Two Networks on Same Frequency
Last Post: March 23, 2006:
I have three access point wireless network on the 2.4GHz frequency in a one storey building 350 ft long by 120 feet wide. Everything is fine, but I have a group of 50 people coming in for 3 days and they need a separate wireless network going to the Internet. My first thought was to have them set up on the5Ghz frequency but that is not possible because of equipment restraints. How can I have them co-locate on the 2.4 GHz frequency without interference? I can adjust the power on the access point in the area where they will be located, but I am afraid that my people might get dropped; any ideas?
Use channels 1, 6, and 11.
I am currently using channels 1, 6, and 11 on the existing nework which has three access points.
With 50 extra users presumably all on the Internet, you are going to want them on more than one AP. 50 users is a high number for one AP. At a minimum, you are going to want them to use at least two different AP's.
Here are a few options. It would be helpful to have some more information before making more suggestions.
First. If you have the right AP's and switches, you can set up a second Guest SSID and send the users directly to the Internet by way of a VLAN Tag. If this is an option, the second question would be, what is the user load on the current AP's?
Assuming you can't do that or your current AP's are maxed out, you will need to add at least two extra AP's in the same area. Your concern is how do you have 5 AP's but only 3 non-overlapping channels and still provide good service? First, don't use anything except channels 1,6, and 11. If you need more of a reason for that, look at the thread between myself and Criss Hyde on the subject.
You are going to want to lower the power levels on the extra AP's to only service the extra customers. You will put them on different channels, but invariably they may be on the same channels as your current AP's.
I would like to hear your feedback on this line of thinking. That may help work on your situation a bit. Good luck!
Oh, one more thought. Will all visitors have g capable cards? If so, this will help. Get AP's where you can disable "b" clients. Depending on the brand of AP you can disable "b" data rates, which can be advantageous. Let us know.
GTHill, you hit the nail on the head. ?¡é?€??How do I have 5 APs on 3 non-overlapping channels and still provide good service? I do appreciate your input. I am currently using Cisco 1231AG access points and have them all on a VLAN. The user load on the current SSID is approximately 30 so I do not have a lot to play with there, I am maxed out. I do not want this temporary group on any of my access points so they will have to install their own APs.
I am inclined to force them to use the Cisco 1231AG and have them configure for the B radio only, and change my existing configuration to G only. All my existing clients have the ABG radio options, so confining them to G temporarily should not be a problem, but both networks will be sharing the 2.4GHz frequency.
Here is a brief outline of my current network. The building is 350 feet long and 120 ft wide. On the eastern end is AP1 on channel 1, in the middle is AP2 on channel 6, on the western end is AP3 on channel 11. The temporary people are going to be in the middle keeping company with my AP2 on channel 6.
You are right GTHill, I will have to lower the power level on the guest network APs but might have to do likewise on my existing APs, and then I am concerned about the level of service on both networks. The guest network people do not have A radio.
On the other hand, some days my user load is really low and I might be able to accommodate the 50 additional users, so I am open to the other option of setting up a second SSID and send them out to the Internet. Can you give me some more input on this?
Thanks a lot.
You say that you currently have 30 users on the current SSID. Does that mean that you have 30 users spread out over the 3 AP?¡é?€??s, or 30 users per AP? How many users per SSID doesn?¡é?€??t really matter, its how many users are on each AP / Channel.
Hey, if all of your clients have A radios built in, why not make your current network 11a only and the guests on the b/g side. Then, change the channel of the g interface of AP2 to channel 1, then add another AP in that area at channel 11. Whenever I have the option, I always put two AP?¡é?€??s in the same area as far apart as possible, channel wise. You may be worried that 11a won?¡é?€??t go as far as b/g, but test it first. You may be surprised. 11a doesn?¡é?€??t always have shorter range.
If for some reason you don?¡é?€??t want to have your current clients on 11a, then I don?¡é?€??t recommend setting all of the guest user AP?¡é?€??s to 11b only. 11b and 11g use the exact same channel sets, so this doesn?¡é?€??t do you any good. Actually, it will most likely hurt the performance. When an 11g mixed mode AP senses an 11b client or AP in the area, it will go into protection mode, which in helps avoid collisions. The short explanation is that 11b clients cannot hear when an AP is transmitting at 11g speeds, so it will step on the 11g communications causing a boatload of collisions. In mixed mode, which is what you want in this case, the AP will transmit a CTS frame (in DSSS 11b), which tells the 11b clients to shut up while I talk for X amount of time (duration in microseconds).
When are you going to be setting this up? Your best option, given the information that I have, is to enable the 11a radio with the same SSID as your current network. Then, change the SSID on the 11g radios to whatever you want to call your guest network. For additional security, assign different VLAN tags to each interface, and port the guest side directly to the Internet. Add another AP in the area of the guest clients and give the 11g radio the guest SSID.
Let me know what you think about all this. If the discussion gets too much more complicated, it may be easier and faster if we just talk. For sake of the forum, I will post the results of your implantation so we can all learn from it. If you want to talk, let me know and I?¡é?€??ll message you with my number.
"Here is a brief outline of my current network. The building is 350 feet long and 120 ft wide. On the eastern end is AP1 on channel 1, in the middle is AP2 on channel 6, on the western end is AP3 on channel 11. The temporary people are going to be in the middle keeping company with my AP2 on channel 6."
How about adding 2 more APs at each end for a total of 5 APs being used. Place AP1 close to one side of the 120 ft wide interior and AP4 100 ft - 120 ft on the other side of AP1. Do the same with AP3 and AP5 ~350 ft from AP1 and AP4.
Keep AP2 in the middle (center it) and change the channel to 11.
Make (AP1 and AP3) channel 1 and (AP4 and AP5)channel 6.
So you would have channel 1 and channel 6 (AP1 and AP4) on one side of the building and channel 11 in the center and ~350 ft on the other side of the building you would have channel 1 and channel 6 (AP3 and AP5).
That way you can run all the APs within the same RF range but on different channels to prevent interference. Your guests can then use channel 11 for their use since they will be located in the middle. The other folks can use channels 1 and 6.
You will have to determine the optimum distance and power for the APs in this scenario.
Test it and see if that will work. Good luck!
Or, with 4 APS, you could use 2 APs in the center (one on each side ~120 ft apart) using channels 6 and 11.
The other 2 APs would be placed at each end ~350 ft apart and use channel 1 for both APs.
This way you will have 2 APs in the middle of the building accomodating 50 guest users on channel 6 and channel 11. Each end of the 350 ft building will both be using channel 1.
With this scenario, there should't be any channel interference.
Hey, this is fun being creative with APs.
Waverunner, I am feeding off your idea, and think I will might be able to do it with 4 APs.
GTHill, please send me your number, I would like to run some ideas by you.
Thanks you guys, I really appreciate your input.
Good luck! Let us know what temporary arrangement worked for your situation.