Cell Power, AWGN (Additive White Gaussian Noise) Power and Total RF Power

Last updated: July 23, 2008

The test set's access network emulator provides control over the following RF power levels:

Cell Power

Î_or is defined in C.S0033 as the received power spectral density of the Forward Channel as measured at the access terminal antenna connector. The Forward Channel is defined as a CDMA Channel from an access network to access terminals. The Forward Channel is transmitted on a CDMA frequency assignment using a particular pilot PN offset. If you have accounted for path loss (see Amplitude Offset ) between the test set output port and the access terminal antenna connector, then cell power is equivalent to Î_or .

AWGN Power

I_oc is defined in C.S0033 as the power spectral density of a band-limited white noise source (simulating interference from other cells) as measured at the access terminal antenna connector. If you have accounted for path loss, then AWGN power is equivalent to I_oc .

The test set also reports:

Total RF Power

Total RF Power is the sum of cell power and AWGN power. I₀ is defined in C.S0033 as the total received power spectral density, including signal and interference, as measured at the access terminal antenna connector. If you have accounted for path loss, then total RF power is equivalent to I₀ .

E_b /N_t

E_b /N_t is the ratio (in dB) of the combined received energy per bit to the effective noise power spectral density for the Control Channel or Forward Traffic Channel at the access terminal antenna connector (assuming you have accounted for path loss). It is calculated as follows:
Traffic E_b /N_t = Traffic_Chip_Bit + Î_or /I_oc (all in dB). (Traffic_Chip_Bit is the number of PN chips per Forward Traffic Channel bit.)

NOTE

When the test set is in a configuration of Multi-carrier Multi-unit (MCMU) , Eb/Nt is calculated on each test set separately. The Eb/Nt will not be accurate if overlapping channels are being generated or if multiple AWGN sources (internal or external units) are overlapping (AWGN has a larger bandwidth than the channel). For example, in an MCMU setup, the Eb/Nt will not be accurate in most situations if AWGN is turned on for multiple units.

Cell Power, AWGN Power and Total RF Power Ranges

The range of values that you can set these power levels to differs from the actual hardware range of the source. This is due to compensation for path loss between the test set output and the access terminal antenna connector (see Amplitude Offset ).

For example, if you enter a value of -30 dBm for desired CW cell power, this indicates that you want -30 dBm of power at the access terminal antenna connector. So, if you have indicated an amplitude offset of -3.5 dB exists between the test set's RF In/Out port and the access terminal's antenna connector, the source will actually have to output -26.5 dB in order to deliver -30 dB to the access terminal antenna connector. Thus, with an amplitude offset of -3.5 dB, the settable range of CW cell power is -130.5 dB to -13.5 dB. The actual power range at a given time is defined by adding the value of the associated amplitude offset to the actual hardware range. If you select an invalid combination of power levels and amplitude offsets, an error message will appear.

Range of Power Levels
Parameter	Actual Hardware Range with Amplitude Offset = 0 (RF In/Out Port)	Actual Hardware Range with Amplitude Offset = 0 (RF Out Only Port)	Setting (or Query) Range
Cell Power (CW)	-127 dBm to -10 dBm	-119 dBm to -2 dBm	-177 dBm to +40 dBm
Cell Power (DIGital856)	-120 dBm/1.23 MHz to -13 dBm/1.23 MHz	-115 dBm/1.23 MHz to -5 dBm/1.23 MHz	-170 dBm/1.23 MHz to +37 dBm/1.23 MHz
AWGN Power (DIGital856)	-120 dBm/1.23 MHz to -15 dBm/1.23 MHz	-115 dBm/1.23 MHz to -7 dBm/1.23 MHz	-170 dBm/1.23 MHz to +35 dBm/1.23 MHz
Total RF Power	-120 dBm/1.23 MHz to -10.88 dBm/1.23 MHz	-115 dBm/1.23 MHz to -2.88 dBm/1.23 MHz	-170 dBm/1.23 MHz to +42 dBm/1.23 MHz
Eb/Nt			-24.26 dB to +33.80 dB

For the lab application , an external AWGN value is available when the test set is configured to generate faded forward channel signals with AWGN. This setup requires a rear panel digital bus connection to an external PC running Baseband Studio software. See Digital Bus Information for details.

Programming Usage

The test set includes commands to set the desired cell power and AWGN power levels. You may also query what you've set these desired power levels to, as well as query what the total RF power will be based on your desired cell power and AWGN power levels. See "Command to Set/Query Desired Level" in RF Power Levels and Noise Ratio Commands .

The test set also includes commands to query the current level of cell power, AWGN power, total RF power and E_b /N_t . See "Command to Query Current Level" in RF Power Levels and Noise Ratio Commands . These CALL:STATus commands are query only. They return values that indicate the test set's actual hardware settings and hardware status. Actual hardware settings can differ from the desired level you've set if you've broken one of the rules above for setting power levels. If this happens, there will be a persistent error reported by the test set indicating the problem. When no error conditions exist, the commands used to set the desired level will return the same results as the commands used to query current level. For example, "CALL:AWGNoise:POWer?" will return the same value as "CALL:STATus:AWGNoise:POWer?" when no error conditions exist. Although the CALL:STATus commands are available for your use, it is a best practice to query the desired power levels instead and include error trapping in your control program to look for errors indicating the desired and current power levels are not equal (see Error Messages ).

RF Power Levels and Noise Ratio Commands
Parameter	Command to Set/Query Desired Level	Command to Query Current Level
Cell Power	CALL[:CELL]:POWer[:SAMPlitude]<[:SELected]\|:CW\|:DIGital856>	CALL:STATus:CELL[1]:POWer:[AMPLitude]<[:SELected]\|:DIGital856>?
AWGN Power	CALL:AWGNoise[:INTernal]:POWer[:SAMPlitude]<[:SELected]\|:DIGital856>	CALL:STATus:AWGNoise[:INTernal]:POWer[:AMPLitude]<[:SELected]\|:DIGital856>?
Total RF Power	CALL:TOTal:POWer[:AMPLitude]<[:SELected]\|:DIGital856>? (query only)	CALL:STATus:TOTal:POWer[:AMPLitude]<[:SELected]\|:DIGital856>?
E_b /N_t	none	CALL:STATus:TRAFfic[:CELL[1]]:EBNTotal?

Rules for Setting Power Levels and Amplitude Offsets

The difference between cell power and AWGN power must not be more than 35 dB when both powers are ON.
The total RF power and amplitude offset must not set the source outside its valid hardware range.
When the test set is configured to physical layer subtype 2 and both Cell power and AWGN power are On, the power level of any MAC code channel generated must not be greater than 30dB below the current Total RF Power. When any cell or AWGN power level is changed such that any code channel is more than 30dB below the Total RF Power, an error message is posted to indicate the error condition. When this happens, the cell or AWGN setting is pended (not applied to the hardware) and the current power setting is not updated (left at previous value). See Code Channel Parameters for setting the power levels of the MAC code channels.