Increasing the range on an AP is one thing and easy enough, the weak point of all this is the receiver/user being able to get back to you. The receiver will always be able to receive you but not always be able to send back to you due to its limited power which is mostly laptop's.
The wireless 802.11 is very similar to the mobile 3g network design. In 3g we keep the broadcast dominated into an area because the users want high capacity = high power/channels. If we spread it too wide/far we don't have enough channels/bandwidth for everyone to get a good throughput.
If we increase the range we increase the amount of users that can see the cell, this also increases the noise level (EC/NO in the 3g networks) which then decreases the quality for all concerned regardless of how close you are to the antenna.
On 3g and 2g networks, just because you see full bars on your phone does not mean you will be able to make a call. The same concept goes for 802.11, to get good capacity keep the antenna range short, to give signal to lots of users but with low bandwith then point the antenna at 90% or turn up the power.
For the sake of the price of a 2nd antenna it is not worth it.
Unfortunately the WLC > DTP settings is all you have which is probably set to 1, max.
Your options are:
- Outdoor situation, Install another AP with external RP-TNC connectors, choose appropriate antenna that can focus the RF beam in your chosen general direction and hope your clients have enough power to communicate back to the
- Indoor situation, just install another AP in that area and let RRM sort out your channels and power.
I somewhat agree with what you are saying John, however the AP he is talking about is an integral antenna design so you could not add another antenna. Adding another antenna to an Access Point would not add more coverage, this is simply for diversity. In diversity only one antenna functions at a time by the algorithm built into the AP.
ldorado, are you trying to get more coverage on the a radio side or the b/g side? The a side will always have a smaller coverage area because of the decreased cell size. Withthe internal antenna if you have it set to max on the controller you cannot go any higher. If you had an external antenna AP you could add a higher gain antenna such as a 6dbi omni or a patch antenna for that matter.
I would check to see what strength level your radios are operating at. If they are at level 1, which is full power, then your only option is to add another AP. If they are not, then are you using RRM? RRM has intentionally turned down your radios because another AP is close by. You could always turn off RRM and manage everything manually, but I wouldn't recommend it.
I guess the original question is more going into the direction of the N-standard support of the 1142N and not just plain antenna power. With N-capabilities you can use beamforming and spatial multiplexing which can get you twice as far as with a plain non-n-capable radio. It also can improve signal quality even if the client is not n-capable. G-only or worse b-only nodes will drag down other clients to pretty low levels compared to native n-only cells. Depending on the answers this could be a compination of all these factors.
With an 1142, you can get increased range to non 802.11n clients by using beamforming (ClientLink). With the new 3600 series of AP's and ClientLink 2.0 you can also do beamforming to 802.11n clients as well. Keep in mind that in most cases the limiting factor is the power/antenna limitations in the client. Cranking up the transmit power on the AP doesn't do any good if the AP can't hear the client.
Don't forget that an iPad uses only 10mW output power in contrast to up to 50 (100) mW of a PC WLAN interface. This is due to power saving reasons. The Gartner Group has released a study which outlines the need of a much denser deployment if you like to support such "low-power-devices". Worst case up to 300% of the APs compared to a "normal" powered device setup. Furthermore iPads do not support CCX which makes the roaming behavior a bad experience. Luckily nobody uses an iPad as a phone. Roaming time without CCX is approx 500ms and more compared to 10-30 ms with CCX. Also don't foget that joining an domain as demanded by security policies is not supported. I think neither Android nor iPad is ready for prime time unless you use a modified version like the Cisco tablet with a modified kernel.
Great detailed breakdown of client radio differences. I've been tasked with incorporating iPads in our environment and I have found all of you comments to be right on the money. Everything from the tx power differences down to the lack up support to joing a windows domain. It has been a challenge, but a challenge isn't a bad thing.