Application: The reverse traffic channels carry the primary digital voice traffic at one of four bit rates which vary frame-to-frame according to the voice content detected by the Vocoder. During a 20-msec Vocoder frame, the Vocoder generates bits at the rates of 8600, 4000, 2000, and 800 bits/sec. To the full-rate frames at 8600 bits/sec, 12 Frame Quality Indictor (FQI) bits and 8 convolutional encoder bits are added. At 50 frames per second, the 12 FQI and 8 encoder bits represent bit rates of 600 and 400 bits/sec respectively. The resulting full-rate bit rate equals 8600+600+400 or 9600 bits/sec. Only 8 FGI bits are added to half- rate frames, a rate of 400 bits/sec, which with the 8 encoder bits brings the half-rate bit rate to 4000+400+400 or 4800 bits/sec. Only the 8 encoder bits are added to the rate 1/4 frames (2000 Vocoder bits/sec) and 1/8 rate frames (800 Vocoder bits/sec) bringing the bit rates to 2000+400 or 2400 bits/sec and 800+400 or 1200 bits/sec. Traffic at these four rates is convolutionally encoded using a rate 1/3 code bringing the full-rate frame symbol rate to 28.8 ksym/sec and the other rates factors of 1/2 this rate. Then all signals are made to have a common symbol rate of 28.8 ksym/sec using various degrees of repetition. These symbols are then interleaved and the symbol stream at 28.2 ksym/sec is partitioned into blocks of 6. Each block is used to select one of 64 Walsh words used in the 64-ary orthogonal modulator. The duplication potentially produced by the repetition function is removed by the data burst analyzer. The duty cycle of the output of the data burst analyzer during any frame equals one, 1/2, 1/4, or 1/8 whenever the Vocoder frame is full-rate, 1/2, 1/4, or 1/8 respectively. The bursts from the data burst randomizer are spread by the long PN code, at the rate of 4 long-code chips per Walsh chip, and then randomized further by the short PN code offset QPSK spreader. The power of each reverse link traffic channel is carefully controlled by the open loop, closed loop, and outer loop power control procedures. Roughly speaking, the power transmitted from each mobile is controlled so that the reverse-link traffic signals arrive at their base station at the same power level.

See Data Burst Randomizer and Offset or Staggered QPSK