multi-standard simulator has been developed to validate the architectural and design choices in terms of error rates at bit or packet level. The simulator takes into account implementation non-idealities and performs all tests to be passed to comply with the given standards. It also hints at the need for implementation margins as well as at possible optimization between different RF-blocks. The final solution, still under design, will consists of two chips, one including the TX and the other the RX for all the above standards. The cellular (plus Bluetooth) transmitter relies on a Linear amplification with Non-linear Component (LINC) architecture that uses direct modulation of the carrier. This allows power saving because DAC and up-conversion mixers are not required. The WLAN (plus Bluetooth) transmitter adopts a direct-conversion architecture that implements an internal output matching over all the frequency bands while maintaining good system efficiency. The same building blocks are used for all standards, saving power and chip area. The cellular receiver architecture is able to reconfigure between Low-IF for GSM and direct conversion for UMTS and Bluetooth. The key aspects in achieving the specs in a fully integrated fashion are a mixer with a very high dynamic range, a careful control of DC offsets and a highly tunable VCO. The WLAN receiver also uses direct-conversion with a Low Noise Amplifier based on a common gate topology that uses positive feedback through integrated transformers to improve input matching and noise. The frequency down-converter uses current driven passive mixers to achieve low 1/f noise corner, and high linearity with low power consumption. Finally, the base-band blocks can be shared among all the standard, thanks to their high reconfigurability. The paper describes the ideas behind the key RF blocks and some details of circuit implementation. Experimental measurements from sub-blocks in a 0.13 /spl mu/m CMOS technology are presented and discussed.
114 citations
TL;DR: In this article, the authors present a feature called "M A S T E R S E R E R IE S Feature", which is based on the concept of feature extraction.
Abstract: © M A S T E R S E R IE S Feature
64 citations
TL;DR: The need for different types of wireless connections to mobile terminals has increased rapidly during the last few years and new process technologies, which use low supply voltages and are optimised for digital circuitry, set additional challenges for future receiver design.
Abstract: The need for different types of wireless connections to mobile terminals has increased rapidly during the last few years. The mobile terminal must be able to connect to globally existing cellular networks, as well as to different ad-hoc networks. The receivers designed for these terminals must achieve a high integration level and a high level of component sharing to meet the strict size and cost requirements. In addition, the performance of a multimode receiver must be compatible with existing single-system receivers. New process technologies, which use low supply voltages and are optimised for digital circuitry, set additional challenges for future receiver design. Several integrated receiver ICs for the multimode and multiband transceivers have been published to meet these demands. This paper gives a review of these circuit solutions and a brief introduction to the demands set by different systems and receiver architectures for the design of the multimode and multiband receiver
59 citations
TL;DR: This paper describes adaptivity design concepts and application of design for adaptivity to multi-standard circuits and systems for wireless communications and an exploratory multi- standard RF front-end is discussed.
Abstract: Telecom trends such as smooth migration towards higher data rates and higher capacities for multimedia applications, and provision of various services (text, audio, video) from different standards with the same wireless device require integrated designs that work across multiple standards, can easily be reused and achieve maximum hardware share at minimum power consumption. This can be achieved by using adaptive circuits that are able to trade off power consumption for performance on the fly. Realization of the adaptivity function requires scaling of parameters such as current consumption to the demands of the signal-processing task. This paper describes adaptivity design concepts and application of design for adaptivity to multi-standard circuits and systems for wireless communications. An exploratory multi-standard RF front-end is discussed with phase-noise tuning, noise-figure tuning, and input-intercept point tuning requirements of 21 dB, 12 dB, and 7 dB, respectively.
53 citations
TL;DR: This paper presents analog and digital base-band circuits that are able to support GSM (with EDGE), WCDMA (UMTS), WLAN and Bluetooth using reconfigurable building blocks that can trade off power consumption for performance on the fly, depending on the standard to be supported and the required QoS level.
Abstract: Multimedia applications are driving wireless network operators to add high-speed data services such as EDGE (E-GPRS), WCDMA (UMTS) and WLAN (IEEE 802.11a,b,g) to the existing network. This creates the need for multi-mode cellular handsets that support a wide range of communication standards, each with a different RF frequency, signal bandwidth, modulation scheme, etc. This in turn generates several design challenges for the analog and digital building blocks of the physical layer. In addition to the above mentioned protocols, mobile devices often include Bluetooth, GPS, FM-radio and TV services that can work concurrently with data and voice communication. Multi-mode, multi-band, and multi-standard mobile terminals must satisfy all these different requirements. Sharing and/or switching transceiver building blocks in these handsets is mandatory in order to extend battery life and/or to reduce cost. Only adaptive circuits that are able to reconfigure themselves within the handover time can meet the design requirements of a single receiver or transmitter covering all the different standards while ensuring seamless inter-operability. This paper presents analog and digital base-band circuits that are able to support GSM (with EDGE), WCDMA (UMTS), WLAN and Bluetooth using reconfigurable building blocks. The blocks can trade off power consumption for performance on the fly, depending on the standard to be supported and the required QoS (Quality of Service) level.
52 citations
TL;DR: An overview of the evolution of mobile terminal architectures, from monolithic to flexible, modular, and capable of meeting the increasing demand for an ever larger number of features at the right cost and time to market is presented.
Abstract: Terminals, including traditional cellular phones, have historically been optimized for a small number of services over a specific network. With the convergence of consumer electronics and Internet-based services, voice and video are now being offered on a variety of access networks, and many functions are being combined into single devices. In addition to new sophisticated audio/video coding and graphics capabilities, there is a growing demand for cheap and ubiquitous broadband wireless Internet access. This demand is driving the need for multiradio platforms that include new licensed and unlicensed air interface technologies, such as WLAN, UWB and Wimax. The proliferation of new applications and wireless standards has created the need for a dramatic change in the portable/mobile terminal architecture. This paper presents an overview of the evolution of mobile terminal architectures, from monolithic to flexible, modular, and capable of meeting the increasing demand for an ever larger number of features at the right cost and time to market
40 citations
11 citations
TL;DR: The first hardware supports and technologies that allow the studies of whole bodies of molecules through the different steps of the biological information flow are reviewed, and then some of the algorithms and softwares for data processing and integration are reviewed.
Abstract: High-throughput biological data acquisition and processing technologies have shifted the focus of biological research from the realm of traditional experimental science (wet biology) to that of information science (in silico biology). Powerful computation and communication means can be applied to the very large amount of apparently incoherent data coming from biomedical research. Part of the experiments and tests that we used to do in vitro and/or in vivo can now be done in silico. The concept of Laboratory (Lab) on Chip (LoC) is the natural evolution of System on Chip (SoC) by using an array of heterogeneous technologies. This paper reviews first hardware supports and technologies that allow the studies of whole bodies of molecules through the different steps of the biological information flow, and then some of the algorithms and softwares for data processing and integration
5 citations
TL;DR: The comparison the IBM main frame packaging technology and hardware system structure for the last three CMOS generations (z900, z990 and z9) and an outlook on the key challenges for the future are presented.
Abstract: This paper gives a comparison the IBM main frame packaging technology and hardware system structure for the last three CMOS generations (z900, z990 and z9) and presents an outlook on the key challenges for the future. The chip and packaging technologies have enabled a node like structure which resulted in a modular concept supporting the IBM On Demand Business Concept. The key challenges for the high-end servers which are the continuously increasing data bandwidth and the increasing node power are discussed