CTS-toSelf vs. DSSS-OFDM
Last Post: October 20, 2011:
Thanks Devinator and GT Hill,
What I understand.
802.11b wifi phones even on a seperate VLAN are dangerous to the 2.4 spectrum of b/g APs.
You can still do it but it doesn't guarantee your data network throughput will be optimum especially if you have alot of users.
This helps tremendously, I saw a recipe for disaster coming and you both have help validate assumptions I had that were partly right and wrong at the same time.
I am learning and this CWNP program is PRIME!
WiMAX is a service provider technology, not a wireless extension of the LAN. They are two entirely different things with different applications.
They get mixed up because people are pushing Mesh Wi-Fi for service provider-style municipal Wi-Fi networks. It may work out O.K. to take Wi-Fi off the LAN and make it a way to give Last Mile access to the internet, but WiMAX is too reliant on licensed RF spectrum to be an extension of the LAN.
For now, the best idea is to take everything except VoIP off the 2.4 GHz (b/g) network and use 802.11b VoIP phones. There are no 802.11a phones out there because of mobile device limitations. Use 5 GHz (802.11a) for data as much as possible.
Meru (www.merunetworks.com) has an interesting option for handling Voice and Data on one WLAN. Their APs share one BSSID (MAC Address) and the same channel. That means clients see the entire wireless medium as just one massive AP. Therefore, the clients never have to roam. The only potential problem is that this relies heavily on the software in Meru's controllers. It has to accurately determine which AP should handle traffic for each client. I've heard from folks who have used it that it works a lot of the time, but it has a hard time in areas with lots of interference and obstructions.
As far as the original topic of DSSS-OFDM vs. CTS-to-Self protection, it's impossible to say which would be best without seeing both in action. It might just be a matter of companies not wanting to spend the additional money to incorporate technology which will give a minimal potential performance benefit to the product (with zero financial benefit).
One thing I have noticed is that with most vendors there is no way to avoid the 25% to 40% performance drop (don't believe the hype on larger numbers) you get with Protection. Even in g-only mode, most products still enable Protection if a Protection-enabled AP is nearby and on an overlapping channel. I only have experience with APs from 8 vendors, but only Cisco allowed Protection to be disabled in that scenario.
Thanks Ben Miller.
I believe WiMAX will soon go mobile with 802.16e and provide us bandwith in some of the unlicensed spectrum in time. You are right it is mostly licensed and that is a good and bad thing for us bandwidth seekers. Right now vendors like Airspan and Alvarion are leading the way with pre-Wimax mobile devices. Airspan has a hybrid Wifi 802.11 and WiMax device that sits on the desktop that shows promise.
I read Meru's whitepaper on ATC and how they implement to enhance-control the RF environment and the challenges with voice over wireless today. Quite interesting. Don't know if it is a good thing or bad thing to be locked to just one proprietary vendors AP and controller. But you have to start somewhere.
Keeping the workforce and world mobile and wireless is a full time job. We are only pioneering a change that will lead us to places where no man has gone before!
Again, remember that 802.16e is a service provider technology, not a wireless extension of *your* LAN. What these vendors talk about is a metro area base station that would blast wireless into the home for a Last Mile link to the internet. That is quite different from Wi-Fi, where anyone can own their own wireless data network.
Like everyone else, I am interested to see what happens with 802.16e. Don't confuse yourself, though. Wi-Fi is a totally different technology than mobile WiMax. Wi-Fi is for everyone while WiMax is going to be owned by only the service providers (cable companies, phone companies, etc.).
And by the way, the guys who wrote that Network World article you posted the link to are completely clueless. It's a shame that misinformation like that gets presented to the general public.
Things seem to have died down on this thread so I thought now would be a good time to say I appreciate the discussion. I seem to pick up nuggets of good information everytime I get on here.
Devinator, I have tried to open the Ripple paper but I keep getting an error "the viewer cannot decrypt this document". I have tried using Adobe Acrobat Reader 5.0.5 and Adobe Acrobat 5.0.5. Have you seen this before and do you have any suggestions on how to fix or work around? Thanks.
Opening any of my whitepapers requires Acrobat Reader version 7 (free download from adobe.com)
Understanding the capacity issues with VoWLAN and steering course away from the voice 802.11b environment and the mixture of 802.11g data , might I inquire on the following?
Which vendor has the upper hand on the development of the OFDM PHY (5GHz) 802.11a handset? Cisco?
That is my assumption. With Cisco's Airespace aquistion I would think that the LWAPP be utilized extensively with the 802.11a phones and provide a counter to MERU very soon.
In my travels many are touting the MERU way of VoWLAN. Is it really working well? I see that MERU and JUNIPER are out in green pastures as well as mesh vendor Firetide.
Competition is tough and Cisco has some hungry competitors. I think that is a good thing. It keeps you on your toes.
Of course we are here all VENDOR NEUTRAL :)
As far as VoWLAN infrastructure, my personal feelings are that Meru's way of handling session handoffs is better than anyone else at the moment. I know that Colubris, Aruba, Airespace, and Trapeze all pay very close attenion to QoS for VoWLAN, so it's hard to tell really who's best w/o some independent laboratory testing. The last testing I read was at least a year ago, and *I think* Aruba came out on top. I think all of these vendors will soon, if not already, have very good VoWLAN QoS features. I'm looking forward to 802.11e ratification.
As far as 802.11a VoWLAN handsets, I don't know who's on top, but I know it isn't Cisco since they don't make one yet. :-)
I was told by one guy who supports handhelds in a warehouse that Meru was disappointing when faced with obstructions. In a clear space, they are great, but when going from room to room, the clients dropped a lot. Obviously this is purely anecdotal information.
Don't hold your breath for 802.11a VoIP phones. You are talking about putting a very energy consuming wireless technology in a small device that must deal with battery life and heat problems. It may happen at some point, but now that the major chip manufacturers are finally ditching the 802.11n Task Group to work away from Airgo, hopefully a higher speed standard will be out soon and VoIP will be done there.
One last thing about WiMAX vs. Wi-Fi is that I found some nice writing from Motorola about 802.16e WiMAX. Now, keep in mind that this is a research paper from Motorola's side of the 802.16e vs. Qualcomm side of the mobile wireless internet access battle. It does, however, detail some specs of 802.16e and gives some context for it that is sorely lacking from those clowns that wrote the article for Network World.
I see how any vendors VoWLAN solution is suspect to loss with voice especially after the site survey we did last week in a building that is made of concrete ,steel, glass and more concrete, steel and glass.
That MOTOROLA WiMAX whitepaper is on time. I understand more clearly. I see 802.16e as the catapult for the WiMAx and Motorola acknowledges the fit. We need to keep our eyes on that and UWB.
now that the major chip manufacturers are finally ditching the 802.11n Task Group to work away from Airgo, hopefully a higher speed standard will be out soon and VoIP will be done there.
? What is going on in the 802.11n (airgo) space war now? Faster Speeds ?
Beam me up!