WifiBasics

  Wifi Signals The main ISM or the Industrial Scientific and Medical bands used for carrying Wifi Signals are 2.4 Ghz 5 Ghz Ref : https://www.electronics-notes.com/articles/connectivity/wifi-ieee-802-11/channels-frequencies-bands-bandwidth.php These 2 bands are split into smaller frequency bands called channels. The frequency range for each channel is called the channel width. ( 20MHz, 40MHz, 80MHz) 2.4 Ghz The 2.4GHz frequency band, covers a frequency range from 2400 MHz to 2500 Mhz which is 100MHz range. This 100 Mhz range is divided into 14 channels , with each channel 20MHz wide. There is a gap of 5MHz between adjacent channels.   The adjacent channels overlap in frequency. Overlapping channels cause interference during transmissions Only 3 channels can be active at a time. There are many groups of non-overlapping wifi channels, ie 1, 6 , and 11, 2,7, and 12 This is used by 802.11b, 802.11g and 802.11n 5GHz Band The 5GH...

Rate Selection or Adaptation in Wireless Networks Depending on the Wlan standard, a wireless device can support multiple data rates. For example, an 802.11b compliant device supports 11, 5.5, 2, & 1Mbps speeds. A 802.11g capable device supports OFDM data rates of 6,9,12,18,24,36,48 and 54 Mbps and DSSS data rates of 11, 5.5, 2 and 1 Mbps. The date rate specifies the rate at which data is transmitted on the physical layer. A higher data rate guarantees a higher throughput. A high data rate requires a high received signal strength for the receiver to decode the frame. If Received signal strength of the frames is less than a specific value for that data rate, then the frames are dropped at the receiver. In poor channel conditions, the RSSI is lesser due to interference .Low data rates require low SNR values ( or low signal strength ) to decode the frames. In poor channel conditions or noisy environments, it is better to send frames at low data rates, since frame...