D-Link DWR-921 User Manual page 52

Section 3 - Configuration
Short GI:
HT 20/40 Coexistence:
D-Link DWR-921 User Manual
Check this box to reduce the guard interval to 400 ns. This can
increase the throughput rate provided that the delay spread
of the connection is also low. However, it can also increase
error rate in some installations, due to increased sensitivity to
radio-frequency reflections. Select the option that works best
for your installation.
Enable this option to reduce interference from other
wireless networks in your area. If the channel width
is operating at 40 MHz and there is another wireless
network's channel over-lapping and causing interference,
the router will automatically change to 20 MHz.
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