Showing papers on "Communication channel published in 1971"

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 ...

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.

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.

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.

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.

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.

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.

Monopulse gain balanced amplification system using pilot carrier techniques

Abstract: A monopulse type receiver utilizing pilot carrier techniques for providing precise angular error information. Four detector cells are arranged in a quadrant configuration for detecting pulses of laser energy, with the output from each cell being delivered to a respective video channel. Each video channel comprises amplification circuitry including an inner loop automatic gain control (AGC) which operates both on noise and the pilot carrier signal to ensure uniformity of response for each video channel. The video channel outputs are fed into respective sample and hold circuits which provide voltage amplitude outputs both to an outer AGC loop and to a pair of command signal normalizer circuits. The outer AGC loop raises or lowers the gain of each of the video channels as required by controlling the amount of pilot carrier signals interjected into the front of the system. The outputs of the normalizer circuits represent ratios of the energy difference in the four channels divided by the sum of the energies of the channels to provide the desired angular information to a gyro head or the like. Pulse presence determination circuits are also provided in order to reject pulses wider than would be expected.

Device and method for simultaneously dispensing different materials from a container

Abstract: A device for simultaneously dispensing two different paste-like materials from the same container includes an outlet member which communicates with the container interior by means of a main channel leading to one of the materials and a secondary channel extending through the outlet member wall and leading to the other material.

Diversity receiver suitable for large scale integration

Abstract: The cost of a diversity receiver is reduced by providing branch circuits which can be fabricated by large scale integration techniques. To this end nonintegrable filters are eliminated and lead connections are minimized. Filtering is provided by a phase-locked loop which passes only the single frequency band to which it is locked. Channel acquisition is achieved by initially swamping all branches with an unmodulated acquisition signal at a frequency selected to cause all branches to lock on one channel. The acquisition signal, which may be introduced at numerous points, is removed after lock-on in order to permit detection of the intelligence modulation.

Profile determining method and system

Abstract: A distance ranging system of conventional design is utilized to measure radial distances transversely to the direction of motion of a vehicle or other object along a right-of-way. Using a high speed rotating transducer element, successive radial scansions are made during the vehicle movement. Each successive radial scansion or sweep is divided into segments or channels, one for every preselected number of degrees of arc in the swept field under examination. At least one channel covers every portion of the swept field. The range information for corresponding arcuate portions or channels of each succeeding revolution or sweep is compared with that previously stored information for such channel and the minimum range information retained for each of the channels. Thus, with each sweep or revolution of the ranging device, new data for each channel is individually compared with the data already residing in each channel. If the new distance measured is less than the distance previously measured and stored for this channel, this new measurement information is then stored and the old information discarded. Simultaneously therewith, lineal distance information as to the location of each minimum range point can be recorded in separate storage area. The process continues for each right-of-way to be measured at which time the operator transfers the stored information to be transferred to paper tape or other storage.

Repetitive signaling using a noisy feedback channel

Abstract: Several feedback coding schemes considered recently are repetitive signaling schemes. The sender retransmits the message, if necessary, on the basis of information received over the feedback channel. This paper considers a repetitive signaling scheme in which the user's estimate of the transmitted message is sent over the feedback channel to the sender with high energy if the user is uncertain of the estimate and with lower energy if otherwise. The sender retransmits the message with high energy if it decides the user's estimate is incorrect. This scheme is applied to a wide-band, additive-white-Gaussian-noise, average-power-constrained feedback communication system. Orthogonal signals are used for transmission over both forward and feedback channels. A lower bound is obtained for the probability of error when arbitrary decision rules are used. This lower bound is achieved asymptotically for long block duration by using decision rules implemented with correlation receivers. The resulting asymptotic error performance is superior to that of any feedback coding scheme previously considered for use in a wide-band additive-white-Gaussian-noise system for any values of the forward and feedback channel capacities.

Universal buffer interface for computer controlled test systems

Abstract: A testing system wherein a digital computer controls programmable testing devices which supply signals to, and receive signals from, a unit under test. Buffer interface equipment is connected to three input/output channels of the computer and includes a plurality of storage registers connected to the various programmable test devices. Information to be supplied to the test devices is received via one input/output channel and placed into storage. Test results are also placed into storage and transmitted back to the computer for analysis via a second channel. The third channel contains address information for selecting which storage registers receive or transmit the digital signals.

Automatic reference level set for television cameras

Abstract: Methods and apparatus for automatically establishing the voltage levels in a television camera which represent signal amplitude levels corresponding to the black and white reference levels by sensing the voltage level of a video signal channel as the image of the scene to be televised is scanned, comparing the sensed signal with a reference signal and establishing a digital signal indicative of whether the voltage of the sensed signal is greater or less than that of the reference, storing the digital information and, if desired, altering the information stored upon command from the comparator, establishing an output voltage signal having a magnitude determined by the stored or altered digital information and modifying the black and white levels from the camera.

Wide dynamic range noise masking compandor

Abstract: A noise masking compandor for greatly reducing the noise added to a wide dynamic range audio signal in passing through a noisy channel, such as a tape recorder. The audio signal, having a dynamic range of approximately 90 db, is compressed to a dynamic range of approximately 30 db for transmission through the noisy channel then subsequently expanded in a complementary fashion to its original 90 db range to provide a faithful reproduction of the original signal without noticeable noise. Compression and expansion result from high precision rectifiers to minimize distortion, and are further achieved without the need for maintaining precisely constant input and output levels for the noisy channel to avoid frequency response distortion. A high degree of high and low frequency signal preemphasis is provided in the compression and expansion characteristic without creating overload problems for the noisy channel.

Worst interference for coherent binary channel (Corresp.)

Abstract: For a coherent channel transmitting binary digits, a worst distribution under an average power constraint can be defined. A solution for the very noisy channel is found to be Gaussian, and the minimax demodulator utilizes correlation detection to guarantee an exponential bound on probability of error.

Optical memory with reference channel to compensate for deterioration

Abstract: A beam addressed optical mass memory utilizes an alterable memory medium which exhibits a change in its optical properties as a function of time or as a function of write-rewrite cycles. A reference bit is recorded on the memory medium and one or more information bits are similarly recorded. The reference and information bits are subjected to essentially the same number of write-rewrite cycles, and therefore exhibit essentially identical changes in optical properties. Information is read out by sequentially directing the light beam to the reference bit and the information bits. A detector produces a reference signal indicative of the intensity of the light beam received from the reference bit and produces information signals indicative of the intensity of the light beam from each of the information bits. The reference signal is directed to a reference channel and temporarily stored. Each of the information signals is directed to an information channel. The reference signal is compared to each of the information signals and readout signals are produced which are indicative of the difference between or the ratio of the reference signal and each of the information signals.

Channels without synchronization

Abstract: Let X = {1,..., a) and Y -= 1,..., a) be the input and output alphabets, respectively. In the (unsynchronized) channels studied in this paper, when an element of X is sent over the channel, the receiver receives either nothing or a sequence of k letters, each a member of Y, where k, determined by chance, can be 1, or 2, or... orL, a given integer. The channel is called unsynchronized because the sequence received (for each letter sent) is not separated from the previous sequence or the following sequence, so that the receiver does not know which letters received correspond to which letter transmitted. In Sections I and 2 we give the necessary definitions and auxiliary results. In Section 3 we extend the results of Dobrushin [2] by proving a strong converse to the coding theoreml and making it possible to compute the capacity to within any desired accuracy. In Section 4 we study the same channel with feedback, prove a coding theorem and strongconverse, and give an algorithm forcomputing the capacity. In Section 5 we study the unsynchronized channel where the transmission of each word is governed by an arbitrary element of a set of channel probability functions. Again we obtain the capacity of the channel, prove a coding theorem and strong converse, and give an algorithm for computing the capacity. In Section 6 we apply results of Shannon [41 and supplement Dobrushin's results on continuous transmission with a fidelity criterion.

Channel tuning arrangement

Abstract: Channel tuning equipment for a communications receiver comprises a channel selector for selecting, in coded form, the channel to which the receiver is to be tuned, circuitry for scan-tuning the channels, a sensor circuit for issuing pulses responsive to successive tunings of the channels, a binary counter responsive to the output of the sensor circuit, and a decoder operable in conjunction with the channel selector and the output of the counter for producing an output of a predetermined logic state only when the selected channel has been reached. The output at the predetermined logic state is utilized to effect a cessation of the scan-tuning either as a signal for manual stop tuning or as a command for automatic stop tuning. The receiver may be an FM receiver that is connected to a coaxial cable for selective tuning to a large number (e.g. several hundred) of channels.