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Communications, IEEE Transactions on

Issue 9 • Date September 1979

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  • [Front cover and table of contents]

    Publication Year: 1979 , Page(s): 0
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 1979 , Page(s): 0
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    Freely Available from IEEE
  • Transparent Wideband Data Transmission in Digital Communication Networks

    Publication Year: 1979 , Page(s): 1302 - 1309
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    This paper presents a systematic study of the possibilities of time-transparent and of code-transparent binary data transmission in digital communication networks where PCM or differential PCM (DPCM) systems are employed for the encoding of speech or video signals. To describe the effects that occur if data signals instead of speech or video signals are sampled and transmitted by these two encoding methods, time-transparency and code-transparency are defined and are used as figures of merit. The occurrence of time-quantizing errors and amplitude errors at the decoder output is statistically analyzed. The limitations to be considered in the various applications are described, and time- and code-transparency are evaluated quantitatively. The predictions of the analysis are then compared with the results obtained through simulations. The comparison shows that for data rates below 10 percent of the bit rate (bits per second) in the digital channel, conventional PCM and DPCM encoding are acceptable for binary data transmission and have the advantage of easy signal integration. For higher data rates special data encoding is necessary. The encoding method analyzed here is dual-mode. View full abstract»

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  • Experimental Mesurements of Viterbi Decoding in Burst Channels

    Publication Year: 1979 , Page(s): 1360 - 1366
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    Experimental measurements of the performance of Viterbi-algorithm decoders in the presence of burst-interference are presented. Results are shown for different code rates and different interference-burst duty factors, amplitudes, and burst lengths. Considerable stress is placed on interference-mitigation techniques (such as symbol erasure, blanking, limiting, and quantizer backoff) that can be added at the receiver prior to the decoder. There is generally good agreement between the measured results and several methods for calculating approximate performance. View full abstract»

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  • Performance of Optical Receivers with Avalanche Photodetection

    Publication Year: 1979 , Page(s): 1315 - 1321
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    This paper reports the results of a computer study to numerically evaluate the digital performance of an optical receiver with avalanche photodetectors. Exact and approximate APD statistics were implemented and error probabilities in the range l0^{-1} to l0^{-4} were computed. Both shot-noise and receiver-noise limited conditions were examined, and on-off keying, binary pulse comparison, multilevel intensity, and PPM signaling formats are considered. View full abstract»

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  • Frequency Detectors for PLL Acquisition in Timing and Carrier Recovery

    Publication Year: 1979 , Page(s): 1288 - 1295
    Cited by:  Papers (60)  |  Patents (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    A significant problem in phase-locked loop (PLL) timing and carrier extraction is the initial acquisition. Very narrow loop bandwidths are generally required to control phase jitter, and acquisition may depend on an extremely accurate initial VCO frequency (VCXO) or sweeping. We describe two simply implemented frequency detectors which, when added to the traditional phase detector, can effect acquisition even with very small loop bandwidths and large initial frequency offsets. The first is the quadricorrelator, previously applied to timing recovery by Bellisio, while the second is new, and called a rotational frequency detector. The latter, while limited to lower frequencies and higher signal-to-noise ratios, is suitable for many applications and can be implemented with simpler circuitry. View full abstract»

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  • KEYPAC--A Telephone Aid for the Deaf

    Publication Year: 1979 , Page(s): 1366 - 1371
    Cited by:  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    This paper presents a telecommunications system, KEYPAC (Key Phone Alphanumeric Communication), that enables a user to communicate over the telephone without the use of speech. The design of this system was motivated by the need for a low cost, yet simple and useful means of telephone communication in the deaf community. The KEYPAC system provides a flexible means for speechless telephone communication by utilizing an ordinary pushbutton telephone as a transmitting device. Alphanumeric messages are sent by pressing sequences of keys according to a simple coding scheme of two keys per letter and one key per number (0-9). Message reception is accomplished with the use of a small, hand-held receiver that is attached to the telephone. The receiver decodes sequences of D.T.M.F. (Dual Tone Multi Frequency) audio tones and displays the resulting messages on a visual display or hard copy printer. View full abstract»

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  • The Effect of Bandlimiting Filters on Probability of Error of MSK

    Publication Year: 1979 , Page(s): 1348 - 1353
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    Minimum Shift Keying (MSK) is a method of modulation which can be viewed as a special case of Frequency Shift Keying or a special form of Offset Quadrature Phase Shift Keying; therefore, it can be detected either by a discriminator or with a pair of matched filters. In the latter case, the system is optimal, provided there are no bandlimiting filters in the transmitter and receiver. These filters introduce intersymbol interference and hence degrade the performance of the system. In this paper we investigate analytically the effect of a bandlimiting filter in the receiver on the error probability of the system, presenting numerical results when that filter is of the Butterworth type. It is shown that a very simple suboptimal detector outperforms the matched filter detector so long as 2W/R_{b} < 1.3 , where Rbis the bit rate and W is the single sided 3 dB bandwidth of the bandlimiting filter. View full abstract»

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  • Hardware for Detection and Partial Correction of PCM Transmission Errors

    Publication Year: 1979 , Page(s): 1310 - 1315
    Cited by:  Papers (2)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    In pulse code modulation of speech, transmission errors cause changes in the statistical properties of the received samples. Recently published work describes computer simulations of a difference detection and correction (DDC) system which detect errors on the basis of these changes. The system examines the differences between adjacent received samples. If a particular difference exceeds a threshold, which is dependent on the rms value of a block of 64 differences, the quantized sample responsible for this large difference is deemed to be erroneous. A nonlinear filter of the median type is then introduced as a corrector. We now present a comprehensive description of the hardware realization of this system, and present measured results of signal-to-noise ratio (snr) as a function of bit error rate, input power and the error criterion for narrow-band white noise input signals. An improvement of 6 dB in snr is achieved for error rates between 0.2 and 2.0%. The snr results are consistent with subjective impressions of the quality of speech processed by the DDC system. View full abstract»

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  • Data Performance in a System Where Data Packets are Transmitted During Voice Silent Periods--Single Channel Case

    Publication Year: 1979 , Page(s): 1371 - 1375
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    We develop a mathematical analysis for the steady state performance of a system where voice calls and data packets are transmitted over the same channel. The voice calls have priority over the data packets, in that the data packets are transmitted only when there are no voice calls present in the system or the voice conversation is in a long silent period. View full abstract»

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  • Effects of Digital Demodulation on Component Coding of NTSC Color Signals

    Publication Year: 1979 , Page(s): 1342 - 1348
    Cited by:  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    Effects of nonideal filtering in the digital demodulation of the composite NTSC signal into luminance and chrominance components on the coding of the luminance component are discussed. The residual chrominance component is shown to cause degradation in prediction and/or motion detection algorithms which are based on line or frame difference signals. Simple techniques for reducing these effects using chrominance-band rejection filters are presented and the efficacy of these methods are verified by simulation. View full abstract»

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  • Generation and Performance of Quadraphase Welti Codes for Radar and Synchronization of Coherent and Differentially Coherent PSK

    Publication Year: 1979 , Page(s): 1296 - 1301
    Cited by:  Papers (3)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    A class of quadraphase synchronizing sequences, whose lengths may be any power of two, is constructed using codes originally reported by Welti. It is shown that there exist realizations of the codes for both coherent and differentially coherent PSK systems. Like binary maximal length sequences (BMLS) their generation and detection require circuits whose complexity grows as \log _{2}N , where N is the codelength. Their aperiodic correlation properties, however, are superior to those of any BMLS-their correlation sidelobes are identically zero, giving unambiguous asynchronous detection. View full abstract»

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  • Image Compression Using Block Truncation Coding

    Publication Year: 1979 , Page(s): 1335 - 1342
    Cited by:  Papers (212)  |  Patents (45)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2104 KB)  

    A new technique for image compression called Block Truncation Coding (BTC) is presented and compared with transform and other techniques. The BTC algorithm uses a two-level (one-bit) nonparametric quantizer that adapts to local properties of the image. The quantizer that shows great promise is one which preserves the local sample moments. This quantizer produces good quality images that appear to be enhanced at data rates of 1.5 bits/picture element. No large data storage is required, and the computation is small. The quantizer is compared with standard (minimum mean-square error and mean absolute error) one-bit quantizers. Modifications of the basic BTC algorithm are discussed along with the performance of BTC in the presence of channel errors. View full abstract»

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  • Approximations of Queue Dynamics and Their Application to Adaptive Routing in Computer Communication Networks

    Publication Year: 1979 , Page(s): 1331 - 1335
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    Various adaptive algorithms have been proposed for routing, flow and congestion control in packet-switched computer communication networks. In most of them, information on queue lengths, or equivalently, time delays, at various points in the network is required for proper adaptation. Since up-to-date information is not always available, these quantities must be estimated based on prior information. This paper presents approximations for the dynamic behavior of the M/M/1 queue which is used to yield the desired estimates of queue lengths. Based on the assumption of finite (but arbitrarily large) storage, a closed form expression for the evolution in time of the queue length distribution is obtained. From this expression various approximations for estimated queue length are extracted. A simple expression for the "relaxation time" of the queue is also deduced as a function of utilization factor and service time. The approximations are applied to a simple adaptive routing example in which packets are routed along the transmission path having the shortest estimated queue, based on delayed information. View full abstract»

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  • Resolution of Overlapping Echo Signals in Sonar/Radar Systems

    Publication Year: 1979 , Page(s): 1321 - 1325
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    A procedure is developed for resolving a time sequence of overlapping echo signals and estimating an a priori unknown number of echoes present in the sequence. The proposed receiver structure is an extension of the conventional narrow-band matched filter envelope detector. Computer simulation results are presented which show the feasibility and satisfactory performance of the receiver proposed. View full abstract»

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  • A Coding Scheme for Conflict-Free Multiaccess Using Global Scheduling

    Publication Year: 1979 , Page(s): 1353 - 1360
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    A coded multiple access protocol (CMAP) to improve the delay-throughput performance of a global scheduling multiaccess model for data communication over a broadcast channel, which exhibits a short propagation delay, is described and analyzed. Upper and lower bounds on delay-throughput characteristics are obtained. It is shown that CMAP reduces system delay compared to the 1-out-of- M code. This reduction is attained at the expense of a dialogue exchange between the central scheduler and the users. View full abstract»

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  • Demand Assigned Multiple Access Systems Using Collision Type Request Channels: Traffic Capacity Comparisons

    Publication Year: 1979 , Page(s): 1325 - 1331
    Cited by:  Papers (21)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    The traffic carrying capabilities of demand assigned multiple access (DAMA) systems in which requests for communication circuits are transmitted over shared collision type channels to a master controller are investigated. The circuit request protocol permits both busy and blocked responses in addition to circuit allocations. The theoretically maximum traffic capacity is determined and it is shown that even very simple systems of this type can achieve efficient bandwidth utilization in realistic situations. View full abstract»

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  • The Effects of Repeater Hard-Limiting, Filter Distortion, and Noise on a Pseudo-Noise, Time-Of-Arrival Estimation System

    Publication Year: 1979 , Page(s): 1271 - 1279
    Cited by:  Papers (2)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    Employment of a repeater in a communication system may lead to the introduction of several sources of potential performance degradation. They are hard-limiting, IF filter group delay distrotion and center frequency offset, and additional noise in the links from transmitter-to-repeater and repeater-to-receiver. Specifically, the hardlimiter and IF filter may introduce signal waveform distortion while the former may also introduce signal-to-noise ratio suppression. In this paper the impact of the above on a pseudo-noise (PN) time-of-arrival (TOA) estimation system is considered. The assumed modulation scheme is differential phase shift keying (DPSK) and realistic nonconstant envelope signals are considered; the performance criterion is TOA estimate standard deviation. One surprising result is that the presence ot the limiter tends to degrade performance; this is contrary to corresponding results that have been derived for data detection. It was also found that performance degrades quite gradually with increasing IF filter differential group delay over the signal bandwidth. Finally, although analytical results presented here pertain specifically to the hard-limiter, they may be straightforwardly extended to determine the effects of repeater n th law devices. View full abstract»

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  • A Failsafe Distributed Routing Protocol

    Publication Year: 1979 , Page(s): 1280 - 1287
    Cited by:  Papers (71)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (912 KB)  

    An algorithm for constructing and adaptively maintaining routing tables in communication networks is presented. The algorithm can be employed in message as well as circuit switching networks, uses distributed computation, provides routing tables that are loop-free for each destination at all times, adapts to changes in network flows, and is completely failsafe. The latter means that after arbitrary failures and additions, the network recovers in finite time in the sense of providing routing paths between all physically connected nodes. For each destination, the routes are independently updated by an update cycle triggered by the destination. View full abstract»

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  • Link Systems with Delay

    Publication Year: 1979 , Page(s): 1261 - 1270
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (824 KB)  

    This paper discusses two classical methods of calculating grade of service parameters for link systems, i.e., the methods of Jacobaeus and Lotze. The possibility of extending these theories to cover delay systems and in particular to calculate the waiting time distribution is looked into. Numerical results from the theories are compared with simulations results. Throughout this paper, pure Poisson arrivals and negative exponentially distributed service times are considered. View full abstract»

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Aims & Scope

IEEE Transactions on Communications focuses on all telecommunications including telephone, telegraphy, facsimile, and point-to-point television by electromagnetic propagation.

 

 

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Editor-in-Chief
Robert Schober
University of British Columbia