Short Code

The short code is a pair of period 2¹⁵ sequences that are used for spreading the CDMA Forward Channel. They are also used in conjunction with the Long Code for spreading the CDMA Reverse Channel. They are both derived from period 2¹⁵ -1 LFSR sequences, augmented with an extra zero bit to bring the length to an even power of two.

The short code LFSR tap polynomials are, for the I-sequence

(1) and for the Q-sequence . (2)
The extra zero bit is inserted in each sequence immediately after the occurrence of 14 consecutive zeros from the generator register. This occurs once per period.

At the spreading rate of 1.2288 MHz the period of the short code is 80/3 = 26.666... ms.

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