17-03-2014, 02:43 PM
Transmit Power Level
Purpose:
To verify that the transmit power level of the device under test (DUT) is within the
conformance limits.
Resource Requirements:
• Vector Signal Analyzer (VSA), Rohde & Schwarz FSQ26 or equivalent
• ERP access point/station with external antenna jack
• Associated ERP AP or station with external antenna jack (optional)
• Controlling Software (Matlab)
Last updated: June 2007
Discussion:
Reference [1] describes the Extended Rate Physical Medium Dependent (ERP-PMD) sublayer
for the 2.4 GHz band. Section 19.4.7 specifies the PMD transmit specifications, and subclause
19.4.7.1 defines the maximum allowable output power of an ERP device by reference to
18.4.7.1. Even though ERP devices occupy the unlicensed ISM band, regulatory bodies at the
national level still govern certain emissions practices, forcing observance of several different
power-level guidelines dependent upon geographical location. The maximum allowable output
power specified by the appropriate regulatory bodies is shown in Table 1, which has been
partially reconstructed below.
Procedure:
1. For DUT’s that support continuous transmission, configure the DUT to continuously
transmit on channel 6 at a data rate of 11 Mbps at maximum output power, with a duty
cycle ≥ 95 %. Otherwise, for burst mode traffic, configure the DUT to associate and
generate continuous ICMP echo request packets of length 100 bytes, and set the Beacon
Interval to 100 ms.
2. Configure the VSA to capture the waveform transmitted by the DUT. Compute the band-
power of the signal.
3. For enhanced accuracy, repeat step 2 and average the band-power of the signal.
4. If power measured is greater than 100mW (20dBm) adjust power level below 100 mW
and repeat steps 1-3.
Observable Results:
a. For a given geographic region, the maximum output power should not exceed the values
specified in Tables 1 and 2.
b. If the maximum output power level of the DUT exceeds 100 mW, it should be capable of
switching power back to 100 mW or less.