Showing papers on "Data transmission published in 1985"

Analysis and Simulation of a Digital Mobile Channel Using Orthogonal Frequency Division Multiplexing

Abstract: This paper discusses the analysis and simulation of a technique for combating the effects of multipath propagation and cochannel interference on a narrow-band digital mobile channel. This system uses the discrete Fourier transform to orthogonally frequency multiplex many narrow subchannels, each signaling at a very low rate, into one high-rate channel. When this technique is used with pilot-based correction, the effects of flat Rayleigh fading can be reduced significantly. An improvement in signal-to-interference ratio of 6 dB can be obtained over the bursty Rayleigh channel. In addition, with each subchannel signaling at a low rate, this technique can provide added protection against delay spread. To enhance the behavior of the technique in a heavily frequency-selective environment, interpolated pilots are used. A frequency offset reference scheme is employed for the pilots to improve protection against cochannel interference.

Spatial TDMA: A Collision-Free Multihop Channel Access Protocol

Abstract: In this paper we define a broadcast channel access protocol called spatial TDMA, which is designed specifically to operate in a multihop packet radio environment where the location of the nodes of the network is assumed to be fixed. The defined protocol assigns transmission rights to nodes in the network in a local TDMA fashion and is collisionfree. Methods for determining slot allocations are developed, and an approximate solution is given for determining the assignment of capacities for the links of the network that minimizes the average delay of messages in the system.

Data and voice communications system

Abstract: A high speed and relatively error free communications system is disclosed which enables the high speed transmission of data at a 19.2 kilobit per second rate. The data is transmitted over the same communications medium as voice transmissions, the data transmission being virtually imperceptible to the user of the analog telephone system. Connection to and from the data terminals is made through an RS232C interface. A spread spectrum technique is utilized which "whitens" the signals of the data terminal regardless of whether the terminal is idle, transmitting or receiving data. Virtual error free transmission is achieved by interleaving bits, so that noise does not destroy the data, and by error detection and correction techniques which assure that the data, as received, is identical to that transmitted. By using a variable pseudo random code, privacy of data communications are enhanced and cross-talk is substantially eliminated. The resulting system is one that can use a single twisted pair wire for transmission and is capable of transmitting data at a high rate of speed while leaving the analog voice transmission resident and unaffected on the line.

Digital transmission over cross-coupled linear channels

Abstract: For a multiuser data communications system operating over a mutually cross-coupled linear channel with additive noise sources, we determine the following: (1) a linear cross-coupled receiver processor (filter) that yields the least-mean-squared error between the desired outputs and the actual outputs, and (2) a cross-coupled transmitting filter that optimally distributes the total available power among the different users, as well as the total available frequency spectrum. The structure of the optimizing filters is similar to the known 2 × 2 case encountered in problems associated with digital transmission over dually polarized radio channels.

Cellular voice and data radiotelephone system

Abstract: A data message transmission system for a cellular radiotelephone system provides protection against data loss caused by multipath fade and subscriber unit handoff. Data from data terminal equipment (801) to be transmitted is converted by a system data processor (805) and radio signalling interface (807) into a format compatible with radio transmission prior to transmission by a transceiver (809). The data is reconverted to its original format following reception. Handoff is accomplished by halting the data transmission prior to handoff and resuming data transmission after handoff. Call supervision occurs via busy-idle bit coding performed in radio signalling interface (807).

Digital transmission over cross-coupled linear channels

Abstract: For a multiuser data communications system operating over a mutually cross-coupled linear channel with additive noise sources, we determine the following: (1) a linear cross-coupled receiver processor (filter) that yields the least-mean-squared error between the desired outputs and the actual outputs, and (2) a cross-coupled transmitting filter that optimally distributes the total available power among the different users, as well as the total available frequency spectrum. The structure of the optimizing filters is similar to the known 2 × 2 case encountered in problems associated with digital transmission over dually polarized radio channels.

Analog and digital telemetry system for an implantable device

Abstract: In an implantable device, transmission and reception of digital information is accomplished as well as the transmission and reception of analog information. The analog signal is FM modulated for transmission and the digital signal is phase modulated for transmission. The FM modulated signal is used as a clock in the phase encoding of the digital signal and thus provides a signal simultaneously carrying analog and digital information. Means for reception of the analog and digital information is taught. The use of PSK (phase shift keying) as the phase modulation scheme for transmission and reception is also taught.

Equalizing without altering or detecting data

Abstract: For terrestrial digital radio systems that use Quadrature Amplitude Modulation, the idea of adapting equalizers to multipath distortion, without relying on accurate data estimates, is attractive. Prompt adaptation following a severe fade, when accurate data estimates are unavailable, is useful for reducing outage time. To avoid processing and administrative overhead, the adaptation method should not involve violating the transmitted signal with the insertion of equalizer training signals. We approach this kind of equalization by building on an algorithm of D. Godard (IEEE Transactions on Communications, November 1980)1 that was devised for voiceband polling networks. The method involves a very simple tap update procedure. However, the technique lacks the foundation of the years of analysis and experimentation that underlie least-mean-square adaptation algorithms. The main purpose of this paper is to present new findings, including (1) a proof that the algorithm, thought to require special equalizer initialization, converges regardless of initialization (this offers useful flexibility in digital radio systems, since, after a severe fade, the algorithm could start with any tap misalignment); (2) a preliminary look at convergence speed suggesting the possibility of significant outage reduction; (3) an algorithm that provides phase coherence (the original algorithm requires a follow-on phase-locked loop); and (4) an algorithm for cross-polarization cancellation as well as equalization.

Data communication network

Abstract: A network for data transmission between nodes interconnected by transmission paths on which a predefined data signal is continuously transmitted to sequentially reach each node. Data traffic is controlled by apparatus responsive to receiving the predefined data signal a predetermined number of times and generating node signals each varying in time in accordance with data traffic on the network to control node access thereto. Multiple nodes are enabled to mutually write data onto the network proportional to the communication network data traffic independent of the network location of the predefined data signal.

Analysis of Traffic Access Control Strategies in Integrated Service Networks

Abstract: A common digital transmission facility provides service to a community of heterogeneous users generating traffic with differing intensity, message length, and bit rate. In order for this type of integrated communication system to handle its traffic demands with high efficiency and flexibility, close control of access and switching at the input node is required. We propose, analyze, and compare two different strategies for managing the access of two types of traffic, a blockable wide-band (WB) type of traffic and a queueable narrow-band (NB) type of traffic, sharing the transmission resource dynamically. The first strategy assigns preemptive priority to the WB traffic over the NB traffic, whereas the second strategy employs a wide-band to narrow-band bit rate compression mechanism. Exact analytic models are developed, and solution methods are presented and implemented. It is shown that the best combined performance is obtained when the two strategies are adaptively combined according to the offered load.

Method and system for transmitting digitized voice signals as packets of bits

Abstract: A method of transmitting digitized voice signals as packets of bits in a digital transmission network to which a plurality of terminals acting as sources of voice signals are attached. The method includes, at the transmitting end and for each source, the steps of: a dividing the signal into successive, digitally-coded segments; performing a so-called source activity detection; and assembling the bits resulting from the coding operation into packets, each packet being provided with a header containing, in particular, a parity bit whose logic value is modified whenever an inactivity or long pause is detected. At the receiving end, detection of a change in the value of said parity bit causes the delivery of a packet of bits to the decoder/synthesizer to be delayed by a given time interval called retention delay.

Flow control arrangement for the transmission of data packets to a communication network

Abstract: A data transmission flow control arrangement for controlling the flow of data packets to a network as tramsmitted by one or more data transmitting and receiving devices via an interface is disclosed The disclosed flow control arrangement provides circuitry in the interface responsive to the storage capacity of a buffer included in the interface If the buffer contains sufficient space to store a data packet of maximum length, data transmissions continue unencumbered However, if the buffer contains insufficient space to accomodate a data packet of maximum length, the specialized circuitry of the interface responds to this condition and applies a signal to all of the associated transmitting and receiving devices of the interface The jamming signal simulates the conditions associated with a busy network and therefore, inhibits the transmission of data from any of the associated transmitting and receiving devices The specialized circuitry of the interface terminates the application of the jamming signal to all associated transmitting and receiving devices when the buffer again contains sufficient space to accommodate a data packet of maximum length

Vehicular data transfer communication system

Abstract: A data transfer communication system capable of handling both node-to-node data transfer messages originating at any transmitter and transmitted to a specific receiver on the network and functional command messages originating at any transmitter and broadcast transmitted to an unspecified number of receivers on the network. Receivers are programmed to receive and acknowledge receipt of correspondingly addressed node-to-node type messages and certain correspondingly addressed functional command type messages with their unique addresses in a predetermined field location of the transmitted message. By utilizing pulse width modulation techniques, binary logic signals and a unique start signal are defined and have a dominant hierarchy that allows for bit-wise contention of the common data bus. In that manner, when contention of the data bus is resolved a higher priority message continues to be transmitted while losing contender delays its transmission until after the higher priority message is completed.

Cascaded information processing module having operation unit, parallel port, and serial port for concurrent data transfer and data processing

Abstract: In a data transmission apparatus, a plurality of data processing modules are used and required sequence setting is performed to a port sequencer of input/output ports of each data processing module. The daisy chain transfer of the selective data transfer, the load distribution data transfer, the collective data transfer is combined between the data processing modules, thereby the data transmission is performed efficiently at high speed.

Digital signal transmitting system

Abstract: PURPOSE:To make connection between devices simple, simplify circuit configuration and make the device small and light by transmitting digital signals using three signal lines, i.e. a data transmission request signal line, a data signal line and a clock transmitting line. CONSTITUTION:A data transmission request signal line 3 is connected from an output port P03 of a microprocessing device 15 in a device 2 to a device 1 through a protective resistance r3. In the device 1, the signal is sent to an input port Pi1 of a processing device 11 through a protective resistance r1. On the other hand, a data transmitting line 4 transmits two-way signals between the devices 1 and 2. For instance, when a signal is sent from the device 1 to 2, the signal is connected from an output port P01 to the device 2 through an open collector driver 12. In a clock transmission signal line 5, clock outputted from an output port P02 of the device 11 of the device 1 is connected to the device 2 through an open collector driver 13, and connected to an input port Pi3 of a device 15 through a pull-up resistance R3 and a protective resistance R5.

Packet and circuit switched communications network

Abstract: A telecommunications network (Fig. 1) being operable as a packet switch and as a circuit switch is comprised of a plurality of units including a call controller unit. Each of the units is connected in common to data (607), address (610), and control leads (221, 224, 225, 613-618) of a bus, the data leads being commonly available for signal transmissions of both call control signals between the call controller unit and the other units and communications signals between calling and called ones of the other units. A bus controller (Fig. 2) is connected to the units by way of the address and control leads for arbitrating access to the data leads by the units, so that only one unit may transmit at any one time. The bus controller includes, a poll circuit (300) for polling the units for asynchronous transmission requests, a grant circuit. (300) being responsive to the requests, for granting access to the data leads for an indefinite period of time as required for transmission of a data packet from one of the units, and a synchronous cycle circuit (400), being responsive to a synchronous request signal from any of the units, for generating a synchronous cycle signal for inhibiting data packet transmission and enabling synchronous data transmission via the data leads during a predetermined period of time.

Image data management system

Abstract: Digitized image data provided by plural diverse non-destructive test apparatus is organized in a common format and routed, via a high speed continuous ring-type data transmission network, to a mass data storage system for redundant storage. Stored image data retrieved from storage may be placed on the network for transmission to a display console for image recreation. Through the use of group addressing, non-image data processing devices may use the data transmission network without establishing an interactive relationship with the storage system.

Broadband digital transmission systems

Abstract: A broadband digital transmission system enables high bit rate data stream to be transmitted over low bit rate telephone networks. A high bit rate stream of data from a source (2) is distributed by a distributor (4) into six separate streams to provide six low bit rate streams of data. A call unit (6) establishes six channel communication with a receiver (20) and the six data streams are fed in parallel along the six channels. A reassembler (34) receives the six low bit rate streams and reconstructs them to produce the original high bit rate stream of data.

Timing Recovery in Digital Subscriber Loops

Abstract: Tradeoffs in the design of the timing recovery functions in a subscriber loop receiver are analyzed. The techniques considered are applicable to both the echo cancellation (EC) and time compression multiplexing (TCM) methods of full duplex transmission. Emphasis is on those techniques that lend themselves to implementation in MOSLSI technology, where the objective requirement is that timing recovery be implemented on a sampled-data signal (with the minimum possible sampling rate where EC is used). The wave difference method (WDM) for timing recovery appears to be the best candidate. A detailed study of its performance is carried out analytically and by computer simulation for the case of binary and alternate mark-inversion (AMI) line coding. A closed form expression describing the binary jitter performance of the WDM and its continuous time counterpart, the spectral line technique, is used to compare the two techniques. Analytical and simulation results for recovered phase and jitter are presented for various cable pulse responses carefully chosen to represent worst-case or nearly worst-case conditions. Two methods for including frequency detection in the WDM, the quadricorrelator and the rotational detector, are also simulated.

Network multiplex structure

Abstract: A time-division multiplexed digital transmission system which utilizes single stage multiplexing and demultiplexing for both synchronous and/or asynchronous bit streams from tributaries of widely differing bit rates. This is achieved by bit stuffing each of the tributaries so as to establish a harmonic relationship at their channel level and then at their tributary level of all the bit streams being multiplexed.

Data transmission system

Abstract: not available for EP0039036Abstract of corresponding document: US4451886The present invention is related to bus extender circuitry for data transmission from a first bus at a first site to a second bus at a second site, includes a first transceiver at the first site, a second transceiver at the second site and a data and control signals transmission medium interconnecting both transceivers. The first transceiver receives data signals and interacts by means of control signals with the first bus which has data and control lines connected to a data source and possibly also to one or more receivers all located at the first site. The second transceiver receives data signals and interacts, by means of control signals, with the first transceiver to transmit data and control signals to the second bus; the second transceiver has data and control lines connected to one or more receivers at the second site.

Data acquisition system

Abstract: A data collection station (2) is connected via a communications link (6) to a data acquisition station (4) at which data relating to the operation of, e.g., gaming machines (18) is collected by data acquisition units (22) and sent to a central communications unit (12) in response to requests therefrom. Each request comprises a poll number and an identification number associated with the acquisition unit (22). A new acquisition unit programmed with the poll number zero can be added to the system. The communications unit (12) detects the new acquisition unit (22), assigns it a new poll number and records its identification number. The communications unit (12) shares a telephone line with a telephone (14) and is only operable to answer incoming calls at predetermined times set by the collection station (2). A portable interrogator unit can be coupled to the communications unit (12) to establish communication therewith instead of using the communications link (6). The communications unit (12) can be switched from a first mode to a second mode in which the data transmission rate used by the communications unit (12) is unsuitable for the modem used to connect the unit (12) to the communications link (6). Accordingly, when in the second mode the communications unit (12) can only communicate with the portable interrogator unit. At least one operation of the communications unit (12) can only be carried out while it is in its second mode.

Cross-polarization cancellation and equalization in digital transmission over dually polarized multipath fading channels

Abstract: A theory for data-aided equalization and cancellation in digital data transmission over dually polarized fading radio channels is presented. The present theory generalizes and extends previous work by admitting decision feedback structures with finite-tap transversal filter implementations. Subject to the assumption that some past and/or future data symbols are correctly detected, formulas and algorithms for evaluating the least mean-square error for different structures are presented. In a sequence of curves we evaluate and compare the performance of various structures for a particular propagation model and several fading events. We find improvement in performance for decision feedback over linear equalization. More importantly, we discovered that in this application, as in the single-channel transmission case, decision feedback/ canceler structures are much less sensitive to timing phase than linear equalizers.

Radio wave data transmission watch device

Abstract: A radio wave data transmission apparatus comprises a plurality of switches, a data converter and a transmission section The switches are selectively activated by a finger tip being moved as if to write a character, thereby providing data showing a character The data converter converts this data into radio wave signals These signals are transmitted from a transmission section

Local and remote bit error rate monitoring for early warning of fault location of digital transmission system

Abstract: In-service line monitoring apparatus to detect and isolate marginal and failed digital transmission equipment within a digital telecommunication system having at least two end terminals. At selected terminal and repeater locations, a digital error detector monitors the bit error rate for each location. The detected BER is truncated to include at least the most significant digit and the exponent of the BER. The truncated BER is stored and then encoded for transmission back to the command center usually located at an end terminal. At the one end terminal the encoded BER is stored and displayed upon request. By being able to monitor the truncated BER at any location or direction, maintenance personnel are able to determine when a link in the system begins to deteriorate well before a complete path failure occurs.

Compatible am broadcast/data transmission system

Abstract: A system for transmitting a composite signal comprising a data transmission signal component and an AM broadcast signal component. The broadcast signal component may be monophonic or stereophonic. The level of the data signal component is made a function of the modulation level so that the data signal is masked by the program modulation and, therefore, AM radio listeners will not be disturbed by the data signal. The rate of data transmission, in one embodiment, is reduced as the level of the data signal is reduced. The data signal is in quadrature with the AM carrier so as to minimize detection of the data signal by an envelope demodulator. Suitable data receivers are also disclosed.

Digital telephony and network integration

Abstract: A network in transition. Speech digitalization fundamentals. Waveform coding. Parametric and hybrid coding. Digital techniques in the telephone network. Digital transmission. Digital cellular radio. Microwave transmission. Satellite transmission. Fiber-optic transmission. Digital switching architecture. Operational switching systems. The evolving switched digital network. The integrated services digital network (ISDN). Closing the loop. Appendices. References. Glossary. Index.

Parallel processing computer including interconnected operation units

Abstract: A plurality of operation units are connected to one another. The operation units include a processor, a buffer memory, and a data transfer control circuit connected between the processor and the buffer memory for controlling the data input-output with the buffer memories in the other of the operation units. The buffer memories and the data transfer control circuit are connected with one another by data buses, respectively.

Signal transmission apparatus for a multiple channel system and method for using the same

Abstract: Signal transmission apparatus is provided for a communications system having a plurality of transmitters for transmitting information signals over any one of several transmission channels, and further having a plurality of receivers for receiving the information signals over any one of the transmission channels. In order to establish a selected transmission channel between a particular transmitter and a particular receiver, the transmitter selects an unoccupied transmission channel and transmits thereon a code identifying the receiver using a wide band signal for high speed bit transmission. When the receiver detects the presence of the identifying code over a particular channel, it first determines that the transmitter is the particular transmitter and, if so, establishes the transmission channel therebetween. The transmitter confirms that the transmission channel has been established, and then continues to transmit the identifying code repeatedly over the transmission channel using a narrow band signal with a low bit transmission rate. Both the wide band and narrow band signals containing the identifying code are included within the audio signal transmission band, so that no extra bandwidth is required for transmission of the identifying code.

A multiprocessor architecture for two-dimensional digital filters (computer, signal, processing, image, parallel)

Abstract: Multiplication, addition and data transfer are the primary operations required for digital filtering. It is important to minimize data communication requirements (data transfer) as well as exploit inherent parallelism for algorithms in order to implement them in real-time with the use of a multiprocessor system. This research is oriented toward the development of a computationally efficient algorithm for digital filtering. A state-space representation is derived for general order one-dimensional and two-dimensional digital filters. An algorithm is then developed from this representation. This algorithm not only exposes the inherent parallelism for these filters but also reduces data communications requirements. A software package for spatial domain IIR digital filters has been implemented on VAX-11/780. This software package is based upon the state-space representation and was used to filter various images to test the performance of the algorithm. A new generic computational primitive is introduced for the implementation of any arbitrary order one-dimensional or two-dimensional FIR or IIR digital filter. A computational structure based upon this primitive has very high efficiency and very low data transfer and storage requirements. It can form the basis for a programmable special purpose chip for digital signal and image processing applications. A new multiprocessor architecture for real-time image processing is developed with each processing unit in the network implementing the computational primitive. This multiprocessor system has a simple control scheme and a simple interconnection network. Thus, it avoids the bottleneck associated with traditional parallel computers and multiprocessor systems.