Hi all,
We need an 802.11b/g network to serve 50 clients. We have two WAPs, each of which can handle up to about 30 clients. Can somebody comment on the pros and cons of setting them to the same or different channels?
Perhaps pros and cons is the wrong term, more like what functionality is gained and lost with each method.
I am aware that if they are on different channels, the channels need to be well seperated.
Antony
Antony Gelberg hath wroth:
Could you kindly disclose the maker and model of your existing WAP's?
Does it really have a hard limit of 30 users or is that the estimated number of users per access point based on "typical" traffic?
The number of users served are fairly simple to estimate: 100 users doing light surfing and email. 10 corporate or business users. 1 file sharing user.
Yes, I can.
All on one channel with same SSID: Advantages: - Possible seamless roaming if the client support it. - Least amount of interference to neighboring systems. - Minimum user configuration issues. Disadvantages: - Maximum mutual RF interference. Needs physical isolation.
All on one channel with different SSID: Advantages: - Users can intentionally select a specific access point. - Least amount of interference to neighboring systems. Disadvantages: - Seamless roaming is impossible. - Somewhat complex user configuration.
Different channels with same SSID: Advantages: - Seamless roaming is possible with a smart client. - Least amount of mutual interference from your own access points. Disadvantages: - Increased chance of interference from other co-channel users. - Simple user configuration. Clients will scan for SSID.
Different channels with different SSID: Advantages: - Easy troubleshooting and identification of WAPs. Disadvantage: - Users must intentionally select their access point. No roaming. - Most complex configuration for users. - Increased chance of interference from other co-channel users.
You don't have much choice in channels. 1, 6, and 11 are the only non-overlapping channels. If you select a channel in between these, you risk receiving interference from both adjacent channels.
This is worth reading completely:
ftp://download.intel.com/business/bss/infrastructure/wireless/deployment/hotspot.pdf See 5.2.3.1 on channel re-use.
Sure, Netgear WAP102.
I think that this will be the main use case. Netgear pre-sales has just told us that the theoretical (as in defined by the standard, not vendor-specific) maximum per channel is 32 users, and the limit on this AP is more like 15 users in practice. How does that reconcile with your figure of 100?
Is simple user configuration not an advantage? :)
ftp://download.intel.com/business/bss/infrastructure/wireless/deployment/hotspot.pdf
Reading it now.
Antony Gelberg hath wroth:
Hmmm... Looking at the above data sheet, it proclaims: "It supports up to 128 simultaneous wireless clients and client types within the same coverage area." There may be a 30 user limit in the bridge to bridge mode, but not the access point mode.
See above quotation from the data sheet. Netgear pre-sales support is wrong. Actually, I'm not even sure 128 is the real upper limit for simultaneous connections. In a past life (about 7 years ago), I did quite a bit of bench testing to see how many simultaneous users and connections could be handled by various access points. Unfortunately, I didn't test this wireless access point. Many of the units tested would literally roll over and die when faced with too many MAC addresses. It's really a question of how much memory is available for internal tables and what algorithm is used to clear the tables when approaching overflow. Sorry, I'm not at liberty to disclose models and numbers.
I've actually deal with a system that had about 100 simultaneous connections with a T1 backhaul. The assumption is that not everyone is doing something at the same time. That's what I mean by "light surfing" and email. With the proper application of bandwidth management (i.e. QoS) to prevent any one user from hogging all the available bandwidth, it is possible to run with 100 simultaneous users.
However, if it's an office environment, forget it. Office computers are always doing something. The average useage is much higher. Users expect instant response time. My guess is about 10-20 office users per AP maximum.
The one user file sharing is not a joke. Most file sharing applications are designed specifically to maximize thrutput, which means opening up huge number of simultaneous streams. That will hog literally all the bandwidth, all the buffer space available, and flood any cache in between.
Oops. Sorry. It should be listed as an advantage.
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