| 1. |
- Chen, Miaoxiang
(författare)
-
Printed electrochemical devices using conducting polymers as active materials on flexible substrates
- 2005
-
Ingår i: Proceedings of the IEEE. - : IEEE conference proceedings. - 0018-9219 .- 1558-2256. ; 93:7, s. 1339-1347, s. 1339-1347
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reports some of our initial works in pursuit of a simple and low-cost method of fabricating all-organic electrochemical diodes, triodes, and transistors on flexible plastic or paper substrates. Conducting polymer poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT: PSS), utilized as an active component, is deposited by spin-coating or printing techniques. The devices are directly fabricated from design without the need for masks, patterns, or dies. The output characteristics of both half-wave and full-wave rectifier circuits from two-terminal diodes show stable performances at frequencies below 5 Hz. In three-terminal tunable triodes, threshold voltage can be tuned in the range between 0.25 and 1.6 V In Jour-terminal transistors, ambipolar operation function can be realized in one single device. I-ON/I-OFF current ratios of 10(3)-10(4) have been achieved in the triode and transistor at operating voltages below 3 V In addition, the device applications in electrochromic displays, logical circuits, as well as the switching speed of the circuits and device stability, are discussed.
|
|
| 2. |
- Sternad, Mikael, et al.
(författare)
-
Towards systems beyond 3G based on adaptive OFDMA transmission
- 2007
-
Ingår i: Proceedings of the IEEE. - 0018-9219 .- 1558-2256. ; 95:12, s. 2432-2455
-
Forskningsöversikt (refereegranskat)abstract
- High data rates, high spectral efficiency, flexibility, and low delays over the air interface will be important features in next-generation wireless systems. The overall challenge will be packet scheduling and adaptive radio transmission for multiple users, via multiple antennas and over frequency-selective wideband channels. This problem needs to be structured to obtain feasible solutions. The basic simplifying assumptions used here are clustering of antennas into cells, orthogonal transmission by use of cyclic-prefix orthogonal frequency-division multiplexing (OFDM) and a time-scale separation view of the total link adaptation, scheduling and intercell coordination problem. Based on these assumptions, we survey techniques that adapt the transmission to the temporal, frequency, and spatial channel properties. We provide a systematic overview of the design problems, such as the dimensioning of the allocated time-frequency resources, the influence of duplexing schemes, adaptation control issues for downlinks and uplinks, timing issues, and their relation to the required performance of channel predictors. Specific design choices are illustrated by recent research within the Swedish Wireless IP program and the EU IST-WINNER project. The presented results indicate that high-performance adaptive OFDM transmission systems are indeed feasible, also for challenging scenarios that involve vehicular velocities, high carrier frequencies, and high bandwidths
|
|
| 3. |
- Svensson, Arne, 1955
(författare)
-
An Introduction to Adaptive QAM Modulation Schemes for Known and Predicted Channels
- 2007
-
Ingår i: Proceedings of the IEEE. - 1558-2256 .- 0018-9219. ; 95:12, s. 2322-2336
-
Tidskriftsartikel (refereegranskat)abstract
- A major disadvantage with fixed modulation(nonadaptive) on channels with varying signal-to-noise ratio(SNR) is that the bit-error-rate (BER) probability performance ischanging with the channel quality. Most applications require acertain maximum BER and there is normally no reason forproviding a smaller BER than required. An adaptive modulationscheme, on the contrary, can be designed to have a BER whichis constant for all channel SNRs. The spectral efficiency of thefixed modulation is constant, while it, in general, will increasewith increasing channel SNRs for the adaptive scheme. This ineffect means that the average spectral efficiency of theadaptive scheme is improved, while at the same time the BERis better suited to the requirement of the application. Thus, theadaptive link becomes much more efficient for data transmission.The major disadvantage is that the transmitter needs toknow the channel SNR such that the best suitable modulation ischosen and the receiver must be informed on the usedmodulation in order to decode the information. This leads toan increased overhead in the system as compared with a fixedmodulation system. In this paper, we introduce adaptivemodulation systems by presenting some of the simpleradaptive quadrature amplitude modulation schemes and theirperformance for both perfectly known and predicted channels.
|
|
| 4. |
|
|
| 5. |
- Welch, J., et al.
(författare)
-
The Allen Telescope Array: The First Widefield, Panchromatic, Snapshot Radio Camera for Radio Astronomy and SETI
- 2009
-
Ingår i: Proceedings of the IEEE. - 1558-2256 .- 0018-9219. ; 97:8, s. 1438-1447
-
Tidskriftsartikel (refereegranskat)abstract
- The first 42 elements of the Allen Telescope Array (ATA-42) are beginning to deliver data at the Hat Creek Radio Observatory in northern California. Scientists and engineers are actively exploiting all of the flexibility designed into this innovative instrument for simultaneously conducting surveys of the astrophysical sky and conducting searches for distant technological civilizations. This paper summarizes the design elements of the ATA, the cost savings made possible by the use of commercial off-the-shelf components, and the cost/performance tradeoffs that eventually enabled this first snapshot radio camera. The fundamental scientific program of this new telescope is varied and exciting; some of the first astronomical results will be discussed.
|
|
| 6. |
- Akenine-Möller, Tomas, et al.
(författare)
-
Graphics processing units for handhelds
- 2008
-
Ingår i: Proceedings of the IEEE. - 0018-9219. ; 96:5, s. 779-789
-
Tidskriftsartikel (refereegranskat)abstract
- During the past few years, mobile phones and other handheld devices have gone from only handling dull text-based menu systems to, on an increasing number of models, being able to render high-quality three-dimensional graphics at high frame rates. This paper is a survey of the special considerations that must be taken when designing graphics processing units (GPUs) on such devices. Starting off by introducing desktop GPUs as a reference, the paper discusses how mobile GPUs are designed, often with power consumption rather than performance as the primary goal. Lowering the bus traffic between the GPU and the memory is an efficient way of reducing power consumption, and therefore some high-level algorithms for bandwidth reduction are presented. In addition, an overview of the different APIs that are used in the handheld market to handle both two-dimensional and three-dimensional graphics is provided. Finally, we present our outlook for the future and discuss directions of future research on handheld GPUs.
|
|
| 7. |
- Molisch, Andreas
(författare)
-
Ultra-Wide-Band Propagation Channels
- 2009
-
Ingår i: Proceedings of the IEEE. - 0018-9219. ; 97:2, s. 353-371
-
Forskningsöversikt (refereegranskat)abstract
- Understanding ultra-wide-band (UWB) propagation channels is a prerequisite for UWB system design as well as communication-theoretic and information-theoretic investigations. This paper surveys the fundamental properties of UWB channels, pointing out the differences to conventional channels. if the relative bandwidth is large, the propagation processes, and therefore path loss and shadowing, become frequency-dependent, and the well-known wide-sense stationary uncorrelated scattering model is not applicable anymore. if the absolute bandwidth is large, the shape of the impulse responses as well as the fading statistics change. This paper also describes methods for measuring UWB channels and extracing channel parameters. Throughout this paper, the relationship between channel properties and other areas of UWB research are pointed out.
|
|
| 8. |
- Win, Moe Z., et al.
(författare)
-
History and Applications of UWB
- 2009
-
Ingår i: Proceedings of the IEEE. - 0018-9219. ; 97:2, s. 198-204
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 9. |
- Zhang, Jinyun, et al.
(författare)
-
UWB Systems for Wireless Sensor Networks
- 2009
-
Ingår i: Proceedings of the IEEE. - 0018-9219. ; 97:2, s. 313-331
-
Tidskriftsartikel (refereegranskat)abstract
- Wireless sensor networks are emerging as an important area for communications. They enable a wealth of new applications including surveillance, building control, factory automation, and in-vehicle sensing. The sensor nodes have to operate under severe constraints on energy consumption and form factor, and provide the ability for precise self-location of the nodes. These requirements can be fulfilled very well by various forms of ultra-wide-band (UWB) transmission technology. We discuss various techniques and tradeoffs in UWB systems and indicate that time-hopping and frequency-hopping impulse radio physical layers combined with simple multiple-access techniques like ALOHA are suitable designs. We also describe the IEEE 802.15.4a standard, an important system that adopts UWB impulse radio to ensure robust data communications and precision ranging. in order to accommodate heterogeneous networks, it uses specific modulation, coding, and ranging waveforms that can be detected well by both coherent and noncoherent receivers.
|
|
