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Communications, IEEE Transactions on

Issue 10 • Date October 1980

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Displaying Results 1 - 14 of 14
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • [Back cover]

    Page(s): 0
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    Freely Available from IEEE
  • The Effect of Choosing the Switches for Rearrangements in Switching Networks

    Page(s): 1832 - 1834
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    Known rearrangement algorithms proposed by Slepian and Paull (method 1) involve two middle switches of the three-stage Clos network. These switches are chosen arbitrarily. However, the middle switches selection rules affect the rearrangement process. In this paper four methods for choosing the switches were studied. Simulation results and analysis have shown that the allocation of the least used switches can decrease the volume of computation required for rearrangements. In the case of limited rearrangement, this method improves the blocking performance of a network. View full abstract»

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  • On Noise Immunity of Feedback Communication Systems

    Page(s): 1844 - 1847
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    This paper compares the noise immunities of feedback communication systems for two particular types of systems noise: Gaussian white noise, which is typical of radio and telephone communication, and Poisson-distributed noise, which is typical of laser communication. The comparison shows that as the error probability requirement is made more stringent, the use of feedback will save commensurately more energy in both cases. View full abstract»

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  • Priority Channel Assignment in Tandem DSI

    Page(s): 1802 - 1809
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    DSI (digital speech interpolation) is a technique for increasing the utilization of telephone transmission facilities by allocating transmission channels during intervals of active speech (talkspurts) only. The use of DSI for tandem connections, where DSI links are connected in cascade via circuit switching, poses a problem, however, since the voice-quality degradation that is inevitable in each DSI link can be accumulated to an unacceptable level as the number of DSI links in an end-to-end call connection increases. To cope with this problem, we propose the use of a priority channel assignment technique. An example of such a technique is one that provides preference in channel assignment at each DSI process in a network to calls that have passed through at least one prior DSI link. We evaluate the performance of priority assignment schemes for TASI-type DSI analytically and show that the overall voice-quality degradation of a multi-DSI link call can be improved significantly through the use of priority assignment. View full abstract»

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  • Optimal Bandwidth Assignment on Up- and Downlinks of Satellite with Buffer Capacity

    Page(s): 1809 - 1818
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    This paper considers a satellite communication system with the slotted ALOHA access mode where the satellite is assumed to have on-board regeneration ability and the finite buffer capacity for storing noncollided packets from the uplink. The system is analyzed with the downlink bandwidth restricted to1/Lof the uplink bandwidth, and with the conventional slotted ALOHA system whereL = 1and the buffer size at the satellite is equal to zero. Maximum throughput and throughput-delay characteristics of this system are analytically obtained. The satellite is given an optimal buffer size to achieve maximum throughput and minimum packet transmission delay. It is shown that the constraints that lead to the downlink bandwidth being lower than the uplink bandwidth do not necessarily result in throughput penalties in a buffered satellite system. Furthermore, when the total bandwidth which can be divided between up- and downlinks is given, if two or three times that of the downlink is assigned to the uplink and if the satellite has buffer storage space only for a few packets, we show that maximum throughput of the system will be improved about 40 percent with little change in delay characteristics in comparison with that of the conventional slotted ALOHA system where the given total bandwidth is equally divided between up- and downlinks. View full abstract»

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  • A Fast-Switching Low-Loss 12-GHz Microstrip 4-PSK Path Length Modulator

    Page(s): 1824 - 1828
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    A 4-PSK microstrip modulator operating at data rates of up to 800 Mbits/s at 12 GHz is described. The circuit is made of two cells in series. Each cell consists of a 3-dB branch-line hybrid coupler and two BTL p-i-n diodes. One cell provides 0° or 90° phase shifts, and the Other 0° or 180° phase shifts, so that four carrier phase values are obtained by appropriately exciting the two cells. The switching time of each cell is 200 ps. Simultaneous switching of both cells increases the switching time to a maximum value of 400 ps. The phase waveforms are nearly rectangular at the above-mentioned data rates. RF insertion loss is 1 dB ± 0.1dB for the four phase values over the 11.7-12.2 GHz frequency band. View full abstract»

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  • A Spread Spectrum System with Frequency Hopping and Sequentially Balanced Modulation--Part II: Operation in Jamming and Multipath

    Page(s): 1785 - 1793
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    The broad-band noise performance of a spread spectrum system with frequency hopping and sequentially balanced modulation was analyzed in Part I of this paper. Here, the analysis is extended to include operation In jamming environments and in specular multipath. Bit-error probability and ranging accuracy curves are presented in each case. View full abstract»

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  • Multiplexing Low-Speed Buffered Data Terminals

    Page(s): 1838 - 1843
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    When terminals (data and/or voice), connected to an asynchronous time division multiplexer (ATDM), are buffered and operate at low speed, the arrivals at the multiplexer are correlated. In this paper, we consider the finite buffer behavior of an ATDM with such terminals. An earlier study by Rudin [6] is a special case of this approach. The treatment here is also an improvement over the analysis by Birdsall et al. [1] of an ATDM with speech sources and is suitable for packet voice applications. View full abstract»

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  • Quantization Noise in Adaptive Delta Modulation Systems

    Page(s): 1794 - 1802
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    New analytical formulas for quantization noise of two widely known adaptive delta modulation (ADM) systems, continuously variable slope delta modulation (CVSD) and Jayant's firstorder constant factor delta modulation (CFDM), have been obtained. These formulas are derived based upon the previously obtained results for linear delta modulation (LDM) and adaptive differential pulse code modulation (ADPCM). To verify the results, computer simulation has been done using band-limited Gaussian signals. Close agreements between the formulas and the simulation results have been obtained in the wide range of the input signal level. View full abstract»

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  • Useful Bounds on the Performance of a Spread-Spectrum Mobile Communication System in Various Fading Environments

    Page(s): 1819 - 1823
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    Previous results on the spread-spectrum system for mobile communication proposed by Cooper and Nettleton have been obtained by computer simulation. In this paper, closed-form bounds on the bit error rate are derived for flat, Rayleigh, and Rician fading conditions. For more general types of fading, the saddle point method is used. Since the bounds are easily computed, they are more useful than computer simulations for analyzing system performance. View full abstract»

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  • Application of Monolithic CMOS Switched-Capacitor Filters and Amplifiers for Signal Processing

    Page(s): 1828 - 1832
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    A custom monolithic CMOS array was designed and integrated for use in meeting the analog conditioning requirements for microsignal processors. These processors are used in "smart" sensors for the purposes of detection and classification. Constrained by very low power dissipation requirements, this array provides a variety of bandpass and low-pass filter functions and programmable CMOS operational amplifiers for AGC amplification for signals in the audio region. Specifically, the custom chip contains 12 poles based on switchedcapacitor techniques partitioned into a 6-pole low-pass filter ladder configuration, and three 2-pole bandpass and low-pass state variable filter configurations. The amplifiers were used in conjunction with an associated microprocessor for software-controlled AGC. A mask change can provide for different capacitor ratios, and hence, frequency responses. Also, the switch clock rates can be used to vary the filter characteristics. Operating from a single +5 V supply, this standard process chip dissipates about 2 mW, and meets all predicted performance characteristics. View full abstract»

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  • Second-Order Greedy Algorithms for Centralized Teleprocessing Network Design

    Page(s): 1835 - 1838
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    We consider the problem of designing a centralized telecommunication network comprised of multipoint lines given a set of terminal locations, traffic requirements, and a common central site. The optimal solution to this problem is a capacitated minimal spanning tree. We develop a class of heuristic algorithms for the solution of this problem by imbedding existing heuristics, referred to as first-order greedy algorithms, inside a loop where small, carefully chosen sets of arcs are alternately forced in and out of the solution. The resultant procedure is shown to be superior to existing techniques, producing solutions typically 2 percent better, while requiring only a modest amount of additional computer time. View full abstract»

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  • RF Reference Signal Transport by Optical Fibers

    Page(s): 1847 - 1848
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    Among the various applications of optical fibers, the transmission of time or frequency reference signals seems to have some interest in view of the immunity of the fibers from electromagnetic disturbances. An analysis of the possible causes of phase fluctuation in a link and a feasibility test for the transmission of a local oscillator signal in a receiving system are reported. 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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Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia