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Showing papers on "Data transmission published in 2002"


Patent
05 Nov 2002
TL;DR: In this article, the authors provide techniques to achieve better utilization of the available resources and robust performance for the downlink and uplink in a multiple-access MIMO system.
Abstract: Techniques to achieve better utilization of the available resources and robust performance for the downlink and uplink in a multiple-access MIMO system. Techniques are provided to adaptively process data prior to transmission, based on channel state information, to more closely match the data transmission to the capacity of the channel. Various receiver processing techniques are provided to process a data transmission received via multiple antennas at a receiver unit. Adaptive reuse schemes and power back-off are also provided to operate the cells in the system in a manner to further increase the spectral efficiency of the system (e.g., reduce interference, improve coverage, and attain high throughput). Techniques are provided to efficiently schedule data transmission on the downlink and uplink. The scheduling schemes may be designed to optimize transmissions (e.g., maximize throughput) for single or multiple terminals in a manner to meet various constraints and requirements.

671 citations


Journal ArticleDOI
TL;DR: In-depth simulation shows that the proposed MPDU-based link adaptation scheme outperforms the single-mode schemes and the autorate fallback (ARF) scheme-which is used in Lucent Technologies' WaveLAN-II networking devices-significantly in terms of the average goodput, the frame drop rate, and the average number of transmission attempts per data frame delivery.
Abstract: Link adaptation to dynamically select the data transmission rate at a given time has been recognized as an effective way to improve the goodput performance of the IEEE 802.11 wireless local-area networks (WLANs). Recently, with the introduction of the new high-speed 802.11a physical layer (PHY), it is even more important to have a well-designed link adaptation scheme work with the 802.11a PHY such that its multiple transmission rates can be exploited. In this paper, we first present a generic method to analyze the goodput performance of an 802.11a system under the distributed coordination function (DCF) and express the expected effective goodput as a closed-form function of the data payload length, the frame retry count, the wireless channel condition, and the selected data transmission rate. Then, based on the theoretical analysis, we propose a novel MPDU (MAC protocol data unit)-based link adaptation scheme for the 802.11a systems. It is a simple table-driven approach and the basic idea is to preestablish a best PHY mode table by applying the dynamic programming technique. The best PHY mode table is indexed by the system status triplet that consists of the data payload length, the wireless channel condition, and the frame retry count. At runtime, a wireless station determines the most appropriate PHY mode for the next transmission attempt by a simple table lookup, using the most up-to-date system status as the index. Our in-depth simulation shows that the proposed MPDU-based link adaptation scheme outperforms the single-mode schemes and the autorate fallback (ARF) scheme-which is used in Lucent Technologies' WaveLAN-II networking devices-significantly in terms of the average goodput, the frame drop rate, and the average number of transmission attempts per data frame delivery.

619 citations


Patent
28 Oct 2002
TL;DR: In this article, a power and data coupler couples the network data signal and the power signal, received through a data input and a power input respectively, and transmits the coupled signal, to a distance of three meters or more, over the transmission line.
Abstract: Electrical supply current, sufficient to power a wireless access point, is transmitted concurrently with a network data signal across a transmission line. A power and data coupler couples the network data signal and the power signal, received through a data input and a power input respectively, and transmits the coupled signal, to a distance of three meters or more, over the transmission line to a power and data decoupler. The power and data decoupler separates the power signal from the network data signal and supplies those signals to a power output port and a data output port, respectively, for use by a wireless access node. The power signal may be modulated at a low frequency relative to the frequency of the data signal, and the network data signal has a data transmission rate of one megabit/second or higher.

534 citations


Patent
08 Jan 2002
TL;DR: In this paper, a scheduler forms one or more sets of terminals for possible (downlink or uplink) data transmission for each of a number of frequency bands, with each sub-hypotheses corresponding to (1) specific assignments of transmit antennas to the terminal(s) in the hypothesis (for the downlink) or (2) a specific order for processing the uplink data transmissions from the terminals(s).
Abstract: Techniques to schedule terminals for data transmission on the downlink and/or uplink in a MIMO-OFDM system based on the spatial and/or frequency “signatures” of the terminals. A scheduler forms one or more sets of terminals for possible (downlink or uplink) data transmission for each of a number of frequency bands. One or more sub-hypotheses may further be formed for each hypothesis, with each sub-hypothesis corresponding to (1) specific assignments of transmit antennas to the terminal(s) in the hypothesis (for the downlink) or (2) a specific order for processing the uplink data transmissions from the terminal(s) (for the uplink). The performance of each sub-hypothesis is then evaluated (e.g., based on one or more performance metrics). One sub-hypothesis is then selected for each frequency band based on the evaluated performance, and the one or more terminals in each selected sub-hypothesis are then scheduled for data transmission on the corresponding frequency band.

521 citations


Patent
Funyun Ling1, Jay Rodney Walton1, Steven J. Howard1, Mark S. Wallace1, John W. Ketchum1 
22 Mar 2002
TL;DR: In this paper, the received signals are processed to derive channel state information (CSI) indicative of characteristics of a number of transmission channels used for data transmission, and the CSI is transmitted back to the transmitter unit.
Abstract: Techniques for transmitting data from a transmitter unit to a receiver unit in a multiple-input multiple-output (MIMO) communication system. In one method, at the receiver unit, a number of signals are received via a number of receive antennas, with the received signal from each receive antenna comprising a combination of one or more signals transmitted from the transmitter unit. The received signals are processed to derive channel state information (CSI) indicative of characteristics of a number of transmission channels used for data transmission. The CSI is transmitted back to the transmitter unit. At the transmitter unit, the CSI from the receiver unit is received and data for transmission to the receiver unit is processed based on the received CSI.

516 citations


Patent
15 May 2002
TL;DR: In this article, one or more sets of terminals are formed for possible data transmission, with each set including a unique combination of one-or more terminals and corresponding to a hypothesis to be evaluated.
Abstract: Techniques to schedule downlink data transmission to a number of terminals in a wireless communication system. In one method, one or more sets of terminals are formed for possible data transmission, with each set including a unique combination of one or more terminals and corresponding to a hypothesis to be evaluated. One or more sub-hypotheses may further be formed for each hypothesis, with each sub-hypothesis corresponding to specific assignments of a number of transmit antennas to the one or more terminals in the hypothesis. The performance of each sub-hypothesis is then evaluated, and one of the evaluated sub-hypotheses is selected based on their performance. The terminal(s) in the selected sub-hypothesis are then scheduled for data transmission, and data is thereafter coded, modulated, and transmitted to each scheduled terminal from one or more transmit antennas assigned to the terminal.

482 citations


Journal ArticleDOI
TL;DR: This paper develops a model for multicarrier transmission over time-varying channels and focuses particularly on multiple-input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM), and proposes a time-domain approach to channel estimation.
Abstract: In this paper, we examine multicarrier transmission over time-varying channels. We first develop a model for such a transmission scheme and focus particularly on multiple-input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM). Using this method, we analyze the impact of time variation within a transmission block (time variation could arise both from Doppler spread of the channel and from synchronization errors). To mitigate the effects of such time variations, we propose a time-domain approach. We design ICI-mitigating block linear filters, and we examine how they are modified in the context of space-time block-coded transmissions. Our approach reduces to the familiar single-tap frequency-domain equalizer when the channel is block time invariant. Channel estimation in rapidly time-varying scenarios becomes critical, and we propose a scheme for estimating channel parameters varying within a transmission block. Along with the channel estimation scheme, we also examine the issue of pilot tone placement and show that in time-varying channels, it may be better to group pilot tones together into clumps that are equispaced onto the FFT grid; this placement technique is in contrast to the common wisdom for time-invariant channels. Finally, we provide numerical results illustrating the performance of these schemes, both for uncoded and space-time block-coded systems.

440 citations


Journal ArticleDOI
TL;DR: The net result is a new transceiver that is not only computationally efficient compared with the optimal maximum likelihood decoder, but it also yields a probability of error performance that is orders of magnitude smaller than traditional BLAST schemes for the same operating conditions.
Abstract: Turbo-BLAST is a novel multitransmit multireceive (MTMR) antenna scheme for high-throughput wireless communications. It exploits the following ideas: the Bell Labs layered space time (BLAST) architecture; random layered space-time (RLST) coding scheme by using independent block codes and random space-time interleaving; sub-optimal turbo-like receiver that performs iterative decoding of the RLST codes and estimation of the channel matrix in an iterative and, most important, simple fashion. The net result is a new transceiver that is not only computationally efficient compared with the optimal maximum likelihood decoder, but it also yields a probability of error performance that is orders of magnitude smaller than traditional BLAST schemes for the same operating conditions. This paper also presents experimental results using real-life indoor channel measurements demonstrating the high-spectral efficiency of turbo-BLAST.

416 citations


Journal ArticleDOI
TL;DR: An analytic solution for adaptive intra mode selection and joint source-channel rate control under time-varying wireless channel conditions is derived and significantly improves the end-to-end video quality in wireless video coding and transmission.
Abstract: We first develop a rate-distortion (R-D) model for DCT-based video coding incorporating the macroblock (MB) intra refreshing rate. For any given bit rate and intra refreshing rate, this model is capable of estimating the corresponding coding distortion even before a video frame is coded. We then present a theoretical analysis of the picture distortion caused by channel errors and the subsequent inter-frame propagation. Based on this analysis, we develop a statistical model to estimate such channel errors induced distortion for different channel conditions and encoder settings. The proposed analytic model mathematically describes the complex behavior of channel errors in a video coding and transmission system. Unlike other experimental approaches for distortion estimation reported in the literature, this analytic model has very low computational complexity and implementation cost, which are highly desirable in wireless video applications. Simulation results show that this model is able to accurately estimate the channel errors induced distortion with a minimum delay in processing. Based on the proposed source coding R-D model and the analytic channel-distortion estimation, we derive an analytic solution for adaptive intra mode selection and joint source-channel rate control under time-varying wireless channel conditions. Extensive experimental results demonstrate that this scheme significantly improves the end-to-end video quality in wireless video coding and transmission.

390 citations


Proceedings ArticleDOI
09 Jun 2002
TL;DR: This paper studies how link error rates affect this retransmission-aware metric, and how it leads to an efficient choice between a path with a large number of short- distance hops and another with a smaller number of large-distance hops.
Abstract: Current algorithms for minimum-energy routing in wireless networks typically select minimum-cost multi-hop paths. In scenarios where the transmission power is fixed, each link has the same cost and the minimum-hop path is selected. In situations where the transmission power can be varied with the distance of the link, the link cost is higher for longer hops; the energy-aware routing algorithms select a path with a large number of small-distance hops. In this paper, we argue that such a formulation based solely on the energy spent in a single transmission is misleading --- the proper metric should include the total energy (including that expended for any retransmissions necessary) spent in reliably delivering the packet to its final destination.We first study how link error rates affect this retransmission-aware metric, and how it leads to an efficient choice between a path with a large number of short-distance hops and another with a smaller number of large-distance hops. Such studies motivate the definition of a link cost that is a function of both the energy required for a single transmission attempt across the link and the link error rate. This cost function captures the cumulative energy expended in reliable data transfer, for both reliable and unreliable link layers. Finally, through detailed simulations, we show that our schemes can lead to upto 30-70% energy savings over best known current schemes, under realistic environments.

385 citations


Patent
23 Jan 2002
TL;DR: In this paper, a base code is used in combination with common or variable puncturing to achieve different coding rates required by the transmission channels, and unpunctured coded bits are grouped into non-binary symbols and mapped to modulation symbols (e.g., using Gray mapping).
Abstract: Coding techniques for a (e.g., OFDM) communication system capable of transmitting data on a number of “transmission channels” at different information bit rates based on the channels' achieved SNR. A base code is used in combination with common or variable puncturing to achieve different coding rates required by the transmission channels. The data (i.e., information bits) for a data transmission is encoded with the base code, and the coded bits for each channel (or group of channels with the similar transmission capabilities) are punctured to achieve the required coding rate. The coded bits may be interleaved (e.g., to combat fading and remove correlation between coded bits in each modulation symbol) prior to puncturing. The unpunctured coded bits are grouped into non-binary symbols and mapped to modulation symbols (e.g., using Gray mapping). The modulation symbol may be “pre-conditioned” and prior to transmission.

Patent
10 Oct 2002
TL;DR: In this article, the transducer is designed for perception of vibrations originated by a series of impacts, which can be used for key combination of access to computerized communication and control nets.
Abstract: used with a body conducting impact actions. SUBSTANCE: system has a data transmission device provided with a reciprocating impact head for transmission of coded series of discrete mechanical impact conducting body, and a data receiving device provided with a transducer sensitive to impacts on the second surface of the body conducting impact actions heat is essentially opposite its first surface. The transducer is designed for perception of vibrations originated by a series of impacts. The data transmission system well does for realization of the control of access, for example, for opening of slit locks, for opening of bank safes, for getting access to computerized communication and control nets. In these cases the data transmission system functions as a key with an electronic control, usually tapping off a single coed series of impacts, in particular, the key combination of access. EFFECT: enhanced efficiency of data transmission. 28 cl, 13 dwg

Journal ArticleDOI
TL;DR: Simulation results of the performance achieved by FMT modulation for very high-speed digital subscriber line systems, where upstream and downstream signals are separated by frequency-division duplexing, are presented and compared with DMT modulation.
Abstract: A filter-bank modulation technique called filtered multitone (FMT) and its application to data transmission for very high-speed digital subscriber line technology are described. The proposed scheme leads to significantly lower spectral overlapping between adjacent subchannels than for known multicarrier techniques such as discrete multitone (DMT) or discrete wavelet multitone. FMT modulation mitigates interference due to echo and near-end crosstalk signals, and increases the system throughput and reach. Signal equalization in an FMT receiver is accomplished in the form of per-subchannel symbol-spaced or fractionally spaced linear or decision-feedback equalization. The problem of channel coding for this type of modulation is also addressed, and an approach that allows combined removal of intersymbol-interference via precoding and trellis coding is described. Furthermore, practical design aspects regarding filter-bank realization, initial transceiver training, adaptive equalization, and timing recovery are discussed. Finally, simulation results of the performance achieved by FMT modulation for very high-speed digital subscriber line systems, where upstream and downstream signals are separated by frequency-division duplexing, are presented and compared with DMT modulation.

Patent
02 May 2002
TL;DR: In this article, adaptive reuse schemes are provided wherein the available system resources may be dynamically and/or adaptively partitioned and allocated to the cells based on a number of factors such as the observed interference levels, loading conditions, system requirements, and so on.
Abstract: Techniques to partition and allocate the available system resources among cells in a communication system, and to allocate the resources in each cell to terminals for data transmission on the uplink. In one aspect, adaptive reuse schemes are provided wherein the available system resources may be dynamically and/or adaptively partitioned and allocated to the cells based on a number of factors such as the observed interference levels, loading conditions, system requirements, and so on. A reuse plan is initially defined and may be redefined to reflect changes in the system. In another aspect, the system resources may be partitioned such that each cell is allocated a set of channels having different performance levels. In yet another aspect, terminals in each cell are scheduled for data transmission (e.g., based on their priority or load requirements) and assigned channels based on their tolerance to interference and the channels' performance.

Journal ArticleDOI
TL;DR: It is shown that a moderate directivity will be sufficient for high-speed infrared communication in typical indoor scenarios and it is confirmed that a K-factor /spl ges/13 dB is required also in infrared wireless links in order to support distortionless data transmission beyond 100 Mbit/s.
Abstract: A simple analytical model of the wireless infrared communication channel in indoor environments is presented. The infrared signal is modeled as the combination of a diffuse component and a line-of-sight (LOS) or direct component. For the diffuse component alone, the properties of the channel are found using Ulbricht's integrating sphere. When a LOS component is also present, the transfer function depends upon the Rician factor K given by the ratio of the electrical power in the LOS and diffuse signals after the detector. For small K, the transfer function shows notches down to low frequencies, but due to the nature of light never for zero frequency. We confirm that a K-factor /spl ges/13 dB is required also in infrared wireless links in order to support distortionless data transmission beyond 100 Mbit/s. Increasing the directivity at the receiver and/or at the transmitter improves the effective value of K. Here, we show that a moderate directivity will be sufficient for high-speed infrared communication in typical indoor scenarios.

Proceedings ArticleDOI
23 Sep 2002
TL;DR: The results show that RBUDP performs extremely efficiently over high speed dedicated networks and the model provided is able to provide good estimates of its performance.
Abstract: High speed bulk data transfer is an important part of many data-intensive scientific applications. This paper describes an aggressive bulk data transfer scheme, called Reliable Blast UDP (RBUDP), intended for extremely high bandwidth, dedicated- or Quality-of-Service-enabled networks, such as optically switched networks. This paper also provides an analytical model to predict RBUDP's performance and compares the results of our model against our implementation of RBUDP. Our results show that RBUDP performs extremely efficiently over high speed dedicated networks and our model is able to provide good estimates of its performance.

Patent
05 Dec 2002
TL;DR: In this paper, a communication system including a transmitter, a receiver, and a serial link, in transmitted from the transmitter to the receiver, is described, where packets of encoded audio data are transmitted over each of one of more channels of the link during data islands between bursts of encoded video data.
Abstract: A communication system including a transmitter (1’), a receiver (2’), and a serial link, in transmitted from the transmitter to the receiver. The serial link can but need not be a TMDS or TMDS-like link. In typical embodiments, packets of encoded audio data are transmitted over each of one of more channels of the link during data islands between bursts of encoded video data. Other aspects of the invention are transmitters for use in encoding data for transmission over a serial link, receivers for receiving such data, and methods for sending encoded data over a serial link.

Journal ArticleDOI
TL;DR: It can be shown that OFDM-CDM outperforms conventional OFDM with respect to bit error rate (BER) performance and bandwidth efficiency.
Abstract: In this paper, orthogonal frequency-division multiplexing-code-division multiplexing (OFDM-CDM) is presented and investigated as alternative to conventional OFDM for high rate data transmission. An additional multipath diversity gain can be obtained with OFDM-CDM by spreading each data symbol in frequency and time. The optimum reliability information for the Viterbi (1979) decoder is derived for OFDM-CDM systems, and the tradeoff between spreading and channel coding in OFDM systems is presented. By using efficient interference cancellation or joint detection techniques, it can be shown that OFDM-CDM outperforms conventional OFDM with respect to bit error rate (BER) performance and bandwidth efficiency.

Journal ArticleDOI
17 Nov 2002
TL;DR: A new linear processing architecture is proposed, which reduces the effect of incorrect CSI at the transmitter and outperforms simpler systems that do not require CSI atThe transmitter at low velocities.
Abstract: The performance of a system using singular value decomposition (SVD) over a multiple-input multiple-output (MIMO) channel is dependent on the accuracy of the channel state information (CSI) at the transmitter and the receiver. In time division duplex (TDD) systems, the channel is reciprocal, hence the CSI can be retrieved through estimation of pilot symbols and applied to transmission. However, for a time-varying channel, the estimated CSI at the transmitter is incorrect due to an inherent delay between the estimation of the CSI and the transmission of data. A typical system employing SVD suffers degradation in capacity when incorrect CSI is used to transmit data. This paper proposes a new linear processing architecture, which reduces the effect of incorrect CSI at the transmitter. No additional pilot signals are required. It is shown at terminal velocity of 2 m.s/sup -1/ for the Hiperlan 2 standards, that the proposed architecture has a capacity of one bit lower than the theoretical channel capacity. At low velocities, this architecture outperforms (in terms of capacity) simpler systems that do not require CSI at the transmitter.

Patent
Takuya Ishida1, Yoshiyuki Kamihara1
14 May 2002
TL;DR: In this article, the end of a data phase (data transport: transfer of all the data) during an OUT transaction is determined on condition that data transmission (DMA transfer) through EBUS (a second bus) has ended and also an Empty signal has gone active, indicating that a data storage area has become empty.
Abstract: A data transfer control device using USB (a first bus), the end of a data phase (data transport: transfer of all the data) during an OUT transaction is determined on condition that data transmission (DMA transfer) through EBUS (a second bus) has ended, and the end of a data phase during an IN transaction is determined on condition that data reception through EBUS has ended and also an Empty signal has gone active, indicating that a data storage area has become empty. A counter that counts the data size is provided on the EBUS side. If data reception through EBUS ends and the size of data remaining in the data storage area is less than the maximum packet size, a short packet in the data storage area is transmitted automatically through USB and an interrupt is used to notify the firmware of the presence of the short packet.

Journal ArticleDOI
TL;DR: By simulation and actual measurements using "reference design" prototype commercial powerline products, it is shown that the HomePlug MAC and PHY layers can guarantee QoS for real-time communications, supporting delay-sensitive data streams for smart home applications.
Abstract: Low voltage electrical wiring has largely been dismissed as too noisy and unpredictable to support high-speed communication signals. Advances in communication and modulation methodologies as well as in adaptive digital signal processing and error detection and correction have spawned novel protocols capable of supporting power line communication networks at speeds comparable to wired LANs. We motivate the use of power line LANs as a basic infrastructure for building integrated smart homes, wherein information appliances ranging from simple control or monitoring devices to multimedia entertainment systems are seamlessly interconnected by the very wires that provide them electricity. By simulation and actual measurements using "reference design" prototype commercial powerline products, we show that the HomePlug MAC and PHY layers can guarantee QoS for real-time communications, supporting delay-sensitive data streams for smart home applications.

Journal ArticleDOI
TL;DR: A key contribution of this paper is a simple formula for the mean spectral efficiency in terms of the propagation exponent, mean signal-to-noise ratio at the cell boundary, number of antennas, and type of coding, which highlights the potential benefits of multiple transmissions combined with adaptive techniques.
Abstract: We present a general framework to quantify the data throughput capabilities of a wireless communication system when it combines: (1) multiple transmit signals; (2) adaptive modulation for each signal; and (3) adaptive array processing at the receiver. We assume a noise-limited environment, corresponding to either an isolated cell or a multicell system whose out-of-cell interference is small compared with the thermal noise. We focus on the user data throughput, in bits per second/Hertz (bps/Hz), and its average over multipath fading, which we call the user spectral efficiency. First, an analysis method is developed to find the probability distribution and mean value of the spectral efficiency over the user positions and shadow fadings, both as a function of user distance from its serving base station and averaged over the cell coverage area. We assume fading conditions and receiver processing that lend themselves to closed-form analysis. The resulting formulas are simple and straightforward to compute, and they provide a number of valuable insights. Next, we run Monte Carlo simulations, both to confirm the analysis and to treat cases less amenable to simple analysis. A key contribution of this paper is a simple formula for the mean spectral efficiency in terms of the propagation exponent, mean signal-to-noise ratio at the cell boundary, number of antennas, and type of coding. Under typical propagation conditions, the mean spectral efficiency using three transmit and three receive antennas ranges from 19.2 bps/Hz (uncoded) to 26.8 bps/Hz (ideally coded), highlighting the potential benefits of multiple transmissions combined with adaptive techniques. This is much higher than the spectral efficiencies for a link using a single transmitter and a threefold receive diversity under the same conditions, where the range is from 8.77 bps/Hz to 11.4 bps/Hz. Moreover, the latter results are not nearly as practical to achieve, as they can for large signal constellations that would be highly vulnerable to impairments.

Journal ArticleDOI
TL;DR: This work proposes a method for grouping antennas and codes in such a way that the inherent diversity is retained, while the complexity is greatly reduced, in MIMO-OFDM systems operating in frequency-selective channels.
Abstract: We consider the capacity of multiple-input-multiple-output (MIMO) systems that use OFDM as the modulation format. We point out a basic equivalence between antennas and OFDM-tones. This similarity immediately allows us to essentially reuse all space-time codes designed for flat-fading channels in MIMO-OFDM systems operating in frequency-selective channels. An optimum code would thus code across all antennas and tones (as well as time) simultaneously. Since this can become very complex, we propose a method for grouping antennas and codes in such a way that the inherent diversity is retained, while the complexity is greatly reduced. Capacity computations between the full-complexity and the reduced-complexity systems illustrate this tradeoff.

Patent
23 Apr 2002
TL;DR: In this paper, a client configures a portable computing device to communicate with a distributor using a data transfer communication protocol, the information is transmitted from the distributor to the portable computing devices.
Abstract: A method of transmitting information to a portable computing device comprises, using a first communication protocol, transmitting a client to the portable computing device. The client configures the portable computing device to communicate with a distributor using a data transfer communication protocol. Using the data transfer communication protocol, the information is transmitted from the distributor to the portable computing device. Transmitting the information includes generating, at the distributor, a polling signal, detecting, at the distributor, an acknowledgement signal generated, in response to the polling signal, by the portable computing device, and generating, in response to the acknowledgement signal, a broadcast signal incorporating the information.

Journal ArticleDOI
TL;DR: Experimental results show that simultaneously adjusting the source coding and transmission power is more energy efficient than considering these factors separately.
Abstract: We consider a situation where a video sequence is to be compressed and transmitted over a wireless channel. Our goal is to limit the amount of distortion in the received video sequence, while minimizing transmission energy. To accomplish this goal, we consider error resilience and concealment techniques at the source coding level, and transmission power management at the physical layer. We jointly consider these approaches in a novel framework. In this setting, we formulate and solve an optimization problem that corresponds to minimizing the energy required to transmit video under distortion and delay constraints. Experimental results show that simultaneously adjusting the source coding and transmission power is more energy efficient than considering these factors separately.

Patent
08 Jan 2002
TL;DR: In this article, the authors propose load balancing data streams at the initiation of a large data transfer and dynamically controlling the number of data streams utilized as conditions within the infrastructure environment change.
Abstract: Available bandwidth utilization during transfer of large files over a TCP/IP network is improved by load balancing data streams at the initiation of a large data transfer and dynamically controlling the number of data streams utilized as conditions within the infrastructure environment change. Software code running in both the client and the server optimizes the number of data streams utilized for each data transfer. A determination is quickly made of the optimum number of data streams for a particular data file transfer in the early stage of transmission. During the first few seconds of the transfer, an initial number of data streams, which is one unless otherwise specified or determined, is used to transmit one or more file segments, each on a different data stream, immediately followed by a second initial number of data streams, which is at least two greater than the initial number of data streams, is used to transmit another portion of the large data file. During each transmission, individual and aggregate transmission bandwidths are determined. The transfer proceeds with the second number of data streams if its aggregate transmission bandwidth is substantially greater than that of the initial number of data streams. Thereafter, during continuous transfer of the large data file, a weighted average of aggregate transmission bandwidth is periodically determined and compared for the active set of data streams. Responsive to a determination that the latest aggregate transmission bandwidth is significantly different from the previous aggregate transmission bandwidth, the number of data streams is modified as conditions in the infrastructure dictate.

Journal ArticleDOI
TL;DR: It is shown that multichannel digital transmission can be implemented on an ensemble of communicating molecules relying exclusively on the interplay of optical inputs and optical outputs.
Abstract: In present telecommunication networks, information transfer relies on the interplay of optical and electrical signals. Data are communicated optically but processed electronically. Methods to maintain the propagating signals solely at the optical level must be developed to overcome the transmission capacities and speed limits imposed by the electronic components. We have demonstrated that molecular switches can be used to gate optical signals in response to optical signals. We have realized a simple optical network consisting of three light sources, one cell containing a solution of three fluorescent molecules, one cell containing a solution of a three-state molecular switch and a detector. The light emitted by the three fluorophores is absorbed by the three states of the molecular switch. Using this simple operating principle, we have shown that multichannel digital transmission can be implemented on an ensemble of communicating molecules relying exclusively on the interplay of optical inputs and optical...

Patent
Ki Jun Kim1, Young Cho Kim1, Young Jo Lee1, Jong Hyae Ahn1, Yong Woo Yun1, Young Jun Kim1 
11 Feb 2002
TL;DR: In this article, the data transmission rate on the reverse link in a mobile communications system is controlled by determining an interference level at a base station due to signals from all mobile stations served by the base station, and determining a transmission energy level required for each mobile station.
Abstract: The data transmission rate on the reverse link in a mobile communications system is controlled by determining an interference level at a base station due to signals from all mobile stations served by the base station, and determining a transmission energy level required for each mobile station. The interference level is compared with the transmission energy level to obtain a comparison result for each mobile station, and each mobile adjusts its data transmission rate based upon the comparison result, which is sent via a common channel on a forward link to each mobile station in a dedicated manner. Thereafter, packet data is transmitted on the reverse link in accordance with the adjusting so that data throughput can be maximized.

Patent
26 Apr 2002
TL;DR: In this paper, a technique for optimizing the delivery of a multiplicity of advertisements and other programming is providing by trading off full-motion video for other forms of high quality still images, text, graphics and audio.
Abstract: A technique for optimizing the delivery of a multiplicity of advertisements and other programming (402) is providing by trading off full-motion video (404) for other forms of high quality still images, text, graphics and audio (406). By creating a group of synchronized digital programming components (408), for example, still-frame video, audio, graphics, text, animation, and media objects, which combined (416) utilize less bandwidth than a standard digital programming segment of full-motion video with CD quality audio, a greater number of differentiable programming content options can be made available in the digital transmission stream (418). Because of the greatly expanded amount of differentiable content that can be created using the bandwidth tradeoff techniques, greater precision in targeting particular content, such as advertisements, to particular users is possible. The invention also contemplates the system requirements, both hardware and software, for a digital programming transmission center and for user's receiver, necessary to implement the bandwidth tradeoff methodology.

Patent
29 Jan 2002
TL;DR: In this paper, a system and methodology for the acquisition of medical data from multiple, at-home patient measurement devices transfers the data via telephone communications to a remotely accessed data management and display system such as a Web-based data management system.
Abstract: A system and methodology for the acquisition of medical data from multiple, at-home patient measurement devices transfers the data via telephone communications to a remotely accessed data management and display system such as a Web-based data management system. The measurement device, which supports two-way communications between the patient and the database system, is extensible to support multiple plug-in medical devices and devices for patient input or identification. Collection of data is mediated through an interface device that is connected via a digital link (serial, network, or digital RF link) to single or multiple patient measurement devices. This interface device is connected to a network via wide area network means including standard phone lines. In the preferred embodiment, data transfer is mediated through pervasive DTMF phone networks. Although DTMF is the preferred format, alternative analog or digital audio tone formats may be used.