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Showing papers on "Communication channel published in 1986"


Patent
05 May 1986
TL;DR: In this paper, a high speed modem that transmits and receives digital data on an ensemble of carrier frequencies spanning the usable band of a dial-up telephone line is described, which includes a system for variably allocating data and power among the carriers to compensate for equivalent noise and to maximize the data rate.
Abstract: A high-speed modem that transmits and receives digital data on an ensemble of carrier frequencies spanning the usable band of a dial-up telephone line. The modem includes a system for variably allocating data and power among the carriers to compensate for equivalent noise and to maximize the data rate. Additionally, systems for eliminating the need for an equalization network, for adaptively allocating control of a channel, and for tracking variations in line parameters are disclosed.

807 citations


Patent
27 Nov 1986
TL;DR: A switched integrated wideband and narrowband multiservices digital network (FIGS) as discussed by the authors is an ISDM providing universal information services based on wideband/narrowband voice, data, and video communications.
Abstract: A switched integrated wideband and narrowband multiservices digital network (FIGS. 1 and 2) is an ISDM providing universal information services based on wideband and narrowband voice, data, and video communications. It comprises a plurality of service areas (100, 101), each served by a central switching node (110). The central node is connected to a plurality of remote nodes (103) by feeder optical fibers (107) and a control bus extension (106). Network interface equipment (104) at subscribers' (102) premises is connected to remote nodes by distribution optical fibers (105). Each distribution fiber is wavelength-division multiplexed and carries modulated (pulse-analog, pulse-code, or differential pulse-code) wideband digital channels (205) and a multiplexed channel (206) comprising 32 time-division-multiplexed narrowband digital channels (207). One narrowband channel (207D) carries all signaling messages. Feeder fibers are wavelength-division multiplexed and carry modulated wideband digital channels (305), and multiplexed channels (306) each comprising a plurality of time-division-multiplexed distribution multiplexed channels. Each remote node comprises a digital space-division switch (505) for wideband channels, and a digital time-division multiplexer and demultiplexer (506) for multiplexed channels. Each central node comprises a digital space-division switch (606) for wideband channels, and a digital time-division switch (607) for narrowband channels. All switches are controlled by a central node control complex (612) over a control bus (116) and its extensions. Signaling messages are transferred between the signaling-message-carrying narrowband channels and the central node complex by a subscriber signaling subsystem (613) via the narrowband switch and the control bus. A central node optionally includes interfaces (615-618) to other communication systems, and trunk communication fiber (112) and CCIS signaling fiber (117) connections to other central nodes of the network.

302 citations


Patent
30 Dec 1986
TL;DR: In this paper, a multiple access data communication system is disclosed wherein a communication channel is shared by a plurality of stations, and the channel is divided into frames each being partitioned into time slots smaller in number than the number of stations of the system.
Abstract: A multiple access data communication system is disclosed wherein a communication channel is shared by a plurality of stations. The channel is divided into frames each being partitioned into time slots smaller in number than the number of stations of the system. A reservation status signal is constantly broadcast at frame intervals from a central station to all remote stations to indicate reserved status of the time slots. When a transmission request is made in a remote station, it discriminates a message signal shorter than the time slot length as a single packet having a time slot length and detects an idle time slot from the channel using the reservation status signal. If the message signal is longer than the time slot length, the station divides it into a series of packets of the time slot length and transmits a reservation request to the central station to receive from it a time-slot assignment signal and inserts the long-message packets to time slots specified by the time-slot assignment signal.

255 citations


Journal ArticleDOI
TL;DR: In this article, the authors discuss the importance of small streams for a wide range of resource benefits, such as spawning habitat, stream power, and energy dissipation, where channel morphology is modified or structural features such as woody root systems, logs, boulders or bedrock.
Abstract: Throughout the United States, land managers are becoming increasingly aware of the importance of small streams for a wide range of resource benefits. Where channel morphology is modified or structural features are added, stream dynamics and energy dissipation need to be considered. Unit stream power, defined here as the time-rate loss of potential energy per unit mass of water, can be reduced by adding stream obstructions, increasing channel sinuosity, or increasing flow resistance with large roughness elements such as woody root systems, logs, boulders, or bedrock. Notable morphological features of small streams are pools, riffles, bed material, and channel banks. Pools, which vary in size, shape, and causative factors, are important rearing habitat for fish. Riffles represent storage locations for bed material and are generally utilized for spawning. The particle sizes and distributions of bed material influence channel characteristics, bedload transport, food supplies for fish, spawning conditions, cover, and rearing habitat. Riparian vegetation helps stabilize channel banks and contributes in various ways to fish productivity. Understanding each stream feature individually and in relation to all others is essential for proper stream management. Although engineered structures for modifying habitat may alter stream characteristics, channel morphology must ultimately be matched to the hydraulic, geologic, and (especially) vegetative constraints of a particular location.

246 citations


Patent
05 Mar 1986
TL;DR: In this paper, the authors present an apparatus and method for the simultaneous transmission of analog speech and modulated data, which is optimized for use over impaired and bandwidth restricted analog channels, or digital representations of such channels.
Abstract: The present invention relates to an apparatus and method for the simultaneous transmission of analog speech and modulated data, such apparatus and method being optimized for use over impaired and bandwidth restricted analog channels, or digital representations of such channels. In each instance of use, an evaluation is made of the available channel bandwidth, with a frequency division multiplex scheme allocating a voice sub-band, with data transmission allocated to sub-bands above, below, or around, this selected voice sub-band. The speech and data sub-band allocations are made by the multiplexor in response to user input of either a requested speech quality, a requested data rate, or a value indicating the relative user weighting of speech quality and data rate. A multi-carrier multi-mode modulation scheme is employed for data transmission, with this scheme having the ability to fully utilize the remaining bandwidth, and further, being capable of adapting to the impairments most likely present on the fringes of bandwidth restricted analog channels. When the analog channel employed is the standard voice-grade telephone circuit, good speech quality simultaneously with 3000 bps data transmission may be expected. The further ability to automatically switch to full bandwidth data transmission when voice transmission is not being attempted is also provided.

242 citations


Journal ArticleDOI
TL;DR: The authors investigate the use of a moderately high externally set profitability constraint as a goal-setting mechanism for controlling channel negotiators to reveal the impact of the constraint and power variables on both quantity and quality of transactions completed as well as dynamics of negotiations over time.
Abstract: The authors investigate the use of a moderately high externally set profitability constraint as a goal-setting mechanism for controlling channel negotiators. Equal and high power channel members ar...

176 citations


Journal ArticleDOI
01 Jan 1986
TL;DR: It is argued that the energy profile in the permeation pathway of most biological channels should vary relatively smoothly with only a few localized energy barriers or wells.
Abstract: Although the reaction-rate theory may provide a useful mathematical description of the channel flux, it presents a misleading physical picture of the channel structure. There is a tendency to regard the barriers in the model as actual physical structures, whereas they are actually only mathematical artifacts that allow one to reduce a complicated differential equation with an infinite number of states to a finite difference equation with a minimum number of states. I argue that the energy profile in the permeation pathway of most biological channels should vary relatively smoothly with only a few localized energy barriers or wells. In these smoothly varying regions, the resistance to ion movement is similar to bulk diffusion and cannot be accurately modeled by one or two energy barriers. For the one-ion channel, the continuum approach is as general and at least as simple as the reaction-rate theory and may provide a more physical interpretation of the data. Thus for the SR K+ channel, the structure suggested by the reaction-rate theory seems inconsistent with some experimental data, while the continuum-theory model is not only consistent with, but complements, the structure suggested by other data. Multi-ion channels have such complicated kinetics that one can only expect the theories to provide a qualitative description of the experimental data. They can be modeled by either the reaction-rate model or a finite difference approximation to the continuum model.

170 citations


Patent
26 Mar 1986
TL;DR: In this article, a combination of a transmitter and implantable receiver is disclosed wherein data is conveyed from transmitter to receiver utilizing a data format in which each channel to be stimulated is adapted to convey information in monopolar, bipolar or analog form.
Abstract: A combination of a transmitter and implantable receiver are disclosed wherein data is conveyed from transmitter to receiver utilizing a data format in which each channel to be stimulated is adapted to convey information in monopolar, bipolar or analog form. The data format includes two types of code words: transition words in which one bit is assigned to each channel and can be used to create monopolar pulsatile or bipolar pulsatile waveforms; and amplitude words that can create analog waveforms one channel at a time. An essential element of the output system is a current source digital to analog converter which responds to the code words to form the appropriate output on each channel. Each output is composed of a set of eight current sources, four with one polarity of current and the other four with the opposite polarity of current. In each group of four, the current sources are binarily related, I, 21, 41 and 8I. In this arrangement each channel can supply 16 amplitudes times two polarities of current; meaning 32 current levels. This channel is simply a 5-bit digit to analog converter. The output circuitry contains charge balance switches. These switches are designed to recover residual charge when the current sources are off. They are also designed to current limit during charge recovery if the excess charge is too great so that they do not cause neural damage. each channel charge balances (will not pass DC current or charge) and charge limits to prevent electrode damage and bone growth. The charge balancing is performed by the charge balancing switches and by the blocking capacitor. The charge limiting is performed by the blocking capacitor only. The charge level on each channel is defined using a switch network ladder which combines a plurality of parallel connected switches; clcosure of each switch doubles the current level handed off from the previous switch.

159 citations


Journal ArticleDOI
TL;DR: This work is primarily rephrasing the work in channel capacity in terms of C_{J} bit/J as compared to C bit/s, to emphasize the energy efficiency and to deemphasize the speed of the telemetry.
Abstract: Underwater acoustic telemetry has a total input energy constraint, since the energy is stored in the transmitter's batteries. This work is primarily rephrasing the work in channel capacity in terms of C_{J} bit/J as compared to C bit/s, to emphasize the energy efficiency and to deemphasize the speed of the telemetry. The energy channel capacity C_{J} , for any waveform channel with well-defined capacity C bit/s at signal power S watts, is defined as C/S bit/J. It is shown that for coherent binary frequency shift keying (BFSK) and waveform channels, the supremum of C_{J} over S is approached as S approaches zero. For the Gaussian channel the best coding uses narrow bands with the highest S/N.

154 citations


Journal ArticleDOI
James L. Best1

149 citations


Patent
11 Dec 1986
TL;DR: In this article, the transmission power of a transmitting station over a digital radio communication channel, based on information relating to the level of the signal received at a receiving station and information related to the quality of such received signal relative to a predetermined error rate, is controlled.
Abstract: Apparatus for controlling the transmission power of a transmitting station over a digital radio communication channel, based on information relating to the level of the signal received at a receiving station and information relating to the quality of such received signal relative to a predetermined error rate. The signal level information and signal quality information is derived by respective threshold measurement devices in the receiving station, and is transmitted back to the transmitting station over a return channel. The transmitting station comprises means for effecting combined processing of such information to derive a control signal which controls means for increasing or decreasing the transmitting power over a dynamic adjustment range. In a first part of such dynamic range such control is based only on the information relating to received signal level, and over a second part of such range such control is additionally based on the quality of the received signal.

Patent
03 Feb 1986
TL;DR: In this article, a distributed, demand access local loop telephone system is described, where a central office and a plurality of remote units which are located near subscriber populations are connected to the subscriber equipment (e.g., telephones or other data sources/sinks) by subscriber dedicated links.
Abstract: A distributed, demand access local loop telephone system is disclosed. An optical fiber, or fibers, connect a central office and a plurality of remote units which are located near subscriber populations. Communications on the fiber is by high speed digital data stream which is comprised of a plurality of bit multiplexed PCM channels, each of bandwidth equivalent to a VF channel or greater. The remote units are connected to the subscriber equipment (e.g. telephones or other data sources/sinks) by subscriber dedicated links (e.g. wire pairs or other cabling), and the remote units may be added, subtracted, or moved along the fiber path to reconfigure the overall system. Because of the demand access nature, the fiber bandwidth can be dynamically redistributed among the remote access units at high speed and controlled at the central office. The topology of the system can also be reconfigured, within limits, from a central site. The system is T1 compatible, the data stream being the resultant of a plurality of T1 streams, and means is provided at the remote units for extracting and inserting one or more VF equivalent channels in any desired number up to and including an entire T 1 equivalent group.

Journal ArticleDOI
TL;DR: In this paper, three approaches to rehabilitation of the degraded channels are possible; geomorphic, engineering and rational, which are based on the channel evolution model, and it generally involves control of grade, control of discharge, or a combination of both.
Abstract: Incised channels are those in which an imbalance between sediment transport capacity and sediment supply has led to degradation of their beds. This is a frequent response to stream channelization, changes in land use, or lowering of base level. If the degradation causes a critical bank-height threshold to be exceeded, which is dependent on the geotechnical properties of the bank materials, then bank failure and channel widening follow. Interdependent adjustments of channel slope and cross-sectional area occur until a new state of dynamic equilibrium with the imposed discharge and sediment load is attained. These geomorphic adjustments can be described and quantified by using location-for-time substitution and a model of channel evolution can be formulated. Three approaches to rehabilitation of the degraded channels are possible; geomorphic, engineering and rational. The rational approach, which integrates elements of both the engineering and geomorphic approaches, is based on the channel evolution model, and it generally involves control of grade, control of discharge, or a combination of both.

Patent
Alfons Eizenhoefer1
30 Jul 1986
TL;DR: In this paper, a time division multiplexed signal frame is generated, including a plurality of time slots which repeat each frame interval, and the signalling channels include a common organizational connection for each channel of the frame.
Abstract: Method of digital radio transmission between a base station and a plurality of mobile stations. A time division multiplexed signal frame is generated, including a plurality of time slots which repeat each frame interval. A beginning number of the time slots form a signalling channel with the remaining following time slots forming a plurality of channels which receive data to be sent. The signalling channels include a common organizational connection for each channel of the frame. Additionally, one of the remaining plurality of channels includes an organizational channel for identifying a larger number of channels than those included in the individual frame. The technique permits a combination of time division multiplexing, spectral multiplexing and carrier frequency multiplexing.

Patent
22 May 1986
TL;DR: In this article, a buffer memory is used to store data from the input/output device arrayed corresponding to the data rate of the data device and a threshold is selected for beginnig an unload cycle of the buffer memory which will permit said buffer memory contents to be completely transferred at the higher channel data rate to the channel during the remaining time additional data is being accumulated in the memory.
Abstract: A buffer memory is used to store data from the input/output device arrayed corresponding to the data rate of said input/output data device. A threshold is selected for beginnig an unload cycle of the buffer memory which will permit said buffer memory contents to be completely transferred at the higher channel data rate to the channel during the remaining time additional data is being accumulated in the memory. The threshold selection is adaptive such that subsequent data block lengths are utilized to calculate a new threshold maintaining data transfer rates from the input/output device into the channel at an optimum value.

Patent
07 Aug 1986
TL;DR: In this article, a system for data communication between ground stations using an orbiting satellite as a relay includes a technique for avoiding the loss of signals from the satellite during periods of heavy precipitation.
Abstract: A system for data communication between ground stations using an orbiting satellite as a relay includes a technique for avoiding the loss of signals from the satellite during periods of heavy precipitation. Data is communicated from an orbiting satellite to a plurality of earth stations on a single transmission frequency. The data is communicated on two separate transmission channels on that one frequency by using orthogonal channels of a coherent phase quadrature transmission system. The overall data rate on one of the two transmission channels is much lower than the overall data rate on the other of the two channels. The data on the lower data rate channel is less likely to be affected by heavy precipitation occurring in the line of sight between the satellite and the ground station, and the lower data rate channel is thus used to communicate data to a ground station located in an area of heavy precipitation. The lower data rate channel is further used to maintain phase synchronization so that the probability of losing phase synchronization with the signal transmitted by the satellite is significantly reduced.

Patent
17 Dec 1986
TL;DR: In this paper, the authors propose a true tester-per-pin architecture, where each channel of the tester operates as if it were an independent tester, and each channel has a memory circuit which stores instructions for operating that channel.
Abstract: A multichannel automatic test system for an electronic circuit utilizes a "true tester-per-pin" architecture; each channel of the tester operates as if it were an independent tester. Each channel of the tester has a memory circuit which stores instructions for operating that channel of the tester. Each of these memories is cycled to the next address to provide a new instruction for that channel, only when it is necessary to change the state of operation of that channel. Thus, the timing of the events on one channel are independent of the timing on the events of any other channel in the tester. The architecture permits the use of dynamic random access memory (DRAM) circuits and allows for backward looping in the test sequence through the use of a cache memory circuit in each channel. The instructions for operating each channel of the tester are context-dependent; that is, the present state of operation of that channel of the tester is utilized in interpreting the next instruction for that channel.

Patent
Christopher B. Marshall1
04 Jul 1986
TL;DR: In this paper, a signal transmission system which is particularly suitable for the employment of direct conversion receivers has a block of adjacent transmission frequency bands allocated to it, where each signal channel is split into two sub-channels or parts occupying mutually different frequency bands for transmission and the bands occupied by the subchannels of the various channels are interleaved.
Abstract: A signal transmission system which is particularly suitable for the employment of direct conversion receivers has a block of adjacent transmission frequency bands allocated to it. Each signal channel is split into two sub-channels or parts occupying mutually different frequency bands for transmission and the bands occupied by the sub-channels of the various channels are interleaved. In the receiver the local oscillator is tuned midway between the bands corresponding to the sub-channels of the wanted channel and the corresponding signals are recovered by bandpass filtering, phase-shifting, summing and differencing, demodulating and combining the frequency down-converted outputs of quadrature related mixers to which the received and the local oscillator signals are applied. Although d.c. block capacitors are used in the outputs of the mixers, these can have a low value because the notch formed in the transmission frequency characteristic does not affect the reception of the required signals, so that the receiver can settle rapidly at switch-on.

Patent
26 Feb 1986
TL;DR: In this paper, a matrix means responsive to the two or more channel signals and the two control signals for generating a number of output signals according to an algorithm is used to steer the directional information systems in such manner through the matrix means that the directional effects of the output signals are enhanced.
Abstract: The decoder of this invention decodes at least two channel signals in a directional information system where at least four input signals containing directional information have been encoded into the two or more channel signals. The decoder generates a first control signal substantially proportional to the logarithm of the ratio of the amplitudes of two of the channel signals to detect, as between two of the channel signals, whether the amplitude of one signal dominates that of the other. The decoder also generates a second control signal substantially proportional to the logarithm of the ratio of the amplitudes of the sum and the difference between two of the channel signals to detect the dominant signal in terms of amplitude. The decoder includes a matrix means responsive to the two or more channel signals and the two control signals for generating a number of output signals according to an algorithm. The control signals generated are used to steer the directional information systems in such manner through the matrix means that the directional effects of the output signals are enhanced. Two decoders of the type described above may be used to decode the high frequency and low frequency portions of the channel signals where the high and low frequency portions are separated by means of two crossover filters. The crossover frequency of the two crossover filters is controlled so that it is approximately at the top end of the signal frequencies intended for the center loudspeaker. Very low frequency signal components are separately processed and evenly distributed among the left, center and right channels.

Patent
28 Feb 1986
TL;DR: In this article, an audio bridge for a telephone conference is described, which comprises an echo canceer to cancel an echo signal from the transmitting side fed back to the receiving side, an amplifier and attenuator circuits to adjust levels of an output of the echo canceller and a transmitting signal transmitted through the channel signal processing circuit.
Abstract: An audio bridge for a telephone conference is disclosed. The audio bridge; comprises a channel signal processing unit assigned to at least three channels. Each channel signal processing circuit comprises an echo canceller to cancel an echo signal from the transmitting side fed back to the receiving side, an amplifier and attenuator circuits to adjust levels of an output of the echo canceller and a transmitting signal transmitted through the channel signal processing circuit, an ERL determining circuit to determine an echo cancellation on the basis of the output from the echo canceller and a signal level on the transmitting side, and a gain/loss computing circuit to compute a loss in a predominant voice condition and a gain and a loss in an inferior voice condition. The speech audio bridge further comprises audio bridge circuits which add the outputs of the amplifier circuits provided in the channel signal processing circuits except for the one assigned to itself, and a predominant channel detection unit for detecting a predominant channel and inferior channels on the basis of output levels of the amplifier circuits to suitably control the gain and loss of each channel according to the predominant and inferior voice conditions. Thus, this equipment makes it possible to prevent "singing" due to the variation of the cancellation with time.

Journal ArticleDOI
TL;DR: An interesting feature of the analysis is that magnitude codes that are catastrophic may perform better than those that are noncatastrophic.
Abstract: Calderbank, Heegard, and Ozarow [1] have suggested a method of designing codes for channels with intersymbol interference, such as the magnetic recording channel. These codes are designed to exploit intersymbol interference. The standard method is to minimize intersymbol interference by constraining the input to the channel using run-length limited sequences. Calderbank, Heegard, and Ozarow considered an idealized model of an intersymbol interference channel that leads to the problem of designing codes for a partial response channel with transfer function (1 - D^{N}) /2 , where the channel inputs are constrained to be \pm 1 . This problem is considered here. Channel inputs are generated using a nontrivial coset of a binary convolutional code. The coset is chosen to limit the zero-run length of the output of the channel and so maintain clock synchronization. The minimum squared Euclidean distance between outputs corresponding to distinct inputs is bounded below by the free distance of a second convolutional code which we call the magnitude code. An interesting feature of the analysis is that magnitude codes that are catastrophic may perform better than those that are noncatastrophic.

Patent
21 Apr 1986
TL;DR: In this paper, the transmission priority of a selected channel is raised if the selected channel was not used at another station, and lowered if the chosen channel was used at other station.
Abstract: In order to effectively avoid cochannel interferences in a multi-station communications system utilizing a plurality of channels in common, the order of transmission channels to be used is determined utilizing a transmission priority assigned to each channel. The subject matter is characterized in that (a) the transmission priority of a selected channel is raised if the selected channel is not used at another station, and (b) is lowered if the selected channel is used at another station. This means that the past use records of the transmission channels are accumulated so that a good channel can be selected with high probability. In other words, a transmission channel with high priority is still ready to be used even if it was not selected in the preceding selection.

Patent
Hideaki Morimoto1
10 Dec 1986
TL;DR: In this paper, a channel switching system for monitoring the standby channels is provided at the receiving side of the digital communication system with: control signal generator means operating so that when two or more standby channels are in standby condition, it generates a control signal to designate them in turn.
Abstract: In a digital radio communication system using at least two regular channel and two or more standby channels for transmitting a test signal therethrough in the standby condition thereby permitting the regular channel to be synchronously switched to one of the standby channels, the improvement wherein a channel switching system for monitoring the standby channels is provided at the receiving side of the digital communication system with: control signal generator means operating so that when two or more standby channels are in standby condition, it generates a control signal to designate them in turn, and when only one standby channel is in standby condition, it generates a control signal to designate the channel; synchronizing switching means for selectively outputting the test signal transmitted via each of the standby channels designated by the control signal; and standby channel monitoring means for detecting an output from the synchronizing switching means to monitor the communication quality of the standby channel placed in standby condition on the basis of the result detected.

Patent
29 Sep 1986
TL;DR: In this article, an access control module restricts access to a computer system to authorized users and selectively controls each user's access to associated computer peripherals such as data storage units, printers, and communications equipment.
Abstract: An access control module restricts access to a computer system to authorized users and selectively controls each user's access to associated computer peripherals such as data storage units, printers, and communications equipment. During start-up of the computer system, a microprocessor associated with the module invokes a software routine that requests entry of a valid user identification code. In response to the code, the microprocessor retrieves from a main non-volatile storage unit pre-recorded information regarding the user's authority to access each of the peripherals, and loads the information into a secondary storage unit comprising random access memory and an address decoder adapted to retrieve data therefrom. Thereafter, the address decoder responds to each peripheral address signal generated in the input/output channel associated with the computer system and retrieves from the secondary storage unit the access information relating to the peripheral identified by the address signal. A latching circuit generates and maintains a signal indicating a violation of computer security if the retrieved information indicates that the current user of the computer system is not authorized to access the selected peripheral. The microprocessor responds to the signal indicating security violation by applying signals to the input/output channel which interrupt the operation of the computer system and interfere with access to the selected peripheral.

Patent
05 May 1986
TL;DR: An endoscope device wherein an observing optical system, illuminating optical system and channel are incorporated into independent pipes which are then arranged as exposed out to form an endoscope inserting part and the above mentioned channel is formed to be of a noncircular cross-section so that, when a treating tool is inserted through the channel, a larger hollow gap may be made between the inner wall of the channel and the treating tool.
Abstract: An endoscope device wherein an observing optical system, illuminating optical system and channel are incorporated into respectively independent pipes which are then arranged as exposed out to form an endoscope inserting part and the above mentioned channel is formed to be of a noncircular cross-section so that, when a treating tool is inserted through the channel, a larger hollow gap may be made between the inner wall of the channel and the treating tool.

Patent
Garry C. Hess1
28 Nov 1986
TL;DR: In this paper, an improved two-way radio communication system with a limited number of channels is described, which assigns calls in a max-minimum method, in a first embodiment according to the type of call and sector to be served.
Abstract: An improved two-way radio communication system having a limited number of channels is disclosed which assigns calls in a max-minimum method, in a first embodiment according to the type of call and sector to be served. This disclosed first embodiment includes a method that ascertains the type of call, handoff or first assignment, and assigns a server with a given central controller to a channel frequency within the requestor sector that minimizes interference to present users. The method of the second embodiment controls requests for assignment to a limited number of channels to reduce adjacent channel interference to and from the requestor with respect to present users operating on a system by utilizing one or more thresholds to arrange channel assignments based upon progressively larger or smaller values of received signal strength.

Patent
11 Jun 1986
TL;DR: In this paper, a magnetic disk drive channel circuitry is described that generates eight incremental values of write current and eight incremental value of delta-V (the minimum voltage change per unit time which tests signals to discriminate between data and noise).
Abstract: A magnetic disk drive channel circuitry is shown and described that generates eight incremental values of write current and eight incremental values of delta-V (the minimum voltage change per unit time which tests signals to discriminate between data and noise). Each of these variable parameter values may be program selected by a three bit bus signal. This variability testing of an adaptation to the optimum parameter value for each head media combination and by grouping tracks in contiguous data bands, the parameters may be optimized for tracks near the inner diameter, the outer diameter and in the middle band. The variable delta-V can also be used as an additional data recovery tool wherein re-reading with a lower value enhances recovery of missing bit errors and re-reading with an increased value can assist recovery from an extra bit error.

Patent
24 Jul 1986
TL;DR: In this paper, a fiber-optic distribution system is disclosed which distributes broadband signals received by a network termination circuit from a broadband communications network (B-ISDN or cable-television network) among a plurality of subscriber terminals.
Abstract: A fiber-optic distribution system is disclosed which distributes broadband signals received by a network termination circuit from a broadband communications network (B-ISDN or cable-television network) among a plurality of subscriber terminals. The network termination circuit (4) contains devices for separating a forward channel and a backward channel. It also includes electric-to-optical and optical-to-electric transducers (5,6). The distribution system contains a fiber-optic multi-port coupler (10) which is made by the fusion technique and interconnects a plurality of optical fibers (12, 13, 14). On the subscriber's side, each of these optical fibers forms the forward channel and the backward channel for one of the terminals (32). On the network side, one of these optical fibers (16) forms the forward channel for the broadband signals, and all other optical fibers (17, 18) are combined to form the narrow-band backward channel. They are connected to a common large-area photodiode (6). As the backward channel is a narrow-band channel, the fact that large-area photodiodes, such as PIN diodes, are relatively slow does not cause any bandwidth problems.

Journal ArticleDOI
TL;DR: Calculation shows that the first improvements on Shannon's outer bound are close to optimum when applied to the Blackwell multiplying channel (BMC).
Abstract: Shannon's two-way channel problem has attracted the attention of information theorists for many years. In a classic paper Shannon gave both an outer and an inner bound to the capacity region of the two-way channel. Schalkwijk recently obtained an improvement to the inner bound for the Blackwell multiplying channel (BMC). We present the first improvements on Shannon's outer bound. Calculation shows that our results are close to optimum when applied to the BMC.

Patent
31 Dec 1986
TL;DR: In this article, a method and means for maintaining continuous bit synchronization of data transmitted from a remote unit through a base unit to a landline unit is disclosed, where an input data stream at a first bit rate, such as digitized or encrypted speech, is interleaved with a plurality of signalling words, and transmitted over an RF channel at a second bit rate.
Abstract: A method and means for maintaining continuous bit synchronization of data transmitted from a remote unit through a base unit to a landline unit is disclosed. An input data stream at a first bit rate, such as digitized or encrypted speech, is interleaved with a plurality of signalling words, and transmitted over an RF channel at a second bit rate. The base site recovers the clock of the received data, strips off the signalling word, modifies the bit rate of the received data, and adjusts the recovered clock rate to provide an output data stream which is in bit synchronization with the input data stream and within a predetermined modem specification. The encrypted data is then sent over landlines to a decryption unit which requires bit synchronization.