IEEE Transactions on Communications

It is shown that When Pierce's pulse-position modulation scheme with 2Lpositions is used on a self-noise-limited directdetection optical communication channel, there results a 2L-ary erasure channel that is equivalent to the parallel combination ofL"completely correlated" binary erasure channels. The capacity of the full channel is the sum of the capacities of the ... View full abstract»

This paper examines the performance of coherent QPSK and QASK systems combined with FH or FH/PN spread spectrum techniques in the presence of partial-band multitone or noise jamming. The worst-case jammer and worst-case performance are determined as functions of the signal-to-background noise ratio (SNR) and signal-to-jammer power ratio (SJR). Asymptotic results for high SNR are shown to have a li... View full abstract»

This paper considers the performance of QPR in the presence of the identical jamming postulated in Part I. Although a QPR system employs a single sample detector in its receiver, while QASK (or QPSK) requires a matched-filter type of receiver., it is shown that the coherent detection performances of the two in the presence of the intentional jammer have definite similarities. View full abstract»

This paper presents closed form expressions for average delay in a class of work conserving single server queueing systems suggested by, but not limited to, the behavior of heavily I/O oriented computing systems. Jobs arrive at the system according to a Poisson process, and each job consists of a set of tasks which must be accomplished in a prescribed order. The tasks with indexihave a ... View full abstract»

Simple two-parameter formulas are presented for the functions involved in the amplitude-phase and the quadrature nonlinear models of a TWT amplifier, and are shown to fit measured data very well. Also, a closed-form expression is derived for the output signal of a TWT amplifier excited by two phase-modulated carriers, and an expression containing a single integral is given when more than two such ... View full abstract»

The probability of error of both a 16-ary QASK system and an MSK system, each operating over a Rician fading channel, is considered. The channel model has two key features: short term variations are modeled by making the channel frequency selective, and long term variations are accounted for by allowing the specular component of the received signal to fade according to a Rayleigh density. The impr... View full abstract»

This paper explores the constraints on the design of twowire repeaterless digital subscriber loop (DSL) systems. Broadly categorized, the design depends on the technical feasibility of the approach used to achieve two-wire transmission, constraints related to compatibility with other systems sharing the same cable, and immunity to central office noise. Each of these varies With the choice of syste... View full abstract»

With digital connectivity, future subscribers will be able to exercise local and network services involving the routine delivery, management, and processing of information. Accelerated by rapidly advancing technology, the evolutionary process towards digital connectivity and integrated voice and data services in the network is underway. This paper describes the methods of integrating voice and inf... View full abstract»

In this paper the main characteristics and the performance of two systems implemented for two wire digital transmission on subscriber lines are presented. Both systems utilize different time intervals to transmit bursts of bits in the two directions with an information bit rate of 80 kbits/s and a line bit rate in the bursts of 256 kbits/s. One system employing WAL2 as the line code exhibits extre... View full abstract»

The digital nonsecure voice terminal (DNVT) is an alldigital four-wire telephone set used for noncryptographic communication over digital channels. It operates at 16 or 32 kbits/s. In this paper we describe the physical and electrical implementation of the telephone. The circuits are described to the block diagram level. The various states or phases of the signaling system, signal recognition code... View full abstract»

Adopting digital techniques in the local network area will enhance the possibility of extending digital operation capability to the subscriber's equipment. The problem is to convey digital signals at a bit rate of at least 64 kbits/s in both directions over existing two-wire subscriber loops. This paper describes a time-shared two-wire digital subscriber transmission system in which the directiona... View full abstract»

In this paper we consider the problem of organizing a set of mobile, radio-equipped nodes into a connected network. We require that a reliable structure be acquired and maintained in the face of arbitrary topological changes due to node motion and/or failure. We also require that such a structure be achieved without the use of a central controller. We propose and develop a self-starting, distribut... View full abstract»

A retransmission Protocol for a broadcast connection (point-to-multipoint) is proposed and its performance characteristics are considered. The protocol is designed for transfers of large files Over a satellite channel that is time-shared to carry both the data from the broadcasting transmitter and the set of acknowledgments from the multiple receiver sites. A mathematical model of the transmission... View full abstract»

An algorithm is presented which enables one ReedSolomon decoder to process other Reed-Solomon encoded data from a different code. All that is required is that both codes have the same length, the same rate, and the same field of coefficients. View full abstract»

A digital telephone concept is described where each subscriber set sends and receives digital signals (8-bit PCM). Duplex, simultaneous operation of extensions on a single pair of wires is made possible by time division multiplex (TDM) techniques. A successful feasibility demonstrator of the concept that operates at 512 kbits/s is also described. It has a digital switch at one end and digital tele... View full abstract»

This paper describes a new integrated service network using packetized voice/data technology which was developed in consideration of the sophisticated service demands for voice, data, and facsimile communication. A major problem in constructing this network is in the local distribution network, i.e., the subscriber interface unit, the local end office, and the subscriber loop which connects them. ... View full abstract»

A new type of digital echo canceler for two-wire digital transmission is presented. The new principle involves very simple signal processing and is thus an interesting alternative for digital transmission on subscriber lines. The principle is compared with other echo cancellation techniques, and it is shown how choice of line code, equalization, and carrier recovery are affected by the new echo ca... View full abstract»

Encryption is an efficient method for information protection in communication links which are subject to wiretapping. In this paper we discuss the application of encryption to satellite communication systems in which the satellite has on-board processing capability. The on-board processor can be used in the key distribution process. Two examples of such processes are described. The first requires ... View full abstract»

The theory of error rates for narrow-band digital FM with limiter-discriminator detection and integrate and dump postdetection filtering is considered. The goal is that of simplifying the existing theory, which has evolved primarily in the frequency domain, and requires numerical integration and differentiation of Fourier series expansions, numerical convolution, and multibit pattern averaging. A ... View full abstract»

In comparing two proposed frequency-hopping mobile radio systems for digitized speech, Goodman et al. have observed that the system employing multiple-frequency-shift-keying (MFSK) can accommodate many more users than the ones with differential-phaseshift-keying (DPSK). Besides the difference in modulation methods, the MFSK system uses hard-limited combining while the DPSK one uses linear combinin... View full abstract»

A basic property of data sources in interactive applications is burstiness, i.e., short periods of activity followed by long idle periods. In these same applications message delay is the primary performance criterion. The combination of bursty flow and a delay criterion leads to a source encoding problem in which delay plays a central role. A salient feature of this problem is that there is a trad... View full abstract»