Factors affecting WLAN PHY Rate

The examples explained in this section focuses on the factors which affect the PHY Rate/Link Throughput of 802.11 based networks:

  • Transmitter power (More Tx power leads to higher throughput)
  • Channel Path loss (Higher path loss exponent leads to lower throughput)
  • Receiver sensitivity (Lower Rx sensitivity leads to higher throughput)
  • Distance (Higher distance between nodes leads to lower throughput)

Effect of Transmitter power#

Open NetSim and Select Examples->Internetworks->Wi-Fi-> Effect of Transmitter Power then click on the tile in the middle panel to load the example as shown in below Figure.

Figure4-1

The following network diagram illustrates, what the NetSim UI displays when you open the example configuration file see below Figure Figure4-2

Increase in transmitter power increases the received power when all other parameters are constant. Increased received power leads to higher SNR and hence higher PHY Data rates, lesser error and higher throughputs.

Network Settings

  1. Environment Grid length: 500m x 500m
  2. Distance between Access Point and the Wireless Node is set to 210m
  3. Set transmitter power to 100mW under Interface Wireless > Physical layer properties of Access point
  4. Set DCF as the medium access layer protocol under datalink layer properties of access point and wireless node.
  5. Channel Characteristics: Path Loss Only, Path Loss Model: Log Distance, Path Loss Exponent: 2.5
  6. Application Generation Rate: 10Mbps (Packet Size: 1460, Inter Arrival Time: 1168µs)
  7. Click on the Application icon present in the top ribbon/toolbar and set Transport Protocol to UDP
  8. In NetSim GUI Plots are Enabled. Run simulation for 10s
  9. Go back to the scenario and decrease the Transmitter Power to 100, 80, 60, 40 and 20 respectively and run simulation for 10s. See that, there is a decrease in the Throughput gradually

Results and Discussion#

Transmitter Power (mW) Throughput (Mbps)
100 5.82
80 5.11
60 3.80
40 3.47
20 1.67

Effect of AP-STA Distance on throughput#

Open NetSim and Select Examples > Internetworks > Wi-Fi > Effect of AP STA Distance on throughput then click on the tile in the middle panel to load the example as shown in Figure 4-3.

Figure4-3

The following network diagram illustrates, what the NetSim UI displays when you open the example configuration file see Figure 4-4.

Figure4-4

As the distance between two devices increases the received signal power reduces as propagation loss increases with distance. As the received power reduces, the underlying PHY rate of the channel drops.

Network Settings

  1. Environment Grid length: 500m x 500m
  2. Distance between Access Point and the Wireless Node is set to 10m
  3. Set DCF as the medium access layer protocol under datalink layer properties of access point and wireless node.
  4. WLAN Standard is set to 802.11ac and No. of Tx and Rx Antenna is set to 1 in access point and No. of Tx is 1 and Rx Antenna is set to 2 in wireless node (Right-Click Access Point or Wireless Node > Properties > Interface Wireless > Transmitting Antennas and Receiving Antennas) and Bandwidth is set to 20 MHz in both Access-point and wireless-node Transmitter Power set to 100mW in both Access-point and wireless-node.
  5. Wired Link speed was set to 1Gbps and propagation delay to 10 µs in wired links.
  6. Channel Characteristics: Path Loss Only, Path Loss Model: Log Distance, Path Loss Exponent: 3.5.
  7. Application Generation Rate: 100 Mbps (Packet Size: 1460, Inter Arrival Time: 116 µs)
  8. Click on the Application icon present in the top ribbon/toolbar and set Transport Protocol to UDP
  9. In NetSim GUI Plots are Enabled and Run simulation for 10s.
  10. Go back to the scenario and increase the Distance from 10m to 20m, 30m, 40m, 50m respectively and Run simulation for 10s.

Results and Discussion#

Distance (m) Throughput (Mbps)
10 22.81
20 21.61
30 17.87
40 17.66
50 12.47

Plots

Figure4-5

Effect of Pathloss Exponent#

Open NetSim and Select Examples > Internetworks > Wi-Fi > Effect of Pathloss Exponent then click on the tile in the middle panel to load the example as shown in Figure 4-6.

Figure4-6

The following network diagram illustrates, what the NetSim UI displays when you open the example configuration file as shown Figure 4-7

Figure4-7

Path Loss or Attenuation of RF signals occurs naturally with distance. Losses can be increased by increasing the path loss exponent ($\eta$). This option is available in channel characteristics. Users can compare the results by changing the path loss exponent ($\eta$) value.

Network Settings

  1. Environment Grid length: 500m x 500m
  2. Distance between Access Point and the Wireless Node is set to 50m
  3. Set DCF as the medium access layer protocol under datalink layer properties of access point and wireless node. WLAN Standard is set to 802.11ac and No. of Tx and Rx Antenna is set to 1 in both access point and wireless node (Right-Click Access Point or Wireless Node > Properties > Interface Wireless > Transmitting Antennas and Receiving Antennas) and Bandwidth is set to 20 MHz in both Access-point and wireless-node and Transmitter Power set to 100mW in both Access-point and wireless-node.
  4. Wired Link speed was set to 1Gbps and propagation delay to 10 µs in wired links.
  5. Channel Characteristics: Path Loss Only, Path Loss Model: Log Distance, Path Loss Exponent: 2
  6. Application Generation rate: 100 Mbps (Packet Size: 1460, Inter Arrival Time: 116 µs)
  7. Click on the Application icon present in the top ribbon/toolbar and set Transport Protocol to UDP
  8. In NetSim GUI Plots are Enabled and Run simulation for 10s.
  9. Go back to the scenario and increase the Path Loss Exponent from 2 to 2.5, 3, 3.5, and 4 respectively. and Run simulation for 10s.

Results and Discussion#

Path loss Exponent Throughput (Mbps)
2.0 22.81
2.5 22.81
3.0 19.30
3.5 12.47
4.0 5.57

Plots

Figure4-8