Each 20 millisecond frame in EIA/TIA-95-B CDMA is divided into sixteen “power control groups”. When the mobile transmits, each power control group contains 1536 data symbols (chips) at a rate of 1.2288 Mbps.
When the voice coder moves to a lower date rate, the CDMA mobile bursts its output by only sending the appropriate number of power control groups. For example, at quarter rate, only four of the sixteen power control groups are transmitted.
Remember that the exact location of the transmitted groups is randomized to spread the transmitted power over time. For each lowering of the data rate, the average transmitted power is reduced by 3 dB.
- Each Frame is Divided into 16 Power Control Groups
- Each Power Control Group Contains 1536 Chips (represents 12 encoded voice bits)
- Average Power is Lowered 3 dB for Each Lower Data Rate