Wireless throughput decreases over distance. Does the signal's effective range decrease as more clients connect?

Question

This is probably a two- or three-part question. Let's set a sample environment first:

• We're using one AP
  • One 2x2 radio antenna
    • Omnidirectional
    • 802.11n (2.4GHz)
    • Up to 30 client devices
  • Mounted to suspended ceiling; center of the room
  • No 2.4GHz interference is occurring
  • A threshold RSSI of -65dBm is set for clients in order to associate
    • Signal has been measured and shows that coverage is guaranteed up to 40ft
• Clients use the same USB Wi-Fi dongle (802.11n)
• SSID is open, no authentication

Assume five devices are initially associated with the AP:

• two are under 8 feet away (-35dBm RSSI)
• two are around 15 feet away (-46dBm RSSI)
• one device failed to connect 42 ft away (-68 dBm). They are now sitting at 37 ft away (-62 dBm RSSI) and have associated

Everything is within spec and OK.

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We know that as a client device moves further away from the AP their throughput rate will decrease. We also know that as multiple clients connect to the AP their bandwidth will decrease since it shared across all devices.

Now, assume ten clients entered the network and settled within 10 feet of the AP.

• Would the furthest client see a dip in its RSSI? Would this be more drastic if the density of clients moved even closer to the AP?

  • e.g. Has our effective range dropped to some measurement below 40ft?

• Does the throughput/transmit rate (not bandwidth) of the furthest client drop as the number of clients increases? If so, is this impacted more severely as the density of clients moves closer towards the AP?

Answer 1

Would the furthest client see a dip in its RSSI? Would this be more drastic if the density of clients moved even closer to the AP?

The position of other clients has no influence on the received signal strength indicator unless they are attenuating the signal by obstructing it etc. and therefore causing the client to receive a weaker signal.

Does the throughput/transmit rate (not bandwidth) of the furthest client drop as the number of clients increases? If so, is this impacted more severely as the density of clients moves closer towards the AP?

The Tx rate of a client may drop if the signal to noise ratio is degraded, or if airtime consumption increases. A high density of clients moving closer to the AP may improve performance since they may make more effective use of the airtime, by utilising more efficient modulation at higher data rates.