ISL3873 Datasheet, PDF (30/31 Pages) Intersil Corporation – Wireless LAN Integrated Medium Access Controller with Baseband Processor

ISL3873
RSSI Performance
The RSSI value is reported on CR62 in hex and is linear with
signal level in dB. Figure 22 shows the RSSI curve
measured on a whole evaluation radio. This takes into
account the full gain adjust range of all radio parts. To get
signal level in dBm on a radio, simply subtract the RSSI
value in decimal from 100.
120
RSSI
100
80
60
40
20
0
-100
-80
-60
-40
-20
0
SIGNAL LEVEL IN dBm
FIGURE 22. RSSI vs SIGNAL LEVEL
Signal Quality Estimate
A signal quality measure is available on CR51 for use by the
MAC. This measure is the SNR in the carrier tracking loop
and can be used to determine when the demodulator is
working near to the noise floor and likely to make errors.
Figure 23 shows the performance of the SQ measure versus
signal to noise level.
100
90
80
70
60
50
40
PER
30
MEAN
20
STDDEV
10
0
-10
-5
0
5
10
15
20
25
SNR IN THE SPREAD BANDWIDTH AT 1Mbps
FIGURE 23. SIGNAL QUALITY MEASURE AND PER vs SNR
ED Threshold
The performance of the ED threshold is shown in Figure 24.
Setting this threshold will effect CCA only. Using ED as part
of the CCA measure will allow deferral to large signals even
if they are not correlated to the desired spread signals.
ED can be read from CR61 bit 4. Using ED and RSSI can
assist the MAC in determining the presence of non
correlating signals such as frequency hoppers or microwave
ovens. For example, the MAC can elect to try to transmit
over microwave oven interference but not count the results in
rate shifting algorithms.
40
30
20
10
0
-10 ₀
STARTS MISSING
MISSING
10
20
30
40
SNR IN SPREAD BANDWIDTH
FIGURE 24. ED THRESHOLD vs SNR IN dB AT 1Mbps
30