So how does it get around this problem in Extricom and Meru systems?
So how does it get around this problem in Extricom and Meru systems?
Meru has the benefit of having been designed relatively recently in 2002. In 2002, wireless was already relatively prevalent. The challenges microcell wireless face, and still face, are the issues of access points interfering wiith each other, the associated issues of channel planning, clients on access points contending with each other creating bandwidth reduction (that's why other solutions cant get laptops online quickly at the start of a lesson), and issues of roaming. Clients in a microcell environment very often hang on to access points even when there is one with a better signal strength to associate to. In microcell environments clients control association. With Meru, the infrastructure controls association, the clients only ever "see" one access point and therefore the decision to roam is removed.
With patented technology ensure both upstream and downstream Qos
Just thought i'll pass on our experince of the above product (in a 4 site FE environment).
The product seems pretty reliable and is great for deploying a wireless network with a global config (same SSID and Key across all 4 sites; several WAPs per site). You can set the config once on the master controller and have the config replicate to the salve controller and they send their config to the WAPs. You can also have multiple SSID/configs going in parallel (including WPA, WPA and 802.11X).
The product gets pretty good reviews and seems to be "feature packed". We have barely delved beneith the surface. But one downside that the features do seem incredibly complex to configure and the online manual is very big. One problem we have at one of the site is lack of IP addresses available in our class C private range, so we'd like the controller to provide IP addresses to the laptops in another range and route between them and the rest of the network, but working out how to do this has been a challenge. I you needs a CCNP or something to figure it out. Does anyone know how it's done?
They all need 5mbps of bandwidth each to run an e-learning application/vod let's say..or at the start of the day to load a profile which is common in education..
How does a single cell (sharing bandwidth of a single channel) from produce over 1gbps of bandwidth in the same room at the same time?
The common problem of microcell architectures is that to increase bandwidth availablilty in a given area, more access points have to be used. Therefore, inherent in microcell is that there would then be more access points on the same channel in a given area which creates more cochannel interference, more client decisions as to which access point to talk to have to be made, creating more issues of "sticky client" where clients hang on to the "wrong" access point, even when they have roamed towards an AP which a better signal strength. Both these issues create bandwidth loss and lower speeds for connecting clients. Notwithstanding the contention issues that microcell faces, where collisions over the air necessitate clients back off, retry, back off etc, causing time delays and bandwidth loss.
In a microcell environment not only would you get interference in the very room you are working in, but then what channel would you put in the next door room as you'd almost certainly have an AP on the same channel bordering the next door room.
The scenario you describe is not new to Meru. Thanks to the fact that Meru can handle up to 128 clients per radio, with little or no contention loss thanks to the patented RF algortithms (called Air Traffic Control), the Aps can listen and coordinate communications across adjacent APs in range.
It's a bit like the difference between having a teacher (the controller and APs) deciding which of the children can speak at any one time rather than having them all speak at once creating noise. The Meru infrastructure coordinates and controls communications at the very edge of the network in the APs to create true Qos where it is needed.
Meru achieves this on a microsecond to microsecond basis. A good example of a high density deployment can be seen here Meru Networks | CME Group . There are numerous other examples worldwide.
With regard to bandwidth, Meru can layer "virtual cells". In the 2.4 Ghz spectrum you can treble your available bandwidth in any given area, again contention free, with none of the interference problems of what channel you use in the next door room as you can just extend your virtual cell on one of the channels. With more channels available in the 5Ghz spectrum, this layering can be extended further. With 11n, obviously the bandwidth gains by channel layering are even greater.
Meru's architecture has been developed with the benefit of understanding the challenges that wifi faced, and then designing a product to fix those issues. Wifi expanded quickly from consumer based devices designed to handle few clients, where only one access point would be used.
No issues of channel interference, no contention issues (which is what usually cripples a school classroom trying to log 30 machines on at the same time), and the seamless roaming with no issues of sticky clients.
I have that exact setup on my Aruba 800 controller. What you need to do is setup another vlan on the controller with the built in DHCP server on the controller and then set up a trucked VLAN port between the controller and some sort of routing device. The routing device could be a cisco router to a good hp switch all it needs to support is 802.11q and static routing (you may whant ACL support for extra security between your networks but thatís up to you).
PM me if you want some more info
Nick (Sheldon School)
So...how does 'channel layering' and 'virtual layers' differ from using different channels then?
Having used the ruckus gear in a whole school scenario I'd have to say I've not seen any of the issues you describe.
I'd also say the auto focusing/shaping antennas are much more useful as a piece of hardware then any software innovations I've seen - the most hilarious test was at bett, where the single ruckus AP was pushing a signal all the way across the main hall while fighting approx 200 other wireless networks.
john (15th March 2009)
I will reply to a number of recent posts.
Single channel operates by coordinating communications between access points operating on the same frequency, something microcell architectures have to plan around, as their architecture grew out of home based wireless systems where one access point would normally cover an average sized house.
As wireless became more popular, and spread to enterprises and schools, the limitations of microcell architectures have become all too apparent (access points interfering on the same channel, inability to handle high volumes of clients, hand offs during roaming) and complicated mechanisms for avoiding all of these inherent issues have had to be designed by microcell vendors.
Understanding these fundamental issues of microcell was key to Meru's design.
A single channel (by design far easier to deploy and extend upon), allied to Meru's patented RF algorithms, ensure that contention over the air is eliminated ensuring all devices, up to a maximum of 128 clients per radio (and that is just a hard stop as clearly 128 are sharing the available bandwidth.)
In no way does Meru recommend 128 clients per radio, due to the fact they are sharing the available bandwidth, but the key thing is that the clients are sharing ALL of the available bandwidth, not a FRACTION of the available bandwidth as we see in competing systems. In competing systems the more clients added the more unusable they become. Regularly we see classrooms of laptops come to a standstill even with recent technology.
It's a bit like a teacher coordinating which child can speak and get their message through whilst every one else in the class listens, rather than the teacher allowing all the children to shout at once when NOONE gets their message through. It is far more efficient.
Technically, this is because Meru's coordination mechanisms deliver QoS at the very edge of the network (at the AP) over the air, ensuring contention is eliminated.
"Virtual Cell" is a mechanism for ensuring seamless roaming for all clients. The Meru infrastructure controls which access points talk to clients, not the other way around (clients controlling association) Clients can be very unpredictable and "flip flop" between cells (on different channels) and therefore disassociate and reassociate. Or, clients when roaming round a building, can hang on to an access point to a point where they have limited connectivity which slows all other clients down not only on that access point, but quite possibly access points on the same channel elswhere in the vicinity.
Meru removes these issues.
Channel Layering allows customers to increase available bandwidth in a particular area, perhaps where higher bandwidth applications are taking place. Microcell vendors would "pack" more aps into a given area. However this denser environment increases the propensity for access points on the same channel to interfere with each other as there are more access points on the same channel in a given area.
Meru, having been designed specifically to operate on a single channel, simply doesn't have this issue.
Meru doesn't have to be operated on a single channel. You can actually deploy Meru in a traditional microcell way if you really wanted to. The recommendation would not be to do so.
One only needs to view the video here to see the power of what Meru does. Meru Networks | CME Group
Apply this principle to a classroom of laptops and it is easy to see why Meru is growing in popularity in the education space as one of the key issue facing schools/colleges/fe/he is will I be able to cope with logging on lots of devices, and will the wireless even work at these numbers of devices. Meru cannot "invent" bandwidth, but Meru certainly don't lose any due to contention as lots of devices connect.
Our website is an excellent source of technical information and case studies for all to view.
Last edited by Jaco45er; 5th December 2009 at 02:54 PM.
i hope this might help, we work wirh Rm from time to time - specifically on green sites - where we help put in Meru - the reason we are used is this work is outsourced to us due to RM not able to get new technology signed off internlly without a massive struggle.
drop me a quick mail, i am able to arrange some demo kit for you if this would help you.
My name is Ben Wilson and I am the UK Country Manager for Xirrus. We've just started to sponsor this networks forum and have a thread introducing ourselves and our product.
We have many hundreds of education sites across the UK and many thousands across the world using our high performance WiFi Arrays. We are the only wireless vendor to off a Free Real Life Active Site Survey and a 100% Coverage Guarantee. We work with nearly all the main education partners in the UK and outperform all other wireless equipment in terms of coverage and capacity on a per devices basis. If you would like to know more, I would be more than happy to discuss detail and competitive landscape with you.
I work in a large 3 form entry 1950's built thick solid concrete walls primary school. When I first came here we had lots of wireless problems. As I have a background as a radio engineer I found it interesting challange to takle the problems so If anyone is interested I can offer this advice that worked for me as now everything is now working well.
I did get quotes from companies to sort the problems out but thought there price was far too high. So I did it myself on the cheap. Firstly I had my friendly local cabling guy put cable access points in everywhere we can. We did not use wireless where we dont have to. You cant beat a cable! I am sure you know this.
Secondly we are in a residential area so lots of co channel interference especially nowadays when I think BT routers must put out 2 signals one for the users an the other is BTfon or a Btopenzone that no one probably uses what a waste of channels.
We now cover the school with just 5 access points but I did do away with the temramental laptop trollies. So wireless is used just for a few teacher and Teaching Assistent laptops and supplying connectivity to 6 mobile classrooms each with 2 clients in. I used Netgear access points and NEW link uSB High gain wireless adapters on the clients. For clents in poor reception area I used High Gain Omni-Directional Swivel Wireless Antenna from Maplin and especially good is the Compact High Gain Directional Corner Antenna for Wireless Networks at £19.99.
I have found that the position of the access point is critical don't settle prematurely on a location for the wireless access point or router. Experiment; try placing the device in several different promising locations. While trial-and-error may not be the most scientific way to find a good spot for your equipment, it is often the only practical way to assure the best possible Wi-Fi performance. Microwaves behave very strangely sometimes.
Also you can buy from CPC Farnell an Antenna extention cable so if you can move the access point antennas around say close to a window or away from a concrete wall all this helps but of course you have to have time to experiment. As always lots of money can be saved if you have time.
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