Showing papers on "Data transmission published in 1989"

Subcarrier multiplexed lightwave systems for broad-band distribution

Abstract: Microwave subcarrier multiplexing (SCM) is an important approach to the design of lightwave systems for broadband distribution. Recent progress in the design and performance of both analog and digital multichannel SCM systems is reviewed. The application of broadband SCM systems to both passive and optically amplified distribution networks is discussed. The discussion covers the general features of SCM systems; the electrooptic components that have been used in the system experiments described here, including laser intensity noise and noise due to intermodulation products; the carrier-to-noise ratio requirements; some multichannel FM systems experiments; and a 20-channel digital systems experiment; and a hybrid system carrying 60 FM SCM channels plus a 100-Mb/s baseband digital channel. Several approaches to broadband subscriber distribution networks are analyzed. >

Bandwidth efficient coding for fading channels: code construction and performance analysis

Abstract: The authors apply a general method of bounding the event error probability of TCM (trellis-coded modulation) schemes to fading channels and use the effective length and the minimum-squared-product distance to replace the minimum-free-squared-Euclidean distance as code design parameters for Rayleigh and Rician fading channels with a substantial multipath component. They present 8-PSK (phase-shift-keying) trellis codes specifically constructed for fading channels that outperform equivalent codes designed for the AWGN (additive white Gaussian noise) channel when v>or=5. For quasiregular trellis codes there exists an efficient algorithm for evaluating event error probability, and numerical results which demonstrate the importance of the effective length as a code design parameter for fading channels with or without side information have been obtained. This is consistent with the case for binary signaling, where the Hamming distance remains the best code design parameter for fading channels. The authors show that the use of Reed-Solomon block codes with expanded signal sets becomes interesting only for large value of E/sub s//N/sub 0/, where they begin to outperform trellis codes. >

Apparatus and method for secure transmission of data over an unsecure transmission channel

Abstract: Apparatus and methods, readily adapted to interface with a standard data transmission network having an unsecure transmission channel, eg, "Ethernet," for the provision of secure transmission of data over the network channel in a manner which is essentially transparent to the standard network devices and users, thereof, are provided Various encryption keys are generated and utilized within the system to disguise or encrypt information transferrred between network nodes The encryption keys are made known only to those network devices which are permitted to handle information encrypted with the encryption keys

Matched Spectral Null Codes for Partial Response Channels

Abstract: A new family of codes that improve the reliability of digital communication over noisy, partial-response channels is described. The codes are intended for use on channels where the input alphabet size is limited. These channels arise in the context of digital data recording and certain data transmission applications. The codes-called matched-spectral-null codes-satisfy the property that the frequencies at which the code power spectral density vanishes correspond precisely to the frequencies at which the channel transfer function is zero. It is shown that matched-spectral-null sequences provide a distance gain on the order of 3 dB and higher for a broad class of partial-response channels. The embodiment of the system incorporates a sliding-block code and a Viterbi detector based upon a reduced-complexity trellis structure. The detectors are shown to achieve the same asymptotic average performance as maximum-likelihood sequence detectors, and the sliding-block codes exclude quasi-catastrophic trellis sequences in order to reduce the required path memory length and improve worst-case detector performance. Several examples are described in detail. >

Packet video and its integration into the network architecture

Abstract: Packet video is investigated from a systems point of view. The most important issues relating to its transmission are identified and studied in the context of a layered network architecture model, leading to a better understanding of the interactions between network and signal handling. The functions at a particular layer can thereby be made less dependent on network implementation and signal format. In the layered network model, the higher layers provide format conversion, hierarchical source coding, error recovery, resynchronization, cost/quality arbitration, session setup and tear-down, packetization, and multiplexing. Provisions from the network layers pertain mainly to real-time transmission. Special consideration is given to hierarchical source coding, error recovery, statistical behavior, and timing aspects. Simulation results indicating practical solutions to some of the issues raised are presented for a hierarchical packet-video subband coding system. >

Narrowband/wideband packet data communication system

Abstract: The best features of narrowband and wideband signaling are merged to provide a simple and reliable multiple-access network. This is done by transmitting the header of the packet using narrowband signaling coupled with an associated channel access protocol such as carrier-sense multiple-access. The data portion of the packet is then sent as a spread-spectrum signal with a spreading sequence that is common to all nodes in the network. The narrowband headers allow easy monitoring of channel loading and busy nodes while acting as a synchronization aid to the wideband signal. The multiple-access capability of spread-spectrum signaling increases channel throughput dramatically over a conventional narrowband-only system, and the anti-multipath feature allows increased data transmission rates on a multipath-prone channel. Common spreading sequences simplify transceiver design and allow packet broadcasting on the network.

A system and device for data transmission, and related method

Abstract: A system (1) for remotely displaying screen data on televisions (3) or the like transmits screen data over a plurality of commercial radio band carrier transmitters (5). A plurality of devices (13) are provided, each being for use with a corresponding television in a home. Each device includes a band receiver (33) and a decoder (35) for receiving and decoding screen data. A display signal is then generated for viewing on the television or the like. Each device can include means (20) for receiving responses from a user, for example responses to a program viewed. The device can also include a storage (51) for storing both screen data and response data. This enables response data to be transmitted at a later time, and it can be collected by polling from a central computer (25). Similarly, screen data can be received and stored, for later viewing.

An adaptive MLSE receiver for TDMA digital mobile radio

Abstract: The authors present a simulation study of an adaptive receiver, based on the concept of maximum-likelihood sequence estimation (MLSE), which compensates for the heavy selective distortions caused by multipath propagation. The receiver includes a matched filter and a modified Viterbi processor and is suitable for implementation in a digital form. It operates adaptively, in a training mode at the beginning of each burst, as well as in a tracking mode during message detection. This makes the receiver robust both to fast Doppler shifts and to a large frequency offset. Simulation results are presented which show the performance in different multipath environments, with echo delay in excess of 20 mu s and vehicle speed up to 250 km/h. >

Digital output transducer

Abstract: Contained within a single housing (120), is a transducer (100) for receiving an acoustic signal, an analog-to-digital converter (108), which changes the output of transducer (100) into a series of digital pulses representing the incoming acoustic signal. The output of the system may be in serial form. This serial output (114) is transmitted (116) to a remote receiver (122) by wires, light, optical fibers, or as radio waves. The receiver's (122) output (124) is applied to a digital system (130), which processes or reconstructs the acoustic signal. The system may include a digital signal processor (300) within the housing (120) for processing the signal (110) prior to transmission. The analog to digital converter may be a delta-sigma oversampling type, or a sub-ranging floating point type, or use adaptive differential pulse code modulation. Power may be derived remotely by transmission over the signal medium.

Mixed mode compression for data transmission

Abstract: In an integrated digital network with at least three nodes, A (31), B (33), and C (35), a call placed at node A (31) to be transmitted through the network from node A (31) to node B (33) to node C (35), is compressed in multiple modes. In response to the path selected, the speech signal in node A (31) is compressed in a first mode for transmission to node B (33). In node B (33), the speech signal is compressed in a second mode for transmission to node C (35), where the first and second modes involve dissimilar algorithms for compression of speech signals. At node C (35), the speech signal would again be adapted for supply to a receiving station. The system can accommodate as many modes of compression as desired.

Cable televison spread spectrum data transmission apparatus

Abstract: Apparatus for transmitting data spread across at least a portion of the bandwith of a cable television channel comprises a carrier signal oscillator (203), a frequency divider (205), a pseudorandom sequence generator (202) and two exclusive OR gates (207, 210). A first exclusive OR gate (207) serves to spread a data signal across the pseudorandom noise sequence generator (202) having a much higher chip rate than the bit rate of the data signal. The second exclusive OR gate (210) modulates the spread spectrum data signal to a carrier frequency for transmission over the cable television channel. The apparatus may be applied for return path transmission in the 0-30 megahertz band which is highly susceptible to interference noise and provides approximately a 20 dB signal to interference ratio advantage over known data coding and transmission schemes. A microprocessor (201) normally present in a cable television terminal may format data for transmission, control the spread spectrum modulation process and control gain control circuitry for introducing an appropriate power level into the cable plant.

Wireless indoor data communication system

Abstract: Described is an intraoffice communication system as the final communication link of a broadband, baseband, or fiber optic LAN. Each user or workstation is a node on the network and can transmit at high data rates with bit error rates of ≦10-9 in packets through the LAN. Message relaying transponders are placed on the ceiling and walls communicating by electromagnetic waves to individual workstations by broadcast. A novel multipath rejection scheme is combining transponder placements with pseudonoise coding for robust and secure data transmission. For the present state of the art if infrared is used, we estimate a minimum light collecting aperture (receive antenna) of 1 cm2 for transmission rates of 30 to 100 Mb/s.

Synchronous quantized subcarrier multiplexer for digital transport of video, voice and data

Abstract: This invention addresses the digital transmission of wideband video, narrowband audio, and digital information over information networks. More specifically, the invention involves synchronous quantized subcarrier multiplexing (quantized-SCM) which results in purely electronic multiplexing of voice, data and multiple channel full bandwidth NTSC video for digital transmission over a communcation line and recovery of same signals at a receiving station.

Direct conversion transceiver design for compact low-cost portable mobile radio terminals

Abstract: A prototype direct conversion transceiver for portable mobile radio terminals has been developed and is under evaluation. Test results are presented showing the performance of this transceiver to be equivalent to (and in some cases better than) that of existing systems. The transmitter and receiver are described, and the receiver fading performance is examined. The results presented show that a direct conversion transceiver system can be made to work at both VHF and UHF. The improved channel characteristics facilitated by digital channel filtering make this configuration particularly suited to data transmission. In addition, the integration potential of all the system components is important for the concept of a 'personal communicator'. >

Packet data transmission over mobile radio channels

Abstract: Since in mobile radio Rayleigh fading poses the main threat to accurate data transmission, a mathematical model of the dynamics of Rayleigh fading is used to explore the optimum duration of data packets. The performance criterion is the rate of information transfer through the mobile radio channel. In addition to packet size, the information rate depends on: the speed of the mobile terminal, the channel bit rate, the size of the packet header, and the fade margin of the modulation and coding techniques. In particular, attention is focused on line rates of 16 kb/s and 256 kb/s (which are representative of the rates proposed for digital mobile radio systems in North America and Europe, respectively). At 16 kb/s, the optimum packet size is approximately 17 B (8.5-ms duration). At 256 kb/s, maximum throughput occurs when the packet contains about 48 B (1.5-ms duration). The precise optimum depends on vehicle speed, header size, and fade margin. The optimum packets are considerably shorter than the 125-B packets customarily used in terrestrial and satellite systems. >

Digital transmission device having an error correction mode and method for shifting down a data transmission rate

Abstract: In a method for shifting down a data transmission rate at a transmitter in response to a request from a receiver for retransmission of data frames having data errors in a digital transmission system such as a facsimile system, when transmission errors occur, the receiver transmits a request to the transmitter for retransmission of one or more data frames for which one or more data errors have occurred. At the transmitter, the data transmission rate is shifted down from the first data transmission rate to a second data transmission rate which is used for retransmitting the data frames for which one or more data errors have occurred. The above shift-down operation is controlled by calculating an expected value indicating a possibility of the occurrence of a data error at the time of retransmitting the data frames in which one or more data errors have occurred, on the basis of a number of data frames requested to be retransmitted and a total number of data frames which have been transmitted from the transmitter to the receiver.

An all digital receiver architecture for bandwidth efficient transmission at high data rates

Abstract: Using the maximum-likelihood approach, algorithms for detection and synchronization are derived that are well suited for VLSI implementation. Special emphasis is placed on an all-digital implementation where carrier and clock synchronization do not require a feedback of signals to the analog part, which simplifies the analog front-end design (mixing oscillator and A/D converter sampling clock run at fixed frequency). An important advantage of the proposed algorithms is that a high clock rate is not required; only two-four times the symbol rate is needed, depending on amplitude quantization. Implementation aspects, e.g. architecture, and quantization, are considered. A prototype is described which was implemented to prove the feasibility of the concept and to evaluate the performance under practical conditions. >

Pulse width modulated self-clocking and self-synchronizing data transmission and method for a telephonic communication network switching system

Abstract: Transmissions of synchronous digital data from a master control unit (50A) to a slave, network termination unit (50B) are via a pulse width modulated data stream including pulse width modulated binary code pulses (20, 22) with a pulse width modulated synchronization pulse (24) all of which have a preselected leading edge transition (28) at the same point in each cycle of a master clock signal. A clock signal is derived at the network termination unit (50B) from the received pulse width modulated binary data stream for decoding and for nonself-clocking, synchronous transmissions from the slave, network termination unit (50B) to the master, control unit (50A). The phase synchronization pulse (24) is employed to maintain phase sychronization between the transmission to and from the control unit (50A).

Data transmission and reception apparatus and method

Abstract: A data transmission and reception apparatus and method capable of selecting either of two modes having the same sampling frequency in which the bit numbers of one data unit are either m or n (which are integral numbers and m>n), while using the same error correction encoder and decoder for the two modes, by inserting m-n bits of dummy data bits into the n-bit data so as to handle it as m-bit data during the processes of error correction encoding and decoding.

Apparatus and method for updating a remote video display from a host computer

Abstract: Apparatus and a method are disclosed for reducing the transmission power required when a host computer displays video information on a remote video display. A video memory is located in close proximity to the display so that the display can be periodically refreshed in the normal manner from the local memory. Consequently, the host computer need only transmit information regarding the portions of the local memory that have changed since the last data transmission. Since the information for the entire local memory is not transmitted each time the memory must be updated and in particular, each time the display must be refreshed, the required data transmission rate between the host and the display is greatly reduced from the rate normally required with prior art apparatus and, consequently, the power consumption is reduced. In addition, a data and command multiplexing scheme is used to minimize the number of data communication lines which must be used between the transmitting and receiving devices, thus further reducing the power consumed during data transmission.

Adaptive carrier recovery systems for digital data communications receivers

Abstract: Adaptive or predictive carrier recovery systems, which are essential in high-performance quadrature-amplitude-modulated (QAM) data communications systems to correct for phase jitter and frequency offset, are considered. Analytical and experimental results are presented for two structures that implement a predictive carrier recovery system. These systems, which adapt their structure to match the spectral properties of the impairments, avoid the conflict between a wide bandwidth (to track fast jitter) and a narrow bandwidth (to minimize output noise) inherent in most carrier recovery loops. Such a system increases the likelihood that very bandwidth-efficient modems (e.g., 7 b/s/Hz for 19.2 kb/s voiceband modem applications) can provide reliable transmission in the presence of severe phase jitter and frequency offset. In particular, the predictive carrier recovery systems can track sinusoidal jitter present at more than one frequency as well as generalized time-varying phase jitter processes. Both finite-impulse-response (FIR) and infinite-impulse-response (IIR) adaptive phase tracking systems are considered. Prior limitations on adaptive IIR filters are overcome by designing a structure that is guaranteed to be stable and to possess only a global minimum as the filter coefficients converge to their desired values. >

Optimized decision feedback equalization versus optimized orthogonal frequency division multiplexing, for high-speed data transmission over the local cable network

Abstract: The ideal near-end crosstalk and thermal noise-limited throughput capabilities of uncoded decision feedback equalized (DFE) and orthogonally frequency division multiplexed (OFDM) PAM digital signals transmitted over nonloaded twisted metallic pairs bundled in a multicore transmission cable are determined. Though OFDM has recently loomed as a possible strong competitor among alternatives to DFE for high-speed data transmission over the digital subscriber loop network, it is revealed to be, at best, of marginal value, even if one allows an infinite number of transmission subchannels. >

Method and apparatus for stabilized data transmission

Abstract: Data can be accurately transmitted between two subsystems even if the clock skew between the two subsystems is larger than one clock cycle by the method of the invention. In one embodiment data is loaded into N state devices in the sending subsystem while the receiver recovers data from the sending state devices in rotation with an N input multiplexer. Another embodiment forwards a clock signal from the sending subsystem along with a data vector of N state signals for recovery by a pair of state devices capturing data on the rising and falling edges of the forwarded clock. A further embodiment achieves double bandwidth by forwarding two clock signals.

Tdm demultiplexer with dedicated maintenance channels to indicate high-speed line faults to low speed circuits

Abstract: In a channel bank at one of TDM hierarchical levels, a TDM demultiplexer includes a plurality of high-speed interfaces connected respectively to high-speed digital transmission lines. Each interface receives detects a line fault and appends an alarm signal of a time-slot duration to time slots of digital signals. The outputs of the high-speed interfaces are multiplexed into a TDM frame sequence and the time slots of data signals in that TDM frame sequence are interchanged according to a prescribed rule. The slot-interchange frame sequence is demultiplexed into plurality of TDM signals greater in number than the number of the high-speed interfaces. Low-speed interfaces respectively receive the demultiplexed TDM signals to detect the time slot in which the alarm signal is contained and transmits a line fault signals to a respective one of low-speed transmission lines.

Pcm data transmitting apparatus and method

Abstract: A data transmission and reception apparatus and method capable of selecting either of two modes having the same sampling frequency in which the bit number of one data unit are either m or n (which are integral numbers and m>n), while using the same error correction encoder and decoder for the two modes, by inserting m-n bits of dummy data bits into the n-bit data so as to handle it as m-bit data during the processes of error correction encoding and decoding and eliminating from the error correction encoded data the dummy data and a redundant code of the error correction code formed by the dummy data so that the data transmission rate can be lowered.

Remote operation control for computer system

Abstract: A control apparatus for realizing remote operation control for a computer system is interposed between the Computer system and a master console for supervising data stream on a data transmission/reception signal line existing between the computer system and the master console. Occurrence of error in the computer system is messaged to a remote terminal through a public telecommunication line. Commands for the computer system can be inputted from the remote terminals.

Image data transfer method and apparatus therefor

Abstract: An image data transfer system constructed of an image data transfer unit, transmission medium and image data reproduction unit. In the image data transfer unit, an input video signal is transformed into image data through sampling and quantization, the image data are coded in a predetermined image coding method, and transferred to the transmission medium. In the image data reproduction unit, the coded data transferred by the transmission medium are decoded in a predetermined image decoding method, the original video signal is restored from the decoded data. A data transfer speed and transfer scheme are selected such that the total coded data amount for the input video signal over a predetermined time duration becomes equal to or smaller than a transferable data amount determined by a data transfer speed from the transmission medium to the image data reproduction unit and by the predetermined time duration. Data transfer information on the selected data transfer speed or information on the transfer scheme is transferred to the transmission medium along with the coded data.

Optical Data Storage Topical Meeting

Abstract: These proceedings present papers on the subjects of magnetic disks and magneto-optical effects of optical systems.

Method and apparatus for dynamic data block length adjustment

Abstract: A method and apparatus for sensing the amount of current data traffic on a high speed parallel bus, such as a Multibus II, and dynamically adjusting the allowable length of a any data block from any bus agent to optimize bus efficiency. A data transfer activity counter or similar device counts the amount of bits transferred in a predetermined sample interval, which is decoded after every sample interval and the allowable block length adjusted. The data block lengths are preselected to optimize efficiency at various average operating conditions with the further consideration that each agent has a maximum data latency time which should not be exceeded before that agent gains access to the bus.