1. WLAN System Capacity Zahid Iqbal

2. WLAN Technologiess IEEE802.11a IEEE802.11b IEEE802.11g

3. 1EEE802.11a Operates on 5GHz band Uses a Radio Transmission called Orthogonal Frequency Division Multiplexing (OFDM) Data Transmission rates from 6Mbps to 54Mbps Use Carrier Sense Multiple Access with collision avoidance (CSMA/CA) for access method

4. Channels and Capacity 300MHz 5.75-5.85GHz5.25-5.35GHz5.15-5.25GHz Low band with maximum power output of 50mW Middle band with maximum power output of 250mW High band with maximum power output of 1W

5. Channels and Capacity 802.11a standard has 12 non-overlapping channels spread across 3 bands 8 of the channels are restricted to indoor use 4 channels can be used indoor or outdoors

6. Channels and Capacity Maximum Wireless Capacity (Mbps) = Rate*# of Non Overlapping Channel Maximum 802.11a Capacity = 54*12 = 648Mbps

7. IEEE 802.11b Operates on 2.4GHz (ISM) band Uses a Radio Transmission called Direct Sequence Spread Spectrum (DSSS) Data Transmission rates from 1Mbps to 11Mbps Use Carrier Sense Multiple Access with collision avoidance (CSMA/CA) for access method

8. Channels and Capacity Total 11 channels are available in the US 3 non-overlapping channels for use (Channela 1, 6,11) Max 802.11b Capacity = 11*3 = 33Mbps

9. IEEE 802.11g Operates on 2.4GHz (ISM) band Uses a Radio Transmission called Orthogonal Frequency Division Multiplexing (OFDM) Data Transmission rates upto 54Mbps

10. IEEE 802.11g Provides backword compatability with 802.11b Use Carrier Sense Multiple Access with collision avoidance (CSMA/CA) for access method

11. Channel and Capacity Total 11 channels are available in the US 3 non-overlapping channels for use (Channela 1, 6,11) Max 802.11g Capacity = 54*3 = 162Mbps

12. Capacity and Performance of 802.11

13. Coverage and Throughput Performance Free space path loss

14. Coverage and Throughput Performance Free space path loss of 2.4GHz and 5GHz with distance 10m:

15. Coverage and Throughput Performance

16. The multipath effect is modeled as a Rayleigh fading channel with a 50 ns delay spread. The shadow fading can be modeled as a log- normal distributed random variable with an 8 dB standard deviation.

17. Coverage and Throughput Performance For indoor radio environments, a two-slope path loss model with a breakpoint is used. The break point is related to the first Fresnel zone clearance, antenna height, and the transmitted frequency.

18. Coverage and Throughput Performance 802.11a802.11b802.11g Data Rate (Mbps) Distance (Feet) Data rate (Mbps) Distance (Feet) Data rate(Mbps) Distance (feet) 5424111155442 48355.51804847 368322253665 24882485 1813318107 1217012135 62256180

19. Coverage and Throughput Performance

20. For a cell radius of 65 feet, more than four 802.11b cells would have to be overlaid on top of each other to achieve the same average throughput of a single 802.11a cell.

21. Impact of co-channel Interfenece on System Capacity 802.11b/g has 3 non-overlapping channels 6 11 1

22. Impact of co-channel Interfenece on System Capacity

23. Mechanism to model the effect of co-channel interference Clear Channel Assesment Method Hidden Cells

24. Impact of co-channel Interfenece on System Capacity Co-channel interference immunity (CCI) CCA Threshold Practical CCA threshold

25. Impact of co-channel Interfenece on System Capacity

26. Conclusion 802.11a can provide coverage comparable to 802.11b upto 225 feet in a typical office environment The data rate of 802.11a is approximately 2 to 5 times better than 802.11b within the coverage distance.

27. Conclusion 802.11g can provide coverage comparable to 802.11b as well. The data rate of 802.11g in a single cell is higher than 802.11a because of the better frequency dependant path loss.

28. References James C. Chen, PhD., Jeffrey M. Gilbert, PhD, “Measured Performance of 5-GHz 802.11a Wireless LAN Systems” Proxim Corporation, “A Detailed examination of the environment and protocol parameters that affect 802.11g network performance “