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
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
Being standard compliant means that we accept that the 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 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.

3. 802.11 Reality #1: A Frequency Constrained Environment
Available non-overlapping channels
3 for b/g (2.4 GHz)
Up to 13 for a (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

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
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 g Clients
The first 10% of b 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