Understanding TPC Values
Transmit Power Control (TPC) values determine how the transmit power of the receiving base or mobile station will increase or decrease over specific time slots. In the channel table editor, TPC values are represented in hexadecimal format to simplify entries and modifications. The following figure shows the channel configuration node for a DPCCH channel, with a TPC value of 7F80.
Hexadecimal TPC values are converted to their binary equivalent. In this example, the value 7F80 becomes 111 1111 1000 0000. Notice that there are 15 digits in the binary TPC value. Because one frame contains 15 timeslots, one binary digit is assigned to each timeslot (see figure below). The assigned bit is then repeated enough times to fill the TPC bit field (see the NTPC column in the table below). Since the example in the following figure uses two TPC bits per timeslot, the values are either 11 or 00.
The TPC bits that are ones (1) direct the receiving base or mobile station to increase its transmit power by an amount specified by the W-CDMA standard. Likewise, TPC bits that are zeros (0) cause the power to decrease by the same amount. In this example, the transmit power is increasing over timeslots 0 through 7 and decreasing over timeslots 8 through 14.
TPC Bits per Timeslot
|
Slot Format |
Channel Bit Rate (kbps) |
Channel Symbol Rate (ksps) |
Spread Factor |
Bits/ Slot |
DPCCH Bits/Slot |
||
|---|---|---|---|---|---|---|---|
|
NTFCI |
NTPC |
Npilot |
|||||
|
0 |
15 |
7.5 |
512 |
10 |
0 |
2 |
4 |
|
1 |
15 |
7.5 |
512 |
10 |
2 |
2 |
4 |
|
2 |
30 |
15 |
256 |
20 |
0 |
2 |
2 |
|
3 |
30 |
15 |
256 |
20 |
2 |
2 |
2 |
|
4 |
30 |
15 |
256 |
20 |
0 |
2 |
4 |
|
5 |
30 |
15 |
256 |
20 |
2 |
2 |
4 |
|
6 |
30 |
15 |
256 |
20 |
0 |
2 |
8 |
|
7 |
30 |
15 |
256 |
20 |
2 |
2 |
8 |
|
8 |
60 |
30 |
128 |
40 |
0 |
2 |
4 |
|
9 |
60 |
30 |
128 |
40 |
2 |
2 |
4 |
|
10 |
60 |
30 |
128 |
40 |
0 |
2 |
8 |
|
11 |
60 |
30 |
128 |
40 |
2 |
2 |
8 |
|
12 |
120 |
60 |
64 |
80 |
8 |
4 |
8 |
|
13 |
240 |
120 |
32 |
160 |
8 |
4 |
8 |
|
14 |
480 |
240 |
16 |
320 |
8 |
8 |
16 |
|
15 |
960 |
480 |
8 |
640 |
8 |
8 |
16 |
|
16 |
1920 |
960 |
4 |
1280 |
8 |
8 |
16 |
|
TPC Bit Pattern |
Transmitter power control command |
||
|---|---|---|---|
|
NTPC = 2 |
NTPC = 4 |
NTPC = 8 |
|
|
11 00 |
1111 0000 |
11111111 00000000 |
1 0 |