A New Mixed Voice-Data Local Area Network

The various issues relating to the use of direct sequence (DS) spread spectrum (SS) modulation as access protocols for a local computer network are investigated. Voice and data messages having different traffic characteristics are packetized, the information bits DPSK modulated, after which spreading by the DS gives the waveform to be transmitted. Each node within the network will have a SS modem, to which all kinds of voice and data sources and different rates can be connected. Each node will be characterized by a certain DS code thus getting security as a fringe benefit. Except the code circuit, all SS modems will look the same, moreover all the DS signals transmitted will have the same spectral properties thus achieving uniformity and modularity of signals and equipments throughout the network. Among the performance criteria, we choose the signal to noise ratio SNR at the demodulator, the packet delay, the probability of correct packet detection, and the useful throughput. A new definition is suggested for the network efficiency and all performance criteria for the proposed network are compared to those of a classic FDMA/ALOHA type network under the same circumstances.