Using 4 channels rather then 3 for the 2.4ghz wifi
We have a large study room at UC Hastings which accommodates up to 150 students. On average I see about 80-100 users using the wifi in the room. To load balance the wifi in the room I have setup 4 APs. Right now we use the 3 non-overlapping 2.4ghz channels, 1, 6, and 11. The 4 APs are line of sight with each. Do you think it would be a good idea to go to 4 channels instead 3 Ex: (1, 4, 8, 11) Nicholas Urrea Information Technology UC Hastings College of the Law [EMAIL PROTECTED] x4718 ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
Re: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi
It is possible but not recommended. I would turn down the power on the APs so you have less bleeding. Could you stagger the APs so that you only use three channels, but have four APs? Just put the two APs on the same channel at opposite ends and turn down the power. Also I know for a fact that two Cisco APs can handle 100 users, all streaming audio. We have a Spanish exam that we do yearly that does this without any problems. So I would think if you had three that would be more than enough. Justin Dover Harpeth Hall School 615-346-0082 The EDUCAUSE Wireless Issues Constituent Group Listserv WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU on Thursday, February 21, 2008 at 2:30 PM -0600 wrote: On Feb 21, 2008, at 2:03 PM, Urrea, Nick wrote: We have a large study room at UC Hastings which accommodates up to 150 students. On average I see about 80-100 users using the wifi in the room. To load balance the wifi in the room I have setup 4 APs. Right now we use the 3 non-overlapping 2.4ghz channels, 1, 6, and 11. The 4 APs are line of sight with each. Do you think it would be a good idea to go to 4 channels instead 3 Ex: (1, 4, 8, 11) No, if you're using 802.11g. If there's searchable archives for this list, you might be able to find a previous discussion we had on it here. Dale ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
Re: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi
Nick, We have been doing 1-4-7-11 (but 1-4-8-11 makes more sense) since 2000 and even with 802.11g we still like it. The loss that you get from overlapping is largely regained by having a 4th channel. Other sources advise to play with smaller cell and reducing the milliwatts emitted from the AP instead of using 4 channels! CIROND published a paper about the usage of 4 channels as well, (search for CIROND, 4 channels, 802.11b...) warning that though it is acceptable with CCK, it might create problems with OFDM! Philippe -- Philippe Hanset University of Tennessee, Knoxville Office of Information Technology Network Services 108 James D Hoskins Library 1400 Cumberland Ave Knoxville, TN 37996 Tel: 1-865-9746555 -- On Thu, 21 Feb 2008, Urrea, Nick wrote: We have a large study room at UC Hastings which accommodates up to 150 students. On average I see about 80-100 users using the wifi in the room. To load balance the wifi in the room I have setup 4 APs. Right now we use the 3 non-overlapping 2.4ghz channels, 1, 6, and 11. The 4 APs are line of sight with each. Do you think it would be a good idea to go to 4 channels instead 3 Ex: (1, 4, 8, 11) Nicholas Urrea Information Technology UC Hastings College of the Law [EMAIL PROTECTED] x4718 ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
Re: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi
On Feb 21, 2008, at 2:03 PM, Urrea, Nick wrote: We have a large study room at UC Hastings which accommodates up to 150 students. On average I see about 80-100 users using the wifi in the room. To load balance the wifi in the room I have setup 4 APs. Right now we use the 3 non-overlapping 2.4ghz channels, 1, 6, and 11. The 4 APs are line of sight with each. Do you think it would be a good idea to go to 4 channels instead 3 Ex: (1, 4, 8, 11) No, if you're using 802.11g. If there's searchable archives for this list, you might be able to find a previous discussion we had on it here. Dale ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
RE: Re: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi
FYI - this configuration does not conform to the 802.11 specifications. Regards, Jon 303-808-2666 -Original Message- From: Philippe Hanset [mailto:[EMAIL PROTECTED] Sent: Thursday, February 21, 2008 12:43 PM Pacific Standard Time To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU Subject:Re: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi Nick, We have been doing 1-4-7-11 (but 1-4-8-11 makes more sense) since 2000 and even with 802.11g we still like it. The loss that you get from overlapping is largely regained by having a 4th channel. Other sources advise to play with smaller cell and reducing the milliwatts emitted from the AP instead of using 4 channels! CIROND published a paper about the usage of 4 channels as well, (search for CIROND, 4 channels, 802.11b...) warning that though it is acceptable with CCK, it might create problems with OFDM! Philippe -- Philippe Hanset University of Tennessee, Knoxville Office of Information Technology Network Services 108 James D Hoskins Library 1400 Cumberland Ave Knoxville, TN 37996 Tel: 1-865-9746555 -- On Thu, 21 Feb 2008, Urrea, Nick wrote: We have a large study room at UC Hastings which accommodates up to 150 students. On average I see about 80-100 users using the wifi in the room. To load balance the wifi in the room I have setup 4 APs. Right now we use the 3 non-overlapping 2.4ghz channels, 1, 6, and 11. The 4 APs are line of sight with each. Do you think it would be a good idea to go to 4 channels instead 3 Ex: (1, 4, 8, 11) Nicholas Urrea Information Technology UC Hastings College of the Law [EMAIL PROTECTED] x4718 ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
RE: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi
Thanks Everybody for the info. I have already lowered the radios to 5mw OFDM and CCK I’m just trying to make the wifi network as reliable as possible. From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[EMAIL PROTECTED] On Behalf Of Jon Freeman Sent: Thursday, February 21, 2008 1:05 PM To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU Subject: Re: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi FYI - this configuration does not conform to the 802.11 specifications. Regards, Jon 303-808-2666 -Original Message- From: Philippe Hanset [mailto:[EMAIL PROTECTED] Sent: Thursday, February 21, 2008 12:43 PM Pacific Standard Time To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU Subject:Re: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi Nick, We have been doing 1-4-7-11 (but 1-4-8-11 makes more sense) since 2000 and even with 802.11g we still like it. The loss that you get from overlapping is largely regained by having a 4th channel. Other sources advise to play with smaller cell and reducing the milliwatts emitted from the AP instead of using 4 channels! CIROND published a paper about the usage of 4 channels as well, (search for CIROND, 4 channels, 802.11b...) warning that though it is acceptable with CCK, it might create problems with OFDM! Philippe -- Philippe Hanset University of Tennessee, Knoxville Office of Information Technology Network Services 108 James D Hoskins Library 1400 Cumberland Ave Knoxville, TN 37996 Tel: 1-865-9746555 -- On Thu, 21 Feb 2008, Urrea, Nick wrote: We have a large study room at UC Hastings which accommodates up to 150 students. On average I see about 80-100 users using the wifi in the room. To load balance the wifi in the room I have setup 4 APs. Right now we use the 3 non-overlapping 2.4ghz channels, 1, 6, and 11. The 4 APs are line of sight with each. Do you think it would be a good idea to go to 4 channels instead 3 Ex: (1, 4, 8, 11) Nicholas Urrea Information Technology UC Hastings College of the Law [EMAIL PROTECTED] x4718 ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
Re: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi
FYI - this configuration does not conform to the 802.11 specifications. Regards, Jon 303-808-2666 Well, WEP did conform to 802.11 ;-) -Original Message- From: Philippe Hanset [mailto:[EMAIL PROTECTED] Sent: Thursday, February 21, 2008 12:43 PM Pacific Standard Time To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU Subject: Re: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi Nick, We have been doing 1-4-7-11 (but 1-4-8-11 makes more sense) since 2000 and even with 802.11g we still like it. The loss that you get from overlapping is largely regained by having a 4th channel. Other sources advise to play with smaller cell and reducing the milliwatts emitted from the AP instead of using 4 channels! CIROND published a paper about the usage of 4 channels as well, (search for CIROND, 4 channels, 802.11b...) warning that though it is acceptable with CCK, it might create problems with OFDM! Philippe -- Philippe Hanset University of Tennessee, Knoxville Office of Information Technology Network Services 108 James D Hoskins Library 1400 Cumberland Ave Knoxville, TN 37996 Tel: 1-865-9746555 -- On Thu, 21 Feb 2008, Urrea, Nick wrote: We have a large study room at UC Hastings which accommodates up to 150 students. On average I see about 80-100 users using the wifi in the room. To load balance the wifi in the room I have setup 4 APs. Right now we use the 3 non-overlapping 2.4ghz channels, 1, 6, and 11. The 4 APs are line of sight with each. Do you think it would be a good idea to go to 4 channels instead 3 Ex: (1, 4, 8, 11) Nicholas Urrea Information Technology UC Hastings College of the Law [EMAIL PROTECTED] x4718 ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
RE: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi
Hi Nick, I have no problems with four channels for 802.11g, but you have to be careful with it. The benefit of four channels is added throughput gained by 33% more APs being able to talk at the same time. The trade-off is increased errors due to simultaneous transmissions on overlapping channels. The closer together your APs and the denser your client population, the more errors you will get. Turning down the AP power will help, but not much. There will still be 100 client radios blasting away at 20mW. If your room is a typical size for 150 seats, then I think your APs are probably too close together to benefit from four 802.11g channels. I would be surprised if your error rates in such a scenario would be less than 10%, and I would expect even higher. Many things would still work under those conditions, but all the retries would negate most, if not all, of the potential benefit.. Also, error rates that high can foul some stuff up. For example, VPN sessions start dropping unexpectedly at error rates above 5%. Streaming content is also likely to have problems. Now that I advised you against it, I hope you would consider giving it a try. I would love to hear how it works out. If you're available to monitor the network after you make the change, you can always put it right back if things don't work out. Of course it depends on how well your users would tolerate a brief period of degraded performance. Chuck Enfield Sr. Communications Engineer Penn State University Telecommunications Networking Services 110 USB2, UP, PA 16802 Ph. (814) 863-8715 Fx. (814) 865-3988 From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[EMAIL PROTECTED] On Behalf Of Urrea, Nick Sent: Thursday, February 21, 2008 3:04 PM To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU Subject: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi We have a large study room at UC Hastings which accommodates up to 150 students. On average I see about 80-100 users using the wifi in the room. To load balance the wifi in the room I have setup 4 APs. Right now we use the 3 non-overlapping 2.4ghz channels, 1, 6, and 11. The 4 APs are line of sight with each. Do you think it would be a good idea to go to 4 channels instead 3 Ex: (1, 4, 8, 11) Nicholas Urrea Information Technology UC Hastings College of the Law [EMAIL PROTECTED] x4718 ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
RE: [WIRELESS-LAN] Using 4 channels rather than 3 for the 2.4ghz wifi
Here's a few articles on the topic: http://www.extremetech.com/article2/0,3973,708876,00.asp http://yves.maguer.free.fr/WiFi/nombre_de_cannaux_disjoints_4_en_france.pdf It's doable, it's been done, but there's a lot of adjacent channel interference, so you have to be able tolerate some errors and retransmits (which are not ideal for Vo-Fi). Of all the enterprise WLAN vendors, Aruba appears to be the most OK of the practice. Frank From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[EMAIL PROTECTED] On Behalf Of Urrea, Nick Sent: Thursday, February 21, 2008 2:04 PM To: WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU Subject: [WIRELESS-LAN] Using 4 channels rather then 3 for the 2.4ghz wifi We have a large study room at UC Hastings which accommodates up to 150 students. On average I see about 80-100 users using the wifi in the room. To load balance the wifi in the room I have setup 4 APs. Right now we use the 3 non-overlapping 2.4ghz channels, 1, 6, and 11. The 4 APs are line of sight with each. Do you think it would be a good idea to go to 4 channels instead 3 Ex: (1, 4, 8, 11) Nicholas Urrea Information Technology UC Hastings College of the Law [EMAIL PROTECTED] x4718 ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
