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Communications, IEEE Transactions on

Issue 3 • Date March 1981

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Displaying Results 1 - 22 of 22
  • [Front cover and table of contents]

    Publication Year: 1981 , Page(s): 0
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    Freely Available from IEEE
  • Guest Editors' Prologue

    Publication Year: 1981 , Page(s): 185 - 186
    Cited by:  Papers (5)
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    Freely Available from IEEE
  • [Back cover]

    Publication Year: 1981 , Page(s): 0
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    Freely Available from IEEE
  • An Efficient Selective-Repeat ARQ Scheme for Satellite Channels and Its Throughput Analysis

    Publication Year: 1981 , Page(s): 353 - 363
    Cited by:  Papers (46)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (888 KB)  

    In this paper, we investigate a selective-repeat ARQ scheme which operates with a finite receiver buffer and a finite range of sequence numbers. The throughput performance of the proposed scheme is analyzed and simulated based on the assumption that the channel errors are randomly distributed and the return channel is noiseless. Both analytical and simulation results show that it significantly outperforms the go-back- N ARQ scheme, particularly for channels with large roundtrip delay and high data rate. It provides high throughput efficiency over a wide range of bit error rates. The throughput remains in a usable range even for very high error rate conditions. The proposed scheme is capable of handling data and/or acknowledgment loss. Furthermore, when buffer overflow occurs at the receiver, the transmitter is capable of detecting it and backs up to the proper location of the input queue to retransmit the correct data blocks. View full abstract»

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  • Quadrature Overlapped Raised-Cosine Modulation

    Publication Year: 1981 , Page(s): 237 - 249
    Cited by:  Papers (35)  |  Patents (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    A variation of an old but neglected pulse shaping technique, raised-cosine, is investigated. By overlapping raised-cosine pulses in each of two data streams and then by quadrature combining them, a simple QPSK/MSK type modulation results. This quadrature overlapped raised-cosine (QORC) modulation exhibits a hybrid structure of QPSK and MSK modulations. The power spectral density of QORC is shown to take on the form of the product of the power spectral densities of MSK and QPSK. The obvious consequences are that the power spectral density main lobe retains the width of the spectral density main lobe of QPSK, but the sidelobes drop off much faster (1/f^{6}) . A simple QORC modulator can be implemented similar to an MSK modulator. Several correlation type receivers are investigated and their performances calculated. Computer simulation results are used to compare end-to-end system performance of QORC and staggered QORC (SQORC) with MSK, QPSK, and staggered QPSK (SQPSK) for both linear and nonlinear satellite channels. The performance of QORC and SQORC compares very favorably with QPSK, SQPSK, and MSK. QORC performs particularly well in the presence of a nonlinear channel. The effect of phase equalization of the channel filter was investigated with outstanding performance improvement. The simulation results show that sidelobe regeneration caused by the channel nonlinearity is much less for SQORC than it is for the other modulation formats considered. View full abstract»

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  • Demodulation and Carrier Synchronization of Multi-h Phase Codes

    Publication Year: 1981 , Page(s): 257 - 266
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (880 KB)  

    Multi- h phase coding is a bandwidth-efficient modulation which offers substantial performance improvement over conventional digital modulations with little or no bandwidth expansion. This paper examines the demodulation of the multi- h signals, and in particular examines the behavior of a decision-directed carrier loop which utilizes the Viterbi algorithm decoder in the calculation of the loop error signal. Both analytic and simulation results are presented and the agreement between the two is shown to be very close. View full abstract»

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  • Spectrally Efficient Communication via Fading Channels Using Coded Multilevel DPSK

    Publication Year: 1981 , Page(s): 276 - 284
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    This paper investigates the use of multilevel differential phase-shift keying with forward error-correcting coding as a technique for achieving limited bandwidth, yet reliable communication over a class of fading channels. Error rate bounds based on the cutoff rate are computed to show that multilevel modulation can be used to allow significant coding gains, while maintaining or reducing the bandwidth of the transmitted signal. View full abstract»

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  • A Method for Transponder Capacity and Link Performance Optimization in Preassigned Multilevel SCPC Systems

    Publication Year: 1981 , Page(s): 314 - 328
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1152 KB)  

    An investigation of ways to improve the capacity in a dedicated SCPC transponder has resulted in the development of a method for optimizing the transponder capacity and link performance in preassigned multilevel SCPC systems. The main approach is to form different groups of carriers based on the traffic requirement, and on typical characteristics of the link destinations such as variations in the satellite e.i.r.p. and downlink path loss, and differences in the receive earth station antenna size. The Fletcher-Powell optimization technique is used to determine the set of optimum carrier levels at the transponder TWTA input. Application of the method to a number of preassigned multilevel frequency plans in a global transponder environment clearly indicates that the total carrier-to-noise ratios for all the links can be optimized at any specified CNR value, and that the optimized capacities are substantially higher than that of the basic two-level system. The implementation of multilevel plans is fairly simple if all downlink carrier levels can be monitored at some reference station in the SCPC network to reasonably control the uplink e.i.r.p. levels. View full abstract»

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  • Teletraffic Analysis for Single-Cell Mobile Radio Telephone Systems

    Publication Year: 1981 , Page(s): 298 - 304
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    Formulas are derived for the congestion in single-cell mobile radio systems in which there are both land-to-mobile and mobile-to-mobile calls and in which mobile-to-mobile calls go via the base station. Two approaches are used. The first yields modified forms of the familiar Erlang and Engset formulas. The second gives more complicated but more accurate formulas. The results of computer simulations to establish the accuracy of the formulas are described. View full abstract»

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  • A Simulation Study of Two Bandwidth-Efficient Modulation Techniques

    Publication Year: 1981 , Page(s): 267 - 275
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB)  

    Signal space coded signaling systems have the potential of achieving significant error-rate improvement without the bandwidth expansion normally encountered when error-correcting codes are used. This paper investigates two such systems by means of computer simulation. A band-limited, nonlinear channel is assumed and both systems exhibit performance improvenment compared to uncoded systems. View full abstract»

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  • Performance of Offset Quadriphase Spread-Spectrum Multiple-Access Communications

    Publication Year: 1981 , Page(s): 305 - 314
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    New analytical results are obtained on the performance of quadriphase spread-spectrum multiple-access communications. The primary performance parameter considered is the signal-to-noise ratio at the receiver output. This parameter includes the effects of multiple-access interference and channel noise, and it has been shown to give a reliable estimate of the average probability of error. View full abstract»

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  • More on the Multipath Fading Channel Model

    Publication Year: 1981 , Page(s): 346 - 352
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    Selective fading due to muitipath on a typical narrowband line-of-sight microwave radio path is represented with a simplified three-ray model. This model provides a satisfactory description of the frequency transfer characteristics of almost all fades observed during three separate propagation experiments. Data were obtained for a 30 MHz bandwidth at 6 GHz using both a standard horn reflector and a parabolic dish, and for a 20 MHz bandwidth at 4 GHz using the horn. The statistics of the parameters of the model were found to be substantially the same for all three cases. The incidence of selective fading scales, within a factor of two, with the incidence of fading at a single frequency, for 1-month observation intervals. View full abstract»

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  • New LSI Digital Service Units and Office Channel Units Used for NTT Digital Data Networks

    Publication Year: 1981 , Page(s): 365 - 370
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    Digital data services have been offered by NTT since 1978. The largest part of the entire digital data network cost is attributable to subscriber loop transmission that includes digital service units (DSU's) and office channel units (OCU's). Therefore, it is important to reduce DSU and OCU costs for economizing on digital data services. In order to achieve this purpose, new LSI DSU and OCU have been developed. The LSI is used for a digital signal processing unit, which occupies most of the equipment cost and size. The LSI can be applied to all bearer rates from 3.2 to 64 kbits/s, for NTT digital data services (leased circuit service, circuit switched service and packet switched service). It is highly significant that adoption of the LSI in DSU and OCU makes the following estimations feasible: 1) About 30 to 40 percent Cost reduction 2) About 25 percent size reduction 3) About 30 to 50 percent failure rate reduction 4) About 50 to 70 percent power consumption reduction. Summary The most expensive part of the network that carries NTT Digital Data Services is the subscriber loop transmission system, which includes DSU and OCU. This paper describes the design philosophy for introducing LSI technology in the DSU and OCU for cost reduction. Then the function, construction and evaluation are presented for the newly developed LSI DSU and OCU, based on the above design concept. View full abstract»

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  • Continuous Phase Modulation--Part II: Partial Response Signaling

    Publication Year: 1981 , Page(s): 210 - 225
    Cited by:  Patents (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1304 KB)  

    An analysis of constant envelope digital partial response continuous Phase modulation (CPM) systems is reported. Coherent detection is assumed and the channel is Gaussian. The receiver observes the received signal over more than one symbol interval to make use of the correlative properties of the transmitted signal. The Systems are M -ary, and baseband pulse shaping over several symbol intervals is considered. An optimum receiver based on the Viterbi algorithm is presented. Constant envelope digital modulation schemes with excellent spectral tail properties are given. The spectra have extremely low sidelobes. It is concluded that partial response CPM systems have spectrum compaction properties. Furthermore, at equal or even smaller bandwidth than minimum shift keying (MSK), a considerable gain in transmitter power can be obtained. This gain increases with M . Receiver and transmitter configurations are presented. View full abstract»

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  • An Evaluation of Local Path ID Swapping in Computer Networks

    Publication Year: 1981 , Page(s): 329 - 336
    Cited by:  Papers (4)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB)  

    This paper analyzes a method for identifying end-to-end connections in computer networks which is designed to provide reductions in the sizes of the packet headers and routing tables stored in the nodes. The method, known as Local Path ID Swapping, uses a shortened connection identifier, called the LPID, in the message headers and routing tables. In general, the LPID field is swapped in the message header from node to node along the path of the route. Some analytical results are presented for evaluating the important tradeoffs involved in LPID swapping. Most notable is the tradeoff between the size of the LPID field and the number of connections which can be defined in the network. View full abstract»

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  • Correlative Phase Shift Keying--A Class of Constant Envelope Modulation Techniques

    Publication Year: 1981 , Page(s): 226 - 236
    Cited by:  Papers (28)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (968 KB)  

    Correlative phase shift keying (CORPSK) is described. CORPSK is a constant envelope modulation technique with smooth transitions between fixed phase positions with successive transitions correlated. A number of CORPSK members for 2 and 4 input levels are analyzed, including tamed frequency modulation (TFM). Main lobe bandwidth is the same or less than in other constant envelope modulation techniques such as MSK, QPSK, and CPFSK, but the out-of-band radiation is much lower. Carrier extraction can be realized with simple techniques, so that coherent detection with optimum receiver performance is practically feasible. Simulation results are presented for coherent as well as noncoherent detection. A power efficiency 2 dB better than four MSK and DQPSK can be obtained for CORPSK with no more than for phase positions. A wide variety of modulations exists within the CORPSK class, with ample opportunity for tradeoffs between power, bandwidth, and complexity. Practical results for TFM are reported. View full abstract»

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  • Continuous Phase Modulation--Part I: Full Response Signaling

    Publication Year: 1981 , Page(s): 196 - 209
    Cited by:  Papers (298)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1008 KB)  

    The continuous phase modulation (CPM) signaling scheme has gained interest in recent years because of its attractive spectral properties. Data symbol pulse shaping has previously been studied with regard to spectra, for binary data and modulation index 0.5. In this paper these results have been extended to the M -ary case, where the pulse shaping is over a one symbol interval, the so-called full response systems. Results are given for modulation indexes of practical interest, concerning both performance and spectrum. Comparisons are made with minimum shift keying (MSK) and systems have been found which are significantly better in E_{b}/N_{0} for a large signal-to-noise ratio (SNR) without expanded bandwidth. Schemes with the same bit error probability as MSK but with considerably smaller bandwidth have also been found. Significant improvement in both power and bandwidth are obtained by increasing the number of levels M from 2 to 4. View full abstract»

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  • Design and Performance of a DSI Terminal for Domestic Applications

    Publication Year: 1981 , Page(s): 337 - 345
    Cited by:  Papers (5)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (984 KB)  

    The development of a microprocessor-controlled 96/48 DSI terminal is described. The terminal is intended for domestic use, and is designed so as to maximize compatibility with existing digital carrier systems, it merges four T1 signals into two T1 compatible bit streams for transmission. The terminal is given sufficient excess capacity to accommodate voiceband data, while retaining toll-grade transmission quality for speech. Implementation approaches and considerations in both calculated and measured system characteristics are described. View full abstract»

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  • The Effect of Phase Error on DPSK Error Probability

    Publication Year: 1981 , Page(s): 364 - 365
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    Expressions are found for the effect of an error in the delay of the preceding signal, which provides the reference phase for the decoding of the present signal in differential phase-shift-keying reception. The signal-to-noise ratio is allowed to be different for the two signals that are compared by the receiver's phase detector. The results are applicable to both binary and quaternary DPSK. In addition, an approximation is obtained for the error probability when the two Signal-to-noise ratios are equal to the same large value. View full abstract»

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  • Power Spectra of Multi-h Phase Codes

    Publication Year: 1981 , Page(s): 250 - 256
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    A procedure is presented for calculating the power spectrum of the class of digital continuous-phase signals known as multi- h phase codes. These signals have been shown to have attractive power advantages over other uncoded digital schemes such as QPSK, and represent a bandwidth-efficient alternative to other coding. techniques. The method is general, handling M -ary signaling, various frequency pulse shapes, and arbitrary sets of modulation indices. Numerical results are shown for several specific codes. In addition, the issue of spectral lines is resolved, and simple spectral approximations are developed. View full abstract»

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  • Power-Bandwidth Performance of Smoothed Phase Modulation Codes

    Publication Year: 1981 , Page(s): 187 - 195
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (992 KB)  

    Constant envelope phase varying sinusoids of the form \sqrt {2E/T} \cos(\omega _{c}t + \phi(t)) are studied, in which the phase function \phi(t) follows some coded pattern in response to data. Power and bandwidth performance are studied for such patterns. The patterns depend on a phase shaping function, a modulation index ( h ), and a sequence of M -ary underlying changes in phase which are chosen at random. A cutoff rate-like parameter R0is computed, which guarantees existence of codes at all rates R < R_{0} bits/ T -interval whose error performance varies as exp [-N(R_{0} - R)] , where N is the code word length in T -intervals. Plots of R0are given as a function of interval energy E , the shaping function h and M . Extensive spectral calculations give the spectra of these phased sinusoids, and their performance is plotted in the power-bandwidth plane. The results give strong evidence that phase codes can approximate any power-bandwidth combination consistent with Shannon's Gaussian channel capacity, and that linear channels are not required for narrow-band transmission. View full abstract»

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  • Cochannel and Intersymbol Interference in Quadrature-Carrier Modulation Systems

    Publication Year: 1981 , Page(s): 285 - 297
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (960 KB)  

    A method is presented for determining the performance of a quadrature-carrier modulation system in terms of probability of error in the presence of additive white Gaussian noise, intersymbol interference, and cochannel interference. This method has been applied to determine the error rate of several quadrature-carrier modulation systems using Butterworth receiving filters of different orders. It has been foand that among the different quadrature-carrier modulation systems studied, sinusoidal frequency-shift keying seems to exhibit the best overall performance in a cochannel and intersymbol interference environment. These results are shown through a number of performance curves that provide useful data for the systems designer. 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.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia