Variable rate data are sent on the reverse CDMA channel. Code symbol repetition introduces redundancy when the data rate is less than 9600 bps. A data randomizer is used to transmit certain bits while turning the transmitter off at other times. When the data rate is 9600 bps, all interleaver output bits are transmitted. When the data rate is 4800 bps, half of the interleaver output bits are transmitted, and the mobile unit does not transmit 50% of the time, and so forth (see Table below)

Figure below illustrates the process under different data rates (E1A92). Data in each 20 ms frame are divided into sixteen power control groups, each with period 1.25 ms. Some power control groups are gated-on, while others are gated-off. The data burst randomizer ensures that every repeated code symbol is transmitted exactly once. During the gate-off process, the mobile station reduces its EIRP either by at least 20 dB with respect to the power of the most recent gated-on period, or to the transmitter noise floor, whichever is greater. This reduces interference to other mobile stations operating on the same reverse CDMA channel. The data burst randomizer generates a masking pattern of 'O's and '1's that randomly masks the redundant data generated by the code repetition process. A block of 14 bits taken from the long code determines the masking pattern. The last 14 hits of the long code used for spreading in the second to last power control group of the previous frame are used to determine the random mask for the gating. These 14 bits are denoted as

b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 b10 b11 b12 b13

where b0 represents the earliest bit, and b13 represents the latest bit. The data randomizer algorithm is as follows:

• If the user data rate is 9600 bps, transmission occurs on all sixteen power control groups.
• If the user data rate is 4800 bps, transmission occurs on eight power control groups given as

bo,2+b1, 4+b2, 6+b3, 8+b4, 10+b5,  l2+b6, l4+b7

• If the user data rate is 2400 bps, transmission occurs on four power control groups numbered
  1. b0 if b8=0, or 2+b1 if b8= 1
  2. 4+b2 if b9= 0, or 6+b3 if b9 = 1
  3. 8 + b4 lf b10= 0, or 10 + b5 if b10 = 1
  4. 12 + B6 if b11 = 0, or l4+b7 if b11 = 1
• If the user data rate is 1200 bps, transmission occurs on two power control groups numbered:
  1. b0 if (b8 = 1 and b12 = 0), or 2 + b1 if (b8 = 1 and b12 = 0),
     or 4 + b2 if(b9 = 0 and b12 = 1), or 6 + b3 if (b9 = 1 and b12 = 1);
  2. 8 + b4 if (b10 = 0 and B13 = 0), or 10 + b5 lf (b10 = 1 and b13 = 0)
     or 12 + b6 if(b11 = 0 and b13 = 1), or 14 + b7 if (b11 = 1 and b13 = 1)