This paper reviews earlier studies on superluminal wave propagation in anomalously dispersive media that have been carried out in the electronic, microwave, and optical regimes. Those studies are relevant to observation of modulated Gaussian pulses transmitted through various media at speeds apparently faster than c without distortion. This paper also presents the condition for superluminal propagation that is established based on the magnitude-phase relation of a causal and minimum-phase filter. Since the condition is modeled on the basis of filter theory, it is applicable to all types of media. A terahertz experiment with a periodic bandgap structure is also included to illustrate superluminal propagation.

The paper presents schemes for rapid on-line error probability estimation of digital communications links. Several estimator structures are proposed based on the assumption of sample independence, including weighted least squares (WLS) and maximum likelihood (ML) forms. The continuous-form ML estimator is shown to lie on the Rao-Cramer bound, making it a most efficient estimator of probability of error. The design, performance, implementation complexity and behavior of these estimators is described for AWGN.>

The use of importance sampling techniques can substantially reduce the variance of probability of error estimates obtained by Monte Carlo type simulations of digital communication systems. However, the advantages of importance sampling diminish as the memory length of the system becomes greater. This paper presents a modified importance sampling method which achieves substantial variance reduction for systems with memory.

An analysis of the exact delay of a TDMA or a loop communication system with a contiguous output and a Poisson message arrival process is presented. The nonlinear relationship of a contiguous output with arbitrary arrival process can be expressed by an infinite series. In the case of a Poisson message arrival process, the series can be summed to a closed form. The derived result, which is validated by simulation, is a vast improvement over the previously used approximate model of multiple frames with single output.

This paper identifies the characteristics of a point-topoint demand-assignment satellite-switched spot-beam antenna communication network for integrated data voice traffic. The described protocol is known as space-division multiple-access (SDMA) which uses an on-board central traffic controller, a fixed-assignment timedivision multiple-access (TDMA) protocol for reservations, and a rigid frame structure with separate data and voice subframes. Message and circuit switching are utilized for data and voice traffic, respectively. Synchronization is maintained by a looped-back reservation burst. A detailed delay analysis of data and voice traffic is presented for an arbitrary compound arrival process. A new method for the calculation of the data reservation and scheduling delays is derived. A comparison of the performance of the SDMA protocol to other protocols is shown. This paper demonstrates the feasibility and illustrates the design of the SDMA protocol.

Intermittent data transmission, that is, sending data only when the signal strength is above a desired threshold, has been shown to be extremely effective at combatting the effects of signal fading. However, such a system must usually interface with a uniform data source and sink by the use of finite buffers. When the buffer fills, transmission must occur during bad signal conditions and when it empties, no transmission can occur. The effect of such a finite buffer on system performance is derived and these theoretical results are validated using computer simulation. Finally, adaptive methods to improve performance are investigated and two areas of application of an intermittent System are examined.