The Realities of 802.11 “Wi-Fi”

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 To better understand the contrast between what Extricom offers today and what has traditionally been done, it is important to understand the clear facts of 802.11. Being standard compliant means that we accept that the 802.11 specification is what it is. And this specification can be problematic in an enterprise environment. Here we highlight 5 important dimensions of the specification. Note that these traits are inconsequential in small deployments. After all, remember that the Wi-Fi specification is, at its heart, developed with a consumer electronics mindset. In a consumer setting characterized by a one- or two-AP setting, such things as channel scarcity, lack of mobility, and mixed mode performance are irrelevant. But, in the enterprise context, these 802.11 traits can be real obstacles. And they ARE obstacles in traditional WLANs. {go to next slide} 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.

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 6 11 1 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

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

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!

802.11 Reality #4: The Impact of Mixed Mode Mixed mode (b/g) backward compatibility degrades capacity Aggregate Throughput (Mbps) 10 5.9 6.2 6.5 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 9 7.1 8.3 8 6.3 6.6 6.9 7.5 7.7 8.4 8.5 7 6.7 7.9 8.6 8.8 6 6.4 8.7 8.9 9.1 5 9.0 9.2 9.4 4 9.6 9.8 3 9.5 9.7 9.9 10.2 10.4 2 10.7 10.9 11.1 1 11.3 11.6 11.7 11.9 12.0 0.0 22.1 #802.11b Clients Number of 802.11g Clients The first 10% of 802.11b users decreases system throughput by 50%

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