Connecting multiple AP’s

[engr1987]

My question may be a basic one as I am relatively new to wireless networking, and until now, have only dealt with a couple of ad hoc networks consisting of a single AP. I have been doing a lot of research and have found only limited information on connecting multiple AP’s in a larger network. What I need to do is provide wireless access in 2 buildings that are adjacent to each other. The main building has a 3Mbs DSL connection. The modem is connected to a router/gateway that provides DHCP service, and the router is connected to a 24 port, layer 2, managed switch. There will be commercial grade AP’s located in both buildings, and there is existing cat5 cable between the buildings. My question is, would it be adequate for AP’s in the second building to be connected to a local unmanaged switch that would then be connected to the layer 2 switch? Could a wireless router be used to function as both the switch and one access point in this situation? The cable run between the 2 switches would be no more than 200 feet. The second building will have 5 AP’s initially with the possibility of adding up to 5 more in the future. The maximum number of concurrent users would be no more than 10 per AP worst case but would more than likely be 3 or 4 normally. If necessary, a second cat5 cable could be available for a second switch if 5 more AP’s were to be installed. The wireless network will be used for Internet access only and must support SNMP, VPN and VLAN capability.

[M/Q]

You are doing great, that is exactly how I would recommend it. Do not use a wireless router/AP, it restricts its ability to be moved if the situation changes as you have 4 other cables running to it. Stick with commercial grade equipment for your AP's and wired switches. AP's wired back to the backbone is the best way to approach this. If you are considering how to manage all these that is also the best way as you can add a enterprise wireless gateway at that point as well and it will feed out to all the AP's.

Your major concern should be that you are using 5 AP's intially and there are only three non-interfering channels on 11b and 11g. You might want to do a site survey and see how you plan to locate the AP's to prevent signal and bandwidth problems from interference. If it is an issue you might want to look at 11a. Please be careful about this part as it has huge implications if not approached correctly.

I have linked one example of the wireless gateway site I was referring to.

http://www.bluesocket.com/

[engr1987]

Thank you very much for your quick response mpkn3rd! I was thinking that using a switch as opposed to a wireless router was the way to go. I just wasn’t sure if the router held any advantages, and I wanted to be sure that the AP’s could be managed okay through the switch and that throughput would not be a problem.

I did look at the Bluesocket wireless gateway yesterday. I will keep it in mind.

The situation with the AP’s is that they will be placed in a hallway ceiling along with sprinkler system water pipes, phone wires, CATV cable, lighting, electrical wiring, and some ducting. I did do a site survey, and the signal propagation was better than I had anticipated. That was done using an 11g AP and 11g wireless card. 11g is required, so using 11a is not an option. There are 3 floors in the second building. With the test AP placed in various locations in the 2nd floor hallway ceiling, I tested the signal on all 3 floors. It is a hotel, so each floor has an identical layout with the hallway running down the middle , and testing was done throughout quite a few rooms on all 3 floors. I am expecting that with load the 2nd and 3rd floors will be fine, but I am anticipating the possibility of having to add the additional 5 AP’s on the 1st floor. I am aware of the limitation of there being only 3 non-interfering channels on 11b & g. It appears to be a bit of a juggling act between getting adequate coverage and channel separation issues. At this point, I am planning on the distance between the AP’s to be approximately 40 feet but that could easily be increased if necessary. I have only had the one AP to test with at this point. I won’t be able to do further testing until I am able to get a few more. Due to certain considerations and some decisions that still need to be made, I am unable to purchase more right away.

Thanks again!

[M/Q]

Sounds great again, just be careful about the interference. Also if they are going to be placed in the ceiling they need to be plenum rated. You may know that all ready, if so I apologize.

As for your plan I like it very much. I am a firm believer of KISS and using devices that are single function as they do that specific job well.

[engr1987]

Yes, definitely plenum rated. I agree simple is best. Helps to keep the headaches down.

I am interested in hearing of anyone's experiences with installing AP's in a similar environment. I am curious as to how well their chosen AP's worked and how good the signal propagation was. Taking into consideration that every situation is different and unique, it would still be interesting to me to hear about some experiences, good and bad.

Thanks!

[JJDinsay]

I too will be installing in a hotel in a similar manner but the client I'm working on will be a 27 storey building! Yikes - with a wired solution it's much easier. DSL modem down low connected to a manged core switch dat supports fiber. I will run CAT5 to da lobby for a public hotspot in the lobby and then run CAT5 up to a remote switch in the comms closet on the 3rd floor. From that switch I run a CAT5 to an 2 AP's each on the 2nd floor, 3rd floor and 4th floor. The building layout is the same - a square design with the rooms along the hallways - both hallways seperated by an elevator shaft. Then on the 6th floor I install another remote swith and run a CAT5 to it from the main switch on floor 1. From there same design again - run CAT5 to 2 AP's each on floor 5, 6 and 7. Next is to install a remote switch on floor 9 and connect it using fiber to overcome distance issues and then connect each of the APs to the remote switch using CAT5. I will use fiber to connect all the remote switches every 3 floors up (11, 14, 16, 18, etc . . .) I've done an RF survey I can't get away with one AP per floor due to the elevator shafts seperating the rooms. I plan on placing each AP in an alternating patter 2 provide overlapping coverage. I'm worried about the channels though. All I need to make sure is that each set of AP's that cover one set of floors - let's say floor 2, 3, 4 is using a different channel than the AP's on 5, 6, 7? Here's a rudimentary setup of AP's if U look at building from the side. The Cat5 solves my connection solution for short range runs from remote switch to AP's and fiber resolves long runs like remote switch to main switch. DHCP will be served by a Win2K and will serve RADIUS. I may go with NoCat solution for Linux for my authentication instead and SQUID to for my caching services. It's only an original plan - U guys have any suggestions?


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I figure this is the best arrangement for the solution as it reduces cost - no need to run a switch per floor and it doesn't require a drop for each room. The hybrid LAN will be used mostly for Internet access so 54MBps limitation should be enough. Unfortunately I'm in Thailand so DSL technology is not as good and it's crazy expensive. 512/256 will support my users - might go with 2 seperate lines as well. It's a serviced apartment so usage may vary as well. I would appreciate any feedback.