Integrating wireless with wired Gig-E on ships

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Jan 3rd, 2008
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In the context of a LAN with 2260 users on one ship, we are looking to develop a 25% solution using wireless. This works out to roughly 565 wireless drops. Besides the obvious steel bulkhead hurdles, we have to deal with where on the ship to put the AP's. This will require an RF study, but before that, Qestion 1: how many users can be "assigned" to one AP?

Wired drops are 100M to the desktop, so wireless users are also expecting 100M at their workstations. Wired products already in place are: Alcatel backbones and Edge devices.

Question 2: Are there standard configurations that we can model?

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Overall Rating: 5 (2 ratings)
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Richard Atkin Fri, 01/04/2008 - 01:18
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Hi Kevin,


There's no real limit that I'm aware of in terms of users per AP (256 rings a bell?), but in reality if you're just using it for e-mails and light internet browsing, then you don't want more than ~25 users per radio (it varies massively, it depends what you're using it for, and what your users expectations are).


You can't expect any more than about 18Mbps half duplex through a single radio, even if your clients are all running at "54Mbps".


You should probably chose dual radio APs, as this gives you the ability to use 802.11 A & B/G, giving you two radios per AP, and doubling the amount of available bandwidth by comparison to a G-only or A-only solution.


While we're talking trechnology, you may want to consider the 1251, which can use 802.11N Draft 2. While there's no guarantee that 802.11N Draft 2 will be upgradeable to 802.11N Final, Cisco 'have done their best' to future-proof the product. Worst case if that you have to buy new 802.11N moduules. 802.11N offers increased cell sizes and much higher throughput. 802.11N is also backwards compatible with 802.11A/B/G, and apparently an A/B/G client on an N Access Point will still benefit (slightly better throughput and range) from the clever maths associated with an 802.11N AP.


HTH,


Any problems, you know where we are!


Richard.

rose-kevin Fri, 01/04/2008 - 05:08
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Richard, Thank you for the response; greatly appreciated. I am wondering why some wireless architects (Navy) are only suggesting 3 users per AP? Seems like a gross waste of bandwidth. These users will be generally surfing the net, emailing (with the occaisional picture download). The issue will be distance away from the AP. Drops will be all over the ship. Using 50 feet as the rule of thumb suggested in the 1250 AP video clip we will have range to the AP will be an issue. We're likely looking at 65-70 AP's for 500 users. What other pieces of gear will be required in order to talk back to the legacy backbones/edge devices (at Gig-E speed), including Intrusion detection, security, management software, etc... We have a first look configuration, but if you can point me to a configuration page on your website, that would be very beneficial.

pmccubbin Fri, 01/04/2008 - 07:55
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Hi Richard,


Good response. I rate it a "5" and hope you continue contributing to this forum.


A couple of speculative questions about the 802.11N.


1. The APs which will eventually run 802.11N will require a greater PoE than the current ones, correct? This might necessitate an upgrade of the switch providing the power?


2. Also, do you think the controllers themselves will be able to handle the greater capacity projected by 802.11 N or will they need to be upgraded too?


Best,


Paul

scottmac Fri, 01/04/2008 - 07:58
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A typical rule -of-thumb is ~20 users per AP, given common productivity applications and utilizations.


That being said, there is no typical utilization. Every organization is different, some individual organizations are different on a day-to-day basis ... "common" as a word should be banned in the planning of AP deployments, IMO ;-} )


What I believe you'll find helpful would be a bandwidth study for several users and extrapolate from there. With perfect connections (yeah, right) remember that a 54M band is really only passing ~22Mbps worth of data ... subtract from that for multipath, collision, polling, and knock off a big chunk (~20%) if there's an 802.11b device ... ONE DEVICE ... associated to that AP.


User distribution will be very important as well ... if the users are well distributed that would make things ultimately easier, but more expensive (less utilization per compartment, more APs because of the geographical distribution).


It may also be worthy of your consideration to look at 802.11a, at least in parallel, wherever possible, because it has more non-overlapping channels and is less likely to catch interference. The other benefit is that it bounces like a mother and on the inside of a tin can, your coverage areas will have few shadows.


Also, depending on your user and AP distribution, you may want to look at something like RADIAX (Andrew Corp, http://www.andrew.com)... which is essentially an engineered leaky coax used as a wide area, low power antenna. It's frequently used in hospitals for low-power paging.


I'm sure you've got this covered, but just in case ... You'll want to verify your configurations against the local laws & regulations of anywhere the ships are likely to cruise (if passing through international boundaries).


Question #2: I'd be surprised, there are just too may variables for any kind of standard or template.


Good Luck, Happy New Year!


Scott


rose-kevin Fri, 01/04/2008 - 08:30
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Scott, Thanks to you for the response. Good stuff in there. I don't know if you've seen of the military's preliminary white papers on deploying wireless on ships, but if you can get your hands on them, they might give you some insight into what we're trying to accomplish and your Gov't reps a leg up on how to make it work. I would love to send you some of that paper work, but alas, I am bound by FOUO (For Official Use Only) protocols that prohibit me from providing to you. You may be able to Google something. Again, we'll take some of this info back to the drawing board and chew on it. -Kevin

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