Derek Andrew

A Transmission Scheme for Integrated Services on Broad-Band Internal Private Business Networks

Internal business networks are expected to present an economic area of application for broad-band communications. A star network with switches optimized for various services is envisaged. An asynchronous switch for video in square wave frequency modulation (SWFM) format can provide a practical solution for full bandwidth switched video services. A transmission scheme is described which combines a SWFM video service together with synchronous PCM data and voice services, asynchronous data up to 9.6 kbauds and network clocks at both 2 MHz and 160 kHz for ISDN, so that all services destined for one terminal site may be transmitted in binary format on cable or fiber. An experimental link is described which provides up to 10 Mbit/s data capacity together with the video service. The hardware is constructed with 74HC family CMOS. An analysis of the effects of data modulation on video quality is given. Measurements of video S/N and distortion are reported. Measured bit-error rate in a 64 kbit/s data channel is reported. The measurements relate to a coaxial cable link with link lengths from 200 to 400 meters.