The Realities of 802.11 “Wi-Fi”

1. The Realities of 802.11 “Wi-Fi”

2. The Realities of 802.11 • Scarcity of Radio Channels • Throughput varies with distance • Protocol designed for portability, not mobility • Mixed mode (b/g) backward compatibility degrades capacity • Voice and data contention degrades capacity and service quality These traits are inconsequential in small deployments. But have major implications for mid-to-large systems. The Extricom solution overcomes all of the above constraints.

3. 11 6 6 1 11 11 6 802.11 Reality #1:A Frequency Constrained Environment • Available non-overlapping channels • 3 for 802.11b/g (2.4 GHz) • Up to 13 for 802.11a (5GHz) • Frequency re-use rarely happens in practice • Clear Channel Assessment (CCA) is range always greater than useable range • Results in co-channel interference and/or collision domain sharing 1 Re-use distance Re-use distance 1 Re-use distance 1 • APs Closer Together  bandwidth stays the same or decreases • APs Farther Apart  bandwidth decreases

4. 802.11 Reality #2:Variable Throughput • The greater the distance from the AP, the slower the connection and throughput

5. 802.11 Reality #3:Portability, Not Mobility • Protocol is designed for portability, not mobility • Handoff decision is up to the client, instead of the infrastructure Inefficient Handoff due to “sticky” clients – a few can drag down all others 11Mbps 36Mbps 11Mbps Bunching: Clients hold on to an AP, even when a better AP is available. Edge Users: 2.5X more clients at the edge than in the high speed zone!

6. 802.11 Reality #4:The Impact of Mixed Mode • Mixed mode (b/g) backward compatibility degrades capacity The first 10% of 802.11b users decreases system throughput by 50%

7. 802.11 Reality #5:Voice and Data Contention • Different traffic types degrade service quality • 802.11e is a statistical answer to QoS • A statistical method – does not guarantee priority • Requires client support