Wireless Coverage Solution

[bradleywarnock]

One question I have is how this works as far as support from Global Service Desk. I think the 1040W have various features such as sensing each other and responding by picking different channels. I think I also saw something about being able to detect rouge access points.

We offer direct support. Today the Global Service Desk does not support it. I would not be the reference for 1041W features, though you may not need the device if True Gain covers the entire building. You would simply employ the features of the 881W, it functions without regard to the True Gain Module signal improvement.

[bradleywarnock]

According to the web site this is booster for the antennas on the 881. Should have NO changes to the system and probably can not even be detected by Global Services. IF the FM group would purchase I think we could see some real savings in setup of wireless in MOST buildings. Wish I knew how to get it on the FM list so they could purchase them for us.

You have it right Ken, True Gain is seamless and transparent to the Cisco 881W. Just configure it as normal. The real savings is in installation. Perhaps ask the FM to source it for you. We'll pursue from our side. Thanks, Brad

[russellhltn]

We offer it at $450 shipping included (55% off). How does that compare with 2 APs?

Considering that if the FM group orders it, they pay for the two APs ... I really think you need to work on getting on the FM group's "catalog".

[johnv]

You have it right Ken, True Gain is seamless and transparent to the Cisco 881W. Just configure it as normal. The real savings is in installation. Perhaps ask the FM to source it for you. We'll pursue from our side. Thanks, Brad

Correct me if I'm wrong (the website doesn't really present any technical data behind this device, both links to specs are broken), but just by adding gain to the AP side doesn't necessarily give you more coverage in your building. It will definitely broadcast the signal out stronger (transmit), but because your client radio (laptop, tablet, or mobile phone) still can only transmit back with a limited range from it's much lower gain built in antenna. In other words, your tablet will receive (see) a stronger signal but will not necessarily work any better because the tablet transmit rate will still be weak and will still have a hard time penetrating multiple walls. Any gain from one side doesn't increase your gain from the other side. Your device will have a strong rx (receive) but a weak tx (transmit) which will result in lower overall connection quality or speed (SNR, CCQ, or however you want to measure it).

Case in point, You can add an antenna to any router to broadcast the signal 10 miles, but NO device without a similar gain antenna on the other side will be able to broadcast the signal 'back' 10 miles. So your device will see it, but it will not work.

Also, I don't see how that device will work with MIMO ('N') routers, you would in theory need one for each antenna (two or three). Not sure how cost effective that would be.

John

[bradleywarnock]

Correct me if I'm wrong (the website doesn't really present any technical data behind this device, both links to specs are broken), but just by adding gain to the AP side doesn't necessarily give you more coverage in your building. It will definitely broadcast the signal out stronger (transmit), but because your client radio (laptop, tablet, or mobile phone) still can only transmit back with a limited range from it's much lower gain built in antenna. In other words, your tablet will receive (see) a stronger signal but will not necessarily work any better because the tablet transmit rate will still be weak and will still have a hard time penetrating multiple walls. Any gain from one side doesn't increase your gain from the other side. Your device will have a strong rx (receive) but a weak tx (transmit) which will result in lower overall connection quality or speed (SNR, CCQ, or however you want to measure it).

Also, I don't see how that device will work with MIMO ('N') routers, you would in theory need one for each antenna (two or three). Not sure how cost effective that would be.

John

Excellent insights. (BTW, sorry about the links, Wordpress was giving fits. I fixed a few, but I will review again later.).

Your comments are traditionally correct, except that the True Gain Module has a highly sensitive receive and filter chain in addition to receive power increase. This gives the low power client some symmetry in bi-directional signal strength. Our data throughput tests show excellent results. In the last building installed, the chapel was a dead zone - no connection. Using True Gain, the pulpit had 5-8 MB connection using a 802.11n MIMO client and ~1.5 MB using a 802.11g client. Worked well for buffered video and web applications.

Thank you for the MIMO clarification. $450 is for the model SGM-2410ID-M3. That's a 3x3 MIMO device (triple antennas) compatible with the Cisco 881W.

[russellhltn]

Case in point, You can add an antenna to any router to broadcast the signal 10 miles, but NO device without a similar gain antenna on the other side will be able to broadcast the signal 'back' 10 miles. So your device will see it, but it will not work.

You have to measure the entire path and not just "one side". The device seems to have gain on receive as well which would address that situation. The user's device still sends at low power, but now the AP is more sensitive.

There is another area of concern - the "hidden transmitter" problem. Since all the devices share the same network, they need to work cooperatively to take turns. If someone is "on the frequency" they wait until they hear silence before transmitting. But if the devices can't hear each other, that breaks down and you can end up with an excessive number of retries.

[bradleywarnock]

You have to measure the entire path and not just "one side". The device seems to have gain on receive as well which would address that situation. The user's device still sends at low power, but now the AP is more sensitive.

There is another area of concern - the "hidden transmitter" problem. Since all the devices share the same network, they need to work cooperatively to take turns. If someone is "on the frequency" they wait until they hear silence before transmitting. But if the devices can't hear each other, that breaks down and you can end up with an excessive number of retries.

Wow. I appreciate the excellent detail of the questions and the expertise of the forum members. Well done. You are right in that clients use a "listen before you talk" protocol, but the access point manages the interaction with each client. If the clients could not see the AP, you are right, there would be a problem. Since all clients can see the AP, then the problem is mitigated because the AP manages the individual client links.

[russellhltn]

Since all clients can see the AP, then the problem is mitigated because the AP manages the individual client links.

I did some checking. It may only partualy help. I did find this:

At the 23rd annual conference on Local Computer Networks, researchers from Colorado State University indicated, "Our simulations indicate that hidden terminals can have a very detrimental effect on the performance of the IEEE 802.11b MAC protocol." In an indoor environment, the RTS/CTS mechanism along with CSMA/CA may be sufficient, but it is simply not suited for long-range, high-speed wireless communications between buildings.

The page looks a bit dated, so perhaps "g" has resolved some of these issues. But it still seems there can be issues with nodes competing for the AP's attention that cannot hear each other. I think the real test would be to have two nodes attempt to stream data while located at opposite ends of the AP's range.

[johnv]

Your comments are traditionally correct, except that the True Gain Module has a highly sensitive receive and filter chain in addition to receive power increase. This gives the low power client some symmetry in bi-directional signal strength. Our data throughput tests show excellent results. In the last building installed, the chapel was a dead zone - no connection. Using True Gain, the pulpit had 5-8 MB connection using a 802.11n MIMO client and ~1.5 MB using a 802.11g client. Worked well for buffered video and web applications.

Sounds exactly like an amplifier...either way, when you boost the gain - you boost the noise as well.

I'm not trying to be too cynical, but physics are physics.

In that Chapel scenario what were the before and after Tx/Rx levels and quality of link. I have seen a lot of links that look good for tests and then poop out when you hit them hard with video streams and some noise. What are you using to measure results?

[bradleywarnock]

I did some checking. It may only partualy help. I did find this:

The page looks a bit dated, so perhaps "g" has resolved some of these issues. But it still seems there can be issues with nodes competing for the AP's attention that cannot hear each other. I think the real test would be to have two nodes attempt to stream data while located at opposite ends of the AP's range.

"g" does resolve the issue using RTS/CTS from the AP. "n" has even more sophisticated methods for resolution. Hidden node is a common situation in any wireless networking environment because the nodes have limited transmit power.

In sum, the True Gain offers great coverage and penetration, but does not alter the capabilities of the access point in dealing with hidden nodes, capacity, QoS, authentication or any other classic wireless networking factor.