This panel presentation contains one full position paper on the user network interface in broadband ISDN, and four position summaries. Issues considered in the latter include: the impact of multimedia services, the effect of optical fiber transmission, the superiority of packet switching for diverse applications, and the potential unification of circuit-and packet-switching techniques.>

In broad-band communication networks, a number of services are simultaneously available to the subscriber. The issues of service integration and multiplexing techniques, and their impact on network topologies, are addressed in this paper. Alternative realizations of broadband networks, together with necessary electrical and optical components, are discussed. A comparison between the different alternatives is also made.

In this paper, new structures are proposed for the realization of two-dimensional (2-D) stable recursive filters. Such structures are derived from 1-D analog doubly-terminated LC ladder networks by first creating a suitable 2-D analog ladder structure using the method outlined in (1), and then utilizing the linear transformation technique to derive the corresponding 2-D structures. In doing so, the resulting structures are not only ensured to be recursively stable, but they also enjoy very low sensitivity to variations in multiplier coefficient values, and their round-off noise is expected to be low. The technique of linear transformations is applied to the design of low sensitivity active filter structures, and one particular scheme leading to an economical realization is outlined. Examples are included to illustrate the excellent low sensitivity of the derived structures.

A novel method is presented for the design of two-dimensional (2-D) recursive filters that are inherently stable, thereby avoiding computationally lengthy tests of stability. The new method is based on mapping the 1-D continuous complex frequency variable s by an appropriate function of the 2-D digital filter variables Z1and Z2. Thus, passive analog filters (Butterworth, Chebyshev or Cauer) may readily be transformed into the 2-D digital domain, preserving certain desirable aspects of the 1-D characteristics, as well as avoiding the cumbersome computations required to synthesize stable two-variable transfer functions. Some examples are presented to demonstrate the excellent response, e.g. circular symmetry, obtained using the new technique. The advantages of this approach over other methods suggested for stable 2-D recursive filter design, are briefly discussed.