Showing papers on "Data transmission published in 1986"

Transmission Range Control in Multihop Packet Radio Networks

Abstract: This paper presents a model for analyzing the performance of transmission strategies in a multihop packet radio network where each station has adjustable transmission radius. A larger transmission radius will increase the probability of finding a receiver in the desired direction and contribute bigger progress if the transmission is successful, but it also has a higher probability of collision with other transmissions. The converse is true for shorter transmission range. We illustrate our model by comparing three transmission strategies. Our results show that the network can achieve better performance by suitably controlling the transmission range. One of the transmission strategies, namely transmitting to the nearest forward neighbor by using adjustable transmission power, has desirable features in a high terminal density environment.

Speech and data multiplexor optimized for use over impaired and bandwidth restricted analog channels

Abstract: The present invention relates to an apparatus and method for the simultaneous transmission of analog speech and modulated data, such apparatus and method being optimized for use over impaired and bandwidth restricted analog channels, or digital representations of such channels. In each instance of use, an evaluation is made of the available channel bandwidth, with a frequency division multiplex scheme allocating a voice sub-band, with data transmission allocated to sub-bands above, below, or around, this selected voice sub-band. The speech and data sub-band allocations are made by the multiplexor in response to user input of either a requested speech quality, a requested data rate, or a value indicating the relative user weighting of speech quality and data rate. A multi-carrier multi-mode modulation scheme is employed for data transmission, with this scheme having the ability to fully utilize the remaining bandwidth, and further, being capable of adapting to the impairments most likely present on the fringes of bandwidth restricted analog channels. When the analog channel employed is the standard voice-grade telephone circuit, good speech quality simultaneously with 3000 bps data transmission may be expected. The further ability to automatically switch to full bandwidth data transmission when voice transmission is not being attempted is also provided.

A Class of Optimum Block Codes in Signal Space

Abstract: By using convolutional coding coupled with expanded sets of channel signals, Ungerboeck showed that it is possible to obtain coding gains of several decibels at a given data rate without increasing the transmission bandwidth. In this paper, we construct a class of optimum signal space codes using short binary block (as opposed to convolutional) codes. Our results are compared to those obtained by Ungerboeck. A simplified decoding procedure that is asymptotically optimum is also presented.

Trellis Coding for Partial-Response Channels

Abstract: We consider trellis-coding techniques for improving the reliability of digital transmission over noisy partial-response channels. Such channels are commonly encountered in digital communication systems, and also play a role in devices for data recording. Concentrating on the channels with characteristics (1 \mp D) , we study methods to obtain codes which increase free Euclidean distance between permitted sequences of channel outputs and avoid the occurrence of unlimited runs of identical outputs at the expense of some loss in data rate. One technique employs the concept of set partitioning. The other is based on using convolutional codes designed for maximum free Hamming distance in conjunction with a precoder. Both methods lead to essentially equivalent codes.

Frequency-hop transmission for satellite packet switching and terrestrial packet radio networks

Abstract: The performance of frequency-hop transmission in a packet communication network is analyzed. Satellite multiple-access broadcast channels for packet switching and terrestrial packet radio networks are the primary examples of the type of network considered. An analysis of the effects of multiple-access interference in frequency-hop radio networks is presented. New measures of "local" performance are defined and evaluated for networks of this type, and new concepts that are important in the design of these networks are introduced. In particular, error probabilities and local throughput are evaluated for a frequency-hop radio network which incorporates the standard slotted and unslotted ALOHA channel-access protocols, asynchronous frequency hopping, and Reed-Solomon error-control coding. The performance of frequency-hop multiple access with error-control coding is compared with the performance of conventional ALOHA random access using narrow-band radios.

Cycle time properties of the FDDI token ring protocol (extended abstract)

Abstract: Communication technology now makes it possible to support high data transmission rates at relatively low cost. In particular, optical fiber can be used as the medium in local area networks with data rates in the range of 100 megabits per second. Unfortunately, local area network topologies and communication protocols that work well with lower speed media are not necessarily appropriate when the data transmission rate is scaled up by approximately an order of magnitude. Recognizing this fact, an ANSI sub-committee (ANSIX3T9) has been working for the past two years on a proposed standard for a token ring protocol tailored to a transmission medium with transmission rate in the 100 megabits per second range. The protocol is referred to as the FDDI (Fiber Distributed Data Interface) Token Ring protocol. The proposal for the standard is now quite mature and nearly stable.

Advanced Groupband Data Modem Using Orthogonally Multiplexed QAM Technique

Abstract: An advanced groupband data modem based on the orthogonally multiplexed QAM technique is proposed. Its performance is evaluated through experiments. In the proposed modem, data are transmitted by a number of orthogonally multiplexed parallel subchannels. Because of this orthogonally multiplexing parallelism, the proposed modem becomes more immune to Gaussian noises, impulsive noises, and channel distortions, compared to the conventional Class IV partial response VSB modem. Furthermore, the orthogonally multiplexed QAM modem retains high flexibility in multiplexing a variety of data terminals and in carrying out fallback operation to a wide range of data rates. Experimental results demonstrate the robustness of the proposed groupband data modem.

Local area network with self assigned address method

Abstract: A local area network is disclosed including apparatus and methods for transferring data between a plurality of data processing resources ("agents") coupled to a cable. In the preferred embodiment, a plurality of agents are coupled to a common cable for data transmission and reception. An agent newly coupled to the cable dynamically assigns itself a unique address on the cable to which other agents may send data. Once an agent has been assigned a final address, it may then transmit to, and receive data from, other agents on the cable. An agent desiring to send data to a receiving agent follows a three step handshake, wherein the sending agent transmits an "RTS" signal and within a predetermined time must receive a "CTS" signal from the receiving agent. The sending agent then transmits a data frame within a predetermined time after the CTS signal is received. The failure to detect a return CTS signal within the predetermined time denotes a collision condition. Re-transmission is attempted using a linear back off method which is adjusted based on previous cable traffic history.

CMOS RF circuits for data communications applications

Abstract: The author describes the recent development of two analog CMOS circuits operating at RF frequencies with applications to data communications. One is a four-quadrant analog multiplier which exhibits a 100-MHz bandwidth with a measured linearity error of 0.7% for X and Y inputs of 0.6 and 0.8 V, respectively. The other is a 90/spl deg/ phase shifter which maintains the grain and phase errors of less than 0.5 dB and 3/spl deg/, respectively, for a signal within 40-60-MHz frequency range.

Data network acknowledgement arrangement

Abstract: A method and apparatus for flexibly interconnecting the nodes of a local data network to achieve reliable internodal data transmission while minimizing the extra data processing load on the host processors of each node. An interface processor is provided at each node which controls transmission and reception of data packets and the communication of data from and to the location in node storage associated with the program processes which generate and receive the data. Different protocols are provided for different types of messages and are controlled by the interface processor in order to provide high reliability data transmission where needed. Destination addresses are associated with each data packet to provide flexible routing of data.

Local area voice/data communications and switching system

Abstract: A distributed, digital voice/data communications and switching system for connecting stations which may provide voice-only transmission, data only or voice and data. The system comprises one or more physical nodes, each serving (in an exemplary case) up to about 30 ports (i.e., station interfaces); nodes may be geographically distributed on the user's premises or one or more nodes may be collected together at a common location. The nodes are interconnected via a hierarchical network configuration formed of at least two, generally three, and perhaps even four interlocking networks. The first network is a slotted ring (the "regional" ring) employing coaxial cable to connect the nodes; it carries all control messages transmitted among the nodes, as well as the users' data traffic, using a frame which circulates continuously at about 20 Mbps. The second network is a "star" arrangement carrying PCM-encoded digitized voice traffic; at the hub of the star, in one of the nodes, is a digital voice switch. An optional third network provides a ring-type local area network (the "nodal ring") which connects together a multiplicity of stations at a given node. Each station may include an analog key telephone; further, a personal computer or data terminal may be connected to the phone for transmission purposes. The nodal ring uses frequency division multiplexing to support both analog voice and data transmission over twisted-pair wiring; in the node, the analog voice is digitized and connected to the star network, while digital data is connected to the regional ring for transmission to other nodes. A fourth (so-called "national") ring may be used to interconnect a plurality of regional rings, to allow the system to grow to greater size. Both the hardware and software are modular and may be distributed among the nodes. The software (firmware) comprises a number of processes (or modules) which operate independently of one another and communicate solely by means of messages transmitted over the system's rings and buses internal to the node(s).

Approximate Analysis of Time-Synchronous Packet Networks

Abstract: In this paper, models and analytical techniques are developed to evaluate the performance of the backbone networks of discrete-time linked-cluster packet networks. The theoretical results are validated by extensive computer simulation. The results of this research may be applied to the design of multiprocessor networks, local area networks, and cellular, terrestrial, and satellite packet networks.

Compressed quantized image-data transmission technique suitable for use in teleconferencing

Abstract: A technique for transmitting compressed quantized image-data from a transmitter to a receiver over a limited bandwidth communication channel employs temporal differential pulse code modulation incorporating pyramid image processing spectrum analyzers and synthesizers. This technique permits the selective elimination by data-compression of only those portions of the original image information which contribute least to the perception of image quality by a viewer of a synthesized display image at the receiver.

Programmable control system for glassware forming machines

Abstract: A control system for the control of a multisection glassware forming machine in a manner which enables totally independent operation of any section regardless of the status of remaining sections. The control program for each section is stored in unalterable, read-only memory within a local computer associated respectively with each section. Each local computer is provided with at least two communication ports. A local terminal may be selectively connected to any local computer via one of the communication ports to enter and display timing setting data. A machine terminal or machine supervisory computer may be selectively connected to any local computer through the other one of the ports. A bidirectional communications interface enables data transfer between the selected local computers and selected data input/output devices.

Method and apparatus for backing up data transmission system

Abstract: A data transmission system is disclosed in which a plurality of data transmission service units (3, 4) and terminals (9) are connected to a data trans­mission line (8) such as in-line or local area network and one of the units is used as an actual service unit and another unit is used as a backup unit. In the service unit, a plurality of processors (5A, 6A, 5B, 6B) of the service units mutually monitor the validity and normality of the operations of others, and if an error is detected, the data transmission control operation of the service unit is frozen and the service unit is disconnected from the data transmission line. In the backup unit, when it detects the freezing of the data transmission control operation of the service unit through the data transmission line, it starts the data transmission control operation in place of the service unit. The backup method and apparatus are applicable to a POS system and a multiple computer system.

Data modem with adaptive synchronized speed change

Abstract: A method for changing the data transmission rates in a synchronous data communication system including a first modem and a second modem coupled together through a transmission channel, the transmission channel including a first path for transmissions from the first modem to the second modem and a second path for transmission from the second modem to the first modem, includes the steps of determining, at the first modem, that the second path of the transmission channel is adequately high in quality to support an increase in transmission rate. Next it is determined, at the second modem, that the first path of the transmission channel is adequately high in quality to support an increase in transmission rate. A training sequence is then transmitted at an increased transmission rate from the second modem to the first modem. Next, a training sequence is transmitted at the increased transmission rate from the first modem to the second modem.

Method for operating a data processing system

Abstract: A method is disclosed for the operation of a data processing system for motor vehicles including at least two computers and a line connecting the computers for the transmission of messages. This line permits a fast and reliable data transmission between the computers installed in the motor vehicle, taking into account the specific requirements of a controller-coupling in the motor vehicle. An embodiment is provided which describes in detail the interface between the individual computers and the line linking the computers, and with the aid of which a controller-coupling is realized in the vehicle.

Digital transmisson including add/drop module

Abstract: In a transmission system, adding and/or dropping any one or more of a plurality of digital signals of one or more digital transmission bit rates is facilitated by employing a un- lque transmission signal in which data words associated with Individual digital signals are arranged in prescribed groups. The transmission signal data word groups are obtained by formatting the individual digital signals to be combined into a unique channel frame format common to all of the digital signals and by employing a unique one-step multiplexing process to insert digital words from the channel frames into the group of data word positions in the transmission signal associated with the particular signal being combined. Consequently, digital signals may be added to the transmission signal by formatting them into the common channel frame format and, then, inserting the digital words therefrom in the one-step multiplexing process into an associated group of data words positions in the transmission signal. Digital signals are dropped from the transmission signal by extracting associated groups of data words from the transmission signal, identifying the corresponding channel frames and deformatting the data bits from channel frames of corresponding digital signals being reconstructed.

Self-adaptive hybrid data transmission

Abstract: The invention relates to data transmission, especially between a satellite and land-mobile terminals, which is self-adaptive and hybrid, i.e. a system which encodes data in sets of blocks including redundant symbols and redundant blocks, and provides automatic retransmission of lost data blocks and in parallel, correction of detected errors within received blocks. In the embodiment described, the data is encoded in a Reed-Solomon code in a two-dimensional mode. Each set of data is transmitted automatically and continuously; the receiver registers the data received and corrects detected errors in the relevant block up to a threshold number; if the number of detected errors in the block exceeds the threshold, the block is erased. When sufficient data has been received to decode the complete set of blocks, the receiver transmits a reception acknowledgement signal repeatedly. When the transmitter receives the reception acknowledgement signal, it interrupts transmission of the current set and starts transmitting the next set, on reception of which the receiver halts transmission of the reception acknowledgement signal.

Data transmission security arrangement for a plurality of data stations sharing access to a communication network

Abstract: An arrangement for securing data transmissions to and from one data device from among a plurality of data devices sharing a common interface is disclosed. In a data communication network, a master communication bus connects to a plurality of data transmitting and receiving devices via a single interface. The disclosed arrangement provides circuitry in the common interface which generates a jamming signal to all devices connected to the interface except for that one device which is either transmitting or receiving a data-transmission. The jamming signal inhibits all the connected devices from monitoring and detecting the data transmission processes of the interface. The one transmitting and receiving device is enabled to either transmit or receive data during the generation of the jamming signal which ensures a secure data transmission and prevents "eavesdropping" by the other devices. The jamming signal is removed at the conclusion of the data transmission to or from the one device.

Computer control system

Abstract: A computer control system, especially a flight control computer system, comprises a series of computer modules operating in parallel and asynchronously to carry out respective parts of an overall control algorithm for a series of items to be controlled, each computer module having a data transmission port connected via a broadcast line to a respective input port of each other computer module so that communication between modules is achieved by any of the modules broadcasting asynchronous data messages onto its broadcast line for the messages to be received by any other modules which require them.

Slot Synchronization in Optical PPM Communications

Abstract: Maintaining slot clock synchronization in a baseband pulse position modulated (PPM) communication link is vital to its performance. This paper examines the slot clocking design associated with a direct detection, photodetecting optical PPM system. Although theoretical PPM synchronizers for optical links have been derived in the past, there is still interest in finding more practical, simpler, and easier-to-implement clocking subsystems. In this paper several types of practical slot synchronizers are considered. A basic design involving analog correlators and slot gating is presented, along with an indication of its performance. Several alternative designs are also presented, including digital synchronizers in which time samples are used for loop control. The advantage in digital systems is that more extensive processing can be handled in software, allowing the loop to perform closer to the ideal. Design procedures for digital clocking are presented, and optimal laser pulse shaping and filtering are discussed. Performance in terms of loop models and tracking error variance is included.

Process transparent multi storage mode data transfer and buffer control

Abstract: An interprocess communication facility in a processor system provides for communication of data between at least two processes. The facility supports a plurality of different data transfer modes which are provided by storage management services of the processor or processors. A process interface provides a common interface for each communicating process to select data transfer modes independently of the data transfer mode chosen by the other communicating process. A data access control function is coupled to the process interface and to the storage management services. The data access control function controls the use of the storage management services as a function of the transfer modes chosen by the communicating processes. It is transparent to the processes as to which transfer mode was chosen by each other.

Rotating data transmission device

Abstract: A rotating data transmission device has a rotating part, such as a rotor, and a stationary part, such as a stator. One of the parts is in the form of a waveguide coupled to a set of transmitters. The other part has a set of receivers associated therewith, the number of transmitters being different from the number of receivers. The transmitters and receivers are respectively located at positions which guarantee continuous data transmission with no interruptions during relative movement of the parts. This results during transmission in certain waveguide sections which are not always required for primary data transmission, thus making those sections available for use as secondary transmission paths. The device is particularly suited for use in a computer tomograph apparatus for transmission of measured data and control data at a high rate.

Higher order digital transmission system including a multiplexer and a demultiplexer

Abstract: Higher order digital transmission system including a multiplexer having N parallel inputs to which tributary input signal streams are applied, and a demultiplexer having N parallel outputs from which the tributary signal streams are taken. The signal processing operations, such as scrambling, justifying, line coding, error monitoring and word synchronization are effected before the multiplexer and after the demultiplexer, consequently not at the full line rate.

Time-division multiplexing communication system for performing a plurality of communications having different data speeds

Abstract: A communication system in which a plurality of terminal devices connected to a loop transmission line perform data transmission/reception in a time-division multiplexing manner by using a communication frame circulating the transmission line. The communication frame being constituted by a plurality of sub-frames, each including a plurality of time slots. Each of the terminal devices is arranged to perform data transmission/reception using a designated time slot in a designated sub-frame. All the sub-frames in the communication frame are allotted to a terminal device of a high capability of data transmission, while less than all of the sub-frames are allotted to a terminal device of a low capability of data transmission. A plurality of low speed terminal devices, to which sub-frames different from each other have been respectively allotted, commonly use a time slot of the same number, so that each of the time slots in the communication frame can be effectively utilized.

Data terminal interface circuit to a telephone transmission line

Abstract: At a transmission line (La', Lb') connected with telephone station equipment (Tel) via a lowpass filter (TP), via which telephone station signals are transmitted in a first frequency range, there is connected via a line transformer (U3) a data terminal (DG) which is able to receive and to send data signals in a second frequency range above the first frequency range. On its side toward the transmission line (La', Lb'), the lowpass filter (TP) has a capacitive termination (C7) which is rated so that its a-c resistance is in the order of magnitude of or preferably less than the characteristic impedance of the data transmission line in the second frequency range.

Communication bus interface

Abstract: A communication interface for controlling the transfer of data between a host processor configured to process data of a first length and a remote storage member configured to store data of a second length includes a bus controller for transferring data between the interface and the remote storage member, a data transfer member for controlling the transfer of data between the host processor and the interface, and a control processor for controlling operating of the bus controller and the transfer member. A first storage member stores data words of said second length and sequentially outputs the data words over a communication bus to the host processor configured to transmit data words of said first length. A second storage member stores data representing the operating status of the transfer member and the bus controller, enabling the control processor to monitor the status of the transfer member and the bus controller.

256 QAM Modem for High Capacity Digital Radio System

Abstract: This paper presents topics related to the 256 QAM modem for high capacity digital microwave radio. Specifications for modem circuitry are derived from the allowable carrier-to-noise ratio degradation point of view. In this process, various degradation factors are categorized so that the same evaluation is possible. Two representative circuits, the automatic threshold control (ATC) and carrier recovery circuits, of particular importance for developing a 256 QAM modem, are presented. For the ATC circuit, the operation principle as well as the presence of the false-lock phenomenon and its evasion method are described. The prototype 256 QAM modem performance indicates the prospect of a 400 Mbit/s 256 QAM modem.

Performance of homodyne detection of binary PSK optical signals

Abstract: This study evaluates the performance of an optical receiver for binary phase shift keyed (BPSK) signals in the presence of noise originating from the photodetectors and the phase fluctuations of the optical sources. Analysis of the homodyne detection process shows that the performance is degraded by two effects: One due to the phase error fluctuations of the recovered carrier and the other due to reduction of the energy per bit available for data recovery. The resulting power penalty can be minimized by dividing in an optimal way the received optical signal between the carrier recovery and the data recovery circuits of the receiver. The minimum penalty thus obtained depends on the 3-dB linewidth and on the transmission rate. For example, a penalty of 0.5 dB, relative to the quantum limit of 9 photon bit needed to achieve a BER of 10-9, imposes a minimum transmission rate of about 180 Gbit/s when the optical source has a 3-dB linewidth of 20 MHz.