Qualcomm let many callers share one frequency by spreading each into a code

In 1985 Irwin Jacobs and a group of engineers founded Qualcomm with a contrarian idea: reuse space that the cellular world had been writing off. They believed a channel's real capacity came from interference, not from clocking users into distinct frequencies or slots.

Their technique, code division multiple access, spreads each caller's bits across one wide band using a pseudorandom code. The receiver inverts only its own code, which turns everyone else's transmission into a low-level floor of noise. Many callers share the same spectrum.

In the spring of 1989 Qualcomm and PacTel Cellular staged a live demonstration for fifty industry leaders. In July 1993 the Telecommunications Industry Association adopted CDMA as a standard, and the first commercial system went live in Hong Kong in 1995.

Separate users by code, not by frequency or time

A shared band with orthogonal codes uses spectrum that fixed-slot schemes waste at the guardbands.

Capacity interpolates as a signal-to-noise tradeoff, so it scales past a hard number of channels.

Spreading makes the signal robust to narrowband interference, improving voice and data quality.

When a scarce resource is carved up physically, adding users is zero-sum. Carve it up with mathematics, so the limit becomes an adjustable signal-to-noise bound, not fixed slots.

CDMA became the basis for IS-95 and the 3G family, licensing out of Qualcomm's patent pool to phone makers and carriers. The spread-spectrum design it proved out set up the cellular standard wars that followed.