wireless range

[ahmedalshami]

dear

i use unified wireless system :

wism

90 1020 WAP (internal antennas)

the problem is the coverage is too bad i need to increase the coverage @11 mbps at least

please advice

[Rob Huffman]

Hi Ahmed,

These questions are always tough to answer without knowing your environment and doing the requisite site survey. It is likely though, that the Internal antennas of the 1020 aren't providing the coverage you desire. The nice thing is that the 1020 supports a wide variety of External antennas so you have lots to choose from. An External antenna will almost certainly increase your coverage areas. The 1020 model comes with internal 802.11a/b/g antennas, and also supports external antenna connectors, providing the greatest deployment flexibility.Antenna capabilities for Cisco 1020 lightweight access points include, High-gain omnidirectional, narrow-beam directional, diversity, and nondiversity antennas are available for both operating bands. For more information on antenna options and some range estimates;

Omni Antenna vs. Directional Antenna

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a00807f34d3.shtml

Cisco Aironet 2.4 GHz and 5 GHz Antennas and Accessories

http://www.cisco.com/en/US/products/hw/wireless/ps469/products_data_sheet09186a008022b11b.html

Cisco Aironet Antenna Reference Guide

http://www.cisco.com/en/US/products/hw/wireless/ps469/products_data_sheet09186a008008883b.html

Hope this helps!

Rob

[jwadleigh]

Hi -

As mentioned in the last post, the only way to determine the best course of action would be to have a professional site survey done. The site survey will analyze real world data about your environment to determine how best to provide the required coverage.

However, if you want to take a crack at it yourself, this might help.

Conceptualizing coverage problems becomes easier if you think of the coverage provided by each access point as a sphere (though in reality the shape is not spherical at all).

There are really only 3 ways to improve coverage of a given area:

1.) Increase the size of the spheres (by increasing the power level).

2.) Change the shape of the spheres (by changing the antenna type - a higher gain antenna will flatten and widen the shape).

3.) Increase the position and/or number of the spheres (by moving or adding additional AP's).

[msaulnier]

How can you estimate the size of the sphere for a specific antenna ?

[jwadleigh]

The short answer, unfortunately, is that you can't.

First, these are not "spheres" at all, but completely irregular, lop-sided shapes. The shape is based on a number of factors:

1.) Signal propagation based on the design of the antenna (which has a shape under ideal conditions, e.g. a vacuum). For instance, an omnidirectional antenna propagates 360 degrees on the horizontal axis.

2.) Sources of interference which may impede or destroy RF signal. (A list of possible sources would best be the subject of another post.)

3.) Barriers for the RF, which either block or attenuate the signal. These may take the form of thick, steel-reinforced walls, stairwells and elevator shafts, etc. A site survey would show the RF shadow caused by such a barrier.

In other words, the propagation of RF is dependent on so many factors, that even if there were a way to give an estimate of distance based solely on the hardware used, it wouldn't be of any real value in practice.

My suggestion would be to have a full professional site survey done to determine the best placement and density of AP's for your environment. If that's not an option for you, do a small pilot (3 AP's or so) and place them in temporary locations in your environment. You can then do a little "trial-and-error" on them to see a) the best locations for installing them permanently, and b) an idea of how many you'd need for the entire site.

Hope this helps! Let us know how you made out.

[msaulnier]

What do you do when there no site to survey ? I need to budget a wireless solution for a new building. With all the numbers and the radiation pasterns in the antenna spec there must be a way to calculate the theoretical range of the antenna.

[jwadleigh]

Without knowledge of the interior structures within this new building, it would be nearly impossible to even make an educated guess. Different building materials absorb, reflect, and distort RF energy differently. Some walls have absolutely no effect whatsoever on RF (signal strengths are equally strong on both sides). Other walls block RF signal entirely (signal strength is strong and clear on one side and nonexistent on the other).

Of course, you could always arbitrarily provision AP's evenly distributed throughout the building (for budget and planning purposes), let's say at a given density (e.g. 1 per x sq ft of floorspace). Just remember that this will probably not provide the necessary coverage and will have to be augmented and revised once implemented.

Sorry if this is not the answer you were looking for.