Showing papers on "Data transmission published in 2007"

Survey of automatic modulation classification techniques: classical approaches and new trends

Abstract: The automatic recognition of the modulation format of a detected signal, the intermediate step between signal detection and demodulation, is a major task of an intelligent receiver, with various civilian and military applications. Obviously, with no knowledge of the transmitted data and many unknown parameters at the receiver, such as the signal power, carrier frequency and phase offsets, timing information and so on, blind identification of the modulation is a difficult task. This becomes even more challenging in real-world scenarios with multipath fading, frequency-selective and time-varying channels. With this in mind, the authors provide a comprehensive survey of different modulation recognition techniques in a systematic way. A unified notation is used to bring in together, under the same umbrella, the vast amount of results and classifiers, developed for different modulations. The two general classes of automatic modulation identification algorithms are discussed in detail, which rely on the likelihood function and features of the received signal, respectively. The contributions of numerous articles are summarised in compact forms. This helps the reader to see the main characteristics of each technique. However, in many cases, the results reported in the literature have been obtained under different conditions. So, we have also simulated some major techniques under the same conditions, which allows a fair comparison among different methodologies. Furthermore, new problems that have appeared as a result of emerging wireless technologies are outlined. Finally, open problems and possible directions for future research are briefly discussed.

Relay-Assisted Free-Space Optical Communication

Abstract: In this paper, we present relay-assisted transmission as a powerful fading mitigation tool for free-space optical systems operating in atmospheric turbulence channels. We study both serial (i.e., multi-hop transmission) and parallel (i.e., cooperative diversity) relaying encoupled with amplify-and-forward and decode-and-forward modes. We consider an aggregated channel model which takes into account both path-loss and turbulence-induced log-normal fading. Since fading variance is distance-dependent in free-space optical systems, relay-assisted transmission takes advantage of the resulting shorter hops and yields significant performance improvements. We derive outage probability of the relaying schemes under consideration which are further confirmed through Monte-Carlo simulations. Our outage probability analysis demonstrates that an impressive performance improvement of 18.5 dB is possible with the use of a single relay at a target outage probability of 10-6.

The Human Body Characteristics as a Signal Transmission Medium for Intrabody Communication

Abstract: The human body characteristics as a signal transmission medium are studied for the application to intrabody communication. The measurements of the body channel cover the frequency range from 100 kHz to 150 MHz and the distance on the body up to 1.2 m. A distributed RC model is developed to analyze the large variation of the channel properties according to the frequency and channel length. The simulation results using the channel model match well with the measurements in both the frequency and time domains. The effect of the ground plane to the body channel transceivers is also investigated and an empirical formula for the minimum ground size is obtained. Finally, the amount of the electromagnetic radiation due to the body antenna effect is measured. With regards to the Federal Communications Commission regulations, the proper frequency range for the intrabody communication is determined to satisfy given bit error rate requirements

High bandwidth data transport system

Abstract: The present invention provides for a methods, system, and apparatus relating to data transmission. One method of the present invention includes representing data using at least one ultra wideband pulse, sending the at least one ultra wideband pulse over an electrically conductive guided media, and recovering the data from the at least one ultra wideband pulse. The present invention can be used in conjunction with telephony applications, cable TV applications, power line applications, fiber optic applications, and data bus applications.

Key Enabling Technologies for Optical–Wireless Networks: Optical Millimeter-Wave Generation, Wavelength Reuse, and Architecture

Abstract: The integration of optical and wireless systems is considered to be one of the most promising solutions for increasing the existing capacity and mobility as well as decreasing the costs in next-generation optical access networks. In this paper, several key enabling technologies for hybrid optical-wireless access networks are described, including optical millimeter-wave (mm-wave) generation, upconversion, and transmission in a downlink direction, and full-duplex operation based on wavelength reuse by using a centralized light source in an uplink direction. By employing these enabling technologies, we design and experimentally demonstrate an optical-wireless testbed that is simultaneously delivering wired and wireless services in the integrated optical-wireless and wavelength-division-multiplexing passive-optical-network access networks. The actual applications consisting of 270-Mb/s uncompressed standard-definition TV signal and 2.5-Gb/s data channels for downstream are successfully transmitted over a 25-km fiber and a 10.2-m indoor wireless link with less than a 1.5-dB power penalty. The results show that this integrated system is a practical solution to deliver superbroadband information services to both stationary and mobile users.

Technical Review on Chinese Digital Terrestrial Television Broadcasting Standard and Measurements on Some Working Modes

Abstract: Technical details of the recently announced Chinese Digital Terrestrial Television Broadcasting Standard which defines the physical layer transmission protocol including the frame structure, channel coding and modulation schemes are discussed in this paper. The major differences between Chinese DTV standard in multi-carrier working mode and DVB-T standard, all occupying the same 8 MHz baseband bandwidth, are addressed. The measurement results of several working modes showing satisfactory receiving performance of high and standard definition TV signals under both indoor and outdoor environments for the fixed and mobile reception are also presented

OFDM Visible Light Wireless Communication Based on White LEDs

Abstract: White LEDs are set to penetrate many areas of everyday life. An interesting property of these devices (in addition to their lightening capabilities) is that they can be utilised for data transmission. In the past, primarily OOK (on-off keying) has been used for digital data modulation of such devices. OOK imposes limitations on the achievable data rates. Therefore, in this paper OFDM is considered in combination with higher order modulation schemes. A hardware demonstrator with an entire link chain (transmitter and receiver) is developed and measured BER (bit error ratio) results are reported. The system uses pilot sub-carriers to correct frequency synchronisation errors, training sequences for channel estimation and time synchronisation routines. Forward error correction (FEC) coding is used. It is shown that for COFDM (coded OFDM) with QPSK (quadrature phase shift keying) modulation and a single LED, a BER of 2 times 10-5 is achieved for a distance of 90 cm between transmitter and receiver.

Distributed MMSE Relay Strategies for Wireless Sensor Networks

Abstract: A fundamental task in a wireless sensor network is to broadcast some measured data from an origin sensor to a destination sensor. Since the sensors are typically small, power limited, and low cost, they are only able to broadcast low-power signals. As a result, the propagation loss from the origin to the destination nodes can attenuate the signals beyond detection. One way to deal with this problem is to pass the transmitted signal through relay nodes. In this paper we propose and study two-hop multisensor relay strategies that achieve minimum mean-square-error (MSE) performance subject to either local or global power constraints. The capacity of the resulting relay link and its diversity order are studied. The effect of channel uncertainties on system performance is examined and a modified relay scheme is proposed.

Data Transmission And Retransmission

Abstract: A method transmits data. The method includes transmitting a series of data unit, receiving a retransmission request indicating a plurality of corrupt data units in the transmitted data units which were not received correctly, and retransmitting the corrupted data units.

Cross-Layer Packetization and Retransmission Strategies for Delay-Sensitive Wireless Multimedia Transmission

Abstract: Existing wireless networks provide dynamically varying resources with only limited support for the quality of service required by the bandwidth-intense, loss-tolerant and delay-sensitive multimedia applications. This variability of resources does not significantly impact delay insensitive data transmission (e.g., file transfers), but has considerable consequences for multimedia applications. Recently, the research focus has been to adapt existing algorithms and protocols at the lower layers of the protocol stack to better support multimedia transmission applications and conversely, to modify application layer solutions to cope with the varying wireless networks resources. In this paper, we show that significant improvements in wireless multimedia performance can be obtained by deploying a joint application-layer adaptive packetization and prioritized scheduling and MAC-layer retransmission strategy. We deploy a state-of-the-art wavelet coder for the compression of the video data that enables on-the-fly adaptation to changing channel conditions and inherent prioritization of the video bitstream. We pose the cross-layer problem as a distortion minimization given delay constraints and derive analytical solutions by modifying existing joint source-channel coding theory aimed at fulfilling rate, rather than delay, constraints. We also propose real-time algorithms that explicitly consider the available information about previously transmitted packets. The obtained results show significant improvements in terms of video quality as opposed to ad-hoc optimizations currently deployed, while the complexity associated with performing this optimization in real time, i.e., at transmission time, is limited

Delay/Fault-Tolerant Mobile Sensor Network (DFT-MSN): A New Paradigm for Pervasive Information Gathering

Abstract: This paper focuses on the delay/fault-tolerant mobile sensor network (DFT-MSN) for pervasive information gathering. We develop simple and efficient data delivery schemes tailored for DFT-MSN, which has several unique characteristics, such as sensor mobility, loose connectivity, fault tolerability, delay tolerability, and buffer limit. We first study two basic approaches, namely, direct transmission and flooding. We analyze their performance by using queuing theory and statistics. Based on the analytic results that show the trade-off between data delivery delay/ratio and transmission overhead, we introduce an optimized flooding scheme that minimizes transmission overhead in flooding. Then, we propose two simple and effective DFT-MSN data delivery schemes, namely, the replication-based efficient data delivery scheme (RED) and the message fault tolerance-based adaptive data delivery scheme (FAD). The RED scheme utilizes the erasure coding technology in order to achieve the desired data delivery ratio with minimum overhead. It consists of two key components for data transmission and message management. The former makes the decision on when and where to transmit data messages according to the delivery probability, which is the likelihood that a sensor can deliver data messages to the sink. The latter decides the optimal erasure coding parameters (including the number of data blocks and the needed redundancy) based on its current delivery probability. The FAD scheme employs the message fault tolerance, which indicates the importance of the messages. The decisions on message transmission and dropping are made based on fault tolerance for minimizing transmission overhead. The system parameters are carefully tuned on the basis of thorough analyses to optimize network performance. Extensive simulations are carried out for performance evaluation. Our results show that both schemes achieve a high message delivery ratio with acceptable delay. The RED scheme results in lower complexity in message and queue management, while the FAD scheme has a lower message transmission overhead.

Applying CDMA Technique to Network-on-Chip

Abstract: The issues of applying the code-division multiple access (CDMA) technique to an on-chip packet switched communication network are discussed in this paper. A packet switched network-on-chip (NoC) that applies the CDMA technique is realized in register-transfer level (RTL) using VHDL. The realized CDMA NoC supports the globally-asynchronous locally-synchronous (GALS) communication scheme by applying both synchronous and asynchronous designs. In a packet switched NoC, which applies a point-to-point connection scheme, e.g., a ring topology NoC, data transfer latency varies largely if the packets are transferred to different destinations or to the same destination through different routes in the network. The CDMA NoC can eliminate the data transfer latency variations by sharing the data communication media among multiple users concurrently. A six-node GALS CDMA on-chip network is modeled and simulated. The characteristics of the CDMA NoC are examined by comparing them with the characteristics of an on-chip bidirectional ring topology network. The simulation results reveal that the data transfer latency in the CDMA NoC is a constant value for a certain length of packet and is equivalent to the best case data transfer latency in the bidirectional ring network when data path width is set to 32 bits.

Radio transmission system and packet transmission terminal

Abstract: PROBLEM TO BE SOLVED: To prevent loss of data packets by rationalizing the transmission amount of the data packets. SOLUTION: A radio transmission system includes: a data packet transmission part 11 which transmits data packets to a packet reception terminal 2 by using a satellite line; an own station data packet reception part 12 which receives data packets transmitted from the data packet transmission part 11 and turned by a satellite; and a line band calculation part 13 which calculates an available band of a radio line from the reception quality of data packets received by the own station data packet reception part 12. A data transmission amount control part 18 controls the transmission amount of data packets transmitted from the data packet transmission part 11, in accordance with the available band calculated by the line band calculation part 13. COPYRIGHT: (C)2009,JPO&INPIT

Method and apparatus for distributing usb hub functions across a network

Abstract: A method and related apparatuses for data transmission between a host computer and one or a plurality of USB compliant peripheral devices over a data communications network is provided which operates in the presence of transmission delays greater than that normally allowed in the USB specification. The host computer is connected to a local extender device which, in turn, is connected to one or a plurality of remote extender devices through the data communications network. The remote extender devices are, in turn, connected to a plurality of conventional USB peripheral devices. Data between the host computer and peripheral devices is stored and processed in the local and remote extender devices in order to allow the host computer and the USB peripheral devices to operate with greater than normally allowed time delays. In particular, the invention is of most utility when the round-trip transmission delay between the host computer and the USB peripheral device exceeds 1 microsecond.

Data Transmission by FrequencyDivision Multiplexing Using the Discrete Fourier Transform

Abstract: The Fourier transform data communication system is a realization of frequency-division multiplexing (FDM) in which discrete Fourier transforms are computed as part of the modulation and demodulation processes. In addition to eliminating the banks of subcarrier oscillators and coherent demodulators usually required in FDM systems, a completely digital implementation can be built around a special-purpose computer performing the fast Fourier transform. In this paper, the system is described and the effects of linear channel distortion are investigated. Signal design criteria and equalization algorithms are derived and explained. A differential phase modulation scheme is presented that obviates any equalization.

Resource allocation to support single-user and multi-user mimo transmissions

Abstract: Techniques for supporting MIMO transmission are described. Users are classified into a first group of users to be scheduled individually for MIMO transmission and a second group of users that can be scheduled together for MIMO transmission. Transmission resources are allocated to the first and second groups, e.g., based upon various criteria such as the number of users in each group, data requirements of the users, total loading for each group, etc. The transmission resources may be hybrid automatic retransmission (HARQ) interlaces, frequency channels, time frequency resources, etc. The resource allocation may be semi-static. The transmission resources allocated to each group are used for data transmission on the downlink and/or uplink for the users in the group. HARQ with blanking may be used for data transmission for the users in the first group. HARQ without blanking may be used for data transmission for the users in the second group.

A 0.2-mW 2-Mb/s Digital Transceiver Based on Wideband Signaling for Human Body Communications

Abstract: This paper presents a low-power wideband signaling (WBS) digital transceiver for data transmission through a human body for body area network applications. The low-power and highspeed human body communication (HBC) utilizes a digital transceiver chip based on WBS and adopts a direct-coupled interface (DCI) which uses an electrode of 50-Omega impedance. The channel investigation with the DCI identities an optimum channel bandwidth of 10 kHz to 100 MHz. The WBS digital transceiver exploits a direct digital transmitter and an all-digital clock and data recovery (CDR) circuit. To further reduce power consumption, the proposed CDR circuit incorporates a low-voltage digitally-controlled oscillator and a quadratic sampling technique. The WBS digital transceiver chip with a 0.25-mum standard CMOS technology has 2-Mb/s data rate at a bit error rate of 1.1 times 10-7, dissipating only 0.2 mW from a 1-V supply generated by a 1.5-V battery.

An EM-Based Forward-Backward Kalman Filter for the Estimation of Time-Variant Channels in OFDM

Abstract: Orthogonal frequency division multiplexing (OFDM) combines the advantages of high achievable rates and relatively easy implementation. However, for proper recovery of the input, the OFDM receiver needs accurate channel information. In this paper, we propose an expectation-maximization algorithm for joint channel and data recovery in fast fading environments. The algorithm makes a collective use of the data and channel constraints inherent in the communication problem. This comes in contrast to other works which have employed these constraints selectively. The data constraints include pilots, the cyclic prefix, and the finite alphabet restriction, while the channel constraints include sparsity, finite delay spread, and the statistical properties of the channel (frequency and time correlation). The algorithm boils down to a forward-backward Kalman filter. We also suggest a suboptimal modification that is able to track the channel and recover the data with no latency. Simulations show the favorable behavior of both algorithms compared to other channel estimation techniques.

Receiver and integrated AM-FM/IQ demodulators for gigabit-rate data detection

Abstract: Provision of gigabit-rate data transmission over wireless radio links, using carrier frequencies in the millimeter-wave range (>30 GHz). More specifically, a circuit for detection of amplitude-shift keyed (ASK) or other amplitude modulations (AM) which can be easily incorporated into an integrated circuit receiver system is described, making the receiver capable of supporting both complex IQ modulation schemes and simpler, non-coherent on-off or multiple-level keying signals. Several novel radio architectures are also described which, with the addition of a frequency discriminator network, have the capability of handling frequency shift keyed (FSK) or other frequency modulations (FM), as well as AM and complex IQ modulation schemes. These radio architectures support this wide variety of modulations by efficiently sharing detector hardware components. Disclosed herein are architecture for supporting both quadrature down-conversion and ASK/AM, ASK/AM detector circuit details, AM-FM detector architecture, and an AM-FM/IQ demodulator system and FSK/FM detector circuit details.

Apparatus and method for transmitting/receiving data in a multi-antenna system, and system using the same

Abstract: A data reception apparatus and method for generating and transmitting feedback information in a multi-antenna system using grouped antennas, and a data transmission apparatus and method for transmitting a data stream of a user according to a transmission mode selected depending on the feedback information is disclosed. The reception apparatus generates feedback information depending on maximum channel quality information, an antenna group index associated with the maximum channel quality information, rank information, and remaining channel quality information associated with the rank information, and transmits the feedback information to the transmission apparatus. The transmission apparatus selects one of a multi-user mode and a single-user mode as a transmission mode depending on the feedback information and transmits a data stream of a user via multiple antenna groups or one antenna group, according to the selected transmission mode.

An Introduction to Adaptive QAM Modulation Schemes for Known and Predicted Channels

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 is changing with the channel quality. Most applications require a certain maximum BER and there is normally no reason for providing a smaller BER than required. An adaptive modulation scheme, on the contrary, can be designed to have a BER which is constant for all channel SNRs. The spectral efficiency of the fixed modulation is constant, while it, in general, will increase with increasing channel SNRs for the adaptive scheme. This in effect means that the average spectral efficiency of the adaptive scheme is improved, while at the same time the BER is better suited to the requirement of the application. Thus, the adaptive link becomes much more efficient for data transmission. The major disadvantage is that the transmitter needs to know the channel SNR such that the best suitable modulation is chosen and the receiver must be informed on the used modulation in order to decode the information. This leads to an increased overhead in the system as compared with a fixed modulation system. In this paper, we introduce adaptive modulation systems by presenting some of the simpler adaptive quadrature amplitude modulation schemes and their performance for both perfectly known and predicted channels.

Brightness Control Methods for Illumination and Visible-Light Communication Systems

Abstract: We have developed two brightness control methods for illumination and visible-light communication systems. One method is pulse width modulation (PWM), the other is changing modulation depth. Using these proposed methods, we can achieve both dimmer i.e. brightness control and wireless communication at the same time. We discussed the relationship between PWM frequency, LED brightness, and communication performance. The results show that we can control brightness from 0% to 87.5% when we use PWM and data transmission possible when PWM frequency is high enough. Brightness can be controlled from 0% to 100% and communication performance is better than that of PWM when we change modulation depth.

Active on-patient sensor, method and system

Abstract: A sensor (which could be detachable) to sense a condition (including pressure from body weight or moisture from incontinence; applied by adhering to skin of a human body or by putting a diaper on the human body, for example), a signal processing circuit, a periodic or continuous transmitter, and a power supply (typically including a battery) are associated with a flexible substrate in low profile enabling disposition adjacent the human body. A transmitter antenna is on the substrate. Insulator film between battery contacts and a switch-and-transistor combination are two power-on techniques. A bedside monitor, a transceiver configured to receive signals from and transmit signals to the bedside monitor, and a computer connected with the transceiver can be included. Other features include: notification signaling; differently responsive antennas; unique identification; low battery detection; anti-collision transmission; patient protocol scheduling; local data transfer from the bedside monitor; and out-of-range transmission detection.

Methods, systems and apparatus for multi-purpose metering

Abstract: Methods and apparatus for multi-purpose metering are disclosed. An example method includes acquiring a rate of data transfer to/from the monitored location and comparing the acquired rate of data transfer to a threshold. The example method also includes setting at least one media monitoring device in a first bandwidth mode when the acquired rate of data transfer exceeds the threshold, and setting the at least one media monitoring device in a second bandwidth mode when the acquired rate of data transfer is below the threshold.

Send-On-Delta Sensor Data Transmission With A Linear Predictor

Abstract: This paper is concerned with sensor data transmission strategy. The main focus of the paper is how to reduce the number of sensor data transmission while maintaining the difference between the estimated sensor value and the real sensor value. The proposed method could be used in sensor networks and networked control systems, where number of transmission should be minimal. A linear predictor is used to predict sensor values and sensor data are transmitted if the difference between the predicted sensor value and the real sensor value exceeds the specified limit. An analytic upper bound of the mean rate of messages is provided. Through simulation, it is shown that the number of transmission could be significantly reduced compared with the periodic sampling and the conventional send-on-delta method.

Providing antenna diversity in a wireless communication system

Abstract: Systems and methodologies are described that facilitate cycling across antennas for channel quality information (CQI) computation and data transmission in a multiple-input multiple-output (MIMO) wireless communication environment. Pilots can be obtained by a wireless terminal. Further, virtual antennas that can be supported by a channel can be identified based upon an analysis of the pilots. Moreover, CQI computations can be effectuated for each of the supported virtual antennas; thereafter, the CQI data can be sent to a base station for data transmission scheduling. Additionally, the base station can schedule transmission based upon the CQI data and/or fairness considerations. When scheduled, data transmission can occur by cycling across the supported virtual antennas.

Data transmission system, data transmission device, management server device, and data transmission method

Abstract: PROBLEM TO BE SOLVED: To provide a data transmission system which enables a user to leave a data transmission device before the completion of data transmission regardless of presence/absence of repayment due to occurrence of a communication error when collecting a charge to perform data transmission by the data transmission device. SOLUTION: The data transmission device (illustrated as an MFP 1) includes a data transmission part (illustrated as a FAX transmission/reception part 12) for transmitting data, a price reception part 11 for receiving the price for FAX data transmission in the FAX transmission/reception part 12, a notification destination input part (illustrated as a notification destination input processing part 10b and a display/operation panel 13) for inputting the notification destination of the user, and a FAX transmission error detection part 10a for detecting a communication error during FAX data transmission. When a communication error is detected in the FAX transmission error detection part 10a, the system provided with the MFP 1 transmits repayment information for repayment of the price for FAX data transmission, during which the communication error has occurred, to the notification destination input by the notification destination input part. COPYRIGHT: (C)2009,JPO&INPIT

High-Resistance Faults on Two Terminal Parallel Transmission Line: Analysis, Simulation Studies, and an Adaptive Distance Relaying Scheme

Abstract: Performance of conventional nonpilot distance relay is affected by ground fault resistance, prefault system conditions, mutual effects of parallel lines and shunt capacitance influences The work presented in this paper addresses the problems encountered by conventional non pilot distance relay when protecting two terminal parallel transmission lines One of the key points of this paper is the detailed analysis of the apparent impedance as seen from the relaying point taking into account the effects of transmission line parameter uncertainties, mutual effects of parallel lines for simple and more complex configuration, shunt capacitance influences and variations in the system external to the protected line Based on extensive computer simulations of the infeed/outfeed, fault resistance, mutual coupling and shunt capacitance effects on the relay characteristics, an adaptive digital distance relaying scheme is proposed using radial basis function neural network which provides more efficient approach for training, computation, adaptation and tripping than the conventional feed forward network using back propagation algorithm In addition, the proposed adaptive scheme improves the performance of distance relay for double-circuit lines using modified compensation factor Moreover, the scheme does not require separate communication channel for data transmission The results of computer simulation show the improvement of sensitivity and selectivity of the relay

Data transmission apparatus and method

Abstract: A data transmission apparatus comprises an estimation device to estimate a transmission condition of the transmission channel in the transmitter based on at least Jitter information or a packet loss rate obtained from the receiver, and a controller to change at least one of a bit rate of transmission data and a error resilience level according to the estimated transmission condition.

Optimal Transmission Range for Wireless Ad Hoc Networks Based on Energy Efficiency

Abstract: The transmission range that achieves the most economical use of energy in wireless ad hoc networks is studied for uniformly distributed network nodes. By assuming the existence of forwarding neighbors and the knowledge of their locations, the average per-hop packet progress for a transmission range that is universal for all nodes is derived. This progress is then used to identify the optimal per-hop transmission range that gives the maximal energy efficiency. Equipped with this analytical result, the relation between the most energy-economical transmission range and the node density, as well as the path loss exponent, is numerically investigated. It is observed that when the path loss exponent is high (such as four), the optimal transmission ranges are almost identical over the range of node densities that we studied. However, when the path loss exponent is only two, the optimal transmission range decreases noticeably as the node density increases. Simulation results also confirm the optimality of the per-hop transmission range, which we found analytically.