Showing papers on "Communication channel published in 1969"

Quantizing for Noisy Channels

Abstract: We consider the transmission of numerical data over a noisy channel. Two sources of error exist. The first is the quantizer where the input data is mapped into a finite set of rational numbers and the second is the channel which includes the encoder, transmitter, transmission medium, receiver, and decoder. For any given probability density on the input data and any given channel matrix, we determine the quantization values and transition levels which minimize the total mean-square error. We also determine the best quantizer structure under the constraint that quantization values and transition levels be equally spaced. For the special case of a noiseless channel both results reduce to those of Max [2]. As an example we consider the case of Gaussian input data and phase-shift keyed (PSK) transmission in additive white Gaussian noise. The transmitter is both peak and average power limited, and the system operates in real time. Both the natural and Gray codes are considered. The mean-square error, quantizer entropy, channel capacity, and information rate are computed for the system using the optimum uniform quantizer. Finally, we show that it is important to take the channel into consideration when designing the quantizer even when the system is not constrained to operate in real time.

An adaptive receiver for digital signaling through channels with intersymbol interference

Abstract: A tutorial paper on an adaptive receiver that is suitable for high-speed digital signaling over slowly time-varying, band-limited channels which have impulse responses that are unknown at the receiver is presented. The receiver utilizes a steepest-descent technique for adjusting its parameters to existing channel conditions. A treatment of the speed of adaptation of the receiver is included.

Method of making semiconductor devices

Abstract: A method for making an IGFET is described. The method utilizes impurity ion implantation into the surface channel to determine the conductivity thereof. The advantages include special impurity profiles providing improved performance, better control over important parameters such as threshold voltage, the manufacture of improved tetrodes, and the manufacture of improved ICs using for example N- and P-channel devices, and depletion and enhancement devices combined in a single chip.

An experimental distributed switching system to handle bursty computer traffic

Abstract: An experimental switching system has been built using commercially available integrated semiconductors to switch data. Data messages to be handled by the system may vary in bit rate (100 bits/sec - 4 × 106 bits/sec), message length, and rate of message occurrence.The system uses a synchronous transmission facility with a crystal stabilized clock rate of approximately 6 MHz. The signaling format chosen facilitates data interchange between a number of similar small sequential machines that share a common transmission facility. Efficient data transmission over common carrier systems requires a change in signal format at the channel inputs.Systems involving interconnected loops are discussed briefly; however, the traffic handling capacity of such systems must be analyzed to determine the memory requirements at the junction points. This paper is concerned primarily with the detailed organization of a single loop.

Measurement of random time-variant linear channels

Abstract: This paper concerns the problems of the measurability and measurement of random time-variant linear channels. With regard to measurability, a new, less stringent channel measurability criterion is proposed to supersede the BL product introduced by Kailath. This criterion involves the area of occupancy of the Doppler-delay spread function (or its dual). By using time and bandwidth constraints on the input and output of a channel, channel measurement is reduced to the measurement of a discrete set of finite parameters. Optimal measurement techniques are described and their performances determined for both known and unknown channel correlation functions.

Improving communication reliability by use of an intermittent feedback channel

Abstract: This paper describes and analyzes a feedback communication scheme where the feedback channel is used only to inform the transmitter, at specified times (prior to a final decision), which message the receiver considers most likely. The feedback information is used by the transmitter to modify its transmission according to a rule known also to the receiver. When orthogonal signals are used and only an average transmitter power constraint is imposed, the error probability can be made to decrease in an N -fold exponential manner with increasing

Hybrid frequency shift-amplitude modulated tone system

Abstract: A two channel data transmission system using amplitude modulation of the frequency shifted carrier of one channel to transmit the data of the second channel. Both channels operate at the maximum data rate at which either a single AM or FS channel would operate over the same band width.

Quadrasonic sound system

Abstract: A stereophonic sound system is disclosed utilizing a two-channel transmission path yet capable of locating virtual sound sources at any point on a circle around a listener. The two-channel transmission path may consist of conventional stereophonic channels such as records, tapes, broadcasting channels, etc. The recording or transmitting means (as the case may be) of the invention provides two audio signals which may comprise preselected combinations of four (for example) directional inputs. One channel may include the first input plus a signal proportional to the sum of the second and fourth inputs, while the second channel consists of the third input plus a signal proportional to the difference between the second and fourth inputs. The sound reproducing means couples these signals and various combinations thereof to four (for example) loudspeakers which may be arranged on the circumference of a circle around the listener. The first speaker may be responsive to the signal on one channel, the next adjacent speaker is responsive to the sum of the signals on the two channels, the third successive speaker is responsive to the second channel, and the last speaker is responsive to the difference between the signals on the two channels. Means are disclosed for controlling the gain in the signal paths of the voltages coupled to the various speakers relative to the other speakers to increase the audio separation between adjacent speakers and thus enhance the directional effect.

A Troposcatter Channel Model

Abstract: Using some basic results in propagation theory, a single integral is derived which relates the channel delay power spectrum to the geometry and antenna patterns of the troposcatter link. Theoretical curves of delay power spectra and frequency correlation functions are presented for medium- and long-distance troposeatter links.

Determination of lightning temperature

Abstract: The assumptions on return-stroke channel opacity, temperature profile, and energy-state distribution that have been used in lightning temperature calculations are examined. It is shown that the assumptions used are probably valid, except perhaps during the initial few microseconds of the discharge, and that a reasonable approximation to local thermodynamic equilibrium exists within the return-stroke channel.

Radio telecommunication system with automatic replacement of defective channels

Abstract: A telecommunication system with several parallel radio channels, operating on different frequency bands, is associated with two standby channels which can be selectively allocated to any working channel by a logic matrix responsive to partial or complete fading of signal in such working channel. Associated discriminating networks establish priorities for the selection of one standby channel over another and for having wholly defective working channels take precedence over channels with only moderately impaired transmission. A single working channel of the group may be selectively marked by a pre-emptive signal enabling this channel to take over, in the event of transmission failure, a standby channel already allocated to a nonprivileged working channel.

Solitary waves in trapezoidal channels

Abstract: Experimental measurements were made of the variation of water-surface height across the crests of solitary waves travelling along trapezoidal channels. The channels had one vertical side and the other side sloped at either 30°, 45° or 60° to the vertical. Reliable results were not obtained with the last channel, but for the other channels there was reasonable agreement with recent theoretical results.

Side hole terminal

Abstract: An electrical terminal designed to be attached to an electrical conductor in the form of a conventional insulated wire or the like, by means of a solder connection. The body portion of the terminal comprises a channel extending into its interior and at least one hole or aperture formed in the side of the body portion intermediate the extremities of the channel and communicating with the interior of the channel. Solder applied to the interior of said channel through the side hole flows about the connector within the channel due to capillary action. Proper filling of the channel with a required minimum amount of solder may be evidenced by the provision of a second hole also formed in the side of the body portion a spaced distance from the first hole and communicating with the interior of the channel such that the presence of solder in the channel may be observed.

Building panel and side joints therefor

Abstract: A BUILDING PANEL HAVING A CENTRAL PAN OF DESIRED PROFILE AND IMPROVED MARGINAL CONNECTING MEANS ALONG OPPOSITE PAN EDGES, PROVIDING AN IMPROVED SIDE JOINT BETWEEN ADJACENT ONES OF THE BUILDING PANELS. BOTH MARGINAL CONNECTING MEANS COMPRISE UPSTANDING U-SHAPED CHANNELS. ONE CHANNEL IS ADAPTED TO FIT WITHIN THE OTHER CHANNEL TO PROVIDE A GASKET-FREE, ESSENTIALLY WEATHER-TIGHT JOINT HAVING AN INTERLOCK TO PREVENT DISENGAGEMENT.

Self-ejecting keyholder with illumination

Abstract: A KEYHOLDER COMPRISING A CASE WITH A CHANNEL FORMED THEREIN FO RECEPTION OF A KEY. THE KEY IS SLIDABLY MOUNTED WITHIN THE CHANNEL AND SPRING MEANS ARE PROVIDED FOR AUTOMATICALLY EJECTING A KEY FROM A LOCK. THE CASING IS FORMED FROM A TRANSPARENT PLASTIC, AND LIGHT MEANS ARE POSITIONED WITHIN THE CASING. WHEN THE LIGHT MEANS ARE TURNED ON, TH ELIGHT PRODUCED WILL BE DIFFUSED THROUGH THE TRANSPARENT PLASTIC, THEREBY ILLUMINATING THE KEY AND THE ASSOCIATED LOCK, AND THUS FACILITATING THE INSERTION OF THE KEY IN THE LOCK.

Tablet dispenser with circular tablet channel

Abstract: A CALENDARED TABLET DISPENSER IS PROVIDED IN WHICH THE TABLETS ARE CONTAINED IN A CONTINUOUS CIRCULAR TABLET CHANNEL. BY VIRTUE OF A DOWNWARD EXTENDING PROJECTION SECURED TO THE COVER, ROTATION OF THE COVER WITH RESPECT TO THE BASE IN THE COUNTER-CLOCKWISE DIRECTION CAUSES THE TABLETS TO MOVE IN THAT DIRECTION IN THE TABLET CHANNEL. MEANS ARE PROVIDED TO PREVENT MOVEMENT OF THE TABLETS IN THE CHANNEL IN THE COUNTER-CLOCKWISE DIRECTIONS. IN USE, THE COVER IS ROTATED WITH RESPECT TO THE BASE IN THE COUNTERCLOCKWISE DIRECTION TO ALIGN THE INDICIA OF TIME REPRESENTING THE DAY ON WHICH THE FIRST TABLET IS TO BE TAKEN WITH THE TABLET ACCESS APERTURE. IN DISPENSING OF THE TABLET, THE COVER IS ROTATED IN THE CLOCKWISE DIRECTION.

Binary communication over the Gaussian channel using feedback with a peak energy constraint

Abstract: We consider binary communication over the additive white Gaussian noise channel with no bandwidth constraint on the channel input signals, assuming the availability of a noiseless delayless feedback link. Although the signals at time t can depend on the noise at times \tau and are therefore random functions, we require that the signal energy never exceed a fixed level. We show that the optimal probability of error is attainable without the use of the feedback channel by using antipodal signals.

Method of making insulated gate field effect transistor with controlled threshold voltage

Abstract: The threshold voltage of an IGFET is precisely controlled by the introduction of a quantity of dopants into the gate and channel region by exposure to an energetic ion beam.

Telecommunication exchange with time division multiplex

Abstract: A telecommunication exchange with time-division multiplex for conducting information received on a channel of a timemultiplexed communications trunk to a selected channel of a second time-multiplexed communications trunk The information from all channels is sequentially stored in a cyclic storage register in fixed relationships with cyclic code numbers generated by a local clock generator At a clock instant determined by the address of an output channel the address of an input channel is serially introduced into a second cyclic register The output of the second cyclic register is decoded and used to switch the output of the first cyclic register corresponding to the selected input channel to an output line

Terrestrial interface unit

Abstract: In a demand assigned multiple access system, a chosen satellite RF frequency band is divided on the basis of assigning a single voice channel per RF carrier. The RF band, thus divided, forms a ''''pool'''' of frequencies. The demand assigned multiple access system is fully variable, allowing all circuits to be selected by any station on demand. Thus, neither end of a channel is permanently associated with any terminal point, and the channels are paired to form a connection as required within the demand assignment pool. The system does not require a central station for system control, but instead uses a demand assignment signaling and switching unit for self-assignment of channels based on continually updated channel allocation status data provided via a common signaling channel. The common signaling channel is used to continuously apprise each earth station demand assignment signaling and switching unit of the availability of pool channels and to establish links directly with other stations. The demand assigned multiple access terminal is designed to be operated with all types of international telephone exchanges. Because of the variations in workings of the several different types of telephone exchanges, two basic types of telephone central to demand assignment multiple access terminal interfaces are provided. The first type of interface provides for individual channel signaling. This entails the communication of all signaling with the individual access circuits. The second type of interface provides for common channel signaling. This entails the communication of all signaling between the telephone central and the demand assignment multiple access terminal via a separate signaling channel. In all cases, the combined operation of the terrestrial interface unit and the demand assignment signaling and switching unit is such that the signaling between the telephone central and the demand assigned multiple access terminal is the same as if it were between two telephone centrals.

High-density permanent data storage and retrieval system

Abstract: A digital data processing system for transferring digital data from a data channel of the central processor of a computing system or from a temporary storage medium to a high-density laser data recording medium and for nondestructively reproducing the data stored in the high-density medium in a form suitable for transfer to a computer data channel or temporary storage for subsequent use. Input data is transferred into a buffer and control subsystem. This subsystem generates synchronous clock signals and data verification signals which are interleaved with the input data and the composite signal thus produced is recorded on the high-density storage medium. Each recorded bit is checked to insure accuracy of recording at the instant of recording that bit, and remedial action is automatically initiated in the event of error. This remedial action consists of recording a completely unambiguous error indication signal, and re-recording the affected data in such a manner that the final record provides sufficient information to permit correction of all recording errors. During readout the retrieved data is transferred from the high-density storage medium into the buffer and control subsystem for verification of the data. If the data is correct, the synchronous clock and data verification signals are stripped from the output data, the data is reorganized into its original format, and transferred to a computer data channel or other storage medium for subsequent use. If during readout an error is detected, remedial action is automatically initiated before the data is transferred. The buffer and control subsystem includes self-checking diagnostic circuits for detecting and localizing malfunctions in all portions of the high-density data storage and data conversion system.

An Adaptive Equalizer for Television Channels

Abstract: The time-varying nature of long cable systems precludes their use for the transmission of television signals which require a fine degree of equalization. A system has been built, where the TV channel quality is continuously monitored and the required equalization is automatically performed during signal transmission. The principles and operation of this system are explained, and some actual experimental results are discussed.

Effects of multipath transmission on the measured propagation delay of an FM signal

Abstract: Position location techniques based on propagation delay have been proposed previously. A narrow-band version of this technique involves the transmission of RF carrier, modulated by a single audio frequency. At a receiver, the audio phase is a measure of distance provided the propagation delay is less than one quarter cycle. The transmission medium introduces multipath distortion and the received signal consists of a set of signals, each an attenuated and delayed replica of the transmitted signal, having traversed a different path. When FM is employed, the phase of the demodulated composite is a nonlinear function of the parameters of the multipath structure of the channel. In this paper, this functional relationship is derived.

Communications system with frequency and time division techniques

Abstract: A communication system for a substantial number of subscribers is shown having random access capabilities without the requirement for the usual central exchange. The system uses a frequency division scheme for separating the several communication information channels. The individual subscriber units are interconnected as by means of one or more wires which are also connected to a master clock which continually generates time division digital information consisting of a plurality of pulses and unused time spaces (ones and zeros) including binary circuit code information and synchronizing pulses. A relatively limited band width is required for carrying this control information which is substantially displaced in frequency from the band containing the several communication information channels. These channels are generated by means of a frequency synthesizer in each of the subscriber units, each of which continually monitors the digital control information to determine whether its address is being called and the circuit code representing the channel of the incoming call. Similarly, outgoing calls are initiated by picking up a headset at the subscriber unit which causes an unused channel to be selected, inserting its circuit code into the digital stream and causing the frequency synthesizer in responding to this code to generate the corresponding carrier frequency. The audio information is then converted to single side band (or other) modulation of the particular carrier frequency signal.

Magnetic domain storage organization

Abstract: A single wall domain propagation arrangement herein includes magnetically soft overlay patterns which generate magnetic poles in response to reorienting inplane fields to move domains in propagation channels defined thereby. The arrangement is organized for high packing density and fast access by providing parallel recirculating bit channels to move consecutive binary word representations to a common recirculating channel. The common channel moves the word to a common read-write area. Information moves synchronously in the common channel, as well as in the parallel channels, permitting the return of information to the parallel channels with little logic circuitry.

Multipath compensation system

Abstract: A system for compensating for multipath distortion in a synthetic phase isolator predetection combiner. Since echos in the signal can be detected with respect to both magnitude and sense, this information can be used to suppress echos or to control time delay compensation elements to thereby provide a more coherent output signal. Multipath distorted signals are received at a plurality of channels, each of which channels effectively shifts the input signal phase by predetection combination with the sum of the signal outputs of the other channels such that each channel output is substantially independent of the input signal phase.

Simultaneous delay measurement between selected signal frequency channels and reference frequency channel

Abstract: The present invention relates to means for simultaneously measuring differential envelope delay between selected signal frequency channels and a reference frequency channel during transmission through a communications link. A test signal is applied to a bank of band-pass filters which separate the test signal into a reference frequency channel and a plurality of signal frequency channels. The signals of each channel are demodulated and passed to a phase shifting means which is adjustable to establish zero differential delay between the respective signal channel and the reference channel. Thereafter, the test signal is transmitted through the communications link and the output of the communications link is applied to the filter bank. A plurality of delay detecting means each measure differential delay between a respective signal channel and the reference channel and provide a delay signal to suitable indicating means.