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Excellent question and one that is often asked.

The general assumption is that the overall system throughput decreases, however, because the system is constantly monitoring the location and communication to all clients within the coverage blanket, we are able to dynamically controll the collision domains and can create an a aggregate throughput of up to 9x per channel.

Let me start this explanation with a rewind to traditional cell planning. Lets take a typical b/g cell plan.

Lets assume that we have a client operating on channel 11 in this example. In this topology the net result of throughput is 1+1+1=1. Why?

Well in the real world of cell planning we have to contend with :


Range Limitations

Edge Users

Limited Number of Users

Reuse Range

Interference Range

Coverage / Capacity

From our whitepaper "Extricom WP - WLAN and the Broadband Myth" found at
http://www.extricom.com/content/documents/whitepapers

"To increase capacity on the wireless network, frequencies are reused. Reusing a frequency
requires careful cell planning. In practice, frequency reuse is seldom achieved, because unless
cells are very far apart, they share collision domains. All nodes in the same collision domain
share the same bandwidth. Placing two cells on the same channel within the same collision
domain provides each with half of the bandwidth.
In accordance with the 802.11 standard, Clear Channel Assessment (CCA) must be used
before a node transmits to ensure that the frequency is clear for transmission. The Physical
Layer Convergence Protocol (PLCP) also limits the reuse range, but in practice, CCA will
almost always be the determining factor of reuse range.
CCA measures the amount of energy in the channel without regard to packets, transmission
speed, or even source of energy (whether it is an AP or a microwave oven). Since energy can
be detected over hundreds of feet, CCA may place far too many cells in the same collision
domain. In Figure 2, the blue cells and the red cells are very likely to be in the same collision
domain. In other words, it is actually CCA reach that will determine the collision domain size,
and not the cell size at the highest data rate.
Moreover, the CCA mechanism is notoriously unreliable, and may provide both false positives
and false negatives. The CCA may indicate that the channel is clear when, in fact, it is not
(false negative). This will result in co-channel interference. On the other hand, the CCA may
indicate that the channel is not clear when, in fact, it could be reused.

Extricom provides true frequency reuse with patented TrueReuse?¡é???¡é technology. While the blanket provides the coverage, mobility, and link resilience benefits
already described, TrueReuse introduces a way to boost the aggregate capacity of that blanket.
TrueReuse essentially takes the concept of frequency reuse and actually delivers the benefit
that had long been hoped-for in cell planning topologies. To increase the capacity of the
channel, the Extricom switch uses its real-time knowledge of the entire system to decide when
to permit multiple access points to simultaneously transmit on the same channel, to different
clients, without causing co-channel interference. In essence, TrueReuse takes a single collision
domain and dynamically splits it into sub-collision domains, thereby multiplying aggregate
capacity.

How? The system dynamically measures the RF reception quality from each client on a
packet-by-packet basis. These measurements are used to create a high granularity, real-time
map of co-channel interference throughout the deployment. This map is then used to
determine when simultaneous transmissions on the same channel will not cause co-channel
interference. The switch uses its real-time information to overcome the limitations imposed by
the CCA mechanism, and to provide efficient frequency reuse.

The net result is a multiplication of the aggregate capacity of the channel blanket. The
Extricom system will deliver three times to nine times more system bandwidth than a
comparable cell-planning system. What?¡é?€??s more, this bandwidth multiplication is in addition to
that which is achieved through the ?¡é?€??stacking?¡é?€?? effect of overlapping channel blankets.
The combined use of TrueReuse technology, and Extricom?¡é?€??s ubiquitous AP placement on the
same channel, allows the Interference-Free architecture to greatly reduce the AP-to-AP
distance necessary for effective reuse. By making decisions on a packet-by-packet basis,
Extricom avoids co-channel interference and uses RF resources to the maximum."

Let me know if this helps to answer your question.