Power Control Required in Reverse link cdma due to following reason.

Maximum System Capacity is Achieved if:

  • All Mobiles are Power Controlled to the Minimum Power for Acceptable Signal Quality in Reverse Link.
  • As a Result, all Mobiles are Received at About Equal Power at the Base Station Independent of Their Location in reverse Link.
Two Types of Control
  • Open Loop Power Control
  • Closed Loop Power Control
Open Loop & Closed Loop Power Control are Always Both Active in Reverse link CDMA

One of the fundamental enabling technologies of CDMA is power control.  Since the limiting factor for CDMA system capacity is the total interference, controlling the power of each mobile is critical to achieve maximum capacity. CDMA mobiles are power controlled to the minimum power that provides acceptable quality for the given conditions in Reverse Link.

As a result, each mobile’s signal arrives at the base station at approximately equal levels (means in Uplink for Uplink Power Control ).  In this way, the interference from one unit to another is held to a minimum.  Two forms of Reverse power control are used for the reverse link: open loop power control, and closed loop power control.

Despite what seems logical, both open and closed loop power control are active at the same time once a traffic channel is established. Both are constantly active and controlling the power of the phone according to their respective control algorithms In Reverse Power Control.