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Communications, IEEE Transactions on

Issue 7 • Date July 1990

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Displaying Results 1 - 25 of 26
  • Comments on "Exact analysis of asymmetric polling systems with single buffers

    Publication Year: 1990 , Page(s): 944 - 946
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    In the above-titled paper by Takine et al. (see ibid., vol.COM-36, no.10, p.1119-27, Oct. 1988) an exact analysis of a nonsymmetric polling system with single message buffers was reported. The commenters provide an alternate method for analyzing the exact mean waiting times of the individual stations in the same system by extending an exact analysis for the two-station case. Some corrections to the numerical results provided in the paper are made.<> View full abstract»

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  • The effect of prioritization on the behavior of a concentrator under an accept, otherwise reject strategy

    Publication Year: 1990 , Page(s): 1031 - 1039
    Cited by:  Papers (2)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (580 KB)  

    The effect of prioritization on the behavior of a concentrator which accepts packetized messages and receives a service from a transmitter operating in synchronous mode is studied. The messages arrive according to a Poisson process, and are divided into two classes: ordinary and priority. A buffer is shared between ordinary and priority packets. Two buffer-sharing strategies are considered: sharing with maximal length, and complete sharing subject to purgation. Upon the arrival of a message, if its size exceeds the remaining buffer space, then the message will be completely rejected. For each buffer-sharing strategy, results obtained include state transition probability, state probability, blocking probability, throughput, and delay. Computer simulations are used to verify the validity of results View full abstract»

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  • Evaluation of a partial-band jammer with Gaussian-shaped spectrum against FH/MFSK

    Publication Year: 1990 , Page(s): 1045 - 1049
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    Since a rectangular spectrum is unrealizable, more realistic spectra such as those where a jammer uses a bandpass filter before amplifying the jamming noise are considered. A Gaussian-shaped filter is used to represent a class of bandpass filters. This is a more realistic shape than the ideal rectangular shape. In addition, it can be easily analyzed by a reasonable approximation, i.e. a Gaussian-shaped spectrum that is constant over each hopped M-ary signaling band. Numerical results indicate that such a Gaussian-shaped partial-band noise jammer has nearly the same effects as an ideal rectangular-shaped partial-band noise jammer with an equivalent bandwidth View full abstract»

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  • Probability of bit error for MPSK modulation with diversity reception in Rayleigh fading and log-normal shadowing channel

    Publication Year: 1990 , Page(s): 933 - 937
    Cited by:  Papers (8)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    In an additive white Gaussian noise channel subject to Rayleigh fading and log-normal shadowing, consideration is given to diversity reception with K-port macroscopic selection and L-branch microscopic maximal-ratio combining, and analytical expressions are derived for upper and lower bounds on the bit error probabilities for BPSK, QPSK, 8-PSK, and 16-PSK modulations. The derived expressions can be evaluated at any location in the serving cell. Error-probability can be calculated by averaging over all possible locations within the serving cell. By evaluating these bounds, numerical results for the following cases are presented: without diversity reception, microdiversity combining, macrodiversity selection, and simultaneous use of macrodiversity selection and microdiversity combining. For symmetrical arrangement of macrodiversity ports against the lognormal shadowing, error probability at the equidistant point gives upper bounds on the error probabilities for most of the area in the serving cell. Error probability at the equidistant point is a good estimate of the error probability obtained by averaging over all possible locations in the cell View full abstract»

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  • Capacity of frequency-hop spread-spectrum multiple-access communication systems

    Publication Year: 1990 , Page(s): 1050 - 1059
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    The information theoretic capacity is considered. In order to account for independent encoding and decoding and private (to the sender and receiver) hopping patterns, an interference channel model is adopted with K sender-receiver pairs with the ith receiver only interested in the message transmitted by the ith sender. Both synchronous and asynchronous hopping patterns are investigated. Although the channel exhibits memory in the latter case, it is possible to compute the capacity region. The asymptotic normalized sum capacity is also computed View full abstract»

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  • Practical aspects of DFT-based frequency division multiplexing for data transmission

    Publication Year: 1990 , Page(s): 929 - 932
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    A practical implementation of digital frequency division multiplexing is presented. The design goals are the use of very few modulation schemes (two or three), uniform reliability across the subchannels, and the avoidance of peak power violation. The FTDM (Fourier transform division multiplexing) method is used to design signals for transmission. Data are encoded in the frequency domain, Fourier transformed to yield a real sequence, and a signal is transmitted whose sampled values, when inverse Fourier transformed, yield the original code. Spectral characteristics for the code are easily obtained because it is designed in the frequency domain View full abstract»

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  • Error rates for narrow-band digital FM with discriminator detection in mobile radio systems

    Publication Year: 1990 , Page(s): 999 - 1005
    Cited by:  Papers (20)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    Error rates for a narrowband digital FM system with discriminator detection in a land mobile radio channel characterized by fading and Doppler frequency shift are obtained using a new analytical method. The fading rate is assumed to be much slower than the bit rate so that signal distortion through a narrow bandpass filter can be analyzed via a quasistatic approach. An experiment was conducted using a Rayleigh fading simulator, and the error rate measurements are shown to agree well with the calculated results, except at high SNR (signal-to-noise ratio) where an irreducible error rate was observed View full abstract»

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  • Optimal trunk reservation for a group with multislot traffic streams

    Publication Year: 1990 , Page(s): 1078 - 1084
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    The problem of finding an optimal control by trunk reservation which maximizes the trunk utilization under parcel blocking constraints is studied, and two different linear programming formulations for this optimization problem are proposed. One is based on the proposed conversion of the conventional nonlinear programming formulation to a linear programming one, and the other is based on the theory of the Markov decision process. A property of the optimal control parameter values is discussed theoretically, and the improvement of trunk utilization achieved by applying the optimal control is evaluated numerically. Moreover, a suboptimal control which observes only the number of busy trunks is compared with the optimal one in traffic characteristics including peakedness of parcel overflows of the controlled trunk group View full abstract»

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  • Nonlinear techniques for interference suppression in spread-spectrum systems

    Publication Year: 1990 , Page(s): 1060 - 1065
    Cited by:  Papers (106)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    The binary nature of direct-sequence signals is exploited to obtain nonlinear filters that outperform the linear filters hitherto used for this purpose. The case of a Gaussian interferer with known autoregressive parameters is considered. Using simulations, it is shown that an approximate conditional mean (ACM) filter of the Masreliez type performs significantly better than the optimum linear (Kalman-Bucy) filter. For the case of interferers with unknown parameters, the nature of the nonlinearity in the ACM filter is used to obtain an adaptive filtering algorithm that is identical to the linear transversal filter except that the previous prediction errors are transformed nonlinearly before being incorporated into the linear prediction. Two versions of this filter are considered: one in which the filter coefficients are updated using the Widrow LMS algorithm, and another in which the coefficients are updated using an approximate gradient algorithm. Simulations indicate that the nonlinear filter with LMS updates performs substantially better than the linear filter for both narrowband Gaussian and single-tone interferers, whereas the gradient algorithm gives slightly better performance for Gaussian interferers but is rather ineffective in suppressing a sinusoidal interferer View full abstract»

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  • Theory of FM clicks with Brownian motion phase noise

    Publication Year: 1990 , Page(s): 1022 - 1030
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    Lasers that are used for coherent optical communication exhibit phase instabilities which can be modeled as a Brownian motion. The effect that such a disturbance has on limiter-discriminator detection of FM signals received in additive Gaussian noise is investigated. Although a new theory must be developed to calculate FM click rates (and prove them finite), no effects are found which would preclude the use of such a detector with Brownian phase noise. In particular, for binary FM transmission at rate R, discriminator detection will result in 1 dB of degradation or less if Bpn/R<0.002, Bpn being the linewidth of the unmodulated carrier View full abstract»

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  • A practical adaptive image compression technique using visual criteria for still-picture transmission with electronic mail

    Publication Year: 1990 , Page(s): 947 - 949
    Cited by:  Papers (1)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    An efficient image compression/decompression technique for complex scenes is presented. An image is first decorrelated by a full two-dimensional DCT (discrete cosine transform). The resulting coefficient map is weighted using properties of the human visual system and finally encoded with a novel multiresolution encoder. The result is converted into printable ASCII for transmission by electronic mail View full abstract»

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  • The performance of rate-compatible punctured convolutional codes for digital mobile radio

    Publication Year: 1990 , Page(s): 966 - 980
    Cited by:  Papers (90)  |  Patents (60)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1320 KB)  

    The unequal error protection capabilities of convolutional codes belonging to the family of rate-compatible punctured convolutional codes (RCPC codes) are studied. The performance of these codes is analyzed and simulated for the first fading Rice and Rayleigh channels with differentially coherent four-phase modulation (4-DPSK). To mitigate the effect of fading, interleavers are designed for these unequal error protection codes, with the interleaving performed over one or two blocks of 256 channel bits. These codes are decoded by means of the Viterbi algorithm using both soft symbol decisions and channel state information. For reference, the performance of these codes on a Gaussian channel with coherent binary phase-shift keying (2-CPSK) is presented. A number of examples are provided to show that it is possible to accommodate widely different error protection levels within short information blocks. Unequal error protection codes for a subband speech coder are studied in detail. A detailed study of the effect of the code and channel parameters such as the encoder memory, the code rate, interleaver depth, fading bandwidth, and the contrasting performance of hard and soft decisions on the received symbols is provided View full abstract»

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  • Multiple-access capability of frequency-hopped spread-spectrum revisited: an analysis of the effect of unequal power levels

    Publication Year: 1990 , Page(s): 1066 - 1077
    Cited by:  Papers (55)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (980 KB)  

    A method for the evaluation of the probability of error of uncoded asynchronous frequency-hopped spread-spectrum multiple-access communications is presented. For systems with binary FSK modulation this method provides an accurate approximation and a tight upper bound to the bit error probability; for systems with M-ary FSK modulation, it provides tight upper bounds to the symbol error probability. The method enables the computationally efficient averaging of the error probability with respect to the delays, phase angles, and data streams of the different users. It relies on the integration of the product of the characteristic function of the envelope of the branch of the BFSK demodulator, which carries the desired signal, and of the derivative of the characteristic function of the envelope of the other branch. For sufficient frequency separation between the BFSK tones, the method can achieve any desirable accuracy. Moreover, the computational effort required for its evaluation grows linearly with the number of interfering users. In the M-ary case, tight upper bounds based on the union bound and the results of the binary case are derived. The method allows the effect of unequal power levels on other-user interference in FH/SSMA systems to be quantified accurately for the first time. The results indicate that the FH/SSMA systems suffer from the near-far problem, although less seriously than direct-sequence SSMA systems View full abstract»

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  • Direct-sequence spread-spectrum parallel acquisition in a fading mobile channel

    Publication Year: 1990 , Page(s): 992 - 998
    Cited by:  Papers (104)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    A parallel acquisition scheme for direct-sequence spread-spectrum systems is proposed, and its mean acquisition time performance is analyzed in both nonfading and Rayleigh-fading environments. An expression for the mean acquisition time is derived in terms of the probabilities of detection, missing, and false alarm. These parameters are first analyzed for a typical AWGN (additive white Gaussian noise) channel, then the Rayleigh-fading channel encountered in a typical UHF or microwave land mobile radio channel is studied. The channel is assumed frequency nonselective, and the effect of data modulation and code Doppler is not considered. The performance of the parallel system is compared to the corresponding serial system, and it is shown that a significant improvement can be achieved View full abstract»

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  • Performance analysis of a noncoherently combined large aperture optical heterodyne receiver

    Publication Year: 1990 , Page(s): 1013 - 1021
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    The performance of a noncoherently combined, multiple-mirror heterodyne receiver is analyzed. In the absence of atmospheric turbulence, the performance of the noncoherently combined receiver is shown to be inferior to that of a monolithic, diffraction-limited receiver with equivalent aperture area. when atmospheric turbulence is taken into consideration, however, the efficiency of a monolithic aperture heterodyne receiver, is limited by the phase coherence length of the atmosphere, and generally does not improve with increasing aperture size. In contrast, the performance of a noncoherently combined system improves with an increasing number of receivers. Consequently, given a fixed collecting area, the noncoherently combined system can offer a superior performance. The performance of the noncoherently combined heterodyne receiver is studied by analyzing the combining loss of the receiver SNR (signal-to-noise ratio). It is shown that, given a constant collecting area, the performance of the combined receiver is optimized when the diameter of each of the individual receivers is on the order of the phase coherence length r0 of the atmospheric turbulence View full abstract»

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  • A modular architecture for very large packet switches

    Publication Year: 1990 , Page(s): 1097 - 1106
    Cited by:  Papers (54)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (808 KB)  

    Switch modules, the building blocks of this system, are independently operated packet switches. Each module consists of a Batcher sorting network, a stack of binary trees, and a bundle of banyan networks. The modular architecture is a unification of the Batcher-banyan switch and the knockout switch, and can be physically realized as an array of three-dimensional parallel processors. Switch modules are interconnected only at the outputs by multiplexers. The partitioned switch fabric provides a flexible distributed architecture, which is the key to simplify the operation and maintenance of the whole switching system. The modularity implies less stringent synchronization requirements and makes higher-speed implementation possible. The proposed modular switch is intended to meet the needs of broadband telephone offices of all sizes. It is estimated that a modular switch with terabit capacity can be built using current VLSI technologies View full abstract»

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  • Human visual weighted progressive image transmission

    Publication Year: 1990 , Page(s): 1040 - 1044
    Cited by:  Papers (53)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    A progressive image transmission scheme which combines transform coding with the human visual system (HVS) model is developed. The adaptive transform coding of W.H. Chen and C.H. Smith (1977) is utilized to classify an image into four equally populated subblocks based on their AC energies. The modulation transfer function (MTF) of the HVS model is obtained experimentally, based on processing a number of test images. A simplified technique for incorporating the MTF into the discrete cosine transform (DCT) domain is utilized. In the hierarchical image buildup, the image is first reconstructed from the DC coefficients of all subblocks. Further transmission hierarchy of transform coefficients and consequent image buildup are dependent on their HVS weighted variances. The HVS weighted reconstructed images are compared to the ones without any weighting at several stages. The HVS weighted progressive image transmission results in perceptually higher quality images compared to the unweighted scheme View full abstract»

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  • Interference faults testing for time switches

    Publication Year: 1990 , Page(s): 954 - 958
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    A detection scheme for coupling faults for integrated digital time-division switches is proposed. It is shown that a low overhead is necessary to improve fault detectability. Based on the proposed augmentation of a standard time switch, a new test procedure that possesses the following properties is developed: it guarantees a detection of all possible coupling faults in both data and control memory, and the number of tests is minimal View full abstract»

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  • Optimal partial decision combining in diversity systems

    Publication Year: 1990 , Page(s): 981 - 991
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    The optimal partial decision combiner is derived, and its performance is analyzed and compared to majority voting and selection diversity using binary noncoherent frequency-shift keying on a Rayleigh-faded additive white Gaussian noise channel. The degradation in the probability of bit error is evaluated when the channel state estimate is imperfect due to parameter quantization, AWGN, and cochannel interference. It is demonstrated that the optimal partial decision combiner can provide a simple means for improving performance on channels with limited cochannel interference View full abstract»

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  • Cut-through bridging for CSMA/CD local area networks

    Publication Year: 1990 , Page(s): 938 - 942
    Cited by:  Papers (6)  |  Patents (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    A novel bridging architecture, called a cut-through bridge, which can be used to interconnect existing carrier-sense multiple access with collision detection (CSMA/CD) LANs is proposed. This bridge uses the cut-through switching concept. After providing a design of this bridge, the authors examine its performance via a detailed simulation model. They demonstrate the performance enhancement achievable by the cut-through bridge over a normal bridge, namely lower average frame delay while attaining the same maximum throughput as the latter. Since the cut-through bridge can be readily used to replace passive repeaters while achieving superior performance, it has promise for immediate application in existing CSMA/CD LANs View full abstract»

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  • The cross-search algorithm for motion estimation [image coding]

    Publication Year: 1990 , Page(s): 950 - 953
    Cited by:  Papers (211)  |  Patents (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    A fast block-matching algorithm for motion estimation is presented. It is based on a logarithmic step where, in each search step, only four locations are tested. For a motion displacement of w pels/frame, this technique requires 5+4 log2w computations to locate the best match. Using sequences of CIF standard pictures, the interframe motion compensated prediction error with this technique is compared to the other fast methods. The computational complexity of this algorithm is also compared against those methods View full abstract»

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  • Phase error dynamics of a first-order phase locked loop in the presence of cochannel tone interference and additive noise

    Publication Year: 1990 , Page(s): 962 - 965
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    An alternative technique of evaluating the probability density function (PDF) of the loop-phase error of a first-order phase-locked loop in the face of a noisy signal accompanied by a cochannel tone interference, using the joint PDF of the resultant signal amplitude and phase, is presented. The numerical computations show that the results obtained are equivalent to those obtained elsewhere View full abstract»

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  • Performance of the timed token scheme in MAP

    Publication Year: 1990 , Page(s): 1006 - 1012
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    Two new analytic approximations are given for the mean delay in the timed token bus network specified in MAP (manufacturing automation protocol). Each station on the network has two kinds of timer for controlling the maximum amount of time for data transfer before giving up the token. High-priority stations would set large values in the token holding timer (THT) and transmit until the timer expires. Low-priority stations compare the elapsed time since the last token arrival (measured cycle time) to the token rotation timer (TRT) setting, and transmit only for the time left in the timer. The first approximation, based on Fuhrmann's bound for the limited-k service discipline, is for the symmetric case where all the stations have the same traffic load and the identical THT or TRT settings. The approximation has been compared to simulation results, and found to be quite accurate for a representation factory network, with THT or TRT set at two and five times the average total walk time. The second approximation is for the asymmetric case where there is one saturated low-priority (limited-TRT) station, and the rest of the stations in the network have high priority with limited-THT service. These two formulas will be useful in the planning and operation of MAP networks by providing guidance in the choice of timer settings for meeting different priority service requirements View full abstract»

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  • Nonuniform traffic analysis on a nonblocking space-division packet switch

    Publication Year: 1990 , Page(s): 1085 - 1096
    Cited by:  Papers (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    The nonuniform traffic performance on a nonblocking space division packet switch is studied. When an output link is simultaneously contended by multiple input packets, only one can succeed, and the rest will be buffered in the queues associated with each input link. given the condition that the traffic on each output is not dominated by individual inputs, this study indicates that the output contention involved by packets at the head of input queues can be viewed as an independent phase-type process for a sufficiently large size of the switch. Therefore, each input queue can be modeled by an independent Geom/PH/1 queueing process. Once the relative input traffic intensities and their output address assignment functions are defined, a general formulation can be developed for the maximum throughput of the switch in saturation. The result indicates under what condition the input queue will saturate. A general solution technique for the evaluation of the queue length distribution is proposed. The numerical study based on this analysis agrees well with simulation results View full abstract»

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  • The conservative code for bit synchronization

    Publication Year: 1990 , Page(s): 1107 - 1113
    Cited by:  Papers (8)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    A novel coding scheme for bit synchronization, the conservative code, is presented and analyzed. Each codeword is characterized by having a predefined number of transitions, with a known delimiting transition at the end, i.e. the number of transitions is conserved. As a result, it is possible to decode the incoming serial bit-stream without explicitly recovering the receiving clock with a phase-locked loop. Thus, it is possible to receive messages from asynchronous sources without any training period. This code can be extremely useful in communication over a passive optical star. In the analysis, the efficiency or capacity of the code is computed with two additional constraints: limited run-length and balancing. It is shown that this coding scheme is efficient when both constraints are applied. The objective of this analysis is to show that the additional constraints imposed on the encoding do not cause a significant reduction in its efficiency. The design of a serial electronic interface is described. Its goal is to maximize the interface bandwidth (greater than 1/Gb/s with GaAs technology), which is usually the bottleneck of an optical communication system. It is achieved by reducing the critical timing path to one flipflop and one NOR gate, and by having a hierarchical interface design 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