150+ user wireless network with 300m linear spread

Posted on 2006-10-21
Last Modified: 2013-11-09
I am overseas and have recently adopted a satellite internet system.  I have two distinct issues with the system.

Situation:  The network is intended to support 150 wireless users.  The users are in three distinct areas.(b1, b2, and b3).  b1 is the tallest building and thus supports the satellite.  b2 is 120 meters from b1.  b3 is a group of 4 buildings spaced within a 75 meter square and is approx. 75 meters to its center from b2.

The satellite contract reads 4.0 mbs down/1.0 mbs up with a 2/1 contention ratio.

Currently there are two networks defined NET1 and NET2.

Current hardware is as follows:
At b1:
Satellite and Nera Satlink 1000 - b1
Linksys WTR54GX4 - acting as an access point in b1
Linksys WTR54GS V3 - acting as an access point in b1
Linksys WTR54G V5 -   b1 this router defines NET1
Linksys WAP54G - located in b1 connected to a DLink 10 dBi panel antenna oriented towards b2

At b2:
Linksys WRT54G V2.2 - This router defines NET2 connected to a DLink 10 dBi panel antenna oriented towards b3
Linksys WAP54G - configured as a bridge

At b3:
WAP54G v3.1
WAP54G v3.0
WAP54G v3.0
WAP54G v3.0

1.  Network stability - The network is inherently weak between the bridge.  I believe this issue to be because of limited line of sight to the antenna attached to the bridge and the panel antenna broadcasting from b1.  Additionally we are seeing problems between the second panel antenna and the access points in b3 due to the same issue.

2.  Bandwidth - the contract reads that contention ratio is 2/1.  However, we are not seeing speeds  I believe the issue is that with the current hardware (specifically the routers) we are only able to have 19 concurrent wireless users per router.  This is particularly an issue in the b2 to b3 configuration because we have one router handling over 100 users.

I am a programmer and not a network administrator.  Thus my knowledge is very basic.  Please feel free to ask questions and clarify this issue.  I am looking for someone who has had experience in either developing a wireless solution for 150+ users and/or someone that has experience in developing wireless access over a 300 meter linear spread.

Thank you for your help.

Question by:JackWooten
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LVL 57

Expert Comment

ID: 17786171
--> 2.  Bandwidth

You have wireless routers that support upto 54 mbps (802.11g).  However, this is half duplex and shared between all users connected to that device.  The 54 Mbps includes various wireless protocol over head.  With 19 users you will be lucky to get 1-2 Mbps.  You need to have fewer users per wireless device in order to get faster speeds.

Author Comment

ID: 17786611
Ok, realize that we are taking over what is essentially home use equipment.  Can you suggest commercial grade equipment that meets the base needs of our situation?
LVL 57

Assisted Solution

giltjr earned 200 total points
ID: 17787816
Actually from an bandwidth point of view it does not matter.  Both commercial grade and home grade have the same issues as it is not the quality of the equipment but the 802.11g (a and b have the same issues) standard.

The only thing that commercial grade equipment may resolve would be signal strength  issues, which deals with how far the clients could be from the WAP or the distance between the bridges.

Are the three WAP's that are used to communicate between the sites also used for clients to connect to?

If so, get the clients off of them.  You only want these to be used to connect between the sites only.  This way you get the full 54 Mbps between the site.  

In fact you may want to replace them with any good quality WAP that supports MIMO, which does full duplex wireless.  Any 802.11n WAP should support MIMO and will provide much more bandwidth between the sites.

I personally like Cisco and Linksys (Linksys is "Cisco's home/SMB division").
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Accepted Solution

StonewallJacoby earned 300 total points
ID: 17791511
With your number of users, I agree that you should dedicate AP's to the duty of bridge, even if the AP's are capable of dual function (bridge and AP).  Without seeing your layout, I suspect that the buildings are located such that you would be best served by a bridge between B1 and B2 and a separate bridge between B1 and (one of the buildings of) B3.  Both these bridges should be built with AP's dedicated to the bridging function, and should be equipped on each end with high gain antennas, preferably external ones, carefully and firmly installed.  Metal exterior buildings (like trailers) hurt wireless signal strength.  Once you get the signal into B2, use regular AP's to provide access to users.  B3 is another matter, can you cable between them?  If so, cable an AP in each of the B3 buildings and cable it back to a switch connected to your B3 bridge.

4MB download really isnt much for 150 users.  I am not surprised they are complaining about speed.  2/1 contention ratio sounds wonderful and expensive.  If you have performance doubts, run a test from a single local workstation.  Also note that Cisco recommends no more than 24 users per access point.

Your situation sounds complicated enough that you really should get a qualified network wireless installer to review it and give you a quote.  You are trying to build a commercial network with hobby grade equipment.

In your situation, what would I do if I had to do this myself?  That depends on:
How much money do I have?
How much time do I have?
What are the consequences of downtime when I kill the system to reconfigure?
Are there any local network geeks I can tap for help?
Are there any local RF geeks I can tap for help?

Here are some thoughts:

1.  Test the satellite speed.  Connect only 1 workstation to the sat terminal, and do some speed testing.  If not satisfactory, get the vendor started on fixing it.

2.  If your users can stand it, temporarily kill B3.  Try using the two flat panel antennas and 2 WAP54G's to set up a good bridge between B1 and B2.  Orient the antennas carefully toward each other, both horizontally and vertically.  Connect the B2 end of this bridge to B2's access point(s).  If this improves performance in B2, then set up another bridge between B1 and B3 (if LOS allows) using similar equipment.

This really is quite complicated.

Author Comment

ID: 17793808
I realize this is complicated and I would go to a consultant if one was available.  Unfortunately where I am located I can not rely on local experts for many reasons, availability not be the least of them.

Your suggestion to shut down B3 is actually the way we have gone to this point.  However we are still exploring other options.

Expert Comment

ID: 17795476
I think that using the flat panels on BOTH ends of the bridge to B2 will strengthen the bridge.  120m really is quite a distance; the kind of equipment you are working with was not meant for this.  If you can strengthen the bridge from B1 to B2 and prove to yourself that it works reliably, then you have furnished your users in B1 and B2 with reliable access, and you have proven to yourself you have a solution for B3 that uses mostly what you already have.

Do you need help with IP address assignment or configuration issues?  I think I know what you're up against here, and I want to help if I can.

Author Comment

ID: 17795820
I think we have the configuration issues worked out at this point.  The routers/APs in B1 are all on seperate channels using 192.XXX.XXX.1  The bridge is actually tied into another router that is broadcasting a seperate SSID with IP of 192.XXX.YYY.1.  I don't know if the seperate SSID is even necessary.  This is a holdover from the previous setup.

I am being purposely vague because I cannot disclose location and building layouts.  Sorry if this cause more confusion but it is the limitations of my current situation.


Expert Comment

ID: 17797058
OK, let me know if you need more info.  By the way, I worked in central Illinois back in the 70's with a guy named Wooten.  Ring any bells?


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