Showing papers on "Communication channel published in 1971"

Wire routing by optimizing channel assignment within large apertures

Abstract: The purpose of this paper is to introduce a new wire routing method for two layer printed circuit boards. This technique has been developed at the University of Illinois Center for Advanced Computation and has been programmed in ALGOL for a B5500 computer. The routing method is based on the newly developed channel assignment algorithm and requires many via holes. The primary goals of the method are short execution time and high wireability. Actual design specifications for ILLIAC IV Control Unit boards have been used to test the feasibility of the routing technique. Tests have shown that this algorithm is very fast and can handle large boards.

Viterbi Decoding for Satellite and Space Communication

Abstract: Convolutional coding and Viterbi decoding, along with binary phase-shift keyed modulation, is presented as an efficient system for reliable communication on power limited satellite and space channels. Performance results, obtained theoretically and through computer simulation, are given for optimum short constraint length codes for a range of code constraint lengths and code rates. System efficiency is compared for hard receiver quantization and 4 and 8 level soft quantization. The effects on performance of varying of certain parameters relevant to decoder complexity and cost is examined. Quantitative performance degradation due to imperfect carrier phase coherence is evaluated and compared to that of an uncoded system. As an example of decoder performance versus complexity, a recently implemented 2-Mbit/s constraint length 7 Viterbi decoder is discussed. Finally a comparison is made between Viterbi and sequential decoding in terms of suitability to various system requirements.

Conflict Measurement in the Distribution Channel

Abstract: Conflict among firms in distribution channels is inherent, pervasive, and potentially disruptive. This article presents an approach to measuring dyadic conflict intensity. Conflict is related to a ...

Experimental study of channel patterns.

Abstract: RIVER channel patterns are described as being braided, meandering, or straight1 with braided rivers having steeper gradients than meandering rivers at the same discharge2. Recent experimental studies also suggest that straight channels have gentler gradients than meandering channels for the same discharge3. The difference in slope has at times been assumed to be the cause of the difference between braided and meandering channels, although braided channels have also been attributed to rapid variations in discharge, high sediment load, or erodible banks4. All of these explanations are plausible, and the last two can be related to the higher velocity and greater tractive force associated with steep gradients.

An Adaptive Decision Feedback Equalizer

Abstract: An adaptive decision feedback equalizer to detect digital information transmitted by pulse-amplitude modulation (PAM) through a noisy dispersive linear channel is described, and its performance through several channels is evaluated by means of analysis, computer simulation, and hardware simulation. For the channels considered, the performance of both the fixed and the adaptive decision feedback equalizers are found to be notably better than that obtained with a similar linear equalizer. The fixed equalizer, which may be used when the channel characteristics are known, exhibits performance which is close to that of the optimum, but impractical, Bayesian receiver and is considerably superior to that of the linear equalizer. The adaptive decision feedback equalizer, which is used when the channel impulse response is unknown or time varying, has a better transient and steady-state performance than the adaptive linear equalizer. The sensitivity of the receiver structure to adjustment and quantization errors is not pronounced.

Dynamic channel assignment in high-capacity mobile communications systems

Abstract: Computer simulations of high-capacity mobile radio systems using different channel assignment philosophies are described. These simulations initiate call attempts and move vehicles about randomly according to prescribed statistical distributions. Base stations and radio channels are assigned to serve mobiles and system operating statistics are accumulated. Relationships between systems parameters obtained from the simulation are presented. Performance of a dynamic channel assignment system (DYNSYS) which has all channels available at all base stations is compared with performance of a fixed-channel assignment system (FIXSYS) which reserves channel subsets for use at specific base stations. For uniform spatial distributions of call attempts and 40-channel systems with reuse intervals of four base station radio coverage areas, the DYNSYS outperforms the FIXSYS at blocking rates up to 13 percent. For example, at a 3 percent blocking rate the DYNSYS provides 20 percent more calls “on” in the system.

Channel heating in return‐stroke lightning

Abstract: A computer code for calculating radiation flow and hydrodynamic motion has been used to investigate the radial-temperature and time-temperature profiles of an air channel heated by a single return stroke of lightning. The investigation used a novel model in which input heat releases were computed from calculated electrical conductances of channel zones and from the experimentally determined information on the electrical current in a single return stroke. Although no experimental information on profiles was available for comparison, apparently realistic temperature profiles of the lightning channel were deduced. However, the magnitudes of the theoretical channel temperature and of its variation with time are in good agreement with experimental observations. The calculated total energy dissipation per unit length of channel is also in fair agreement with experimental estimates.

Dynamic program control for channel assignment in mobile communication systems

Abstract: To determine a channel which may be advantageously assigned to a mobile user via a preferred one of a plurality of spacially remote base stations, a central control computer considers the status of use of all communication channels utilized by the system. All of these channels constitute but a single set, so any of them may be assigned to a mobile user by way of any base station. Thus, the allocation procedures utilized by the computer feature optimization tests which insure minimal station-to-station interference with optimal "packing" and re-use of the channels over the entire system.

Madagascar's Paleoposition: New Data from the Mozambique Channel.

Abstract: The main paleopositions that have been proposed for Madagascar are examined after a recent geological and geophysical survey in the Mozambique Channel. Results from that survey show a north-south ridgelike feature and favor the theory that Madagascar fitted against Somalia rather than against Mozambique to the west.

Input/output control

Abstract: An input/output control system for a data processor which controls the transfer of data from I/O devices (such as disks or drums in which data are recorded in fixed sector lengths and in which the devices are capable of signalling when they reach any desired sector). A plurality of channels for scheduling and executing input/output programs are provided, each capable of being logically connected to a device through a cross-point switch. I/O tasks are placed in a queue common to the channels. Channels extract tasks from the queue and execute channel programs associated with the tasks. During latent periods of devices channel programs corresponding to the devices are queued in device queues. This frees a channel to go on to another task. When a device is at a point where its program can be continued, any free channel which has access to the device responds, reenters the program by extracting it from the device queue, and resumes execution of the program.

A theoretical melting model for plasticating extruders

Abstract: A theoretical model for melting in plasticating extruders is described. Compared to previous models, this model introduces more accurate and less restrictive assumptions, adds a mass balance on the entire channel, and replaces certain approximate solutions by exact solutions. Flow of the solid bed is represented by a solid bed acceleration parameter, SBAP, which permits solid bed acceleration in a screw compression section. New experimental melting data for a variety of screw designs, polymers, and extruder sizes are presented and compared to the theoretical predictions. With the optimum SBAP, reasonably accurate model prediction of the melting profiles is observed for a wide variety of cases.

The diffraction of tides by a narrow channel

Abstract: A Green's function for a semi-infinite rotating ocean of uniform depth is obtained, and the resulting near and far fields are estimated asymptotically.Given a tide of uniform height at the mouth of a narrow channel on a semiinfinite ocean, the Green's function is used to calculate the diffracted Kelvin and Poincare waves propagating up the channel and into the ocean.

A Cheap Method of Recording Behavioural Events, for Direct Computer-Access

Abstract: A new system is described for recording behavioural events on a time scale, in a form which can be fed directly into a computer. The user presses keys on a keyboard to denote behavioural events. The number of separate events which can be distinguished depends on the quality of equipment used, and can be over 60. The main disadvantage of the system is that no two events can be recorded simultaneously. The information is coded on magnetic tape, using an unmodified single channel domestic tape recorder. The encoding unit is light and battery driven, and together with the tape recorder can easily be taken into the field. The tapes are later played back through a simple interface to a small computer. The computer decodes them, and punches out a permanent paper tape record of which behaviours occurred, and when, to the nearest tenth of a second. These paper tapes can then be fed back into the same or another computer for analysis. In addition to recording discrete events, the system can be used as a simple analogue to digital converter. The main advantage of the system is that it is extremely cheap and easy to make. This is because a very simple frequency code is used, and the computer itself is programmed to perform the whole decoding operation.

Capacity of a continuous memoryless channel with feedback

Abstract: Shannon showed that the capacity of a discrete memoryless channel can not be increased by noiseless feedback. It has been conjectured that this should be true for a continuous memoryless channel, provided such a channel is appropriately defined. We precisely define such a channel from two mathematically different points of view and rigorously prove that its capacity can not be increased by feedback.

Selecting channels of distribution: a multi‐stage process

Abstract: This article explores the options available to a distributor in terms of the suitability of a channel of distribution with regard to the company's product market characteristics. Guidelines are presented for the construction of a channel selection procedure.

Group Codes do not Achieve Shannon's Channel Capacity for General Discrete Channels

Abstract: Elias [9], [10] proved that group codes achieve Shannon's channel capacity for binary symmetric channels. This result was generalized by Dobrushin [7] (and independently by Drygas [8]) to discrete memoryless channels satisfying a certain symmetry condition and having a Galois field as alphabet. We prove that group codes to dnot achieve the channel capacity for general discrete memoryless channels. It therefore makes sense to introduce a group code capacity and to talk about a group coding theorem and its weak converse can be established for several reasonable channels such as the discrete memoryless channel, compound channels, and averaged channels. An example of a channel is given for which Shannon's capacity is positive and the group code capacity is zero. Using group codes, one can therefore expect high rates only for channels with a simple probabilistic structure.

Stored program facsimile control system

Abstract: A facsimile transceiver system incorporating a stored program controller. The stored program controller provides operational control of a scanner and a printer mechanism in conjunction with a communication channel for transmitting and receiving facsimile signals and a condition indicator display for presenting transceiver condition information. The scanner and printer are made to operate with a variety of different formats of control and data signals from a remote facsimile system by associating an appropriate program with the controller. This program instructs the controller to process the control and data signals passing through it between the channel, and scanner and printer in a manner that causes the local facsimile system to operate compatibly with other facsimile equipment at the remote end of the communication channel. By readily varying controller operation with different programs, which can be simply associated with the controller, a single facsimile transceiver is operatable with a range of different remote transceivers, operator characteristics and diagnostic checkouts. Improvements in facsimile efficiency are also readily incorporated in existing equipment by providing the improvement through a new program.

Method and apparatus for homogenizing viscous molten glass

Abstract: SUBSTANCES ARE MIXED INTO LIQUID FLOWING VISCOUSLY IN A CHANNEL OR PASSAGE BY MEANS OF GAS-CURTAIN MIXER DEVICES OF THE KIND TAUGHT IN BRITISH PAT. NO. 1,171,133. TWO SUCH DEVICES ARE USED, EXTENDING TRANSVERSELY OF THE CHANNEL OR PASSAGE AND AT AN ANGLE OF 10 TO 80 DEGREES WITH RESPECT TO THE FLOW OF LIQUID. THE UPSTREAM MIXER DEVICE EXTENDS ONLY ABOUT 88 TO 98.5 PERCENT OF THE WAY ACROSS THE PASSAGE OR CHANNEL; THE DOWNSTREAM MIXER DEVICE EXTENDS ALL THE WAY ACROSS THE CHANNEL. THIS YIELDS AN IMPROVED MIXING ACTION. THE FOREGOING CONCEPT IS APPLIED TO THE MIXING OF COLORANT INTO MOLTEN GLASS TRAVELING IN THE FOREHEARTH OF A CONTAINER-GLASS TANK. THIS REQUIRES PARTICULAR CONDITIONS OF THE USE OF THE MIXER DEVICES WITH RESPECT TO GAS-IMPINGEMENT ANGLE, SPACING BETWEEN THE DEVICES, AND ORIENTATION ANGLE OF THE DEVICES WITH RESPECT TO THE FLOW OF THE GLASS.

Synthetic array processor

Abstract: The method and apparatus for processing bipolar coherent sidelooking radar data to achieve continuous real time synthetic array mapping in the form of focused line-by-line imagery. Received radar data is correlated such that a number of subarrays are vectorially combined with appropriate quadratic phase corrections to continuously form the total synthetic array. Each subarray is accumulated in a recirculating (feedback) channel which applies a linear phase correction and amplitude weighting, which in turn reduces the arithmetic operations required to form the array. The subarrays are updated by continuously subtracting out the oldest data and adding new data to yield continuous line-by-line imagery. Alternate accumulator and feedback channels are employed in an interleaved fashion to minimize the buildup of "round-off" errors which result from digital multiplications. The invention is adaptable to all-range-focusing and operation at various pointing angles.

Delayed Encoding: Stabilizer for Adaptive Coders

Abstract: The decision process in source encoders can be influenced favorably by anticipating future quantizing errors and modifying the quantizer appropriately. This requires that the signal code be delayed slightly from the corresponding input signal sample. As an adaptation of an existing coder, little advantage is obtained [8]. However, the process has a stabilizing influence so that much stronger adaptation algorithms can be used to advantage, increasing the signal to quantizing noise ratio (S/N) markedly. It is believed that this fact is of general applicability, but it is shown herein only for 1-bit coders. A family of 1-bit coders (delta modulators) using exponentially adaptive step size, with two steps of integration in the feedback path has been studied using a special purpose computer facility. Such coders are ordinarily unstable and useless, but with error anticipation a measured S/N advantage of several dB over optimized adaptive coders of previous design is obtained. The study has concentrated on picture signals and an encoding which does not require a separate channel or code to signal changes in the coder. Fig. 8 compares the optimized delayed encoder operation with an optimized adaptive coder without delay. "Optimization" in the former case requires a modification of the feedback network-the use of two steps of integration instead of one. Delayed encoding is not just an improvement for existing differential coders, it promises to be a revolution in coder design.

Encoding technique for enabling a device to process different types of digital information transmitted along a single information channel

Abstract: A data processing system includes a first device which transmits different types of pulse coded digital information along a single channel to a second device for separation and distribution to a number of different outputs. The different types of digital information transmitted are encoded with different pulse widths. The pulse widths for the different types of information are selected to provide highly reliable data transmission. The second device includes a receive section which has a plurality of detectors. Each of these detectors operate to detect only the pulse coded digital information encoded with predetermined pulse widths and pass them to its output. The system accommodates bidirectional transmission and processing of the encoded digital information by including like transmit and receive sections within each device.

An improved microspectrofluorimeter with automatic digital data logging: Construction and operation

Abstract: SUMMARY This paper describes an instrument for microspectrofluorimetry, based on the Leitz microspectrograph. Important features are monochromatic epi-illumination, a reference channel and a measuring system using photon counting with automatic recording of data in digital form. To minimize fading, measurements of fluorescence intensity can be made within as little as 200 msec from the commencement of irradiation.

Method and apparatus for spraying

Abstract: A METHOD AND APPARATUS FOR ATOMIZING AND SPRAYING LIQUIDS SUCH AS FUEL, PAINT OR WATER IN THE FORM OF MINUTE DROPLETS UTILIZING A SMALL AMOUNT OF AIR TO PROVIDE THE ATOMIZING FORCE. THE LIQUID UNDER A PRESSURE OF FROM 30-100 PSI IS CAUSED TO FLOW IN A THIN FILM. STREAMS OF GAS AT A SLIGHTLY HIGHER PRESSURE ARE INPINGED AGAINST THE LIQUID FILM SO THAT THE GAS IS SHEARED INTO MICROBUBBLES WHICH ARE ENTRAINED IN THE LIQUID TO FORM A FROTH IN WHICH THE LIQUID IS THE CONTINUOUS PHASE, AND IN WHICH THE AIR TO LIQUID MASS RATIO IS FROM 0.1 TO 1.6. THE FROTH FLOWS THROUGH A SPACE IN WHICH THE PRESSURE DECREASES AS THE FROTH MOVES TOWARD A NOZZLE. DURING THIS FLOW THE FROTH BECOMES HOMOGENEOUS. THE FROTH IS DISCHARGED THROUGH A NOZZLE WHEREUPON THE AIR BUBBLES EXPLODE RUPTURING THE LIQUID FILM AND CAUSING THE LIQUID TO DISINTEGRATE INTO FINELY ATOMIZED DROPS. THE APPARATUS FOR CARRYING OUT THIS METHOD COMPRISES A LIQUID FILM-FORMING CHANNEL CONNECTED TO A LIQUID INLET LINE SUPPLIED WITH LIQUID UNDER PRESSURE, AN AIR INJECTION CHANNEL TERMINATING ADJACENT TO THE LIQUID FLOW CHANNEL, A FLOW SPACE INTERCONNECTING THE LUQID FILM CHANNEL AND A NOZZLE ORIFICE. IN THE PREFERRED EMBODIMENT THE FILM-FORMING CHANNEL IS ANNULAR WITH AIR BEING INJECTED FROM THE OUTSIDE OF THE CHANNEL. IN A MODIFICATION THE LIQUID FILM-FORMING CHANNEL IS PLANAR WITH AIR BEING INJECTED INTO THE FILM FROM ONE OR BOTH SIDES OF THE CHANNEL.

Communication among computers

Abstract: Multiple computer system in which a control signal manifestation is circulated by a single control line from one computer to the next to indicate that the computer receiving the control signal manifestation may have available to it for communication with another computer a common communications channel. If, upon receipt of a control signal manifestation, a computer desires to transmit via the channel, it "captures" the control signal manifestation. If not, or after a computer has completed its communication, it returns the control signal manifestation to the single control line for passage to the next computer.

On Decoding of Correlative Level Coding Systems with Ambiguity Zone Detection

Abstract: Decoding of a correlative level coding or partialresponse signaling system is discussed in an algebraic framework. A correction scheme in which the quantizer Output includes ambiguity levels is proposed. The implementation and algorithm of error correction is discussed in some detail. An optimum design of the quantizer based on Chow's earlier work is discussed. Both analytical and simulation results on the performance of the proposed decoding scheme are presented. An asymptotic expression for the decoding error rate is derived in closed form as a function of the channel signal-to-noise ratio. This is also compared with the conventional bit-by-bit detection method and the maximumlikelihood decoding method recently studied.

Modification of channel regions in insulated gate field effect transistors

Abstract: Method of producing channel regions in IGFET''s by implanting ions in the gate region through the gate, the gate of polycrystalline silicon material. The method both produces conducting channel regions and removes conducting channel regions. Enhancement mode and depletion mode transistors can be made. Other devices, such as resistors, can be formed simultaneously or sequentially by the implantation step.