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Broadband switching and transmission technologies are maturing rapidly, promising to make broadband ISDN (B-ISDN) possible and potentially economical in the near future. The diversity of possible B-ISDN services provides much impetus for the implementation of B-ISDN, but complicates the task of specifying network switching requirements. This paper examines a few representative services in order to generate a set of basis vectors in capability space. New services are then projected onto this basis; if a new service cannot be constructed from the basis vectors, other vectors are added to the basis set. B-ISDN architects can then specify switching requirements by selecting those capability basis vectors that are required for the services most in demand. For full motion entertainment video services, circuit switching capability at about 150 Mbit/s may be required, while selective broadcast and remote switching capabilities may reduce the cost of these services. For subvideo-rate services, new transfer mode (NTM) capability may be required to allow users the flexibility to allocate access channels dynamically on a per-call basis. Multiple connection (e.g., voice and video) and multiple party call capabilities may be required for many B-ISDN services, implying a need to extend the ISDN signaling protocol. The capability for the user to request network code conversion between different coding formats (e.g., NTSC or HDTV), and network compression of signals to reduce the cost of interoffice facilities, may also be required. Finally, fast call setup capability and high calling volume capabilities may be required, implying a need to distribute call processing functions over multiple processors in the central office.
Date of Publication: Oct 1987