We have simplified the equation, and
it is given below.
(7.125)
where PUE UE transmit power; PCPICH path loss of CPICH channel; IBTS interference power
seen by the NodeB; and K constant value (set by higher layers).
The open-loop correction provides a quick response to the mobile environment. The open-loop
correction is generated as in Fig. 7.88, where r(t) is the received signal.
PUE PCPICH IBTS K
FIGURE 7.88 Open-loop power control measurement flow.
RC r(t) RAKE
Fingers
Power
Measurement
Apply
Equation
To UE Transmit
Gain Control
Despread
Symbols
Variable K obtained
through higher-layer
messages
This is used when a UE is powered ON, extracts the cell system information from the BCH transport
channel, and then needs to transmit a message such as PRACH.
The second form of power control is the closed inner loop. Two inner loops exist, one for the UE
and one for the NodeB, which respectively measure their received signal power and determine the
correction. For example, in an effort to refine the open-loop estimate, the NodeB must measure the UE??™s
transmit power and then feed back a power control command to the UE to increase or decrease its
transmit power. The rate at which the correction is applied for WCDMA is 1500 Hz, with step sizes
of
1 or
2 dB.
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