The rate of a class of random processes
Algorithm applied to specific classes of random processes for calculating minimum channel capacity required by transmission system for sources in each class
Sakrison, D. J.↗
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Optimized telemetry systems for advanced Mariner-type spacecraft
Mariner-type spacecraft telemetry system optimization, considering channel capacity
Gilder, J. R.↗
Noiseless linear feedback and analog data transmission
Noiseless linear feedback limitation over bandlimited channel capacity in analog data transmission
Butman, S.↗
An improved learning decoder
Learning decoder was developed which operates at system data rate without limiting data rate. Decoder is much simpler than those in existence, operates near Shannon's channel capacity, and automatically recovers operation after loss of signal.
Doland, G. D.↗
Communication theory of quantum systems
Communication theory problems incorporating quantum effects for optical-frequency applications are discussed. Under suitable conditions, a unique quantum channel model corresponding to a given classical space-time varying linear random channel is established. A procedure is described by which a proper density-operator representation applicable to any receiver configuration can be constructed directly from the channel output field. Some examples illustrating the application of our methods to the development of optical quantum channel representations are given. Optimizations of communication system performance under different criteria are considered. In particular, certain necessary and sufficient conditions on the optimal detector in M-ary quantum signal detection are derived. Some examples are presented. Parameter estimation and channel capacity are discussed briefly.
Yuen, H. P. H.↗
A time-division multiplexing system for asynchronous high-rate telemetry.
A time-division multiplexing system has been developed that is significantly different from commercially available equipments. Multiplexing is achieved by interleaving blocks of data from each source, preceded by a short coded bit pattern specifying the source of that particular block of data. Data blocks are transmitted as they become available from each particular source. Hence, synchronism of the input and output rates is not required. The prototype system can accommodate input rates as high as 461 kbit/sec on a single input channel, and output rates as high as 953 kbit/sec. The system makes possible use of an excess of 90% of channel capacity for information transmittal.
Appel, R. L.↗
Time-based priority selection for analog circuits
Unlimited channel capacity multiplexing circuit is hierarchially structured to achieve priority encoding. Circuit could be used for automatic patient monitoring systems and diagnostic test systems in automotive and communications industry.
Fageol, J. D.↗
Transmission strategies for atmospheric entry probes.
In this article we shall be concerned with the question of how to maximize the expected data return when the channel capacity cannot be predicted in advance. An example of this type is a planetary entry probe to Venus or Jupiter, whose atmospheric transmission characteristics are not yet fully known. And even if they were known, these transmission characteristics would be subject to unpredictable changes due to planet weather and/or entry trajectory.
Butman, S.↗
An operational video data compression system for ATS and ITOS
An operational data compression system has been developed and implemented for transmission of digitized ATS and ITOS-VHRR satellite video data over the wideband communication link between the Wallops Island, Va. Command and Data Acquisition Station and the National Environmental Satellite Service at Suitland, Md. This system uses minicomputers for the coding and decoding of the data to achieve maximum flexibility together with specially designed interface equipment for greater efficiency. No loss in data quality occurs due to the compression, and, in certain cases, data is transmitted which would be otherwise unavailable due to the limited channel capacity. This paper describes the method of compression, the equipment used, and the compression results attained.
Kutz, R. L.↗
Adaptive multibeam phased array design for a Spacelab experiment
The parametric tradeoff analyses and design for an Adaptive Multibeam Phased Array (AMPA) for a Spacelab experiment are described. This AMPA Experiment System was designed with particular emphasis to maximize channel capacity and minimize implementation and cost impacts for future austere maritime and aeronautical users, operating with a low gain hemispherical coverage antenna element, low effective radiated power, and low antenna gain-to-system noise temperature ratio.
Noji, T. T.↗
Phase-locked telemetry system for rotary instrumentation of turbomachinery, phase 1
A telemetry system for use in making strain and temperature measurements on the rotating components of high speed turbomachines employs phase locked transmitters, which offer greater measurement channel capacity and reliability than existing systems which employ L-C carrier oscillators. A prototype transmitter module was tested at 175 C combined with 40,000 g's acceleration.
Adler, A.↗
Digital and analog communication systems
The book presents an introductory treatment of digital and analog communication systems with emphasis on digital systems. Attention is given to the following topics: systems and signal analysis, random signal theory, information and channel capacity, baseband data transmission, analog signal transmission, noise in analog communication systems, digital carrier modulation schemes, error control coding, and the digital transmission of analog signals.
Shanmugam, K. S.↗
Comparison of three-phase modulation with two-phase and four-phase modulation
For a constant added noise density at high signal-to-noise ratios and for the same error rate, three-phase PSK requires about 0.75 dB less energy per bit than two-phase or four-phase PSK. However, at very low signal-to-noise ratios, three-phase PSK requires about 0.74 dB more energy per bit of channel capacity than two-phase or four-phase PSK.
Pierce, J. R.↗
Coding for the photon channel
Motivated by a recent paper of Pierce, we consider the problem associated with coding for optical communications systems that use photon-counting techniques. Making certain realistic assumptions, we find that external noise sources are negligible, and that channel capacity (measured in nats per photon) is infinite. However, quantum effects made the design of an efficient system at rates above about 5 nats per photon very difficult.
Mceliece, R. J.↗
Video framerate, resolution and grayscale tradeoffs for undersea telemanipulator
The product of Frame Rate (F) in frames per second, Resolution (R) in total pixels and grayscale in bits (G) equals the transmission band rate in bits per second. Thus for a fixed channel capacity there are tradeoffs between F, R and G in the actual sampling of the picture for a particular manual control task in the present case remote undersea manipulation. A manipulator was used in the MASTER/SLAVE mode to study these tradeoffs. Images were systematically degraded from 28 frames per second, 128 x 128 pixels and 16 levels (4 bits) grayscale, with various FRG combinations constructed from a real-time digitized (charge-injection) video camera. It was found that frame rate, resolution and grayscale could be independently reduced without preventing the operator from accomplishing his/her task. Threshold points were found beyond which degradation would prevent any successful performance. A general conclusion is that a well trained operator can perform familiar remote manipulator tasks with a considerably degrade picture, down to 50 K bits/ sec.
Ranadive, V.↗
20 x 20 IF switch matrix for SS-TDMA systems
Satellite-switched TDMA, an effective means for the increasing of communication satellite channel capacity and the improvement of system flexibility, requires that the spacecraft carry an IF switch matrix in order to provide interconnectivity among multiple beam antennas. Attention is presently given to the development of a 20 x 20 IF switch matrix for the NASA 30/20 GHz communications satellite which will provide a 2.5 GHz bandwidth at C-band frequencies with a switching speed of 10 nsec. Switch matrix architecture, switching device characteristic, and distribution control unit design practices are discussed, together with switch matrix reliability.
Ho, P. T.↗
A TWT amplifier with a linear power transfer characteristic and improved efficiency
A novel method called "Dynamic Velocity Taper' to linearize the Pout versus Pin transfer characteristic that does not require any extraneous circuitry or tuning, has large bandwidth capabilities ( 10 percent) and offers also an increase in the intrinsic traveling wave tube (TWT) efficiency by 1 to 2 dB is described. In addition, the method permits the TWT to be operated at or near the synchronous voltage (b plus or minus o) which produces a flat small and large signal gain responses and low AM to PM conversion. The physics of the method and experimental verification are given. The implementation should have a significant impact on TWT performance and increase the channel capacity of communication satellites.
Kosmahl, H. G.↗
Optical communication with laser diode arrays
The performance of a direct-detection optical communication system in which the laser transmitter sends short optical pulses of selected nonoverlapping center frequencies is analysed. This modulation format, in which a single light pulse is sent in one of M time slots at one of N optical center frequencies, is referred to as color coded optical pulse position modulation (CCPPM). The optimum energy-efficiency of this system, as measured by the channel capacity in nats per photon, exceeds that of ordinary optical pulse position modulation which uses a pulsed laser of fixed optical frequency. Reliable communication at optimal energy efficiency is easily achieved through the use of modest block length Reed-Solomon codes with the code words represented as CCPPM symbols.
Davidson, F.↗