The command post on the move

The author describes the operation at 24 Mb/s of a broadband code-division multiple-access (B-CDMA) system employing nonlinear codes for security. Users in this system can transmit toll quality voice using 32-kb/s adaptive delta modulation or data at rates up to T1. The antennas employed are omnidirectional, and the acquisition and tracking systems can follow Doppler shifts to 1 part in 10/sup 5/. Handoff from one base station to another occurs smoothly without loss of data. Experimental results are presented to verify theory. It is shown that such a system by virtue of its 48-MHz bandwidth and the low data rate has a processing gain of approximately 40 dB. Thus, the power spectral density of the transmitted signal is reduced by 40 dB compared to a narrowband transmission. As a result, B-CDMA is inherently LPI (low probability of interception).<
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