Showing papers on "Data transmission published in 1997"

Multipoint communication: a survey of protocols, functions, and mechanisms

Abstract: Group communication supports information transfer between a set of participants. It is becoming more and more relevant in distributed environments. For distributed or replicated data, it provides efficient communication without overloading the network. For some types of multimedia applications, it is the only way to control data transmission to group members. This paper surveys protocol functions and mechanisms for data transmission within a group, from multicast routing problems up to end-to-end multipoint transmission control. We provide a bibliography which is organized by topic.

Adaptive coded modulation for fading channels

Abstract: We propose a variable-power and variable-rate coded MQAM modulation technique for high-speed data transmission on fading channels. Coding gain is obtained by superimposing trellis codes designed for AWGN channels on the adaptive modulation, and we obtain the same coding gains as these codes exhibit in AWGN. We present analytical and simulation results which show a 3dB coding gain relative to uncoded adaptive modulation for a simple 4-state trellis code, and a 4 dB coding gain for an 8-state trellis code. More complex trellis codes achieve higher gains.

The role of synchronization in digital communications using chaos. I . Fundamentals of digital communications

Abstract: In a digital communications system, data is transmitted from one location to another by mapping bit sequences to symbols, and symbols to sample functions of analog waveforms. The analog waveform passes through a bandlimited (possibly time-varying) analog channel, where the signal is distorted and noise is added. In a conventional system the analog sample functions sent through the channel are weighted sums of one or more sinusoids; in a chaotic communications system, the sample functions are segments of chaotic waveforms. At the receiver, the symbol may be recovered by means of coherent detection, where all possible sample functions are known, or by noncoherent detection, where one or more characteristics of the sample functions are estimated. In a coherent receiver, synchronization is the most commonly used technique for recovering the sample functions from the received waveform. These sample functions are then used as reference signals for a correlator. Synchronization-based receivers have advantages over noncoherent ones in terms of noise performance and bandwidth efficiency. These advantages are lost if synchronization cannot be maintained, for example, under poor propagation conditions. In these circumstances, communication without synchronization may be preferable. The main aim of this paper is to provide a unified approach for the analysis and comparison of conventional and chaotic communications systems. In Part I, the operation of sinusoidal communications techniques is surveyed in order to clarify the role of synchronization and to classify possible demodulation methods for chaotic communications.

Data-aided frequency estimation for burst digital transmission

Abstract: Burst transmission of digital data is employed in several applications such as satellite time-division multiple access (TDMA) systems and terrestrial mobile cellular radio. We propose a new algorithm for carrier frequency estimation in burst-mode phase shift keying (PSK) transmissions. The algorithm is data-aided and clock-aided and has a feedforward structure that is easy to implement in digital form. Its estimation range is large, about /spl plusmn/20% of the symbol rate and its accuracy is close to the Cramer-Rao bound (CRB) for a signal-to-noise ratio (SNR) as low as 0 dB. Comparisons with earlier methods are discussed.

Computer having packet-based interconnect channel

Abstract: A physically non-distributed microprocessor-based computer includes a microprocessor, and a random access memory device, a mass storage device, and an input-output port device, all operable from the microprocessor and including an interface for receiving and transmitting data in packet form. A novel packet-based data channel extends between the microprocessor and the interfaces of the devices to provide communication between the microprocessor and the devices. By varying the size of the packets in accordance with actual data transmission requirements improved computer performance is achieved.

Device control with topology map in a digital network

Abstract: A topology map for a digital system is generated and displayed on a display device to indicate the various components which make up the system. The various components are indicated using icons each of which represent a respective one of the components. A user specifies a source device and a receive device by manipulating the corresponding icons so as to cause a data transfer between the source device and the receive device. The data transfer may include the transfer of video data, audio data, or both. In a preferred embodiment, the digital network corresponds to the IEEE 1394 Serial Bus Standard.

Method and apparatus for transbody transmission of power and information

Abstract: Capacitive coupling is used to transmit data and power through a user's body. In one implementation, a transmitter carried by the user transmits power and data to a receiver, which is also carried on the user's body. The signal that the transmitter applies to the user's body not only contains a data component, but also powers the receiver and enables it to detect and decode the data. In other implementations, the transmitter or the receiver is physically displaced from the user's body (although both receiver and transmitter are coupled to environmental ground), and data and power are transmitted when the transmitter and receiver become sufficiently proximate—via the user's body—to permit capacitive coupling. The disclosed approach is amenable to a wide variety of applications, ranging from “interbody” exchange of digital information between individuals through physical contact (e.g., a handshake) to “intrabody” data transfer (e.g., between a paging device worn in the shoe and a wristwatch display device) to devices that permit communication between the user and his or her immediate environment.

Low-power encodings for global communication in CMOS VLSI

Abstract: Technology trends and especially portable applications are adding a third dimension (power) to the previously two-dimensional (speed, area) VLSI design space. A large portion of power dissipation in high performance CMOS VLSI is due to the inherent difficulties in global communication at high rates and we propose several approaches to address the problem. These techniques can be generalized at different levels in the design process. Global communication typically involves driving large capacitive loads which inherently require significant power. However, by carefully choosing the data representation, or encoding, of these signals, the average and peak power dissipation can be minimized. Redundancy can be added in space (number of bus lines), time (number of cycles) and voltage (number of distinct amplitude levels). The proposed codes can be used on a class of terminated off-chip board-level buses with level signaling, or on tristate on-chip buses with level or transition signaling.

Dual-mode digital FM communication system

Abstract: A dual-mode digital communication system for communicating an information signal during operation in frequency-modulated (FM) and multiple-access modes is disclosed herein. The digital communication system includes a dual-mode transmitter for transmitting the information signal using an FM communication signal during FM mode operation, and for transmitting the information signal using a multiple-access communication signal during multiple-access mode operation. The communication system further includes a dual-mode receiver for receiving the FM communication signal during FM mode operation, and for receiving the multiple-access communication signal during multiple-access mode operation. Incorporated within the dual-mode receiver is a digital demodulator for recovering the information signal from the received FM signal during operation in the FM mode, and for recovering the information signal from the received multiple-access signal during multiple-access mode operation. In a preferred implementation the dual-mode transmitter is disposed to convert a first sequence of binary data within the information signal into a sampled modulation waveform, and to provide the FM communication signal by modulating a carrier signal based at least in part on the sampled modulation waveform. The dual-mode transmitter may also be configured to multiplex a second sequence of wideband message data with the sampled modulation waveform so as to form a composite FM modulation waveform.

Inverse filtering criteria for CDMA systems

Abstract: Linear blind CDMA receivers are derived using inverse filtering criteria. The receiver parameters are directly obtained without explicit estimation of the system/channel. Both synchronous and asynchronous cases are addressed, and multipath distortions are explicitly considered and compensated for. The approach is based on minimizing the receiver's output energy subject to appropriate constraints. Similar approaches have been used before in multiuser systems but without considering multipath distortions. Batch and adaptive blind algorithms are derived that are near-far resistant and do not require knowledge of the interfering users' codes. Global convergence is shown, optimality and performance issues are discussed, and some illustrative simulations are presented.

A network switch with a multiple bus structure and a bridge interface for transferring network data between different buses

Abstract: A network switch includes a plurality of first network ports coupled to a first bus, a plurality of second network ports coupled to a second bus, a bridge interface enabling data transfer between the buses, a switch manager controlling the flow of network data, and a processor for performing supervisory and control functions. The first and second network ports operate according to different network protocols, and the first and second buses operate according to different bus standards. During packet data transfers across the first bus, the bridge interface emulates a first network port. During packet data transfers across the second bus, the bridge interface primarily acts as a slave to the second network ports by storing control lists for execution by the second network ports, thus relieving the processor of performing overhead functions associated with data transfers across the second bus.

Data transfer method and system in low voltage networks

Abstract: The present invention concerns a data transfer process in a two-way communication via low voltage networks connected to a telecommunication network. The data transmission on the low voltage network is carried out in a high frequency range up to 30 mHz, with a strip display of data signals and a transmission level below the radio-and-line-interfering voltage-limit, while signals displayed by pseudo-random numbers are provided to ensure a multi-user structure with various sequences within a family in order to give a logical direction on the low voltage network with a directional codification, whereby the binary data sequences in the low voltage network which are displayed in relation to the users and those which are characterized in relation to the direction, are recognized in a correlator at intervals determined by the damping rate by means of the sequences which are prescribed, regenerated and evaluated with a new directional characteristic for rerouting signals.

Simultaneous quantum cryptographic key distribution and conventional data transmission over installed fibre using wavelength-division multiplexing

Abstract: Wavelength division multiplexing (WDM) is used to add a secure quantum key distribution channel (/spl lambda/=1300 nm) to a conventional 1.2 Gbit/s data channel (/spl lambda//spl sim/1550 nm) operating over 28 km of installed fibre in BT's London and East Anglia multiservice network testbed (LEANET). Error-free operation of the data channel is demonstrated with no degradation of the quantum channel performance.

Method and apparatus for data transmission using multiple transmit antennas

Abstract: A method and apparatus for increasing the data rate and providing antenna diversity using multiple transmit antennas is disclosed. A set of bits of a digital signal are used to generate a codeword. Codewords are provided according to a channel code. Delay elements may be provided in antenna output channels, or with suitable code construction delay may be omitted. n signals represent n symbols of a codeword are transmitted with n different transmit antennas. At the receiver MLSE or other decoding is used to decode the noisy received sequence. The parallel transmission and channel coding enables an increase the data rate over previous techniques, and recovery even under fading conditions. The channel coding may be concatenated with error correction codes under appropriate conditions.

Method and apparatus for providing anonymous data transfer in a communication system

Abstract: A method, and associated apparatus, of providing a communication station (12) with anonymous access to a communication network (14) to communicate data therein. Access is provided to the communication station (12) only after authenticating that the communication station is authorized to communicate in the network (14), but access is provided without individually identifying the communication station (12) to the network (14) with a permanent identifier unique to the communication station.

Introduction to Digital Mobile Communication

Abstract: From the Publisher: A thorough introduction to digital mobile communication technology, this book emphasizes digital transmission methods. Beginning with an introduction to what digital mobile communication is, it presents mathematical analyses of signals, mobile radio channels, digital modulation methods and more.

High precision spatially defined data transfer system

Abstract: A system for transferring digital information to spatially localizable portable electronic devices has a plurality of portable electronic devices, with each portable electronic device supporting wireless communication. A spatial localizing module determines spatial location with submeter precision for each of the plurality of electronic devices, and a communication module is connected to the spatial localizing module for mediating wireless communication between the portable electronic devices. A user can define electronic data transfers between portable electronic devices in user determined spatial locations with submeter precision. Data transfers are possible to adjacent electronic devices, electronic devices within a defined radius, electronic devices along a defined bearing or having specific orientations, or even located within a defined set of regions or rooms.

Multiple access communication network with combined contention and reservation mode access

Abstract: Channel access for communicating a data packet over a multiple access communication network with a forward channel and a multiple access reverse channel which efficiently handles a mix of short message and long data transfer communication type traffic is provided by combined contention and reservation mode access to the multiple reverse channel. A forward channel transmission apparatus or base station broadcasts a forward channel control packet associated with a subsequent transmission window which channel control packet includes an indication of contention or reservation mode for the subsequent transmission window and an identifier identifying a device to be granted reservation mode access to the reverse channel. The forward channel transmission apparatus allocates access to reservation mode transmissions responsive to reservation requests transmitted by reverse channel transmission apparatus or subscriber devices having data packets to transmit which exceed the data packet size which may be transmitted within the constraints of a contention mode burst. For short length data packets, the reverse channel transmission apparatus transmits the data packet in a contention window rather than transmitting a reservation request to obtain reservation mode access to the reverse channel for transmission of the data packet. The base station further transmits an acknowledgment of successfully received data packets allowing the subscriber device to submit for retransmission data packets which are not successfully transmitted without the need to involve higher layer error recovery mechanisms. The broadcast channel control packet is associated with a subsequent transmission window so that the reverse channel transmission apparatus may be provided with slow receive to transmit switching time hardware.

Data transmission protocol method and apparatus

Abstract: A data communications protocol for single path media having low data error rate requires the generation of a data packet with a start code field having a predetermined pattern, a byte count field for defining a data field having a maximum predetermined length in bytes, a data payload field having a byte count according to the value of the byte count field and a cyclic redundancy cheek field of predetermined length. The value of the byte count field may be fixed, may be changed from packet to packet or may be changed upon initialization. The described data communications protocol permits utilization with data types varying from high definition television to alarm reporting applications. Moreover, the data rate may be varied by varying an idle time signal duration up to a maximum (when the idle time signal duration is reduced to zero). According to one exemplary embodiment for plastic fiber optic media, MPEG2 transport stream packets may be transmitted at 54 MB and over distances of 20 meters or even more with other media.

Apparatus and method for processing a quadrature amplitude modulated (qam) signal

Abstract: Apparatus (130) and method for receiving a QAM signal using a backward compatible hierarchical coding scheme to increase data transmission using finer constellations, while maintaining compatability with existing Direct Broadcasting Satellite (DBS) systems. The apparatus employs multiple stages of decoders (146,170) such that the finer constellations of the QAM signal are unraveled at different stages.

High speed communications system for analog subscriber connections

Abstract: A new data communication system is described which enables data transmission over existing telephone lines at rates higher than possible with existing methods, including conventional modems. By using a novel asymmetric configuration of the two communication endpoints, the currently-accepted maximum theoretical limits on the data rate are no longer applicable. One endpoint is connected directly to a digital telephone network, whereas the other endpoint uses a conventional telephone connection. This reduces the transmission problem to compensation for a single telephone line interface and a single analog local loop. Means of providing this compensation and the required clock synchronization were also created, enabling a practical implementation of the system. The new system can achieve rates up to 64,000 bits-per-second and has broad utility in several active areas including wide-band audio transmission, video transmission, networking, facsimile transmission, and remote computer access.

Spread-spectrum techniques for wireless communication

Abstract: The primary goal of this paper is to provide a concise introduction to the use of spread spectrum in wireless communications. The symbiotic relationship between wireless communications and digital microelectronics is also developing rapidly. Indeed, mobile and personal communications is now at parity with the computer industry as a major driver in the development of high-speed, low-power integrated circuits. Underlying this is the deep relationship between the theories of signal processing and communication. This is the motivation behind the second objective of this article: to present the concepts and capabilities of spread spectrum so that engineers versed in DSP can quickly grasp its utility and exploit opportunities for further advancing the performance of spread-spectrum systems. To these ends, we first present a simple digital communication system that operates in discrete time. Then we build upon this model to show the basic concepts and resulting benefits of spread spectrum. Then we introduce the two basic spread-spectrum techniques of direct-sequence (DS) and frequency hopping (FH), followed by two methods that have been recently proposed. Next we present simple models for the multipath fading channel, and introduce solutions employing both DS and FH techniques. We then briefly discuss descriptive links to other nonspread modulation techniques and conclude with a brief introduction to the literature for further investigation by the reader.

Semiconductor IC with a plurality of processing circuits which receive parallel data via a parallel data transfer circuit

Abstract: A semiconductor integrated circuit having a two-dimensional array (MAR) and a parallel data transfer circuit (TRC) for transferring from the array data read out in parallel through data lines, in parallel to a processing circuit group (PE) by selecting the word lines of the two-dimensional memory array. The processing circuit group executing processing operations in parallel by using the data transferred from the parallel data transfer circuit. Each of the processing circuits having access to a plurality of series word lines and the data lines of the two-dimensional array through the parallel data transfer circuits. The arrangement of the parallel data transfer circuits allowing for an overlap range wherein data from each of the data lines of the memory array is available to more than one of the parallel data transfer circuits. Since the data lines of the two-dimensional memory array have the overlapped range, convolution processing operations or the like can be executed in parallel for the two-dimensional data stored in the two-dimensional memory array in a high parallelism and at a high speed.

Apparatus and method for requesting and dispensing negotiable instruments

Abstract: The present invention provides an apparatus and method for requesting and dispensing negotiable instruments such as bank checks, money orders, and traveler's checks. An instrument may be requested in this apparatus and method by a bank customer from a telephone, a computer, a fixed-location dispenser, or a portable, hand-held dispenser that is in communication with a bank computer. This request may be made orally, using touch tones, or using data transmission over a communication network that may include telephone lines, two-way radio links, microwave links, satellite links, cellular telephone links, computer networks, and the Internet. After a request is processed and approved, the requested instrument may then be dispensed at any time in this apparatus and method to the bank customer or another party from any receive-only dispenser, fixed-location dispenser, or portable, hand-held dispenser that is also in communication with the bank computer.

Scheduled data Transmission system, scheduled data transmission method, and transmission server

Abstract: This invention makes it possible to link separately employed pagers, PHS, and other data terminals with computer networks such as the Internet, and to schedule transfer of data to the data terminals. In a system for transferring message to pagers from user terminals connected to the Internet, a user terminal indicates to a transmission server the time for message transfer, and the transmission server, using a code conversion table, converts the message to the code adapted to the particular pager service provider and pager terminal, and transmits the message to the pager terminal at the indicated time.

Methods, systems and computer program products for reliable data transmission over communications networks

Abstract: Methods, systems and computer programs provide reliable transmission of data over a communications link in a communications network which otherwise may be unreliable. The transmission of the data packets in a communications link between a sending station and a receiving station is reliably managed by biasing the expected round trip time associated with the first sending station to accommodate relatively large fluctuations in the actual latency of transmissions in the data packets between the sending station and the receiving station whereby the number of retransmissions of data packets between the sending station and the receiving station is relatively minimized. The retransmission of data packets is controlled by first modifying the expected round trip time associated with the first computer causing the expected round trip time to approach the largest actual latency experienced by the sending station and also to account for the size of the data packets successfully transmitted between the sending station and the receiving station. The retransmission of the data packets may also be controlled by dynamically regrading the round trip time associated with the sending station based on an indication by the receiving station that the communications link can be trusted. The round trip timer is regraded by dynamically increasing the expected round trip time based on the successful transmission of a data packet on the first attempt and is dynamically decreased based on the unsuccessful transmission of the data packet on the first transmission attempt. The communications network may be a wired communications network, a wireless communications network, or a combination of wired and wireless communications networks.

Encryption apparatus for ensuring security in communication between devices

Abstract: In the first devices, MPU 53 generates random number R1 as challenge data. Random number R3 is generated by first encryption IC 54, and then combined with random number R1, encrypted, and sent to second device 52 as encrypted text C1. When encrypted text C2 is similarly received from second device 52, first encryption IC 54 decrypts C2 and separates the decrypted result into first separated data RR2 and second separated data RR4. The first encryption IC 54 returns the first separated data to second device 52 as response data. MPU 53 compares the first separated data returned from second device 52 with random number R1, and in the event of a match, authenticates second device 52 as a legitimate device. The first encryption IC 54 generates the time-varying data transfer key by combining second separated data RR4 with random number R3, and transfers the digital copyrighted data to second device 52 by using the data transfer key.

Integrated circuits for data transmission over twisted-pair channels

Abstract: This paper discusses typical architectures and challenges in designing integrated circuits for data transmission over twisted-pair wire channels. To highlight the various architectural approaches, two main applications are discussed-high-bit-rate digital subscriber loop (HDSL) and fast-Ethernet. Although these two applications have orders of magnitude difference in their bit rates, they share many common building blocks including line-drivers, 24 wire hybrids, echo cancellation, digital equalization, and clock recovery. Typical integrated circuit approaches for realizing each of these blocks are presented as well as possible tradeoffs. Finally, future challenges facing integrated circuit designers are presented.

Method and apparatus for pre-transmission power control using lower rate for high rate communication

Abstract: The present invention employs a method and apparatus for providing improved power control when changing the rate at which data is sent in a communications system. When data arrives at the transmitter for transmission at a high rate, power control feedback is changed from a slow mode (with a low bandwidth feedback channel) to a fast mode (with a high bandwidth feedback channel). This control changes even before the data is transmitted at the high rate. Once the power level is accurately estimated for data transmission at the high rate, then data transmission begins at the high rate.

Mouse adapted to scan biometric data

Abstract: In the past, contact imaging devices were large and costly. It has been proposed that for contact imaging device adoption for the personal computing market, cost and size must be reduced. In an attempt to address these concerns, a biometric pointing device such as a mouse is presented incorporating therein a contact imager. The contact imager fits within a small enclosure. Further, data transmission means within the mouse provides a signal to a single port on a computer indicative of the output data from both the contact imaging means and the pointing device.