To ensure accurate comparisons, we cleared the laptop’s cache before reloading the page: We measured the SNR value from the same laptop and client radio using AirMagnet Analyzer. For various SNRs, the following is what we found for the signal strength (found in the Windows connection status), association status, and performance when loading a particular webpage from a wireless laptop. For instance, we’ve run user-oriented tests to determine the impacts of SNR values on the ability for a user with a typical client radio (set to 30 mW) to associate with an 802.11b/g access point and load a particular webpage. My company, Wireless-Nets, has performed extensive testing of wireless LANs at various SNR levels. A SNR of 30 dB, for example, may allow an 802.11g client radio and access point to communicate at 24 Mbps whereas, a SNR of 15 dB may only provide for 6 Mbps. A lower SNR requires wireless LAN devices to operate at lower data rates, which decreases throughput. A higher SNR value means that the signal strength is stronger in relation to the noise levels, which allows higher data rates and fewer retransmissions – all of which offers better throughput. SNR directly impacts the performance of a wireless LAN connection. An increase in RF interference from microwave ovens and cordless phones, which increases the noise level, also decreases The same goes for the signals propagating from the user device to the access point. The SNR of an access point signal, measured at the user device, decreases as range to the user increases because the applicable free space loss between the user and the access point reduces signal level. Don’t let the unit “dB” throw you – it merely represents a difference in two logarithmic values, such as dBm. For example, a signal level of -53 dBm measured near an access point and typical noise level of -90 dBm yields a SNR of 37 dB, a healthy value for wireless LANs. Survey, it’s important to define the range boundary of an access point based on signal-to-noise (SNR) ratio, which is the signal level (in dBm) minus the noise level (in dBm).
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