Micro Cell (Traditional Architecture) vs. Virtual Cell Architecture - 1

Micro Cell (Traditional Architecture) vs. Virtual Cell Architecture

Micro cell WLAN architecture, as used by virtually all WLAN suppliers, requires that radios
be deployed in a checkerboard pattern of radio coverage. Adjacent radios operate on
different (though somewhat overlapping) channels, and at lower than maximum power, to
minimize mutual interference and thereby enhance performance.

Clients decide when to switch between channels based on changes in signal strength, i.e.,

moving away from channel 1 and towards channel 6 causes the former to drop in strength

and the latter to rise. It is therefore important that adjacent channels overlap as little as

possible to allow the clients to switch efficiently. Additionally, since adjacent channels

have overlapping radio energy it is important to isolate adjacent channels as much as

possible to prevent signal contention. Lowering output power increases the isolation of

adjacent channels but lowers both signal-to-noise ratio and the effective operating range.

Micro cell architecture is very inefficient with respect to the consumption of wireless

bandwidth, since three or four radio channels are required to avoid the overlap of adjacent

radios. In a 2.4GHz 802.11b/g deployment, key channels 1, 6, and 11 must all be dedicated

to the micro cell deployment, leaving no free channels available for other uses.

Additionally, channel planning and maintenance programs must be used to properly locate

radios to minimize co-channel interference while optimizing radio coverage. Channel

planning must be conducted at both the initial deployment and with every addition, move,

or change to the system.

By contrast, Meru’s Virtual Cell architecture aligns clients and Access Points on a single

radio channel. All of the clients and Access Points can be considered, metaphorically, to

reside on a single plane which is defined by the radio channel on which they reside. Access

Points are coordinated by a Meru Controller, which determines when clients are handed-off

by analyzing signal quality - in this architecture clients do not themselves decide when to

switch between Access Points.

Adjacent channel interference is not an issue with Virtual Cell architecture; Access Points

can be operated at full output power and situated where needed for optimum, overlapping

coverage, including being located in close proximity to one another. High output power

and overlapping coverage together minimize the number of Access Points and ensure that

clients remain networked in the event of a failure of one radio. In the example below the

Virtual Cell is operating on channel 1.